Reland of Android: Make base interface for camera1 and camera2

webrtc/api/java/android/org/webrtc/CameraVideoCapturer.java

+/*
+ *  Copyright 2016 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+package org.webrtc;
+
+/**
+ * Base interface for camera1 and camera2 implementations. Extends VideoCapturer with a
+ * switchCamera() function. Also provides subinterfaces for handling camera events, and a helper
+ * class for detecting camera freezes.
+ */
+public interface CameraVideoCapturer extends VideoCapturer {
+  /**
+   * Camera events handler - can be used to be notifed about camera events. The callbacks are
+   * executed from an arbitrary thread.
+   */
+  public interface CameraEventsHandler {
+    // Camera error handler - invoked when camera can not be opened
+    // or any camera exception happens on camera thread.
+    void onCameraError(String errorDescription);
+
+    // Invoked when camera stops receiving frames.
+    void onCameraFreezed(String errorDescription);
+
+    // Callback invoked when camera is opening.
+    void onCameraOpening(int cameraId);
+
+    // Callback invoked when first camera frame is available after camera is started.
+    void onFirstFrameAvailable();
+
+    // Callback invoked when camera is closed.
+    void onCameraClosed();
+  }
+
+  /**
+   * Camera switch handler - one of these functions are invoked with the result of switchCamera().
+   * The callback may be called on an arbitrary thread.
+   */
+  public interface CameraSwitchHandler {
+    // Invoked on success. |isFrontCamera| is true if the new camera is front facing.
+    void onCameraSwitchDone(boolean isFrontCamera);
+
+    // Invoked on failure, e.g. camera is stopped or only one camera available.
+    void onCameraSwitchError(String errorDescription);
+  }
+
+  /**
+   * Switch camera to the next valid camera id. This can only be called while the camera is running.
+   * This function can be called from any thread.
+   */
+  void switchCamera(CameraSwitchHandler switchEventsHandler);
+
+  /**
+   * Helper class to log framerate and detect if the camera freezes. It will run periodic callbacks
+   * on the SurfaceTextureHelper thread passed in the ctor, and should only be operated from that
+   * thread.
+   */
+  public static class CameraStatistics {
+    private final static String TAG = "CameraStatistics";
+    private final static int CAMERA_OBSERVER_PERIOD_MS = 2000;
+    private final static int CAMERA_FREEZE_REPORT_TIMOUT_MS = 4000;
+
+    private final SurfaceTextureHelper surfaceTextureHelper;
+    private final CameraEventsHandler eventsHandler;
+    private int frameCount;
+    private int freezePeriodCount;
+    // Camera observer - monitors camera framerate. Observer is executed on camera thread.
+    private final Runnable cameraObserver = new Runnable() {
+      @Override
+      public void run() {
+        final int cameraFps = Math.round(frameCount * 1000.0f / CAMERA_OBSERVER_PERIOD_MS);
+        Logging.d(TAG, "Camera fps: " + cameraFps +".");
+        if (frameCount == 0) {
+          ++freezePeriodCount;
+          if (CAMERA_OBSERVER_PERIOD_MS * freezePeriodCount >= CAMERA_FREEZE_REPORT_TIMOUT_MS
+              && eventsHandler != null) {
+            Logging.e(TAG, "Camera freezed.");
+            if (surfaceTextureHelper.isTextureInUse()) {
+              // This can only happen if we are capturing to textures.
+              eventsHandler.onCameraFreezed("Camera failure. Client must return video buffers.");
+            } else {
+              eventsHandler.onCameraFreezed("Camera failure.");
+            }
+            return;
+          }
+        } else {
+          freezePeriodCount = 0;
+        }
+        frameCount = 0;
+        surfaceTextureHelper.getHandler().postDelayed(this, CAMERA_OBSERVER_PERIOD_MS);
+      }
+    };
+
+    public CameraStatistics(
+        SurfaceTextureHelper surfaceTextureHelper, CameraEventsHandler eventsHandler) {
+      if (surfaceTextureHelper == null) {
+        throw new IllegalArgumentException("SurfaceTextureHelper is null");
+      }
+      this.surfaceTextureHelper = surfaceTextureHelper;
+      this.eventsHandler = eventsHandler;
+      this.frameCount = 0;
+      this.freezePeriodCount = 0;
+      surfaceTextureHelper.getHandler().postDelayed(cameraObserver, CAMERA_OBSERVER_PERIOD_MS);
+    }
+
+    private void checkThread() {
+      if (Thread.currentThread() != surfaceTextureHelper.getHandler().getLooper().getThread()) {
+        throw new IllegalStateException("Wrong thread");
+      }
+    }
+
+    public void addFrame() {
+      checkThread();
+      ++frameCount;
+    }
+
+    public void release() {
+      checkThread();
+      surfaceTextureHelper.getHandler().removeCallbacks(cameraObserver);
+    }
+  }
+}