Support for source specific multicast

[bigbrobrody]

We have mandated the use of ONVIF in a network that uses PIM-SSM. However, this has caused an issue with Axis IP cameras, which use a different URL for accessing a SSM stream.

Searching through the ONVIF specifications, I can't find mention of source specific multicast. Have I missed it? If not, are there any plans to incorporate it?

[maxim-zapryanov]

SSM is a client side option, there is no need for support on server (IP camera) or any intermediary hops. Only limitation is that the SSM address must be in the range 232.0.0.0/8. Some servers might advertise SSM in the SDP if such is used.
As such PIM-SSM is not specified in the ONVIF specifications. Axis devices using a different URL for SSM is an implementation detail that might not be compatible with ONVIF or some other clients.

[bigbrobrody]

I'm resurrecting this thread because after lots more testing I still can't see a clear answer to how RTSP is supposed to work reliably in a source-specific multicast network. I'm not sure about your statement that SSM is a client side option. SSM is an architectural choice when designing the network. I can't see anything client side that signals use of SSM and in fact I believe that it's the server (camera/RTSP server) that should be working it out. I've created a short write-up of my thoughts here: https://github.com/bigbrobrody/ONVIF-SSM/tree/main