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
