sdk/android/api/org/webrtc/EglRenderer.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;

import android.graphics.Bitmap;
import android.graphics.Matrix;
import android.graphics.SurfaceTexture;
import android.opengl.GLES20;
import android.os.Handler;
import android.os.HandlerThread;
import android.os.Looper;
import android.view.Surface;
import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.Locale;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;

/**
 * Implements org.webrtc.VideoRenderer.Callbacks by displaying the video stream on an EGL Surface.
 * This class is intended to be used as a helper class for rendering on SurfaceViews and
 * TextureViews.
 */
public class EglRenderer implements VideoRenderer.Callbacks, VideoSink {
  private static final String TAG = "EglRenderer";
  private static final long LOG_INTERVAL_SEC = 4;
  private static final int MAX_SURFACE_CLEAR_COUNT = 3;

  public interface FrameListener { void onFrame(Bitmap frame); }

  private static class FrameListenerAndParams {
    public final FrameListener listener;
    public final float scale;
    public final RendererCommon.GlDrawer drawer;
    public final boolean applyFpsReduction;

    public FrameListenerAndParams(FrameListener listener, float scale,
        RendererCommon.GlDrawer drawer, boolean applyFpsReduction) {
      this.listener = listener;
      this.scale = scale;
      this.drawer = drawer;
      this.applyFpsReduction = applyFpsReduction;
    }
  }

  private class EglSurfaceCreation implements Runnable {
    private Object surface;

    // TODO(bugs.webrtc.org/8491): Remove NoSynchronizedMethodCheck suppression.
    @SuppressWarnings("NoSynchronizedMethodCheck")
    public synchronized void setSurface(Object surface) {
      this.surface = surface;
    }

    @Override
    // TODO(bugs.webrtc.org/8491): Remove NoSynchronizedMethodCheck suppression.
    @SuppressWarnings("NoSynchronizedMethodCheck")
    public synchronized void run() {
      if (surface != null && eglBase != null && !eglBase.hasSurface()) {
        if (surface instanceof Surface) {
          eglBase.createSurface((Surface) surface);
        } else if (surface instanceof SurfaceTexture) {
          eglBase.createSurface((SurfaceTexture) surface);
        } else {
          throw new IllegalStateException("Invalid surface: " + surface);
        }
        eglBase.makeCurrent();
        // Necessary for YUV frames with odd width.
        GLES20.glPixelStorei(GLES20.GL_UNPACK_ALIGNMENT, 1);
      }
    }
  }

  protected final String name;

  // |renderThreadHandler| is a handler for communicating with |renderThread|, and is synchronized
  // on |handlerLock|.
  private final Object handlerLock = new Object();
  private Handler renderThreadHandler;

  private final ArrayList<FrameListenerAndParams> frameListeners = new ArrayList<>();

  // Variables for fps reduction.
  private final Object fpsReductionLock = new Object();
  // Time for when next frame should be rendered.
  private long nextFrameTimeNs;
  // Minimum duration between frames when fps reduction is active, or -1 if video is completely
  // paused.
  private long minRenderPeriodNs;

  // EGL and GL resources for drawing YUV/OES textures. After initilization, these are only accessed
  // from the render thread.
  private EglBase eglBase;
  private final VideoFrameDrawer frameDrawer = new VideoFrameDrawer();
  private RendererCommon.GlDrawer drawer;
  private final Matrix drawMatrix = new Matrix();

  // Pending frame to render. Serves as a queue with size 1. Synchronized on |frameLock|.
  private final Object frameLock = new Object();
  private VideoFrame pendingFrame;

  // These variables are synchronized on |layoutLock|.
  private final Object layoutLock = new Object();
  private float layoutAspectRatio;
  // If true, mirrors the video stream horizontally.
  private boolean mirror;

  // These variables are synchronized on |statisticsLock|.
  private final Object statisticsLock = new Object();
  // Total number of video frames received in renderFrame() call.
  private int framesReceived;
  // Number of video frames dropped by renderFrame() because previous frame has not been rendered
  // yet.
  private int framesDropped;
  // Number of rendered video frames.
  private int framesRendered;
  // Start time for counting these statistics, or 0 if we haven't started measuring yet.
  private long statisticsStartTimeNs;
  // Time in ns spent in renderFrameOnRenderThread() function.
  private long renderTimeNs;
  // Time in ns spent by the render thread in the swapBuffers() function.
  private long renderSwapBufferTimeNs;

