changing audio bitrate with ffmpeg

[wallywalters]

Is it possible to write a single ffmeg command to change the audio bitrate of an AVI file? Or must I write one line to demux the audio, another to change the bitrate and then a third to remux?

I keep getting error messages when I try to do it in one line, like this:

ffmpeg -i input.avi -vcodec copy -ab 192 output.avi

Any help will be sincerely appreciated.

[poisondeathray]

you forgot to specify -acodec , and the audio bitrate is in "k" units for kbit/s

assuming you want ac3:

ffmpeg -i input.avi -vcodec copy -acodec ac3 -ab 192k output.avi

[wallywalters]

Actually I want to use MP3, which produces an error message "unknown encoder," which I don't understand because the LAME ACM is installed on my PC.

[Gavino]

Use -acodec libmp3lame

ffmpeg does not use installed codecs, only its own built-in ones.

[wallywalters]

Got it. Working now, thanks.