How do I bring a video layer on top of a live capture and put it behind again

Hello, I'm new at Processing and I need some help. I want to start a new art project and a friend showed me that I can do it with Processing. I want to capture live video from the notebook webcam and if somebody presses a key, a video starts to play. And when the key is released, I want to the live capture screen be on top again. I can't figured out how to "kill" that video canvas and let the live capture shows and then to "kill" that live capture canvas and so on... I have two codes. The first, puts the video "layer" on top of the live capture "layer" and when it stops a still image of the video its shown. The second one, viceversa...

Thanks in advance!!

FIRST ONE

import processing.video.*;

Capture cam;
Movie video;

void setup() {
 size(640,480);
 cam = new Capture(this,640,480,30);
 video = new Movie(this,"ex.mp4");
 cam.start();
 }

void keyPressed() {
   video.loop();
   cam.stop();

}
void draw() {
  if (cam.available()) {
    cam.read();
    image(cam,0,0);
  } else video.read(); {
    image(video,0,0);
  }
}

void keyReleased() {
 video.stop();
 cam.start();

}

SECOND ONE

import processing.video.*;

Capture cam;
Movie video;

void setup() {
 size(640,480);
 cam = new Capture(this,640,480,30);
 video = new Movie(this,"ex.mp4");
 cam.start();
 }

void draw() {
  if (cam.available()) {
    cam.read();
    image(cam,0,0);
  }
  if (keyPressed == true) {
    video.loop();
    cam.stop();
    image(video,0,0);
  } else {
    video.stop();
    cam.start();
    image(cam,0,0);
  }

}