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Implement cross-thread MediaSource attachments #4314

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@at-ninja at-ninja commented Oct 25, 2024

Port relevant Chromium code to the Cobalt 25 codebase to allow for
MediaSource objects on a Dedicated Worker to render frames on a
HTMLMediaElement owned by the main browser thread.

Usage of this feature is gated behind the MediaSource.EnableInWorkers
H5VCC flag. In addition, the
MediaElement.EnableUsingMediaSourceBufferedRange and
MediaElement.EnableUsingMediaSourceAttachmentMethods flags are also
required as pre-requisite features.

This commit does introduce mutex locks to the SourceBuffer and MediaSource
classes that cannot be fully gated behind H5VCC flags. However, current
usage of both classes is contained to single-threaded usecases. As such,
the mutex lock code should be an effective no-op.

This is based off of the following Chromium commits:

b/338425382

@at-ninja at-ninja force-pushed the cross-thread-media-source-attachments branch from 55fac9b to 2e35a64 Compare October 30, 2024 19:24
@at-ninja at-ninja changed the title [draft] Cross thread media source attachments Implement cross-thread MediaSource attachments Oct 30, 2024
Port relevant Chromium code to the Cobalt 25 codebase to allow for
`MediaSource` objects on a Dedicated Worker to render frames on a
`HTMLMediaElement` owned by the main browser thread.

Usage of this feature is gated behind the `MediaSource.EnableInWorkers`
H5VCC flag. In addition, the
`MediaElement.EnableUsingMediaSourceBufferedRange` and
`MediaElement.EnableUsingMediaSourceAttachmentMethods` flags are also
required as pre-requisite features.

This commit does introduce mutex locks to the `SourceBuffer` and `MediaSource`
classes that cannot be fully gated behind H5VCC flags. However, current
usage of both classes is contained to single-threaded usecases. As such,
the mutex lock code should be an effective no-op.

This is based off of the following Chromium commits:

* https://chromium-review.googlesource.com/c/chromium/src/+/2459431
* https://chromium-review.googlesource.com/c/chromium/src/+/2617351
* https://chromium-review.googlesource.com/c/chromium/src/+/2909389

b/338425382
@at-ninja at-ninja force-pushed the cross-thread-media-source-attachments branch from 2e35a64 to 5fc5cd4 Compare October 31, 2024 20:04
@at-ninja at-ninja marked this pull request as ready for review October 31, 2024 20:05
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Looks great!

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2 participants