Renderer state
These events are associated with the state of AV equipment renderering. This comes down to the state of the amplifier.
Event Type
http://id.webbrick.co.uk/events/av/render/state
Event Source
av/render/state/<usn> The usn is the uniqueu id for the av device
Event Payload
| usn | a unique identifier for the target. | mandatory | volume | current volume setting | only if changed |