[FFmpeg-user] really simple pan= question

Paul Miller listmail at voltar-confed.org
Tue May 8 17:15:46 CEST 2012



On Tue, May 08, 2012 at 05:03:51PM +0200, Nicolas George wrote:
> Le decadi 20 floréal, an CCXX, Paul Miller a écrit :
> > for i in c{0..5}; do
> >     ffmpeg -i short.mkv -strict experimental -filter:a pan=1:c0=$i -ac 1 -y $i.mp3;
> > done
> 
> Audio filtering is not yet supported in the ffmpeg command line tool, you
> need to use workarounds to use it:
> 
> ffmpeg -f lavfi -i amovie=short.mkv,pan=1:c0=$i

This is really interesting and probably explains everything.
It's funny that the man pages clearly indicate these filters
exist and ffmpeg produces no errors when you try to use them.

> The -strict experimental seems strange.

Not *that* strange I hope.  I'm arch, so everything is bleeding
new.  This channel spliting is yak shaving and -strict
experimental is vestigial, relating to my actual transcode
project where the output has an aac audio stream.  Without strict
experimental I get this:


ffmpeg -i short.mkv short.aac
ffmpeg version 0.10.2 Copyright (c) 2000-2012 the FFmpeg developers
  built on Mar 17 2012 08:51:02 with gcc 4.6.3
  configuration: --prefix=/usr --enable-libmp3lame --enable-libvorbis --enable-libxvid --enable-libx264 --enable-libvpx --enable-libtheora --enable-libgsm --enable-libspeex --enable-postproc --enable-shared --enable-x11grab --enable-libopencore_amrnb --enable-libopencore_amrwb --enable-libschroedinger --enable-libopenjpeg --enable-librtmp --enable-libpulse --enable-gpl --enable-version3 --enable-runtime-cpudetect --disable-debug --disable-static
  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, matroska,webm, from 'short.mkv':
  Metadata:
    ENCODER         : Lavf53.32.100
  Duration: 00:01:30.12, start: 0.000000, bitrate: 15723 kb/s
    Stream #0:0: Video: h264 (High), yuv420p, 1920x1080, SAR 1:1 DAR 16:9, 23.98 fps, 23.98 tbr, 1k tbn, 47.95 tbc (default)
    Metadata:
      title           : Tron.Legacy.3D.2010.ENG.DTS.1080p.3DBD.x264.half.SBS.z-man
    Stream #0:1(eng): Audio: dts (DTS), 48000 Hz, 5.1(side), s16, 1536 kb/s (default)
Incompatible sample format 's16' for codec 'aac', auto-selecting format 'flt'
[NULL @ 0x29717c0] Codec is experimental but experimental codecs are not enabled, see -strict -2
Output #0, adts, to 'short.aac':
  Metadata:
    ENCODER         : Lavf53.32.100
    Stream #0:0(eng): Audio: none, 48000 Hz, 5.1(side), flt, 128 kb/s (default)
Stream mapping:
  Stream #0:1 -> #0:0 (dca -> aac)
Error while opening encoder for output stream #0:0 - maybe incorrect parameters such as bit_rate, rate, width or height




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116 jumps, 48.6 minutes of freefall, 92.9 freefall miles.


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