Media forking howto

[Mihovil Kolaric]

Hi,

I am using RTPengine together with kamailio in different scenarios (WebRTC-Gateway, Recording for SIP-calls).

No I am trying to duplicate the RTP-Stream of a SIP-call (resp: one direction of it) to 1..x other SIP-UAs. This somehow sounds like

• Media forking
• Publish/subscribe mechanism for N-to-N media forwarding

in https://github.com/sipwise/rtpengine/blob/master/README.md - however, I do not really understand how to do that/where to start. For obvious reasons the commands are not present in kamailio´s rtpengin-module - is there however any other tool/utility that uses this media forking, so I can study it? Or is there any howto/guideline to use that feature?

Any hints are appreciated.

Thx & Br,

M. K.

[Youssef Boujraf]

Hi,

Would you like to share your rtpengine and kamailio config pls?

I am looking for webrtc gateway with rtpengine and have some issue to setup with kamailo.

Best Regards

[Mihovil Kolaric]

Hi,

for the WebRTC-Gateway I used this howto: https://github.com/havfo/WEBRTC-to-SIP

Best Regards

[Richard Fuchs]

Hi,

This is a relatively new feature and so not well supported in other software yet. Contributions are always welcome.

OpenSIPS is working on integrating this with their SIPREC module. I suppose the Kamailio UAC module could also be used for this. Other solutions like general SIP UAs would also be possible.

As a PoC you can use the included `rtpengine-ng-client` script. You need to know the call ID of the call that you want to fork media from, and be able to select a particular call party (e.g. through their SIP tag or the provided label) OR be able to handle multi-part SDP that receives media from all call parties.

You start by sending a subscribe request to rtpengine. For example for a SIPREC-style subscription you would do something like

$ rtpengine-ng-client "subscribe request" --call-id=$CALLID --all --SIPREC

This produces a multi-part offer SDP (that would be sent as an invite to the SIPREC SRS). It also returns a "to-tag" which is used to identify this subscription.

The corresponding answer SDP (from the 200 OK from the SRS) would then be passed as a subscribe answer to rtpengine, together with the to-tag that was returned by the subscribe-request:

$ rtpengine-ng-client "subscribe answer" --call-id=$CALLID --sdp=$SDP --to-tag=$TAG

At this point the media would start flowing to the SRS.

Subscriptions can use all other available options, such as encryption, transcoding, etc.

For the N-to-N media forwarding feature you would create subscriptions exactly in the same way, except that you subscribe not to a regular call created through offer/answer, but rather to send-only media streams created via "publish" (which works analogous to "offer" except that it's one-way).

HTH

Cheers

[Youssef Boujraf]

Dear,

Is this repo working with kamailio behind the NAT ?

Best Regards,

[geekdroid 0409]

Hi Mihovil Kolaric,

Have you tried the solution mentioned, can it be implemented? Do you have any ideas to share, 

thank you very much!