webrtc/api/android/java/src/org/webrtc/SurfaceTextureHelper.java - src - Git at Google

 /*
  *  Copyright 2015 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.SurfaceTexture;
 import android.opengl.GLES11Ext;
 import android.opengl.GLES20;
 import android.os.Build;
 import android.os.Handler;
 import android.os.HandlerThread;
 import android.os.SystemClock;

 import java.nio.ByteBuffer;
 import java.nio.FloatBuffer;
 import java.util.concurrent.Callable;
 import java.util.concurrent.TimeUnit;

 /**
  * Helper class to create and synchronize access to a SurfaceTexture. The caller will get notified
  * of new frames in onTextureFrameAvailable(), and should call returnTextureFrame() when done with
  * the frame. Only one texture frame can be in flight at once, so returnTextureFrame() must be
  * called in order to receive a new frame. Call stopListening() to stop receiveing new frames. Call
  * dispose to release all resources once the texture frame is returned.
  * Note that there is a C++ counter part of this class that optionally can be used. It is used for
  * wrapping texture frames into webrtc::VideoFrames and also handles calling returnTextureFrame()
  * when the webrtc::VideoFrame is no longer used.
  */
 class SurfaceTextureHelper {
   private static final String TAG = "SurfaceTextureHelper";
   /**
    * Callback interface for being notified that a new texture frame is available. The calls will be
    * made on a dedicated thread with a bound EGLContext. The thread will be the same throughout the
    * lifetime of the SurfaceTextureHelper instance, but different from the thread calling the
    * SurfaceTextureHelper constructor. The callee is not allowed to make another EGLContext current
    * on the calling thread.
    */
   public interface OnTextureFrameAvailableListener {
     abstract void onTextureFrameAvailable(
         int oesTextureId, float[] transformMatrix, long timestampNs);
   }

   /**
    * Construct a new SurfaceTextureHelper sharing OpenGL resources with |sharedContext|. A dedicated
    * thread and handler is created for handling the SurfaceTexture. May return null if EGL fails to
    * initialize a pixel buffer surface and make it current.
    */
   public static SurfaceTextureHelper create(
       final String threadName, final EglBase.Context sharedContext) {
     final HandlerThread thread = new HandlerThread(threadName);
     thread.start();
     final Handler handler = new Handler(thread.getLooper());

     // The onFrameAvailable() callback will be executed on the SurfaceTexture ctor thread. See:
     // http://grepcode.com/file/repository.grepcode.com/java/ext/com.google.android/android/5.1.1_r1/android/graphics/SurfaceTexture.java#195.
     // Therefore, in order to control the callback thread on API lvl < 21, the SurfaceTextureHelper
     // is constructed on the |handler| thread.
     return ThreadUtils.invokeAtFrontUninterruptibly(handler, new Callable<SurfaceTextureHelper>() {
       @Override
       public SurfaceTextureHelper call() {
         try {
           return new SurfaceTextureHelper(sharedContext, handler);
         } catch (RuntimeException e) {
           Logging.e(TAG, threadName + " create failure", e);
           return null;
         }
       }
     });
   }

   // State for YUV conversion, instantiated on demand.
   static private class YuvConverter {
     private final EglBase eglBase;
     private final GlShader shader;
     private boolean released = false;

     // Vertex coordinates in Normalized Device Coordinates, i.e.
     // (-1, -1) is bottom-left and (1, 1) is top-right.
     private static final FloatBuffer DEVICE_RECTANGLE =
         GlUtil.createFloatBuffer(new float[] {
               -1.0f, -1.0f,  // Bottom left.
                1.0f, -1.0f,  // Bottom right.
               -1.0f,  1.0f,  // Top left.
                1.0f,  1.0f,  // Top right.
             });

