[Ffmpeg-devel] ac3 -> no sound

Justin Ruggles jruggle
Tue Apr 4 15:59:39 CEST 2006

Edmund Mergl wrote:
> Hello Justin,
> thanks for answering.
> A sample of the output can be found here:  http://www.edmund-mergl.de/test-part.avi
> It has been prepared with the following command:
> ffmpeg -i test-part.vob -f avi -vcodec mpeg4 -b 3000 -g 300 -acodec ac3 -bf 2 -s 720x528 test-part.avi
> I used the CVS version from yesterday.
> mplayer and xine have no sound although the sound is ok, when playing the vob file.
> Edmund
> Justin Ruggles wrote:
>>Edmund Mergl wrote:
>>>I'm trying to recode a vob-file retaining the orignal ac3 sound.
>>>The result is an avi, whithout any sound :-(
>>>This is the command-line I've used:
>>>ffmpeg -i test.vob -f avi -vcodec mpeg4 -b 3000 -g 300 -acodec ac3 -bf 2 -s 720x528 test.avi
>>>Playing the original vob file with xine or mplayer has sound.
>>>Recoding the vob-file and converting the sound to mp3 is ok:
>>>ffmpeg -i test.vob -f avi -vcodec mpeg4 -b 3000 -g 300 -acodec mp3 -bf 2 -s 720x528 test.avi
>>>Only ac3 does not work.
>>>Here is the output from ffmpeg (source from CVS today, same problem with older versions):
>>>FFmpeg version CVS, Copyright (c) 2000-2004 Fabrice Bellard
>>>  configuration:  --enable-shared --enable-gpl --enable-mp3lame --enable-a52 --enable-amr_wb --enable-amr_nb --enable-faad --enable-faac
>>>  libavutil version: 49.0.0
>>>  libavcodec version: 51.8.0
>>>  libavformat version: 50.4.0
>>>  built on Apr  3 2006 09:48:37, gcc: 4.0.2 20051125 (Red Hat 4.0.2-8)
>>>Input #0, mpeg, from 'test.vob':
>>>  Duration: 00:26:10.2, start: 0.280633, bitrate: 5469 kb/s
>>>  Stream #0.0[0x1e0], 29.97 fps(r): Video: mpeg2video, yuv420p, 720x480, 9800 kb/s
>>>  Stream #0.1[0x80]: Audio: ac3, 48000 Hz, stereo, 192 kb/s
>>>Output #0, avi, to 'test.avi':
>>>  Stream #0.0, 29.97 fps(c): Video: mpeg4, yuv420p, 720x528, q=2-31, 3000 kb/s
>>>  Stream #0.1: Audio: ac3, 48000 Hz, stereo, 64 kb/s
>>>Stream mapping:
>>>  Stream #0.0 -> #0.0
>>>  Stream #0.1 -> #0.1
>>>Press [q] to stop encoding
>>>The first 200 MB of the original vob-file can be found here:  http://www.edmund-mergl.de/test-part.vob
>>>(in this movie the sounds starts after 2 minutes)
>>I can't reproduce the problem here. Using latest CVS, the result plays
>>just fine for me with both ffplay and mplayer.  There is some low-volume
>>sound right away, and dialog starts after about 3 minutes.  Maybe give a
>>link to a sample of your output file so the problem can be traced to
>>either the encoder or your decoder.

There seems to be something screwy going on with the avi format in your
sample.  ffplay will play the clip just fine, but mplayer doesn't seem
to like it.  There is audio playing, but mplayer (or at least the
version I'm using) has problems with the audio/video sync.  When I run
'avi2raw' or 'ffmpeg -acodec copy' and extract the audio, the resulting
ac3 file plays as expected.


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