Say you input has 2 english audio tracks, 7.1 and 2.0.
You want to copy the audio track of highest quality (number of channels) to
If I use
-map 0:m:language:eng it selects all english audio tracks where I thought by default it would only copy the highest channel audio track.
ffmpeg -i *mkv -map 0:m:language:eng -vn -acodec copy output.flac