MediaSource: handle property
Note: This feature is only available in Dedicated Web Workers.
The handle
read-only property of the MediaSource
interface returns a MediaSourceHandle
object, a proxy for the MediaSource
that can be transferred from a dedicated worker back to the main thread and attached to a media element via its HTMLMediaElement.srcObject
property.
Note: handle
is only visible on MediaSource
instances inside dedicated workers.
Each MediaSource
object created inside a dedicated worker has its own distinct MediaSourceHandle
. The handle
getter will always return the MediaSourceHandle
instance specific to the associated dedicated worker MediaSource
instance. If the handle has already been transferred to the main thread using postMessage()
, the handle instance in the worker is technically detached and can't be transferred again.
Value
A MediaSourceHandle
object instance.
Examples
The 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: MediaSourceHandle
s cannot be successfully transferred into or via a shared worker or service worker.
Specifications
Specification |
---|
Media Source Extensions™ # dom-mediasource-handle |
Browser compatibility
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