Conference protocol

The protocol described in this article is used between the PBX conference object in the PBX and a conference interface. It's purpose is to handle additional calls from a client endpoint to the conference interface. This calls are established to handle more than one video streams from the conference interface. The following facility messages are currently known:

• Video setup
• Video connect
• Video priority
• Video capabilities

Depending on the value of the type property, different objects are defined. The following types are known:

This facility marks the call as a video call, informs about the direction and requests optionally a individual video stream with a given id. The bitrate argument informs about the own quality capability or the quality of a requested stream.

{
    "type": "video_setup",
    "mode": Video Direction Mode,
    "guid": string,
    "id": unsigned,
    "bitrate": unsigned,
}

This is a string defining the mode of the video direction. The following values are defined for this property:

This facility informs about the guid and video stream id and is an optional response to a created video channel or a message to set the requested stream quality.

{
    "type": "video_conn",
    "guid": string,
    "id": unsigned,
    "bitrate": unsigned,
}

This facility is used to temporarily pause speaker detection. Can be used when desktop sharing is started (on=true) and stopped (on=false).

{
    "type": "video_priority",
    "on": boolean
}

This facility is used to indicate support for "multi-video".
A multi-video-capable endpoint sends this facility when initiating a call ("setup" message).
The multi-video-capable conference sends this facility when accepting a call ("conn" message).

If both ends of a call indicate multi-video-support

The main call connection is established with audio-only. For video separate connections are opened by the endpoint (sendonly and recvonly).

If NOT both ends of a call indicate multi-video-support

The main call connection is established with audio and video channel. E.g. endpoint-to-endpoint call.

{
    "type": "video_capabilities",
    "multivideo": boolean
}

Examples:

Legacy endpoint calls lagacy conference:

EP sends "setup" without video_capabilities(multivideo=true) and A+V offer.
CONF sends "conn" without video_capabilities(multivideo=true) and A+V answer.
Audio and video are transported over main call connection.

Legacy endpoint calls multi-video conference:

EP sends "setup" without video_capabilities(multivideo=true) and A+V offer.
CONF sends "conn" with video_capabilities(multivideo=true) and A+V answer.
Audio and video are transported over main call connection.

Multi-video endpoint calls lagacy conference:

EP sends "setup" with video_capabilities(multivideo=true) and A+V offer.
CONF sends "conn" without video_capabilities(multivideo=true) and A+V answer.
Audio and video are transported over main call connection.

Multi-video endpoint calls multi-video conference:

EP sends "setup" with video_capabilities(multivideo=true) and A+V offer.
CONF sends "conn" with video_capabilities(multivideo=true) and Audio-Only answer.
Audio only is transported over main call connection. EP opens additional video-only connections to CONF.