The functions to create and destroy HTML5 tags to capture and display video and audio are moved to display.js module
Analyzing the source code
To analyze the source code take the version available here which can be downloaded with build 1.0.1.36
Local video capturing and displaying
1. Initialization
initLocalDisplay() code
The initLocalDisplay() returns the object to work with HTML5 tags to capture and display local video and audio
const initLocalDisplay = function(localDisplayElement){
const localDisplayDiv = localDisplayElement;
const localDisplays = {};
const removeLocalDisplay = function(id) {
...
}
const getAudioContainer = function() {
...
};
const add = function(id, name, stream) {
...
}
const stop = function () {
...
}
const audioStateText = function (stream) {
...
}
return {
add: add,
stop: stop
}
}
2. Adding HTML tags to capture and display local video/audio
2.1. Add audio track to HTML5 video tag
add() code
Where:
- audio track is added to video tag
onendedevent handler is added to audio track
if (stream.getAudioTracks().length > 0) {
let videoElement = getAudioContainer();
if (videoElement) {
let track = stream.getAudioTracks()[0];
videoElement.video.srcObject.addTrack(track);
videoElement.audioStateDisplay.innerHTML = audioStateText(stream);
track.addEventListener("ended", function() {
videoElement.video.srcObject.removeTrack(track);
videoElement.audioStateDisplay.innerHTML = "No audio";
//check video element has no tracks left
for (const [key, vTrack] of Object.entries(videoElement.video.srcObject.getTracks())) {
if (vTrack.readyState !== "ended") {
return;
}
}
removeLocalDisplay(videoElement.id);
});
return;
}
}
2.2. Container creation to display local video
add() code
Where:
- container
divtag to display local video is created divtag to display video information is created
const coreDisplay = document.createElement('div');
coreDisplay.setAttribute("class","text-center");
coreDisplay.setAttribute("style","width: auto; height: auto;");
coreDisplay.id = stream.id;
const streamNameDisplay = document.createElement("div");
streamNameDisplay.innerHTML = "Name: " + name;
streamNameDisplay.setAttribute("class","text-center");
streamNameDisplay.setAttribute("style","width: auto; height: auto;");
coreDisplay.appendChild(streamNameDisplay);
2.3. Button creation to mute/unmute local audio
add() code
Where:
- button to mute/unmute local audio is created
- clieck event handler for the button is added
const audioStateDisplay = document.createElement("button");
audioStateDisplay.innerHTML = audioStateText(stream);
audioStateDisplay.addEventListener('click', function(){
if (stream.getAudioTracks().length > 0) {
stream.getAudioTracks()[0].enabled = !(stream.getAudioTracks()[0].enabled);
audioStateDisplay.innerHTML = audioStateText(stream);
}
});
coreDisplay.appendChild(audioStateDisplay);
2.4. Tag creation to display local video
add() code
Where:
- contaner tag which can be resized to a parent node is created
- HTML5
videotag is created (considering Safari publishing)
const streamDisplay = document.createElement('div');
streamDisplay.id = "stream-" + id;
streamDisplay.setAttribute("class","text-center");
streamDisplay.setAttribute("style","width: auto; height: auto;");
coreDisplay.appendChild(streamDisplay);
const video = document.createElement("video");
video.muted = true;
if(Browser().isSafariWebRTC()) {
video.setAttribute("playsinline", "");
video.setAttribute("webkit-playsinline", "");
}
streamDisplay.appendChild(video);
video.srcObject = stream;
2.5. Video tag event handlers creation
add() code
Where:
- local video playback is started
onendedevent handler is set up for video trackonresizeevent handler is set up for local video to adjust video displaying size to the container dimensions
video.onloadedmetadata = function (e) {
video.play();
};
stream.getTracks().forEach(function(track){
track.addEventListener("ended", function() {
video.srcObject.removeTrack(track);
//check video element has no tracks left
for (const [key, vTrack] of Object.entries(video.srcObject.getTracks())) {
if (vTrack.readyState !== "ended") {
return;
}
}
removeLocalDisplay(id);
});
});
video.addEventListener('resize', function (event) {
streamNameDisplay.innerHTML = "Name: " + name + "<br/>Max.resolution: " + video.videoWidth + "x" + video.videoHeight;
resizeVideo(event.target);
});
2.6. Video container addition to HTML page
add() code
localDisplays[id] = coreDisplay;
localDisplayDiv.appendChild(coreDisplay);
return coreDisplay;
3. Stop video and audio capturing
stop() code
const stop = function () {
for (const [key, value] of Object.entries(localDisplays)) {
removeLocalDisplay(value.id);
}
}
Room streams published displaying
1. Initialization
initRemoteDisplay() code
The initLocalDisplay() function returns the object to work with HTML5 tags to display remote video and audio streams
const initRemoteDisplay = function(mainDiv, room, peerConnection) {
const constants = SFU.constants;
const remoteParticipants = {};
...
const createRemoteDisplay = function(id, name, mainDiv) {
...
