RTP Dynamic Payload and Static Payload
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Static payload is payload which is defined in the IANA rtp parameter document
An example of a static payload type is a-law PCM coded single channel audio sampled at 8KHz. This is completely defined in the RTP Audio/Video profile as payload type 8, so the media field for such a stream sent to UDP port 47232 is: m=video 47232 RTP/AVP 8
For static payloads the a=rtpmap line is not mandatory in SDP, considering that the payload type itself can specify unique audio encoding
An example of a dynamic payload type is 18 bit linear encoded stereo audio sampled at 18KHz. If we wish to use dynamic RTP/AVP payload type 99 for such a stream, additional information (a=rtpmap line) is required to decode it:
m=video 39132 RTP/AVP 99
a=rtpmap:99 L18/16000/2
The format is a=rtpmap:payload type encoding name/clock rate/encoding parameters
in this rtpmap we are mapping a codec (encoding name) with the payload number as it does not have a rtp payload number allocated by IANA
rfc3551 defines codec names which can be used in SDP while IANA maps codecs names to a number known as payload number
2 Responses to “RTP Dynamic Payload and Static Payload”
“m=video 47232 RTP/AVP 8″ don’t you me audio?
By Luis on Jun 28, 2011
mean*
By Luis on Jun 28, 2011