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ffmpeg - Audio - Audio Channels - Change Audio Channels - Stereo to Mono

Downmix both channels

ffmpeg -i "input.mkv" -ac 1 mono.mkv

WARNING: Any out of phase stereo will cancel out.

The following filtergraph can be used to bring out of phase stereo in phase prior to downmixing:

-af "asplit[a],aphasemeter=video=0,ametadata=select:key=lavfi.aphasemeter.phase:value=-0.005:function=less,pan=1c|c0=c0,aresample=async=1:first_pts=0,[a]amix"

Choose a specific channel

ffmpeg -i stereo.wav -filter_complex "[0:a]channelsplit=channel_layout=stereo:channels=FR[right]" -map "[right]" front_right.wav

NOTE: This uses the channelsplit audio filter to include only the right channel.

If you only want the left channel use FL instead of FR.

For a list of channel names, run
```
ffmpeg -layouts
```

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ffmpeg - Audio - Audio Channels - Change Audio Channels - Stereo to Mono

Downmix both channels

Choose a specific channel