[FFmpeg-user] MPEG AC-3 Error

Kirk Bocek t004 at kbocek.com
Fri Dec 19 20:02:43 CET 2014


I am attempting to split a large MPG file containing MPEG-2 video and 
AC-3 audio into a smaller file. However the resulting file's AC-3 audio 
seems to be broken. I am working on CentOS 6.6 X86_64. The source file 
and my ffmpeg version looks like:

$ ffmpeg -i SNL20141213.mpg
ffmpeg version 0.10.15 Copyright (c) 2000-2014 the FFmpeg developers
   built on Aug 30 2014 15:49:19 with gcc 4.4.7 20120313 (Red Hat 4.4.7-3)
   configuration: --prefix=/usr --bindir=/usr/bin 
--datadir=/usr/share/ffmpeg --incdir=/usr/include/ffmpeg 
--libdir=/usr/lib64 --mandir=/usr/share/man --arch=x86_64 
--extra-cflags='-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions 
-fstack-protector --param=ssp-buffer-size=4 -m64 -mtune=generic' 
--enable-bzlib --disable-crystalhd --enable-gnutls --enable-libass 
--enable-libcdio --enable-libcelt --enable-libdc1394 
--disable-indev=jack --enable-libfreetype --enable-libgsm 
--enable-libmp3lame --enable-openal --enable-libopenjpeg 
--enable-libpulse --enable-librtmp --enable-libschroedinger 
--enable-libspeex --enable-libtheora --enable-libvorbis --enable-libv4l2 
--enable-libx264 --enable-libxvid --enable-x11grab --enable-avfilter 
--enable-postproc --enable-pthreads --disable-static --enable-shared 
--enable-gpl --disable-debug --disable-stripping --shlibdir=/usr/lib64 
--enable-runtime-cpudetect
   libavutil      51. 35.100 / 51. 35.100
   libavcodec     53. 61.100 / 53. 61.100
   libavformat    53. 32.100 / 53. 32.100
   libavdevice    53.  4.100 / 53.  4.100
   libavfilter     2. 61.100 /  2. 61.100
   libswscale      2.  1.100 /  2.  1.100
   libswresample   0.  6.100 /  0.  6.100
   libpostproc    52.  0.100 / 52.  0.100
Input #0, mpegts, from 'SNL20141213.mpg':
   Duration: 01:36:57.52, start: 5443.377922, bitrate: 18218 kb/s
   Program 1
     Stream #0:0[0x7c0]: Video: mpeg2video (Main) ([2][0][0][0] / 
0x0002), yuv420p, 1920x1080 [SAR 1:1 DAR 16:9], 38810 kb/s, 29.97 fps, 
29.97 tbr, 90k tbn, 59.94 tbc
     Stream #0:1[0x7c1]: Audio: ac3 ([129][0][0][0] / 0x0081), 48000 Hz, 
5.1(side), s16, 384 kb/s

I am splitting the file with the command:

ffmpeg -i SNL20141213.mpg -acodec ac3 -ab 384k -vcodec copy -t 0:20:00 
-ss 0:5:00 -y SNL-split.mpg

I see this error message in the output:

Incompatible sample format 's16' for codec 'ac3', auto-selecting format 
'flt'

The resulting file looks like:

Input #0, mpeg, from 'SNL-split.mpg':
   Duration: 00:20:00.07, start: 1.000000, bitrate: 18145 kb/s
     Stream #0:0[0x80]: Audio: ac3, 48000 Hz, 5.1(side), s16, 384 kb/s
     Stream #0:1[0x1e0]: Video: mpeg2video (Main), yuv420p, 1920x1080 
[SAR 1:1 DAR 16:9], 38810 kb/s, 29.97 fps, 29.97 tbr, 90k tbn, 59.94 tbc

The resulting file does not play audio in VLC. Does anyone have any 
suggestions on either the error message or getting playable AC-3 audio 
in the output file?

Thanks.





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