  // Used for bitmap capturing.
  private GlTextureFrameBuffer bitmapTextureFramebuffer;

  private final Runnable logStatisticsRunnable = new Runnable() {
    @Override
    public void run() {
      logStatistics();
      synchronized (handlerLock) {
        if (renderThreadHandler != null) {
          renderThreadHandler.removeCallbacks(logStatisticsRunnable);
          renderThreadHandler.postDelayed(
              logStatisticsRunnable, TimeUnit.SECONDS.toMillis(LOG_INTERVAL_SEC));
        }
      }
    }
  };

  private final EglSurfaceCreation eglSurfaceCreationRunnable = new EglSurfaceCreation();

  /**
   * Standard constructor. The name will be used for the render thread name and included when
   * logging. In order to render something, you must first call init() and createEglSurface.
   */
  public EglRenderer(String name) {
    this.name = name;
  }

  /**
   * Initialize this class, sharing resources with |sharedContext|. The custom |drawer| will be used
   * for drawing frames on the EGLSurface. This class is responsible for calling release() on
   * |drawer|. It is allowed to call init() to reinitialize the renderer after a previous
   * init()/release() cycle.
   */
  public void init(final EglBase.Context sharedContext, final int[] configAttributes,
      RendererCommon.GlDrawer drawer) {
    synchronized (handlerLock) {
      if (renderThreadHandler != null) {
        throw new IllegalStateException(name + "Already initialized");
      }
      logD("Initializing EglRenderer");
      this.drawer = drawer;

      final HandlerThread renderThread = new HandlerThread(name + "EglRenderer");
      renderThread.start();
      renderThreadHandler = new Handler(renderThread.getLooper());
      // Create EGL context on the newly created render thread. It should be possibly to create the
      // context on this thread and make it current on the render thread, but this causes failure on
      // some Marvel based JB devices. https://bugs.chromium.org/p/webrtc/issues/detail?id=6350.
      ThreadUtils.invokeAtFrontUninterruptibly(renderThreadHandler, () -> {
        // If sharedContext is null, then texture frames are disabled. This is typically for old
        // devices that might not be fully spec compliant, so force EGL 1.0 since EGL 1.4 has
        // caused trouble on some weird devices.
        if (sharedContext == null) {
          logD("EglBase10.create context");
          eglBase = EglBase.createEgl10(configAttributes);
        } else {
          logD("EglBase.create shared context");
          eglBase = EglBase.create(sharedContext, configAttributes);
        }
      });
      renderThreadHandler.post(eglSurfaceCreationRunnable);
      final long currentTimeNs = System.nanoTime();
      resetStatistics(currentTimeNs);
      renderThreadHandler.postDelayed(
          logStatisticsRunnable, TimeUnit.SECONDS.toMillis(LOG_INTERVAL_SEC));
    }
  }

  public void createEglSurface(Surface surface) {
    createEglSurfaceInternal(surface);
  }

  public void createEglSurface(SurfaceTexture surfaceTexture) {
    createEglSurfaceInternal(surfaceTexture);
  }

  private void createEglSurfaceInternal(Object surface) {
    eglSurfaceCreationRunnable.setSurface(surface);
    postToRenderThread(eglSurfaceCreationRunnable);
  }

