# Read from 2 videos at the same time

Hi, for my algorithm i want to process first frame from `videoA` and first frame from `videoB` at the same time and so on until the last frame.

In my implementation i have a problem,in theory it should read alternately like this frame 1 from `videoA`, frame 1 from `videoB`, frame 2 from `video A`, frame 2 from `videoB` and so on, but in reality the second `videoB` it starts to read after `video A` already read 6-8 frames, i don’t know why videoB it starts to read with so much delay.

Is it possible to read at the same time from 2 different videos without any delay?

``````import processing.video.*;
Movie videoA, videoB;

void setup() {
size(1600, 600);
videoA = new Movie(this, "videoL1.avi");
videoB = new Movie(this, "videoR1.avi");

videoA.play();
videoB.play();
}

void draw() {

image(videoA, 0, 0, 800, 600);
image(videoB, 800, 0, 800, 600);

}

int counterL=0;
int counterR=0;
boolean a=true;
void movieEvent(Movie c) {
if (c==videoA) {
println("left image: "+counterL);
counterL++;
} else if (c==videoB) {
println("right image: "+counterR);
counterR++;
}
}
boolean stop=false;
void keyPressed() {

if (key=='s')
{
if (stop==false)
{
videoA.pause();
videoB.pause();
stop=true;
} else
{
stop=false;
videoA.play();
videoB.play();
}
}
}
``````
1 Like

This is just a guess, but maybe the time it takes to `play()` the videos in the beginning causes the delay. Try to create them both on seperate threads and check when those finished:

``````boolean videoAPlayed, videoBPlayed;

void setup() {
// ...

// Instead of directly playing them:
}

void playVideoA() {
videoA.play();
videoAPlayed = true;
}

void playVideoB() {
videoB.play();
videoBPlayed = true;
}

void draw() {
if (videoAPlayed)
image(videoA, 0, 0, 800, 600);
if (videoBPlayed)
image(videoB, 800, 0, 800, 600);
}
``````
2 Likes

I’ve just come up w/ a FiFo Queue solution using 2 ArrayDeque containers to store previous video frames of each Movie:

The trick is to only remove() a PImage frame of each container as a pair when none isEmpty():

This way the 2 videos are displayed synched to their corresponding frame number.

And its source code can be viewed on this link here:

And in this forum as well:

``````/**
* FiFo Sync Frame Pair (v1.0.1)
* GoToLoop (2020/Apr/20)
*
* GitHub.com/GoToLoop/FiFo-Sync-Frame-Pair
*/

import processing.video.Movie;

import java.util.Queue;
import java.util.ArrayDeque;

static final String VID_1 = "videoL1.avi", VID_2 = "videoR1.avi";
static final int W = 1024, H = 768, WW = W >> 1, HH = H >> 1;

final Queue<PImage> framesA = new ArrayDeque<PImage>();
final Queue<PImage> framesB = new ArrayDeque<PImage>();

Movie videoA, videoB;

void settings() {
size(W, HH);
}

void setup() {
videoA = new Movie(this, VID_1);
videoB = new Movie(this, VID_2);

videoA.play();
videoB.play();
}

void draw() {
if (framesB.isEmpty() || framesA.isEmpty())  return;

final PImage frameA = framesA.remove();
final PImage frameB = framesB.remove();

set(0, 0, frameA);
set(WW, 0, frameB);
}

void movieEvent(final Movie m) {