Christer, I believe Attila is correct. To do it the way you suggest would mean each ptime attribute would need to be position sensitive to match up with the appropriate codec. This behavior is not described anywhere in RFC2327, and would need to be for implementations to be interoperable. There are also some mentions of ptime handling in RFC3264, and they do not suggest this behaviour. Those mentions appear to indicate one ptime attribute associated with one stream.
This issue has been discussed a few times before on mmusic, it may be more appropriate to continue the discussion there if needed. I think the bottom line is most implementations probabally associate one ptime attribute to one m line. The only way to get different ptimes for a stream is to omit the attribute completely when specifying multiple codecs with different default times, such as G711 & G723. May have to wait for sdpng to do this as desired. John Hearty Level3 > -----Original Message----- > From: Christer Holmberg [mailto:[EMAIL PROTECTED] > Sent: Sunday, March 23, 2003 11:20 AM > To: Attila Sipos > Cc: [EMAIL PROTECTED]; link.xie; 'Christian Stredicke'; > [EMAIL PROTECTED] > Subject: Re: [Sip-implementors] SDP packet times for muliple codecs > > > > Hi, > > Which "rules" are you refering to? RFC2327 does say ptime is a media > attribute, but I can't find anywhere said that you can't > specify separate > values for specific codecs (using it together with rtpmap). > Please tell me if > I'm wrong. > > Regards, > > Christer Holmberg > Ericsson Finland > > > > I think the problem is that (according to the rules) the ptime > > attribute is not related to a specific profile but to a specific > > media description: > > > m=audio 10000 RTP/AVP 0 8 > > > a=rtpmap: 0 PCMU/8000 > > > a=ptime:20 > > > a=rtpmap: 8 PCMA/8000 > > > a=ptime:30 > > > > So I guess, officially, you can only really have one ptime parameter > > associated with each "m=" line. > > Personally I can't see why we couldn't use multiple packet times > > in the way you suggested but maybe it'll break some implementations. > > I don't know. > > > > As a recap, I remember the various other proposals to > handle the multiple > > profiles: > > m=audio 10000 RTP/AVP 0 8 > > a=mptime:20 30 > > a=rtpmap: 0 PCMU/8000 > > a=rtpmap: 8 PCMA/8000 > > > > or: > > m=audio 10000 RTP/AVP 0 8 > > a=x-ptime:20 30 > > a=rtpmap: 0 PCMU/8000 > > a=rtpmap: 8 PCMA/8000 > > > > I have another idea: be explicit about the packet times used > > for each profile (like with rtpmap): > > > > m=audio 10000 RTP/AVP 0 8 > > a=rtpmap: 0 PCMU/8000 > > a=rtpmap: 8 PCMA/8000 > > a=ptimemap: 0 20 > > a=ptimemap: 8 30 > > > > But, as you can see, it's less efficient that the mptime > > or x-ptime parameters. > > > > Can anyone say how far away we are before all this > > "mulitple packet time" stuff is standardised? > > > > Attila > > > > > -----Original Message----- > > > From: Christer Holmberg [mailto:[EMAIL PROTECTED] > > > Sent: 19 March 2003 22:43 > > > To: [EMAIL PROTECTED] > > > Cc: link.xie; Attila Sipos; 'Christian Stredicke'; > > > [EMAIL PROTECTED] > > > Subject: Re: [Sip-implementors] SDP packet times for > muliple codecs > > > > > > > > > > > > Hi, > > > > > > Why don't you use normal RTPMAP stuff, without any extensions > > > and/or x- > > > parameters? > > > > > > Your SDP would look like: > > > > > > m=audio 10000 RTP/AVP 0 8 > > > a=rtpmap: 0 PCMU/8000 > > > a=ptime:20 > > > a=rtpmap: 8 PCMA/8000 > > > a=ptime:30 > > > > > > Or, have I missunderstood your issue? > > > > > > Regards, > > > > > > Christer Holmberg > > > Ericsson Finland > > > > > > > > > > > > [EMAIL PROTECTED] wrote: > > > > > > > Hi all, > > > > > > > > I think Link.xie is right that till the attribute is > > > > registered 'X-mptime' should be the attribute name used. > > > > > > > > Though, we should move towards standardizing this > > > > attribute in a draft.... because chances are other > > > > implementations will not understand this unregistered > > > > attribute and may lead to inter-op issues later. > > > > PacketCable seems to have taken a step forward already > > > > in this regard. > > > > > > > > PS: Some more digging into the archive shows that we did > > > > agree to bring out a draft on the 'mptime' attrib > > > > for exactly the same reason.... Perhaps Kevin and > > > > Colin could tell if one is already on its way :) > > > > Else we can prepare one now ? > > > > > > > > (ref: > > > > > > > http://www1.ietf.org/mail-archive/working-groups/mmusic/curren > > > t/msg01030.ht > > > > ml) > > > > > > > > Cheers, > > > > Siddharth. > > > > > > > > -------------------------------------------------------- > > > > Siddharth Toshniwal > > > > Hughes Software Systems > > > > Prestige Opal http://www.hssworld.com > > > > 146, Infantry Road Ph (O): +91-80-2286390 (7094) > > > > Bangalore-560001, India Mobile: +91-9845154068 > > > > -------------------------------------------------------- > > > > > > > > "link.xie" <[EMAIL PROTECTED]> on 03/12/2003 04:49:12 PM > > > > > > > > To: "Attila Sipos" <[EMAIL PROTECTED]>, "'Christian > > > Stredicke'" > > > > <[EMAIL PROTECTED]> > > > > cc: [EMAIL PROTECTED] (bcc: Siddharth J > > > Toshniwal/HSSBLR) > > > > > > > > Subject: Re: [Sip-implementors] SDP packet times for > muliple codecs > > > > > > > > I think X-mptime is better. Cause in rfc2327, > > > > "Unregistered attributes should begin with "X-" to > > > prevent inadvertent > > > > collision with registered attributes" > > > > > > > > ----- Original Message ----- > > > > From: "Attila Sipos" <[EMAIL PROTECTED]> > > > > To: "'Christian Stredicke'" <[EMAIL PROTECTED]>; "'link.xie'" > > > > <[EMAIL PROTECTED]>; "Attila Sipos" <[EMAIL PROTECTED]> > > > > Cc: <[EMAIL PROTECTED]> > > > > Sent: Wednesday, March 12, 2003 4:44 PM > > > > Subject: RE: [Sip-implementors] SDP packet times for > muliple codecs > > > > > > > > > > > > > > Hello all, > > > > > > > > > > Link Xie, thanks for your response: > > > > > > > m=audio 10000 RTP/AVP 0 8 > > > > > > > a=X-ptime: 20 30 > > > > > > > > > > Following Siddharth's link > > > > > > > > > > > > http://lists.cs.columbia.edu/pipermail/sip-implementors/2003-F > > > ebruary/00455 > > > > 6 > > > > > .html > > > > > > > > > > It seems that from this link the answer is to use "mptime": > > > > > > > > > > >So instead of redefining ptime, create a new "mptime" > > > parm that has a > > > > > >construct similar to the m line: > > > > > > > > > > > >m=audio 49170 RTP/AVP 0 4 18 > > > > > >A=mptime:10 30 30 > > > > > > > > > > > > > > > > The packetcable spec (from > > > http://www.packetcable.com/specifications/ ) > > > > > > > > http://www.packetcable.com/downloads/specs/PKT-SP-EC-MGCP-I06- > > > 021127.pdf > > > > > also seem to use mptime: > > > > > > > > > > (taken from PacketCable(tm) Network-Based Call > Signaling Protocol > > > > > Specification) > > > > > > > > > > m=audio 3456 RTP/AVP 96 97 0 > > > > > a=rtpmap:96 G726-32/8000 > > > > > a=rtpmap:97 telephone-event/8000 > > > > > a=mptime: 10 - 10 > > > > > > > > > > Here, rfc2833 doesn't have a packet time so it's > shown with a '-' > > > > > (rfc2833 is supposed to have the same packet time as > the selected > > > > > audio