  /**
   * Block until any pending frame is returned and all GL resources released, even if an interrupt
   * occurs. If an interrupt occurs during release(), the interrupt flag will be set. This function
   * should be called before the Activity is destroyed and the EGLContext is still valid. If you
   * don't call this function, the GL resources might leak.
   */
  public void release() {
    logD("Releasing.");
    final CountDownLatch eglCleanupBarrier = new CountDownLatch(1);
    synchronized (handlerLock) {
      if (renderThreadHandler == null) {
        logD("Already released");
        return;
      }
      renderThreadHandler.removeCallbacks(logStatisticsRunnable);
      // Release EGL and GL resources on render thread.
      renderThreadHandler.postAtFrontOfQueue(() -> {
        if (drawer != null) {
          drawer.release();
          drawer = null;
        }
        frameDrawer.release();
        if (bitmapTextureFramebuffer != null) {
          bitmapTextureFramebuffer.release();
          bitmapTextureFramebuffer = null;
        }
        if (eglBase != null) {
          logD("eglBase detach and release.");
          eglBase.detachCurrent();
          eglBase.release();
          eglBase = null;
        }
        eglCleanupBarrier.countDown();
      });
      final Looper renderLooper = renderThreadHandler.getLooper();
      // TODO(magjed): Replace this post() with renderLooper.quitSafely() when API support >= 18.
      renderThreadHandler.post(() -> {
        logD("Quitting render thread.");
        renderLooper.quit();
      });
      // Don't accept any more frames or messages to the render thread.
      renderThreadHandler = null;
    }
    // Make sure the EGL/GL cleanup posted above is executed.
    ThreadUtils.awaitUninterruptibly(eglCleanupBarrier);
    synchronized (frameLock) {
      if (pendingFrame != null) {
        pendingFrame.release();
        pendingFrame = null;
      }
    }
    logD("Releasing done.");
  }

  /**
   * Reset the statistics logged in logStatistics().
   */
  private void resetStatistics(long currentTimeNs) {
    synchronized (statisticsLock) {
      statisticsStartTimeNs = currentTimeNs;
      framesReceived = 0;
      framesDropped = 0;
      framesRendered = 0;
      renderTimeNs = 0;
      renderSwapBufferTimeNs = 0;
    }
  }

  public void printStackTrace() {
    synchronized (handlerLock) {
      final Thread renderThread =
          (renderThreadHandler == null) ? null : renderThreadHandler.getLooper().getThread();
      if (renderThread != null) {
        final StackTraceElement[] renderStackTrace = renderThread.getStackTrace();
        if (renderStackTrace.length > 0) {
          logD("EglRenderer stack trace:");
          for (StackTraceElement traceElem : renderStackTrace) {
            logD(traceElem.toString());
          }
        }
      }
    }
  }

  /**
   * Set if the video stream should be mirrored or not.
   */
  public void setMirror(final boolean mirror) {
    logD("setMirror: " + mirror);
    synchronized (layoutLock) {
      this.mirror = mirror;
    }
  }

  /**
   * Set layout aspect ratio. This is used to crop frames when rendering to avoid stretched video.
   * Set this to 0 to disable cropping.
   */
  public void setLayoutAspectRatio(float layoutAspectRatio) {
    logD("setLayoutAspectRatio: " + layoutAspectRatio);
    synchronized (layoutLock) {
      this.layoutAspectRatio = layoutAspectRatio;
    }
  }

  /**
   * Limit render framerate.
   *
   * @param fps Limit render framerate to this value, or use Float.POSITIVE_INFINITY to disable fps
   *            reduction.
   */
  public void setFpsReduction(float fps) {
    logD("setFpsReduction: " + fps);
    synchronized (fpsReductionLock) {
      final long previousRenderPeriodNs = minRenderPeriodNs;
      if (fps <= 0) {
        minRenderPeriodNs = Long.MAX_VALUE;
      } else {
        minRenderPeriodNs = (long) (TimeUnit.SECONDS.toNanos(1) / fps);
      }
      if (minRenderPeriodNs != previousRenderPeriodNs) {
        // Fps reduction changed - reset frame time.
        nextFrameTimeNs = System.nanoTime();
      }
    }
  }

  public void disableFpsReduction() {
    setFpsReduction(Float.POSITIVE_INFINITY /* fps */);
  }

  public void pauseVideo() {
    setFpsReduction(0 /* fps */);
  }

  /**
   * Register a callback to be invoked when a new video frame has been received. This version uses
   * the drawer of the EglRenderer that was passed in init.
   *
   * @param listener The callback to be invoked. The callback will be invoked on the render thread.
   *                 It should be lightweight and must not call removeFrameListener.
   * @param scale    The scale of the Bitmap passed to the callback, or 0 if no Bitmap is
   *                 required.
   */
  public void addFrameListener(final FrameListener listener, final float scale) {
    addFrameListener(listener, scale, null, false /* applyFpsReduction */);
  }

