[AVT] Re: Comments on draft-ietf-avt-rtp-vc1-01

Hi Anders,

See inline.

Anders Klemets wrote:
> As for adding additional SDP parameters to support the SIP
> "offer/answer" feature, I wonder if it is a requirement these days that
> all new RTP payload formats should come with built-in support for this
> functionality?  Or is this something that could be defined at a later
> date, by the appropriate SIP working group?

No, you don't usually add extra parameters for offer/answer. The 
parameters I was discussing was what is needed to support any 
bi-directional usage basically.

What we do require is to describe how the payload format parameters will 
be used in offer/answer (RFC 3264). And no, we don't offload this work 
to any SIP groups and it is needed for all formats.

If we wouldn't define offer/answer considerations you end up with 
discussions like the one around RFC 3016 and how to interpret the 
parameters. It is also very good to think how different parameters 
actually will be used. That way they will be defined in a way that is 
more useful.

> 
> If we were to omit "offer/answer" from this spec, does it need to
> mention that IANA maintains a registry of MIME/SDP parameters?  Colin's
> comment seemed to suggest that it is necessary to mention this.  The
> spec already mentions that IANA should register "video/vc1".  Doesn't
> that imply that IANA will also register any additional MIME parameters
> that the IETF may want to define in the future?

The question Colin made was if any of the payload format parameters has 
a specific value space that could be extended in the future. Examples of 
this is the color-space and sampling used in RFC 4175.

> 
> As for the numbering of the headings and the title headings being split
> into separate lines, I don't know why that happened. The document that I
> e-mailed to internet-drafts@ietf.org does not have that problem.  Would
> they have edited the document for some reason?

No, not likely. It might be some character encoding issues. If you used 
Word to produce the draft it is common to end up with characters that 
aren't in the 7-bit ascii set.

Cheers

Magnus Westerlund

Multimedia Technologies, Ericsson Research EAB/TVA/A
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