Switching Camera Views

Technical Java
1

I would like to know if it is possible to change the current camera display programmatically. What I would like to achieve as the end result is having two cameras, one forward, one backward, that switch based on the direction the robot is currently moving (with a manual override).

I currently am able to manually change the view by selecting the desired view from the drop-down menu on the dashboard, and may display both simultaneously if I wish.

2

You can do something like this (edited from the screenstepspage):

public void robotInit() {
            new Thread(() -> {
                UsbCamera camera1 = CameraServer.getInstance().startAutomaticCapture(0);
                camera1.setResolution(640, 480);
                UsbCamera camera2 = CameraServer.getInstance().startAutomaticCapture(1);
                camera2.setResolution(640, 480);
                
                CvSink cvSink1 = CameraServer.getInstance().getVideo(camera1);
                CvSink cvSink2 = CameraServer.getInstance().getVideo(camera2);
                CvSource outputStream = CameraServer.getInstance().putVideo("Switcher", 640, 480);
                
                Mat image = new Mat();
                
                while(!Thread.interrupted()) {
                    if(/*switcher button logic*/){
                      cvSink1.grabFrame(image);
                    } else{
                      cvSink2.grabFrame(image);
                    }
                    
                    outputStream.putFrame(image);
                }
            }).start();
    }

I’m tired, so this is all I can think of now. The code may not be entirely right, but the general idea should work. There probably is a much better/simpler/more efficient way that I have no clue about.

3

The above code gets you about 90% of the way their, but still runs into USB bandwidth issues. I modified the code slightly and now have switching cameras working very well, with the occasional error message, but nothing fatal.

public void robotInit() {
    	
    	Thread t = new Thread(() -> {
    		
    		boolean allowCam1 = false;
    		
    		UsbCamera camera1 = CameraServer.getInstance().startAutomaticCapture(0);
            camera1.setResolution(320, 240);
            camera1.setFPS(30);
            UsbCamera camera2 = CameraServer.getInstance().startAutomaticCapture(1);
            camera2.setResolution(320, 240);
            camera2.setFPS(30);
            
            CvSink cvSink1 = CameraServer.getInstance().getVideo(camera1);
            CvSink cvSink2 = CameraServer.getInstance().getVideo(camera2);
            CvSource outputStream = CameraServer.getInstance().putVideo("Switcher", 320, 240);
            
            Mat image = new Mat();
            
            while(!Thread.interrupted()) {
            	
            	if(oi.getGamepad().getRawButton(9)) {
            		allowCam1 = !allowCam1;
            	}
            	
                if(allowCam1){
                  cvSink2.setEnabled(false);
                  cvSink1.setEnabled(true);
                  cvSink1.grabFrame(image);
                } else{
                  cvSink1.setEnabled(false);
                  cvSink2.setEnabled(true);
                  cvSink2.grabFrame(image);     
                }
                
                outputStream.putFrame(image);
            }
            
        });
        t.start();
4

When I attempt to add the switcher, I get a large number of errors and warnings. Something like unable to set FPS or unable to set resolution. It’s really irritating, the errors go away when I comment out the switching code, but the dashboard still shows >30 FPS for both cameras, and higher resolution (even though my code sets the resolution and FPS lower).

I am using two Lifecam 3000s if it matters.

5

On the dashboard are you streaming the Switcher? If you try to stream just the default USB cameras, you will get errors.

7