webrtc-stats.html

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      Identifiers for WebRTC's Statistics API
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    <section id="abstract">
      <p>
        This document defines a set of WebIDL objects that allow access to the statistical
        information about a {{RTCPeerConnection}}.
      </p>
      <p>
        These objects are returned from the getStats API that is specified in [[WEBRTC]].
      </p>
    </section>
    <section id="sotd">
      <!-- Status of the draft -->
      <p>Since the previous publication as a Candidate Recommendation, the stats objects were significantly reorganized to better match the underlying data sources. In addition, the <code>networkType</code> property was deprecated for preserving privacy, and the <code>statsended</code> event was removed as no longer needed.</p>
    </section><!-- NB: [[!..]] normative refs, [[..]] informative refs-->
    <!-- based on the wiki page https://www.w3.org/2011/04/webrtc/wiki/Stats -->
    <section class="informative">
      <h2>
        Introduction
      </h2>
      <p>
        Audio, video, or data packets transmitted over a peer-connection can be lost, and
        experience varying amounts of network delay. A web application implementing WebRTC expects
        to monitor the performance of the underlying network and media pipeline.
      </p>
      <p>
        This document defines the statistic identifiers used by the web application to extract
        metrics from the user agent.
      </p>
    </section>
    <section id="conformance">
      <p>
        This specification defines the conformance criteria that applies to a single product: the
        <em>user agent</em>.
      </p>
      <p>
        Implementations that use ECMAScript to implement the objects defined in this specification
        MUST implement them in a manner consistent with the
        ECMAScript Bindings defined in the Web IDL specification [[WEBIDL]], as this document uses
        that specification and terminology.
      </p>
      <p>
        This specification does not define what objects a conforming implementation should
        generate. Specifications that refer to this specification have the need to specify
        conformance. They should put in their document text like this (EXAMPLE ONLY):
      </p>
      <ul>
        <li>An implementation MUST support generating statistics for the type
        {{RTCInboundRtpStreamStats}}, with members {{RTCReceivedRtpStreamStats/packetsReceived}}, {{RTCInboundRtpStreamStats/bytesReceived}}, {{RTCReceivedRtpStreamStats/packetsLost}}, and
        {{RTCReceivedRtpStreamStats/jitter}}.
        </li>
        <li>It MUST support generating statistics for the type {{RTCOutboundRtpStreamStats}}, with
        members {{RTCSentRtpStreamStats/packetsSent}}, {{RTCSentRtpStreamStats/bytesSent}}.
        </li>
        <li>For all subclasses of {{RTCRtpStreamStats}}, it MUST include {{RTCRtpStreamStats/ssrc}} and {{RTCRtpStreamStats/kind}}. When stats
        exist for both sides of a connection, in the form of an {{RTCStatsType/"inbound-rtp"}} / {{RTCStatsType/"remote-outbound-rtp"}}
        pair or an {{RTCStatsType/"outbound-rtp"}} / {{RTCStatsType/"remote-inbound-rtp"}} pair, the members {{RTCOutboundRtpStreamStats/remoteId}} and {{RTCRemoteOutboundRtpStreamStats/localId}} MUST
        also be present.
        </li>
        <li>It MAY support generating other stats.
        </li>
      </ul>
    </section>
    <section>
      <h2>
        Terminology
      </h2>
      <p>
        The terms {{RTCPeerConnection}}, {{RTCDataChannel}},
        {{RTCDtlsTransport}}, {{RTCDtlsTransportState}}, {{RTCIceTransport}},
        {{RTCIceRole}}, {{RTCIceTransportState}}, {{RTCDataChannelState}},
        {{RTCIceCandidateType}},  {{RTCStats}}, {{RTCCertificate}} are defined in [[!WEBRTC]].
      </p>
      <p><dfn class=fixme data-idl>RTCPriorityType</dfn> is defined in [[WEBRTC-PRIORITY]].</p>
      <p>
        The term <dfn><a href="https://datatracker.ietf.org/doc/html/rfc7656#section-2.1.10">RTP stream</a></dfn> is defined in [[RFC7656]].
      </p>
      <p>
        The terms <dfn data-lt="SSRC"><a href="https://datatracker.ietf.org/doc/html/rfc3550#section-3">Synchronization Source</a></dfn> (SSRC),
        <dfn data-lt="Sender Report|SR|RTCP SR"><a href="https://datatracker.ietf.org/doc/html/rfc3550#section-6.4.1">RTCP Sender Report</a></dfn> (SR),
        <dfn data-lt="Receiver Report|RR|RTCP RR"><a href="https://datatracker.ietf.org/doc/html/rfc3550#section-6.4.2">RTCP Receiver Report</a></dfn> (RR) are defined in [[RFC3550]].
      </p>
      <p>The term <dfn data-lt="Extended Report|XR"><a href="https://datatracker.ietf.org/doc/html/rfc3611">RTCP Extended Report</a></dfn> (XR) is defined in [[RFC3611]].</p>
      <p>An <dfn>audio sample</dfn> refers to having a sample in any channel of an audio track - if multiple audio channels are used, metrics based on samples do not increment at a higher rate, simultaneously having samples in multiple channels counts as a single sample.</p>
    </section>
    <section>
      <h2>
        Basic concepts
      </h2>
      <p>
        The basic object of the stats model is the [= stats object =]. The following terms are
        defined to describe it:
      </p>
      <dl>
        <dt>
          <dfn data-export>Monitored object</dfn>
        </dt>
        <dd>
          <p>
            An internal object that keeps a set of data values. Most monitored objects are object
            defined in the WebRTC API; they may be thought of as being internal properties of those
            objects.
          </p>
        </dd>
        <dt>
          <dfn data-export>Stats object</dfn>
        </dt>
        <dd>
          This is a set of values, copied out from a monitored object at a specific moment in time.
          It is returned as a WebIDL dictionary through the getStats API call.
        </dd>
        <dt>
          <dfn data-export>Stats object reference</dfn>
        </dt>
        <dd>
          <p>
            A monitored object has a stable identifier <var>id</var>, which is reflected in all stats
            objects produced from the monitored object. Stats objects may contain references to
            other stats objects using this <var>id</var> value. In a [= stats object =], these references
            are represented by a {{DOMString}} containing <var>id</var> value of the referenced stats object.
          </p>
          <p>
            All stats object references have type {{DOMString}} and member names ending in <code>Id</code>, or
            they have type <code>sequence&lt;{{DOMString}}&gt;</code> and member names ending in <code>Ids</code>.
          </p>
        </dd>
        <dt>
          <dfn data-export>Stats value</dfn>
        </dt>
        <dd>
          Refers to a single value within a stats object.
        </dd>
      </dl>
      <p>
        A monitored object changes the values it contains continuously over its lifetime, but is
        never visible through the getStats API call. A stats object, once returned, never changes.
      </p>
      <p>
        The stats API is defined in [[!WEBRTC]]. It is defined to return a collection of [= stats object =]s, each of which is a dictionary inheriting directly or indirectly from the
        <dfn class="informative" data-noexport>RTCStats</dfn> dictionary.
        This API is normatively defined in [[!WEBRTC]], but is
        reproduced here for ease of reference.
      </p>
      <pre class="idl informative">
dictionary RTCStats {
    required DOMHighResTimeStamp timestamp;
    required RTCStatsType        type;
    required DOMString           id;
};
      </pre>
      <p>
        Timestamps are expressed with {{DOMHighResTimeStamp}} [[HIGHRES-TIME]], and are defined as
        {{Performance.timeOrigin}} +
              {{Performance.now()}} at the time the information is
        collected.
      </p>
      <section>
        <h3>
          Guidelines for design of stats objects
        </h3>
        <p>
          When introducing a new stats object, the following principles should be followed:
        </p>
        <ul>
          <li>An {{RTCStats}} object should correspond to an object defined in the specification it
          supports.
          </li>
          <li>The object MUST define a new value in the {{RTCStatsType}} enum, and MUST define the
          syntax of the [= stats object =] it returns either by reference to an existing
          sub-dictionary of {{RTCStats}} or by defining a new sub-dictionary of {{RTCStats}}.
          </li>
          <li>All members of the new object need to have definitions that make them consistently
          implementable. References to other specifications are a good way of doing this.
          </li>
          <li>All members need to have defined behavior for what happens before the thing it counts
          happens, or when the information it's supposed to show is not available. Usually, this
          will be "start at zero" or "do not populate the value".
          </li>
        </ul>
        <p>
          The new members of the stats dictionary need to be named according to standard practice
          (camelCase), as per [[API-DESIGN-PRINCIPLES]].
        </p>
        <p>
          Names ending in <code>Id</code> (such as {{RTCRtpStreamStats/transportId}}) are always a [= stats object reference =];
          names ending in <code>Ids</code> are always of type sequence&lt;{{DOMString}}&gt;, where
          each {{DOMString}} is a [= stats object reference =].
        </p>
        <p>
          If the natural name for a stats value would end in <code>id</code> (such as when the stats value is
          an in-protocol identifier for the monitored object), the recommended practice is to let
          the name end in <code>identifier</code>, such as {{RTCDataChannelStats/dataChannelIdentifier}}.
        </p>
        <p>
          Stats are sampled by Javascript. In general, an application will not have overall control
          over how often stats are sampled, and the implementation cannot know what the intended
          use of the stats is. There is, by design, no control surface for the application to
          influence how stats are generated.
        </p>
        <p>
          Therefore, letting the implementation compute "average" rates is not a good idea, since
          that implies some averaging time interval that can't be set beforehand. Instead, the
          recommended approach is to count the number of measurements of a value and sum the
          measurements given even if the sum is meaningless in itself; the JS application can then
          compute averages over any desired time interval by calling getStats() twice, taking the
          difference of the two sums and dividing by the difference of the two counts.
        </p>
        <p>
          For stats that are measured against time, such as byte counts, no separate counter is
          needed; one can instead divide by the difference in the timestamps.
        </p>
      </section>
      <section>
        <h3>
          Guidelines for implementing stats objects
        </h3>
        <p>
          When implementing stats objects, the following guidelines should be adhered to:
        </p>
        <ul>
          <li>When a feature is not implemented on the platform, omit the dictionary member that is
          tracking usage of the feature.
          </li>
          <li>When a feature is not applicable to an instance of an object (for example {{RTCInboundRtpStreamStats/audioLevel}}
          on a video stream), it shall not [= map/exist =]. Do NOT report a count of zero, -1 or "empty string".
          </li>
          <li>When a feature is an instantaneous measure and it has not yet been
          sampled, it shall not [= map/exist =].</li>
          <li>When a feature is a cumulative measure and it has not been sampled yet,
          but is likely to increment in the future, report a
          count of zero. This allows subtraction of such features without additional checks for existence.
          </li>
        </ul>
      </section>
      <section>
        <h3>
          Lifetime considerations for monitored objects
        </h3>
        <p>
          The object descriptions will say what the lifetime of a [= monitored object =] from the
          perspective of stats is. When a monitored object is <dfn>deleted</dfn>, it no longer appears in
          stats; until this happens, it will appear. This may or may not correspond to the actual
          lifetime of an object in an implementation; what matters for this specification is what
          appears in stats.
        </p>
        <p>
          If a monitored object can only exist in a few instances over the lifetime of a
          {{RTCPeerConnection}}, it may be simplest to consider it "eternal" and never delete it from
          the set of objects reported on in stats. This type of object will remain visible until
          the {{RTCPeerConnection}} is no longer available; it is also visible in {{RTCPeerConnection/getStats()}} after
          pc.close(). This is the default when no lifetime is mentioned in its specification.
        </p>
        <p>
          Objects that might exist in many instances over time should have a defined time at which
          they are [= deleted =], at which time they stop appearing in subsequent calls to {{RTCPeerConnection/getStats()}}.
          When an object is [= deleted =], we can guarantee that no subsequent {{RTCPeerConnection/getStats()}} call will
          contain a [= stats object reference =] that references the deleted object. We also
          guarantee that the stats id of the deleted object will never be reused for another
          object. This ensures that an application that collects [= stats object =]s for deleted
          [= monitored object =]s will always be able to uniquely identify the object pointed to
          in the result of any {{RTCPeerConnection/getStats()}} call.
        </p>
      </section>
      <section>
        <h3>
          Guidelines for {{RTCPeerConnection/getStats()}} results caching/throttling
        </h3>
        <p>
          A call to {{RTCPeerConnection/getStats()}} touches many components of WebRTC and may take significant time to
          execute. The implementation may or may not utilize caching or throttling of {{RTCPeerConnection/getStats()}}
          calls for performance benefits, however any implementation must adhere to the following:
        </p>
        <p>
          When the state of the {{RTCPeerConnection}} visibly changes as a result of an API call, a
          promise resolving or an event firing, subsequent new {{RTCPeerConnection/getStats()}} calls must return
          up-to-date dictionaries for the affected objects.
        </p>
        <p>
          When a stats object is [= deleted =], subsequent {{RTCPeerConnection/getStats()}} calls MUST NOT return stats
          for that [= monitored object =].
        </p>
      </section>
    </section><!-- VS: getStats() remains in base spec! -->
    <section>
      <h2>
        Maintenance procedures for stats object types
      </h2>
      <section>
        <h3>
          Adding new stats objects
        </h3>
        <p class="status-ED">
          This document, in its editors' draft form, serves as the repository for the currently
          defined set of stats object types including proposals for new standard types.
        </p>
        <p class="status-not-ED">
          This document specifies the interoperable stats object types. Proposals for new object
          types may be made in <a href="https://w3c.github.io/webrtc-stats/">the editors draft
          maintained on GitHub</a>. New standard types may appear in future revisions of the W3C
          Recommendation.
        </p>
        <p>
          If a need for a new stats object type or stats value within a stats object is found, an
          issue should be <a href="https://github.com/w3c/webrtc-stats/issues">raised on
          Github</a>, and a review process will decide on whether the stat should be added to the
          editors draft or not.
        </p>
        <p>
          A pull request for a change to the editors draft may serve as guidance for the
          discussion, but the eventual merge is dependent on the review process.
        </p>
        <p>
          While the WebRTC WG exists, it will serve as the review body; once it has disbanded, the
          W3C will have to establish appropriate review.
        </p>
        <p>
          The level of review sought is that of the IETF process' "expert review", as defined in
          [[RFC5226]] section 4.1. The documentation needed includes the names of the new stats,
          their data types, and the definitions they are based on, specified to a level that allows
          interoperable implementation. The specification may consist of references to other
          documents.
        </p>
        <p>
          Another specification that wishes to refer to a specific version (for instance for
          conformance) should refer to a dated version; these will be produced regularly when
          updates happen.
        </p>
      </section>
    </section>
    <section>
      <h2>
        Procedures for mitigating privacy concerns
      </h2>
      <p class="fingerprint">
        The WebRTC's Statistics API exposes information about the system,
        including hardware capabilities and network characteristics. To limit
        the finger printing surface imposed by this API, some metrics are only
        exposed if allowed by the algorithms in this section.
      </p>
      <section>
        <h3>
          Limiting exposure of hardware capabilities
        </h3>
        <p>
          To avoid passive fingerprinting, hardware capabilities should only be
          exposed in capturing contexts. This is tested using the algorithm
          below.
        </p>
        <p>
          To <dfn data-lt="exposing hardware is allowed">check if hardware
          exposure is allowed</dfn>, run the following steps:
          <ol>
            <li>
              <p>
                If the <a href="https://w3c.github.io/mediacapture-main/#context-capturing-state">
                context capturing state</a> is true, return true.
              </p>
            </li>
            <li>
              <p>
                Otherwise return false.
              </p>
            </li>
          </ol>
        </p>
      </section>
    </section>
    <section id="rtctatstype-*">
      <h2>
        {{RTCStatsType}}
      </h2>
      <p>
        The {{RTCStats/type}} member, of type {{RTCStatsType}}, indicates the type of the
        object that the {{RTCStats}} object represents. An object with a given {{RTCStats/type}} can
        have only one IDL dictionary type, but multiple {{RTCStats/type}} values may indicate the same IDL
        dictionary type; for example, {{RTCStatsType/"local-candidate"}} and {{RTCStatsType/"remote-candidate"}} both use the IDL
        dictionary type {{RTCIceCandidateStats}}.
      </p>
      <p>
        This specification is normative for the allowed values of {{RTCStatsType}}.
      </p>
      <section id="rtcstatstype-str*">
        <h3>
          <dfn>RTCStatsType</dfn> enum
        </h3>
        <pre class="idl">
enum RTCStatsType {
"codec",
"inbound-rtp",
"outbound-rtp",
"remote-inbound-rtp",
"remote-outbound-rtp",
"media-source",
"media-playout",
"peer-connection",
"data-channel",
"transport",
"candidate-pair",
"local-candidate",
"remote-candidate",
"certificate"
};
        </pre>
        <p>
          The following strings are valid values for {{RTCStatsType}}:
        </p>
        <dl data-link-for="RTCStatsType" data-dfn-for="RTCStatsType">
          <dt>
            <dfn>codec</dfn>
          </dt>
          <dd>
            <p>
              Statistics for a codec that is currently being used by <a>RTP stream</a>s being sent or
              received by this {{RTCPeerConnection}} object. It is accessed by the
              {{RTCCodecStats}}.
            </p>
          </dd>
          <dt>
            <dfn>inbound-rtp</dfn>
          </dt>
          <dd>
            <p>
              Statistics for an inbound <a>RTP stream</a> that is currently received with this
              {{RTCPeerConnection}} object. It is accessed by the
              {{RTCInboundRtpStreamStats}}.
            </p>
            <p>
              RTX streams do not show up as separate
              {{RTCInboundRtpStreamStats}} objects but affect the {{RTCReceivedRtpStreamStats/packetsReceived}},
              {{RTCInboundRtpStreamStats/bytesReceived}}, {{RTCInboundRtpStreamStats/retransmittedPacketsReceived}}
              and {{RTCInboundRtpStreamStats/retransmittedBytesReceived}} counters of the relevant
              {{RTCInboundRtpStreamStats}} objects.
            </p>
            <p>
              FEC streams do not show up as separate
              {{RTCInboundRtpStreamStats}} objects but affect the {{RTCReceivedRtpStreamStats/packetsReceived}},
              {{RTCInboundRtpStreamStats/bytesReceived}}, {{RTCInboundRtpStreamStats/fecPacketsReceived}}
              and {{RTCInboundRtpStreamStats/fecBytesReceived}} counters of the relevant
              {{RTCInboundRtpStreamStats}} objects.
            </p>
          </dd>
          <dt>
            <dfn>outbound-rtp</dfn>
          </dt>
          <dd>
            <p>
              Statistics for an outbound <a>RTP stream</a> that is currently sent with this
              {{RTCPeerConnection}} object. It is accessed by the
              {{RTCOutboundRtpStreamStats}}.
            </p>
            <p>
              When there are multiple <a>RTP stream</a>s connected to the same sender due to using
              simulcast, there will be one {{RTCOutboundRtpStreamStats}} per <a>RTP stream</a>,
              with distinct values of the {{RTCRtpStreamStats/ssrc}} member. RTX streams do not show up as separate
              {{RTCOutboundRtpStreamStats}} objects but affect the {{RTCSentRtpStreamStats/packetsSent}},
              {{RTCSentRtpStreamStats/bytesSent}}, {{RTCOutboundRtpStreamStats/retransmittedPacketsSent}}
              and {{RTCOutboundRtpStreamStats/retransmittedBytesSent}} counters of the relevant
              {{RTCOutboundRtpStreamStats}} objects.
            </p>
          </dd>
          <dt>
            <dfn>remote-inbound-rtp</dfn>
          </dt>
          <dd>
            <p>
              Statistics for the remote endpoint's inbound <a>RTP stream</a> corresponding to an outbound
              stream that is currently sent with this {{RTCPeerConnection}} object. It is
              measured at the remote endpoint and reported in an <a>RTCP Receiver Report</a> (RR) or <a>RTCP
              Extended Report</a> (XR). It is accessed by the
              {{RTCRemoteInboundRtpStreamStats}}.
            </p>
          </dd>
          <dt>
            <dfn>remote-outbound-rtp</dfn>
          </dt>
          <dd>
            <p>
              Statistics for the remote endpoint's outbound <a>RTP stream</a> corresponding to an inbound
              stream that is currently received with this {{RTCPeerConnection}} object. It
              is measured at the remote endpoint and reported in an <a>RTCP Sender Report</a> (SR). It is
              accessed by the {{RTCRemoteOutboundRtpStreamStats}}.
            </p>
          </dd>
          <dt>
            <dfn>media-source</dfn>
          </dt>
          <dd>
            <p>
              Statistics for the media produced by a {{MediaStreamTrack}} that is
              currently attached to an {{RTCRtpSender}}. This reflects the media that is
              fed to the encoder; after <code class=gum>getUserMedia()</code> constraints have been applied
              (i.e. not the raw media produced by the camera). It is either an
              {{RTCAudioSourceStats}} or {{RTCVideoSourceStats}}
              depending on its <code class=gum>kind</code>.
            </p>
          </dd>
          <dt>
            <dfn>media-playout</dfn>
          </dt>
          <dd>
            <p>
              Statistics related to audio playout. It is accessed by the
              {{RTCAudioPlayoutStats}}.
            </p>
          </dd>
          <dt>
            <dfn>peer-connection</dfn>
          </dt>
          <dd>
            <p>
              Statistics related to the {{RTCPeerConnection}} object. It is accessed by
              the {{RTCPeerConnectionStats}}.
            </p>
          </dd>
          <dt>
            <dfn>data-channel</dfn>
          </dt>
          <dd>
            <p>
              Statistics related to each {{RTCDataChannel}} id. It is accessed by the
              {{RTCDataChannelStats}}.
            </p>
          </dd>
          <dt>
            <dfn>transport</dfn>
          </dt>
          <dd>
            <p>
              Transport statistics related to the {{RTCPeerConnection}} object. It is
              accessed by the {{RTCTransportStats}}.
            </p>
          </dd>
          <dt>
            <dfn>candidate-pair</dfn>
          </dt>
          <dd>
            <p>
              ICE candidate pair statistics related to the {{RTCIceTransport}} objects. It
              is accessed by the {{RTCIceCandidatePairStats}}.
            </p>
            <p>
              A candidate pair that is not the current pair for a transport is [= deleted =] when the
              {{RTCIceTransport}} does an ICE restart, at the time the state changes to {{RTCIceTransportState/"new"}}. The
              candidate pair that is the current pair for a transport is [= deleted =] after an ICE
              restart when the {{RTCIceTransport}} switches to using a candidate pair generated from
              the new candidates; this time doesn't correspond to any other externally observable
              event.
            </p>
          </dd>
          <dt>
            <dfn>local-candidate</dfn>
          </dt>
          <dd>
            <p>
              ICE local candidate statistics related to the {{RTCIceTransport}} objects.
              It is accessed by the {{RTCIceCandidateStats}} for the local
              candidate.
            </p>
            <p>
              A local candidate is [= deleted =] when the {{RTCIceTransport}} does an ICE restart, and the
              candidate is no longer a member of any non-deleted candidate pair.
            </p>
          </dd>
          <dt>
            <dfn>remote-candidate</dfn>
          </dt>
          <dd>
            <p>
              ICE remote candidate statistics related to the {{RTCIceTransport}} objects.
              It is accessed by the {{RTCIceCandidateStats}} for the remote
              candidate.
            </p>
            <p>
              A remote candidate is [= deleted =] when the {{RTCIceTransport}} does an ICE restart, and the
              candidate is no longer a member of any non-deleted candidate pair.
            </p>
          </dd>
          <dt>
            <dfn>certificate</dfn>
          </dt>
          <dd>
            <p>
              Information about a certificate used by an {{RTCIceTransport}}. It is accessed by the
              {{RTCCertificateStats}}.
            </p>
          </dd>
        </dl>
      </section>
    </section>
    <section>
      <h2>
        Stats dictionaries
      </h2>
      <section>
        <h3>
          The RTP statistics hierarchy
        </h3>
        <p>
          The dictionaries for RTP statistics are structured as a hierarchy, so that those stats
          that make sense in many different contexts are represented just once in IDL.
        </p>
        <p>
          The metrics exposed here correspond to local measurements and those reported by RTCP packets.
          Compound RTCP packets contain multiple RTCP report blocks, such as <a>Sender Report</a> (SR) and
          <a>Receiver Report</a> (RR) whereas a non-compound RTCP packets may contain just a single
          RTCP SR or RR block.
        </p>
        <p>
          The lifetime of all RTP [= monitored object =]s are tied to <a>SSRC</a>s.
          The {{RTCOutboundRtpStreamStats}} is created when the RTP sender is configured by
          setting a local or remote SDP answer (via <code>setLocalDescription()</code>
          or <code>setRemoteDescription()</code> and the signaling state returning to
          <code>"stable"</code>). The {{RTCInboundRtpStreamStats}} is created when
          the first RTP packet for this SSRC is received and the remote RTP stream stats
          objects ({{RTCRemoteInboundRtpStreamStats}} and {{RTCRemoteOutboundRtpStreamStats}})
          are created when the corresponding RTCP packet is first received.
        </p>
        <p>
          RTP monitored objects are deleted when the corresponding RTP sender or
          RTP receiver is reconfigured to remove the corresponding RTP stream.
          This happens for the old SSRC when the {{RTCRtpStreamStats/ssrc}}
          changes, a simulcast layer is dropped or the {{RTCRtpTransceiver}}'s
          {{RTCRtpTransceiver/currentDirection}} becomes <code>"stopped"</code>.
          The monitored object is <i>not</i> deleted if the transceiver is made
          <code>"inactive"</code> or if the encoding's
          {{RTCRtpEncodingParameters/active}} parameter is set to
          <code>false</code>. If an SSRC is recycled after a deletion event has
          happened, this is considered a new RTP monitored object and the new
          RTP stream stats will have reset counters and a new ID.
        </p>
        <p>
          For a given RTP stats object, its total counters must always increase,
          but due to changes in SSRC, simulcast layers dropping or transceivers
          stopping, an RTP stats object can be deleted and/or replaced by a new
          RTP stats object. The caller will need to be aware of this when aggregating
          packet counters across multiple RTP stats objects (the aggregates may
          decrease due to deletions).
        </p>
        <pre class="example highlight">
          An RTCRtpSender is sending two layers of simulcast (on SSRC=111 and
          SSRC=222). Two "outbound-rtp" stats objects are observed, one with
          SSRC=111, and the other with SSRC=222. Both objects' packet counters are
          increasing.

