Co-host across Channels

Introduction

Co-hosting across channels refers to the process where the Agora SDK relays the media stream of a host from an interactive live streaming channel (source channel) to a maximum of four interactive live streaming channels (destination channels). It has the following benefits:

• All hosts in the relay channels can see and hear each other.
• The audience members in the relay channels can see and hear all hosts.

Co-hosting across channels applies to scenarios such as an online singing contest, where hosts of different channels interact with each other.

Sample project

We provide an open-source channel media relay demo project that implements channel media relay on GitHub. You can try the demo and view the source code.

• iOS: ChannelMediaRelay
• macOS: ChannelMediaRelay

Implementation

Before relaying media streams across channels, ensure that you have implemented the basic real-time communication functions in your project. For details, see the following documents:

• iOS: Start Live Interactive Streaming.
• macOS: Start Live Interactive Streaming.

As of v2.9.0, the Agora Native SDK supports co-hosting across channels with the following methods:

• startChannelMediaRelay
• updateChannelMediaRelay
• stopChannelMediaRelay

Once the channel media relay starts, the SDK relays the media streams of a host from the source channel to at most four destination channels.

During the relay, the SDK reports the states and events of the channel media relay with the channelMediaRelayStateDidChange and didReceiveChannelMediaRelayEvent callbacks. Refer to the following codes and their corresponding states to implement you code logic:

Note:

• Any host in an interactive live streaming channel can call the startChannelMediaRelay method to enable channel media stream relay. The SDK relays the media streams of the host who calls the method.
• During the media stream relay, if the host of the destination channel drops offline or leaves the channel, the host of the source channel receives the didOfflineOfUid callback.

API call sequence

Follow the API call sequence to implement your code logic:

Sample code

// Configures the information of the source channel. Set channelName as the default value, meaning the current channel name. Set uid as the default value 0.
let config = AgoraChannelMediaRelayConfiguration()
// Note that sourceChannelToken is different from the token used for joining the source channel. You need to generate sourceChannelToken with the source channel name and a uid of 0.
config.sourceInfo = AgoraChannelMediaRelayInfo(token: sourceChannelToken)

// Configures the information of the destination channel.
let destinationInfo = AgoraChannelMediaRelayInfo(token: destinationChannelToken)
config.setDestinationInfo(destinationInfo, forChannelName: destinationChannelName)
// Starts the channel media relay.
agoraKit.startChannelMediaRelay(config)

// Stops the channel media relay.
agoraKit.stopChannelMediaRelay()

// Uses the channelMediaRelayStateDidChange callback to monitor the state of the channel media relay.
func rtcEngine)(_ engine: AgoraRtcEngineKit, channelMediaRelayStateDidChange state: AgoraChannelMediaRelayState, error: AgoraChannelMediaRelayError) {
  LogUtils.log(message: "channelMediaRelayStateDidChange: \(state.rawVlue) error \(error.rawValue)", level: .info)

  switch(state){
    case .running:
        isRelaying = true
        break
    case .failure:
        showAlert(message: "Media Relay Failed: \(error.rawValue)")
        isRelaying = false
        break
    case .idle:
        isRelaying = false
        break
    default:break
  }
}

API Reference

• startChannelMediaRelay
• updateChannelMediaRelay
• stopChannelMediaRelay
• channelMediaRelayStateDidChange
• didReceiveChannelMediaRelayEvent

Considerations

• The Agora RTC SDK supports relaying media streams to a maximum of four destination channels. To add or delete a destination channel, call updateChannelMediaRelay.
• This feature supports integer user IDs only.

• When setting the source channel information, ensure that you set uid as 0, and the uid that you use to generate the token should also be set as 0.

• To call startChannelMediaRelay again after it succeeds, you must call stopChannelMediaRelay to quit the current relay.