CODEWITHSUNDEEP
videosip
Radhakrishnan
Radhakrishnan

Reputation: 177

Sharing content on a video channel between SIP video Endpoints?

Are there implementations were multiple "m=video" lines are sent in same SDP with different label ids? Can anyone give an example for it? If available, Can BFCP protocol be used to control the main video channel apart from the spkr or alt channels?

Upvotes: 2

Views: 3125

Answers (1)

Yochi Moran
Yochi Moran

Reputation: 76

There are implementations with multiple "m=video" lines are sent in same SDP with different label ids. Example is Video conference when one of the participants is sharing a presentation during the call. SDP example:

 v=0
 o=Alice 330742730 33077831 IN IP4 172.101.72.11
 s=lecture
 c=IN 172.101.72.11
 t=0 0
 m=video 52986 RTP/AVP 31
 a=rtpmap:31 H261/9000
 a=content:slides
 m=video 53134 RTP/AVP 31
 a=rtpmap:31 H261/9000
 a=content:main

“slides” is the presentation stream and “main” is the main Video stream. The streams are controlled by both SIP and BFCP. BFCP is used for “asking permission” to send the second stream, and SIP Offer/Answer model (i.e., sending SDP messages over Invite or Update) for actually open the stream. For example, if participant wishes to start presenting to other participants, he first asks for permission by sending BFCP “floor request”, and then opens the stream by send a Re-Invite with a new SDP adding the second “m=video” line. You can get more details from IMTC SIP Parity Activity Group: http://www.imtc.org/uc/sip-parity-activity-group/

Upvotes: 6

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