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

  • All hosts in the relay channels can see and hear each other.
  • The audiences 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.


To enable channel media relay, contact

Before relaying media streams across channels, ensure that you have implemented the basic real-time communication functions in your project. For details, see 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 onChannelMediaRelayStateChanged and onChannelMediaRelayEvent callbacks. Refer to the following codes and their corresponding states to implement your code logic:

State codes Event codes The media stream relay state
RELAY_STATE_FAILURE(3) / Exceptions occur for the media stream relay. Refer to the error parameter for troubleshooting.
RELAY_STATE_IDLE(0) and RELAY_OK(0) / The channel media relay stops.


  • Any host in a live interactive 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 onUserOffline callback.

API call sequence

Follow the API call sequence to implement your code logic:

Sample code

ChannelMediaInfo *lpSrcinfo = new ChannelMediaInfo;
lpSrcinfo->channelName = nullptr;
lpSrcinfo->token = nullptr;
lpSrcinfo->uid = 0;
ChannelMediaInfo  *lpDestInfos = NULL;
int nDestCount = arrayDestInfos.size();    
for(int nIndex = 0; nIndex < nDestCount; nIndex++) {
        std::string strChannelName = arrayDestInfos[nIndex]["channelName"].asString();
        std::string strtoken  = arrayDestInfos[nIndex]["token"].asString();
        uid_t uid = arrayDestInfos[nIndex]["uid"].asUInt();

        lpDestInfos[nIndex].channelName = new char[strChannelName.length() + 1];
        lpDestInfos[nIndex].token = new char[strtoken.length() + 1];
        strcpy_s((char*)lpDestInfos[nIndex].channelName,strChannelName.length() + 1,strChannelName.c_str());
        strcpy_s((char*)lpDestInfos[nIndex].token,strtoken.length() + 1,strtoken.c_str());
        lpDestInfos[nIndex].uid = uid;
ChannelMediaRelayConfiguration cmrc;
cmrc.srcInfo = lpSrcinfo;
cmrc.destInfos = lpDestInfos;
cmrc.destCount = nDestCount;
int ret = 0;
// Sets the destination channel you want to join.
ret = m_lpAgoraEngine->startChannelMediaRelay(cmrc);

ChannelMediaInfo *lpUpdateDestInfos = new ChannelMediaInfo;
lpUpdateDestInfos->channelName = "test";
lpUpdateDestInfos->token = nullptr;
lpUpdateDestInfos->uid = 0;
cmrc.destInfos = lpUpdateDestInfos;
cmrc.destCount = 1;
// Updates the media relay channels.
ret = m_lpAgoraEngine->updateChannelMediaRelay(cmrc);    
After calling the startChannelMediaRelay method, you can call the updateChannelMediaRelay method to add or delete the relay channels.

API reference


  • 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 souce channel information (setSrcChannelInfo), 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.