Original Question

Is there some cli tool to convert aac files from the iTunes Store (no DRM) to mp3?

Update 1

MP3 to MP3

I installed libavcodec-unstripped-52 and get a little further.

When I try to encode MP3 files with it: It says [mp3 @ 0x997cde0]Header missing.

lame also had problems since the tags are ID3v2, is it possible that the libmp3lame does not support that either?

Should I convert the tags or what can I do to get this working?

AAC to MP3

This went through, but there are no headers in the resulting MP3 file. How can I get the headers in there?