  /**
   * Register a callback to be invoked when a new video frame has been received.
   *
   * @param listener The callback to be invoked. The callback will be invoked on the render thread.
   *                 It should be lightweight and must not call removeFrameListener.
   * @param scale    The scale of the Bitmap passed to the callback, or 0 if no Bitmap is
   *                 required.
   * @param drawer   Custom drawer to use for this frame listener or null to use the default one.
   */
  public void addFrameListener(
      final FrameListener listener, final float scale, final RendererCommon.GlDrawer drawerParam) {
    addFrameListener(listener, scale, drawerParam, false /* applyFpsReduction */);
  }

  /**
   * Register a callback to be invoked when a new video frame has been received.
   *
   * @param listener The callback to be invoked. The callback will be invoked on the render thread.
   *                 It should be lightweight and must not call removeFrameListener.
   * @param scale    The scale of the Bitmap passed to the callback, or 0 if no Bitmap is
   *                 required.
   * @param drawer   Custom drawer to use for this frame listener or null to use the default one.
   * @param applyFpsReduction This callback will not be called for frames that have been dropped by
   *                          FPS reduction.
   */
  public void addFrameListener(final FrameListener listener, final float scale,
      final RendererCommon.GlDrawer drawerParam, final boolean applyFpsReduction) {
    postToRenderThread(() -> {
      final RendererCommon.GlDrawer listenerDrawer = drawerParam == null ? drawer : drawerParam;
      frameListeners.add(
          new FrameListenerAndParams(listener, scale, listenerDrawer, applyFpsReduction));
    });
  }

  /**
   * Remove any pending callback that was added with addFrameListener. If the callback is not in
   * the queue, nothing happens. It is ensured that callback won't be called after this method
   * returns.
   *
   * @param runnable The callback to remove.
   */
  public void removeFrameListener(final FrameListener listener) {
    if (Thread.currentThread() == renderThreadHandler.getLooper().getThread()) {
      throw new RuntimeException("removeFrameListener must not be called on the render thread.");
    }
    final CountDownLatch latch = new CountDownLatch(1);
    postToRenderThread(() -> {
      latch.countDown();
      final Iterator<FrameListenerAndParams> iter = frameListeners.iterator();
      while (iter.hasNext()) {
        if (iter.next().listener == listener) {
          iter.remove();
        }
      }
    });
    ThreadUtils.awaitUninterruptibly(latch);
  }

  // VideoRenderer.Callbacks interface.
  @Override
  public void renderFrame(VideoRenderer.I420Frame frame) {
    VideoFrame videoFrame = frame.toVideoFrame();
    onFrame(videoFrame);
    videoFrame.release();
  }

  // VideoSink interface.
  @Override
  public void onFrame(VideoFrame frame) {
    synchronized (statisticsLock) {
      ++framesReceived;
    }
    final boolean dropOldFrame;
    synchronized (handlerLock) {
      if (renderThreadHandler == null) {
        logD("Dropping frame - Not initialized or already released.");
        return;
      }
      synchronized (frameLock) {
        dropOldFrame = (pendingFrame != null);
        if (dropOldFrame) {
          pendingFrame.release();
        }
        pendingFrame = frame;
        pendingFrame.retain();
        renderThreadHandler.post(this ::renderFrameOnRenderThread);
      }
    }
    if (dropOldFrame) {
      synchronized (statisticsLock) {
        ++framesDropped;
      }
    }
  }

  /**
   * Release EGL surface. This function will block until the EGL surface is released.
   */
  public void releaseEglSurface(final Runnable completionCallback) {
    // Ensure that the render thread is no longer touching the Surface before returning from this
    // function.
    eglSurfaceCreationRunnable.setSurface(null /* surface */);
    synchronized (handlerLock) {
      if (renderThreadHandler != null) {
        renderThreadHandler.removeCallbacks(eglSurfaceCreationRunnable);
        renderThreadHandler.postAtFrontOfQueue(() -> {
          if (eglBase != null) {
            eglBase.detachCurrent();
            eglBase.releaseSurface();
          }
          completionCallback.run();
        });
        return;
      }
    }
    completionCallback.run();
  }

