Opened 8 years ago

Closed 8 years ago

Last modified 8 years ago

#1300 closed enhancement (fixed)

Symmetric payload type in generating SDP answer

Reported by: bennylp Owned by: nanang
Priority: normal Milestone: release-2.0-beta
Component: pjmedia Version: trunk
Keywords: Cc:
Backport to 1.x milestone: Backported:

Description (last modified by nanang)

Answerer SHOULD use matching payload type as the offer:

  • RFC 3264 6.1:


In the case of RTP, if a particular codec was referenced with a specific payload type number in the offer, that same payload type number SHOULD be used for that codec in the answer.

  • RFC 6184:


To simplify the handling and matching of these configurations, the same RTP payload type number used in the offer SHOULD also be used in the answer, as specified in [8]. An answer MUST NOT contain the payload type number used in the offer unless the configuration is exactly the same as in the offer.

Note:

  • Implemented in SDP negotiator (instead of in endpoint as the preanswer generator), as the codecs need to be negotiated first.
  • Initiating re-INVITE will revert the payload type numbers to the pjmedia defaults, which should be fine. If this is not acceptable, a simple solution will be providing alternatives for SDP generation for the re-INVITE:
    • using active local SDP,
    • no SDP.

Change History (6)

comment:1 Changed 8 years ago by nanang

  • Description modified (diff)
  • Summary changed from With H.264, answerer SHOULD use matching payload type as the offer to Symmetric payload type in generating SDP answer

comment:2 Changed 8 years ago by nanang

(In [3837]) Re #1300: Implemented symmetric payload type in generating SDP answer in SDP negotiator.
This should work for all codecs, audio & video. Can be disabled at compile-time
using PJMEDIA_SDP_NEG_REWRITE_ANSWER_PT macro setting.

comment:3 Changed 8 years ago by nanang

  • Milestone changed from release-2.x to release-2.0-beta
  • Resolution set to fixed
  • Status changed from new to closed

comment:4 Changed 8 years ago by nanang

  • Description modified (diff)

comment:5 Changed 8 years ago by bennylp

(In [3842]) Re #1300: fixed bug when looking for non-telephone-events codec in the incoming INVITE causing it to rejects with 488

comment:6 Changed 8 years ago by nanang

(In [3856]) Re #1300: Bug in updating SDP rtpmap in symmetric PT when PT offer is shorter than our default, the rtpmap value length was not updated.

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