Video Delay/Buffer in Processing 2.0

问题

I'm having a ton of trouble making a simple video delay in processing. I looked around on the internet and I keep finding the same bit of code and I can't get it to work at all. When I first tried it, it did nothing (at all). Here's my modified version (which at least seems to load frames into the buffer), I really have no idea why it doesn't work and I'm getting really tired of pulling out my hair. Please... please, for the love of god, please somebody point out the stupid mistake I'm making here. And now, without further delay (hah, get it?), the code:

import processing.video.*;

VideoBuffer vb;
Movie myMovie;
Capture cam;

float seconds = 1;

void setup() {
  size(320,240, P3D);
  frameRate(30);

  String[] cameras = Capture.list();

  if (cameras.length == 0) {
    println("There are no cameras available for capture.");
    exit();
  } else {
    println("Available cameras:");
    for (int i = 0; i < cameras.length; i++) {
      println(cameras[i]);
    }
  cam = new Capture(this, cameras[3]);
  cam.start(); 

  }

  vb = new VideoBuffer(90, width, height);

}

void draw() {

  if (cam.available() == true) {
    cam.read();
    vb.addFrame(cam);
  }

  image(cam, 0, 0);
  image( vb.getFrame(), 150, 0 );

}  



class VideoBuffer
{
  PImage[] buffer;

  int inputFrame = 0;
  int outputFrame = 0;
  int frameWidth = 0;
  int frameHeight = 0;

  VideoBuffer( int frames, int vWidth, int vHeight )
  {
    buffer = new PImage[frames];
    for(int i = 0; i < frames; i++)
    {
  this.buffer[i] = new PImage(vWidth, vHeight);
    }
    this.inputFrame = 0;
    this.outputFrame = 1;
    this.frameWidth = vWidth;
    this.frameHeight = vHeight;
  }

  // return the current "playback" frame.  
  PImage getFrame()
  {
    return this.buffer[this.outputFrame];
  } 

  // Add a new frame to the buffer.
  void addFrame( PImage frame )
  {
    // copy the new frame into the buffer.
    this.buffer[this.inputFrame] = frame;

    // advance the input and output indexes
    this.inputFrame++;
    this.outputFrame++;
    println(this.inputFrame + " " + this.outputFrame);

    // wrap the values..    
    if(this.inputFrame >= this.buffer.length)
    {
 this.inputFrame = 0;
    }
    if(this.outputFrame >= this.buffer.length)
    {
  this.outputFrame = 0;
    }
  }  
} 

回答1:

This works in Processing 2.0.1.

import processing.video.*;

Capture cam;
PImage[] buffer;
int w = 640;
int h = 360;
int nFrames = 60;
int iWrite = 0, iRead = 1;

void setup(){
  size(w, h);
  cam = new Capture(this, w, h);
  cam.start();
  buffer = new PImage[nFrames];
}

void draw() {
  if(cam.available()) {
    cam.read();
    buffer[iWrite] = cam.get();
    if(buffer[iRead] != null){
      image(buffer[iRead], 0, 0);
    }
    iWrite++;
    iRead++;
    if(iRead >= nFrames-1){
      iRead = 0;
    }
    if(iWrite >= nFrames-1){
      iWrite = 0;
    }
  }       
}

There is a problem inside your addFrame-Method. You just store a reference to the PImage object, whose pixels get overwritten all the time. You have to use buffer[inputFrame] = frame.get() instead of buffer[inputFrame] = frame. The get() method returns a copy of the image.

来源：https://stackoverflow.com/questions/17705781/video-delay-buffer-in-processing-2-0