Re: AW: [AVT] RE: [MMUSIC] questions about grouping media streams in RTPand SDP (RFC3388 etc), advice needed

[Randell Jesup <rjesup at wgate.com>]

Dave Singer <singer at apple.com> writes:
>At 10:10  +0300 10/06/07, Even, Roni wrote:
>>I understand that you intend to send two media streams using two m lines
>>without grouping and any specific semantics to identify the stream.
>>Our experience is that if you have two video m lines you can not know
>>which one the other will pick if he does not understand the relation
>>between the streams.

>you keep missing that the streams have attributes that tell me which is which.
>
>m=video
>a=fmtp: yes this is a foobar primary stream
>m=video
>a=fmtp:yes this is a foobar repair stream
>
>if I see such an SDP with only one foobar primary and only one foobar
>repair, it's fairly clear that the foobar repair stream is associated with
>the foobar primary stream, without needing grouping.

Roni's point was really not that *you* wouldn't be able to tell, but that
some other UA (which "does not understand the relation beween the streams")
could/would mis-interpret the SDP.  This of course assumes they think at
least one payload for each stream is something they know how to
send/receive.

That's also a problem with the current grouping RFC (along with the
chicken-and-egg syndrome).

-- 
Randell Jesup, Worldgate (developers of the Ojo videophone), ex-Amiga OS team
rjesup at wgate.com
"The fetters imposed on liberty at home have ever been forged out of the weapons
provided for defence against real, pretended, or imaginary dangers from abroad."
		- James Madison, 4th US president (1751-1836)


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