     // Texture coordinates - (0, 0) is bottom-left and (1, 1) is top-right.
     private static final FloatBuffer TEXTURE_RECTANGLE =
         GlUtil.createFloatBuffer(new float[] {
               0.0f, 0.0f,  // Bottom left.
               1.0f, 0.0f,  // Bottom right.
               0.0f, 1.0f,  // Top left.
               1.0f, 1.0f   // Top right.
             });

     private static final String VERTEX_SHADER =
         "varying vec2 interp_tc;\n"
       + "attribute vec4 in_pos;\n"
       + "attribute vec4 in_tc;\n"
       + "\n"
       + "uniform mat4 texMatrix;\n"
       + "\n"
       + "void main() {\n"
       + "    gl_Position = in_pos;\n"
       + "    interp_tc = (texMatrix * in_tc).xy;\n"
       + "}\n";

     private static final String FRAGMENT_SHADER =
         "#extension GL_OES_EGL_image_external : require\n"
       + "precision mediump float;\n"
       + "varying vec2 interp_tc;\n"
       + "\n"
       + "uniform samplerExternalOES oesTex;\n"
       // Difference in texture coordinate corresponding to one
       // sub-pixel in the x direction.
       + "uniform vec2 xUnit;\n"
       // Color conversion coefficients, including constant term
       + "uniform vec4 coeffs;\n"
       + "\n"
       + "void main() {\n"
       // Since the alpha read from the texture is always 1, this could
       // be written as a mat4 x vec4 multiply. However, that seems to
       // give a worse framerate, possibly because the additional
       // multiplies by 1.0 consume resources. TODO(nisse): Could also
       // try to do it as a vec3 x mat3x4, followed by an add in of a
       // constant vector.
       + "  gl_FragColor.r = coeffs.a + dot(coeffs.rgb,\n"
       + "      texture2D(oesTex, interp_tc - 1.5 * xUnit).rgb);\n"
       + "  gl_FragColor.g = coeffs.a + dot(coeffs.rgb,\n"
       + "      texture2D(oesTex, interp_tc - 0.5 * xUnit).rgb);\n"
       + "  gl_FragColor.b = coeffs.a + dot(coeffs.rgb,\n"
       + "      texture2D(oesTex, interp_tc + 0.5 * xUnit).rgb);\n"
       + "  gl_FragColor.a = coeffs.a + dot(coeffs.rgb,\n"
       + "      texture2D(oesTex, interp_tc + 1.5 * xUnit).rgb);\n"
       + "}\n";

     private int texMatrixLoc;
     private int xUnitLoc;
     private int coeffsLoc;;

     YuvConverter (EglBase.Context sharedContext) {
       eglBase = EglBase.create(sharedContext, EglBase.CONFIG_PIXEL_RGBA_BUFFER);
       eglBase.createDummyPbufferSurface();
       eglBase.makeCurrent();

       shader = new GlShader(VERTEX_SHADER, FRAGMENT_SHADER);
       shader.useProgram();
       texMatrixLoc = shader.getUniformLocation("texMatrix");
       xUnitLoc = shader.getUniformLocation("xUnit");
       coeffsLoc = shader.getUniformLocation("coeffs");
       GLES20.glUniform1i(shader.getUniformLocation("oesTex"), 0);
       GlUtil.checkNoGLES2Error("Initialize fragment shader uniform values.");
       // Initialize vertex shader attributes.
       shader.setVertexAttribArray("in_pos", 2, DEVICE_RECTANGLE);
       // If the width is not a multiple of 4 pixels, the texture
       // will be scaled up slightly and clipped at the right border.
       shader.setVertexAttribArray("in_tc", 2, TEXTURE_RECTANGLE);
       eglBase.detachCurrent();
     }

     synchronized void convert(ByteBuffer buf,
         int width, int height, int stride, int textureId, float [] transformMatrix) {
       if (released) {
         throw new IllegalStateException(
             "YuvConverter.convert called on released object");
       }

       // We draw into a buffer laid out like
       //
       //    +---------+
       //    |         |
       //    |  Y      |
       //    |         |
       //    |         |
       //    +----+----+
       //    | U  | V  |
       //    |    |    |
       //    +----+----+
       //
       // In memory, we use the same stride for all of Y, U and V. The
       // U data starts at offset |height| * |stride| from the Y data,
       // and the V data starts at at offset |stride/2| from the U
       // data, with rows of U and V data alternating.
       //
       // Now, it would have made sense to allocate a pixel buffer with
       // a single byte per pixel (EGL10.EGL_COLOR_BUFFER_TYPE,
       // EGL10.EGL_LUMINANCE_BUFFER,), but that seems to be
       // unsupported by devices. So do the following hack: Allocate an
       // RGBA buffer, of width |stride|/4. To render each of these
       // large pixels, sample the texture at 4 different x coordinates
       // and store the results in the four components.
       //
       // Since the V data needs to start on a boundary of such a
       // larger pixel, it is not sufficient that |stride| is even, it
       // has to be a multiple of 8 pixels.

