Oh sorry I just slipped out of the thread.
________________________________ From: Manpreet Singh [mailto:[EMAIL PROTECTED] Sent: Friday, June 01, 2007 10:56 AM To: Srinivas .; [EMAIL PROTECTED]; [email protected]; [EMAIL PROTECTED] Subject: RE: [SIPForum-discussion] [Sip-implementors] ptime/Maxptime supportin SDP I think we are digressing from the main conversation. Everyone knows the priority is based on sequence in m line but the thread is discussing how can we put different ptimes for different codecs. the suggestion was to use different m lines and thats how the issue arose that it wont be possible to find the priority. so if each m line has only 1 codec, and there are multiple m lines, how is the priority decided? But the bigger question is that if thats the right way to do and if has been formally defined somewhere. Manpreet ________________________________ From: Srinivas . [mailto:[EMAIL PROTECTED] Sent: Friday, June 01, 2007 1:12 AM To: Manpreet Singh; [EMAIL PROTECTED]; [email protected]; [EMAIL PROTECTED] Subject: RE: [SIPForum-discussion] [Sip-implementors] ptime/Maxptime supportin SDP As per RFC 3264, the offerer should place codecs in the order of preference in "m" line. v=0 o=carol 28908764872 28908764872 IN IP4 100.3.6.6 s=- t=0 0 c=IN IP4 192.0.2.4 m=audio 0 RTP/AVP 0 1 3 a=rtpmap:0 PCMU/8000 a=rtpmap:1 1016/8000 a=rtpmap:3 GSM/8000 m=video 0 RTP/AVP 31 34 a=rtpmap:31 H261/90000 a=rtpmap:34 H263/90000 In the above media attribute line codec 0 has high priority then follows 1 and 3. It is answerer to negotiate based on this preference. Cheers S ________________________________ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Manpreet Singh Sent: Friday, June 01, 2007 1:21 AM To: [EMAIL PROTECTED]; [email protected]; [EMAIL PROTECTED] Subject: Re: [SIPForum-discussion] [Sip-implementors] ptime/Maxptime supportin SDP I was reading some threads on this last year and there is says this way there is no way to find out the priority of the codecs to be used. So if one does implement this how would the priority be decided? So in the example below, which has higher preference, payload 18 or 4? Is this defined somewhere formally? thanks ________________________________ From: Bala Neelakantan [mailto:[EMAIL PROTECTED] Sent: Wednesday, May 16, 2007 10:34 PM To: 'Manpreet Singh'; [email protected] 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]; [email protected] 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] Sent: Wednesday, May 16, 2007 4:15 PM To: 'Manpreet Singh'; [email protected] 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: [email protected] > 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 > [email protected] > https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors ======================================================================== ==================================================== Disclaimer: This message and the information contained herein is proprietary and confidential and subject to the Tech Mahindra policy statement, you may review the policy at http://www.techmahindra.com/Disclaimer.html externally and http://tim.techmahindra.com/Disclaimer.html internally within Tech Mahindra. ======================================================================== ==================================================== ============================================================================================================================ Disclaimer: This message and the information contained herein is proprietary and confidential and subject to the Tech Mahindra policy statement, you may review the policy at <a href="http://www.techmahindra.com/Disclaimer.html";>http://www.techmahindra.com/Disclaimer.html</a> externally and <a href="http://tim.techmahindra.com/Disclaimer.html";>http://tim.techmahindra.com/Disclaimer.html</a> internally within Tech Mahindra. ============================================================================================================================ _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
