WebRTC web page recording audio and video tutorial

Introduction : I recently studied the principle and implementation of audio and video recording on web pages, and now I will make a summary of the current implementation methods.

content

• Related API
• Method introduction
• Practical drill

Related API

To achieve this function involves two js api.

• getUserMedia

• MediaRecorder

Method introduction

getUserMedia

Use getUserMediathis interface to get the camera and microphone of the device and return an Promiseobject.

grammarvar stream = navigator.mediaDevices.getUserMedia(constraints);

constraintsIt includes the following spellings:

• Request audio and video

const constraints = {
    audio: true,
    video: true
}
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• Request a specific device video resolution

const constraints = {
    audio: true,
    video: {
        width: { 
            min: 1280 
        },
        height: { 
            min: 720 
        }
    }
}
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• Use front camera (default)

const constraints = {
    audio: true,
    video: {
        facingMode: "user"
    }
}
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• Force the use of the rear camera

const constraints = {
    audio: true,
    video: {
        facingMode: {
            exact: "environment"
        }
    }
}
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E.g:

const constraints = {
    audio: true,
    video: {
        width: 1280,
        height: 720
    }
};

async function createMedia() {
    try {
        let stream = await navigator.mediaDevices.getUserMedia(constraints);
        var video = document.querySelector('video');
        video.srcObject = stream;
        video.onloadedmetadata = function (e) {
            video.play();
        };
    } catch (error) {
        console.log(`getUserMedia: ${error}`);
    }
}

createMedia();
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Of course, streamthere are other methods that can be used, such as

• addTrackAdd a new track to the stream
• getAudioTracksContains all audio tracks in the stream
• getVideoTracksfor each video track included in the media stream
• getTracksall objects in this stream

MediaRecorder

This is one way to record a stream.

• startstart recording
• stopend recording
• onstopListen to the end event
• ondataavailablereal-time streaming data

grammarvar mediaRecorder = new MediaRecorder(stream[, options]);

E.g

// stream就是上面获取的音视频流
let options = {
    audioBitsPerSecond : 128000,
    videoBitsPerSecond : 2500000,
}
let mediaRecorder = new MediaRecorder(stream, options);

// 实时的录制流数据
mediaRecorder.ondataavailable = function (e) {  
    console.log(e.data);
}

// 监听停止录制事件并生成播放地址
mediaRecorder.onstop = function () {
    let blob = new Blob(chunks, {'type': mediaRecorder.mimeType});
    let url = window.URL.createObjectURL(blob);
    console.log(url);
}
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Practical drill

• page structure section

<audio controls src=""></audio>
<video controls src="" style="width: 100%;"></video>
<button id="start">开始音频</button>
<button id="stop">结束音频</button>
<button id="play">播放音频</button>
<button id="startVideo">开始视频</button>
<button id="stopVideo">结束视频</button>
<button id="playVideo">播放视频</button>
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• js part

Get element added event

// 获取按钮
let audioStart = document.querySelector('#start');
let audioStop = document.querySelector('#stop');
let audioPlay = document.querySelector('#play');
let startVideo = document.querySelector('#startVideo');
let stopVideo = document.querySelector('#stopVideo');
let playVideo = document.querySelector('#playVideo');

// 音频操作
audioStart.onclick = function () {  
    start('audio');
}

audioStop.onclick = function () {  
    stop('audio');
}

audioPlay.onclick = function () {  
    document.querySelector('audio').play();
}

// 视频操作
startVideo.onclick = function () {  
    start('video');
}

stopVideo.onclick = function () {  
    stop('video');
}

playVideo.onclick = function () {  
    document.querySelector('video').play();
}
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start recording

// 开始录制
function start (type) {
    let option = type == 'audio' ? {
        audio: true
    } : {
        video: true,
    }
    createMedia(type, option);
}
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stop recording

// 停止录制
function stop (type) {
    mediaRecorder.stop();
}

function stopSet (type) {  
    if (type == 'audio') {
        stream.getAudioTracks()[0].stop();
        stream = null;
    } else {
        stream.getVideoTracks()[0].stop();
    }
    stream = null;
    mediaRecorder = null;
    chunks = [];
    meida = null;
}
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How to pass

// 全局参数
let stream = null,mediaRecorder = null,chunks = [], media = null;
async function createMedia (type, option) {  
    try {
        // 获取媒体流
        stream = await navigator.mediaDevices.getUserMedia(option);
        media = document.querySelector(type);
        if (type === 'video') {
            media.srcObject = stream;
        }
        console.log(type, stream);

        // 录制流
        let options = {
            audioBitsPerSecond : 128000,
            videoBitsPerSecond : 2500000,
        }
        mediaRecorder = new MediaRecorder(stream, options);
        console.log(type, mediaRecorder);

        mediaRecorder.ondataavailable = function (e) {  
            chunks.push(e.data);
        }

        mediaRecorder.start();

        // 停止录制
        mediaRecorder.onstop = function () {
            let blob = new Blob(chunks, {'type': mediaRecorder.mimeType});
            let url = window.URL.createObjectURL(blob);
            if (type === 'video') {
                media.srcObject = null;
            }
            media.src = url;
            stopSet(type);
        }

    } catch (error) {
        console.log('getUserMedia： ', error);
    }
}
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see the effect

If you want to experience it, you can turn on this audio and video recording , which is better for mobile phones.

Well, today's tutorial is introduced here, bye!