Measuring Camera Activity to activate a Video in a second Frame

Hello,

I'm not very used to processing yet... I've just started making sketches a half year ago. It works very well, but nevertheless I have a problem:

I just understand how I can attach videos in Processing and manage how I can start, stop it and jump to a certain frame. I understand how I can grap the webcam but I don't know how I can measure activity within the captured picture.

I just found a side www.creativecoding.org with a code to understand how activity measuring works, but I think this is not the right solution (and I must confess that I don't understand the code completely).

The only thing I want is, if the cam measures a certain amount of activity that the video played in a second sketch will jump to a certain frame and if the activity's amount under a certain level that it will jump back.

I also have a second problem that I don't know how to attach two sketchs with each other.

can anybody help me... this might be a noob question but I really don't get further.

this is my sketch:

1. import processing.video.*;
   
   final int VID_WIDTH  = 640;
   final int VID_HEIGHT = 480;
   
   float[] buffer1 = new float[VID_WIDTH * VID_HEIGHT];
   float[] buffer2 = new float[buffer1.length];
   float[] buffer3 = new float[buffer1.length];
   
   float threshold = 400;
   
   Capture cam;
   
   void setup() {
     size (VID_WIDTH, VID_HEIGHT);
     cam = new Capture (this, VID_WIDTH, VID_HEIGHT);
     frameRate(15);
     cam.start();
   }
   
   void draw() {
     if (cam.available ()) {
       cam.read();
       background(0);
       image(cam, 0, 0);
       loadPixels();
       for (int i=0; i < cam.pixels.length; i++) {
         color c = cam.pixels[i];
         float sumC = red(c) + green(c) + blue(c);
         float deltaPixel = (buffer1[i] + buffer2[i] + buffer3[i]) / 3 - sumC;
         if (deltaPixel > threshold) {
           noStroke();
           fill(0, 255, 255);
           rectMode(CENTER);
           rect(320, 240, deltaPixel / 5 , deltaPixel / 5);
         }
         buffer3[i] = buffer2[i];
         buffer2[i] = buffer1[i];
         buffer1[i] = sumC;
       }
       loadPixels();
     }
   }

it works well but I don't know exactly how I can determine the value exactly... also it would be necessary that i can view the rect in a second window... the rest I would manage by myself I think...

many thanks!

Jerome