I don't know how to use the video library, but I would draw the video frame into a PGraphics Object (an Offscreen Buffer) and then save it from there.

if you add the name of the capture device.
for example myCapture.save();

like in this example :


import processing.video.*;
Capture myCapture;

void setup()
{
  size(200, 200);
  myCapture = new Capture(this, width, height, 30);
}

void captureEvent(Capture myCapture) {
  myCapture.read();
}

void draw() {
 
}

void keyPressed(){
  myCapture.save(frameCount+".png");

}

Thank you very much!