Video Pixels Changing While I Process Them

Processing Libraries
10 
/**
 * Synchronized Pixels Capture (1.0.0)
 * GoToLoop (2021-Oct-05)
 * Discourse.Processing.org/t/video-pixels-changing-while-i-process-them/32589/10
 */

import processing.video.Capture;

Capture cam;
PImage frame;

void setup() {
  size(640, 480);
  frame = get();

  cam = new Capture(this, width, height, "pipeline: autovideosrc");
  cam.start();
}

void draw() {
  surface.setTitle("Frame: " + frameCount + "   FPS: " + round(frameRate));

  synchronized (frame) {
    background(frame);
  }
}

void captureEvent(final Capture c) {
  c.read();

  final color[] pix = frame.pixels;
  final int len = pix.length;

  c.loadPixels();

  synchronized (frame) {
    arrayCopy(c.pixels, pix);

    for (int i = 0; i < len; pix[i++] ^= ~PImage.ALPHA_MASK);

    frame.updatePixels();
  }
}
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