1512506 - MDSM would dispatch LOTS audio decoding tasks when we seek audio directly to EOS during looping decoding

Status: RESOLVED FIXED

(Core :: Audio/Video: Playback, enhancement, P2)

Comment 1

[Alastor Wu [:alwu][PTO 5/15-5/18]]

I found that if we seek looping audio directly into EOS, MDSM will dispatch LOTS of decoding tasks because of wrong estimation of decoded audio duration, which might cause CPU and memory waste.

> [Child 38615: MediaPlayback #1]: V/MediaDecoder MediaDecoderStateMachine[0x12d79a000] Decoder=125817000 Queueing audio task - queued=6574, decoder-queued=1

From the log, you can see we've queued 6574 samples (and MDSM still continues to dispatch decoding task) in AudioQueue.

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The reason of this issue is that, when we directly seek to EOS, seeking state would change MDSM's `mCurrentPosition` when seeking finished. 

In this situation, when entering `loopingDecoding` state, it doesn't set `mAudioLoopingOffset` yet so that we can't do time-adjustment for decoding samples. 

When we start the media sink, we would use the time where EOS happens as media sink's start time. As we didn't get the audio offset before, we can't adjust audio sample time in order to make them larger than clock time.
Therefore, the estimation of decoded audio duration would be incorrect, and MDSM would always think we don't have enough data because `mDecodedAudioEndTime - clock's time` is smaller zero.

Comment 2

[Alastor Wu [:alwu][PTO 5/15-5/18]]

Attachment: Bug 1512506 - Prevent MDSM from dispatching lots of audio decoding tasks when seeking directly to EOS during looping.

To make sure media sink starts from the correct position, otherwise, we would get incorrect estimation of decoded audio
duration when we directly seek looping audio to EOS. That would results in MDSM continually dispatching decoding tasks
even if we've enough data.

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/cc946b482d75
Prevent MDSM from dispatching lots of audio decoding tasks when seeking directly to EOS during looping. r=jya

Comment 4

[Razvan Maries]

https://hg.mozilla.org/mozilla-central/rev/cc946b482d75