Requestvideoframecallback() simple instance

In the article 《

Browser video frame operation method  requestVideoFrameCallback()  brief introduction

》 The basic usage is introduced in , This article is to experience its use process , Some cool examples will be added later .

Click to start playing video 、 Pause video to read metadata . Draw a picture on the canvas that synchronizes the video frame rate with the actual video frame rate .

GITHUB

Contains the entire code example , The main codes are as follows ：

<template>
 <div id=&quot;app&quot;>
 <div class=&quot;player-container&quot;>
 <div class=&quot;title&quot;>requestVideoFrameCallback()  Simple example </div>
 <div class=&quot;item-container left&quot;>
 <div class=&quot;item-container-in&quot;>
 <video controls playsinline muted autoplay></video>
 <div class=&quot;item-header&quot;>Video</div>
 </div>
 </div>
 <div class=&quot;item-container right&quot;>
 <div class=&quot;item-container-in&quot;>
 <canvas></canvas>
 <div class=&quot;item-header&quot;>Canvas</div>
 </div>
 </div>
 <div class=&quot;fps-info&quot; v-if=&quot;fpsInfo&quot;>
 <strong>FPS：</strong>
 <i>{{ fpsInfo }}</i>
 </div>
 <div class=&quot;metadata-info&quot; v-if=&quot;metadata&quot;>
 <textarea readonly v-model=&quot;metadata&quot;></textarea>
 </div>
 </div>
 </div>
</template>

<script>
export default {
 name: &quot;App&quot;,
 data() {
 return {
 fpsInfo: null,
 metadata: null,
 };
 },
 mounted() {
 this.init();
 },
 methods: {
 init() {
 const video = document.querySelector(&quot;video&quot;);
 const canvas = document.querySelector(&quot;canvas&quot;);
 const ctx = canvas.getContext(&quot;2d&quot;);

 video.addEventListener(&quot;play&quot;, () => {
 if (
 !(&quot;requestVideoFrameCallback&quot; in HTMLVideoElement.prototype)
 ) {
 return alert(
 &quot; Your browser does not support interfaces  `Video.requestVideoFrameCallback()`&quot;
 );
 }
 });

 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 = &quot;https://vjs.zencdn.net/v/oceans.mp4&quot;;
 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: &quot;&quot;;
 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>


Execute the code and click to play the video , The picture on the right is synchronized with the video picture .

Utilization method  

requestVideoFrameCallback()

  Can be in WEB Use the camera to synchronize actions to 3D In the task model , Need to use AI To recognize the skeleton work of each frame in the video , Then sync to virtual 3D In the model . This is a common scene in virtual live broadcast .