          One layer is inactivated using RTCRtpSender.setParameters(). While
          this pauses one of the layers (its packet counter freezes), the RTP
          monitored objects are not deleted. The RTCRtpTransceiver is negotiated
          as "inactive" and the RTP monitored objects are still not deleted.
          When the RTCRtpTransceiver becomes "sendonly" again, the same
          "outbound-rtp" objects continue to be used.

          Later, RTCRtpTransceiver.stop() is called. The "outbound-rtp" objects
          still exist but their packet counters have frozen. Renegotiation
          happens and the transceiver.currentDirection becomes "stopped", now
          both "outbound-rtp" objects have been deleted.
        </pre>
        <p>
          The hierarchy is as follows:
        </p>
        <p>
          {{RTCRtpStreamStats}}: Stats that apply to any end of any <a>RTP stream</a>
        </p>
        <ul>
          <li>
            <p>
              {{RTCReceivedRtpStreamStats}}: Stats measured at the receiving end of an RTP
              stream, known either because they're measured locally or transmitted via an RTCP
              <a>Receiver Report</a> (RR) or <a>Extended Report</a> (XR) block.
            </p>
            <ul>
              <li>
                <p>
                  {{RTCInboundRtpStreamStats}}: Stats that can only be measured at the local
                  receiving end of an <a>RTP stream</a>.
                </p>
              </li>
              <li>
                <p>
                  {{RTCRemoteInboundRtpStreamStats}}: Stats relevant to the remote receiving end
                  of an <a>RTP stream</a> - usually computed by combining local data with data received
                  via an RTCP <a>RR</a> or <a>XR</a> block.
                </p>
              </li>
            </ul>
          </li>
          <li>
            <p>
              {{RTCSentRtpStreamStats}}: Stats measured at the sending end of an <a>RTP stream</a>,
              known either because they're measured locally or because they're received via RTCP,
              usually in an <a>RTCP Sender Report</a> (SR).
            </p>
            <ul>
              <li>
                {{RTCOutboundRtpStreamStats}}: Stats measured locally.
              </li>
              <li>
                <p>
                  {{RTCRemoteOutboundRtpStreamStats}}: Stats relevant to the remote sending end
                  of an <a>RTP stream</a>, usually computed based on an <a>RTCP SR</a>.
                </p>
              </li>
            </ul>
          </li>
        </ul>
      </section>
      <section id="streamstats-dict*">
        <h3>
          <dfn>RTCRtpStreamStats</dfn> dictionary
        </h3>
        <div>
          <pre class="idl">dictionary RTCRtpStreamStats : RTCStats {
             required unsigned long       ssrc;
             required DOMString           kind;
             DOMString           transportId;
             DOMString           codecId;
};</pre>
          <section>
            <h2>
              Dictionary {{RTCRtpStreamStats}} Members
            </h2>
            <dl data-link-for="RTCRtpStreamStats" data-dfn-for="RTCRtpStreamStats" class=
            "dictionary-members">
              <dt>
                <dfn>ssrc</dfn> of type <span class="idlMemberType">unsigned
                long</span>
              </dt>
              <dd>
                <p>
                  The synchronization source (SSRC) identifier is an unsigned integer value per [[RFC3550]]
                  used to identify the stream of RTP packets that this stats object is describing.
                </p>
                <p>
                  For outbound and inbound local, SSRC describes the stats for the RTP stream that were
                  sent and received, respectively by those endpoints.
                  For the remote inbound and remote outbound, SSRC describes the stats for the RTP stream
                  that were received by and sent to the remote endpoint.
                </p>
              </dd>
              <dt>
                <dfn>kind</dfn> of type <span class="idlMemberType">DOMString</span>
              </dt>
              <dd>
                <p>
                  Either "<code class=gum>audio</code>" or "<code class=gum>video</code>". This
                  MUST match the <code class=gum>kind</code> attribute of the related {{MediaStreamTrack}}.
                </p>
              </dd>
              <dt>
                <dfn>transportId</dfn> of type <span class=
                "idlMemberType">DOMString</span>
              </dt>
              <dd>
                <p>
                  It is a unique identifier that is associated to the object that was inspected to
                  produce the {{RTCTransportStats}} associated with this <a>RTP stream</a>.
                </p>
              </dd>
              <dt>
                <dfn>codecId</dfn> of type <span class=
                "idlMemberType">DOMString</span>
              </dt>
              <dd>
                <p>
                  It is a unique identifier that is associated to the object that was inspected to
                  produce the {{RTCCodecStats}} associated with this <a>RTP stream</a>.
                </p>
              </dd>
            </dl>
          </section>
        </div>
      </section>
      <section id="codec-dict*">
        <h3>
          <dfn>RTCCodecStats</dfn> dictionary
        </h3>
        <p>
          Codecs are created when registered for an RTP transport,
          but only the subset of codecs that are in use (referenced by an RTP
          stream) are exposed in <code>getStats()</code>.
        </p>
        <p>
          The {{RTCCodecStats}} object is created when one or more
          {{RTCRtpStreamStats/codecId}} references the codec. When there no
          longer exists any reference to the {{RTCCodecStats}}, the stats object
          is deleted. If the same codec is used again in the future, the
          {{RTCCodecStats}} object is revived with the same {{RTCStats/id}} as
          before.
        </p>
        <p>
          Codec objects may be referenced by multiple RTP streams in
          media sections using the same transport, but similar codecs in
          different transports have different {{RTCCodecStats}} objects.
        </p>
        <p class="note">
          User agents are expected to coalesce information into a single
          <code>"codec"</code> entry per payload type per transport, unless
          {{RTCCodecStats/sdpFmtpLine}} differs per direction, in which case two
          entries (one for encode and one for decode) are needed.
        </p>
        <div>
          <pre class="idl">dictionary RTCCodecStats : RTCStats {
             required unsigned long payloadType;
             required DOMString     transportId;
             required DOMString     mimeType;
             unsigned long clockRate;
             unsigned long channels;
             DOMString     sdpFmtpLine;
};</pre>
          <section>
            <h2>
              Dictionary {{RTCCodecStats}} Members
            </h2>
            <dl data-link-for="RTCCodecStats" data-dfn-for="RTCCodecStats" class=
            "dictionary-members">
              <dt>
                <dfn>payloadType</dfn> of type <span class="idlMemberType">unsigned
                long</span>
              </dt>
              <dd>
                <p>
                  Payload type as used in RTP encoding or decoding.
                </p>
              </dd>
              <dt>
                <dfn>transportId</dfn> of type <span class=
                "idlMemberType">DOMString</span>
              </dt>
              <dd>
                <p>
                  The unique identifier of the transport on which this codec is being used, which
                  can be used to look up the corresponding {{RTCTransportStats}}
                  object.
                </p>
              </dd>
              <dt>
                <dfn>mimeType</dfn> of type <span class=
                "idlMemberType">DOMString</span>
              </dt>
              <dd>
                <p>
                  The codec MIME media type/subtype defined in the IANA media types registry
                  [[!IANA-MEDIA-TYPES]], e.g. video/VP8.
                </p>
              </dd>
              <dt>
                <dfn>clockRate</dfn> of type <span class="idlMemberType">unsigned
                long</span>
              </dt>
              <dd>
                <p>
                  Represents the media sampling rate.
                </p>
              </dd>
              <dt>
                <dfn>channels</dfn> of type <span class="idlMemberType">unsigned
                long</span>
              </dt>
              <dd>
                <p>
                  When present, indicates the number of channels (mono=1, stereo=2).
                </p>
              </dd>
              <dt>
                <dfn>sdpFmtpLine</dfn> of type <span class=
                "idlMemberType">DOMString</span>
              </dt>
              <dd>
                <p>
                  The "format specific parameters" field from the
                  <code class="sdp">a=fmtp</code> line in the SDP
                  corresponding to the codec, if one [= map/exist =]s,
                  as defined by
                  [[!RFC8829]] (<a href="https://www.rfc-editor.org/rfc/rfc8829#section-5.8">section 5.8</a>).
                </p>
              </dd>
            </dl>
          </section>
        </div>
      </section>
      <section id="receivedrtpstats-dict*">
        <h3>
          <dfn>RTCReceivedRtpStreamStats</dfn> dictionary
        </h3>
        <div>
          <pre class="idl">dictionary RTCReceivedRtpStreamStats : RTCRtpStreamStats {
             unsigned long long   packetsReceived;
             unsigned long long   packetsReceivedWithEct1;
             unsigned long long   packetsReceivedWithCe;
             unsigned long long   packetsReportedAsLost;
             unsigned long long   packetsReportedAsLostButRecovered;
             long long            packetsLost;
             double               jitter;
};</pre>
          <section>
            <h2>
              Dictionary {{RTCReceivedRtpStreamStats}} Members
            </h2>
            <dl data-link-for="RTCReceivedRtpStreamStats" data-dfn-for="RTCReceivedRtpStreamStats"
            class="dictionary-members">
              <dt>
                <dfn>packetsReceived</dfn> of type <span class=
                "idlMemberType">unsigned long long</span>
              </dt>
              <dd>
                <p>
                  Total number of RTP packets received for this <a>SSRC</a>. This includes retransmissions.
                  At the receiving endpoint, this is calculated as defined in [[!RFC3550]] section 6.4.1. At the sending
                  endpoint the {{packetsReceived}} is estimated by subtracting the Cumulative Number of Packets Lost
                  from the Extended Highest Sequence Number Received, both reported in the <a>RTCP Receiver
                  Report</a>, and then subtracting the initial Extended Sequence Number that was sent to this SSRC in a
                  <a>RTCP Sender Report</a> and then adding one, to mirror what is discussed in Appendix A.3 in [[!RFC3550]], but for the
                  sender side. If no <a>RTCP Receiver Report</a> has been received yet, then return 0.
                </p>
              </dd>
              <dt>
                <dfn>packetsReceivedWithEct1</dfn> of type <span class="idlMemberType">unsigned long long</span>
              </dt>
              <dd>
                <p>
                  Total number of RTP packets received for this <a>SSRC</a> marked with the "ECT(1)" marking.
                </p>
              </dd>
              <dt>
                <dfn>packetsReceivedWithCe</dfn> of type <span class="idlMemberType">unsigned long long</span>
              </dt>
              <dd>
                <p>
                  Total number of RTP packets received for this <a>SSRC</a> marked with the "CE" marking.
                </p>
              </dd>
              <dt>
              <dt>
                <dfn>packetsReportedAsLost</dfn> of type <span class="idlMemberType">unsigned long long</span>
              </dt>
              <dd>
                <p>
                  Total number of RTP packets for which an [[RFC8888]] section 3.1 report has been sent with a zero R bit.
                  Only [= map/exist =]s if support for the "ccfb" feedback mechanism has been negotiated.
                </p>
              </dd>
                <dt><dfn>packetsReportedAsLostButRecovered</dfn> of type <span class="idlMemberType">unsigned long long</span></dt>
              </dt>
              <dd>
                <p>
                  Total number of RTP packets for which an [[RFC8888]] section 3.1 report has been sent with a zero R bit,
                  but a later report for the same packet has the R bit set to 1.
                  Only [= map/exist =]s if support for the "ccfb" feedback mechanism has been negotiated.
                </p>
              </dd>
              <dt>
                <dfn>packetsLost</dfn> of type <span class="idlMemberType">long long</span>
              </dt>
              <dd>
                <p>
                  Total number of RTP packets lost for this <a>SSRC</a>. Calculated as defined in
                  [[!RFC3550]] section 6.4.1. Note that because of how this is estimated, it can be
                  negative if more packets are received than sent.
                </p>
              </dd>
              <dt>
                <dfn>jitter</dfn> of type <span class="idlMemberType">double</span>
              </dt>
              <dd>
                <p>
                  Packet Jitter measured in seconds for this <a>SSRC</a>. Calculated as defined in section
                  6.4.1. of [[!RFC3550]].
                </p>
              </dd>
            </dl>
          </section>
        </div>
      </section>
      <section id="inboundrtpstats-dict*">
        <h3>
          {{RTCInboundRtpStreamStats}} dictionary
        </h3>
        <p>
          The <dfn>RTCInboundRtpStreamStats</dfn> dictionary represents the measurement metrics for
          the incoming RTP media stream. The timestamp reported in the statistics object is the
          time at which the data was sampled.
        </p>
        <div>
          <pre class="idl">dictionary RTCInboundRtpStreamStats : RTCReceivedRtpStreamStats {
             required DOMString   trackIdentifier;
             DOMString            mid;
             DOMString            remoteId;
             unsigned long        framesDecoded;
             unsigned long        keyFramesDecoded;
             unsigned long        framesRendered;
             unsigned long        framesDropped;
             unsigned long        frameWidth;
             unsigned long        frameHeight;
             double               framesPerSecond;
             unsigned long long   qpSum;
             double               totalDecodeTime;
             double               totalInterFrameDelay;
             double               totalSquaredInterFrameDelay;
             unsigned long        pauseCount;
             double               totalPausesDuration;
             unsigned long        freezeCount;
             double               totalFreezesDuration;
             DOMHighResTimeStamp  lastPacketReceivedTimestamp;
             unsigned long long   headerBytesReceived;
             unsigned long long   packetsDiscarded;
             unsigned long long   fecBytesReceived;
             unsigned long long   fecPacketsReceived;
             unsigned long long   fecPacketsDiscarded;
             unsigned long long   bytesReceived;
             unsigned long        nackCount;
             unsigned long        firCount;
             unsigned long        pliCount;
             double               totalProcessingDelay;
             DOMHighResTimeStamp  estimatedPlayoutTimestamp;
             double               jitterBufferDelay;
             double               jitterBufferTargetDelay;
             unsigned long long   jitterBufferEmittedCount;
             double               jitterBufferMinimumDelay;
             unsigned long long   totalSamplesReceived;
             unsigned long long   concealedSamples;
             unsigned long long   silentConcealedSamples;
             unsigned long long   concealmentEvents;
             unsigned long long   insertedSamplesForDeceleration;
             unsigned long long   removedSamplesForAcceleration;
             double               audioLevel;
             double               totalAudioEnergy;
             double               totalSamplesDuration;
             unsigned long        framesReceived;
             DOMString            decoderImplementation;
             DOMString            playoutId;
             boolean              powerEfficientDecoder;
             unsigned long        framesAssembledFromMultiplePackets;
             double               totalAssemblyTime;
             unsigned long long   retransmittedPacketsReceived;
             unsigned long long   retransmittedBytesReceived;
             unsigned long        rtxSsrc;
             unsigned long        fecSsrc;
             double               totalCorruptionProbability;
             double               totalSquaredCorruptionProbability;
             unsigned long long   corruptionMeasurements;
            };</pre>
          <section>
            <h2>
              Dictionary {{RTCInboundRtpStreamStats}} Members
            </h2>
            <dl data-link-for="RTCInboundRtpStreamStats" data-dfn-for="RTCInboundRtpStreamStats"
            class="dictionary-members">
              <dt>
                <dfn>trackIdentifier</dfn> of type <span class=
                "idlMemberType">DOMString</span>
              </dt>
              <dd>
                <p>
                  The value of the {{MediaStreamTrack}}'s <code class=gum>id</code> attribute.
                </p>
              </dd>
              <dt>
                <dfn>mid</dfn> of type <span class=
                "idlMemberType">DOMString</span>
              </dt>
              <dd>
                <p>
                  If the {{RTCRtpTransceiver}} owning this stream has a
                  {{RTCRtpTransceiver/mid}} value that is not <code>null</code>,
                  this is that value, otherwise this member MUST NOT be
                  [= map/exist | present =].
                </p>
              </dd>
              <dt>
                <dfn>remoteId</dfn> of type <span class=
                "idlMemberType">DOMString</span>
              </dt>
              <dd>
                <p>
                  The {{remoteId}} is used for looking up the remote
                  {{RTCRemoteOutboundRtpStreamStats}} object for the same <a>SSRC</a>.
                </p>
              </dd>
              <dt>
                <dfn>framesDecoded</dfn>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for audio. It represents the total number of frames correctly decoded
                  for this <a>RTP stream</a>, i.e., frames that would be displayed if no frames are dropped.
                </p>
              </dd>
              <dt>
                <dfn>keyFramesDecoded</dfn> of type <span class=
                "idlMemberType">unsigned long</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for audio. It represents the total number of key frames, such as key
                  frames in VP8 [[RFC6386]] or IDR-frames in H.264 [[RFC6184]], successfully
                  decoded for this RTP media stream. This is a subset of
                  {{framesDecoded}}. <code>framesDecoded - keyFramesDecoded</code> gives
                  you the number of delta frames decoded.
                </p>
              </dd>
              <dt>
                <dfn>framesRendered</dfn>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for audio. It represents the total number of frames that have been
                  rendered. It is incremented just after a frame has been rendered.
                </p>
              </dd>
              <dt>
                <dfn>framesDropped</dfn> of type <span class="idlMemberType">unsigned
                long</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for audio. The total number of frames dropped prior to decode or dropped
                  because the frame missed its display deadline for this receiver's track. The measurement
                  begins when the receiver is created and is a cumulative metric as defined in
                  Appendix A (g) of [[!RFC7004]].
                </p>
              </dd>
              <dt>
                <dfn>frameWidth</dfn> of type <span class="idlMemberType">unsigned
                long</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for audio. Represents the width of the last decoded frame. Before the
                  first frame is decoded this member MUST NOT [= map/exist =].
                </p>
              </dd>
              <dt>
                <dfn>frameHeight</dfn> of type <span class="idlMemberType">unsigned
                long</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for audio. Represents the height of the last decoded frame. Before
                  the first frame is decoded this member MUST NOT [= map/exist =].
                </p>
              </dd>
              <dt>
                <dfn>framesPerSecond</dfn> of type <span class=
                "idlMemberType">double</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for audio. The number of decoded frames in the last second.
                </p>
              </dd>
              <dt>
                <dfn>qpSum</dfn> of type <span class="idlMemberType">unsigned long
                long</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for audio. The sum of the QP values of frames decoded by this
                  receiver. The count of frames is in {{framesDecoded}}.

