I don't know whether to blame IETF or the authors who write the RFC for SDP. They simply write and IETF also just accepts it and end users need to mock their brain with this stupid standards.
Every codec has its own ptime. I don't know how they made it per media instead of percodec. If at all defined by ITU it would have been much clearer. IETF going crazy. Regards, Kannaiyan ----- Original Message ----- From: "Manpreet Singh" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]>; <sip-implementors@cs.columbia.edu> Sent: Friday, May 18, 2007 12:03 AM Subject: Re: [Sip-implementors] ptime/Maxptime support in SDP > Anywhere this has been defined the way to do this? I am looking for some > draft or spec where its clearly defined. People are taking their own > interpretations so want to know where I can find this in writing. > > thanks > > _____ > > From: Bala Neelakantan [mailto:[EMAIL PROTECTED] > Sent: Wednesday, May 16, 2007 10:34 PM > To: 'Manpreet Singh'; sip-implementors@cs.columbia.edu > Subject: RE: [Sip-implementors] ptime/Maxptime support in SDP > > > > For that, you have to have multiple m lines, with each having just one > codec, and the ptime can be specified for that. > > > > In your example, you can try separate m= line for each codec in the Offer. > > > > m=audio 22836 RTP/AVP 4 > c=IN IP4 216.168.161.230 > a=rtpmap:18 G729/8000 > a=fmtp:18 annexb=yes; > > a=ptime:20 > a=maxptime:40 > > m=audio 22838 RTP/AVP 18 > > a=rtpmap:4 G723/8000 > a=fmtp:4 bitrate=6.3;annexa=yes; > > a=ptime:30 > a=maxpime:60 > > > > > Thanks, > > Neel > > > > -----Original Message----- > From: Manpreet Singh [mailto:[EMAIL PROTECTED] > Sent: Wednesday, May 16, 2007 3:28 PM > To: [EMAIL PROTECTED]; > sip-implementors@cs.columbia.edu > Subject: RE: [Sip-implementors] ptime/Maxptime support in SDP > > > > 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] > <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- <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 > <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 > _______________________________________________ Sip-implementors mailing list Sip-implementors@cs.columbia.edu https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
