var pos = 0;

​

function setup() { 

  createCanvas(1000, 300);

  capture = createCapture(VIDEO);

  capture.size(400, 300);

  background(0);

} 

​

function draw() {

    capture.loadPixels();

  var w = capture.width;

  var h = capture.height;

  copy(capture, w/2, 0, 1, h, pos, 0, 1, h);

  pos = pos + 1;

  if (pos > width) {

   pos = 0; 

  }

}