[Ffmpeg-devel] [BUG] PCM audio from VOB files always decodes as 16 bit.

[Allan Hsu]

I noticed this bug today while trying to transcode a VOB file. The  
PCM track on the DVD is labeled "HD PCM" and I suspect that the PCM  
data is 20 or 24 bits per sample. ffmpeg identifies the PCM track as  
pcm_s16be and tries to decode it as such. The resulting file has an  
audio track that contains what sounds like noise plus what sounds  
like the proper audio, slowed down. The audio stream on the resulting  
file is also much longer than the video stream. I've uploaded the  
file to the FTP as neko.vob and the ffmpeg output is here:

./ffmpeg -i ~/Desktop/neko.vob -acodec pcm_s16le -ac 2 -ar 48000 - 
vcodec mpeg4 -b 768k ~/Desktop/neko.avi
FFmpeg version SVN-r7712, Copyright (c) 2000-2006 Fabrice Bellard, et  
al.
   configuration:  --enable-gpl --enable-x264 --enable-xvid --enable- 
mp3lame --extra-cflags=-I/Users/allan/code/usr/include --extra- 
ldflags=-L/Users/allan/code/usr/lib
   libavutil version: 49.2.0
   libavcodec version: 51.29.0
   libavformat version: 51.8.0
   built on Jan 25 2007 14:44:41, gcc: 4.0.1 (Apple Computer, Inc.  
build 5367)
Input #0, mpeg, from '/Users/allan/Desktop/neko.vob':
   Duration: 00:00:08.8, start: 2064.871300, bitrate: 9259 kb/s
   Stream #0.0[0x1e0]: Video: mpeg2video, yuv420p, 720x480, 9800 kb/ 
s, 29.97 fps(r)
   Stream #0.1[0xa0]: Audio: pcm_s16be, 48000 Hz, stereo, 1536 kb/s
   Stream #0.2[0x89]: Audio: 0x0000
Output #0, avi, to '/Users/allan/Desktop/neko.avi':
   Stream #0.0: Video: mpeg4, yuv420p, 720x480, q=2-31, 768 kb/s,  
29.97 fps(c)
   Stream #0.1: Audio: pcm_s16le, 48000 Hz, stereo, 1536 kb/s
Stream mapping:
   Stream #0.0 -> #0.0
   Stream #0.1 -> #0.1
Press [q] to stop encoding
[mpeg2video @ 0x43c3b0]ac-tex damaged at 9 1bitrate=2506.5kbits/s
[mpeg2video @ 0x43c3b0]Warning MVs not available
[mpeg2video @ 0x43c3b0]concealing 1305 DC, 1305 AC, 1305 MV errors
frame=  265 q=13.1 Lsize=    3505kB time=8.8 bitrate=3247.7kbits/s
video:999kB audio:2423kB global headers:0kB muxing overhead 2.453207%

-Allan

--
Allan Hsu <allan at counterpop dot net>
1E64 E20F 34D9 CBA7 1300  1457 AC37 CBBB 0E92 C779