       if (stride % 8 != 0) {
         throw new IllegalArgumentException(
             "Invalid stride, must be a multiple of 8");
       }
       if (stride < width){
         throw new IllegalArgumentException(
             "Invalid stride, must >= width");
       }

       int y_width = (width+3) / 4;
       int uv_width = (width+7) / 8;
       int uv_height = (height+1)/2;
       int total_height = height + uv_height;
       int size = stride * total_height;

       if (buf.capacity() < size) {
         throw new IllegalArgumentException("YuvConverter.convert called with too small buffer");
       }
       // Produce a frame buffer starting at top-left corner, not
       // bottom-left.
       transformMatrix =
           RendererCommon.multiplyMatrices(transformMatrix,
               RendererCommon.verticalFlipMatrix());

       // Create new pBuffferSurface with the correct size if needed.
       if (eglBase.hasSurface()) {
         if (eglBase.surfaceWidth() != stride/4 ||
             eglBase.surfaceHeight() != total_height){
           eglBase.releaseSurface();
           eglBase.createPbufferSurface(stride/4, total_height);
         }
       } else {
         eglBase.createPbufferSurface(stride/4, total_height);
       }

       eglBase.makeCurrent();

       GLES20.glActiveTexture(GLES20.GL_TEXTURE0);
       GLES20.glBindTexture(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, textureId);
       GLES20.glUniformMatrix4fv(texMatrixLoc, 1, false, transformMatrix, 0);

       // Draw Y
       GLES20.glViewport(0, 0, y_width, height);
       // Matrix * (1;0;0;0) / width. Note that opengl uses column major order.
       GLES20.glUniform2f(xUnitLoc,
           transformMatrix[0] / width,
           transformMatrix[1] / width);
       // Y'UV444 to RGB888, see
       // https://en.wikipedia.org/wiki/YUV#Y.27UV444_to_RGB888_conversion.
       // We use the ITU-R coefficients for U and V */
       GLES20.glUniform4f(coeffsLoc, 0.299f, 0.587f, 0.114f, 0.0f);
       GLES20.glDrawArrays(GLES20.GL_TRIANGLE_STRIP, 0, 4);

       // Draw U
       GLES20.glViewport(0, height, uv_width, uv_height);
       // Matrix * (1;0;0;0) / (width / 2). Note that opengl uses column major order.
       GLES20.glUniform2f(xUnitLoc,
           2.0f * transformMatrix[0] / width,
           2.0f * transformMatrix[1] / width);
       GLES20.glUniform4f(coeffsLoc, -0.169f, -0.331f, 0.499f, 0.5f);
       GLES20.glDrawArrays(GLES20.GL_TRIANGLE_STRIP, 0, 4);

       // Draw V
       GLES20.glViewport(stride/8, height, uv_width, uv_height);
       GLES20.glUniform4f(coeffsLoc, 0.499f, -0.418f, -0.0813f, 0.5f);
       GLES20.glDrawArrays(GLES20.GL_TRIANGLE_STRIP, 0, 4);

       GLES20.glReadPixels(0, 0, stride/4, total_height, GLES20.GL_RGBA,
           GLES20.GL_UNSIGNED_BYTE, buf);

       GlUtil.checkNoGLES2Error("YuvConverter.convert");

       // Unbind texture. Reportedly needed on some devices to get
       // the texture updated from the camera.
       GLES20.glBindTexture(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, 0);
       eglBase.detachCurrent();
     }

     synchronized void release() {
       released = true;
       eglBase.makeCurrent();
       shader.release();
       eglBase.release();
     }
   }

   private final Handler handler;
   private final EglBase eglBase;
   private final SurfaceTexture surfaceTexture;
   private final int oesTextureId;
   private YuvConverter yuvConverter;

