Merge pull request #456 from JLLeitschuh/fix/ipCameraFrameGrabberHang

Fixes IP Cameras Hanging

Author: ThomasJClark

core/src/main/java/edu/wpi/grip/core/sources/CameraSource.java

@@ -21,6 +21,7 @@
 import java.net.URL;
 import java.util.Optional;
 import java.util.Properties;
+import java.util.concurrent.TimeUnit;
 import java.util.concurrent.TimeoutException;
 import java.util.logging.Level;
 import java.util.logging.Logger;
@@ -36,7 +37,24 @@ public class CameraSource extends Source implements StartStoppable {
      * {@link CameraSource.Factory#create(String)}, allowing this to work with basically any network video stream, this
      * default path allows the Axis M1011 cameras used in FRC to work when only an IP address is supplied.
      */
-    public final static String DEFAULT_IP_CAMERA_PATH = "/mjpg/video.mjpg";
+    public static final String DEFAULT_IP_CAMERA_PATH = "/mjpg/video.mjpg";
+    private static final int
+            /**
+             * Connecting to a device can take the most time.
+             * This should have a little bit of leeway.
+             *
+             * On a fairly decent computer with a great internet connection 7 seconds is more than enough.
+             * This value has been doubled to ensure that people running computers that may be older
+             * or have firewalls that will slow down connecting can still use the device.
+             */
+            IP_CAMERA_CONNECTION_TIMEOUT = 14;
+    private static final int
+            /**
+             * Reading from an existing connection shouldn't take that long.
+             * If it does we should really give up and try to reconnect.
+             */
+            IP_CAMERA_READ_TIMEOUT = 5;
+    private static final TimeUnit IP_CAMERA_TIMEOUT_UNIT = TimeUnit.SECONDS;
 
     private final static String DEVICE_NUMBER_PROPERTY = "deviceNumber";
     private final static String ADDRESS_PROPERTY = "address";
@@ -88,7 +106,11 @@ public FrameGrabber create(String addressProperty) throws MalformedURLException
             if (new URL(addressProperty).getPath().length() <= 1) {
                 addressProperty += DEFAULT_IP_CAMERA_PATH;
             }
-            return new IPCameraFrameGrabber(addressProperty);
+            return new IPCameraFrameGrabber(
+                    addressProperty,
+                    IP_CAMERA_CONNECTION_TIMEOUT,
+                    IP_CAMERA_READ_TIMEOUT,
+                    IP_CAMERA_TIMEOUT_UNIT);
         }
     }
 

core/src/main/java/edu/wpi/grip/core/sources/IPCameraFrameGrabber.java

@@ -33,13 +33,13 @@
 import javax.imageio.ImageIO;
 import java.awt.image.BufferedImage;
 import java.io.ByteArrayInputStream;
+import java.io.DataInputStream;
+import java.io.EOFException;
 import java.io.IOException;
-import java.io.InputStream;
 import java.net.MalformedURLException;
 import java.net.URL;
 import java.net.URLConnection;
-import java.util.List;
-import java.util.Map;
+import java.util.concurrent.TimeUnit;
 
 import static org.bytedeco.javacpp.opencv_core.*;
 import static org.bytedeco.javacpp.opencv_imgcodecs.cvDecodeImage;
@@ -69,37 +69,31 @@ public static void tryLoad() throws Exception {
         }
     }
 
-    private URL url;
+    private final URL url;
+    private final int connectionTimeout;
+    private final int readTimeout;
 
     private URLConnection connection;
-    private InputStream input;
+    private DataInputStream input;
     private byte[] pixelBuffer = new byte[1024];
-    private Map<String, List<String>> headerfields;
-    private String boundryKey;
     private IplImage decoded = null;
     private FrameConverter<IplImage> converter = new OpenCVFrameConverter.ToIplImage();
 
-    public IPCameraFrameGrabber(String urlstr) throws MalformedURLException {
+    public IPCameraFrameGrabber(String urlstr, int connectionTimeout, int readTimeout, TimeUnit unit) throws MalformedURLException {
+        super();
         url = new URL(urlstr);
+        this.connectionTimeout = Math.toIntExact(TimeUnit.MILLISECONDS.convert(connectionTimeout, unit));
+        this.readTimeout = Math.toIntExact(TimeUnit.MILLISECONDS.convert(readTimeout, unit));
     }
 
     @Override
     public void start() throws Exception {
 
         try {
             connection = url.openConnection();
-            headerfields = connection.getHeaderFields();
-            if (headerfields.containsKey("Content-Type")) {
-                List<String> ct = headerfields.get("Content-Type");
-                for (int i = 0; i < ct.size(); ++i) {
-                    String key = ct.get(i);
-                    int j = key.indexOf("boundary=");
-                    if (j != -1) {
-                        boundryKey = key.substring(j + 9); // FIXME << fragile
-                    }
-                }
-            }
-            input = connection.getInputStream();
+            connection.setConnectTimeout(connectionTimeout);
+            connection.setReadTimeout(readTimeout);
+            input = new DataInputStream(connection.getInputStream());
         } catch (IOException e) {
             // Make sure we rethrow the IO exception https://github.com/bytedeco/javacv/pull/300
             throw new Exception(e.getMessage(), e);
@@ -169,9 +163,9 @@ byte[] readImage() throws IOException {
             }
         }
         // find embedded jpeg in stream
-        String subheader = sb.toString();
+        final String subheader = sb.toString();
         //log.debug(subheader);
-        int contentLength = -1;
+
         // if (boundryKey == null)
         // {
         // Yay! - server was nice and sent content length
@@ -180,18 +174,17 @@ byte[] readImage() throws IOException {
 
         if (c0 < 0) {
             //log.info("no content length returning null");
-            return null;
+            throw new EOFException("The camera stream ended unexpectedly");
         }
 
         c0 += 16;
-        contentLength = Integer.parseInt(subheader.substring(c0, c1).trim());
+        final int contentLength = Integer.parseInt(subheader.substring(c0, c1).trim());
         //log.debug("Content-Length: " + contentLength);
 
         // adaptive size - careful - don't want a 2G jpeg
         ensureBufferCapacity(contentLength);
 
-        while (input.available() < contentLength) ;
-        input.read(pixelBuffer, 0, contentLength);
+        input.readFully(pixelBuffer, 0, contentLength);
         input.read();// \r
         input.read();// \n
         input.read();// \r