Convert HTML5 Canvas Sequence to a Video File

Question

I'd like to convert an animation in HTML5 canvas to a video file that could be uploaded to YouTube. Is there any sort of screen capture API or something that could allow me to do this programatically?

Answer 1

Back to 2020

Solved it by using MediaRecorder API. It builds exactly to do that, among other things.

Here is a solution that recorded X ms of canvas video you can extend it with Buttons UI to start, pause, resume, stop, generate URL.

function record(canvas, time) {
    var recordedChunks = [];
    return new Promise(function (res, rej) {
        var stream = canvas.captureStream(25 /*fps*/);
        mediaRecorder = new MediaRecorder(stream, {
            mimeType: "video/webm; codecs=vp9"
        });
        
        //ondataavailable will fire in interval of `time || 4000 ms`
        mediaRecorder.start(time || 4000);

        mediaRecorder.ondataavailable = function (event) {
            recordedChunks.push(event.data);
             // after stop `dataavilable` event run one more time
            if (mediaRecorder.state === 'recording') {
                mediaRecorder.stop();
            }

        }

        mediaRecorder.onstop = function (event) {
            var blob = new Blob(recordedChunks, {type: "video/webm" });
            var url = URL.createObjectURL(blob);
            res(url);
        }
    })
}