   // These variables are only accessed from the |handler| thread.
   private OnTextureFrameAvailableListener listener;
   // The possible states of this class.
   private boolean hasPendingTexture = false;
   private volatile boolean isTextureInUse = false;
   private boolean isQuitting = false;
   // |pendingListener| is set in setListener() and the runnable is posted to the handler thread.
   // setListener() is not allowed to be called again before stopListening(), so this is thread safe.
   private OnTextureFrameAvailableListener pendingListener;
   final Runnable setListenerRunnable = new Runnable() {
     @Override
     public void run() {
       Logging.d(TAG, "Setting listener to " + pendingListener);
       listener = pendingListener;
       pendingListener = null;
       // May have a pending frame from the previous capture session - drop it.
       if (hasPendingTexture) {
         // Calling updateTexImage() is neccessary in order to receive new frames.
         updateTexImage();
         hasPendingTexture = false;
       }
     }
   };

   private SurfaceTextureHelper(EglBase.Context sharedContext, Handler handler) {
     if (handler.getLooper().getThread() != Thread.currentThread()) {
       throw new IllegalStateException("SurfaceTextureHelper must be created on the handler thread");
     }
     this.handler = handler;

     eglBase = EglBase.create(sharedContext, EglBase.CONFIG_PIXEL_BUFFER);
     try {
       // Both these statements have been observed to fail on rare occasions, see BUG=webrtc:5682.
       eglBase.createDummyPbufferSurface();
       eglBase.makeCurrent();
     } catch (RuntimeException e) {
       // Clean up before rethrowing the exception.
       eglBase.release();
       handler.getLooper().quit();
       throw e;
     }

     oesTextureId = GlUtil.generateTexture(GLES11Ext.GL_TEXTURE_EXTERNAL_OES);
     surfaceTexture = new SurfaceTexture(oesTextureId);
     surfaceTexture.setOnFrameAvailableListener(new SurfaceTexture.OnFrameAvailableListener() {
       @Override
       public void onFrameAvailable(SurfaceTexture surfaceTexture) {
         hasPendingTexture = true;
         tryDeliverTextureFrame();
       }
     });
   }

   private YuvConverter getYuvConverter() {
     // yuvConverter is assigned once
     if (yuvConverter != null)
       return yuvConverter;

     synchronized(this) {
       if (yuvConverter == null)
         yuvConverter = new YuvConverter(eglBase.getEglBaseContext());
       return yuvConverter;
     }
   }

   /**
    * Start to stream textures to the given |listener|. If you need to change listener, you need to
    * call stopListening() first.
    */
   public void startListening(final OnTextureFrameAvailableListener listener) {
     if (this.listener != null || this.pendingListener != null) {
       throw new IllegalStateException("SurfaceTextureHelper listener has already been set.");
     }
     this.pendingListener = listener;
     handler.post(setListenerRunnable);
   }

   /**
    * Stop listening. The listener set in startListening() is guaranteded to not receive any more
    * onTextureFrameAvailable() callbacks after this function returns.
    */
   public void stopListening() {
     Logging.d(TAG, "stopListening()");
     handler.removeCallbacks(setListenerRunnable);
     ThreadUtils.invokeAtFrontUninterruptibly(handler, new Runnable() {
       @Override
       public void run() {
         listener = null;
         pendingListener = null;
       }
     });
   }

   /**
    * Retrieve the underlying SurfaceTexture. The SurfaceTexture should be passed in to a video
    * producer such as a camera or decoder.
    */
   public SurfaceTexture getSurfaceTexture() {
     return surfaceTexture;
   }

   /**
    * Retrieve the handler that calls onTextureFrameAvailable(). This handler is valid until
    * dispose() is called.
    */
   public Handler getHandler() {
     return handler;
   }

   /**
    * Call this function to signal that you are done with the frame received in
    * onTextureFrameAvailable(). Only one texture frame can be in flight at once, so you must call
    * this function in order to receive a new frame.
    */
   public void returnTextureFrame() {
     handler.post(new Runnable() {
       @Override public void run() {
         isTextureInUse = false;
         if (isQuitting) {
           release();
         } else {
           tryDeliverTextureFrame();
         }
       }
     });
   }

   public boolean isTextureInUse() {
     return isTextureInUse;
   }

   /**
    * Call disconnect() to stop receiving frames. OpenGL resources are released and the handler is
    * stopped when the texture frame has been returned by a call to returnTextureFrame(). You are
    * guaranteed to not receive any more onTextureFrameAvailable() after this function returns.
    */
   public void dispose() {
     Logging.d(TAG, "dispose()");
     ThreadUtils.invokeAtFrontUninterruptibly(handler, new Runnable() {
       @Override
       public void run() {
         isQuitting = true;
         if (!isTextureInUse) {
           release();
         }
       }
     });
   }

