Created
June 4, 2010 09:43
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An HTML5 Video Transformation Example for Benchmarking
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| <html> | |
| <head> | |
| <title>Video Transformation Benchmarking</title> | |
| <script type="text/javascript" src="benchmark.js"></script> | |
| </head> | |
| <body> | |
| <video id="video" src="myMovie.m4v"> | |
| </video> | |
| <canvas id="canvas1"> | |
| </canvas> | |
| <canvas id="canvas2"> | |
| </canvas> | |
| <script type="text/javascript"> | |
| benchmark.register(); | |
| </script> | |
| </body> | |
| </html> |
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| var benchmark = { | |
| 'video': null, | |
| 'videoWidth': null, | |
| 'videoHeight': null, | |
| 'canvas1': null, | |
| 'context1': null, | |
| 'canvas2': null, | |
| 'context2': null, | |
| 'register': function register() { | |
| this.video = document.getElementById("video"); | |
| this.canvas1 = document.getElementById("canvas1"); | |
| this.context1 = this.canvas1.getContext("2d"); | |
| this.canvas2 = document.getElementById("canvas2"); | |
| this.context2 = this.canvas2.getContext("2d"); | |
| this.video.addEventListener("loadeddata", function loadedData() { | |
| benchmark.videoWidth = this.videoWidth; | |
| benchmark.videoHeight = this.videoHeight; | |
| benchmark.canvas1.width = benchmark.videoWidth; | |
| benchmark.canvas1.height = benchmark.videoHeight; | |
| benchmark.canvas2.width = benchmark.videoWidth; | |
| benchmark.canvas2.height = benchmark.videoHeight; | |
| this.addEventListener("play", benchmark.monitor, false); | |
| }); | |
| }, | |
| 'monitor': function monitor() { | |
| if (benchmark.video.paused || benchmark.video.ended) { | |
| return; | |
| } | |
| benchmark.processFrame(); | |
| // call this function again immediately to get the next frame | |
| setTimeout(benchmark.monitor, 0); | |
| }, | |
| 'processFrame': function processFrame() { | |
| this.context1.drawImage(this.video, 0, 0); | |
| /* console.log('width: ' + this.videoWidth); */ | |
| /* console.log('height: ' + this.videoHeight); */ | |
| var frame = this.context1.getImageData(0, 0, this.videoWidth, this.videoHeight); | |
| var l = frame.data.length / 4; | |
| // invert colors one pixel at a time | |
| for (var k = 0; k < l; k ++) { | |
| frame.data[k * 4] = 255 - frame.data[k * 4]; // red | |
| frame.data[k * 4 + 1] = 255 - frame.data[k * 4 + 1]; // green | |
| frame.data[k * 4 + 2] = 255 - frame.data[k * 4 + 2]; // blue | |
| // ignore the alpha channel | |
| } | |
| this.context2.putImageData(frame, 0, 0); | |
| } | |
| }; |
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In Chrome 5.0.375.55 for OS X there appears to be little performance degradation from having to use an intermediate canvas element.