}
const stop = function() {
...
}
peerConnection.ontrack = ({transceiver}) => {
...
}
return {
stop: stop
}
}
2. Room events handling
2.1. ADD_TRACKS
initRemoteDisplay() code
Where:
- a new participant is added to participants list
- tracks quality information is added to tracks list
- elements to display remote audion and video are created
room.on(constants.SFU_ROOM_EVENT.ADD_TRACKS, function(e) {
console.log("Received ADD_TRACKS");
let participant = remoteParticipants[e.info.nickName];
if (!participant) {
participant = {};
participant.nickName = e.info.nickName;
participant.tracks = [];
participant.displays = [];
remoteParticipants[participant.nickName] = participant;
}
participant.tracks.push.apply(participant.tracks, e.info.info);
for (const pTrack of e.info.info) {
...
let display = createRemoteDisplay(participant.nickName, participant.nickName, mainDiv);
participant.displays.push(display);
if (pTrack.type === "VIDEO") {
display.videoMid = pTrack.mid;
display.setTrackInfo(pTrack);
} else if (pTrack.type === "AUDIO") {
display.audioMid = pTrack.mid;
}
}
...
});
2.2. REMOVE_TRACKS
initRemoteDisplay() code
Where:
- video elements are removed
- tracks data are dleteted from tracks list
}).on(constants.SFU_ROOM_EVENT.REMOVE_TRACKS, function(e) {
console.log("Received REMOVE_TRACKS");
const participant = remoteParticipants[e.info.nickName];
if (!participant) {
return;
}
for (const rTrack of e.info.info) {
for (let i = 0; i < participant.tracks.length; i++) {
if (rTrack.mid === participant.tracks[i].mid) {
participant.tracks.splice(i, 1);
break;
}
}
for (let i = 0; i < participant.displays.length; i++) {
let found = false;
const display = participant.displays[i];
if (display.audioMid === rTrack.mid) {
display.setAudio(null);
found = true;
} else if (display.videoMid === rTrack.mid) {
display.setVideo(null);
found = true;
}
if (found) {
if (!display.hasAudio() && !display.hasVideo()) {
display.dispose();
participant.displays.splice(i, 1);
}
break;
}
}
}
});
2.3. LEFT
initRemoteDisplay() code
Where:
- participant is removed from participants list
- video elements are removed
}).on(constants.SFU_ROOM_EVENT.LEFT, function(e) {
console.log("Received LEFT");
let participant = remoteParticipants[e.name];
if (!participant) {
return;
}
participant.displays.forEach(function(display){
display.dispose();
})
delete remoteParticipants[e.name];
});
2.4. TRACK_QUALITY_STATE
initRemoteDisplay() code
Where:
- track quality data are updated
}).on(constants.SFU_ROOM_EVENT.TRACK_QUALITY_STATE, function(e){
console.log("Received track quality state");
const participant = remoteParticipants[e.info.nickName];
if (!participant) {
return;
}
for (const rTrack of e.info.tracks) {
const mid = rTrack.mid;
for (let i = 0; i < participant.displays.length; i++) {
const display = participant.displays[i];
if (display.videoMid === mid) {
display.updateQualityInfo(rTrack.quality);
break;
}
}
}
});
3. Tags to display remote video creation
3.1. Container div creation
createRemoteDisplay() code
Where:
- container
divtag for participants streams is created - child container
divtag for a certain stream is created - container
divtag for quality switch buttons is created
const cell = document.createElement("div");
cell.setAttribute("class", "text-center");
cell.id = id;
mainDiv.appendChild(cell);
const streamNameDisplay = document.createElement("div");
streamNameDisplay.innerHTML = "Published by: " + name;
streamNameDisplay.setAttribute("style","width:auto; height:auto;");
streamNameDisplay.setAttribute("class","text-center");
cell.appendChild(streamNameDisplay);
const qualityDisplay = document.createElement("div");
qualityDisplay.setAttribute("style","width:auto; height:auto;");
qualityDisplay.setAttribute("class","text-center");
cell.appendChild(qualityDisplay);
let qualityDivs = [];
const rootDisplay = document.createElement("div");
rootDisplay.setAttribute("style","width:auto; height:auto;");
rootDisplay.setAttribute("class","text-center");
