transcoding music

M4A (AAC) to MP3

The faad program is what is supposed to be used to play M4A files, but it seemed to not work with all of mine. MPlayer seems to be better. Unfortunately, MPlayer can't output the decoded PCM data to stdout, so to achieve parallel decoding/encoding, a named pipe is necessary. This is like a pipe on the command line except that it has a filename.

mkfifo tmp.pipe
mplayer -noconsolecontrols -ao pcm:file=tmp.pipe whatever.m4a &
lame --preset standard tmp.pipe whatever.mp3
rm -f tmp.pipe

Substitute your preferred lame flags.

To do all files in a directory recursively:

mkfifo tmp.pipe
find . -name "*.m4a" | while read filename
do
    mp3_filename=`basename "$filename" ".m4a"`.mp3
    mplayer -noconsolecontrols -ao pcm:file=tmp.pipe "$filename" &
    lame --preset standard tmp.pipe "$mp3_filename"
done
rm -f tmp.pipe

Add -maxdepth 1 to find's arguments to be non-recursive.

FLAC to MP3

A little simpler. Here's the recursive version:

find . -name "*.flac" | while read filename
do
    mp3_filename=`basename "$filename" ".flac"`.mp3
    flac -dc "$filename" | lame --preset standard - "$mp3_filename"
done

update: actually, why not use mplayer for every source format?

Hey.. good idea. I also made a script that parallelizes and put it on github.