How to get over 30FPS using Java in a Screen Capture Program?

Question

I'm currently using the Robot classes in Java to record the screen. However, it does not achieve the minimum of 30 frames per second. I'm not re-creating objects, and am being as efficient as I can, but I only average around 15 frames per second. Robot is simply not cutting it.

What can I use to capture the screen? I've tried Xuggle, but I can't seem to get that to capture fast enough either.

Answer 1

For operating systems following the X11 standard (Linux, FreeBSD, Solaris, etc.), we can do it this way via JavaCV and FFmpeg:

import com.googlecode.javacv.*;

public class ScreenGrabber {
    public static void main(String[] args) throws Exception {
        int x = 0, y = 0, w = 1024, h = 768; // specify the region of screen to grab
        FFmpegFrameGrabber grabber = new FFmpegFrameGrabber(":0.0+" + x + "," + y);
        grabber.setFormat("x11grab");
        grabber.setImageWidth(w);
        grabber.setImageHeight(h);
        grabber.start();

        CanvasFrame frame = new CanvasFrame("Screen Capture");
        while (frame.isVisible()) {
            frame.showImage(grabber.grab());
        }
        frame.dispose();
        grabber.stop();
    }
}

I don't know about Windows or Mac OS X, but I suspect we would need to access native APIs directly. Nevertheless, JavaCPP could help with that.

Answer 2

Build on @Samuel's answer, according to the official ffmpeg documentation you should be able to keep it pretty cross platform if you make the file parameter passed to the FFmpegFrameGrabber (which is really an input parameter that gets passed down as the -i option to ffmpeg) adhere to the different formats each device expects.

ie:

for Windows: dshow expects -i video="screen-capture-recorder"

for OSX: avfoundation expects -i "<screen device index>:"

and for Linux: x11grab expects -i :<display id>+<x>,<y>.

So just passing those values (arguments to -i) to the constructor and setting the format (via setFormat) accordingly should do the trick:

Examples:

for Windows:

new FFmpegFrameGrabber("video=\"screen-capture-recorder\"")
    .setFormat("dshow");

for OSX:

new FFmpegFrameGrabber("\"<screen device index>:\"")
    .setFormat("avfoundation");

for Linux:

new FFmpegFrameGrabber(":<display id>+<x>,<y>")
    .setFormat("x11grab");

PS: Haven't tested this fully so not sure if the quotes are actually necessary.