Does video.size() function doesn’t work properly for pixel manipulation

p5.js Coding Questions
1

<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<height;y++){
for(var x=0;x<width;x++){
let index=(x+y*width)*4;

  var r=video.pixels[index+0];
  var g=video.pixels[index+1];
  var b=video.pixels[index+2];
  var a=255;
  
  let br=(r+g+b)/3;
  pixels[index+0]=br;
  pixels[index+1]=br;
  pixels[index+2]=br;
  pixels[index+3]=255;
  
  
}

}
updatePixels();
}

please suggest what is wrong
/>