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mediasipjmftelecommunicationsdp

SDP media field format

I would like to create a SDP media field with its attributes, and there are a few things I don't understand. I've skimmed and read the relevant RFC and I understand most of what each field means, but what I don't understand is how do I derive from the Audio/Video Format of the JMF, which parameters of the format compose the rtpmap registry entries I need to use. I see many times the fields

m=audio 12548 RTP/AVP 0 8 101
a=rtpmap:0 PCMU/8000
a=rtpmap:8 PCMA/8000
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-16
a=silenceSupp:off - - - -
a=ptime:20
a=sendrecv

these are received from the pbx server I'm connecting to, what do they mean in the terms of the JMF audio format properties. (I do understand these are standard audio format commonly used in telecommunication)

UPDATE:

I was more wondering about the format parameter '0 8 101' at the end of

m=audio 12548 RTP/AVP 0 8 101

I know they are referenced from this list, but how do I determine according to the JMF media format which one to use?

Thanks in advance,

Adam Zehavi.

Solution

  • You can use any of the codecs listed in the SDP. The agent that sent the SDP is stating that it supports all of the codecs listed.

    In the SDP example you've provided you could start sending RTP encoded with either G711 ULAW (PCMU) or G711 ALAW (PCMA).