Exporting a video in p5.js
ccapture works well with p5.js to achieve the goal of recording what's displaying on a canvas.
Here is a demo of ccapture working with p5.js. The source code comes with the demo.
This method won't output laggy videos because it is not recording what you see on the screen, which can be laggy. Instead, it writes every frame into the video and tells the videos to play at a fixed frame rate. So even if it takes seconds to calculate just one frame, the output video will play smoothly without showing any delay between frames.
However, there is one caveat though. This method only works with Chrome.
Since p5.js is built on the Canvas API, in modern browsers, you can use a MediaRecorder to do this job.
const btn = document.querySelector('button'),
chunks = [];
function record() {
chunks.length = 0;
let stream = document.querySelector('canvas').captureStream(30),
recorder = new MediaRecorder(stream);
recorder.ondataavailable = e => {
if (e.data.size) {
chunks.push(e.data);
}
};
recorder.onstop = exportVideo;
btn.onclick = e => {
recorder.stop();
btn.textContent = 'start recording';
btn.onclick = record;
};
recorder.start();
btn.textContent = 'stop recording';
}
function exportVideo(e) {
var blob = new Blob(chunks);
var vid = document.createElement('video');
vid.id = 'recorded'
vid.controls = true;
vid.src = URL.createObjectURL(blob);
document.body.appendChild(vid);
vid.play();
}
btn.onclick = record;
// taken from pr.js docs
var x, y;
function setup() {
createCanvas(300, 200);
// Starts in the middle
x = width / 2;
y = height;
}
function draw() {
background(200);
// Draw a circle
stroke(50);
fill(100);
ellipse(x, y, 24, 24);
// Jiggling randomly on the horizontal axis
x = x + random(-1, 1);
// Moving up at a constant speed
y = y - 1;
// Reset to the bottom
if (y < 0) {
y = height;
}
}<script src="https://cdnjs.cloudflare.com/ajax/libs/p5.js/0.5.7/p5.min.js"></script>
<button>start recording</button><br>