Re: [AVT] I-D ACTION:draft-ietf-avt-rtp-h264-05.txt

>  > >- In the encoding considerations for the MIME type, may wish to note
>>  > that file formats are defined elsewhere?
>>
>>  The problem here is that all file formats are still in their
>>  specification phase -- we can't reference them (yet).  And what good
>>  would a simple "elsewhere" do?
>
>Questions about the lack of a file format have been raised during IESG
>review of other RTP payload formats. Noting that the formats are being
>defined elsewhere will avoid the question later.

Then perhaps it is appropriate to say a little more.

MPEG has defined the storage of AVC/H.264 content in ISO-family 
files, and that specification is published.  It's not expected to be 
used standalone, of course, as video is rarely found standalone 
(usually with audio).  So this does define the storage of AVC in MP4, 
3GP, 3GP2 and so on.  RTP packetization of this format shouldn't be 
excessively problematic, as it stores whole NAL Units in the same 
form as the RTP payload, and hint tracks can also be used if 
appropriate to pre-compute packetization.

The packing of AVC/H.264 into MPEG-2 transport streams is also 
defined, so it is also possible to encounter MPEG-2 
transport-streams-frozen-on-disk which contain H.264.  The RTP 
packetization of those would involve changing the NAL Units from 
start-code to length-fields, and I expect other operations.

Would text like this help?
-- 
David Singer
Apple Computer/QuickTime

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