569187 - mAudioEndTime used before it's initialized (buffering logic decodes thousands of audio packets)

Status: RESOLVED FIXED

(Core :: Audio/Video, defect)

Description

[Matthew Gregan [:kinetik]]

I can reproduce this by opening a largish non-autoplay video and then immediately seeking to the middle.

We can get in a situation where the AudioLoop is waiting at http://mxr.mozilla.org/mozilla-central/source/content/media/nsBuiltinDecoderStateMachine.cpp#341 with:

(gdb) p mState
$20 = nsDecoderStateMachine::DECODER_STATE_DECODING
(gdb) p mStopDecodeThreads
$21 = 0 '\0'
(gdb) p IsPlaying()
$22 = 0
(gdb) p mReader.mRawPtr->mAudioQueue.GetSize()
$23 = 33273
(gdb) p mReader.mRawPtr->mAudioQueue.AtEndOfStream()
$24 = 0

In DecodeLoop(), we're constantly decoding audio to try to meet the targets, but:

227	      audioDecoded = mReader->mAudioQueue.Duration() +
228	                     mAudioEndTime - currentTime;

(gdb) p mReader.mRawPtr->mAudioQueue.Duration()
$25 = 709802
(gdb) p mAudioEndTime
$26 = -1
(gdb) p currentTime
$27 = 1254821
(gdb) p audioDecoded
$28 = -545020

Comment 1

[Matthew Gregan [:kinetik]]

Attachment: patch v0

Don't use mAudioEndTime in calculations if it's still -1.  -1 is a sentinel value that indicates we haven't written any audio to the backend since initialization.

Comment 2

[Chris Pearce [:cpearce (Not reading bugmail)]]

http://hg.mozilla.org/mozilla-central/rev/fa1972c19a0b