#673: Regression on demuxing mp3 track from an .MOV file.
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Reporter: dongwon | Type: defect
Status: new | Priority: important
Component: avformat | Version: git-master
Keywords: mov,mp4 | Blocked By:
Blocking: | Reproduced by developer: 0
Analyzed by developer: 0 |
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When I try to play the attached sample mov file, I can see the following
errors and can't hear any sound.
{{{
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x2014600]error unaligned chunk.
}}}
(This happens on ffplay >= 0.6.3 including current git while 0.5.5 works
well with the sample file. Also, I've checked the file with vlc and totem
players and they worked fine.)
I checked the code which emits the log and found out it fails to build an
index for audio stream due to the following sanity checking code. (which
is introduced between 0.5.5 and 0.6.3)
== ffmpeg/avformat/mov.c ==
{{{
if (sc->samples_per_frame && chunk_samples %
sc->samples_per_frame) {
av_log(mov->fc, AV_LOG_ERROR, "error unaligned chunk\n");
return;
}
}}}
If I read the code correctly, it is using two different units regarding
"sample".
In samples_per_frame, "sample" means the uncompressed samples when we say
sampling rates.
(reference: "Samples per packet" -
http://developer.apple.com/library/mac/#documentation/QuickTime/QTFF/QTFFChap3/qtff3.html#//apple_ref/doc/uid/TP40000939-CH205-131395)
In chunk_samples, "sample" means a unit of media data like elementary
stream.
(reference: "Samples per chunk" in 'stsc' atom,
http://developer.apple.com/library/mac/#documentation/QuickTime/QTFF/QTFFChap2/qtff2.html#//apple_ref/doc/uid/TP40000939-CH204-25691)
So, I think modulo operation between them does not make sense.
I'm setting the priority to "important" because this is a regression.
--
Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/673>
FFmpeg <http://ffmpeg.org>
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