[Mp4-tech] Encoding information in MP4 file

[Dave Singer]

In general, you need to read the spec.  Part 12 
is freely available (from www.iso.ch, 14496-12). 
The stsd box contains both the 'name(s)' of the 
codec, and their initialization.  In the case of 
AVC (H.264), you're looking for also 14496-15, 
which tells you how to find the parameter sets, 
which in turn tell you profile etc.
The ftyp box tells you what specs the file adheres to.
At 16:48  -0700 20/09/06, Adam Potolsky wrote:
>Good day,
>
>In continuing work on MP4 file, I have found 
>that there is more data that I need to gather 
>form the MP4 files and I am having difficulty 
>finding this information. In particular, I am 
>hunting down a definitive way to know the 
>specific encoding used for the video and audio 
>channel. In the case of an MPEG4-P2 track, I 
>want to know which Profile was used. (Simple 
>Profile, Advance Simple Profile, etcŠ) I have 
>looked at the 'stsd' atom and it looks like the 
>"compressor" name can be set to 0 for size so 
>this seems an unreliable source for this data. 
>In the 'ftyp' atom, there appears to be the data 
>I might be able to use, however, I'm not sure of 
>its reliability in terms of what I want.
>
>For example:
>
>... ftyp3gp6....
>3gp63g2aisomavc1
>..&.moov...lmvhd
>Š
>Š
>.....stbl....sts
>d............avc
>Š
>..*avcC.B...!..'
>B....m.... ...Dx
>7474  .....(....
>
>Uses H.264 encoding, but the 'ftyp' doesn't state that explicitly.
>
>Is there a way to tell the specific encoding box data?
>If so, how, and If not, can anyone recommend 
>another way to find this information out?
>
>Thank you in advance for you assistance,
>Adam Potolsky
>
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-- 
David Singer
Apple Computer/QuickTime