Hello Ravi,
>> multiple ptimes in a media line? Please accept my apologies
>> if this topic has been discussed ad nauseam in the past.
No problem, I have pasted here some extracts I wrote in
an old sip-implementors e-mail
>> 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
>> >
>>
>>
So, the above example is
g711u-law ("0") at 10ms packet time
g723.1 ("4") at 30ms packet time
g729 ("18") at 30ms packet time
And for an example with RFC2833:
>> 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).
Note also that some people use X-mptime instead of mptime
but the format is the same. (the X- is used because it's
unstandardised)
This way of doing it does not seem to be in any standard
but I have experienced quite a few vendors who have used
either mptime or X-mptime so I suggest you prepare to accept
either.
Good luck.
Regards,
Attila
http://www.vegastream.com
>> -----Original Message-----
>> From: [EMAIL PROTECTED]
>> [mailto:[EMAIL PROTECTED] Behalf Of
>> Gummadidala, Ravi
>> Sent: 03 October 2005 04:01
>> To: [email protected]
>> Subject: [Sip-implementors] multiple ptime question
>>
>>
>> I know that this has been discussed in the past but I am not
>> sure what the conclusion/concensus was. The question is
>> whether attributes like ptime are codec-specific or media
>> specific? Some people have argued that these are media
>> specific properties and it is invalid for a SDP m line to
>> have multiple ptime values. The other school of thought
>> claims that ptime is a codec specific attribute. I am also
>> inclined to go with the latter. Say in the m line a UA
>> advertises support for EVRC and G723. EVRC is a 20ms frame
>> based codec while G723 is a 30ms frame based codec. How
>> should such an SDP be formulated if it is invalid to have
>> multiple ptimes in a media line? Please accept my apologies
>> if this topic has been discussed ad nauseam in the past.
>> Thanks,
>> -Ravi.
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>>
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