如何在翻转相机之前停止 WebRTC MediaRecorder 中所有以前的视频流？

Question

我的 PHP 网站有问题。在我的网站上，我使用来自 github 的 navigator.MediaDevices.getUserMedia() webrtc 示例进行视频录制，其工作正常，但目前我不想为用户提供切换设备摄像头的功能在移动浏览器上。我正在使用的代码如下，但它不能正常工作。

我的 html 代码是，

        <button  value="false" id="flipV" ><img src="<?= Yii::$app->request->baseUrl ?>/images/flip.png" height="22" width="22"></button>
        <video id="gum" autoplay muted></video>
        <video id="recorded" autoplay loop></video>

        <div>
            <button id="record" disabled>Start Recording</button>
            <button id="play" disabled>Play</button>
            <button id="download" disabled>Download</button>
        </div>

    </div>

我的js代码是，

'use strict';
var flipV = false;
$(document).ready(function () {
    $("body").on("click", "#flipV", function () {
        if (flipV == false) {
            flipV = true;
        } else {
            flipV = false;
        }
        startVideo();

    });
});
/* globals MediaRecorder */

var mediaSource = new MediaSource();
mediaSource.addEventListener('sourceopen', handleSourceOpen, false);
var mediaRecorder;
var recordedBlobs;
var sourceBuffer;

var gumVideo = document.querySelector('video#gum');
var recordedVideo = document.querySelector('video#recorded');

var recordButton = document.querySelector('button#record');
var playButton = document.querySelector('button#play');
var downloadButton = document.querySelector('button#download');
recordButton.onclick = toggleRecording;
playButton.onclick = play;
downloadButton.onclick = download;

// window.isSecureContext could be used for Chrome
var isSecureOrigin = location.protocol === 'https:' ||
        location.hostname === 'localhost';
if (!isSecureOrigin) {
    alert('getUserMedia() must be run from a secure origin: HTTPS or localhost.' +
            '\n\nChanging protocol to HTTPS');
    location.protocol = 'HTTPS';
}

var constraints = {audio: true, video: {facingMode: (flipV) ? "user" : "environment"}};

function handleSuccess(stream) {
    recordButton.disabled = false;
    console.log('getUserMedia() got stream: ', stream);
    window.stream = stream;
    if (window.URL) {
        gumVideo.src = window.URL.createObjectURL(stream);
    } else {
        gumVideo.src = stream;
    }
}

function handleError(error) {
    console.log('navigator.getUserMedia error: ', error);
}
function startVideo() {
    navigator.mediaDevices.getUserMedia(constraints).
            then(handleSuccess).catch(handleError);
}
//
function handleSourceOpen(event) {
    console.log('MediaSource opened');
    sourceBuffer = mediaSource.addSourceBuffer('video/webm; codecs="vp8"');
    console.log('Source buffer: ', sourceBuffer);
}

function toggleRecording() {
    if (recordButton.textContent === 'Start Recording') {
        startRecording();
    } else {
        stopRecording();
        recordButton.textContent = 'Start Recording';
        playButton.disabled = false;
        downloadButton.disabled = false;
    }
}

function startRecording() {
    recordedBlobs = [];
    var options = {mimeType: 'video/webm;codecs=vp9'};
    if (!MediaRecorder.isTypeSupported(options.mimeType)) {
        console.log(options.mimeType + ' is not Supported');
        options = {mimeType: 'video/webm;codecs=vp8'};
        if (!MediaRecorder.isTypeSupported(options.mimeType)) {
            console.log(options.mimeType + ' is not Supported');
            options = {mimeType: 'video/webm'};
            if (!MediaRecorder.isTypeSupported(options.mimeType)) {
                console.log(options.mimeType + ' is not Supported');
                options = {mimeType: ''};
            }
        }
    }
    try {
        mediaRecorder = new MediaRecorder(window.stream, options);
    } catch (e) {
        console.error('Exception while creating MediaRecorder: ' + e);
        alert('Exception while creating MediaRecorder: '
                + e + '. mimeType: ' + options.mimeType);
        return;
    }
    console.log('Created MediaRecorder', mediaRecorder, 'with options', options);
    recordButton.textContent = 'Stop Recording';
    playButton.disabled = true;
    downloadButton.disabled = true;
    mediaRecorder.onstop = handleStop;
    mediaRecorder.ondataavailable = handleDataAvailable;
    mediaRecorder.start(10); // collect 10ms of data
    console.log('MediaRecorder started', mediaRecorder);
}

function stopRecording() {
    mediaRecorder.stop();
    console.log('Recorded Blobs: ', recordedBlobs);
    recordedVideo.controls = true;
}

function play() {
    var superBuffer = new Blob(recordedBlobs, {type: 'video/webm'});
    recordedVideo.src = window.URL.createObjectURL(superBuffer);
}

function download() {
    var blob = new Blob(recordedBlobs, {type: 'video/webm'});
    var url = window.URL.createObjectURL(blob);
    var a = document.createElement('a');
    a.style.display = 'none';
    a.href = url;
    a.download = 'test.webm';
    document.body.appendChild(a);
    a.click();
    setTimeout(function () {
        document.body.removeChild(a);
        window.URL.revokeObjectURL(url);
    }, 100);
}

Answer 1

使用您从 getUserMedia 获得的流 stream.getTracks().forEach(function(track) { track.stop(); }) 这会停止所有设备（您可以检查桌面上的相机灯是否熄灭）并且（在移动设备上）需要在再次调用 getUserMedia 之前完成。