Alaw file format

I’m currently working on an interface for our customers to manage music on hold.

I’m trying to make sure that all files are actually what they claim to be, and convertable by asterisk.
Eg. is the .m4a file actually a parsable m4a file (If so convert to wav then alaw), is the wav file actually a wav in a supported format, does the MP3 files have ID3tags (Some ID3 tags makes asterisk have a bad day, eg album covers)

But I can not figure out how to identify alaw files. From what I can tell the alaw files, are an asterisk invention, is there a header or similar you can use to detect if it’s a seemingly valid alaw file, or does the alaw files, just contain the raw audio stream, with no headers, or other identification?

It’s the raw audio stream.