                </p>
                <p>
                  The definition of QP value depends on the codec; for VP8, the QP value is the
                  value carried in the frame header as the syntax element <code class=vp8>y_ac_qi</code>, and defined in
                  [[RFC6386]] section 19.2. Its range is 0..127.
                  <!-- Need appropriate references for VP9 and H.264 -->
                </p>
                <p>
                  Note that the QP value is only an indication of quantizer values used; many
                  formats have ways to vary the quantizer value within the frame.
                </p>
              </dd>
              <dt>
                <dfn>totalDecodeTime</dfn> of type <span class=
                "idlMemberType">double</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for audio.
                  Total number of seconds that have been spent decoding the {{framesDecoded}}
                  frames of this stream. The average decode time can be calculated by dividing this
                  value with {{framesDecoded}}. The time it takes to decode one frame is the
                  time passed between feeding the decoder a frame and the decoder returning decoded
                  data for that frame.
                </p>
              </dd>
              <dt>
                <dfn>totalInterFrameDelay</dfn> of type <span class=
                "idlMemberType">double</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for audio.
                  Sum of the interframe delays in seconds between consecutively rendered frames,
                  recorded just after a frame has been rendered. The interframe delay variance be
                  calculated from {{totalInterFrameDelay}}, {{totalSquaredInterFrameDelay}},
                  and {{framesRendered}} according to the formula:
                  ({{totalSquaredInterFrameDelay}} - {{totalInterFrameDelay}}^2/
                  {{framesRendered}})/{{framesRendered}}.
                </p>
              </dd>
              <dt>
                <dfn>totalSquaredInterFrameDelay</dfn> of type <span class=
                "idlMemberType">double</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for audio.
                  Sum of the squared interframe delays in seconds between consecutively rendered frames,
                  recorded just after a frame has been rendered. See {{totalInterFrameDelay}} for
                  details on how to calculate the interframe delay variance.
                </p>
              </dd>
              <dt>
                <dfn><code>pauseCount</code></dfn> of type
                <span class="idlMemberType">unsigned long</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for audio.
                  Count the total number of video pauses experienced by this receiver.
                  Video is considered to be paused if time passed since last rendered
                  frame exceeds 5 seconds. {{pauseCount}} is incremented when a frame
                  is rendered after such a pause.
                </p>
              </dd>
              <dt>
                <dfn><code>totalPausesDuration</code></dfn> of type
                <span class="idlMemberType">double</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for audio.
                  Total duration of pauses (for definition of pause see {{pauseCount}}),
                  in seconds. This value is updated when a frame is rendered.
                </p>
              </dd>
              <dt>
                <dfn><code>freezeCount</code></dfn> of type
                <span class="idlMemberType">unsigned long</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for audio.
                  Count the total number of video freezes experienced by this receiver.
                  It is a freeze if frame duration, which is time interval between two
                  consecutively rendered frames, is equal or exceeds
                  Max(3 * avg_frame_duration_ms, avg_frame_duration_ms + 150), where
                  avg_frame_duration_ms is linear average of durations of last 30 rendered
                  frames.
                </p>
              </dd>
              <dt>
                <dfn><code>totalFreezesDuration</code></dfn> of type
                <span class="idlMemberType">double</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for audio.
                  Total duration of rendered frames which are considered as frozen (for
                  definition of freeze see {{freezeCount}}), in seconds. This value
                  is updated when a frame is rendered.
                </p>
              </dd>
              <dt>
                <dfn>lastPacketReceivedTimestamp</dfn> of type <span class=
                "idlMemberType">DOMHighResTimeStamp</span>
              </dt>
              <dd>
                <p>
                  Represents the timestamp at which the last packet was received for this <a>SSRC</a>.
                  This differs from {{RTCStats/timestamp}}, which represents the time at which the
                  statistics were generated by the local endpoint.
                </p>
              </dd>
              <dt>
                <dfn>headerBytesReceived</dfn> of type <span class=
                "idlMemberType">unsigned long long</span>
              </dt>
              <dd>
                <p>
                  Total number of RTP header and padding bytes received for this <a>SSRC</a>.
                  This includes retransmissions.
                  This does not include the size of transport layer headers such as IP or UDP.
                  <code>headerBytesReceived + bytesReceived</code> equals the number of bytes
                  received as payload over the transport.
                </p>
              </dd>
              <dt>
                <dfn>packetsDiscarded</dfn> of type <span class=
                "idlMemberType">unsigned long long</span>
              </dt>
              <dd>
                <p>
                  The cumulative number of RTP packets discarded by the jitter buffer due to late
                  or early-arrival, i.e., these packets are not played out. RTP packets discarded
                  due to packet duplication are not reported in this metric [[XRBLOCK-STATS]].
                  Calculated as defined in [[!RFC7002]] section 3.2 and Appendix A.a.
                </p>
              </dd>
              <dt>
                <dfn>fecBytesReceived</dfn> of type <span class=
                "idlMemberType">unsigned long long</span>
              </dt>
              <dd>
                <p>
                  Total number of RTP FEC bytes received for this <a>SSRC</a>, only including payload bytes.
                  This is a subset of {{RTCInboundRtpStreamStats/bytesReceived}}. If a FEC mechanism that
                  uses a different {{RTCRtpStreamStats/ssrc}} was negotiated, FEC packets are sent over a
                  separate SSRC but is still accounted for here.
                </p>
              </dd>
              <dt>
                <dfn>fecPacketsReceived</dfn> of type <span class=
                "idlMemberType">unsigned long long</span>
              </dt>
              <dd>
                <p>
                  Total number of RTP FEC packets received for this <a>SSRC</a>. If a FEC mechanism that
                  uses a different {{RTCRtpStreamStats/ssrc}} was negotiated, FEC packets are sent over a
                  separate SSRC but is still accounted for here.
                  This counter can also be incremented when receiving FEC packets in-band with media packets
                  (e.g., with Opus).
                </p>
              </dd>
              <dt>
                <dfn>fecPacketsDiscarded</dfn> of type <span class=
                "idlMemberType">unsigned long long</span>
              </dt>
              <dd>
                <p>
                  Total number of RTP FEC packets received for this <a>SSRC</a> where the error correction
                  payload was discarded by the application. This may happen 1. if all the source
                  packets protected by the FEC packet were received or already recovered by a
                  separate FEC packet, or 2. if the FEC packet arrived late, i.e., outside the
                  recovery window, and the lost RTP packets have already been skipped during
                  playout. This is a subset of {{fecPacketsReceived}}.
                </p>
              </dd>
              <dt>
                <dfn>bytesReceived</dfn> of type <span class="idlMemberType">unsigned
                long long</span>
              </dt>
              <dd>
                <p>
                  Total number of bytes received for this <a>SSRC</a>. This includes retransmissions.
                  Calculated as defined in [[!RFC3550]] section 6.4.1.
                </p>
              </dd>
              <dt>
                <dfn>firCount</dfn> of type <span class="idlMemberType">unsigned
                long</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for audio. Count the total number of Full Intra Request (FIR) packets,
                  as defined in [[!RFC5104]] section 4.3.1, sent by this receiver. Does not count the RTCP FIR
                  indicated in [[?RFC2032]] which was deprecated by [[?RFC4587]].
                </p>
              </dd>
              <dt>
                <dfn>pliCount</dfn> of type <span class="idlMemberType">unsigned
                long</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for audio. Count the total number of Picture Loss Indication (PLI)
                  packets, as defined in [[!RFC4585]] section 6.3.1, sent by this receiver.
                </p>
              </dd>
              <dt>
                <dfn>totalProcessingDelay</dfn> of type <span class=
                "idlMemberType">double</span>
              </dt>
              <dd>
                <p>
                  It is the sum of the time, in seconds, each <a>audio sample</a> or video frame takes from
                  the time the first RTP packet is received (reception timestamp) and to the time
                  the corresponding sample or frame is decoded (decoded timestamp). At this point the audio
                  sample or video frame is ready for playout by the MediaStreamTrack. Typically ready for
                  playout here means after the audio sample or video frame is fully decoded by the decoder.
                </p>
                <p>
                  Given the complexities involved, the time of arrival or the reception timestamp is measured
                  as close to the network layer as possible and the decoded timestamp is measured as soon as the
                  complete sample or frame is decoded.
                </p>
                <p>
                  In the case of audio, several samples are received in the same RTP packet, all samples
                  will share the same reception timestamp and different decoded timestamps.
                  In the case of video, the frame is received over several RTP packets, in this
                  case the earliest timestamp containing the frame is counted as the reception timestamp,
                  and the decoded timestamp corresponds to when the complete frame is decoded.
                </p>
                <p>
                  This metric is not incremented for frames that are not decoded,
                  i.e. {{RTCInboundRtpStreamStats/framesDropped}}.
                  The average processing delay can be calculated by dividing the {{totalProcessingDelay}} with the
                  {{framesDecoded}} for video (or provisional stats spec <code>totalSamplesDecoded</code> for audio).
                </p>
              </dd>
              <dt>
                <dfn>nackCount</dfn> of type <span class="idlMemberType">unsigned
                long</span>
              </dt>
              <dd>
                <p>
                  Count the total number of Negative ACKnowledgement (NACK) packets, as defined in [[!RFC4585]]
                  section 6.2.1, sent by this receiver.
                </p>
              </dd>
              <dt>
                <dfn>estimatedPlayoutTimestamp</dfn> of type <span class=
                "idlMemberType">DOMHighResTimeStamp</span>
              </dt>
              <dd>
                <p>
                  This is the estimated playout time of this receiver's track. The playout time is
                  the NTP timestamp of the last playable <a>audio sample</a> or video frame that has a known
                  timestamp (from an <a>RTCP SR</a> packet mapping RTP timestamps to NTP timestamps),
                  extrapolated with the time elapsed since it was ready to be played out. This is
                  the "current time" of the track in NTP clock time of the sender and can be present
                  even if there is no audio currently playing.
                </p>
                <p>
                  This can be useful for estimating how much audio and video is out of sync for two
                  tracks from the same source, <var>audioInboundRtpStats</var>.{{estimatedPlayoutTimestamp}} -
                  <var>videoInboundRtpStats</var>.{{estimatedPlayoutTimestamp}}.
                </p>
              </dd>
              <dt>
                <dfn>jitterBufferDelay</dfn> of type <span class=
                "idlMemberType">double</span>
              </dt>
              <dd>
                <p>
                  The purpose of the jitter buffer is to recombine RTP packets into frames (in the case of video)
                  and have smooth playout. The model described here assumes that the samples or frames are
                  still compressed and have not yet been decoded.
                  It is the sum of the time, in seconds, each <a>audio sample</a> or a video frame takes from
                  the time the first packet is received by the jitter buffer (ingest timestamp) to the
                  time it exits the jitter buffer (emit timestamp).
                  In the case of audio, several samples belong to the same RTP packet, hence they will have the same
                  ingest timestamp but different jitter buffer emit timestamps.
                  In the case of video, the frame maybe is received over several RTP packets, hence the ingest timestamp
                  is the earliest packet of the frame that entered the jitter buffer and the emit timestamp is
                  when the whole frame exits the jitter buffer.
                  This metric increases upon samples or frames exiting, having completed their time in the buffer (and
                  incrementing {{jitterBufferEmittedCount}}). The average jitter buffer
                  delay can be calculated by dividing the {{jitterBufferDelay}} with the
                  {{jitterBufferEmittedCount}}.
                </p>
              </dd>
              <dt>
                <dfn><code>jitterBufferTargetDelay</code></dfn> of type <span class=
                "idlMemberType">double</span>
              </dt>
              <dd>
                <p>
                  This value is increased by the target jitter buffer delay every time a
                  sample is emitted by the jitter buffer. The added target is the target
                  delay, in seconds, at the time that the sample was emitted from the
                  jitter buffer. To get the average target delay, divide by
                  {{jitterBufferEmittedCount}}.
                </p>
              </dd>
              <dt>
                <dfn>jitterBufferEmittedCount</dfn> of type <span class=
                "idlMemberType">unsigned long long</span>
              </dt>
              <dd>
                <p>
                  The total number of <a>audio sample</a>s or video frames that have come out of the
                  jitter buffer (increasing {{jitterBufferDelay}}).
                </p>

              </dd>
              <dt>
                <dfn>jitterBufferMinimumDelay</dfn> of type <span class=
                "idlMemberType">double</span>
              </dt>
              <dd>
                <p>
                  There are various reasons why the jitter buffer delay might be increased to a higher value, such as
                  to achieve AV synchronization or because a
                  <a href="https://w3c.github.io/webrtc-extensions/#dom-rtcrtpreceiver-jitterbuffertarget">jitterBufferTarget</a>
                  was set on a RTCRtpReceiver. When using one of these mechanisms, it can be useful to keep track of
                  the minimal jitter buffer delay that could have been achieved, so WebRTC clients can track the amount
                  of additional delay that is being added.
                </p><p>
                  This metric works the same way as {{jitterBufferTargetDelay}}, except that it is not affected by
                  external mechanisms that increase the jitter buffer target delay, such as jitterBufferTarget (see link above),
                  AV sync, or any other mechanisms. This metric is purely based on the network characteristics such
                  as jitter and packet loss, and can be seen as the minimum obtainable jitter buffer delay if no
                  external factors would affect it. The metric is updated every time {{jitterBufferEmittedCount}} is updated.
                </p>
              </dd>
              <dt>
                <dfn>totalSamplesReceived</dfn> of type <span class=
                "idlMemberType">unsigned long long</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for video. The total number of samples that have been received on this
                  RTP stream. This includes {{concealedSamples}}.
                </p>
              </dd>
              <dt>
                <dfn>concealedSamples</dfn> of type <span class=
                "idlMemberType">unsigned long long</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for video. The total number of samples that are concealed samples. A
                  concealed sample is a sample that was replaced with synthesized samples generated
                  locally before being played out. Examples of samples that have to be concealed
                  are samples from lost packets (reported in {{RTCReceivedRtpStreamStats/packetsLost}}) or samples from packets that arrive
                  too late to be played out (reported in {{RTCInboundRtpStreamStats/packetsDiscarded}}).
                </p>

