mp4v2 doesn't support .mp3 audio data

[christ...@cbau.wanadoo.co.uk]

To reproduce: Take any .mp3 file. Open it with QuickTime Player on MacOS X 10.9. "Save" to save it - this converts it to an .mp4 file with a .mov suffix. iTunes playes it just fine. 

However, the file contains an atom "moov.trak.mdia.minf.stbl.stsd..mp3" (the last type is '.mp3', starting with a dot), which cannot be handled. 

The reason why I would like to have .mp3 files in a QuickTime file: There are lots of audiobooks that come in the form of many .mp3 files. There are apps like "AudioBook Binder" that can turn them into single file audio books with chapters, but these apps convert them to AAC format. Which is _not_ good if your original is a 32 Kbit/sec or 64 KBit/sec .mp3 file, because converting to 128 KBit AAC makes it a lot bigger, and converting to 64 KBit AAC adds another loss of quality that I'd really want to avoid. It would be a lot better if I could take the audio data unchanged (concatenating multiple .mp3 files is not really difficult). 

PS. I'm not sure how the find commands in mp4v2 would handle a string like "moov.trak.mdia.minf.stbl.stsd..mp3".