我正在使用navigator.mediaDevices.getUserMedia从Web浏览器中的摄像头设备打开MediaStream。我的应用程序想在WebAssembly中进行一些实时图像处理,为此,我需要直接从相机提供实时图像流。

我的解决方案在大多数设备上都运行良好,但是,在具有多个后置摄像头的设备上(例如Android版Google Chrome上的Samsung Galaxy S10),我遇到了问题。问题在于以下代码段:

const constraints = {
    audio: false,
    video: {
        width: { min: 640, ideal: 1280, max: 1920 },
        height: { min: 480, ideal: 720, max: 1080 },
        facingMode: { ideal: 'environment' },
    }
};
const stream = await navigator.mediaDevices.getUserMedia( constraints );

总是打开错误的相机-不支持自动对焦并且提供的图像对于我的代码来说太失真了。宽镜头相机非常适合风景摄影,但是对于条码和文本扫描来说却很糟糕。

如何使用MediaTrackConstraints选择正确的相机?我也尝试添加

focusMode: { ideal: 'continuous' }

约束(根据MDN documentation,这应该是图像轨迹的可能约束),但似乎不起作用。

我也尝试枚举所有设备(来自this SO answer),但我不知道如何正确选择正确的相机。

值得注意的是,此代码段:

const devices = await navigator.mediaDevices.enumerateDevices();
devices.forEach( ( device: MediaDeviceInfo ) => {
    console.log( "Found device: " + JSON.stringify( device ) );
});

产生以下控制台输出:
Found device: {"deviceId":"default","kind":"audioinput","label":"","groupId":"4852f187ff6a41e6d3fb3ba41c4897f46bd8ff153579da6fcb8f485432a32f66"}
Found device: {"deviceId":"86d4706b0bf160ff12fa75535173edcc68d4fa7ad5e00ec186cb1285ff22869d","kind":"audioinput","label":"","groupId":"c2cfc78763f7668263b0033c44d0f906ca0f33264ebfa6b96e9846265a21ff09"}
Found device: {"deviceId":"4d5fecf5a3eee5d41812bb6c34efe6d25342af9448628b006561c7385a22ca6c","kind":"audioinput","label":"","groupId":"7a86866423279d7b1e12dbe585a14a677a2f2df4e41ec5d388b6c90f7319e88d"}
Found device: {"deviceId":"b46cd34041256d2cf72ed6e8500f71beb698a01b8c47c7c04801c20c47630978","kind":"videoinput","label":"camera2 1, facing front","groupId":"b1bd1a6ed8a87cd07ca0fa84744ae515b1ab2bed61cc257765c37d3426269af7"}
Found device: {"deviceId":"39d63e8a9764261b73785c90beb58399997a5a4de56b3238fff6676c738331a6","kind":"videoinput","label":"camera2 3, facing front","groupId":"a23c2f0e311c0ca0c80a56a8b5ff7c1f8aa093df4f6ac080b051c1d95f60a94e"}
Found device: {"deviceId":"4d5fecf5a3eee5d41812bb6c34efe6d25342af9448628b006561c7385a22ca6c","kind":"videoinput","label":"camera2 2, facing back","groupId":"9b6b1a429e0db2d5094ddebe205d23309464650d8bcd585b2fe4ae8196b86f1c"}
Found device: {"deviceId":"86d4706b0bf160ff12fa75535173edcc68d4fa7ad5e00ec186cb1285ff22869d","kind":"videoinput","label":"camera2 0, facing back","groupId":"0de9556e1253763d7203b3b9e5db313cf89e05dd4bdd4ea0c5aff52d2952cf11"}
Found device: {"deviceId":"default","kind":"audiooutput","label":"","groupId":"default"}

正确的相机标有camera2 0, facing back标签,出于某种原因,Chrome始终选择camera2 2, facing back

当然,我可以按其标签对选择的相机进行硬编码,但这仅适用于Samsung Galaxy S10,并且我希望我的代码可以在具有多个后置摄像头的任何设备上使用。

我仍然没有尝试在iPhone 11 Pro(具有3个后置摄像头)上运行我的页面,但是它可以在Huawei Mate 30 Pro(4个后置摄像头)和Oppo Reno 9上正常运行。与Android上的Google Chrome有关。当我在Android版Firefox上打开页面时,浏览器会要求我在关闭摄像头权限对话框后且仅当多个摄像头满足给定约束时才选择应使用哪个摄像头。这很公平,因为它可以选择正确的相机进行扫描。我尚未尝试在Samsung Internet和Opera浏览器上打开页面(尚未)。