              </dd>
              <dt>
                <dfn>silentConcealedSamples</dfn> of type <span class=
                "idlMemberType">unsigned long long</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for video. The total number of concealed samples inserted that are
                  "silent". Playing out silent samples results in silence or comfort noise. This is
                  a subset of {{concealedSamples}}.
                </p>

              </dd>
              <dt>
                <dfn>concealmentEvents</dfn> of type <span class=
                "idlMemberType">unsigned long long</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for video. The number of concealment events. This counter increases every
                  time a concealed sample is synthesized after a non-concealed sample. That is, multiple
                  consecutive concealed samples will increase the {{concealedSamples}} count multiple
                  times but is a single concealment event.
                </p>

              </dd>
              <dt>
                <dfn>insertedSamplesForDeceleration</dfn> of type <span class=
                "idlMemberType">unsigned long long</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for video. When playout is slowed down, this counter is increased by the
                  difference between the number of samples received and the number of samples played out.
                  If playout is slowed down by inserting samples, this will be the number of inserted
                  samples.
                </p>

              </dd>
              <dt>
                <dfn>removedSamplesForAcceleration</dfn> of type <span class=
                "idlMemberType">unsigned long long</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for video. When playout is sped up, this counter is increased by the
                  difference between the number of samples received and the number of samples played
                  out. If speedup is achieved by removing samples, this will be the count of samples
                  removed.
                </p>

              </dd>
              <dt>
                <dfn>audioLevel</dfn> of type <span class=
                "idlMemberType">double</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for video. Represents the audio level of the receiving track. For audio
                  levels of tracks attached locally, see {{RTCAudioSourceStats}}
                  instead.
                </p>
                <p>
                  The value is between 0..1 (linear), where 1.0 represents 0 dBov, 0 represents
                  silence, and 0.5 represents approximately 6 dBSPL change in the sound pressure
                  level from 0 dBov.
                </p>
                <p>
                  The {{audioLevel}} is averaged over some small interval, using the algorithm
                  described under {{totalAudioEnergy}}. The interval used is [=implementation-defined=].
                </p>
              </dd>
              <dt>
                <dfn>totalAudioEnergy</dfn> of type <span class=
                "idlMemberType">double</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for video. Represents the audio energy of the receiving track. For
                  audio energy of tracks attached locally, see
                  {{RTCAudioSourceStats}} instead.
                </p>
                <p>
                  This value MUST be computed as follows: for each <a>audio sample</a> that is received
                  (and thus counted by {{totalSamplesReceived}}), add the sample's
                  value divided by the highest-intensity encodable value, squared and then
                  multiplied by the duration of the sample in seconds. In other words,
                  <code>duration * Math.pow(energy/maxEnergy, 2)</code>.
                </p>
                <p>
                  This can be used to obtain a root mean square (RMS) value that uses the same
                  units as {{audioLevel}}, as defined in [[RFC6464]]. It can be
                  converted to these units using the formula
                  <code>Math.sqrt(totalAudioEnergy/totalSamplesDuration)</code>. This calculation
                  can also be performed using the differences between the values of two different
                  {{RTCPeerConnection/getStats()}} calls, in order to compute the average audio level over
                  any desired time interval. In other words, do <code>Math.sqrt((energy2 -
                  energy1)/(duration2 - duration1))</code>.
                </p>
                <p>
                  For example, if a 10ms packet of audio is produced with an RMS of 0.5 (out of
                  1.0), this should add <code>0.5 * 0.5 * 0.01 = 0.0025</code> to
                  {{totalAudioEnergy}}. If another 10ms packet with an RMS of 0.1 is
                  received, this should similarly add <code>0.0001</code> to
                  {{totalAudioEnergy}}. Then,
                  <code>Math.sqrt(totalAudioEnergy/totalSamplesDuration)</code> becomes
                  <code>Math.sqrt(0.0026/0.02) = 0.36</code>, which is the same value that would be
                  obtained by doing an RMS calculation over the contiguous 20ms segment of audio.
                </p>
                <p>
                  If multiple audio channels are used, the
                  audio energy of a sample refers to the <strong>highest energy</strong> of any
                  channel.
                </p>
              </dd>
              <dt>
                <dfn>totalSamplesDuration</dfn> of type <span class=
                "idlMemberType">double</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for video. Represents the audio duration of the receiving track. For
                  audio durations of tracks attached locally, see
                  {{RTCAudioSourceStats}} instead.
                </p>
                <p>
                  Represents the total duration in seconds of all samples that have been received
                  (and thus counted by {{totalSamplesReceived}}). Can be used with
                  {{totalAudioEnergy}} to compute an average audio level over
                  different intervals.
                </p>

