Audio Channel Mapping

nmosaudiochannelmap exposes AMWA IS-08 routing as an audio matrix in the pipeline. Request one sink_%u pad for each input stream and one src_%u pad for each output stream. Every sink pad becomes an IS-08 Input; every source pad becomes an IS-08 Output.

Request and configure every pad before the element reaches READY. Channel counts come from negotiated audio caps by default, or from the pad's channels property when it is set. The important pad properties are:

• Sink pads: input-id, receiver-name, label, and description.
• Source pads: output-id, sender-name, label, description, and the optional initial active-map.

receiver-name associates an Input with the corresponding NMOS Receiver. sender-name associates an Output with the Source belonging to the corresponding NMOS Sender. The pad label is published as IS-08 /properties/name; it is not the caller-chosen Sender or Receiver name.

All elements that use the same node-seed contribute to one NMOS Node and one shared IS-08 Channel Mapping API. This includes multiple nmosaudiochannelmap elements. Each element's required channelmapping-name identifies the subset of Inputs and Outputs that it owns; it does not create a separate IS-08 API. The name must therefore be unique within the Node.

An empty input-id or output-id defaults to inputN or outputN, where N is the pad's position among the element's sink or source pads. These IDs appear in the IS-08 API paths and in active-map. IDs must be unique within the Node, so when a Node has more than one channel mapping, set explicit IDs on all (or all but one) of them. A clash fails when the element reaches PAUSED.

By default an Output may advertise unrestricted routable Inputs. Set restrict-routable-inputs=true to limit each Output to the Inputs owned by that element. Unrouted channels remain permitted. The element starts with an identity map where its channel geometry permits, then applies routing changes requested by an IS-08 Controller.

See the nmosaudiochannelmap reference for all element and pad properties and a complete pipeline example.