problem usi video.size() function when creating software mirrors in p5.js

does video.size() function doesn’t work properly for pixel manipulation.
the moment i am using it I am getting a black screen in the canvas though the video is running in the browser
I am sending the code:
let video;

function setup() {
createCanvas(320, 240);
video=createCapture(VIDEO);
pixelDensity(1);
video.size(320,240);

}

function draw() {
background(220);
loadPixels();
video.loadPixels();
for(var y=0;y