              </dd>
              <dt>
                <dfn>framesReceived</dfn> of type <span class="idlMemberType">unsigned
                long</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for audio. Represents the total number of complete frames received on
                  this <a>RTP stream</a>. This metric is incremented when the complete frame is received.
                </p>
              </dd>
              <dt>
                <dfn>decoderImplementation</dfn> of type <span class=
                "idlMemberType">DOMString</span>
              </dt>
              <dd>
                <p class="fingerprint">
                  MUST NOT [= map/exist =] unless [= exposing hardware is allowed =].
                </p>
                <p>
                  MUST NOT [= map/exist =] for audio. Identifies the decoder implementation used.
                  This is useful for diagnosing interoperability issues.
                </p>
              </dd>
              <dt>
                <dfn>playoutId</dfn> of type <span class=
                "idlMemberType">DOMString</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for video.
                  If audio playout is happening, this is used to look up the
                  corresponding {{RTCAudioPlayoutStats}}.
                </p>
              </dd>
              <dt>
                <dfn>powerEfficientDecoder</dfn> of type <span class=
                "idlMemberType">boolean</span>
              </dt>
              <dd>
                <p class="fingerprint">
                  MUST NOT [= map/exist =] unless [= exposing hardware is allowed =].
                </p>
                <p>
                  MUST NOT [= map/exist =] for audio.
                  Whether the decoder currently used is considered power
                  efficient by the user agent. This SHOULD reflect if the
                  configuration results in hardware acceleration, but the user
                  agent MAY take other information into account when deciding if
                  the configuration is considered power efficient.
                </p>
              </dd>
              <dt>
                <dfn>framesAssembledFromMultiplePackets</dfn> of type <span class=
                "idlMemberType">unsigned long</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for audio.
                  It represents the total number of frames correctly decoded
                  for this RTP stream that consist of more than one RTP packet. For such frames the
                  {{totalAssemblyTime}} is incremented. The average frame assembly time can be calculated by
                  dividing the {{totalAssemblyTime}} with {{framesAssembledFromMultiplePackets}}.
                </p>
              </dd>
              <dt>
                <dfn>totalAssemblyTime</dfn> of type <span class=
                "idlMemberType">double</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for audio.
                  The sum of the time, in seconds, each video frame takes
                  from the time the first RTP packet is received (reception timestamp) and to the time
                  the last RTP packet of a frame is received. Only incremented for frames consisting of more
                  than one RTP packet.
                </p>
                <p>
                  Given the complexities involved, the time of arrival or the reception timestamp is measured
                  as close to the network layer as possible. This metric is not incremented for frames that
                  are not decoded, i.e., {{framesDropped}} or frames that fail decoding for other reasons
                  (if any). Only incremented for frames consisting of more than one RTP packet.
                </p>
              </dd>
              <dt>
                <dfn>retransmittedPacketsReceived</dfn> of type <span class=
                "idlMemberType">unsigned long long</span>
              </dt>
              <dd>
                <p>
                  The total number of retransmitted packets that were received for this <a>SSRC</a>. This is a
                  subset of {{RTCReceivedRtpStreamStats/packetsReceived}}. If RTX is not negotiated,
                  retransmitted packets can not be identified and this member MUST NOT [= map/exist =].
                </p>
              </dd>
              <dt>
                <dfn>retransmittedBytesReceived</dfn> of type <span class=
                "idlMemberType">unsigned long long</span>
              </dt>
              <dd>
                <p>
                  The total number of retransmitted bytes that were received for this <a>SSRC</a>, only including
                  payload bytes. This is a subset of {{RTCInboundRtpStreamStats/bytesReceived}}. If RTX is not
                  negotiated, retransmitted packets can not be identified and this member MUST NOT [= map/exist =].
                </p>
              </dd>
              <dt>
                <dfn>rtxSsrc</dfn> of type <span class=
                "idlMemberType">unsigned long</span>
              </dt>
              <dd>
                <p>
                  If RTX is negotiated for retransmissions on a separate <a>RTP stream</a>, this is the SSRC
                  of the RTX stream that is associated with this stream's {{RTCRtpStreamStats/ssrc}}.
                  If RTX is not negotiated, this value MUST NOT be [= map/exist | present =].
                </p>
              </dd>
              <dt>
                <dfn>fecSsrc</dfn> of type <span class=
                "idlMemberType">unsigned long</span>
              </dt>
              <dd>
                <p>
                  If a FEC mechanism that uses a separate <a>RTP stream</a> is negotiated, this is the SSRC
                  of the FEC stream that is associated with this stream's {{RTCRtpStreamStats/ssrc}}.
                  If FEC is not negotiated or uses the same <a>RTP stream</a>, this value MUST NOT be
                  [= map/exist | present =].
                </p>
              </dd>
              <dt>
                <dfn>totalCorruptionProbability</dfn> of type <span class=
                "idlMemberType">double</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for audio. Represents the cumulative sum of all corruption
                  probability measurements that have been made for this SSRC, see {{corruptionMeasurements}}
                  regarding when this attribute SHOULD be [= map/exist | present =].
                </p>
                <p>
                  Each measurement added to {{totalCorruptionProbability}} MUST be in the range [0.0, 1.0],
                  where a value of 0.0 indicates the system has estimated there is no or negligible corruption
                  present in the processed frame. Similarly a value of 1.0 indicates there is almost certainly
                  a corruption visible in the processed frame. A value in between those two indicates there is
                  likely some corruption visible, but it could for instance have a low magnitude or be present
                  only in a small portion of the frame.
                </p>
                <p class="note">
                  The corruption likelihood values are estimates - not guarantees. Even if the estimate is
                  0.0, there could be corruptions present (i.e. it's a false negative) for instance if only a
                  very small area of the frame is affected. Similarly, even if the estimate is 1.0 there might
                  not be a corruption present (i.e. it's a false positive) for instance if there are
                  macroblocks with a QP far higher than the frame average.
                  Just like there are edge cases for e.g. PSNR measurements, these metrics should primarily
                  be used as a basis for statistical analysis rather than be used as an absolute truth on a
                  per-frame basis.
                </p>
              </dd>
              <dt>
                <dfn>totalSquaredCorruptionProbability</dfn> of type <span class=
                "idlMemberType">double</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for audio. Represents the cumulative sum of all corruption
                  probability measurements squared that have been made for this SSRC, see
                  {{corruptionMeasurements}} regarding when this attribute SHOULD be [= map/exist | present =].
                </p>
              </dd>
              <dt>
                <dfn>corruptionMeasurements</dfn> of type <span class=
                "idlMemberType">unsigned long long</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for audio. When the user agent is able to make a corruption
                  probability measurement, this counter is incremented for each such measurement and
                  {{totalCorruptionProbability}} and {{totalSquaredCorruptionProbability}} are aggregated
                  with this measurement and measurement squared respectively.
                  If the <a href="http://www.webrtc.org/experiments/rtp-hdrext/corruption-detection">
                  corruption-detection</a> header extension is present in the RTP packets, corruption
                  probability measurements MUST be [= map/exist | present =].
                </p>
                <p class="note">
                  The corruption-detection header extension documented at
                  <a href="http://www.webrtc.org/experiments/rtp-hdrext/corruption-detection">
                  http://www.webrtc.org/experiments/rtp-hdrext/corruption-detection</a> is experimental. The
                  identifier and format may change once an IETF standard has been established.
                </p>
              </dd>
            </dl>
          </section>
        </div>
      </section>
      <section id="remoteinboundrtpstats-dict*">
        <h3>
          {{RTCRemoteInboundRtpStreamStats}} dictionary
        </h3>
        <p>
          The <dfn>RTCRemoteInboundRtpStreamStats</dfn> dictionary represents the remote endpoint's
          measurement metrics for a particular incoming <a>RTP stream</a> (corresponding to an outgoing
          <a>RTP stream</a> at the sending endpoint). The timestamp reported in the statistics object is
          the time at which the corresponding <a>RTCP RR</a> was received.
        </p>
        <div>
          <pre class="idl">dictionary RTCRemoteInboundRtpStreamStats : RTCReceivedRtpStreamStats {
             DOMString            localId;
             double               roundTripTime;
             double               totalRoundTripTime;
             double               fractionLost;
             unsigned long long   roundTripTimeMeasurements;
             unsigned long long   packetsWithBleachedEct1Marking;
};</pre>
          <section>
            <h2>
              Dictionary {{RTCRemoteInboundRtpStreamStats}} Members
            </h2>
            <dl data-link-for="RTCRemoteInboundRtpStreamStats" data-dfn-for=
            "RTCRemoteInboundRtpStreamStats" class="dictionary-members">
              <dt>
                <dfn>localId</dfn> of type <span class=
                "idlMemberType">DOMString</span>
              </dt>
              <dd>
                <p>
                  The {{localId}} is used for looking up the local
                  {{RTCOutboundRtpStreamStats}} object for the same <a>SSRC</a>.
                </p>
              </dd>
              <dt>
                <dfn>roundTripTime</dfn> of type <span class=
                "idlMemberType">double</span>
              </dt>
              <dd>
                <p>
                  Estimated round trip time for this <a>SSRC</a> based on the RTCP timestamps in the RTCP
                  Receiver Report (RR) and measured in seconds. Calculated as defined in section
                  6.4.1. of [[!RFC3550]]. MUST NOT [= map/exist =] until a <a>RTCP Receiver Report</a> is
                  received with a DLSR value other than 0 has been received.
                </p>
              </dd>
              <dt>
                <dfn>totalRoundTripTime</dfn> of type <span class=
                "idlMemberType">double</span>
              </dt>
              <dd>
                <p>
                  Represents the cumulative sum of all round trip time measurements in seconds
                  since the beginning of the session. The individual round trip time is calculated
                  based on the RTCP timestamps in the <a>RTCP Receiver Report</a> (RR) [[!RFC3550]], hence
                  requires a DLSR value other than 0. The average round trip time can be computed
                  from {{totalRoundTripTime}} by dividing it by
                  {{roundTripTimeMeasurements}}.
                </p>
              </dd>
              <dt>
                <dfn>fractionLost</dfn> of type <span class=
                "idlMemberType">double</span>
              </dt>
              <dd>
                <p>
                  The fraction packet loss reported for this <a>SSRC</a>. Calculated as defined in
                  [[!RFC3550]] section 6.4.1 and Appendix A.3.
                </p>
              </dd>
              <dt>
                <dfn>roundTripTimeMeasurements</dfn> of type <span class=
                "idlMemberType">unsigned long long</span>
              </dt>
              <dd>
                <p>
                  Represents the total number of <a>RTCP RR</a> blocks received for this <a>SSRC</a> that contain
                  a valid round trip time. This counter will not increment if the {{roundTripTime}} can not
                  be calculated because no <a>RTCP Receiver Report</a> with a DLSR value other than 0 has been received.
                </p>
              </dd>
              <dt>
                <dfn>packetsWithBleachedEct1Marking</dfn> of type <span class="idlMemberType">unsigned long long</span>
              </dt>
              <dd>
                <p>
                  Number of packets that were sent with ECT(1) markings per [[RFC3168]] section 3, but where an
                  [[RFC8888]] report gave information that the packet was received with a marking of "not-ECT".
                </p>
            </dl>
          </section>
        </div>
      </section>
      <section id="sentrtpstats-dict*">
        <h3>
          <dfn>RTCSentRtpStreamStats</dfn> dictionary
        </h3>
        <div>
          <pre class="idl">dictionary RTCSentRtpStreamStats : RTCRtpStreamStats {
            unsigned long long packetsSent;
            unsigned long long bytesSent;
};</pre>
          <section>
            <h2>
              Dictionary {{RTCSentRtpStreamStats}} Members
            </h2>
            <dl data-link-for="RTCSentRtpStreamStats" data-dfn-for="RTCSentRtpStreamStats" class=
            "dictionary-members">
              <dt>
                <dfn>packetsSent</dfn> of type <span class="idlMemberType">unsigned
                long long</span>
              </dt>
              <dd>
                <p>
                  Total number of RTP packets sent for this <a>SSRC</a>. This includes retransmissions.
                  Calculated as defined in [[!RFC3550]] section 6.4.1.
                </p>
              </dd>
              <dt>
                <dfn>bytesSent</dfn> of type <span class="idlMemberType">unsigned long
                long</span>
              </dt>
              <dd>
                <p>
                  Total number of bytes sent for this <a>SSRC</a>. This includes retransmissions.
                  Calculated as defined in [[!RFC3550]] section 6.4.1.
                </p>
              </dd>
            </dl>
          </section>
        </div>
      </section>
      <section id="outboundrtpstats-dict*">
        <h3>
          {{RTCOutboundRtpStreamStats}} dictionary
        </h3>
        <p>
          The <dfn>RTCOutboundRtpStreamStats</dfn> dictionary represents the measurement metrics
          for the outgoing <a>RTP stream</a>. The timestamp reported in the statistics object is the time
          at which the data was sampled.
        </p>
        <div>
          <pre class="idl">dictionary RTCOutboundRtpStreamStats : RTCSentRtpStreamStats {
             DOMString            mid;
             DOMString            mediaSourceId;
             DOMString            remoteId;
             DOMString            rid;
             unsigned long        encodingIndex;
             unsigned long long   headerBytesSent;
             unsigned long long   retransmittedPacketsSent;
             unsigned long long   retransmittedBytesSent;
             unsigned long        rtxSsrc;
             double               targetBitrate;
             unsigned long long   totalEncodedBytesTarget;
             unsigned long        frameWidth;
             unsigned long        frameHeight;
             double               framesPerSecond;
             unsigned long        framesSent;
             unsigned long        hugeFramesSent;
             unsigned long        framesEncoded;
             unsigned long        keyFramesEncoded;
             unsigned long long   qpSum;
             record&lt;DOMString, double&gt; psnrSum;
             unsigned long long   psnrMeasurements;
             double               totalEncodeTime;
             double               totalPacketSendDelay;
             RTCQualityLimitationReason                 qualityLimitationReason;
             record&lt;DOMString, double&gt; qualityLimitationDurations;
             unsigned long        qualityLimitationResolutionChanges;
             unsigned long        nackCount;
             unsigned long        firCount;
             unsigned long        pliCount;
             DOMString            encoderImplementation;
             boolean              powerEfficientEncoder;
             boolean              active;
             DOMString            scalabilityMode;
             unsigned long long   packetsSentWithEct1;
};</pre>
          <section>
            <h2>
              Dictionary {{RTCOutboundRtpStreamStats}} Members
            </h2>
            <dl data-link-for="RTCOutboundRtpStreamStats" data-dfn-for="RTCOutboundRtpStreamStats"
            class="dictionary-members">
              <dt>
                <dfn>mid</dfn> of type <span class=
                "idlMemberType">DOMString</span>
              </dt>
              <dd>
                <p>
                  If the {{RTCRtpTransceiver}} owning this stream has a
                  {{RTCRtpTransceiver/mid}} value that is not <code>null</code>,
                  this is that value, otherwise this member MUST NOT be
                  [= map/exist | present =].
                </p>
              </dd>
              <dt>
                <dfn>mediaSourceId</dfn> of type <span class=
                "idlMemberType">DOMString</span>
              </dt>
              <dd>
                <p>
                  The identifier of the stats object representing the track currently attached to the
                  sender of this stream, an {{RTCMediaSourceStats}}.
                </p>
              </dd>
              <dt>
                <dfn>remoteId</dfn> of type <span class=
                "idlMemberType">DOMString</span>
              </dt>
              <dd>
                <p>
                  The {{remoteId}} is used for looking up the remote
                  {{RTCRemoteInboundRtpStreamStats}} object for the same <a>SSRC</a>.
                </p>
              </dd>
              <dt>
                <dfn>rid</dfn> of type <span class="idlMemberType">DOMString</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for audio.
                  Only [= map/exist =]s if a {{RTCRtpCodingParameters/rid}}
                  has been set for this <a>RTP stream</a>.
                  If {{RTCRtpCodingParameters/rid}} is set this value will be present
                  regardless if the RID RTP header extension has been negotiated.
                </p>
              </dd>
              <dt>
                <dfn>encodingIndex</dfn> of type <span class="idlMemberType">
                unsigned long</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for audio.
                  This is the index of the encoding that represents this
                  <a>RTP stream</a> in the RTP sender's list of
                  {{RTCRtpSendParameters/encodings}}.
                </p>
              </dd>
              <dt>
                <dfn>headerBytesSent</dfn> of type <span class=
                "idlMemberType">unsigned long long</span>
              </dt>
              <dd>
                <p>
                  Total number of RTP header and padding bytes sent for this <a>SSRC</a>. This does not
                  include the size of transport layer headers such as IP or UDP.
                  <code>headerBytesSent + bytesSent</code> equals the number of bytes sent as
                  payload over the transport.
                </p>
              </dd>
              <dt>
                <dfn>retransmittedPacketsSent</dfn> of type <span class=
                "idlMemberType">unsigned long long</span>
              </dt>
              <dd>
                <p>
                  The total number of packets that were retransmitted for this <a>SSRC</a>. This is a
                  subset of {{RTCSentRtpStreamStats/packetsSent}}. If RTX is not negotiated, retransmitted
                  packets are sent over this {{RTCRtpStreamStats/ssrc}}. If RTX was negotiated,
                  retransmitted packets are sent over a separate SSRC but is still accounted for here.
                </p>
              </dd>
              <dt>
                <dfn>retransmittedBytesSent</dfn> of type <span class=
                "idlMemberType">unsigned long long</span>
              </dt>
              <dd>
                <p>
                  The total number of bytes that were retransmitted for this <a>SSRC</a>, only including
                  payload bytes. This is a subset of {{RTCSentRtpStreamStats/bytesSent}}. If RTX is not
                  negotiated, retransmitted bytes are sent over this {{RTCRtpStreamStats/ssrc}}. If RTX
                  was negotiated, retransmitted bytes are sent over a separate SSRC but is still
                  accounted for here.
                </p>
              </dd>
              <dt>
                <dfn>rtxSsrc</dfn> of type <span class=
                "idlMemberType">unsigned long</span>
              </dt>
              <dd>
                <p>
                  If RTX is negotiated for retransmissions on a separate <a>RTP stream</a>, this is the SSRC
                  of the RTX stream that is associated with this stream's {{RTCRtpStreamStats/ssrc}}.
                  If RTX is not negotiated, this value MUST NOT be [= map/exist | present =].
                </p>
              </dd>
              <dt>
                <dfn>targetBitrate</dfn> of type <span class=
                "idlMemberType">double</span>
              </dt>
              <dd>
                <p>
                  Reflects the current encoder target in bits per second. The
                  target is an instantaneous value reflecting the encoder's
                  settings, but the resulting payload bytes sent per second,
                  excluding retransmissions, SHOULD closely correlate to the
                  target. See also {{RTCSentRtpStreamStats/bytesSent}} and
                  {{RTCOutboundRtpStreamStats/retransmittedBytesSent}}. The
                  {{targetBitrate}} is defined in the same way as the Transport
                  Independent Application Specific (TIAS) bitrate [[!RFC3890]].
                </p>
              </dd>
              <dt>
                <dfn>totalEncodedBytesTarget</dfn> of type <span class=
                "idlMemberType">unsigned long long</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for audio.
                  This value is increased by the target frame size in bytes every time a frame has
                  been encoded. The actual frame size may be bigger or smaller than this number.
                  This value goes up every time {{framesEncoded}} goes up.
                </p>
              </dd>
              <dt>
                <dfn>frameWidth</dfn> of type <span class="idlMemberType">unsigned
                long</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for audio.
                  Represents the width of the last encoded frame. The resolution
                  of the encoded frame may be lower than the media source (see {{RTCVideoSourceStats.width}}).
                  Before the first frame is encoded this member MUST NOT [= map/exist =].
                </p>
              </dd>
              <dt>
                <dfn>frameHeight</dfn> of type <span class="idlMemberType">unsigned
                long</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for audio.
                  Represents the height of the last encoded frame. The resolution
                  of the encoded frame may be lower than the media source (see {{RTCVideoSourceStats.height}}).
                  Before the first frame is encoded this member MUST NOT [= map/exist =].
                </p>
              </dd>
              <dt>
                <dfn>framesPerSecond</dfn> of type <span class=
                "idlMemberType">double</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for audio.
                  The number of encoded frames during the last second. This may be
                  lower than the media source frame rate (see {{RTCVideoSourceStats.framesPerSecond}}).
                </p>
              </dd>
              <dt>
                <dfn>framesSent</dfn> of type <span class="idlMemberType">unsigned
                long</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for audio.
                  Represents the total number of frames sent on this <a>RTP stream</a>.
                </p>
              </dd>
              <dt>
                <dfn>hugeFramesSent</dfn> of type <span class="idlMemberType">unsigned
                long</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for audio.
                  Represents the total number of huge frames sent by this RTP
                  stream. Huge frames, by definition, are frames that have an encoded size at least
                  2.5 times the average size of the frames. The average size of the frames is defined
                  as the target bitrate per second divided by the target FPS at the time the frame was
                  encoded. These are usually complex to encode frames with a lot of changes in the
                  picture. This can be used to estimate, e.g slide changes in the streamed presentation.
                </p>
                <p>
                  The multiplier of 2.5 is choosen from analyzing encoded frame sizes for a sample
                  presentation using WebRTC standalone implementation. 2.5 is a reasonably large
                  multiplier which still caused all slide change events to be identified as a huge
                  frames. It, however, produced 1.4% of false positive slide change detections
                  which is deemed reasonable.
                </p>
              </dd>
              <dt>
                <dfn>framesEncoded</dfn> of type <span class=
                "idlMemberType">unsigned long</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for audio.
                  It represents the total number of frames successfully
                  encoded for this RTP media stream.
                </p>
              </dd>
              <dt>
                <dfn>keyFramesEncoded</dfn> of type <span class=
                "idlMemberType">unsigned long</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for audio.
                  It represents the total number of key frames, such as key
                  frames in VP8 [[RFC6386]] or IDR-frames in H.264 [[RFC6184]], successfully
                  encoded for this RTP media stream. This is a subset of
                  {{framesEncoded}}. <code>framesEncoded - keyFramesEncoded</code> gives
                  you the number of delta frames encoded.
                </p>
              </dd>
              <dt>
                <dfn>qpSum</dfn> of type <span class="idlMemberType">unsigned long
                long</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for audio.
                  The sum of the QP values of frames encoded by this sender.
                  The count of frames is in {{framesEncoded}}.
                </p>
                <p>
                  The definition of QP value depends on the codec; for VP8, the QP value is the
                  value carried in the frame header as the syntax element <code class=vp8>y_ac_qi</code>, and defined in
                  [[RFC6386]] section 19.2. Its range is 0..127.
                  <!-- Need appropriate references for VP9 and H.264 -->
                </p>
                <p>
                  Note that the QP value is only an indication of quantizer values used; many
                  formats have ways to vary the quantizer value within the frame.
                </p>
              </dd>
              <dt>
                <dfn>psnrSum</dfn> of type <span class="idlMemberType">
                record&lt;DOMString, double&gt;</span>
              </dt>
              <dd>
                <p class="fingerprint">
                  MUST NOT [= map/exist =] unless [= exposing hardware is allowed =].
                </p>
                <p>
                  MUST NOT [= map/exist =] for audio.
                  The cumulative sum of the PSNR values of frames encoded by this sender.
                  The record includes values for the "y", "u" and "v" components.
                  The count of measurements is in {{psnrMeasurements}}.
                </p>
                <p>
                  PSNR is defined in [[ISO-29170-1:2017]].
                </p>
                <p class="note">
		  PSNR metrics are intended for statistical analysis rather
		  than representing absolute truth on a per-frame basis.
                </p>
              </dd>
              <dt>
                <dfn>psnrMeasurements</dfn> of type <span class="idlMemberType">unsigned long long
                </span>
              </dt>
              <dd>
                <p class="fingerprint">
                  MUST NOT [= map/exist =] unless [= exposing hardware is allowed =].
                </p>
                <p>
                  MUST NOT [= map/exist =] for audio.
                  The number of times PSNR was measured. The components of {{psnrSum}} are
                  aggregated with this measurement.
                </p>
                <p>
                  The PSNR is defined in [[ISO-29170-1:2017]].
                  The frequency of PSNR measurements is [=implementation-defined=].
                </p>
                <p class="note">
                  User agents are encouraged to measure PSNR at a fixed frequency
                  for each encoder implementation, and as frequently as possible as
                  long as it does not introduce a noticeable performance penalty.
                </p>
              </dd>
              <dt>
                <dfn>totalEncodeTime</dfn> of type <span class=
                "idlMemberType">double</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for audio.
                  Total number of seconds that has been spent encoding the {{framesEncoded}}
                  frames of this stream. The average encode time can be calculated by dividing this
                  value with {{framesEncoded}}. The time it takes to encode one frame is the
                  time passed between feeding the encoder a frame and the encoder returning encoded
                  data for that frame. This does not include any additional time it may take to
                  packetize the resulting data.
                </p>
              </dd>
              <dt>
                <dfn>totalPacketSendDelay</dfn> of type <span class=
                "idlMemberType">double</span>
              </dt>
              <dd>
                <p>
                  The total number of seconds that packets have spent buffered locally before being
                  transmitted onto the network. The time is measured from when a packet is emitted
                  from the RTP packetizer until it is handed over to the OS network socket. This
                  measurement is added to {{totalPacketSendDelay}} when
                  {{RTCSentRtpStreamStats/packetsSent}} is incremented.
                </p>
              </dd>
              <dt>
                <dfn>qualityLimitationReason</dfn> of type <span class=
                "idlMemberType">{{RTCQualityLimitationReason}}</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for audio.
                  The current reason for limiting the resolution and/or
                  framerate, or {{RTCQualityLimitationReason/"none"}} if not limited.
                </p>
                <p>
                  The implementation reports the most limiting factor. If the
                  implementation is not able to determine the most limiting
                  factor because multiple may exist, the reasons MUST be
                  reported in the following order of priority: "bandwidth",
                  "cpu", "other".
                </p>
                <p class="note">
                  The consumption of CPU and bandwidth resources is
                  interdependent and difficult to estimate, making it hard to
                  determine what the "most limiting factor" is. The priority
                  order promoted here is based on the heuristic that "bandwidth"
                  is generally more varying and thus a more likely and more
                  useful signal than "cpu".
                </p>
              </dd>
              <dt>
                <dfn>qualityLimitationDurations</dfn> of type <span class=
                "idlMemberType">record&lt;DOMString, double&gt;</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for audio.
                  A record of the total time, in seconds, that this stream
                  has spent in each quality limitation state. The record includes a mapping for all
                  {{RTCQualityLimitationReason}} types, including {{RTCQualityLimitationReason/"none"}}.
                </p>
                <p>
                  The sum of all entries minus {{qualityLimitationDurations}}[{{RTCQualityLimitationReason/"none"}}]
                  gives the total time that the stream has been limited.
                </p>
              </dd>
              <dt>
                <dfn>qualityLimitationResolutionChanges</dfn> of type <span class=
                "idlMemberType">unsigned long</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for audio.
                  The number of times that the resolution has changed because
                  we are quality limited ({{qualityLimitationReason}} has a value other than
                  {{RTCQualityLimitationReason/"none"}}). The counter is initially zero and increases when the
                  resolution goes up or down. For example, if a 720p track is sent as 480p for some
                  time and then recovers to 720p, {{qualityLimitationResolutionChanges}}
                  will have the value 2.
                </p>
              </dd>
              <dt>
                <dfn>nackCount</dfn> of type <span class="idlMemberType">unsigned
                long</span>
              </dt>
              <dd>
                <p>
                  Count the total number of Negative ACKnowledgement (NACK) packets, as defined in [[!RFC4585]]
                  section 6.2.1, received by this sender.
                </p>
              </dd>
              <dt>
                <dfn>firCount</dfn> of type <span class="idlMemberType">unsigned
                long</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for audio.
                  Count the total number of Full Intra Request (FIR) packets,
                  as defined in [[!RFC5104]] section 4.3.1, received by this sender. Does not count the RTCP FIR
                  indicated in [[?RFC2032]] which was deprecated by [[?RFC4587]].
                </p>
              </dd>
              <dt>
                <dfn>pliCount</dfn> of type <span class="idlMemberType">unsigned
                long</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for audio.
                  Count the total number of Picture Loss Indication (PLI)
                  packets, as defined in [[!RFC4585]] section 6.3.1, received by this sender
                </p>
              </dd>
              <dt>
                <dfn>encoderImplementation</dfn> of type <span class=
                "idlMemberType">DOMString</span>
              </dt>
              <dd>
                <p class="fingerprint">
                  MUST NOT [= map/exist =] unless [= exposing hardware is allowed =].
                </p>
                <p>
                  MUST NOT [= map/exist =] for audio.
                  Identifies the encoder implementation used.
                  This is useful for diagnosing interoperability issues.
                </p>
              </dd>
              <dt>
                <dfn>powerEfficientEncoder</dfn> of type <span class=
                "idlMemberType">boolean</span>
              </dt>
              <dd>
                <p class="fingerprint">
                  MUST NOT [= map/exist =] unless [= exposing hardware is allowed =].
                </p>
                <p>
                  MUST NOT [= map/exist =] for audio.
                  Whether the encoder
                  currently used is considered power efficient by the user agent.
                  This SHOULD reflect if the configuration results in hardware acceleration,
                  but the user agent MAY take other information into account when deciding if
                  the configuration is considered power efficient.
                </p>
              </dd>
              <dt>
                <dfn>active</dfn> of type <span class=
                "idlMemberType">boolean</span>
              </dt>
              <dd>
                <p>
                  Indicates whether this <a>RTP stream</a> is configured to be sent or disabled.
                  Note that an active stream can still not be sending, e.g. when being limited by
                  network conditions.
                </p>
              </dd>
              <dt>
                <dfn>scalabilityMode</dfn> of type <span class=
                "idlMemberType">DOMString</span>
              </dt>
              <dd>
                <p>
                  MUST NOT [= map/exist =] for audio.
                  Only [= map/exist =]s when a
                  <a href="https://w3c.github.io/webrtc-svc/#scalabilitymodes*">
                  scalability mode</a> is currently configured for this <a>RTP stream</a>.
                </p>
              </dd>
              <dt>
                <dfn>packetsSentWithEct1</dfn> of type <span class="idlMemberType">unsigned long long</span>
              </dt>
              <dd>
                Total number of RTP packets sent for this <a>SSRC</a> with the ECT(1) marking defined in [[RFC3168]]
                section 5 and used by the L4S protocol described in [[RFC9331]].
              </dd>
            </dl>
          </section>
        </div>
      </section>
      <section>
        <h3>
          <dfn>RTCQualityLimitationReason</dfn> enum
        </h3>
        <div>
          <pre class="idl">enum RTCQualityLimitationReason {
            "none",
            "cpu",
            "bandwidth",
            "other",
          };</pre>
          <table data-link-for="RTCQualityLimitationReason" data-dfn-for=
		 "RTCQualityLimitationReason" class="simple">
	          <caption>{{RTCQualityLimitationReason}} Enumeration description</caption>
            <thead>
              <tr>
                <th>Enum value</th><th>Description</th>
              </tr>
            </thead>
            <tbody>
              <tr>
                <td>
                  <dfn>none</dfn>
                </td>
                <td>
                  <p>
                    The resolution and/or framerate is not limited.
                  </p>
                </td>
              </tr>
              <tr>
                <td>
                  <dfn>cpu</dfn>
                </td>
                <td>
                  <p>
                    The resolution and/or framerate is primarily limited due to CPU load.
                  </p>
                </td>
              </tr>
              <tr>
                <td>
                  <dfn>bandwidth</dfn>
                </td>
                <td>
                  <p>
                    The resolution and/or framerate is primarily limited due to congestion cues
                    during bandwidth estimation. Typical, congestion control algorithms use
                    inter-arrival time, round-trip time, packet or other congestion cues to perform
                    bandwidth estimation.
                  </p>
                </td>
              </tr>
              <tr>
                <td>
                  <dfn>other</dfn>
                </td>
                <td>
                  <p>
                    The resolution and/or framerate is primarily limited for a reason other than
                    the above.
                  </p>
                </td>
              </tr>
            </tbody>
          </table>
        </div>
      </section>
      <section id="remoteoutboundrtpstats-dict*">
        <h3>
          {{RTCRemoteOutboundRtpStreamStats}} dictionary
        </h3>
        <p>
          The <dfn>RTCRemoteOutboundRtpStreamStats</dfn> dictionary represents the remote
          endpoint's measurement metrics for its outgoing <a>RTP stream</a> (corresponding to an outgoing
          <a>RTP stream</a> at the sending endpoint). The timestamp reported in the statistics object is
          the time at which the corresponding <a>RTCP SR</a> was received.
        </p>
        <div>
          <pre class="idl">dictionary RTCRemoteOutboundRtpStreamStats : RTCSentRtpStreamStats {
             DOMString           localId;
             DOMHighResTimeStamp remoteTimestamp;
             unsigned long long  reportsSent;
             double              roundTripTime;
             double              totalRoundTripTime;
             unsigned long long  roundTripTimeMeasurements;
};</pre>
          <section>
            <h2>
              Dictionary {{RTCRemoteOutboundRtpStreamStats}} Members
            </h2>
            <dl data-link-for="RTCRemoteOutboundRtpStreamStats" data-dfn-for=
            "RTCRemoteOutboundRtpStreamStats" class="dictionary-members">
              <dt>
                <dfn>localId</dfn> of type <span class=
                "idlMemberType">DOMString</span>
              </dt>
              <dd>
                <p>
                  The {{localId}} is used for looking up the local
                  {{RTCInboundRtpStreamStats}} object for the same <a>SSRC</a>.
                </p>
              </dd>
              <dt>
                <dfn>remoteTimestamp</dfn> of type <span class=
                "idlMemberType">DOMHighResTimeStamp</span>
              </dt>
              <dd>
                <p>
                  {{remoteTimestamp}}, of type {{DOMHighResTimeStamp}}
                  [[!HIGHRES-TIME]], represents the remote timestamp at which these statistics were
                  sent by the remote endpoint. This differs from {{RTCStats/timestamp}}, which
                  represents the time at which the statistics were generated or received by the
                  local endpoint. The {{remoteTimestamp}}, if present, is derived from the
                  NTP timestamp in an <a>RTCP Sender Report</a> (SR) block, which reflects the remote
                  endpoint's clock. That clock may not be synchronized with the local clock.
                </p>
              </dd>
              <dt>
                <dfn>reportsSent</dfn> of type <span class=
                "idlMemberType">unsigned long long</span>
              </dt>
              <dd>
                <p>
                  Represents the total number of <a>RTCP Sender Report</a> (SR) blocks sent for this <a>SSRC</a>.
                </p>
              </dd>
              <dt>
                <dfn>roundTripTime</dfn> of type <span class=
                "idlMemberType">double</span>
              </dt>
              <dd>
                <p>
                  Estimated round trip time for this <a>SSRC</a> based on the latest <a>RTCP Sender Report</a> (SR)
                  that contains a DLRR report block as defined in [[!RFC3611]]. The Calculation of
                  the round trip time is defined in section 4.5. of [[!RFC3611]]. MUST NOT [= map/exist =] if the
                  latest SR does not contain the DLRR report block, or if the last RR timestamp in the DLRR report
                  block is zero, or if the delay since last RR value in the DLRR report block is zero.
                </p>
              </dd>
              <dt>
                <dfn>totalRoundTripTime</dfn> of type <span class=
                "idlMemberType">double</span>
              </dt>
              <dd>
                <p>
                  Represents the cumulative sum of all round trip time measurements in seconds since the
                  beginning of the session. The individual round trip time is calculated based on the
                  DLRR report block in the <a>RTCP Sender Report</a> (SR) [[!RFC3611]].
                  This counter will not increment if the {{roundTripTime}} can not be calculated.
                  The average round trip time can be computed from {{totalRoundTripTime}} by dividing it by {{roundTripTimeMeasurements}}.
                </p>
              </dd>
              <dt>
                <dfn>roundTripTimeMeasurements</dfn> of type <span class=
                "idlMemberType">unsigned long long</span>
              </dt>
              <dd>
                <p>
                  Represents the total number of <a>RTCP Sender Report</a> (SR) blocks received for this
                  <a>SSRC</a> that contain a DLRR report block that can derive a valid round trip time
                  according to [[!RFC3611]].
                  This counter will not increment if the {{roundTripTime}} can not be calculated.
                </p>
              </dd>
            </dl>
          </section>
        </div>
      </section>
      <section id="mediasourcestats-dict*">
        <h3>
          {{RTCMediaSourceStats}} dictionary
        </h3>
        <p>
          The <dfn>RTCMediaSourceStats</dfn> dictionary represents a track that is currently
          attached to one or more senders. It contains information about media sources such as
          frame rate and resolution prior to encoding. This is the media passed from the
          {{MediaStreamTrack}} to the {{RTCRtpSender}}s. This is in contrast to
          {{RTCOutboundRtpStreamStats}} whose members describe metrics as measured after
          the encoding step. For example, a track may be captured from a high-resolution camera,
          its frames downscaled due to track constraints and then further downscaled by the
          encoders due to CPU and network conditions. This dictionary reflects the video frames or
          <a>audio sample</a>s passed out from the track - after track constraints have been applied but
          before any encoding or further downsampling occurs.
        </p>
        <p>
          Media source objects are of either subdictionary {{RTCAudioSourceStats}} or
          {{RTCVideoSourceStats}}. The {{RTCStats/type}} is the same
          ({{RTCStatsType/"media-source"}}) but {{RTCMediaSourceStats/kind}} is different (<code class=gum>"audio"</code> or
          <code class=gum>"video"</code>) depending on the kind of track.
        </p>
        <p>
          The media source stats objects are created when a track is attached to any
          {{RTCRtpSender}} and may subsequently be attached to multiple senders during its
          life. The life of this object ends when the track is no longer attached to any sender of
          the same {{RTCPeerConnection}}. If a track whose media source object ended is
          attached again this results in a new media source stats object whose counters (such as
          number of frames) are reset.
        </p>
        <div>
          <pre class="idl">dictionary RTCMediaSourceStats : RTCStats {
             required DOMString       trackIdentifier;
             required DOMString       kind;
};</pre>
          <section>
            <h2>
              Dictionary {{RTCMediaSourceStats}} Members
            </h2>
            <dl data-link-for="RTCMediaSourceStats" data-dfn-for="RTCMediaSourceStats" class=
            "dictionary-members">
              <dt>
                <dfn>trackIdentifier</dfn> of type <span class=
                "idlMemberType">DOMString</span>
              </dt>
              <dd>
                <p>
                  The value of the {{MediaStreamTrack}}'s <code class=gum>id</code> attribute.
                </p>
              </dd>
              <dt>
                <dfn>kind</dfn> of type <span class="idlMemberType">DOMString</span>
              </dt>
              <dd>
                <p>
                  The value of the {{MediaStreamTrack}}'s <code class=gum>kind</code> attribute.
                  This is either <code class=gum>"audio"</code> or <code class=gum>"video"</code>. If it is
                  <code class=gum>"audio"</code> then this stats object is of type
                  {{RTCAudioSourceStats}}. If it is <code class=gum>"video"</code> then this stats
                  object is of type {{RTCVideoSourceStats}}.
                </p>
              </dd>
            </dl>
          </section>
        </div>
      </section>
      <section id="audiosourcestats-dict*">
        <h3>
          {{RTCAudioSourceStats}} dictionary
        </h3>
        <p>
          The <dfn>RTCAudioSourceStats</dfn> dictionary represents an audio track that is attached
          to one or more senders. It is an {{RTCMediaSourceStats}} whose
          {{RTCMediaSourceStats/kind}} is <code class=gum>"audio"</code>.
        </p>
        <div>
          <pre class="idl">dictionary RTCAudioSourceStats : RTCMediaSourceStats {
              double              audioLevel;
              double              totalAudioEnergy;
              double              totalSamplesDuration;
              double              echoReturnLoss;
              double              echoReturnLossEnhancement;
};</pre>
          <section>
            <h2>
              Dictionary {{RTCAudioSourceStats}} Members
            </h2>
            <dl data-link-for="RTCAudioSourceStats" data-dfn-for="RTCAudioSourceStats" class=
            "dictionary-members">
              <dt>
                <dfn>audioLevel</dfn> of type <span class=
                "idlMemberType">double</span>
              </dt>
              <dd>
                <p>
                  Represents the audio level of the media source. For audio levels of remotely
                  sourced tracks, see {{RTCInboundRtpStreamStats}} instead.
                </p>
                <p>
                  The value is between 0..1 (linear), where 1.0 represents 0 dBov, 0 represents
                  silence, and 0.5 represents approximately 6 dBSPL change in the sound pressure
                  level from 0 dBov.
                </p>
                <p>
                  The {{audioLevel}} is averaged over some small interval, using the algorithm
                  described under {{totalAudioEnergy}}. The interval used is [=implementation-defined=].
                </p>
              </dd>
              <dt>
                <dfn>totalAudioEnergy</dfn> of type <span class=
                "idlMemberType">double</span>
              </dt>
              <dd>
                <p>
                  Represents the audio energy of the media source. For audio energy of remotely
                  sourced tracks, see {{RTCInboundRtpStreamStats}} instead.
                </p>
                <p>
                  This value MUST be computed as follows: for each <a>audio sample</a> produced by the
                  media source during the lifetime of this stats object, add the sample's value
                  divided by the highest-intensity encodable value, squared and then multiplied by
                  the duration of the sample in seconds. In other words, <code>duration *
                  Math.pow(energy/maxEnergy, 2)</code>.
                </p>
                <p>
                  This can be used to obtain a root mean square (RMS) value that uses the same
                  units as {{audioLevel}}, as defined in [[RFC6464]]. It can be
                  converted to these units using the formula
                  <code>Math.sqrt(totalAudioEnergy/totalSamplesDuration)</code>. This calculation
                  can also be performed using the differences between the values of two different
                  {{RTCPeerConnection/getStats()}} calls, in order to compute the average audio level over
                  any desired time interval. In other words, do <code>Math.sqrt((energy2 -
                  energy1)/(duration2 - duration1))</code>.
                </p>
                <p>
                  For example, if a 10ms packet of audio is produced with an RMS of 0.5 (out of
                  1.0), this should add <code>0.5 * 0.5 * 0.01 = 0.0025</code> to
                  {{totalAudioEnergy}}. If another 10ms packet with an RMS of 0.1 is
                  received, this should similarly add <code>0.0001</code> to
                  {{totalAudioEnergy}}. Then,
                  <code>Math.sqrt(totalAudioEnergy/totalSamplesDuration)</code> becomes
                  <code>Math.sqrt(0.0026/0.02) = 0.36</code>, which is the same value that would be
                  obtained by doing an RMS calculation over the contiguous 20ms segment of audio.
                </p>
                <p>
                  If multiple audio channels are used, the
                  audio energy of a sample refers to the <strong>highest energy</strong> of any
                  channel.
                </p>
              </dd>
              <dt>
                <dfn>totalSamplesDuration</dfn> of type <span class=
                "idlMemberType">double</span>
              </dt>
              <dd>
                <p>
                  Represents the audio duration of the media source. For audio durations of
                  remotely sourced tracks, see {{RTCInboundRtpStreamStats}} instead.
                </p>
                <p>
                  Represents the total duration in seconds of all samples that have been produced
                  by this source for the lifetime of this stats object. Can be used with
                  {{totalAudioEnergy}} to compute an average audio level over
                  different intervals.
                </p>
              </dd>
              <dt>
                <dfn>echoReturnLoss</dfn> of type <span class=
                "idlMemberType">double</span>
              </dt>
              <dd>
                <p>
                  Only [= map/exist =]s when the {{MediaStreamTrack}} is sourced from a microphone where
                  echo cancellation is applied. Calculated in decibels, as defined in [[!ECHO]]
                  (2012) section 3.14.
                </p>
                <p>
                  If multiple audio channels are used, the channel of the <strong>least audio
                  energy</strong> is considered for any sample.
                </p>
              </dd>
              <dt>
                <dfn>echoReturnLossEnhancement</dfn> of type <span class=
                "idlMemberType">double</span>
              </dt>
              <dd>
                <p>
                  Only [= map/exist =]s when the {{MediaStreamTrack}} is sourced from a microphone where
                  echo cancellation is applied. Calculated in decibels, as defined in [[!ECHO]]
                  (2012) section 3.15.
                </p>
                <p>
                  If multiple audio channels are used, the channel of the
                  <strong>least audio energy</strong> is considered for any sample.
                </p>
              </dd>
            </dl>
          </section>
        </div>
      </section>
      <section id="videosourcestats-dict*">
        <h3>
          {{RTCVideoSourceStats}} dictionary
        </h3>
        <p>
          The <dfn>RTCVideoSourceStats</dfn> dictionary represents a video track that is attached
          to one or more senders. It is an {{RTCMediaSourceStats}} whose
          {{RTCMediaSourceStats/kind}} is <code class=gum>"video"</code>.
        </p>
        <div>
          <pre class="idl">dictionary RTCVideoSourceStats : RTCMediaSourceStats {
             unsigned long   width;
             unsigned long   height;
             unsigned long   frames;
             double          framesPerSecond;
};</pre>
          <section>
            <h2>
              Dictionary {{RTCVideoSourceStats}} Members
            </h2>
            <dl data-link-for="RTCVideoSourceStats" data-dfn-for="RTCVideoSourceStats" class=
            "dictionary-members">
              <dt>
                <dfn>width</dfn> of type <span class="idlMemberType">unsigned
                long</span>
              </dt>
              <dd>
                <p>
                  The width, in pixels, of the last frame originating from this source. Before a
                  frame has been produced this member MUST NOT [= map/exist =].
                </p>
              </dd>
              <dt>
                <dfn>height</dfn> of type <span class="idlMemberType">unsigned
                long</span>
              </dt>
              <dd>
                <p>
                  The height, in pixels, of the last frame originating from this source. Before a
                  frame has been produced this member MUST NOT [= map/exist =].
                </p>
              </dd>
              <dt>
                <dfn>frames</dfn> of type <span class="idlMemberType">unsigned long</span>
              </dt>
              <dd>
                <p>
                  The total number of frames originating from this source.
                </p>
              </dd>
              <dt>
                <dfn>framesPerSecond</dfn> of type <span class=
                "idlMemberType">double</span>
              </dt>
              <dd>
                <p>
                  The number of frames originating from this source, measured during the last
                  second. For the first second of this object's lifetime this member MUST NOT [= map/exist =].
                </p>
              </dd>
            </dl>
          </section>
        </div>
      </section>