   public void textureToYUV(ByteBuffer buf,
       int width, int height, int stride, int textureId, float [] transformMatrix) {
     if (textureId != oesTextureId)
       throw new IllegalStateException("textureToByteBuffer called with unexpected textureId");

     getYuvConverter().convert(buf, width, height, stride, textureId, transformMatrix);
   }

   private void updateTexImage() {
     // SurfaceTexture.updateTexImage apparently can compete and deadlock with eglSwapBuffers,
     // as observed on Nexus 5. Therefore, synchronize it with the EGL functions.
     // See https://bugs.chromium.org/p/webrtc/issues/detail?id=5702 for more info.
     synchronized (EglBase.lock) {
       surfaceTexture.updateTexImage();
     }
   }

   private void tryDeliverTextureFrame() {
     if (handler.getLooper().getThread() != Thread.currentThread()) {
       throw new IllegalStateException("Wrong thread.");
     }
     if (isQuitting || !hasPendingTexture || isTextureInUse || listener == null) {
       return;
     }
     isTextureInUse = true;
     hasPendingTexture = false;

     updateTexImage();

     final float[] transformMatrix = new float[16];
     surfaceTexture.getTransformMatrix(transformMatrix);
     final long timestampNs = (Build.VERSION.SDK_INT >= Build.VERSION_CODES.ICE_CREAM_SANDWICH)
         ? surfaceTexture.getTimestamp()
         : TimeUnit.MILLISECONDS.toNanos(SystemClock.elapsedRealtime());
     listener.onTextureFrameAvailable(oesTextureId, transformMatrix, timestampNs);
   }

   private void release() {
     if (handler.getLooper().getThread() != Thread.currentThread()) {
       throw new IllegalStateException("Wrong thread.");
     }
     if (isTextureInUse || !isQuitting) {
       throw new IllegalStateException("Unexpected release.");
     }
     synchronized (this) {
       if (yuvConverter != null)
         yuvConverter.release();
     }
     GLES20.glDeleteTextures(1, new int[] {oesTextureId}, 0);
     surfaceTexture.release();
     eglBase.release();
     handler.getLooper().quit();
   }
 }
	/*
	* Copyright 2015 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.SurfaceTexture;
	import android.opengl.GLES11Ext;
	import android.opengl.GLES20;
	import android.os.Build;
	import android.os.Handler;
	import android.os.HandlerThread;
	import android.os.SystemClock;

	import java.nio.ByteBuffer;
	import java.nio.FloatBuffer;
	import java.util.concurrent.Callable;
	import java.util.concurrent.TimeUnit;

	/**
	* Helper class to create and synchronize access to a SurfaceTexture. The caller will get notified
	* of new frames in onTextureFrameAvailable(), and should call returnTextureFrame() when done with
	* the frame. Only one texture frame can be in flight at once, so returnTextureFrame() must be
	* called in order to receive a new frame. Call stopListening() to stop receiveing new frames. Call
	* dispose to release all resources once the texture frame is returned.
	* Note that there is a C++ counter part of this class that optionally can be used. It is used for
	* wrapping texture frames into webrtc::VideoFrames and also handles calling returnTextureFrame()
	* when the webrtc::VideoFrame is no longer used.
	*/
	class SurfaceTextureHelper {
	private static final String TAG = "SurfaceTextureHelper";
	/**
	* Callback interface for being notified that a new texture frame is available. The calls will be
	* made on a dedicated thread with a bound EGLContext. The thread will be the same throughout the
	* lifetime of the SurfaceTextureHelper instance, but different from the thread calling the
	* SurfaceTextureHelper constructor. The callee is not allowed to make another EGLContext current
	* on the calling thread.
	*/
	public interface OnTextureFrameAvailableListener {
	abstract void onTextureFrameAvailable(
	int oesTextureId, float[] transformMatrix, long timestampNs);
	}

