我正在使用 MVC ASP.Net 4 HTML5 开发一个项目（默认浏览器是 google-chrome v29.0.1547.57）我可以与这些工具交互并拍照，但只能使用前置摄像头，如何启用后置摄像头？ 平板的特点：三星 Galaxy Tab 2 希望你能帮帮我
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83781 次
5 回答
52
查看https://simpl.info/getusermedia/sources/显示如何使用
MediaStreamTrack.getSources(gotSources);
然后，您可以选择源并将其作为可选传递给 getUserMedia
var constraints = {
audio: {
optional: [{sourceId: audioSource}]
},
video: {
optional: [{sourceId: videoSource}]
}
};
navigator.getUserMedia(constraints, successCallback, errorCallback);
它现在在稳定版 Chrome 和移动版中完全可用（截至 v30）
于 2013-09-27T15:59:04.040 回答
27
可以在https://webrtc.github.io/samples/src/content/devices/input-output/找到演示。这将允许访问前后摄像头。
您会发现许多演示都依赖于已弃用的功能：
MediaStreamTrack.getSources()
从 Chrome 45 和 FireFox 39 开始，您将需要使用以下功能：
MediaDevices.enumerateDevices()
例子：
if (!navigator.mediaDevices || !navigator.mediaDevices.enumerateDevices) {
console.log("enumerateDevices() not supported.");
return;
}
// List cameras and microphones.
navigator.mediaDevices.enumerateDevices()
.then(function(devices) {
devices.forEach(function(device) {
console.log(device.kind + ": " + device.label +
" id = " + device.deviceId);
});
})
.catch(function(e) {
console.log(e.name + ": " + e.message);
});更多文档可以在这里找到：https ://developer.mozilla.org/en-US/docs/Web/API/MediaDevices/enumerateDevices
于 2016-02-18T11:39:15.373 回答
14
在三星 S8 上的 Chrome 中，我可以使用“面向模式”=“环境”从“后置摄像头”获取视频。默认似乎是“用户”（“前置”摄像头）
在打字稿中：
const video = document.getElementById("video");
const constraints = {
advanced: [{
facingMode: "environment"
}]
};
navigator.mediaDevices
.getUserMedia({
video: constraints
})
.then((stream) => {
video.src = window.URL.createObjectURL(stream);
video.play();
});
于 2017-07-28T11:13:32.090 回答
4
上次我开发该代码时，这里是我使用的版本：您直接调用代码中的函数 whichCamera 并指定哪个相机“用户”、“环境”或“计算机”'如果你在计算机上运行）
`//----------------------------------------------------------------------
// whichCamera(Type)
// For smartphone or tablet :
// Start the type={user,environment} camera.
// For computer it's simple :
// type = "computer".
//----------------------------------------------------------------------
var streamSrc, cameraType;
function whichCamera(type){
var cameraFacing;
cameraType = type;
if( type == "user")
cameraFacing = 0;
else if( type == "environment")
cameraFacing = 1;
else if( type == "computer"){
cameraFacing = 2;
}
console.log(type+" index : "+cameraFacing);
// Here we list all media devices, in order to choose between
// the front and the rear camera.
// videoDevices[0] : user Camera
// videoDevices[1] : environment Camera
// Then set the video resolution.
navigator.mediaDevices.enumerateDevices()
.then(devices => {
var videoDevices, videoDeviceIndex, constraints;
// Initialize the array wich will contain all video resources IDs.
// Most of devices have two video resources (Front & Rear Camera).
videoDevices = [0,0];
// Simple index to browse the videa resources array (videoDevices).
videoDeviceIndex = 0;
// devices.forEach(), this function will detect all media resources (Audio, Video) of the device
// where we run the application.
devices.forEach(function(device) {
console.log(device.kind + ": " + device.label +
" id = " + device.deviceId);
// If the kind of the media resource is video,
if (device.kind == "videoinput") {
// then we save it on the array videoDevices.
videoDevices[videoDeviceIndex++] = device.deviceId;
console.log(device.deviceId+" = "+videoDevices[videoDeviceIndex-1]);
}
});
console.log("Camera facing ="+cameraFacing+" ID = "+videoDevices[videoDeviceIndex-1]);
// Here we specified which camera we start,
// videoDevices[0] : Front Camera
// videoDevices[1] : Back Camera
if( cameraFacing != "computer"){
constraints = { deviceId: { exact: videoDevices[cameraFacing] }};
return navigator.mediaDevices.getUserMedia({ video:
constraints,
width: { min: 1280, ideal: 1600, max: 1920 },
height: { min: 720, ideal: 1200, max: 1080 }
}
);
}else
return navigator.mediaDevices.getUserMedia({ video: true });
})
// Then we retrieve the link to the video stream.
.then(stream => {
if (window.webkitURL) {
video.src = window.webkitURL.createObjectURL(stream);
localMediaStream = stream;
console.log(localMediaStream +" = "+ stream)
} else if (video.mozSrcObject !== undefined) {
video.mozSrcObject = stream;
console.log(video.mozSrcObject +" = "+ stream)
} else if (video.srcObject !== undefined) {
video.srcObject = stream;
console.log(video.srcObject +" = "+ stream)
} else {
video.src = stream;
console.log(video.src +" = "+ stream)
}
streamSrc = stream;
})
.catch(e => console.error(e));
}
于 2017-07-16T15:53:38.807 回答
0
//----------------------------------------------------------------------
// 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));
于 2017-03-20T08:32:10.210 回答