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Short version of the question: is there any protocol in AAC or MP3 file type that allows for internal looping of an audio file?

Now for the explanation:

This is a curious situation I've run into. One of my main jobs I do is to produce 10hour ambient sounds for a Sleep Sound business (run by an old friend of mine). These 10hour sounds are comprised of a 7-20minute sound looped continuously for 10hours (to ensure it plays all night long). We use various digital mediums to sell our products.

Unfortunately, we're running into an issue with iTunes and the increasingly popular iCloud, which requires all audio files be under 200MB. Even at 128kbps, a 10hour mp3 is about 550MB. I ran the calculations, and we'd have to drop to below 45kbps to be under the limit! Obviously that's not an option. So, to come back to my original question, is there a popular audio compression file format (AAC/MP3) that has builtin protocols for looping audio? From my few readings, it seems that AAC is fairly sophisticated, and just might.

Obviously, this has to play correctly across all major platforms and devices, so things like OGG and FLAC would be out of the question.

Are you giving up on having a 10 hour long compressed audio file? And you are looking for a way to deliver something that will have a small footprint, but loop for the right amount of time.

Does it have to play in iTunes?

Would it be possible to create a Garageband file-- with all your loops in there? That would be small, and could run for 10 hours (theoretically). Garageband is a free app, so folks could install it, but it's not exactly a small request to ask your customers to install something that big.

Is there a browser-based sound-generating thing, where you put your sample loops into soundfonts, then use a browser to play a MIDI file that triggers that is playing the soundfonts player?

Yes, I was thinking REX files, or Apple Loops, but neither are playable across platforms.

Most notably, the need to play in iOS, iTunes, Android, and Windows and be idiot proof. That's been the problem, some of our customers who are using iCloud keep getting their files denied and they don't know what to do about it.