      <section id="playoutstats-dict*">
        <h3>
          {{RTCAudioPlayoutStats}} dictionary
        </h3>
        <p>
          Only applicable if the playout path represents an audio device.
          Represents one playout path - if the same playout stats object is
          referenced by multiple {{RTCInboundRtpStreamStats}} this is an
          indication that audio mixing is happening in which case sample
          counters in this stats object refer to the samples after mixing.
        </p>
        <div>
          <pre class="idl">dictionary RTCAudioPlayoutStats : RTCStats {
             required DOMString kind;
             double             synthesizedSamplesDuration;
             unsigned long      synthesizedSamplesEvents;
             double             totalSamplesDuration;
             double             totalPlayoutDelay;
             unsigned long long totalSamplesCount;
};</pre>
          <p class="note">
            The {{RTCAudioPlayoutStats}} dictionary and all of its metrics are
            features at risk due to lack of consensus.
          </p>
          <section>
            <h2>
              Dictionary {{RTCAudioPlayoutStats}} Members
            </h2>
            <dl data-link-for="RTCAudioPlayoutStats" data-dfn-for="RTCAudioPlayoutStats" class=
            "dictionary-members">
              <dt>
                <dfn>kind</dfn> of type <span class=
                "idlMemberType">DOMString</span>
              </dt>
              <dd>
                <p>
                  For audio playout, this has the value
                  "<code class=gum>audio</code>". This reflects the
                  <code class=gum>kind</code> attribute
                  {{MediaStreamTrack}}(s) being played out.
                </p>
              </dd>
              <dt>
                <dfn>synthesizedSamplesDuration</dfn> of type <span class=
                "idlMemberType">double</span>
              </dt>
              <dd>
                <p>
                  If the playout path is unable to produce audio samples on time
                  for device playout, samples are synthesized to be playout out
                  instead. {{synthesizedSamplesDuration}} is measured in seconds
                  and is incremented each time an audio sample is synthesized by
                  this playout path. This metric can be used together with
                  {{totalSamplesDuration}} to calculate the percentage of played
                  out media being synthesized.
                </p>
                <p>
                  Synthesization typically only happens if the pipeline is
                  underperforming. Samples synthesized by the
                  {{RTCInboundRtpStreamStats}} are not counted for here, but in
                  {{RTCInboundRtpStreamStats}}.{{RTCInboundRtpStreamStats/concealedSamples}}.
                </p>
              </dd>
              <dt>
                <dfn>synthesizedSamplesEvents</dfn> of type <span class=
                "idlMemberType">unsigned long</span>
              </dt>
              <dd>
                <p>
                  The number of synthesized samples events. This counter
                  increases every time a sample is synthesized after a
                  non-synthesized sample. That is, multiple consecutive
                  synthesized samples will increase
                  {{synthesizedSamplesDuration}} multiple times but is a single
                  synthesization samples event.
                </p>
              </dd>
              <dt>
                <dfn>totalSamplesDuration</dfn> of type <span class=
                "idlMemberType">double</span>
              </dt>
              <dd>
                <p>
                  The total duration, in seconds, of all audio samples that have
                  been playout. Includes both synthesized and non-synthesized
                  samples.
                </p>
              </dd>
              <dt>
                <dfn>totalPlayoutDelay</dfn> of type <span class=
                "idlMemberType">double</span>
              </dt>
              <dd>
                <p>
                  When audio samples are pulled by the playout device, this
                  counter is incremented with the estimated delay of the playout
                  path for that audio sample. The playout delay includes the
                  delay from being emitted to the actual time of playout on the
                  device. This metric can be used together with
                  {{totalSamplesCount}} to calculate the average playout delay
                  per sample.
                </p>
              </dd>
              <dt>
                <dfn>totalSamplesCount</dfn> of type <span class=
                "idlMemberType">unsigned long long</span>
              </dt>
              <dd>
                <p>
                  When audio samples are pulled by the playout device, this
                  counter is incremented with the number of samples emitted for
                  playout.
                </p>
              </dd>
            </dl>
          </section>
        </div>
      </section>

