The example shows how to play a number of streams in one WebRTC connection with simulcast. A room is considered to be a publishing unit, that is, viewers who connect to this room receive all the streams published in it.

On the screenshots below:

Note that audio tracks are playing in a separate audio tags.

Example source code

The source code consists of the following modules:

Analyzing the code

To analyze the example source code, take the file player.js version with hash 7bd8412 available here

1. Local variables

Local variables declaration to work with constants, SFU SDK, to display video and to work with client configuration

code

const constants = SFU.constants;
const sfu = SFU;
let mainConfig;
let remoteDisplay;
let playState;
const PLAY = "play";
const STOP = "stop";
const PRELOADER_URL="../commons/media/silence.mp3"

2. Default configuration

Default room configuration to use if there is no config.json file found

code

const defaultConfig = {
    room: {
        url: "ws://127.0.0.1:8080",
        name: "ROOM1",
        pin: "1234",
        nickName: "User1"
    }
};

3. Object to store current publishing/playback state

The object should keep Websocket session data, WebRTC connection data and room data, and shoukd form HTML tags ids to access them from code.

code

const CurrentState = function(prefix) {
    let state = {
        prefix: prefix,
        pc: null,
        session: null,
        room: null,
        set: function(pc, session, room) {
            state.pc = pc;
            state.session = session;
            state.room = room;
        },
        clear: function() {
            state.room = null;
            state.session = null;
            state.pc = null;
        },
        buttonId: function() {
            return state.prefix + "Btn";
        },
        buttonText: function() {
            return (state.prefix.charAt(0).toUpperCase() + state.prefix.slice(1));
        },
        inputId: function() {
            return state.prefix + "Name";
        },
        statusId: function() {
            return state.prefix + "Status";
        },
        formId: function() {
            return state.prefix + "Form";
        },
        errInfoId: function() {
            return state.prefix + "ErrorInfo";
        },
        is: function(value) {
            return (prefix === value);
        }
    };
    return state;
}

4. Initialization

init() code

The init() function is called on page load and:

const init = function() {
    let configName = getUrlParam("config") || "./config.json";
    ...
    playState = CurrentState(PLAY);
    $.getJSON(configName, function(cfg){
        mainConfig = cfg;
        onDisconnected(playState);
    }).fail(function(e){
        //use default config
        console.error("Error reading configuration file " + configName + ": " + e.status + " " + e.statusText)
        console.log("Default config will be used");
        mainConfig = defaultConfig;
        onDisconnected(playState);
    });
    $("#url").val(setURL());
    $("#roomName").val("ROOM1-"+createUUID(4));
    $("#playName").val("Player1-"+createUUID(4));
}

5. Establishing server connection

connect(), SFU.createRoom() code

The connect() function is called by Publish or Play click:

const connect = function(state) {
    //create peer connection
    pc = new RTCPeerConnection();
    //get config object for room creation
    const roomConfig = getRoomConfig(mainConfig);
    roomConfig.pc = pc;
    roomConfig.url = $("#url").val();
    roomConfig.roomName = $("#roomName").val();
    roomConfig.nickname = $("#" + state.inputId()).val();
    // clean state display items
    setStatus(state.statusId(), "");
    setStatus(state.errInfoId(), "");
    // connect to server and create a room if not
    const session = sfu.createRoom(roomConfig);
    session.on(constants.SFU_EVENT.CONNECTED, function(room) {
        state.set(pc, session, room);
        onConnected(state);
        setStatus(state.statusId(), "ESTABLISHED", "green");
    }).on(constants.SFU_EVENT.DISCONNECTED, function() {
        state.clear();
        onDisconnected(state);
        setStatus(state.statusId(), "DISCONNECTED", "green");
    }).on(constants.SFU_EVENT.FAILED, function(e) {
        state.clear();
        onDisconnected(state);
        setStatus(state.statusId(), "FAILED", "red");
        setStatus(state.errInfoId(), e.status + " " + e.statusText, "red");
    });
}

6. Playback start after session establishing

onConnected() code

The onConnected() function:

const onConnected = function(state) {
    $("#" + state.buttonId()).text("Stop").off('click').click(function () {
        onStopClick(state);
    }).prop('disabled', false);
    ...
    // Add errors displaying
    state.room.on(constants.SFU_ROOM_EVENT.FAILED, function(e) {
        setStatus(state.errInfoId(), e, "red");
    }).on(constants.SFU_ROOM_EVENT.OPERATION_FAILED, function (e) {
        setStatus(state.errInfoId(), e.operation + " failed: " + e.error, "red");
    });
    playStreams(state);
}

7. Streams playback

playStreams(), SFURoom.join() code

The playStreams() function:

const playStreams = function(state) {
    //create remote display item to show remote streams
    remoteDisplay = initRemoteDisplay({
        div: document.getElementById("remoteVideo"),
        room: state.room,
        peerConnection: state.pc
    });
    state.room.join(state.pc);
}

8. Playback stopping

stopStreams(), remoteDisplay.stop() code

const stopStreams = function(state) {
    if (remoteDisplay) {
        remoteDisplay.stop();
    }
}

9. Play click action

onStartClick(), playFirstSound(), connect() code

const onStartClick = function(state) {
    if (validateForm("connectionForm") && validateForm(state.formId())) {
        $("#" + state.buttonId()).prop('disabled', true);
        if (state.is(PLAY) && Browser().isSafariWebRTC()) {
            playFirstSound(document.getElementById("main"), PRELOADER_URL).then(function () {
                connect(state);
            });
        } else {
            connect(state);
        }
    }
}

10. Stop click actions

onStopClick(), Session.disconnect() code

The onStopClick() function:

const onStopClick = function(state) {
    $("#" + state.buttonId()).prop('disabled', true);
    stopStreams(state);
    state.session.disconnect();
}

11. Websocket session disconnection actions

onDisconnected() code

The onDisconnected() functions:

const onDisconnected = function(state) {
    $("#" + state.buttonId()).text(state.buttonText()).off('click').click(function () {
        onStartClick(state);
    }).prop('disabled', false);
    $('#url').prop('disabled', false);
    $("#roomName").prop('disabled', false);
    $("#" + state.inputId()).prop('disabled', false);
}