Created
May 20, 2013 16:19
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Experiment creating thumbnails of MP4 videos using the HTML5 Filereader API. Currently, the loading of videos in rapid succession fails with a decoding error, and if too many videos are processed concurrently, the display driver crashes.
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| <!DOCTYPE html> | |
| <html lang="en"> | |
| <head> | |
| <link href="https://netdna.bootstrapcdn.com/twitter-bootstrap/2.3.1/css/bootstrap-combined.min.css" rel="stylesheet"> | |
| <script src="http://code.jquery.com/jquery.js"></script> | |
| <script src="https://rawgithub.com/caolan/async/master/lib/async.js"></script> | |
| <script src="https://netdna.bootstrapcdn.com/twitter-bootstrap/2.3.1/js/bootstrap.min.js"></script> | |
| <script> | |
| window.URL = window.URL || window.webkitURL; | |
| function handleFiles(files) { | |
| async.eachSeries(files, do_video); | |
| } | |
| function do_video(file, callback) { | |
| var url = window.URL.createObjectURL(file); | |
| screenshotOfFile(url, function (elem) { | |
| $('<li class="span4"></li>').appendTo('.thumbnails').append(elem); | |
| callback(); | |
| }, callback); | |
| } | |
| function screenshotOfFile(url, callback, error) { | |
| var video = $("video")[0]; | |
| video.addEventListener("loadeddata", function () { | |
| this.removeEventListener("loadeddata", arguments.callee); | |
| this.removeEventListener("error", arguments.callee); | |
| var elem = screenshot(this); | |
| callback(elem); | |
| }); | |
| video.addEventListener("error", function () { | |
| this.removeEventListener("error", arguments.callee); | |
| console.log(this.error); | |
| this.removeEventListener("loadeddata", arguments.callee); | |
| this.src = ''; | |
| error(); | |
| }); | |
| video.src = url; | |
| } | |
| function screenshot(video) { | |
| var canvas = document.createElement("canvas"); | |
| canvas.height = video.videoHeight; | |
| canvas.width = video.videoWidth; | |
| var ctx = canvas.getContext("2d"); | |
| ctx.drawImage(video, 0, 0, canvas.width, canvas.height); | |
| canvas.style.width = 'inherit'; | |
| canvas.style.height = 'inherit'; | |
| return canvas; | |
| } | |
| </script> | |
| </head> | |
| <body> | |
| <video id="player"></video> | |
| <input type="file" id="fileElem" multiple onchange="handleFiles(this.files)"> | |
| <ul class="thumbnails"> </ul> | |
| </body> | |
| </html> |
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