[Mp4-tech] How to indentify the AAC format in a .mp4 file?

[yipan]

Hello all:
     I am recently decoding an .mp4 file. And the audio is encoded with AAC.
     I konw there are three formats for AAC, namely ADTS, ADIF and RAW
format. Unfortunately, I can't find the identification both for ADTS
and ADIF, by extracting the AAC audio stream to an .aac file with each
fream added ADTS header, it works.
So I guess the AAC audio reside in my testing .mp4 file is in RAW
format. But is there any side information in the .mp4 file can tell me
this, without ADIF or ADTS header, I can't decide the parameters like
sample rate, sample size and so on.
     Thanks!