Re: [MMUSIC] SDP grouping in a new offer

[Christer Holmberg <[e-mail]>]

Hi,

In my opinion the grouping framework does not change the at-least-N-m=-lines rule.

...which is probably why 5888 doesn't mention it.

Regards,

Christer

________________________________
From: [e-mail] [[e-mail]] On Behalf Of Muthu Arul Mozhi Perumal (mperumal) [[e-mail]]
Sent: Thursday, July 05, 2012 2:47 PM
To: mmusic
Cc: Raghavendra S (raghs); Toleti Danayya Naidu (naidud); Dinesh V (dinv)
Subject: [MMUSIC] SDP grouping in a new offer

Experts,

RFC3264 states that:

   If an SDP is offered, which is different from the previous SDP, the
   new SDP MUST have a matching media stream for each media stream in
   the previous SDP.  In other words, if the previous SDP had N "m="
   lines, the new SDP MUST have at least N "m=" lines.  The i-th media
   stream in the previous SDP, counting from the top, matches the i-th
   media stream in the new SDP, counting from the top.  This matching is
   necessary in order for the answerer to determine which stream in the
   new SDP corresponds to a stream in the previous SDP.  Because of
   these requirements, the number of "m=" lines in a stream never
   decreases, but either stays the same or increases.  Deleted media
   streams from a previous SDP MUST NOT be removed in a new SDP;
   however, attributes for these streams need not be present.

>From section 9.1 of RFC5888, it seems the same is applicable with SDP grouping, but is not explicit. Should there be matching m-lines in the new offer even with SDP grouping? Does SDP grouping change anything w.r.t to the above statements in RFC3264?

thanks,
Muthu