由于Google Chrome浏览器是Android上最流行的Web浏览器,因此,我什至会对Chrome特定的解决方案感到满意,但是,当然,最好的办法是获得适用于任何地方的答案。

编辑

根据jib的评论,我也尝试过使用focusDistance

focusDistance: { min: 0.05, ideal: 0.12, max: 0.3 }

并没有帮助。

我还尝试使用以下代码段记录getSettingsgetCapabilities的输出:

const devices = await navigator.mediaDevices.enumerateDevices();
let videoDevices: Array< MediaDeviceInfo > = [];
devices.forEach( ( device: MediaDeviceInfo ) => {
    if ( device.kind == 'videoinput' ) {
        console.log( "Found video device: " + JSON.stringify( device ) );
        videoDevices.push( device );
    }
});

console.log( '' );

// open every video device and dump its characteristics
for ( let i in videoDevices ) {
    const device = videoDevices[ i ];
    console.log( "Opening video device " + device.deviceId + " (" + device.label + ")" );
    const stream = await navigator.mediaDevices.getUserMedia( { video: { deviceId: { exact: device.deviceId } } } );
    stream.getVideoTracks().forEach( track => {
            const capabilities = track.getCapabilities();
            console.log( "Track capabilities: " + JSON.stringify( capabilities ) );
            const settings = track.getSettings();
            console.log( "Track settings: " + JSON.stringify( settings ) );
            console.log( '' );
        }
    )

    stream.getTracks().forEach( track => track.stop() );
}

输出如下:
Found video device: {"deviceId":"b46cd34041256d2cf72ed6e8500f71beb698a01b8c47c7c04801c20c47630978","kind":"videoinput","label":"camera2 1, facing front","groupId":"500dd57c6795399100a5ca8bf7f0cc4d7ed8b1bcb0877101d1bef7eb74921868"}
Found video device: {"deviceId":"39d63e8a9764261b73785c90beb58399997a5a4de56b3238fff6676c738331a6","kind":"videoinput","label":"camera2 3, facing front","groupId":"245693c8d34be77fe2f15be31b6054a19edb8ea9ed4116d966d2a03695bebebe"}
Found video device: {"deviceId":"4d5fecf5a3eee5d41812bb6c34efe6d25342af9448628b006561c7385a22ca6c","kind":"videoinput","label":"camera2 2, facing back","groupId":"c219595df2c2a430aea7007f64e6ce8fbfa783b038cf53069336361cc07e71af"}
Found video device: {"deviceId":"86d4706b0bf160ff12fa75535173edcc68d4fa7ad5e00ec186cb1285ff22869d","kind":"videoinput","label":"camera2 0, facing back","groupId":"96a68b6d6429786317e3b2c4773082604c5ab9a5cdaaf49c481878e40d67e987"}

Opening video device b46cd34041256d2cf72ed6e8500f71beb698a01b8c47c7c04801c20c47630978 (camera2 1, facing front)
Track capabilities: {"aspectRatio":{"max":3216,"min":0.0004528985507246377},"deviceId":"b46cd34041256d2cf72ed6e8500f71beb698a01b8c47c7c04801c20c47630978","facingMode":["user"],"frameRate":{"max":30,"min":0},"groupId":"500dd57c6795399100a5ca8bf7f0cc4d7ed8b1bcb0877101d1bef7eb74921868","height":{"max":2208,"min":1},"resizeMode":["none","crop-and-scale"],"width":{"max":3216,"min":1}}
Track settings: {"aspectRatio":1.3333333333333333,"deviceId":"b46cd34041256d2cf72ed6e8500f71beb698a01b8c47c7c04801c20c47630978","facingMode":"user","frameRate":30,"groupId":"500dd57c6795399100a5ca8bf7f0cc4d7ed8b1bcb0877101d1bef7eb74921868","height":480,"resizeMode":"none","width":640}

