Re: [AVTCORE] Comments on draft-ietf-avtcore-rfc5285bis-03

[David Singer <[e-mail]>]

> On Oct 18, 2016, at 16:53 , Magnus Westerlund <[e-mail]> wrote:
> 
> I think there is a negotiation mechanism, in that if one include extmap mappings for values above 15, then you indicate that you support the two-byte format, and if you accept you can clearly indicate this. Maybe this should be made more explicit, as a method of determining the operations mode. To me we do now end up with four different cases:
> 
> A. One-byte only: only ID's in range 1-14. The state of a=extmap-allow-mixed has no meaning, only indication if one want to renegotiate.
> 
> B. two-byte only: only ID's above 15. The state of a=extmap-allow-mixed has no meaning, only indication if one want to renegotiate.

sorry, I don’t get this.  Two-byte headers get you full-byte length fields and thus longer payloads. You could use these with small local IDs.  Why say you have to use IDs outside 1-14???


> 
> C. one or two-byte, but no switching between within a RTP stream: No a=extmap-allow-mixed attribute, but negotiated IDs both in 1-14 as well as above 15.
> 
> D. one and two-bytes with switching: a=extmap-allow-mixed and negotiated IDs both in 1-14 as well as above 15.
> 
> Maybe the above alternatives should be made explicit to ensure that implementers understand and consider all the alternatives.

David Singer
Manager, Software Standards, Apple Inc.