Re: [webrtc-pc] Missing CNAME in RID based simulcast offer (#2114)

From what I can see, libwebrtc is using msid to synchronize the RTP streams. CNAME is used for statistics only.  "LS" groups are not supported. Based on the source code (https://cs.chromium.org/chromium/src/third_party/webrtc/call/audio_receive_stream.h?type=cs&q=sync_group&sq=package:chromium&g=0&l=123), there was an issue (https://bugs.chromium.org/p/webrtc/issues/detail?id=4762) to fix how synchronization works but this was since closed. 

@fippo "LS" group should allow to specify synchronization context across multiple MediaStreams. Tracks withing MediaStream are always synchronized and LS group is redundant (unless remote does not support msid).

JSEP requires adding LS group to SDP and adding individual tracks to the appropriate LS group, including tracks in the same MediaStream. (https://tools.ietf.org/html/draft-ietf-rtcweb-jsep-26#section-5.2.1). As far as I can see current implementations are not compliant with JSEP draft.

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Received on Wednesday, 6 March 2019 22:45:40 UTC