Question

使用getUserMedia API访问桌面摄像头时，它会打开网络摄像头。当然它对视频通信很有帮助。但是在移动设备中使用时会调用哪个摄像头。前置摄像头或后置摄像头？是否需要选择相机的代码？

Answer 1

有一个解决方案，用户可以选择其中一个摄像头。

通过评估以下代码中的sourceInfo.facing，您可以选择相机（“用户”或“环境”）（适用于当前Chrome＆gt; = 30）：https://simpl.info/getusermedia/sources/

'use strict';

var videoElement = document.querySelector('video');
var audioSelect = document.querySelector('select#audioSource');
var videoSelect = document.querySelector('select#videoSource');

navigator.getUserMedia = navigator.getUserMedia ||
  navigator.webkitGetUserMedia || navigator.mozGetUserMedia;

function gotSources(sourceInfos) {
  for (var i = 0; i !== sourceInfos.length; ++i) {
    var sourceInfo = sourceInfos[i];
    var option = document.createElement('option');
    option.value = sourceInfo.id;
    if (sourceInfo.kind === 'audio') {
      option.text = sourceInfo.label || 'microphone ' + (audioSelect.length + 1);
      audioSelect.appendChild(option);
    } else if (sourceInfo.kind === 'video') {
      option.text = sourceInfo.label || 'camera ' + (videoSelect.length + 1);
      videoSelect.appendChild(option);
    } else {
      console.log('Some other kind of source: ', sourceInfo);
    }
  }
}

if (typeof MediaStreamTrack === 'undefined'){
  alert('This browser does not support MediaStreamTrack.\n\nTry Chrome Canary.');
} else {
  MediaStreamTrack.getSources(gotSources);
}


function successCallback(stream) {
  window.stream = stream; // make stream available to console
  videoElement.src = window.URL.createObjectURL(stream);
  videoElement.play();
}

function errorCallback(error){
  console.log('navigator.getUserMedia error: ', error);
}

function start(){
  if (!!window.stream) {
    videoElement.src = null;
    window.stream.stop();
  }
  var audioSource = audioSelect.value;
  var videoSource = videoSelect.value;
  var constraints = {
    audio: {
      optional: [{sourceId: audioSource}]
    },
    video: {
      optional: [{sourceId: videoSource}]
    }
  };
  navigator.getUserMedia(constraints, successCallback, errorCallback);
}

audioSelect.onchange = start;
videoSelect.onchange = start;

start();

Answer 2

不幸的是，你不能（但是？）通过代码选择它。

Mozilla Firefox beta：当用户接受共享相机时，他/她还可以选择要分享的相机。
Chrome测试版：我只能使用面部相机。可能可配置，但我不知道如何......

编辑：在Chrome中，可以通过编程方式选择背面摄像头。请参阅此主题中Probot的下一个答案。

Answer 3

答案是肯定的，对于Android作为默认摄像头，前端（用户） caerma up。所以我建议这个脚本在前置摄像头和后置摄像头之间进行选择

    //----------------------------------------------------------------------
    //  Here we list all media devices, in order to choose between
    //  the front and the back camera.
    //      videoDevices[0] : Front Camera
    //      videoDevices[1] : Back Camera
    //  I used an array to save the devices ID 
    //  which i get using devices.forEach()
    //  Then set the video resolution.
    //----------------------------------------------------------------------
    navigator.mediaDevices.enumerateDevices()
    .then(devices => {
      var videoDevices = [0,0];
      var videoDeviceIndex = 0;
      devices.forEach(function(device) {
        console.log(device.kind + ": " + device.label +
          " id = " + device.deviceId);
        if (device.kind == "videoinput") {  
          videoDevices[videoDeviceIndex++] =  device.deviceId;    
        }
      });


      var constraints =  {width: { min: 1024, ideal: 1280, max: 1920 },
      height: { min: 776, ideal: 720, max: 1080 },
      deviceId: { exact: videoDevices[1]  } 
    };
    return navigator.mediaDevices.getUserMedia({ video: constraints });

  })
    .then(stream => {
      if (window.webkitURL) {
        video.src = window.webkitURL.createObjectURL(stream);
        localMediaStream = stream;
      } else if (video.mozSrcObject !== undefined) {
        video.mozSrcObject = stream;
      } else if (video.srcObject !== undefined) {
        video.srcObject = stream;
      } else {
        video.src = stream;
      }})
    .catch(e => console.error(e));

哪个相机会在移动设备中打开getUserMedia API？前面还是后面？

3 个答案: