M4aToMp3

Using FFMPEG to convert M4a to Mp3 from a gist at https://gist.github.com/christofluethi/646ae60d797a46a706a5

given a directory of directories of m4a files, convert and pack to mp3

buggy, leaves the output file as ".mp3" in the subdirectory, not as a properly named thing in the root.

for DIR in */; do

    cd "$DIR"

    for SRC in *.m4a; do

       BASE=${SRC%'.m4a'}    
       DEST=$( printf "%s.mp3" "$BASE")
       ffmpeg -y -i "$SRC" -codec:a libmp3lame -q:a 0 "$DEST" >/tmp/ffmpeg.log 
    done

    printf "file '%s'\n" *.mp3 > mylist.txt
    ffmpeg -f concat -safe 0 -i mylist.txt -c copy "../$DIR.mp3"
    cd ..
done

brew update
brew link yasm
brew link x264
brew link lame
brew link xvid

brew install ffmpeg

ffmpeg wiki: 
https://trac.ffmpeg.org/wiki/Encode/MP3

lame option 	Average kbit/s 	Bitrate range kbit/s 	ffmpeg option
-b 320 	320 	320 CBR (non VBR) example 	-b:a 320k (NB this is 32KB/s, or its max)
-V 0 	245 	220-260 	-q:a 0 (NB this is VBR from 22 to 26 KB/s)
-V 1 	225 	190-250 	-q:a 1
-V 2 	190 	170-210 	-q:a 2
-V 3 	175 	150-195 	-q:a 3
-V 4 	165 	140-185 	-q:a 4
-V 5 	130 	120-150 	-q:a 5
-V 6 	115 	100-130 	-q:a 6
-V 7 	100 	80-120 	-q:a 7
-V 8 	85 	70-105 	-q:a 8
-V 9 	65 	45-85 	-q:a 9

ffmpeg -i in.m4a -codec:a libmp3lame -qscale:a 1 out.mp3