Super User is a question and answer site for computer enthusiasts and power users. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

How can I use ffmpeg to isolate one channel from an audio file? I have a stereo audio file, and I need the output to be the contents of the right channel in a mono audio file.

While I'm sure it's fairly easy to do, I can't figure it out. Thanks for the help!

share|improve this question
up vote 8 down vote accepted

You have two methods:


You can use the -map_channel option:

ffmpeg -i stereo.wav -map_channel 0.0.1 right_mono.wav
  • The first 0 is the input file id
  • The next 0 is the stream specifier
  • The 1 is the channel id

So this can be translated as: first file, first stream, second channel (or right channel).

From the -map_channel documentation:

The order of the -map_channel option specifies the order of the channels in the output stream. The output channel layout is guessed from the number of channels mapped (mono if one -map_channel, stereo if two, etc.

pan audio filter

You could also use the pan audio filter:

ffmpeg -i stereo.wav -af pan=1:c0=c1 right_mono.wav
  • 1 is output channel layout or number of channels
  • c0=c1 is the "outdef", or output channel specification
  • c0 represents the desired output channel number
  • c1 represents the input channel to use

Make sure to read the pan documentation first.

share|improve this answer
Interstingly, on FLAC/WAV files -map_channel is nearly instantaneous saying "Pure channel mapping detected". – Louis May 31 '13 at 18:36
@Louis See Remapping examples for an explanation of "Pure channel mapping detected". – LordNeckbeard May 31 '13 at 18:46
Ah nice, so pan seems superior in that it can do pure channel mapping on lossy files too. – Louis May 31 '13 at 18:53
@Louis I think it should be the same. The console output of the -map_channel example shows, -map_channel is forwarded to lavfi similarly to -af pan=0x4:c0=c1, and the md5 muxer shows that the streams are the same. I don't quite understand 0x4 though. – LordNeckbeard May 31 '13 at 19:56

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.