Re: [MMUSIC] Open Issues: draft-ietf-mmusic-sdp-simulcast-03

[Christer Holmberg <[e-mail]>]

Hi,

...

> Also, I have some other issues:
> - syntax allows two sends, or two recvs, but those are semantically forbidden
> - the syntax allows paused with PTs, but that is semantically forbidden.
> - syntax allows pt values that aren't numeric
> - use of WSP (SP or HTAB). Contrary to typical SDP usage.

I believe use of WSP is forbidden in SDP.

> Below is a proposal for revised syntax that follows the spirit, but aligns better 
> with other attributes and 4566bis. It doesn't have some of the extensibility of 
> the prior syntax because I couldn't see how to do it in a meaningful way. I don't think it is a great loss here.
>
> ...
>
> 6.1 Simulcast attribute
>
>    Name: simulcast
>
>    Value: simulcast-value
>
>    Usage Level: media
>
>    Charset Dependent: no
>

I think it would also be good to indicate the multiplex group.

>    Syntax:
>
>       simulcast-value = sc-send-opt [SP sc-recv-opt]
>                       / sc-recv-opt
>       sc-send-opt = "send" SP sc-sendrecv-args
>       sc-recv-opt = "recv" SP sc-sendrecv-args
>
>       sc-sendrecv-args = sc-pt-args / sc-rid-args
>       sc-pt-args = "pt=" sc-pt-list *(";" sc-pt-list)
>       sc-rid-args = "rid=" sc-rid-list *(";" sc-rid-list)
>                     [SP sc-pause-opt]
>
>       sc-pt-list = payload-type *("," payload-type)
>       sc-rid-list = rid-identifier *("," rid-identifier)
>       sc-pause-opt = "paused=" sc-rid-list
>
>       ; SP defined in [RFC5234]
>       ; payload-type, defined in [draft-ietf-mmusic-rfc4566bis-15]
>       ; rid-identifier defined in [I-D.pthatcher-mmusic-rid]
>
>    Examples:
>
>       a=simulcast: send pt=97;98 recv pt=97
>       a=simulcast: send rid=1,2,3 recv rid=4 paused=3

Looks good.

Regards,

Christer