前言：
在文章《浏览器视频帧操作方法 requestVideoFrameCallback()》中介绍了基本的使用情况，本文来体验一下其使用过程，后续将增加一些酷炫的实例。
点击开始播放视频、暂停视频以读取元数据。在画布上绘制视频帧与实际视频帧速率同步的画面。
主要代码如下：
<template>
<div id="app">
<div class="player-container">
<div class="title">requestVideoFrameCallback() 简单实例</div>
<div class="item-container left">
<div class="item-container-in">
<video controls playsinline muted autoplay></video>
<div class="item-header">Video</div>
</div>
</div>
<div class="item-container right">
<div class="item-container-in">
<canvas></canvas>
<div class="item-header">Canvas</div>
</div>
</div>
<div class="fps-info" v-if="fpsInfo">
<strong>FPS：</strong>
<i>{{ fpsInfo }}</i>
</div>
<div class="metadata-info" v-if="metadata">
<textarea readonly v-model="metadata"></textarea>
</div>
</div>
</div>
</template>
<script>
export default {
name: "App",
data() {
return {
fpsInfo: null,
metadata: null,
};
},
mounted() {
this.init();
},
methods: {
init() {
const video = document.querySelector("video");
const canvas = document.querySelector("canvas");
const ctx = canvas.getContext("2d");
video.addEventListener("play", () => {
if (
!("requestVideoFrameCallback" in HTMLVideoElement.prototype)
) {
return alert(
"你的浏览器不支持接口 `Video.requestVideoFrameCallback()`"
);
}
});
let width = canvas.width;
let height = canvas.height;
let paintCount = 0;
let startTime = 0.0;
const updateCanvas = (now, metadata) => {
if (startTime === 0.0) {
startTime = now;
}
ctx.drawImage(video, 0, 0, width, height);
const elapsed = (now - startTime) / 1000.0;
const fps = (++paintCount / elapsed).toFixed(3);
this.fpsInfo = !isFinite(fps) ? 0 : fps;
this.metadata = JSON.stringify(metadata, null, 2);
video.requestVideoFrameCallback(updateCanvas);
};
video.src = "https://vjs.zencdn.net/v/oceans.mp4";
video.requestVideoFrameCallback(updateCanvas);
},
},
};
</script>
<style>
* {
-webkit-box-sizing: border-box;
box-sizing: border-box;
}
#app {
font-family: Avenir, Helvetica, Arial, sans-serif;
-webkit-font-smoothing: antialiased;
-moz-osx-font-smoothing: grayscale;
text-align: center;
color: #2c3e50;
background: #000;
}
.title {
position: absolute;
left: 0;
top: 30;
height: 60px;
line-height: 60px;
font-size: 24px;
color: #fff;
text-align: center;
width: auto;
right: 0px;
background-color: #000;
z-index: 100;
border-bottom: 1px rgba(255, 255, 255, 0.6) solid;
}
.player-container {
width: 100%;
height: 100vh;
overflow: hidden;
position: relative;
}
.item-container {
position: absolute;
width: 50%;
height: 100%;
padding: 50px;
top: 0px;
z-index: 1;
}
.item-container.left {
left: -5px;
border-right: 1px rgba(255, 255, 255, 0.6) solid;
}
.item-container-in {
width: 100%;
height: 100%;
position: relative;
}
.item-header {
position: absolute;
width: 100%;
height: 100%;
top: 100px;
z-index: 9;
color: rgba(255, 255, 255, 0.8);
font-weight: 700;
}
.item-container.right {
right: -5px;
border-left: 1px rgba(255, 255, 255, 0.6) solid;
}
.item-container canvas,
.item-container video {
position: absolute;
left: 50%;
top: 50%;
margin: -180px 0px 0px -320px;
width: 640px;
height: 360px;
}
.item-container::before {
position: absolute;
content: "";
width: 1px;
height: 100%;
overflow: hidden;
background-color: rgba(#fff, 0.6);
}
.fps-info {
position: absolute;
width: 200px;
height: 50px;
line-height: 20px;
font-family: Arial, Helvetica, sans-serif;
left: 50px;
bottom: 50px;
z-index: 10;
padding: 15px;
background-color: rgba(255, 255, 255, 0.5);
text-align: left;
color: #000;
}
.fps-info i {
font-style: normal;
}
.metadata-info {
position: absolute;
width: 600px;
height: 180px;
line-height: 20px;
font-family: Arial, Helvetica, sans-serif;
right: 50px;
bottom: 50px;
z-index: 10;
padding: 15px;
background-color: rgba(255, 255, 255, 0.5);
text-align: left;
color: #000;
}
.metadata-info textarea {
display: block;
width: 100%;
height: 100%;
background-color: transparent;
border: none;
}
</style>执行代码点击播放视频，右边的画面保持和视频画面同步。
利用方法 requestVideoFrameCallback() 可以在WEB中实现使用摄像头同步动作到3D任务模型中，需要用到AI来识别视频中的每一帧的骨骼工作，然后同步到虚拟3D模型中。这在虚拟直播中算是比较常见的场景。
到此这篇关于JS requestVideoFrameCallback() 简单案例的文章就介绍到这了,更多相关JS requestVideoFrameCallback内容请搜索编程网以前的文章或继续浏览下面的相关文章希望大家以后多多支持编程网！