<section id="pcstats-dict*">
        <h3>
          <dfn>RTCPeerConnectionStats</dfn> dictionary
        </h3>
        <div>
          <pre class="idl">dictionary RTCPeerConnectionStats : RTCStats {
            unsigned long dataChannelsOpened;
            unsigned long dataChannelsClosed;
};</pre>
          <section>
            <h2>
              Dictionary {{RTCPeerConnectionStats}} Members
            </h2>
            <dl data-link-for="RTCPeerConnectionStats" data-dfn-for="RTCPeerConnectionStats" class=
            "dictionary-members">
              <dt>
                <dfn>dataChannelsOpened</dfn> of type <span class=
                "idlMemberType">unsigned long</span>
              </dt>
              <dd>
                <p>
                  Represents the number of unique {{RTCDataChannel}}s that have entered the {{RTCDataChannelState/"open"}} state
                  during their lifetime.
                </p>
              </dd>
              <dt>
                <dfn>dataChannelsClosed</dfn> of type <span class=
                "idlMemberType">unsigned long</span>
              </dt>
              <dd>
                <p>
                  Represents the number of unique {{RTCDataChannel}}s that have left the {{RTCDataChannelState/"open"}} state
                  during their lifetime (due to being closed by either end or the underlying
                  transport being closed). {{RTCDataChannel}}s that transition from {{RTCDataChannelState/"connecting"}} to
                  {{RTCDataChannelState/"closing"}} or {{RTCDataChannelState/"closed"}} without ever being {{RTCDataChannelState/"open"}} are not counted in this number.
                </p>
              </dd>
            </dl>
            <p>
              The total number of open data channels at any time can be calculated as
              {{RTCPeerConnectionStats/dataChannelsOpened}} - {{RTCPeerConnectionStats/dataChannelsClosed}}. This number is always positive.
            </p>
          </section>
        </div>
      </section>
      <section id="dcstats-dict*">
        <h3>
          <dfn>RTCDataChannelStats</dfn> dictionary
        </h3>
        <div>
          <pre class="idl">dictionary RTCDataChannelStats : RTCStats {
             DOMString           label;
             DOMString           protocol;
             unsigned short      dataChannelIdentifier;
             required RTCDataChannelState state;
             unsigned long       messagesSent;
             unsigned long long  bytesSent;
             unsigned long       messagesReceived;
             unsigned long long  bytesReceived;
};</pre>
          <section>
            <h2>
              Dictionary {{RTCDataChannelStats}} Members
            </h2>
            <dl data-link-for="RTCDataChannelStats" data-dfn-for="RTCDataChannelStats" class=
            "dictionary-members">
              <dt>
                <dfn>label</dfn> of type <span class="idlMemberType">DOMString</span>
              </dt>
              <dd>
                The {{RTCDataChannel/label}} value of the {{RTCDataChannel}} object.
              </dd>
              <dt>
                <dfn>protocol</dfn> of type <span class=
                "idlMemberType">DOMString</span>
              </dt>
              <dd>
                The {{RTCDataChannel/protocol}} value of the {{RTCDataChannel}} object.
              </dd>
              <dt>
                <dfn>dataChannelIdentifier</dfn> of type <span class=
                "idlMemberType">unsigned short</span>
              </dt>
              <dd>
                <p>
                  The {{RTCDataChannel/id}} attribute of the {{RTCDataChannel}} object.
                </p>
              </dd>
              <dt>
                <dfn>state</dfn> of type {{RTCDataChannelState}}
              </dt>
              <dd>
                The {{RTCDataChannel/readyState}} value of the {{RTCDataChannel}} object.
              </dd>
              <dt>
                <dfn>messagesSent</dfn> of type <span class="idlMemberType">unsigned
                long</span>
              </dt>
              <dd>
                <p>
                  Represents the total number of API "message" events sent.
                </p>
              </dd>
              <dt>
                <dfn>bytesSent</dfn> of type <span class="idlMemberType">unsigned long
                long</span>
              </dt>
              <dd>
                <p>
                  Represents the total number of payload bytes sent on this
                  {{RTCDataChannel}}.
                </p>
              </dd>
              <dt>
                <dfn>messagesReceived</dfn> of type <span class=
                "idlMemberType">unsigned long</span>
              </dt>
              <dd>
                <p>
                  Represents the total number of API "message" events received.
                </p>
              </dd>
              <dt>
                <dfn>bytesReceived</dfn> of type <span class="idlMemberType">unsigned
                long long</span>
              </dt>
              <dd>
                <p>
                  Represents the total number of payload bytes received on this
                  {{RTCDataChannel}}.
                </p>
              </dd>
            </dl>
          </section>
        </div>
      </section>
      <section id="transportstats-dict*">
        <h3>
          <dfn>RTCTransportStats</dfn> dictionary
        </h3>
        <p>
          An {{RTCTransportStats}} object represents the stats corresponding to an
          {{RTCDtlsTransport}} and its underlying
          {{RTCIceTransport}}. When bundling is used, a single
          transport will be used for all {{MediaStreamTrack}}s in the bundle group.
          If bundling is not used, different {{MediaStreamTrack}} will use
          different transports. Bundling is described in [[!WEBRTC]].
        </p>
        <div>
          <pre class="idl">dictionary RTCTransportStats : RTCStats {
             unsigned long long    packetsSent;
             unsigned long long    packetsReceived;
             unsigned long long    bytesSent;
             unsigned long long    bytesReceived;
             RTCIceRole            iceRole;
             DOMString             iceLocalUsernameFragment;
             required RTCDtlsTransportState dtlsState;
             RTCIceTransportState  iceState;
             DOMString             selectedCandidatePairId;
             DOMString             localCertificateId;
             DOMString             remoteCertificateId;
             DOMString             tlsVersion;
             DOMString             dtlsCipher;
             RTCDtlsRole           dtlsRole;
             DOMString             srtpCipher;
             unsigned long         selectedCandidatePairChanges;
             unsigned long         ccfbMessagesSent;
	     unsigned long         ccfbMessagesReceived;
};</pre>
          <section>
            <h2>
              Dictionary {{RTCTransportStats}} Members
            </h2>
            <dl data-link-for="RTCTransportStats" data-dfn-for="RTCTransportStats" class=
            "dictionary-members">
              <dt>
                <dfn>packetsSent</dfn> of type <span class="idlMemberType">unsigned
                long long</span>
              </dt>
              <dd>
                <p>
                  Represents the total number of packets sent over this transport.
                </p>
              </dd>
              <dt>
                <dfn>packetsReceived</dfn> of type <span class=
                "idlMemberType">unsigned long long</span>
              </dt>
              <dd>
                <p>
                  Represents the total number of packets received on this transport.
                </p>
              </dd>
              <dt>
                <dfn>bytesSent</dfn> of type <span class="idlMemberType">unsigned long
                long</span>
              </dt>
              <dd>
                <p>
                  Represents the total number of payload bytes sent on this
                  {{RTCIceTransport}}, i.e., not including headers, padding
                  or ICE connectivity checks.
                </p>
              </dd>
              <dt>
                <dfn>bytesReceived</dfn> of type <span class="idlMemberType">unsigned
                long long</span>
              </dt>
              <dd>
                <p>
                  Represents the total number of payload bytes received on this
                  {{RTCIceTransport}}, i.e., not including headers, padding
                  or ICE connectivity checks.
                </p>
              </dd>
              <dt>
                <dfn>iceRole</dfn> of type <span class=
                "idlMemberType">{{RTCIceRole}}</span>
              </dt>
              <dd>
                <p>
                  Set to the current value of the {{RTCIceTransport/role}} attribute of the underlying
                  {{RTCDtlsTransport}}.{{RTCDtlsTransport/iceTransport}}.
                </p>
              </dd>
              <dt>
                <dfn>iceLocalUsernameFragment</dfn> of type <span
                  class="idlMemberType">DOMString</span>
              </dt>
              <dd>
                <p>
                  Set to the current value of the local username fragment
                  used in message validation procedures [[RFC5245]]
                  for this {{RTCIceTransport}}. It may be
                  updated on setLocalDescription() and on ICE restart.
                </p>
              </dd>
              <dt>
                <dfn>dtlsState</dfn> of type <span class=
                "idlMemberType">{{RTCDtlsTransportState}}</span>
              </dt>
              <dd>
                <p>
                  Set to the current value of the {{RTCDtlsTransport/state}} attribute of the underlying
                  {{RTCDtlsTransport}}.
                </p>
              </dd>
              <dt>
                <dfn>iceState</dfn> of type <span class="idlMemberType">{{RTCIceTransportState}}</span>
              </dt>
              <dd>
                <p>
                  Set to the current value of the {{RTCIceTransport/state}}
                  attribute of the underlying {{RTCIceTransport}}.
                </p>
              </dd>
              <dt>
                <dfn>selectedCandidatePairId</dfn> of type <span class=
                "idlMemberType">DOMString</span>
              </dt>
              <dd>
                <p>
                  It is a unique identifier that is associated to the object that was inspected to
                  produce the {{RTCIceCandidatePairStats}} associated with this transport.
                </p>
              </dd>
              <dt>
                <dfn>localCertificateId</dfn> of type <span class=
                "idlMemberType">DOMString</span>
              </dt>
              <dd>
                <p>
                  For components where DTLS is negotiated, give local certificate.
                </p>
              </dd>
              <dt>
                <dfn>remoteCertificateId</dfn> of type <span class=
                "idlMemberType">DOMString</span>
              </dt>
              <dd>
                <p>
                  For components where DTLS is negotiated, give remote certificate.
                </p>
              </dd>
              <dt>
                <dfn>tlsVersion</dfn> of type <span class=
                "idlMemberType">DOMString</span>
              </dt>
              <dd>
                <p>
                  For components where DTLS is negotiated, the TLS version agreed. Only [= map/exist =]s
                  after DTLS negotiation is complete.
                </p>
                <p>
                  The value comes from <code>ServerHello.supported_versions</code> if present, otherwise from
                  <code>ServerHello.version</code>. It is represented as four upper case
                  hexadecimal digits, representing the two
                  bytes of the version.
                </p>
              </dd>
              <dt>
                <dfn>dtlsCipher</dfn> of type <span class=
                "idlMemberType">DOMString</span>
              </dt>
              <dd>
                <p>
                  Descriptive name of the cipher suite used for the DTLS transport, as defined in
                  the "Description" column of the IANA cipher suite registry [[!IANA-TLS-CIPHERS]].
                </p>
              </dd>
              <dt>
                <dfn>dtlsRole</dfn> of type <span class=
                "idlMemberType">RTCDtlsRole</span>
              </dt>
              <dd>
                <p>
                  {{RTCDtlsRole/"client"}} or {{RTCDtlsRole/"server"}} depending on the DTLS role.
                  {{RTCDtlsRole/"unknown"}} before the DTLS negotiation starts.
                </p>
              </dd>
              <dt>
                <dfn>srtpCipher</dfn> of type <span class=
                "idlMemberType">DOMString</span>
              </dt>
              <dd>
                <p>
                  Descriptive name of the protection profile used for the SRTP transport, as
                  defined in the "Profile" column of the IANA DTLS-SRTP protection profile registry
                  [[!IANA-DTLS-SRTP]] and described further in [[RFC5764]].
                </p>
              </dd>
              <dt>
                <dfn>selectedCandidatePairChanges</dfn> of type <span class=
                "idlMemberType">unsigned long</span>
              </dt>
              <dd>
                <p>
                  The number of times that the selected candidate pair of this transport has
                  changed. Going from not having a selected candidate pair to having a
                  selected candidate pair, or the other way around, also increases this
                  counter. It is initially zero and becomes one when an initial candidate
                  pair is selected.
                </p>
              </dd>
	      <dt>
              <dfn>ccfbMessagesSent</dfn> of type <span class="idlMemberType">unsigned long</span>
	      </dt>
	      <dd>
		<p>The number of Transport-Layer Feedback Messages of type CongestionControl Feedback Packet, as described
		in [[!RFC8888]] section 3.1, sent on this transport.</p>
	      </dd>
	      <dt>
              <dfn>ccfbMessagesReceived</dfn> of type <span class="idlMemberType">unsigned long</span>
	      </dt>
	      <dd>
		<p>The number of Transport-Layer Feedback Messages of type CongestionControl Feedback Packet, as described
		in [[!RFC8888]] section 3.1, received on this transport.</p>
	      </dd>
            </dl>
          </section>
          <section>
            <h3>
              <dfn>RTCDtlsRole</dfn> enum
            </h3>
            <div>
              <pre class="idl">enum RTCDtlsRole {
      "client",
      "server",
      "unknown",
};</pre>
              <table data-link-for="RTCDtlsRole" data-dfn-for="RTCDtlsRole" class="simple">
                <caption>{{RTCDtlsRole}} Enumeration description</caption>
                <thead>
                  <tr>
                    <th>Enum value</th><th>Description</th>
                  </tr>
                </thead>
                <tbody>
                  <tr>
                    <td>
                      <dfn>client</dfn>
                    </td>
                    <td>
                      <p>
                        The RTCPeerConnection is acting as a DTLS client as defined in [[RFC6347]].
                      </p>
                    </td>
                  </tr>
                  <tr>
                    <td>
                      <dfn>server</dfn>
                    </td>
                    <td>
                      <p>
                        The RTCPeerConnection is acting as a DTLS server as defined in [[RFC6347]].
                      </p>
                    </td>
                  </tr>
                  <tr>
                    <td>
                      <dfn>unknown</dfn>
                    </td>
                    <td>
                      <p>
                        The DTLS role of the RTCPeerConnection has not been determined yet.
                      </p>
                    </td>
                  </tr>
                </tbody>
              </table>
            </div>
          </section>
        </div>
      </section>
      <section id="icecandidate-dict*">
        <h3>
          <dfn>RTCIceCandidateStats</dfn> dictionary
        </h3>
        <p>
          {{RTCIceCandidateStats}} reflects the properties of a <code class=ice>candidate</code> in
          Section 15.1 of [[!RFC5245]]. It corresponds to a {{RTCIceCandidate}} object.
        </p>
        <div>
          <pre class="idl">dictionary RTCIceCandidateStats : RTCStats {
             required DOMString       transportId;
             DOMString?               address;
             long                     port;
             DOMString                protocol;
             required RTCIceCandidateType candidateType;
             long                     priority;
             DOMString                url;
             RTCIceServerTransportProtocol relayProtocol;
             DOMString                foundation;
             DOMString                relatedAddress;
             long                     relatedPort;
             DOMString                usernameFragment;
             RTCIceTcpCandidateType   tcpType;
};</pre>
          <section>
            <h2>
              Dictionary {{RTCIceCandidateStats}} Members
            </h2>
            <dl data-link-for="RTCIceCandidateStats" data-dfn-for="RTCIceCandidateStats" class=
            "dictionary-members">
              <dt>
                <dfn>transportId</dfn> of type <span class=
                "idlMemberType">DOMString</span>
              </dt>
              <dd>
                <p>
                  It is a unique identifier that is associated to the object that was inspected to
                  produce the {{RTCTransportStats}} associated with this candidate.
                </p>
              </dd>
              <dt>
                <dfn>address</dfn> of type <span class=
                "idlMemberType">DOMString</span>
              </dt>
              <dd>
                <p>
                  It is the address of the candidate, allowing for IPv4 addresses, IPv6 addresses,
                  and fully qualified domain names (FQDNs). See [[!RFC5245]] section 15.1 for
                  details.
                </p>
                <p>
                  The user agent should make sure that only remote candidate addresses that the web
                  application has configured on the corresponding {{RTCPeerConnection}} are exposed;
                  This is especially important for peer reflexive remote candidates. By default,
                  the user agent MUST leave the {{RTCIceCandidateStats/address}} member as <code>null</code> in the
                  {{RTCIceCandidateStats}} dictionary of any remote candidate. Once a {{RTCPeerConnection}}
                  instance learns on an address by the web application using {{RTCPeerConnection/addIceCandidate()}},
                  the user agent can expose the 'address' member value in any remote
                  {{RTCIceCandidateStats}} dictionary of the corresponding {{RTCPeerConnection}} that
                  matches the newly learnt address.
                </p>
              </dd>
              <dt>
                <dfn>port</dfn> of type <span class="idlMemberType">long</span>
              </dt>
              <dd>
                <p>
                  It is the port number of the candidate.
                </p>
              </dd>
              <dt>
                <dfn>protocol</dfn> of type <span class=
                "idlMemberType">DOMString</span> <!-- TODO: reuse RTCIceProtocol? -->
              </dt>
              <dd>
                <p>
                  Valid values for transport is one of <code>"udp"</code> and <code>"tcp"</code>. Based
                  on the <code class=ice>"transport"</code> defined in [[!RFC5245]] section 15.1.
                </p>
              </dd>
              <dt>
                <dfn>candidateType</dfn> of type <span class=
                "idlMemberType">{{RTCIceCandidateType}}</span>
              </dt>
              <dd>
                <p>
                  This enumeration is defined in [[WEBRTC]].
                </p>
              </dd>
              <dt>
                <dfn>priority</dfn> of type <span class="idlMemberType">long</span>
              </dt>
              <dd>
                <p>
                  Calculated as defined in [[!RFC5245]] section 15.1.
                </p>
              </dd>
              <dt>
                <dfn>url</dfn> of type <span class="idlMemberType">DOMString</span>
              </dt>
              <dd>
                <p>
                  For local candidates of type {{RTCIceCandidateType/"srflx"}} or type
                  {{RTCIceCandidateType/"relay"}} this is the URL of the ICE server
                  from which the candidate was obtained and defined in [[WEBRTC]].
                </p>
                <p>
                  For remote candidates, this property MUST NOT be [= map/exist | present =].
                </p>
              </dd>
              <dt>
                <dfn>relayProtocol</dfn> of type <span class=
                "idlMemberType">{{RTCIceServerTransportProtocol}}</span>
              </dt>
              <dd>
                <p>
                  It is the protocol used by the endpoint to communicate with the TURN server. This
                  is only present for local relay candidates and defined in [[WEBRTC]].
                </p>
                <p>
                  For remote candidates, this property MUST NOT be [= map/exist | present =].
                </p>
              </dd>
              <dt>
                <dfn>foundation</dfn> of type <span class="idlMemberType">DOMString</span>
              </dt>
              <dd>
                <p>
                  The ICE foundation as defined in [[!RFC5245]] section 15.1.
                </p>
              </dd>
              <dt>
                <dfn>relatedAddress</dfn> of type <span class="idlMemberType">DOMString</span>
              </dt>
              <dd>
                <p>
                  The ICE rel-addr defined in [[!RFC5245]] section 15.1. Only set for serverreflexive,
                  peerreflexive and relay candidates.
                </p>
              </dd>
              <dt>
                <dfn>relatedPort</dfn> of type <span class="idlMemberType">long</span>
              </dt>
              <dd>
                <p>
                  The ICE rel-addr defined in [[!RFC5245]] section 15.1. Only set for serverreflexive,
                  peerreflexive and relay candidates.
                </p>
              </dd>
              <dt>
                <dfn>usernameFragment</dfn> of type <span class="idlMemberType">DOMString</span>
              </dt>
              <dd>
                <p data-tests="protocol/candidate-exchange.html">
                  The ICE username fragment as defined in [[!RFC5245]] section 7.1.2.3. For
                  peerreflexive remote candidates this is not set unless the ICE username fragment
                  has been previously signaled.
                </p>
              </dd>
              <dt>
              <dt>
                <dfn>tcpType</dfn> of type <span class="idlMemberType">{{RTCIceTcpCandidateType}}</span>
              </dt>
              <dd>
                <p>
                  The ICE candidate TCP type, as defined іn {{RTCIceTcpCandidateType}} and used
                  in {{RTCIceCandidate}}.
                </p>
              </dd>
            </dl>
          </section>
        </div>
      </section>
      <section id="candidatepair-dict*">
        <h3>
          <dfn>RTCIceCandidatePairStats</dfn> dictionary
        </h3>
        <div>
          <pre class="idl">dictionary RTCIceCandidatePairStats : RTCStats {
             required DOMString            transportId;
             required DOMString            localCandidateId;
             required DOMString            remoteCandidateId;
             required RTCStatsIceCandidatePairState state;
             boolean                       nominated;
             unsigned long long            packetsSent;
             unsigned long long            packetsReceived;
             unsigned long long            bytesSent;
             unsigned long long            bytesReceived;
             DOMHighResTimeStamp           lastPacketSentTimestamp;
             DOMHighResTimeStamp           lastPacketReceivedTimestamp;
             double                        totalRoundTripTime;
             double                        currentRoundTripTime;
             double                        availableOutgoingBitrate;
             double                        availableIncomingBitrate;
             unsigned long long            requestsReceived;
             unsigned long long            requestsSent;
             unsigned long long            responsesReceived;
             unsigned long long            responsesSent;
             unsigned long long            consentRequestsSent;
             unsigned long                 packetsDiscardedOnSend;
             unsigned long long            bytesDiscardedOnSend;
};</pre>
          <section>
            <h2>
              Dictionary {{RTCIceCandidatePairStats}} Members
            </h2>
            <dl data-link-for="RTCIceCandidatePairStats" data-dfn-for="RTCIceCandidatePairStats"
            class="dictionary-members">
              <dt>
                <dfn>transportId</dfn> of type <span class=
                "idlMemberType">DOMString</span>
              </dt>
              <dd>
                <p>
                  It is a unique identifier that is associated to the object that was inspected to
                  produce the {{RTCTransportStats}} associated with this candidate pair.
                </p>
              </dd>
              <dt>
                <dfn>localCandidateId</dfn> of type <span class=
                "idlMemberType">DOMString</span>
              </dt>
              <dd>
                <p>
                  It is a unique identifier that is associated to the object that was inspected to
                  produce the {{RTCIceCandidateStats}} for the local candidate associated
                  with this candidate pair.
                </p>
              </dd>
              <dt>
                <dfn>remoteCandidateId</dfn> of type <span class=
                "idlMemberType">DOMString</span>
              </dt>
              <dd>
                <p>
                  It is a unique identifier that is associated to the object that was inspected to
                  produce the {{RTCIceCandidateStats}} for the remote candidate associated
                  with this candidate pair.
                </p>
              </dd>
              <dt>
                <dfn>state</dfn> of type <span class=
                "idlMemberType">{{RTCStatsIceCandidatePairState}}</span>
              </dt>
              <dd>
                <p>
                  Represents the state of the checklist for the local and remote candidates in a
                  pair.
                </p>
              </dd>
              <dt>
                <dfn>nominated</dfn> of type <span class=
                "idlMemberType">boolean</span>
              </dt>
              <dd>
                <p>
                  Related to updating the nominated flag described in Section 7.1.3.2.4 of
                  [[!RFC5245]].
                </p>
              </dd>
              <dt>
                <dfn>packetsSent</dfn> of type <span class="idlMemberType">unsigned
                long long</span>
              </dt>
              <dd>
                <p>
                  Represents the total number of packets sent on this candidate pair.
                </p>
              </dd>
              <dt>
                <dfn>packetsReceived</dfn> of type <span class=
                "idlMemberType">unsigned long long</span>
              </dt>
              <dd>
                <p>
                  Represents the total number of packets received on this candidate pair.
                </p>
              </dd>
              <dt>
                <dfn>bytesSent</dfn> of type <span class="idlMemberType">unsigned long
                long</span>
              </dt>
              <dd>
                <p>
                  Represents the total number of payload bytes sent on this candidate pair, i.e.,
                  not including headers, padding or ICE connectivity checks.
                </p>
              </dd>
              <dt>
                <dfn>bytesReceived</dfn> of type <span class="idlMemberType">unsigned
                long long</span>
              </dt>
              <dd>
                <p>
                  Represents the total number of payload bytes received on this candidate pair,
                  i.e., not including headers, padding or ICE connectivity checks.
                </p>
              </dd>
              <dt>
                <dfn>lastPacketSentTimestamp</dfn> of type <span class=
                "idlMemberType">DOMHighResTimeStamp</span>
              </dt>
              <dd>
                <p>
                  Represents the timestamp at which the last packet was sent on this particular
                  candidate pair, excluding STUN packets.
                </p>
              </dd>
              <dt>
                <dfn>lastPacketReceivedTimestamp</dfn> of type <span class=
                "idlMemberType">DOMHighResTimeStamp</span>
              </dt>
              <dd>
                <p>
                  Represents the timestamp at which the last packet was received on this particular
                  candidate pair, excluding STUN packets.
                </p>
              </dd>
              <dt>
                <dfn>totalRoundTripTime</dfn> of type <span class=
                "idlMemberType">double</span>
              </dt>
              <dd>
                <p>
                  Represents the sum of all round trip time measurements in seconds since the
                  beginning of the session, based on STUN connectivity check [[!STUN-PATH-CHAR]]
                  responses (responsesReceived), including those that reply to requests that are
                  sent in order to verify consent [[!RFC7675]]. The average round trip time can be
                  computed from {{totalRoundTripTime}} by dividing it by
                  {{responsesReceived}}.
                </p>
              </dd>
              <dt>
                <dfn>currentRoundTripTime</dfn> of type <span class=
                "idlMemberType">double</span>
              </dt>
              <dd>
                <p>
                  Represents the latest round trip time measured in seconds, computed from both
                  STUN connectivity checks [[!STUN-PATH-CHAR]], including those that are sent for
                  consent verification [[!RFC7675]].
                </p>
              </dd>
              <dt>
                <dfn>availableOutgoingBitrate</dfn> of type <span class=
                "idlMemberType">double</span>
              </dt>
              <dd>
                <p>
                  It is calculated by the underlying congestion control by combining the available
                  bitrate for all the outgoing <a>RTP stream</a>s using this candidate pair. The bitrate
                  measurement does not count the size of the IP or other transport layers like TCP
                  or UDP. It is similar to the TIAS defined in [[!RFC3890]], i.e., it is measured
                  in bits per second and the bitrate is calculated over a 1 second window.

