568432 - Assertion while seeking in the WebM backend

Status: RESOLVED FIXED

(Core :: Audio/Video, defect)

Description

[Matthew Gregan [:kinetik]]

We're hitting the following assertion infrequently when seeking in the WebM backend:

###!!! ASSERTION: Seek target should lie inside the first frame after seek: 'video->mTime <= seekTime && seekTime <= video->mTime + mReader->GetInfo().mCallbackPeriod', file /Users/kinetik/work/mozilla-central/content/media/nsBuiltinDecoderStateMachine.cpp, line 892


Ignoring the fact that mCallbackPeriod is bogus for WebM files (we hardcode it to 50ms), this assertion appears to be catching a valid problem in some cases:

(gdb) p seekTime
$13 = 3332739
(gdb) p video.mRawPtr->mTime
$14 = 3332746

We've landed at a frame 7ms ahead of the target time.

It's possible this is fixed by my seeking patch in bug 568162.  I haven't been able to reproduce the assertion with that patch applied, but it's possible I didn't test thoroughly enough.

Comment 1

[Matthew Gregan [:kinetik]]

With the file I hit this assertion on, the frame times seem to vary between 33ms and 50ms, so the old code with the hardcoded frame time of 40ms would cause us stop decoding forward after seeking when landing on a 33ms long frame.  This explains the 7ms discrepancy.  It'd also be possible to decode too far forward if we landed on a 50ms long frame.  My seeking patch in bug 568162 fixes both cases by using the start time of the following frame as the end time for the currently inspected frame.

This assertion may still fire because it relies on mCallbackPeriod.  Fixing that is bug 568431.

Comment 2

[Matthew Gregan [:kinetik]]

Fixed by bug 568431 landing.