html#
在页面上摆放一些元素，下面是主要部分
<div id="buttons"><button id="stop">停止</button><button id="b320">320x240</button><button id="b240-320">240x320</button><button id="b640">640x480</button><button id="b1280">1280x720</button><button id="b1920">1920x1080</button><button id="b2048">2048x1152</button></div><div id="videoblock" style="display: none"><p id="dimensions" style="height: 1em;"></p><video playsinline autoplay style="background: none;height: auto;width: auto;"></video><div id="width"><label>Width <span></span>px:</label><input type="range" min="0" max="7680" value="0"></div><input id="isFullWidth" type="checkbox">视频宽度100%<br><input id="aspectlock" type="checkbox">锁定宽高比<br></div><p id="msg" style="display: none;"></p>
button 一些按钮用来选择分辨率
videoblock 用来显示视频，默认隐藏
dimensions 用来现实视频的一些信息
video 宽高先设置为auto
#width input 滑动选择视频的宽度
isFullWidth 让video宽度为100%
msg 显示错误信息
js#
拿到一些元素
const dimensionsInfo = document.querySelector(’#dimensions’);
const video = document.querySelector(‘video’);
let stream;
const videoblock = document.querySelector(’#videoblock’); // 视频区域
const messagebox = document.querySelector(’#msg’);
const widthInput = document.querySelector(‘div#width input’);
const widthOutput = document.querySelector(‘div#width span’);
const aspectLock = document.querySelector(’#aspectlock’);
const fullWidSetting = document.querySelector(’#isFullWidth’);
启动视频#
先把拿到流的处理方法写出来
function gotStream(mediaStream) {
stream = window.stream = mediaStream; // 给控制台
video.srcObject = mediaStream;
messagebox.style.display = ‘none’;
videoblock.style.display = ‘block’;
const track = mediaStream.getVideoTracks()[0];
const constraints = track.getConstraints();
console.log('当前constraints: ’ + JSON.stringify(constraints));
if (constraints && constraints.width && constraints.width.exact) {
widthInput.value = constraints.width.exact;widthOutput.textContent = constraints.width.exact;
} else if (constraints && constraints.width && constraints.width.min) {
widthInput.value = constraints.width.min;widthOutput.textContent = constraints.width.min;
}
}
拿到视频流后，track.getConstraints()获取信息，显示出当前信息并修改ui。
以按钮320为例
document.querySelector(’#b320’).onclick = () => {
const c320 = {
video: { width: { exact: 320 }, height: { exact: 240 } }
};
startPlay(c320);
};
function startPlay(constraints) {
stopStream();
clearMsg();
videoblock.style.display = ‘none’;
navigator.mediaDevices.getUserMedia(constraints)
.then(gotStream).catch(e => {showErrMsg('getUserMedia报错 ' + e, JSON.stringify(constraints));});
}
function stopStream() {
if (stream) {
stream.getTracks().forEach(track => {track.stop();});
}
}
定义配置c320，设定宽为320，高伟240
先把视频停下来
调用getUserMedia并把参数配置传进去
还可以监听video的变化
let currentWidth = 0;
let currentHeight = 0;
// 显示视频尺寸信息
function displayVideoDimensions(whereSeen) {
if (video.videoWidth) {
dimensionsInfo.innerText = '实际video尺寸: ' + video.videoWidth +'x' + video.videoHeight + 'px.';if (currentWidth !== video.videoWidth ||currentHeight !== video.videoHeight) {console.log(whereSeen + ': ' + dimensionsInfo.innerText);currentWidth = video.videoWidth;currentHeight = video.videoHeight;}
} else {
dimensionsInfo.innerText = '拿不到video的宽度';
}
}
// 载入meta信息
video.onloadedmetadata = () => {
displayVideoDimensions(‘loadedmetadata’);
};
// 修改了尺寸
video.onresize = () => {
displayVideoDimensions(‘resize’);
};
载入信息或者尺寸改变的时候显示出来。
定义了多种常见的分辨率
document.querySelector(’#b640’).onclick = () => {
const c640 = {
video: { width: { exact: 640 }, height: { exact: 480 } }
};
startPlay(c640);
};
document.querySelector(’#b1280’).onclick = () => {
const c1280 = {
video: { width: { exact: 1280 }, height: { exact: 720 } }
};
startPlay(c1280);
};
滑动调整#
我们放置了一个input，type=“range”，它可以左右滑动。滑动的时候我们改变视频设置的宽度。宽度信息也显示在界面上。
widthInput.onchange = onConstraintChange;
function onConstraintChange(e) {
widthOutput.textContent = e.target.value;
const track = window.stream.getVideoTracks()[0];
let constraints;
if (aspectLock.checked) {
constraints = {width: { exact: e.target.value },aspectRatio: {exact: video.videoWidth / video.videoHeight}};
} else {
constraints = { width: { exact: e.target.value } };
}
clearMsg();
console.log('使用配置 ’ + JSON.stringify(constraints));
track.applyConstraints(constraints)
.then(() => {console.log('配置成功');displayVideoDimensions('applyConstraints');}).catch(err => {showErrMsg('配置失败 ', err.name);});
}
亚马逊测评 www.yisuping.cn
