webrtc/api/android/java/src/org/webrtc/ScreenCapturerAndroid.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.annotation.TargetApi;
import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.hardware.display.DisplayManager;
import android.hardware.display.VirtualDisplay;
import android.media.projection.MediaProjection;
import android.media.projection.MediaProjectionManager;
import android.view.Surface;

import java.util.ArrayList;
import java.util.List;

/**
 * An implementation of VideoCapturer to capture the screen content as a video stream.
 * Capturing is done by {@code MediaProjection} on a {@code SurfaceTexture}. We interact with this
 * {@code SurfaceTexture} using a {@code SurfaceTextureHelper}.
 * The {@code SurfaceTextureHelper} is created by the native code and passed to this capturer in
 * {@code VideoCapturer.initialize()}. On receiving a new frame, this capturer passes it
 * as a texture to the native code via {@code CapturerObserver.onTextureFrameCaptured()}. This takes
 * place on the HandlerThread of the given {@code SurfaceTextureHelper}. When done with each frame,
 * the native code returns the buffer to the  {@code SurfaceTextureHelper} to be used for new
 * frames. At any time, at most one frame is being processed.
 */
@TargetApi(21)
public class ScreenCapturerAndroid implements
    VideoCapturer, SurfaceTextureHelper.OnTextureFrameAvailableListener {

  private static final int DISPLAY_FLAGS = DisplayManager.VIRTUAL_DISPLAY_FLAG_PUBLIC
      | DisplayManager.VIRTUAL_DISPLAY_FLAG_PRESENTATION;
  // DPI for VirtualDisplay, does not seem to matter for us.
  private static final int VIRTUAL_DISPLAY_DPI = 400;

  private final Intent mediaProjectionPermissionResultData;
  private final MediaProjection.Callback mediaProjectionCallback;

  private int width;
  private int height;
  private VirtualDisplay virtualDisplay;
  private SurfaceTextureHelper surfaceTextureHelper;
  private CapturerObserver capturerObserver;
  private long numCapturedFrames = 0;
  private MediaProjection mediaProjection;
  private boolean isDisposed = false;
  private MediaProjectionManager mediaProjectionManager;

  /**
   * Constructs a new Screen Capturer.
   *
   * @param mediaProjectionPermissionResultData the result data of MediaProjection permission
   *     activity; the calling app must validate that result code is Activity.RESULT_OK before
   *     calling this method.
   * @param mediaProjectionCallback MediaProjection callback to implement application specific
   *     logic in events such as when the user revokes a previously granted capture permission.
  **/
  public ScreenCapturerAndroid(
      Intent mediaProjectionPermissionResultData,
      MediaProjection.Callback mediaProjectionCallback) {
    this.mediaProjectionPermissionResultData = mediaProjectionPermissionResultData;
    this.mediaProjectionCallback = mediaProjectionCallback;
  }

  private void checkNotDisposed() {
    if (isDisposed) {
      throw new RuntimeException("capturer is disposed.");
    }
  }

  @Override
  public synchronized void initialize(
      final SurfaceTextureHelper surfaceTextureHelper,
      final Context applicationContext,
      final VideoCapturer.CapturerObserver capturerObserver) {
    checkNotDisposed();

    if (capturerObserver == null) {
      throw new RuntimeException("capturerObserver not set.");
    }
    this.capturerObserver = capturerObserver;

    if (surfaceTextureHelper == null) {
      throw new RuntimeException("surfaceTextureHelper not set.");
    }
    this.surfaceTextureHelper = surfaceTextureHelper;

    mediaProjectionManager = (MediaProjectionManager)
        applicationContext.getSystemService(Context.MEDIA_PROJECTION_SERVICE);
  }

  /**
   * This method is not called by native code, neither by the java app. It can be removed later
   * once it is removed from the VideoCapturer interface.
   */
  @Override
  public List<CameraEnumerationAndroid.CaptureFormat> getSupportedFormats() {
    return null;
  }

  @Override
  public synchronized void startCapture(final int width, final int height,
       final int ignoredFramerate) {
    checkNotDisposed();

    this.width = width;
    this.height = height;

    mediaProjection = mediaProjectionManager.getMediaProjection(
        Activity.RESULT_OK, mediaProjectionPermissionResultData);

    // Let MediaProjection callback use the SurfaceTextureHelper thread.
    mediaProjection.registerCallback(mediaProjectionCallback, surfaceTextureHelper.getHandler());

    createVirtualDisplay();
    capturerObserver.onCapturerStarted(true);
    surfaceTextureHelper.startListening(ScreenCapturerAndroid.this);
  }

  @Override
  public synchronized void stopCapture() {
    checkNotDisposed();
    ThreadUtils.invokeAtFrontUninterruptibly(surfaceTextureHelper.getHandler(), new Runnable() {
      @Override
      public void run() {
        surfaceTextureHelper.stopListening();
        capturerObserver.onCapturerStopped();

        if (virtualDisplay != null) {
          virtualDisplay.release();
          virtualDisplay = null;
        }

        if (mediaProjection != null) {
          // Unregister the callback before stopping, otherwise the callback recursively
          // calls this method.
          mediaProjection.unregisterCallback(mediaProjectionCallback);
          mediaProjection.stop();
          mediaProjection = null;
        }
      }
    });
  }


  @Override
  public synchronized void dispose() {
    isDisposed = true;
  }

  @Override
  public synchronized void onOutputFormatRequest(
      final int width, final int height, final int framerate) {
    checkNotDisposed();
    surfaceTextureHelper.getHandler().post(new Runnable() {
      @Override
      public void run() {
        capturerObserver.onOutputFormatRequest(width, height, framerate);
      }
    });
  }

  /**
   * Changes output video format. This method can be used to scale the output
   * video, or to change orientation when the captured screen is rotated for example.
   *
   * @param width new output video width
   * @param height new output video height
   * @param ignoredFramerate ignored
   */
  @Override
  public synchronized void changeCaptureFormat(
      final int width, final int height, final int ignoredFramerate) {
    checkNotDisposed();

    this.width = width;
    this.height = height;

    if (virtualDisplay == null) {
      // Capturer is stopped, the virtual display will be created in startCaptuer().
      return;
    }

    // Create a new virtual display on the surfaceTextureHelper thread to avoid interference
    // with frame processing, which happens on the same thread (we serialize events by running
    // them on the same thread).
    ThreadUtils.invokeAtFrontUninterruptibly(surfaceTextureHelper.getHandler(), new Runnable() {
      @Override
      public void run() {
        virtualDisplay.release();
        createVirtualDisplay();
      }
    });
  }

  private void createVirtualDisplay() {
    surfaceTextureHelper.getSurfaceTexture().setDefaultBufferSize(width, height);
    virtualDisplay = mediaProjection.createVirtualDisplay(
        "WebRTC_ScreenCapture", width, height, VIRTUAL_DISPLAY_DPI,
        DISPLAY_FLAGS, new Surface(surfaceTextureHelper.getSurfaceTexture()),
        null /* callback */, null /* callback handler */);
  }

  // This is called on the internal looper thread of {@Code SurfaceTextureHelper}.
  @Override
  public void onTextureFrameAvailable(int oesTextureId, float[] transformMatrix, long timestampNs) {
    numCapturedFrames++;
    capturerObserver.onTextureFrameCaptured(width, height, oesTextureId, transformMatrix,
        0 /* rotation */, timestampNs);
  }

  @Override
  public boolean isScreencast() {
    return true;
  }

  public long getNumCapturedFrames() {
    return numCapturedFrames;
  }
}