codec). > > > > > > > > > > > > > > > Which is correct mptime or X-ptime? > > > > > > > > > > > > > > > Regards, > > > > > > > > > > Attila > > > > > > > > > > > > > > > > -----Original Message----- > > > > > > From: Christian Stredicke [mailto:[EMAIL PROTECTED] > > > > > > Sent: 12 March 2003 08:31 > > > > > > To: 'link.xie'; 'Attila Sipos' > > > > > > Cc: [EMAIL PROTECTED] > > > > > > Subject: AW: [Sip-implementors] SDP packet times for > > > muliple codecs > > > > > > > > > > > > > > > > > > The "X-" is a bad idea. We were using this in another > > > > > > scenario and many > > > > > > SDP parsers complained about "x-" headers. Better use > > > > > > something without > > > > > > "x-" (e.g. "xptime"). > > > > > > > > > > > > Christian > > > > > > > > > > > > > -----Urspr > > > > > > > > > > > -------------------------------------------------------------- > > > ---------- > > > > > > > > �ngliche Nachricht----- > > > > > > > Von: [EMAIL PROTECTED] > > > > > > [mailto:sip-implementors- > > > > > > > [EMAIL PROTECTED] Im Auftrag von link.xie > > > > > > > Gesendet: Mittwoch, 12. M�rz 2003 03:46 > > > > > > > An: Attila Sipos; [EMAIL PROTECTED] > > > > > > > Betreff: Re: [Sip-implementors] SDP packet times for > > > muliple codecs > > > > > > > > > > > > > > Hi,Attila > > > > > > > I think your suggestion is wrong. We also use > > > this solution > > > > > > before. > > > > > > > But we find that the meaning of 2 "m=" line repesent > > > 2 media stream. > > > > > > So > > > > > > > it's not suitalbe for this case. > > > > > > > Our solution is introducing a new attribut "X-mptime" > > > > > > which means > > > > > > > multiple ptime > > > > > > > and the SDP would like: > > > > > > > > > > > > > > m=audio 10000 RTP/AVP 0 8 ----- 0 means g711u-law > > > > > > and 8 means > > > > > > > g711a-law > > > > > > > a=X-ptime: 20 30 -----20 for > > > > > > g711u 30 for > > > > > > > g711a > > > > > > > > > > > > > > I think this can solve your problem > > > > > > > > > > > > > > Best Regard > > > > > > > Link.Xie > > > > > > > ----- Original Message ----- > > > > > > > From: "Attila Sipos" <[EMAIL PROTECTED]> > > > > > > > To: <[EMAIL PROTECTED]> > > > > > > > Sent: Tuesday, March 11, 2003 7:33 PM > > > > > > > Subject: [Sip-implementors] SDP packet times for > > > muliple codecs > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Hello everyone, > > > > > > > > > > > > > > > > For multiple codecs we can have an SDP like this: > > > > > > > > m=audio 10000 RTP/AVP 0 8 ----- 0 means > > > g711u-law and 8 means > > > > > > > g711a-law > > > > > > > > a=ptime:20 > > > > > > > > But this is only correct if the packet times match for > > > > > > > > u-law and a-law. > > > > > > > > > > > > > > > > > > > > > > > > What if you have a system where, for some reason, the > > > > > > > > codecs have different packet times? > > > > > > > > > > > > > > > > Can you do this? > > > > > > > > m=audio 10000 RTP/AVP 0 - ---- g711-ulaw > > > > > > > > a=ptime:20 > > > > > > > > m=audio 10000 RTP/AVP 8 ---- g711 a-law > > > > > > > > a=ptime:30 > > > > > > > > > > > > > > > > Regards, > > > > > > > > > > > > > > > > Attila > > > > > > > > > > > > > > > > <http://www.vegastream.com> > > > > > > > > VegaStream : A World of difference for your Integrated > > > > > > Communications > > > > > _______________________________________________ > Sip-implementors mailing list > [EMAIL PROTECTED] > http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors > _______________________________________________ Sip-implementors mailing list [EMAIL PROTECTED] http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
