title: Panning all audio channels center in ffmpeg?
body: <p>I am using FFMPEG to transcode a large file to a smaller file.  Usually the files will have 2 audio channels (though not always). I am trying to center all audio channels.</p>
  
  <p>I asked over at the ffmpeg-users for examples of how to do this: <a href="http://ffmpeg-users.933282.n4.nabble.com/Panning-audio-channels-example-td4417939.html" rel="nofollow">http://ffmpeg-users.933282.n4.nabble.com/Panning-audio-channels-example-td4417939.html</a></p>
  
  <p>What I got from the replies is that FFMPEG has yet to implement audio filters.  Somehow I should be able to set up a libav filter (?) to pan all channels center... something to the effect of: 
  <code>pan="c0=0.5*FL+0.5*FR"</code> though when I do this, I get the error: <code>No such filter: 'pan'</code>. Those guys are great but I can't figure this out by reading the <a href="http://ffmpeg.org/ffmpeg.html" rel="nofollow">docs</a>.</p>
  
  <p>I have not disabled filters, here is my build info
  <code>configuration: --prefix=/opt/local --enable-gpl --enable-postproc --enable-swscale --enable-avfilter --enable-libmp3lame --enable-libvorbis --enable-libtheora --enable-libdirac --enable-libschroedinger --enable-libopenjpeg --enable-libxvid --enable-libx264 --enable-libvpx --enable-libspeex --mandir=/opt/local/share/man --enable-shared --enable-pthreads --cc=/opt/local/bin/gcc-apple-4.2 --arch=x86_64 --enable-yasm --enable-nonfree --enable-libfaac</code></p>
  
  <p>Here is an example of one of my built command lines: <code>ffmpeg -i inMovie.mov -acodec libfaac -ab 64k -vcodec libx264 -vpre medium -b 320k -pass 1 -s 374x210 -threads 0 outMov.mp4</code></p>
  
  <p>I've got the rest of my FFMPEG command line working great... Essentially what I am looking for is to have left/right audio channels both have the same audio in the output file.  If there is an easier way to do this (convert to 2 mixed mono channels?) I am all ears!!</p>
  
  <p>Thank you for your help!</p>