Howto convert audio files to *.m4a?
Solution 1:
I'd stick with ffmpeg. You weren't far off. Here's what I've just used to convert a load of 50-meg flacs to 5-meg m4as, complete with metadata:
find -name "*.flac" -exec ffmpeg -ab 192k -i "{}" -map_meta_data "{}.m4a":"{}" "{}.m4a" \;
You could expand that to clean up the original files or save them somewhere else (I was actually struggling with that bit).
For some reason, mine was crawling along at 190kbits/s so there might be a better encoding string (I should hope there is, this is a bit silly).