javascript - 如何在 Javascript 中选择合适的后置摄像头？
问题描述
我正在使用在网络浏览器中从相机设备navigator.mediaDevices.getUserMedia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运行良好，但是，我在具有多个后置摄像头的设备上遇到了问题，例如适用于 Android 的 Google Chrome 上的三星 Galaxy S10。问题是以下代码段：
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 );
总是打开一个错误的相机 - 广角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扭曲了。广角相机适用于风景摄影，但对于条形码和文本扫描来说很糟糕。
如何使用MediaTrackConstraints选择正确的相机？我也试过添加
focusMode: { ideal: 'continuous' }
约束（根据MDN 文档，这应该是图像轨道的可能约束），但它似乎不起作用。
我也尝试过枚举所有设备（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，这段代码片段：
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"}
正确的相机有标签camera2 0, facing back，由于某种原因，Chrome 总是选择camera2 2, facing back.
当然，我可以通过标签对相机的选择进行硬编码，但这仅适用于三星 Galaxy S10，我希望我的代码适用于任何具有多个后置摄像头的设备。
我还没有尝试在 iPhone 11 Pro（有 3 个后置摄像头）上运行我的页面，但它在华为 Mate 30 Pro（4 个后置摄像头）和 Oppo Reno 9 上运行正常。此外，问题似乎与 Android 上的 Google Chrome 相关。当我在 Firefox for Android 上打开我的页面时，浏览器会要求我在关闭相机权限对话框后选择应该使用哪个相机，并且只有在多个相机满足给定约束的情况下。这是相当公平的，因为它可以选择正确的相机来执行扫描。我还没有尝试在三星互联网和 Opera 浏览器上打开我的页面（还）。
由于 Google Chrome 是 Android 上最受欢迎的网络浏览器，我什至会对 Chrome 特定的解决方案感到满意，但当然，最好的办法是获得在任何地方都有效的答案。
编辑
根据jib的评论，我也尝试过使用focusDistancewith
focusDistance: { min: 0.05, ideal: 0.12, max: 0.3 }
它没有帮助。
我还尝试使用以下代码段记录getSettings和的输出：getCapabilities
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}
所以，除了最大可用分辨率不同外，没有什么可以区分camera2 0, facing back和的。camera2 2, facing back
我也尝试过使用三星互联网浏览器，它的行为与谷歌浏览器相同。
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那个）？
解决方案
I placed all the cameras by id into array like that
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++;
}
});Than on the event that flip the camera by pressing the button i did this:
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();
});
});like that instead of using user/enviroment, my problem was sort of solved.
hope will help you too.
Regards, Avi.
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