Re: [MMUSIC] RFC 5576 is da answah

[Harald Alvestrand <[e-mail]>]

On 11/22/2012 11:17 PM, Bernard Aboba wrote:
> Christer said:
>
> "My suggestion has been that "CLUE application specific data" (e.g. 
> spatial relationship information) goes into the CLUE channel, while 
> "transport data" (especially data which might be needed by 
> intermediaries etc) goes into SDP. "
>
> [BA]  That seems like a reasonable guideline to me.  Looking at 
> draft-ietf-clue-framework Section 6.1.1, many of the attributes other 
> than the "spatial relationship" ones (such as Point of Capture, Line 
> of Capture and Area of Capture) do seem like they can be handled in 
> SDP.  For example,  the max-send-ssrc:  and max-recv-ssrc: parameters 
> defined in draft-westerlund-mmusic-max-ssrc seem to communicate 
> similar information to Max Capture Encodings, and Encoding Group might 
> be taken care of via the a=ssrc-group construct in RFC 5576. Height, 
> Width and Framerate also can be handled in SDP (though IMHO the 
> negotiation mechanism in draft-lennox-mmusic-sdp-source-selection 
> needs work).
>
> [Harald]  The answer asks for *exactly* 720 by 576. The offerer has to 
> either send in that resolution or renegotiate.
> If a range was acceptable, the answerer should have indicated that 
> ([x=700:800,y=500:600]).
>
> [BA] Yes, but it seems clumsy for the receiver to indicate its 
> preferences without information on what the sender supports. In 
> draft-lennox-mmusic-sdp-source-selection, imageattr information only 
> seems to be supported in the answer, whereas in RFC 6236, the Offer 
> may include both send and receive information as described in Section 6.1:
> a=imageattr:PT send attr-list recv attr-list
> Including both send and receive information in the Offer seems more 
> likely to enable the negotiation to conclude in a single Offer/Answer 
> exchange.

So are you arguing that draft-lennox should specify "imageattr" with the 
"a=ssrc" construct as well as with the "a=remote-ssrc" construct? I 
could support that.

Sender's generic support can be indicated using 6236, but the sender 
might want to specify it per stream too.