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

[Dave Singer]

The MP4 file format has all you need in various tables, including 
decoder setup information.  I'm kinda surprised you can get the data 
out without knowing the tables and their meaning, unless there is 
only the one audio track (whereupon it's possible you'll get lucky 
and the aac frames are contiguously stored in time order).
The other file formats you mention have little or no relation to MP4.
At 10:33  +0800 2/08/05, yipan wrote:
>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!
>
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-- 
David Singer
Apple Computer/QuickTime