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 audio.ext

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
  • What's your full command?
    – Gyan
    Jun 12, 2019 at 10:51

1 Answer 1


A map option will select all streams matched by the specification. The 'best' stream is only selected in the absence of any map options.

So, you'll need a two-stage process to do this:

ffmpeg -i in.mkv -map 0:a:m:language:eng -vn -acodec copy -f nut - | ffmpeg -f nut -i - -c copy output.flac

The first ffmpeg process sends all English language audio streams to the 2nd ffmpeg process, which will select only the 'best' among the received streams for output.

If you want to keep metadata, and not worry about the codec of the input file, you can change your output to .mkv

  • That's the 'file format' set for the piped data. ffmpeg generally detects the format based on the extension of the output file. There's none specified by - so we have to set one. -f matroska would work as well but nut supports finer timestamps so I prefer that.
    – Gyan
    Jun 12, 2019 at 12:15
  • nut is not really necessary here, just a habit for me. ffmpeg can't auto-supply extension.
    – Gyan
    Jun 12, 2019 at 12:30
  • I've added this to your answer so is more relevant to others. Thanks so much! I'll cleanup old comments
    – Freedo
    Jun 13, 2019 at 8:36
  • Trying to adapt this to subtitles doesn't work. Any idea why? -map 0:s:m:language:eng -vn -scodec copy -f nut - | ffmpeg -f nut -i - -c:s srt "${file%.mkv}".eng.srt
    – Freedo
    Dec 28, 2019 at 6:43
  • Share full log.
    – Gyan
    Dec 28, 2019 at 7:10

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