                  For candidate pairs in use, the estimate is normally no lower than the
                  bitrate for the packets sent at {{lastPacketSentTimestamp}}, but might
                  be higher.
                </p>
                <p>
                  Only [= map/exist =]s when the underlying congestion control calculated either a
                  send-side bandwidth estimation, for example using mechanisms such as
                  <a href="https://datatracker.ietf.org/doc/html/draft-holmer-rmcat-transport-wide-cc-extensions-01">TWCC</a>,
                  or received a receive-side estimation via RTCP, for example the one described in
                  <a href="https://datatracker.ietf.org/doc/html/draft-alvestrand-rmcat-remb-03">REMB</a>.
                  MUST NOT [= map/exist =] for candidate pairs that were never used
                  for sending packets that were taken into account for bandwidth estimation or
                  candidate pairs that have have been used previously but are not currently in use.
                </p>
              </dd>
              <dt>
                <dfn>availableIncomingBitrate</dfn> of type <span class=
                "idlMemberType">double</span>
              </dt>
              <dd>
                <p>
                  It is calculated by the underlying congestion control by combining the available
                  bitrate for all the incoming <a>RTP stream</a>s using this candidate pair. The bitrate
                  measurement does not count the size of the IP or other transport layers like TCP
                  or UDP. It is similar to the TIAS defined in [[!RFC3890]], i.e., it is measured
                  in bits per second and the bitrate is calculated over a 1 second window.

                  For pairs in use, the estimate is normally no lower than the
                  bitrate for the packets received at {{lastPacketReceivedTimestamp}}, but
                  might be higher.
                </p>
                <p>
                  Only [= map/exist =]s when a receive-side bandwidth estimation, for example
                  <a href="https://datatracker.ietf.org/doc/html/draft-alvestrand-rmcat-remb-03">REMB</a>
                  was calculated. MUST NOT [= map/exist =] for candidate pairs that were never used
                  for receiving packets that were taken into account for bandwidth estimation or
                  candidate pairs that have have been used previously but are not currently in use.
                </p>
              </dd>
              <dt>
                <dfn>requestsReceived</dfn> of type <span class=
                "idlMemberType">unsigned long long</span>
              </dt>
              <dd>
                <p>
                  Represents the total number of connectivity check requests received (including
                  retransmissions). It is impossible for the receiver to tell whether the request
                  was sent in order to check connectivity or check consent, so all connectivity
                  checks requests are counted here.
                </p>
              </dd>
              <dt>
                <dfn>requestsSent</dfn> of type <span class="idlMemberType">unsigned
                long long</span>
              </dt>
              <dd>
                <p>
                  Represents the total number of connectivity check requests sent (not including
                  retransmissions).
                </p>
              </dd>
              <dt>
                <dfn>responsesReceived</dfn> of type <span class=
                "idlMemberType">unsigned long long</span>
              </dt>
              <dd>
                <p>
                  Represents the total number of connectivity check responses received.
                </p>
              </dd>
              <dt>
                <dfn>responsesSent</dfn> of type <span class="idlMemberType">unsigned
                long long</span>
              </dt>
              <dd>
                <p>
                  Represents the total number of connectivity check responses sent. Since we cannot
                  distinguish connectivity check requests and consent requests, all responses are
                  counted.
                </p>
              </dd>
              <dt>
                <dfn>consentRequestsSent</dfn> of type <span class=
                "idlMemberType">unsigned long long</span>
              </dt>
              <dd>
                <p>
                  Represents the total number of consent requests sent.
                </p>
              </dd>
              <dt>
                <dfn>packetsDiscardedOnSend</dfn> of type <span class=
                "idlMemberType">unsigned long</span>
              </dt>
              <dd>
                <p>
                  Total number of  packets for this candidate pair that have been discarded due to socket
                  errors, i.e. a socket error occurred when handing the packets to the socket. This
                  might happen due to various reasons, including full buffer or no available
                  memory.
                </p>
              </dd>
              <dt>
                <dfn>bytesDiscardedOnSend</dfn> of type <span class=
                "idlMemberType">unsigned long long</span>
              </dt>
              <dd>
                <p>
                  Total number of bytes for this candidate pair that have been discarded due to socket
                  errors, i.e. a socket error occurred when handing the packets containing the bytes
                  to the socket. This might happen due to various reasons, including full buffer or
                  no available memory. Calculated as defined in [[!RFC3550]] section 6.4.1.
                </p>
              </dd>
            </dl>
          </section>
        </div>
        <section>
          <h3>
            <dfn>RTCStatsIceCandidatePairState</dfn> enum
          </h3>
          <div>
            <pre class="idl">enum RTCStatsIceCandidatePairState {
    "frozen",
    "waiting",
    "in-progress",
    "failed",
    "succeeded"
};</pre>
            <table data-link-for="RTCStatsIceCandidatePairState" data-dfn-for=
		   "RTCStatsIceCandidatePairState" class="simple">
	      <caption>{{RTCStatsIceCandidatePairState}} Enumeration description</caption>
              <thead>
                <tr>
		  <th>Enum value</th><th>Description</th>
                </tr>
	      </thead>
	      <tbody>
                <tr>
                  <td>
                    <dfn>frozen</dfn>
                  </td>
                  <td>
                    <p>
                      Defined in Section 5.7.4 of [[!RFC5245]].
                    </p>
                  </td>
                </tr>
                <tr>
                  <td>
                    <dfn>waiting</dfn>
                  </td>
                  <td>
                    <p>
                      Defined in Section 5.7.4 of [[!RFC5245]].
                    </p>
                  </td>
                </tr>
                <tr>
                  <td>
                    <dfn>in-progress</dfn>
                  </td>
                  <td>
                    <p>
                      Defined in Section 5.7.4 of [[!RFC5245]].
                    </p>
                  </td>
                </tr>
                <tr>
                  <td>
                    <dfn>failed</dfn>
                  </td>
                  <td>
                    <p>
                      Defined in Section 5.7.4 of [[!RFC5245]].
                    </p>
                  </td>
                </tr>
                <tr>
                  <td>
                    <dfn>succeeded</dfn>
                  </td>
                  <td>
                    <p>
                      Defined in Section 5.7.4 of [[!RFC5245]].
                    </p>
                  </td>
                </tr>
              </tbody>
            </table>
          </div>
        </section>
      </section>
      <section id="certificatestats-dict*">
        <h3>
          <dfn>RTCCertificateStats</dfn> dictionary
        </h3>
        <div>
          <pre class="idl">dictionary RTCCertificateStats : RTCStats {
             required DOMString fingerprint;
             required DOMString fingerprintAlgorithm;
             required DOMString base64Certificate;
             DOMString issuerCertificateId;
};</pre>
          <section>
            <h2>
              Dictionary {{RTCCertificateStats}} Members
            </h2>
            <dl data-link-for="RTCCertificateStats" data-dfn-for="RTCCertificateStats" class=
            "dictionary-members">
              <dt>
                <dfn>fingerprint</dfn> of type <span class=
                "idlMemberType">DOMString</span>
              </dt>
              <dd>
                <p>
                  The fingerprint of the certificate. Only use the fingerprint value as defined in
                  Section 5 of [[!RFC4572]].
                </p>
              </dd>
              <dt>
                <dfn>fingerprintAlgorithm</dfn> of type <span class=
                "idlMemberType">DOMString</span>
              </dt>
              <dd>
                <p>
                  The hash function used to compute the certificate fingerprint. For instance,
                  <code>"sha-256"</code>.
                </p>
              </dd>
              <dt>
                <dfn>base64Certificate</dfn> of type <span class=
                "idlMemberType">DOMString</span>
              </dt>
              <dd>
                <p>
                  The DER-encoded base-64 representation of the certificate.
                </p>
              </dd>
              <dt>
                <dfn>issuerCertificateId</dfn> of type <span class=
                "idlMemberType">DOMString</span>
              </dt>
              <dd>
                <p>
                  The {{issuerCertificateId}} refers to the stats object that contains the next
                  certificate in the certificate chain. If the current certificate is at the end of
                  the chain (i.e. a self-signed certificate), this will not be set.
                </p>
              </dd>
            </dl>
          </section>
        </div>
      </section>
    </section>
    <section>
      <h2>
        Examples
      </h2>
      <section>
        <h3>
          Example of a stats application
        </h3>
        <p>
          Consider the case where the user is experiencing bad sound and the application wants to
          determine if the cause of it is packet loss. The following example code might be used:
        </p>
        <pre class="example highlight">var baselineReport, currentReport;
var sender = pc.getSenders()[0];

sender.getStats().then(function (report) {
    baselineReport = report;
})
.then(function() {
    return new Promise(function(resolve) {
        setTimeout(resolve, aBit); // ... wait a bit
    });
})
.then(function() {
    return sender.getStats();
})
.then(function (report) {
    currentReport = report;
    processStats();
})
.catch(function (error) {
  console.log(error.toString());
});

function processStats() {
    // compare the elements from the current report with the baseline
    for (let now of currentReport.values()) {
        if (now.type != "outbound-rtp")
            continue;

        // get the corresponding stats from the baseline report
        let base = baselineReport.get(now.id);

        if (base) {
            remoteNow = currentReport.get(now.remoteId);
            remoteBase = baselineReport.get(base.remoteId);

            var packetsSent = now.packetsSent - base.packetsSent;
            var packetsReceived = remoteNow.packetsReceived - remoteBase.packetsReceived;

            // if intervalFractionLoss is &gt; 0.3, we've probably found the culprit
            var intervalFractionLoss = (packetsSent - packetsReceived) / packetsSent;
        }
    });
}
</pre>
      </section>
    </section>
    <section>
      <h3>
        Security and Privacy Considerations
      </h3>
      <p>
        The data exposed by WebRTC Statistics include most of the media and network data also
        exposed by [[!GETUSERMEDIA]] and [[!WEBRTC]] - as such, all the privacy and security
        considerations of these specifications related to data exposure apply as well to this
        specification.
      </p>
      <p>
        In addition, the properties exposed by {{RTCReceivedRtpStreamStats}},
        {{RTCRemoteInboundRtpStreamStats}}, {{RTCSentRtpStreamStats}},
        {{RTCOutboundRtpStreamStats}}, {{RTCRemoteOutboundRtpStreamStats}},
        {{RTCIceCandidatePairStats}}, {{RTCTransportStats}} expose network-layer data not
        currently available to the JavaScript layer.
      </p>
      <p>
        Beyond the risks associated with revealing <a data-cite="WEBRTC#revealing-ip-addresses">IP
        addresses as discussed in the WebRTC 1.0 specification</a>, some combination of the network
        properties uniquely exposed by this specification can be correlated with location.
      </p>
      <p>
        For instance, the round-trip time exposed in {{RTCRemoteInboundRtpStreamStats}} can give
        some coarse indication on how far aparts the peers are located, and thus, if one of the
        peer's location is known, this may reveal information about the other peer.
      </p>
      <p>
        When applied to isolated streams, media metrics may allow an application to infer some
        characteristics of the isolated stream, such as if anyone is speaking (by watching the
        {{RTCAudioSourceStats/audioLevel}} statistic).
      </p>
      <p>
        The following stats are deemed to be sensitive, and MUST NOT be reported for an
        <a data-cite="WEBRTC-IDENTITY#isolated-media-streams">isolated media stream</a>:
      </p>
      <ul>
        <li>{{RTCAudioSourceStats.audioLevel}}</li>
        <li>{{RTCAudioSourceStats.totalAudioEnergy}}</li>
        <li>{{RTCAudioSourceStats.audioLevel}}</li>
        <li>{{RTCInboundRtpStreamStats.audioLevel}}</li>
        <li>{{RTCInboundRtpStreamStats.totalAudioEnergy}}</li>
      </ul>
    </section>
    <section class="appendix" id=summary>
      <h2>Summary of WebRTC stats fields per type</h2>
      <table>
        <thead>
          <tr>
            <th>{{RTCStatsType}}</th><th>Dictionary</th><th>Fields</th>
          </tr>
        </thead>
        <tbody>
          <tr>
            <th class="row">{{RTCStatsType/"codec"}}</th>
            <td>{{RTCCodecStats}}</td>
          </tr>
          <tr>
            <th class="row">{{RTCStatsType/"inbound-rtp"}}</th>
            <td>{{RTCInboundRtpStreamStats}}</td>
          </tr>
          <tr>
            <th class="row">{{RTCStatsType/"outbound-rtp"}}</th>
            <td>{{RTCOutboundRtpStreamStats}}</td>
          </tr>
          <tr>
            <th class="row">{{RTCStatsType/"remote-inbound-rtp"}}</th>
            <td>{{RTCRemoteInboundRtpStreamStats}}</td>
          </tr>
          <tr>
            <th class="row">{{RTCStatsType/"remote-outbound-rtp"}}</th>
            <td>{{RTCRemoteOutboundRtpStreamStats}}</td>
          </tr>
          <tr>
            <th class="row">{{RTCStatsType/"media-source"}}</th>
            <td>{{RTCAudioSourceStats}} {{RTCVideoSourceStats}}</td>
          </tr>
          <tr>
            <th class="row">{{RTCStatsType/"media-playout"}}</th>
            <td>{{RTCAudioPlayoutStats}}</td>
          </tr>
          <tr>
            <th class="row">{{RTCStatsType/"peer-connection"}}</th>
            <td>{{RTCPeerConnectionStats}}</td>
          </tr>
          <tr>
            <th class="row">{{RTCStatsType/"data-channel"}}</th>
            <td>{{RTCDataChannelStats}}</td>
          </tr>
          <tr>
            <th class="row">{{RTCStatsType/"transport"}}</th>
            <td>{{RTCTransportStats}}</td>
          </tr>
          <tr>
            <th class="row">{{RTCStatsType/"candidate-pair"}}</th>
            <td>{{RTCIceCandidatePairStats}}</td>
          </tr>
          <tr>
            <th class="row">{{RTCStatsType/"local-candidate"}}</th>
            <td>{{RTCIceCandidateStats}}</td>
          </tr>
          <tr>
            <th class="row">{{RTCStatsType/"remote-candidate"}}</th>
            <td>{{RTCIceCandidateStats}}</td>
          </tr>
          <tr>
            <th class="row">{{RTCStatsType/"certificate"}}</th>
            <td>{{RTCCertificateStats}}</td>
          </tr>
        </tbody>
      </table>
    </section>
      <section class="appendix">
        <h2>
          Acknowledgements
        </h2>
        <p>
          The editors wish to thank the Working Group chairs, Stefan Håkansson, and the Team
          Contact, Dominique Hazaël-Massieux, for their support. The editors would like to thank
          Bernard Aboba, Taylor Brandstetter, Henrik Boström, Jan-Ivar Bruaroey, Karthik Budigere,
          Cullen Jennings, and Lennart Schulte for their contributions to this specification.
        </p>
      </section>
  </body>
</html>