HTMLMediaElement: srcObject property
Limited availability
This feature is not Baseline because it does not work in some of the most widely-used browsers.
The srcObject property of the
HTMLMediaElement interface sets or returns the object which serves as
the source of the media associated with the HTMLMediaElement, or null if not assigned.
The object can be a MediaStream, a MediaSource, a
Blob, or a File (which inherits from Blob).
Note:
As of March 2020, only Safari has full support for srcObject, i.e., using MediaSource, MediaStream, Blob, and File objects as values. Other browsers support MediaStream objects; until they catch up, consider falling back to creating a URL with URL.createObjectURL() and assigning it to HTMLMediaElement.src (see below for an example). In addition, as of version 108 Chromium supports attaching a dedicated worker MediaSource object by assigning that object's MediaSourceHandle instance (transferred from the worker) to srcObject.
Value
A MediaStream, MediaSource, Blob, or
File object (though see the compatibility table for what is actually
supported), or null if not assigned.
Usage notes
Older versions of the Media Source specification required using
URL.createObjectURL() to create an object URL then
setting src to that URL. Now you can just set
srcObject to the MediaStream directly.
Examples
Basic example
In this example, a MediaStream from a camera is assigned to a
newly-created <video> element.
const mediaStream = await navigator.mediaDevices.getUserMedia({ video: true });
const video = document.createElement("video");
video.srcObject = mediaStream;
In this example, a new MediaSource is assigned to a newly-created
<video> element.
const mediaSource = new MediaSource();
const video = document.createElement("video");
video.srcObject = mediaSource;
Supporting fallback to the src property
The examples below support older browser versions that require you to create an object
URL and assign it to src if srcObject isn't supported.
First, a MediaStream from a camera is assigned to a newly-created
<video> element, with fallback for older browsers.
const mediaStream = await navigator.mediaDevices.getUserMedia({ video: true });
const video = document.createElement("video");
if ("srcObject" in video) {
video.srcObject = mediaStream;
} else {
// Avoid using this in new browsers, as it is going away.
video.src = URL.createObjectURL(mediaStream);
}
Second, a new MediaSource is assigned to a newly-created
<video> element, with fallback for older browsers and browsers that
don't yet support assignment of MediaSource directly.
const mediaSource = new MediaSource();
const video = document.createElement("video");
// Older browsers may not have srcObject
if ("srcObject" in video) {
try {
video.srcObject = mediaSource;
} catch (err) {
if (err.name !== "TypeError") {
throw err;
}
// Even if they do, they may only support MediaStream
video.src = URL.createObjectURL(mediaSource);
}
} else {
video.src = URL.createObjectURL(mediaSource);
}
Constructing a MediaSource in a worker and passing it to the main thread to play
The MediaSource.handle property can be accessed inside a dedicated worker and the resulting MediaSourceHandle object is then transferred over to the thread that created the worker (in this case the main thread) via a postMessage() call:
// Inside dedicated worker
let mediaSource = new MediaSource();
let handle = mediaSource.handle;
// Transfer the handle to the context that created the worker
postMessage({ arg: handle }, [handle]);
mediaSource.addEventListener("sourceopen", () => {
// Await sourceopen on MediaSource before creating SourceBuffers
// and populating them with fetched media — MediaSource won't
// accept creation of SourceBuffers until it is attached to the
// HTMLMediaElement and its readyState is "open"
});
Over in the main thread, we receive the handle via a message event handler, attach it to a <video> via its HTMLMediaElement.srcObject property, and play the video:
worker.addEventListener("message", (msg) => {
let mediaSourceHandle = msg.data.arg;
video.srcObject = mediaSourceHandle;
video.play();
});
Note:
MediaSourceHandles cannot be successfully transferred into or via a shared worker or service worker.
Specifications
| Specification |
|---|
| HTML # dom-media-srcobject-dev |
| Media Source Extensions™ # htmlmediaelement-extensions-srcobject |
Browser compatibility
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