Combining audio files without reencoding

Hi,


I'm looking for a solution to combine multiple AAC encoded m4a files (with the same bitrate) into a bigger m4a / m4b file.

Currently all the sample code I could find is basically uncompressing the audio stream and then recompressing.


My understanding is that the mp4 container conatins atoms with the samples and I'd just have to append them to a new container, adjust the length information / metadata and that's it. Is there any API to do that - like in the old days the lower level Quicktime APIs allowed?


Thanks!