Hi Guillermo, On Wed, 2022-09-14 at 04:39 +0000, Zuñiga, Guillermo wrote: > I was trying looking for in the SDP RFC the following, but I couldn´t > find specific example of information. > > Where in the SDP RFC I could find why rtpmap is not define when we > have just one payload like g711 and just another dynamic payload?
The rtpmap attribute is optional if the format has a static payload type assigned to it by the media profile. You can find this in RFC 4566 Section 6: As an example of a static payload type, consider u-law PCM coded single-channel audio sampled at 8 kHz. This is completely defined in the RTP Audio/Video profile as payload type 0, so there is no need for an "a=rtpmap:" attribute However, RFC 3264 (offer / answer model) recommends that a=rtpmap: is used for all payload types (Section 5.1): In the case of RTP streams, all media descriptions SHOULD contain "a=rtpmap" mappings from RTP payload types to encodings. If there is no "a=rtpmap", the default payload type mapping, as defined by the current profile in use (for example, RFC 1890 [5]) is to be used. For this reason most SIP UAs include a=rtpmap: for all payload types, but having it only for dynamic payload types is acceptable, too. Best, Jānis _______________________________________________ Sip-implementors mailing list Sip-implementors@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
