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Using ffmpeg I'd like to have some directions/parameters to:

  • encode any audio file to a poor bitrate
  • strip artwork from file
  • optimize for speed
  • optimize for size

My goal is to have a bare-bone file encoded in mp3 in the fastest time possible, quality does not matter (even 96kbps or less), it just needs to be extremely fast.

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ffmpeg -i input.file -map 0:a:0 -b:a 96k output.mp3

...will convert any file with audio into a Constant Bit Rate MP3 @ 96 kbit/s. Music files normally store cover images as a video stream, which will be stripped by this command; M4A files do this differently, but ffmpeg is currently not able to access that data, so it will be stripped whatever you do. This will also select the first audio stream, if there are multiple audio streams.

CBR mode should be faster than VBR, and using a low bit rate should be faster than a higher one.

Of course, file size can be easily calculated from the bit rate. A one-minute CBR MP3 @96 kbit/s will have a file size of 60s*96000bit/s=5760000 bit, /8192=703.125 KB.

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  • I run this command with 48k bitrate, but the resulting file had a shorter duration, by about a quarter. Why does the lower bitrate distort the length of the audio?
    – Mirror318
    May 17, 2017 at 9:15
  • in my setup, the above command runs at ~15x relative speed, while the default command in the wiki: >" ffmpeg -i input.file -codec:a libmp3lame -qscale:a 2 output.mp3 " runs at ~19x relative speed; so I don't think this is the fastest way to convert. if I find any faster way I'll report back here with an answer =)
    – Vinícius M
    Aug 14, 2018 at 20:12
  • This actually made the mp3 bigger in size, what could be the reason?
    – Madeo
    Feb 25, 2020 at 6:59
  • @Madeo The reason may be the bitrate. Try with 64k
    – Patrissol Kenfack
    Oct 14, 2020 at 8:51
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One method:

ffmpeg -i in.mp3 -b:a 96k -map a out.mp3

-map a strips artwork.

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