3.1.5.35 Extensions for multi-channel main-video modality negotiation

This section describes an SDP extension to negotiate a "main-video" modality consisting of multiple channels. A conference hosted by an audio/video MCU might be provisioned to support a "main-video" modality consisting of multiple channels<63>. This would enable a conference participant to simultaneously receive the video sources of multiple other participants, while also sourcing its own video into the conference.