On Monday 03 October 2005 05:01, Gummadidala, Ravi wrote: > I know that this has been discussed in the past but I am not sure what the > conclusion/concensus was. The question is whether attributes like ptime are > codec-specific or media specific? Some people have argued that these are > media specific properties and it is invalid for a SDP m line to have > multiple ptime values. The other school of thought claims that ptime is a > codec specific attribute. I am also inclined to go with the latter. Say in > the m line a UA advertises support for EVRC and G723. EVRC is a 20ms frame > based codec while G723 is a 30ms frame based codec. How should such an SDP > be formulated if it is invalid to have multiple ptimes in a media line?
Cite from RFC 2327: a=ptime:<packet time> <...> It is a media attribute, and is not dependent on charset. As the behavior for multiple unequal attributes per media line is not defined, the result from such an offer is also undefined. (E.g. what happens when someone offers multiple a=fmtp:... for two different out of band DTMF offers?) So in my opinion you would have to have one m line for each new ptime value. Regards Nils _______________________________________________ Sip-implementors mailing list [email protected] http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
