Well each codec is defined as the media attribute so for each media attribute, one can define packetization to be used. Different codec support different packetizations so they have to be defined explicitly and we cant use a session level ptime for all media attribiutes.
So how does one specify packetization in the SDP for each codec used is really my question. Lets assume a UA wants to use G723 with 30 ms packetization and G729 with 40 ms packetization. -----Original Message----- From: Bala Neelakantan [mailto:[EMAIL PROTECTED] Sent: Wednesday, May 16, 2007 4:15 PM To: 'Manpreet Singh'; sip-implementors@cs.columbia.edu Subject: RE: [Sip-implementors] ptime/Maxptime support in SDP Ptime is media attribute. It can't be specified per codec. >From 2327. a=ptime:<packet time> This gives the length of time in milliseconds represented by the media in a packet. This is probably only meaningful for audio data. It should not be necessary to know ptime to decode RTP or vat audio, and it is intended as a recommendation for the encoding/packetisation of audio. It is a media attribute, and is not dependent on charset. You can see some notes on usage of ptime in rfc3264. >From RFC 4040. Optional parameters: ptime, maxptime "ptime" gives the length of time in milliseconds represented by the media in a packet, as described in RFC 2327 [6]. "maxptime" represents the maximum amount of media, which can be encapsulated in each packet, expressed as time in milliseconds, as described in RFC 3267 [9]. Thanks, Neel > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:sip-implementors- [EMAIL PROTECTED] On Behalf Of > Manpreet Singh > Sent: Wednesday, May 16, 2007 2:22 PM > To: sip-implementors@cs.columbia.edu > Subject: [Sip-implementors] ptime/Maxptime support in SDP > > Whats the right implementation for ptime/maxptime in the SDP. I read > few recommendations but what is the correct way of doing it? > > m=audio 22836 RTP/AVP 4 18 > c=IN IP4 216.168.161.230 > a=rtpmap:18 G729/8000 > a=fmtp:18 annexb=yes;ptime=20 > a=maxptime:40 > a=rtpmap:4 G723/8000 > a=fmtp:4 bitrate=6.3;annexa=yes;ptime=30 a=maxpime:60 > > OR > > m=audio 22836 RTP/AVP 4 18 > c=IN IP4 216.168.161.230 > a=rtpmap:18 G729/8000 > a=fmtp:18 annexb=yes; > a=ptime:20 > a=maxptime:40 > a=rtpmap:4 G723/8000 > a=fmtp:4 bitrate=6.3;annexa=yes > a=ptime:30 > a=maxpime:60 > > is this how we can define ptime and maxptime per media attribute? Any > place this has been defined? > > Thanks > _______________________________________________ > Sip-implementors mailing list > Sip-implementors@cs.columbia.edu > https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors _______________________________________________ Sip-implementors mailing list Sip-implementors@cs.columbia.edu https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
