Apply loadPixels() to video is extremely slow in OpenGL renderers

[Real-John-Cheung]

I tried to replace the black pixels in a video in P3D renderer but just calling loadPixels() seems to make the programme extremely slow But it's ok when it applied to still Images so I guess some problems with the video library? I used the newest beta release of the video library

To recreate the problem

Movie myMovie

void setup(){
  size (640,480,P3D);
  myMovie = new Movie (this,"mymovie.mp4");
  myMpvie.play();
}

void draw(){
  background(0,255,0);
  myMovie.loadPixels();
  image(myMovie,0,0);
}

void movieEvent(Movie m){
  m.read;
}

I run the above code, the movie play in like 0.3 FPS ( the movie is 320x240)

But with this

Movie myMovie

void setup(){
  size (640,480,P3D);
  myMovie = new Movie (this,"mymovie.mp4");
  myMpvie.play();
}

void draw(){
  background(0,255,0);
  //myMovie.loadPixels();
  image(myMovie,0,0);
}

void movieEvent(Movie m){
  m.read;
}

or this

Movie myMovie

void setup(){
  size (640,480);
  myMovie = new Movie (this,"mymovie.mp4");
  myMpvie.play();
}

void draw(){
  background(0,255,0);
  myMovie.loadPixels();
  image(myMovie,0,0);
}

void movieEvent(Movie m){
  m.read;
}

The movie is played in 24FPS, which is it's original frame rate.

I tried both on my MacBook Pro 15 2018 and My PC with AMD Ryzen 1600, AMD R9 380 and 16GB RAM so it seems not a hardware problem.....