Re: [MMUSIC] SDPCapNeg question

[Flemming Andreasen <fandreas at cisco.com>]

Ingemar Johansson S wrote:
> Hi
>
> Reading the SDPCapNeg draft and esp. the syntax in 3.5.1 I get the idea that it is possible to formulate an SDP like
>
> m=audio 54320 RTP/AVP 0
> a=tcap:1 RTP/AVPF
> a=pcfg:1 
>
> in other words just an empty potential configuration.
>
> Even though this is close to stupidity I just want to make sure that it is possible (and no ... I don't see any use case at all). Also it does not seem to break the syntax as far as I can see in 3.5 and 3.6.
>   
It is possible, and there is a specific use case for it, as described in 
Section 3.5.1:
<quote>
  A potential configuration list is normally provided after the
  configuration number. When the potential configuration list is
  omitted, the potential configuration equals the actual
  configuration.
</quote>
Specifically what that allows you to do is change the default behavior 
of having the actual configuration always be the least preferred 
potential configuration.

Looking a Section 3.6.1, there is however some confusing text in there, 
more specifically the following:
<quote>
Each potential configuration attribute in a given
  media description MUST contain a unique configuration number and one
  or more potential configuration lists, as described in Section
  3.5.1.
</quote>


Specifically, the part saying there MUST be one or more potential 
configuration lists is incorrect per the above. I'll get that fixed to 
say "zero, one or more".

> Speaking of the [...] and (...) in the syntax , I have tried to find the document that describes these and their exact meanings, where do I find this info ?(need to make the syntax in the image attribute draft correct).
>   
That's ABNF syntax - refer to RFC 5234.

Thanks

-- Flemming
> /Ingemar
>
> ******************************************* 
> Ingemar Johansson 
> Senior Research Engineer, IETF "nethead" 
> EAB/TVP - Multimedia Technologies 
> Ericsson Research Ericsson AB 
> Box 920 S-971 28 Luleå, Sweden 
> Tel: +46 (0)8 4043042 
> ECN: 850-43042 
> Mobile: +46 (0)730 783289 
> ******************************************* 
>
>   
_______________________________________________
mmusic mailing list
mmusic at ietf.org
https://www.ietf.org/mailman/listinfo/mmusic