[Ffmpeg-devel] ffmpeg bug or stream wrong info ?

Thanos Kyritsis djart
Fri Nov 11 13:44:31 CET 2005


I have a QT mov file that reports having a mp2 audio stream 
(CODEC_ID_MP2), while in reality it is a mp3 stream (CODEC_ID_MP3) !!


$ ffmpeg -acodec copy -i revelations_film_QT_large.mov file.mp2
ffmpeg version CVS, build 3277056, Copyright (c) 2000-2004 Fabrice 
Bellard
  configuration:  --enable-mp3lame --enable-a52 --enable-gpl 
--enable-shared
  built on Nov 11 2005 14:25:01, gcc: 3.3.6

Seems that stream 0 comes from film source: 29970.00 (29970/1) -> 29.97 
(30000/1001)
Input #0, mov,mp4,m4a,3gp,3g2, from 'revelations_film_QT_large.mov':
  Duration: 00:47:13.5, start: 0.000000, bitrate: 717 kb/s
  Stream #0.0, 29.97 fps: Video: svq3, yuv420p, 534x400
  Stream #0.1: Audio: mp2, 44100 Hz, stereo
Output #0, mp2, to 'file.mp2':
  Stream #0.0: Audio: mp2, 44100 Hz, stereo
Stream mapping:
  Stream #0.1 -> #0.0
Press [q] to stop encoding
error, non monotone timestamps 255015182 >= 255015182
size=   44172kB time=2833.5 bitrate= 127.7kbits/s
video:0kB audio:44173kB global headers:0kB muxing overhead -0.001844%


$ ffmpeg -acodec copy -i file.mp2 file2.mp2
ffmpeg version CVS, build 3277056, Copyright (c) 2000-2004 Fabrice 
Bellard
  configuration:  --enable-mp3lame --enable-a52 --enable-gpl 
--enable-shared
  built on Nov 11 2005 14:25:01, gcc: 3.3.6
Input #0, mp3, from 'file.mp2':
  Duration: 00:47:06.9, start: 0.000000, bitrate: 127 kb/s
  Stream #0.0: Audio: mp3, 44100 Hz, stereo, 128 kb/s
Output #0, mp2, to 'file2.mp2':
  Stream #0.0: Audio: mp3, 44100 Hz, stereo, 128 kb/s
Stream mapping:
  Stream #0.0 -> #0.0
Press [q] to stop encoding
size=   44172kB time=2833.5 bitrate= 127.7kbits/s
video:0kB audio:44172kB global headers:0kB muxing overhead 0.000000%


If I use ffmpeg to decode audio from the .mov file, it decodes just fine 
(ffmpeg -acodec pcm_s16le file.mov file.wav), while a more simple code 
(like a modified apiexample.c) does not decode it properly because the 
audio stream is recognised as MP2!

If I stream copy the audio stream (extract the audio stream from 
the .mov container) and then use the code from apiexample.c to decode 
it, it decodes just fine, just because this audio stream alone appears 
as mp3, while inside the .mov, it appears as mp2!

Any ideas ?

The original mov stream is available freely over the net, it's located 
at the following address if you want to test it:
http://www.panicstruckpro.com/revelations/revelations_movie.html

-- 
Thanos Kyritsis <djart at linux.gr>

- What's your ONE purpose in life ?
- To explode, of course! ;-)





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