Use av_rescale_q() for converting FFmpeg timestamps to base::TimeDelta.

Use av_rescale_q() for converting FFmpeg timestamps to base::TimeDelta.

Previously we were using integer math to convert to microseconds, but depending on the frame rate and packet size we could introduce enough error that could accumulate and introduce audio/video synchronization drift.  av_rescale_q() is a simple function but is designed to minimize error as much as possible.

[scherkus (not reviewing), 2009-05-19 21:54:48]

You said you were interested ;)

There's still some debug code in ffmpeg_audio_decoder.cc that will be removed
after I'm finished testing.

[awong, 2009-05-19 22:12:29]

http://codereview.chromium.org/113598/diff/1/3
File media/filters/ffmpeg_audio_decoder.cc (right):

http://codereview.chromium.org/113598/diff/1/3#newcode99
Line 99: wsprintf(str, L"Fixing duration: %d\n",
(int)duration.InMilliseconds());
why not %lld?

http://codereview.chromium.org/113598/diff/1/3#newcode100
Line 100: OutputDebugString(str);
hrm...how does i18n work btw?  Is this message going to be queued for
translation?  Why a wchar_t?

http://codereview.chromium.org/113598/diff/1/3#newcode118
Line 118: microseconds /= codec_context_->channels;
maybe calculate one big denominator and then only do 1 floating-point divide?

[scherkus (not reviewing), 2009-05-19 23:19:18]

Fixed up floating point math and removed debug code.

[awong, 2009-05-19 23:30:49]

lgtm

one nitpick about super long expression readability.

http://codereview.chromium.org/113598/diff/1002/1004
File media/filters/ffmpeg_audio_decoder.cc (right):

http://codereview.chromium.org/113598/diff/1002/1004#newcode115
Line 115: double microseconds = size / (codec_context_->channels *
Errr...break the integral portion into another variable that's an int64, and add
a comment on what it is and wanting to avoid a serial set of divides on floats.

Then end up with?

double microseconds = size;
microseconds /= denomiator / static_cast<double>(kMicrosecondsPerSecond);

[scherkus (not reviewing), 2009-05-19 23:41:29]

ok take one more peek

[awong, 2009-05-19 23:48:00]

still lgtm. :)