Hold video frame in Bitmap instead of keeping a ByteBuffer reference.

remoting/android/java/src/org/chromium/chromoting/jni/JniInterface.java

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package org.chromium.chromoting.jni;
 
 import android.app.Activity;
 import android.app.AlertDialog;
 import android.app.ProgressDialog;
 import android.content.Context;
@@ skipping 118 matching lines @@
 
     /** Returns the current cursor shape. */
     public static Bitmap getCursorBitmap() { return sCursorBitmap; }
 
     /*
      * Entry points *from* the native code.
      */
     /** Callback to signal whenever we need to redraw. */
     private static Runnable sRedrawCallback = null;
 
-    /** Screen width of the video feed. */
-    private static int sWidth = 0;
-
-    /** Screen height of the video feed. */
-    private static int sHeight = 0;
-
-    /** Buffer holding the video feed. */
-    private static ByteBuffer sBuffer = null;
+    /** Bitmap holding a copy of the latest video frame. */
+    private static Bitmap sFrameBitmap = null;
 
     /** Position of cursor hot-spot. */
     private static Point sCursorHotspot = new Point();
 
     /** Bitmap holding the cursor shape. */
     private static Bitmap sCursorBitmap = null;
 
     /** Reports whenever the connection status changes. */
     private static void reportConnectionStatus(int state, int error) {
         if (state < SUCCESSFUL_CONNECTION && error == 0) {
@@ skipping 134 matching lines @@
         return true;
     }
 
     /** Performs the redrawing callback. This is a no-op if the window isn't visible. */
     private static void redrawGraphicsInternal() {
         if (sRedrawCallback != null)
             sRedrawCallback.run();
     }
 
     /**
-     * Obtains the image buffer.
-     * This should not be called from the UI thread. (We prefer the native graphics thread.)
+     * Returns a bitmap of the latest video frame. Called on the native graphics thread when
+     * DesktopView is repainted.
      */
-    public static Bitmap retrieveVideoFrame() {
+    public static Bitmap getVideoFrame() {
         if (Looper.myLooper() == Looper.getMainLooper()) {
             Log.w("jniiface", "Canvas being redrawn on UI thread");
         }
 
         if (!sConnected) {
             return null;
         }
 
-        int[] frame = new int[sWidth * sHeight];
-
-        sBuffer.order(ByteOrder.LITTLE_ENDIAN);
-        sBuffer.asIntBuffer().get(frame, 0, frame.length);
-
-        return Bitmap.createBitmap(frame, 0, sWidth, sWidth, sHeight, Bitmap.Config.ARGB_8888);
+        return sFrameBitmap;
     }
 
     /**
+     * Sets a new video frame. Called from native code on the native graphics thread whenever a new
+     * frame has been decoded.
+     */
+    private static void setVideoFrame(int width, int height, ByteBuffer buffer) {
+        int[] frame = new int[width * height];

[garykac, 2013/09/23 19:47:43]

Can you add a check here to ensure that this is being called on the graphics
thread?

[Lambros, 2013/09/25 23:15:11]

Done.

+
+        buffer.order(ByteOrder.LITTLE_ENDIAN);
+        buffer.asIntBuffer().get(frame, 0, frame.length);

[Sergey Ulanov, 2013/09/25 23:32:08]

This copies content of the buffer. I think we can avoid doing it. You just need
a custom webrtc::DesktopFrame implementation that stores data in an int array in
java heap and then allows releasing it to pass to this function.

[solb, 2013/09/26 14:21:36]

If I understand the patches correctly, https://codereview.chromium.org/23677011/
will be applied on top of this, and it eliminates this copy.

[Lambros, 2013/09/26 22:29:37]

Yes - with these two CLs landed, there will only be a single copy from C++ video
frame pixels to a Java Bitmap. Unless Java Bitmap can provide direct access to
its pixels to C++ code, or Android can draw pixels directly from a ByteBuffer
(or byte[] array) onto the screen, we cannot avoid this copy.

+
+        sFrameBitmap = Bitmap.createBitmap(frame, width, height, Bitmap.Config.ARGB_8888);
+        redrawGraphicsInternal();
+    }
+
+    /**
      * Updates the cursor shape. This is called from native code on the graphics thread when
      * receiving a new cursor shape from the host.
      */
     public static void updateCursorShape(int width, int height, int hotspotX, int hotspotY,
                                          ByteBuffer buffer) {
         sCursorHotspot = new Point(hotspotX, hotspotY);
 
         int[] data = new int[width * height];
         buffer.order(ByteOrder.LITTLE_ENDIAN);
         buffer.asIntBuffer().get(data, 0, data.length);
@@ skipping 23 matching lines @@
 
     /** Schedules a redraw on the native graphics thread. */
     private static native void scheduleRedrawNative();
 
     /** Passes mouse information to the native handling code. */
     private static native void mouseActionNative(int x, int y, int whichButton, boolean buttonDown);
 
     /** Passes key press information to the native handling code. */
     private static native void keyboardActionNative(int keyCode, boolean keyDown);
 }