how to get better frameRate in motion detection

HI, I'm using following example for motion detection https://github.com/shiffman/LearningProcessing/blob/master/chp16_video/example_16_13_MotionPixels/example_16_13_MotionPixels.pde

This example was performed with camera(320,240) and its work nice but my canvas size is (1280,720) so the frameRate is getting very low near by 8 to 10fps and if i use camera with (640,480) then the feed is displaying twice seems like it duplicating.

i want to display my live feed in full resolution which is (1280,720) so how can i scale up my camera which is (640,480) to (1280,720) ? (frameRate can be better with that resolution?)

// Learning Processing
// Daniel Shiffman
// http://www.learningprocessing.com

// Example 16-13: Simple motion detection

import processing.video.*;
// Variable for capture device
Capture video;
// Previous Frame
PImage prevFrame;
// How different must a pixel be to be a "motion" pixel
float threshold = 50;

void setup() {
  size(1280, 720, P3D);
  video = new Capture(this, 640,480, 30);
  video.start();
  // Create an empty image the same size as the video
  prevFrame = createImage(video.width, video.height, RGB);
}

void captureEvent(Capture video) {
  // Save previous frame for motion detection!!
  prevFrame.copy(video, 0, 0, video.width, video.height, 0, 0, video.width, video.height); // Before we read the new frame, we always save the previous frame for comparison!
  prevFrame.updatePixels();  // Read image from the camera
  video.read();
}

void draw() {
  background(255);
  //pushMatrix();
  //scale(2.0);

  loadPixels();
  video.loadPixels();
  prevFrame.loadPixels();

  // Begin loop to walk through every pixel
  for (int x = 0; x < video.width; x ++ ) {
  for (int y = 0; y < video.height; y ++ ) {

//  for (int x = 440; x < 840; x ++ ) {
//   for (int y = 0; y < 400; y ++ ) {

      int loc = x + y*video.width;            // Step 1, what is the 1D pixel location
      color current = video.pixels[loc];      // Step 2, what is the current color
      color previous = prevFrame.pixels[loc]; // Step 3, what is the previous color

      // Step 4, compare colors (previous vs. current)
      float r1 = red(current);
      float g1 = green(current);
      float b1 = blue(current);
      float r2 = red(previous);
      float g2 = green(previous);
      float b2 = blue(previous);
      float diff = dist(r1, g1, b1, r2, g2, b2);

      // Step 5, How different are the colors?
      // If the color at that pixel has changed, then there is motion at that pixel.
      if (diff > threshold) {
        // If motion, display black

        pixels[loc] = color(0);
      } else {
        // If not, display white
        pixels[loc] = color(255);
      }
    }
  }
  updatePixels();

//popMatrix();

  stroke(255, 0, 0);
  rect(440, 0, 400, 400);
  surface.setTitle((int) frameRate + " motion");
}