Bug 284448 – [WebCodecs] Limit the number of decode operations we can enqueue

• Status: RESOLVED
• Resolution: FIXED
• Component: Media

[Jean-Yves Avenard [:jya]]

Per spec [1] ; when decode is called, we are to:
1- increment the "decodeQueueSize"
2- enqueue a control message 
3- Process the control message queue
4- If the codec is saturated we are to return early with "not processed"
5- If not, decrement decodeQueueSize and pass the data to the "codec implementation"


In our implementation, we have no concept of the codec being "saturated". as such we always immediately queue the data to be decoded to the AudioDecoder's queue.

As a consequence, or decodeQueueSize is never greater than 0.

In the webcodec's registry sample, https://w3c.github.io/webcodecs/samples/audio-video-player/audio_video_player.html the code relies on the decodeQueueSize() increasing in size to know when to stop enqueue. With our implementation, as the queue size is always 0, we decode and very quickly fills the audio ring buffer and those decoded audio frames are lost.

We should limit the number of audio decode we run simultaneously, Chrome appears to limit that number to just 1. 

We should do the same.

[1] https://w3c.github.io/webcodecs/#dom-audiodecoder-decode

[Radar WebKit Bug Importer]

<rdar://problem/141272065>

[Jean-Yves Avenard [:jya]]

Pull request: https://github.com/WebKit/WebKit/pull/37811

[EWS]

Committed 287798@main (53a8065088fb): <https://commits.webkit.org/287798@main>

Reviewed commits have been landed. Closing PR #37811 and removing active labels.