SFU Player¶

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:

Server url - Websocket URL of WCS server
Room name - room name
Player - viewer user name
360p, 720p, 180p send - quality switch buttons

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

Example source code¶

The source code consists of the following modules:

player.html - HTML page
player.css - HTML page styles
player.js - main application logic
config.json - client configuration file, contains streams publishing description

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:

initializes state objects
reads config.json file or default configuration
initializes input fields

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:

creates PeerConnection object
cleans the previous session state displayed
sets up room configuration and creates Websocket session
subscribes to Websocket session events

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:

sets up Stop button click actions
subscribes to room error events
calls playback 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:

initializes a base container tag to display incoming media streams
joins to the room on server

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

8. Playback stopping¶

stopStreams(), remoteDisplay.stop() code

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

9. Play click action¶

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

validates input fields
in Safari browser, calls playFirstSound() before playback to automatically play incoming audio
calls connect() function

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:

stops playback
disconects Websocket session

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

11. Websocket session disconnection actions¶

onDisconnected() code

The onDisconnected() functions:

sets up Play click actions
enables Server url and Room name fields access, if there's no parallel session

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);
}