How to Record video on server using WebRTC

WebRTC (Web Real-Time Communication) is an open-source project designed to enable real-time communication between browsers and mobile applications through simple APIs. It supports video, audio, and data transmission.

Basic Steps to Record Video Using WebRTC

1. Establishing RTCPeerConnection

First, establish an RTCPeerConnection on the client side to transmit video streams. This is the foundation of WebRTC communication.

Example Code:

javascript
var peerConnection = new RTCPeerConnection();

2. Capturing Media Streams

Use navigator.mediaDevices.getUserMedia to capture video and audio streams from the client.

Example Code:

javascript
navigator.mediaDevices.getUserMedia({ video: true, audio: true })
.then(stream => {
  // You can display this stream locally or send it to others
})
.catch(error => {
  console.error("Failed to capture media stream", error);
});

3. Sending Media Streams

Send the captured media streams through RTCPeerConnection to the server or other clients.

Example Code:

javascript
peerConnection.addStream(stream);

Recording Video on the Server Side

For recording video on the server, a common approach is to use media servers (such as Kurento, Janus, or Mediasoup) to receive WebRTC streams and store them as video files. Below is a basic example illustrating how to implement this using Kurento Media Server.

1. Installing Kurento Media Server

First, install Kurento Media Server on the server. Download it from the Kurento website and follow the installation instructions.

2. Creating a Server-Side Application

Create a server-side application to handle WebRTC signaling and media streams, as well as manage media recording.

Example Code (using Node.js):

javascript
const kurento = require('kurento-client');

let kurentoClient = null;
function getKurentoClient(callback) {
    if (kurentoClient !== null) {
        return callback(null, kurentoClient);
    }

    kurento('ws://localhost:8888/kurento', function(error, client) {
        if (error) {
            return callback(error);
        }

        kurentoClient = client;
        callback(null, kurentoClient);
    });
}

function startRecording(callId, sdpOffer, callback) {
    getKurentoClient(function(error, client) {
        if (error) {
            return callback(error);
        }

        client.create('MediaPipeline', function(error, pipeline) {
            if (error) {
                return callback(error);
            }

            pipeline.create('WebRtcEndpoint', function(error, webRtcEndpoint) {
                if (error) {
                    return callback(error);
                }

                webRtcEndpoint.processOffer(sdpOffer);
                webRtcEndpoint.gatherCandidates();

                let recorder = pipeline.create('RecorderEndpoint', {uri: `file:///tmp/${callId}.webm`});
                webRtcEndpoint.connect(recorder);

                recorder.record();
                callback(null, webRtcEndpoint.generateAnswer());
            });
        });
    });
}

3. Handling Client Requests

On the client side, establish a connection with the server using WebRTC and send recording requests. The server saves the video stream to the specified file.

Summary

• WebRTC can capture and transmit video and audio streams on the client side.
• Using media servers (such as Kurento), you can receive and record these streams on the server side.
• Developers need to handle WebRTC signaling and media streams on the server side, as well as manage media recording.

By doing this, it is possible to record and store video within web applications, providing users with rich interactive experiences.