[Ffmpeg-devel] ac3 -> no sound

Edmund Mergl e.mergl
Wed Apr 5 00:05:40 CEST 2006


Justin Ruggles wrote:
> 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:
>>
>>
>>>Hello,
>>>
>>>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)
>>>>
>>>>
>>>>Edmund
>>>
>>>
>>>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.
>>>
>>>-Justin
> 
> 
> 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.
> 
> -Justin
> 
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> 
> 

Hello Justin,

I found a work-around:

   mpeg_ps_extract --video Megaleksandros1-001.vob
   mpeg_ps_extract --audio Megaleksandros1-001.vob
   transcode -i Megaleksandros1-001.m2v -w 2000,50 -y xvid4,null -f 30,4 -o Megaleksandros1-001_pre.avi
   avimerge  -i Megaleksandros1-001_pre.avi -p Megaleksandros1-001.ac3 -a 0 -A 0 -o Megaleksandros1-001.avi

result is ok, sound and video are in sync and I'm happy, because the DVD is hard to get
and few ac3-frames in the first VOB-file have CRC-errors.

Edmund








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