[Mp4-tech] Encrypting AVC encoded elementary streams with ISMACryp

[Dave Singer]

I forgot to say in my previous reply, that there 
is no esds for AVC.  There may be the optional 
boxes from the AVC spec, of course (which would 
stay).  A typical transform looks like (thanks to 
a friend from the ISMA):
For AVC:     'stsd'
                             'avc1'
                                     ... (other fields)
                                     'avcC'
For encrypted AVC: 'stsd'
                                         'encv' 
(all the fields of 'avc1' are preserved except 
the 4CC 'avc1' which becomes 'encv')
                                                 ...
                                                 'avcC'
                                                 'sinf'
                                                         'frma'
                                                                 field = '264b'
                                                         'schm'
                                                                 type = 'iAEC'
                                                                 version = '1'
                                                         'schi'
                                                                 'iKMS'
                                                                         ...
                                                                 'iSFM'
                                                                         ...
                                                                 'iSLT
                                                                        ...
The other thing I meant to say is that ISMA is 
recommending, in ISMACryp 1.1, that the 
byte-stream (start-code) structure of AVC be used 
when encrypted, as it enables finding NALu 
boundaries after loss.  This explains why my 
colleague has 264b, and not avc1, in the original 
format box.
At 15:43  +0100 1/12/05, Cengiz Tas wrote:
>Hi all,
>
>I have integrated AVC/H.264 ISMACryp support within the mpeg4ip project and
>encountered the following problem:
>
>According to the ISMACryp spec the mp4v box of an encrypted MPEG-4 Video
>(simple) has to be substituted with the encv box with the esds box as child,
>etc. When creating AVC-Content I have an avc1 box with avcC as child and no
>esds box anymore. How does the box structure for an ISMA encrypted AVC file
>looks like? I have an idea but couldn´t find any information in the specs.
>Is it sufficient to create the encv box with the avc1/avcC boxes as
>children? Or do I have to add the esds box, too ?
>
>example:
>
>...
>stbl
>stsd
>encv
>avc1
>avcC
>...
>
>
>Thanks for your help.
>
>Cengiz.
>
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-- 
David Singer
Apple Computer/QuickTime