[Asterisk-Dev] video in iax2 spec

[Derek Smithies]

Steve,
my reading the paragraph (you wrote)
> 
> The packetization for everything except theora seems pretty trivial to 
> do; just take the output of the encoder, and drop it into frames. 
> Theora, however, is like vorbis, in that it has codebooks and stuff that 
> need to be sent reliably between endpoints. I might need to use an IE 
> for this kind of thing, although they could be sent in reliably 
> transmitted frames. I plan to follow the i-d for RTP packetization for 
> this, but they're changing that around a bit. (you can see my comments 
> about this in the xiph-rtp mailing list).
> 

suggests that you are intending different call handling for each different 
codec. So that Theora needs no additional packetization information added 
to the mini video frame. Other codecs need additional packetization 
information added to the mini video frames.

What happens when you are going from h323 to iax2 (with video?). My view 
is that the video packetization format chosen should make voip protocol
conversion easy. If the iax2 video packetization is codec dependendant, 
well, voip protocol conversion becomes hard.

I think the RTP header used in H323 for video works very well, and should 
be used in the video packets. Yes, I know RTP headers take up bytes.
However, given that we are sending compressed video, an extra couple of 
bytes are not going to "break the bank".

I think also that the video packetization should be as  consistant  as 
possible for the major video codecs.

Derek.

-- 
Derek Smithies Ph.D.                         
IndraNet Technologies Ltd.                
Email: derek at indranet.co.nz         
ph +64 3 365 6485                          
Web: http://www.indranet-technologies.com/