  /**
   * Private helper function to post tasks safely.
   */
  private void postToRenderThread(Runnable runnable) {
    synchronized (handlerLock) {
      if (renderThreadHandler != null) {
        renderThreadHandler.post(runnable);
      }
    }
  }

  private void clearSurfaceOnRenderThread(float r, float g, float b, float a) {
    if (eglBase != null && eglBase.hasSurface()) {
      logD("clearSurface");
      GLES20.glClearColor(r, g, b, a);
      GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT);
      eglBase.swapBuffers();
    }
  }

  /**
   * Post a task to clear the surface to a transparent uniform color.
   */
  public void clearImage() {
    clearImage(0 /* red */, 0 /* green */, 0 /* blue */, 0 /* alpha */);
  }

  /**
   * Post a task to clear the surface to a specific color.
   */
  public void clearImage(final float r, final float g, final float b, final float a) {
    synchronized (handlerLock) {
      if (renderThreadHandler == null) {
        return;
      }
      renderThreadHandler.postAtFrontOfQueue(() -> clearSurfaceOnRenderThread(r, g, b, a));
    }
  }

  /**
   * Renders and releases |pendingFrame|.
   */
  private void renderFrameOnRenderThread() {
    // Fetch and render |pendingFrame|.
    final VideoFrame frame;
    synchronized (frameLock) {
      if (pendingFrame == null) {
        return;
      }
      frame = pendingFrame;
      pendingFrame = null;
    }
    if (eglBase == null || !eglBase.hasSurface()) {
      logD("Dropping frame - No surface");
      frame.release();
      return;
    }
    // Check if fps reduction is active.
    final boolean shouldRenderFrame;
    synchronized (fpsReductionLock) {
      if (minRenderPeriodNs == Long.MAX_VALUE) {
        // Rendering is paused.
        shouldRenderFrame = false;
      } else if (minRenderPeriodNs <= 0) {
        // FPS reduction is disabled.
        shouldRenderFrame = true;
      } else {
        final long currentTimeNs = System.nanoTime();
        if (currentTimeNs < nextFrameTimeNs) {
          logD("Skipping frame rendering - fps reduction is active.");
          shouldRenderFrame = false;
        } else {
          nextFrameTimeNs += minRenderPeriodNs;
          // The time for the next frame should always be in the future.
          nextFrameTimeNs = Math.max(nextFrameTimeNs, currentTimeNs);
          shouldRenderFrame = true;
        }
      }
    }

    final long startTimeNs = System.nanoTime();

    final float frameAspectRatio = frame.getRotatedWidth() / (float) frame.getRotatedHeight();
    final float drawnAspectRatio;
    synchronized (layoutLock) {
      drawnAspectRatio = layoutAspectRatio != 0f ? layoutAspectRatio : frameAspectRatio;
    }

    final float scaleX;
    final float scaleY;

    if (frameAspectRatio > drawnAspectRatio) {
      scaleX = drawnAspectRatio / frameAspectRatio;
      scaleY = 1f;
    } else {
      scaleX = 1f;
      scaleY = frameAspectRatio / drawnAspectRatio;
    }

    drawMatrix.reset();
    drawMatrix.preTranslate(0.5f, 0.5f);
    if (mirror)
      drawMatrix.preScale(-1f, 1f);
    drawMatrix.preScale(scaleX, scaleY);
    drawMatrix.preTranslate(-0.5f, -0.5f);

    if (shouldRenderFrame) {
      GLES20.glClearColor(0 /* red */, 0 /* green */, 0 /* blue */, 0 /* alpha */);
      GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT);
      frameDrawer.drawFrame(frame, drawer, drawMatrix, 0 /* viewportX */, 0 /* viewportY */,
          eglBase.surfaceWidth(), eglBase.surfaceHeight());

      final long swapBuffersStartTimeNs = System.nanoTime();
      eglBase.swapBuffers();

      final long currentTimeNs = System.nanoTime();
      synchronized (statisticsLock) {
        ++framesRendered;
        renderTimeNs += (currentTimeNs - startTimeNs);
        renderSwapBufferTimeNs += (currentTimeNs - swapBuffersStartTimeNs);
      }
    }

    notifyCallbacks(frame, shouldRenderFrame);
    frame.release();
  }

  private void notifyCallbacks(VideoFrame frame, boolean wasRendered) {
    if (frameListeners.isEmpty())
      return;

    drawMatrix.reset();
    drawMatrix.preTranslate(0.5f, 0.5f);
    if (mirror)
      drawMatrix.preScale(-1f, 1f);
    drawMatrix.preScale(1f, -1f); // We want the output to be upside down for Bitmap.
    drawMatrix.preTranslate(-0.5f, -0.5f);