cell.appendChild(rootDisplay);
const streamDisplay = document.createElement("div");
streamDisplay.setAttribute("style","width:auto; height:auto;");
streamDisplay.setAttribute("class","text-center");
rootDisplay.appendChild(streamDisplay);
3.2. Video tag addition
setVideo() code
setVideo: function(stream) {
if (video) {
video.remove();
}
if (stream == null) {
video = null;
this.videoMid = undefined;
qualityDivs.forEach(function(div) {
div.remove();
});
qualityDivs = [];
return;
}
video = document.createElement("video");
video.muted = true;
if(Browser().isSafariWebRTC()) {
video.setAttribute("playsinline", "");
video.setAttribute("webkit-playsinline", "");
}
streamDisplay.appendChild(video);
video.srcObject = stream;
video.onloadedmetadata = function (e) {
video.play().then(function() {
video.muted = false;
});
};
video.addEventListener("resize", function (event) {
streamNameDisplay.innerHTML = "Published by: " + name + "<br/>Current resolution: " + video.videoWidth + "x" + video.videoHeight;
resizeVideo(event.target);
});
},
3.3. Audio tag addition
setAudio() code
setAudio: function(stream) {
if (audio) {
audio.remove();
}
if (!stream) {
audio = null;
this.audioMid = undefined;
return;
}
audio = document.createElement("audio");
audio.controls = "controls";
audio.muted = true;
audio.autoplay = true;
cell.appendChild(audio);
audio.srcObject = stream;
audio.onloadedmetadata = function (e) {
audio.play().then(function() {
audio.muted = false;
});
};
},
3.4. Setting up quality switcher
setTrackInfo() code
setTrackInfo: function(trackInfo) {
if (trackInfo && trackInfo.quality) {
for (let i = 0; i < trackInfo.quality.length; i++) {
const qualityDiv = document.createElement("button");
qualityDivs.push(qualityDiv);
qualityDiv.innerText = trackInfo.quality[i];
qualityDiv.setAttribute("style", "display:inline-block; border: solid; border-width: 1px");
qualityDiv.style.color = "red";
qualityDiv.addEventListener('click', function(){
console.log("Clicked on quality " + trackInfo.quality[i] + " trackId " + trackInfo.id);
if (qualityDiv.style.color === "red") {
return;
}
for (let c = 0; c < qualityDivs.length; c++) {
if (qualityDivs[c].style.color !== "red") {
qualityDivs[c].style.color = "gray";
}
}
qualityDiv.style.color = "blue";
room.changeQuality(trackInfo.id, trackInfo.quality[i]);
});
qualityDisplay.appendChild(qualityDiv);
}
}
},
3.5. Removing the container
dispose() code
dispose: function() {
cell.remove();
},
4. Subscription to ontrack PeerConnection event
PeerConnection.ontrack(), setAudio(), setVideo() code
Where:
- video or audio tag addition function is called when track is received
peerConnection.ontrack = ({transceiver}) => {
let rParticipant;
console.log("Attach remote track " + transceiver.receiver.track.id + " kind " + transceiver.receiver.track.kind + " mid " + transceiver.mid);
for (const [nickName, participant] of Object.entries(remoteParticipants)) {
for (const pTrack of participant.tracks) {
console.log("Participant " + participant.nickName + " track " + pTrack.id + " mid " + pTrack.mid);
if (pTrack.mid === transceiver.mid) {
rParticipant = participant;
break;
}
}
if (rParticipant) {
break;
}
}
if (rParticipant) {
for (const display of rParticipant.displays) {
if (transceiver.receiver.track.kind === "video") {
if (display.videoMid === transceiver.mid) {
let stream = new MediaStream();
stream.addTrack(transceiver.receiver.track);
display.setVideo(stream);
break;
}
} else if (transceiver.receiver.track.kind === "audio") {
if (display.audioMid === transceiver.mid) {
let stream = new MediaStream();
stream.addTrack(transceiver.receiver.track);
display.setAudio(stream);
break;
}
}
}
} else {
console.warn("Failed to find participant for track " + transceiver.receiver.track.id);
}
}
5. Playback stopping
stop() code
const stop = function() {
for (const [nickName, participant] of Object.entries(remoteParticipants)) {
participant.displays.forEach(function(display){
display.dispose();
});
delete remoteParticipants[nickName];
}
}