This is fantastic.

For folks wanting to play around with this on OSX:

brew install ffmpeg lame brew install sox --with-lame

The --with-lame is important if you want to process mp4s.

Might want to consider putting some kind of progress indicator (simple polling on tmp_audio_in.u8 vs tmp_audio_out.u8). I ended up looking at the output directory with

watch -n .5 ls -la /tmp/audio_shop-DIRECTORY

I think the cleanup isn't working quite right, getting a rm unlink failure.

Seriously, this is a neat hack.