Opening video device 39d63e8a9764261b73785c90beb58399997a5a4de56b3238fff6676c738331a6 (camera2 3, facing front)
Track capabilities: {"aspectRatio":{"max":3968,"min":0.0003654970760233918},"deviceId":"39d63e8a9764261b73785c90beb58399997a5a4de56b3238fff6676c738331a6","facingMode":["user"],"frameRate":{"max":30,"min":0},"groupId":"245693c8d34be77fe2f15be31b6054a19edb8ea9ed4116d966d2a03695bebebe","height":{"max":2736,"min":1},"resizeMode":["none","crop-and-scale"],"width":{"max":3968,"min":1}}
Track settings: {"aspectRatio":1.3333333333333333,"deviceId":"39d63e8a9764261b73785c90beb58399997a5a4de56b3238fff6676c738331a6","facingMode":"user","frameRate":30,"groupId":"245693c8d34be77fe2f15be31b6054a19edb8ea9ed4116d966d2a03695bebebe","height":480,"resizeMode":"none","width":640}

Opening video device 4d5fecf5a3eee5d41812bb6c34efe6d25342af9448628b006561c7385a22ca6c (camera2 2, facing back)
Track capabilities: {"aspectRatio":{"max":4608,"min":0.00028935185185185184},"deviceId":"4d5fecf5a3eee5d41812bb6c34efe6d25342af9448628b006561c7385a22ca6c","facingMode":["environment"],"frameRate":{"max":60,"min":0},"groupId":"c219595df2c2a430aea7007f64e6ce8fbfa783b038cf53069336361cc07e71af","height":{"max":3456,"min":1},"resizeMode":["none","crop-and-scale"],"width":{"max":4608,"min":1}}
Track settings: {"aspectRatio":1.3333333333333333,"deviceId":"4d5fecf5a3eee5d41812bb6c34efe6d25342af9448628b006561c7385a22ca6c","facingMode":"environment","frameRate":60,"groupId":"c219595df2c2a430aea7007f64e6ce8fbfa783b038cf53069336361cc07e71af","height":480,"resizeMode":"none","width":640}

Opening video device 86d4706b0bf160ff12fa75535173edcc68d4fa7ad5e00ec186cb1285ff22869d (camera2 0, facing back)
Track capabilities: {"aspectRatio":{"max":4032,"min":0.00033068783068783067},"deviceId":"86d4706b0bf160ff12fa75535173edcc68d4fa7ad5e00ec186cb1285ff22869d","facingMode":["environment"],"frameRate":{"max":60,"min":0},"groupId":"96a68b6d6429786317e3b2c4773082604c5ab9a5cdaaf49c481878e40d67e987","height":{"max":3024,"min":1},"resizeMode":["none","crop-and-scale"],"width":{"max":4032,"min":1}}
Track settings: {"aspectRatio":1.3333333333333333,"deviceId":"86d4706b0bf160ff12fa75535173edcc68d4fa7ad5e00ec186cb1285ff22869d","facingMode":"environment","frameRate":60,"groupId":"96a68b6d6429786317e3b2c4773082604c5ab9a5cdaaf49c481878e40d67e987","height":480,"resizeMode":"none","width":640}

因此,除了最大可用分辨率不同之外,没有什么可区分camera2 0, facing backcamera2 2, facing back

我也尝试过使用三星Internet浏览器,它的行为与Google Chrome浏览器相同。

还有其他想法(除了遍历所有后置摄像头并选择分辨率最低的摄像头之外)?

最佳答案

我将所有摄像机按id放置到这样的数组中

      navigator.mediaDevices.enumerateDevices()
        .then(function(devices) {

        for(;devices[i];){
        if(devices[i].kind == "videoinput"){
            that.aCameras.push(   [devices[i].deviceId , devices[i].label]   )
            j++;
            }
        i++;
        }
    });

比通过按下按钮来翻转相机的事件,我做到了:

      var defaultsOpts = { audio: false, video: true };
      defaultsOpts.video = {
              deviceId: that.aCameras[that.currentCamera][0]
      };
      if ( that.aCameras.length-1 != that.currentCamera ){
          that.currentCamera++;
      }
      else{
          that.currentCamera = 0;
      }
      navigator.mediaDevices.getUserMedia(defaultsOpts)
            .then(function (stream) {
                  vid.srcObject = stream;
                  localstream = stream;
                  vid.play();
               });

       });

这样,而不是使用用户/环境,
我的问题解决了。
希望也会对您有帮助。
问候,
阿维

09-10 12:06
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