Is there an m4v file format specification?

Hi folks.

Does anyone know where I can find a specification or authoritative documentation for the M4V file format that Quicktime, iTunes, and other Apple products support? Or something that describes its differences, if any, from the MP4 file format?

I'm trying to fix an issue with VLC producing .m4v files that don't have their audio streams recognized.

There are many places on the Internet, including Wikipedia, that just say "M4V is the same as MP4" or "M4V is like MP4 but somewhat different" but none of them have references to any documentation from Apple or another authoritative source.