WPILIB Camera Code Crashing JVM

[adamzg]

To provide some clarity, we can see from the stack from the JVM that we're in com.ni.vision.NIVision._Priv_ReadJPEGString in wpi's lib when the jvm crashes...

Java frames: (J=compiled Java code, j=interpreted, Vv=VM code)
J 361  com.ni.vision.NIVision._Priv_ReadJPEGString_C(JJI)V (0 bytes) @ 0xb4815038 [0xb4814fe0+0x58]
J 357 C1 edu.wpi.first.wpilibj.vision.AxisCamera.getImage(Lcom/ni/vision/NIVision$Image;)Z (47 bytes) @ 0xb4813b88 [0xb48138f0+0x298]
J 326 C1 org.usfirst.frc3932.Robot.runCamera()V (42 bytes) @ 0xb480bac8 [0xb480ba90+0x38]
J 324 C1 org.usfirst.frc3932.Robot.teleopPeriodic()V (15 bytes) @ 0xb480b3b0 [0xb480b180+0x230]
j  edu.wpi.first.wpilibj.IterativeRobot.startCompetition()V+240
j  edu.wpi.first.wpilibj.RobotBase.main([Ljava/lang/String;)V+322

...and our runCamera method from that stack is...

public static AxisCamera currentCamera;
.
.
.
	private void runCamera(){
		try {
			currentCamera.getImage(image);
			CameraServer.getInstance().setImage(image);
		} catch (Exception e) {
			System.err.println("Failed to get image from camera");
			System.err.println(e.getStackTrace());
		}
	}
.
.
.

...so from our Robot.java class the last touch point for us is currentCamera.getImage in this case.

[adamzg]

Looking at the source for NIVision I think the .free() will work if used in a finally block. When we tried it the first time it didn't end up in a finally block and the image was being used as a member variable.

The NIVision class is calling C libraries that allocate memory outside the JVM so the correct steps we need are (pseudo code):

• Image image;
• try
• allocate image - image = NIVision.imaqCreateImage(NIVision.ImageType.IMAGE_ RGB, 0);
• use image - CameraServer.getInstance().setImage(image);
• finally
• free image - image.free();

Will repost when we understand better.

[adamzg]

Still crashing.

Here's the JVM version...

gsmin@roboRIO-3932-FRC:/usr/local/frc/bin# /usr/local/frc/JRE/bin/java -version -XX:+PrintCommandLineFlag
java version "1.8.0_06"
Java(TM) SE Embedded Runtime Environment (build 1.8.0_06-b23, profile compact2, headless)
Java HotSpot(TM) Embedded Client VM (build 25.6-b23, mixed mode)
admin@roboRIO-3932-FRC:/usr/local/frc/bin# cd /usr/local/frc/JRE/bin    
admin@roboRIO-3932-FRC:/usr/local/frc/JRE/bin# ls
java         keytool      rmid         rmiregistry
admin@roboRIO-3932-FRC:/usr/local/frc/JRE/bin# cd

...stats from top at time of crash...

Mem: 176600K used, 75372K free, 0K shrd, 93K buff, 3067729088K cached
CPU:   9% usr  12% sys   0% nic  76% idle   0% io   0% irq   0% sirq
Load average: 2.22 2.15 2.30 4/290 8550

[adamzg]

Here is our latest and cleanest code with all the logic encapsulated in a single class. This still crashes the JVM...

public class CameraConfig {
	private AxisCamera camera;
	private String URL;
	
	public CameraConfig(String URL){
		this.URL = URL;
		this.camera = new AxisCamera(this.URL);
    	camera.writeExposurePriority(50);
	}
	
	public void sendImage() {
		Image image = NIVision.imaqCreateImage(NIVision.ImageType.IMAGE_RGB, 0);
		try {
			camera.getImage(image);
			CameraServer.getInstance().setImage(image);		
		} catch (Exception e) {
			System.err.println("Failed to get image from camera");
			System.err.println(e.getStackTrace());
		} finally {
			image.free();
		}
	}
	
	public boolean exists() {
    	boolean flag = false;
    	Image image = NIVision.imaqCreateImage(NIVision.ImageType.IMAGE_RGB, 0);
    	try {
    		camera.getImage(image);
    		flag = true;
    	}
    	catch (Exception e){
    		
    	}
    	finally {
    		image.free();
    	}
    	return flag;
	}
}