Hi, My query is regarding ptime behavior for iLBC codec sent in SDP. Does ptime have to be a multiple of the mode (20/30) for iLBC? And, if it is not, I believe it should be ignored. Is this correct?
We are facing certain situations in which we cannot provide a ptime conducive to the multiple theory to the peer. Should this be avoided under all circumstances? Or since ptime is only a suggestive parameter, things can be made simpler by using the same ptime handling policy for all codecs (iLBC, as well, non-iLBC)? In RTP, ptime is just a suggestive media parameter. Ideally ptime should be a multiple of mode value in case of iLBC. This would have been the thumb rule for the ideal world where ptime would have been followed religiously. However, probably to keep things simpler, and avoid confusions in case of multiple codecs (iLBC and non-iLBC), such a definition was only provided for mptime in RFC 3952 as quoted below: maxptime:The maximum amount of media which can be encapsulated in each packet, expressed as time in milliseconds. The time SHALL be calculated as the sum of the time the media present in the packet represents. The time SHOULD be a multiple of the frame size. This attribute is probably only meaningful for audio data, but may be used with other media types if it makes sense. It is a media attribute, and is not dependent on charset. Note that this attribute was introduced after RFC 2327, and non updated implementations will ignore this attribute. This was, however, not imposed on the ptime for iLBC as quoted below: ptime: Defined as usual for RTP audio (see SDP RFC) Thanks Shruti Aricent Technology Holdings "DISCLAIMER: This message is proprietary to Aricent and is intended solely for the use of the individual to whom it is addressed. It may contain privileged or confidential information and should not be circulated or used for any purpose other than for what it is intended. If you have received this message in error,please notify the originator immediately. If you are not the intended recipient, you are notified that you are strictly prohibited from using, copying, altering, or disclosing the contents of this message. Aricent accepts no responsibility for loss or damage arising from the use of the information transmitted by this email including damage from virus." _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
