secure ONVIF audio backchannel

[Ishan Mandrekar]

Hi,

Has anybody been able to successfully transmit (and receive) SRTP on
the ONVIF audio backchannel? I don't see any built-in support for it.
For instance, when the backchannel pipeline is configured with
``application/x-srtp`` caps with a srtp decoder plugin in the launch
line, the SDP generated by the RTSP server does not include the
``key-mgmt`` attribute in the media section pertaining to the audio
backchannel.

Thanks,
-Ishan