    Iterator<FrameListenerAndParams> it = frameListeners.iterator();
    while (it.hasNext()) {
      FrameListenerAndParams listenerAndParams = it.next();
      if (!wasRendered && listenerAndParams.applyFpsReduction) {
        continue;
      }
      it.remove();

      final int scaledWidth = (int) (listenerAndParams.scale * frame.getRotatedWidth());
      final int scaledHeight = (int) (listenerAndParams.scale * frame.getRotatedHeight());

      if (scaledWidth == 0 || scaledHeight == 0) {
        listenerAndParams.listener.onFrame(null);
        continue;
      }

      if (bitmapTextureFramebuffer == null) {
        bitmapTextureFramebuffer = new GlTextureFrameBuffer(GLES20.GL_RGBA);
      }
      bitmapTextureFramebuffer.setSize(scaledWidth, scaledHeight);

      GLES20.glBindFramebuffer(GLES20.GL_FRAMEBUFFER, bitmapTextureFramebuffer.getFrameBufferId());
      GLES20.glFramebufferTexture2D(GLES20.GL_FRAMEBUFFER, GLES20.GL_COLOR_ATTACHMENT0,
          GLES20.GL_TEXTURE_2D, bitmapTextureFramebuffer.getTextureId(), 0);

      GLES20.glClearColor(0 /* red */, 0 /* green */, 0 /* blue */, 0 /* alpha */);
      GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT);
      frameDrawer.drawFrame(frame, listenerAndParams.drawer, drawMatrix, 0 /* viewportX */,
          0 /* viewportY */, scaledWidth, scaledHeight);

      final ByteBuffer bitmapBuffer = ByteBuffer.allocateDirect(scaledWidth * scaledHeight * 4);
      GLES20.glViewport(0, 0, scaledWidth, scaledHeight);
      GLES20.glReadPixels(
          0, 0, scaledWidth, scaledHeight, GLES20.GL_RGBA, GLES20.GL_UNSIGNED_BYTE, bitmapBuffer);

      GLES20.glBindFramebuffer(GLES20.GL_FRAMEBUFFER, 0);
      GlUtil.checkNoGLES2Error("EglRenderer.notifyCallbacks");

      final Bitmap bitmap = Bitmap.createBitmap(scaledWidth, scaledHeight, Bitmap.Config.ARGB_8888);
      bitmap.copyPixelsFromBuffer(bitmapBuffer);
      listenerAndParams.listener.onFrame(bitmap);
    }
  }

  private String averageTimeAsString(long sumTimeNs, int count) {
    return (count <= 0) ? "NA" : TimeUnit.NANOSECONDS.toMicros(sumTimeNs / count) + " μs";
  }

  private void logStatistics() {
    final long currentTimeNs = System.nanoTime();
    synchronized (statisticsLock) {
      final long elapsedTimeNs = currentTimeNs - statisticsStartTimeNs;
      if (elapsedTimeNs <= 0) {
        return;
      }
      final float renderFps = framesRendered * TimeUnit.SECONDS.toNanos(1) / (float) elapsedTimeNs;
      logD("Duration: " + TimeUnit.NANOSECONDS.toMillis(elapsedTimeNs) + " ms."
          + " Frames received: " + framesReceived + "."
          + " Dropped: " + framesDropped + "."
          + " Rendered: " + framesRendered + "."
          + " Render fps: " + String.format(Locale.US, "%.1f", renderFps) + "."
          + " Average render time: " + averageTimeAsString(renderTimeNs, framesRendered) + "."
          + " Average swapBuffer time: "
          + averageTimeAsString(renderSwapBufferTimeNs, framesRendered) + ".");
      resetStatistics(currentTimeNs);
    }
  }

  private void logD(String string) {
    Logging.d(TAG, name + string);
  }
}