Version: 5.5

Group call flow

This page describes the flow of LINE Planet's group call (conference).

In the diagrams below, app clients and the app server belong to the application domain, and PlanetKit and LINE Planet Cloud belong to the LINE Planet domain.

Joining a group call

To join a group call, an app client must call JoinConference(). When a user joins a group call, the OnConnected event occurs.

Note

A room ID is required to join a group call room. Therefore, app clients must share a room ID through an application communication channel before joining a group call.

The following diagram shows a flow for joining a group call, where Client 01 joins a group video call with video and then Client K joins the group call without video.

When Client 01 wants to join a call, the app client of Client 01 calls JoinConference().
Planet Cloud invokes the Group Call Event callback to notify the app server of the new group call.
The OnConnected event occurs on the app client of Client 01.
When Client K wants to join the call, the app client of Client K calls JoinConference().
Planet Cloud invokes the Group Call Event callback to notify the app server of the group call's status change.
On the app client of Client 01, the OnPeerListUpdate event occurs. On the app client of Client K, the OnConnected, OnPeerListUpdate, and OnPeersVideoUpdated events occur.

In the flow above, you can see three related events.

Event	Condition	Description
`OnConnected`	After `JoinConference()` is called	Completion callback
`OnPeerListUpdate`	After someone joins or leaves the room	Delivers the list of participants who newly joined or left the room
`OnPeersVideoUpdated`	- After someone joins the room and enables or disables video - When someone joins the room with video enabled	Delivers the list of participants who enabled or disabled video

Peer list updated event

The OnPeerListUpdate event occurs whenever the list of participants is updated. Therefore, after Client K joins a room, both Client 01 and Client K receive this event.

When OnPeerListUpdate occurs for a new participant, other participants can create an instance of PeerControl for the participant and use the PeerControl instance to perform actions such as starting or stopping the participant's video or updating the participant's UI based on the participant's status changes.

Note

For more information on how to use PeerControl, refer to the group video call code example.

Peers video updated event

The OnPeersVideoUpdated event occurs whenever a participant's video stream changes.

In the example above, only Client 01 is sending video, and the OnPeersVideoUpdated event lets Client K know that Client 01 enabled video.

Tip

The OnPeersVideoUpdated event can also be generated by enabling a video call during an audio call. For more information, refer to Enable video call from audio call.

Updating interval of the events

An app client receives OnPeerListUpdate and OnPeersVideoUpdated based on the latest information within the update interval. As a result, the app client may not receive events for quick changes that occur within an update interval, such as when someone joins and leaves the room right away.

LINE Planet Cloud has a scheduler that updates information internally, and the scheduling interval becomes longer as the number of participants increases. Therefore, keep in mind that the update becomes slower in proportion to the number of participants.

Requesting peer video

An app client automatically receives the audio stream after receiving the OnConnected event. However, a video stream is not sent automatically by LINE Planet Cloud unless the app client calls PeerControl::StartVideo() with a proper video resolution.

Applications can find out who enabled the video stream from the OnPeersVideoUpdated callback of IConferenceEvent or the OnVideoUpdated callback of IPeerControlEvent.

Group call request peer video sequence diagram

It is recommended that you use PLNK_VIDEO_RESOLUTION_RECOMMENDED for the resolution parameter when calling StartVideo(), which makes PlanetKit use recommended resolutions depending on the number of video streams. For a more detailed explanation, see Peer video resolution in a group call.

Tip

Depending on the operating system's UI framework, additional API calls might be required to render the peer's video stream. For more information, see API reference.

Leaving a group call

To leave a group call, an app client must call LeaveConference(). On the app client of the user who left the group call, the OnDisconnected event occurs. On the app clients of peers, the OnPeerListUpdate event occurs because the list of participants has been changed.

Participant with video enabled

If the participant who enabled video leaves the room, OnPeersVideoUpdated is sent to other participants.

Group call leave video enabled sequence diagram

When Client 01 wants to leave a call, the app client of Client 01 calls LeaveConference().
On the app client of Client K, the OnPeersVideoUpdated and OnPeerListUpdate events occur. On the app client of Client 01, the OnDisconnected event occurs.
Planet Cloud invokes the Group Call Event callback to notify the app server of the group call's status change.

Note

If the participant who was sending screen share video leaves the room, OnPeerScreenShareUpdated with DISABLED state is sent to other participants.
The OnPeersVideoUpdated or OnPeerScreenShareUpdated with DISABLED state is sent only to participants who are using PlanetKit 4.4 or higher.

Participant with video disabled

If the participant who disabled video leaves the room, OnPeersVideoUpdated does not occur.

Group call leave video disabled sequence diagram

When Client K wants to leave a call, the app client of Client K calls LeaveConference().
On the app client of Client 01, the OnPeerListUpdate event occurs. On the app client of Client K, the OnDisconnected event occurs.
Planet Cloud invokes the Group Call Event callback to notify the app server of the group call's status change.

Group call flow