Add a field trial to produce VideoFrames in camera capturers.

webrtc/sdk/android/src/java/org/webrtc/NV21Buffer.java

+/*
+ * Copyright 2017 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 java.nio.ByteBuffer;
+
+public class NV21Buffer implements VideoFrame.Buffer {

[magjed_webrtc, 2017/08/22 08:53:08]

Maybe you want to land this class in a separate CL?

[sakal, 2017/08/22 11:45:30]

Acknowledged but let's land this with the other code since this will only be
used from here.

+  private final byte[] data;
+  private final int width;
+  private final int height;
+  private final Runnable releaseCallback;
+  private final Object refCountLock = new Object();
+
+  private int refCount = 1;
+
+  public NV21Buffer(byte[] data, int width, int height, Runnable releaseCallback) {
+    this.data = data;
+    this.width = width;
+    this.height = height;
+    this.releaseCallback = releaseCallback;
+  }
+
+  @Override
+  public int getWidth() {
+    return width;
+  }
+
+  @Override
+  public int getHeight() {
+    return height;
+  }
+
+  @Override
+  public VideoFrame.I420Buffer toI420() {
+    return (VideoFrame.I420Buffer) cropAndScale(0, 0, width, height, width, height);

[magjed_webrtc, 2017/08/22 08:53:08]

Comment the literals.

[sakal, 2017/08/22 11:45:30]

Done.

+  }
+
+  @Override
+  public void retain() {
+    synchronized (refCountLock) {
+      ++refCount;
+    }
+  }
+
+  @Override
+  public void release() {
+    synchronized (refCountLock) {
+      if (--refCount == 0 && releaseCallback != null) {
+        releaseCallback.run();
+      }
+    }
+  }
+
+  @Override
+  public VideoFrame.Buffer cropAndScale(
+      int cropX, int cropY, int cropWidth, int cropHeight, int scaleWidth, int scaleHeight) {
+    I420BufferImpl newBuffer = I420BufferImpl.allocate(scaleWidth, scaleHeight);
+    nativeCropAndScale(cropX, cropY, cropWidth, cropHeight, scaleWidth, scaleHeight, data, width,
+        height, newBuffer.getDataY(), newBuffer.getStrideY(), newBuffer.getDataU(),
+        newBuffer.getStrideU(), newBuffer.getDataV(), newBuffer.getStrideV());
+    return newBuffer;
+  }
+
+  private static native void nativeCropAndScale(int cropX, int cropY, int cropWidth, int cropHeight,
+      int scaleWidth, int scaleHeight, byte[] src, int srcWidth, int srcHeight, ByteBuffer dstY,
+      int dstStrideY, ByteBuffer dstU, int dstStrideU, ByteBuffer dstV, int dstStrideV);
+}