	/**
	* Construct a new SurfaceTextureHelper sharing OpenGL resources with \|sharedContext\|. A dedicated
	* thread and handler is created for handling the SurfaceTexture. May return null if EGL fails to
	* initialize a pixel buffer surface and make it current.
	*/
	public static SurfaceTextureHelper create(
	final String threadName, final EglBase.Context sharedContext) {
	final HandlerThread thread = new HandlerThread(threadName);
	thread.start();
	final Handler handler = new Handler(thread.getLooper());

	// The onFrameAvailable() callback will be executed on the SurfaceTexture ctor thread. See:
	// http://grepcode.com/file/repository.grepcode.com/java/ext/com.google.android/android/5.1.1_r1/android/graphics/SurfaceTexture.java#195.
	// Therefore, in order to control the callback thread on API lvl < 21, the SurfaceTextureHelper
	// is constructed on the \|handler\| thread.
	return ThreadUtils.invokeAtFrontUninterruptibly(handler, new Callable<SurfaceTextureHelper>() {
	@Override
	public SurfaceTextureHelper call() {
	try {
	return new SurfaceTextureHelper(sharedContext, handler);
	} catch (RuntimeException e) {
	Logging.e(TAG, threadName + " create failure", e);
	return null;
	}
	}
	});
	}

	// State for YUV conversion, instantiated on demand.
	static private class YuvConverter {
	private final EglBase eglBase;
	private final GlShader shader;
	private boolean released = false;

	// Vertex coordinates in Normalized Device Coordinates, i.e.
	// (-1, -1) is bottom-left and (1, 1) is top-right.
	private static final FloatBuffer DEVICE_RECTANGLE =
	GlUtil.createFloatBuffer(new float[] {
	-1.0f, -1.0f, // Bottom left.
	1.0f, -1.0f, // Bottom right.
	-1.0f, 1.0f, // Top left.
	1.0f, 1.0f, // Top right.
	});

	// Texture coordinates - (0, 0) is bottom-left and (1, 1) is top-right.
	private static final FloatBuffer TEXTURE_RECTANGLE =
	GlUtil.createFloatBuffer(new float[] {
	0.0f, 0.0f, // Bottom left.
	1.0f, 0.0f, // Bottom right.
	0.0f, 1.0f, // Top left.
	1.0f, 1.0f // Top right.
	});

	private static final String VERTEX_SHADER =
	"varying vec2 interp_tc;\n"
	+ "attribute vec4 in_pos;\n"
	+ "attribute vec4 in_tc;\n"
	+ "\n"
	+ "uniform mat4 texMatrix;\n"
	+ "\n"
	+ "void main() {\n"
	+ " gl_Position = in_pos;\n"
	+ " interp_tc = (texMatrix * in_tc).xy;\n"
	+ "}\n";

	private static final String FRAGMENT_SHADER =
	"#extension GL_OES_EGL_image_external : require\n"
	+ "precision mediump float;\n"
	+ "varying vec2 interp_tc;\n"
	+ "\n"
	+ "uniform samplerExternalOES oesTex;\n"
	// Difference in texture coordinate corresponding to one
	// sub-pixel in the x direction.
	+ "uniform vec2 xUnit;\n"
	// Color conversion coefficients, including constant term
	+ "uniform vec4 coeffs;\n"
	+ "\n"
	+ "void main() {\n"
	// Since the alpha read from the texture is always 1, this could
	// be written as a mat4 x vec4 multiply. However, that seems to
	// give a worse framerate, possibly because the additional
	// multiplies by 1.0 consume resources. TODO(nisse): Could also
	// try to do it as a vec3 x mat3x4, followed by an add in of a
	// constant vector.
	+ " gl_FragColor.r = coeffs.a + dot(coeffs.rgb,\n"
	+ " texture2D(oesTex, interp_tc - 1.5 * xUnit).rgb);\n"
	+ " gl_FragColor.g = coeffs.a + dot(coeffs.rgb,\n"
	+ " texture2D(oesTex, interp_tc - 0.5 * xUnit).rgb);\n"
	+ " gl_FragColor.b = coeffs.a + dot(coeffs.rgb,\n"
	+ " texture2D(oesTex, interp_tc + 0.5 * xUnit).rgb);\n"
	+ " gl_FragColor.a = coeffs.a + dot(coeffs.rgb,\n"
	+ " texture2D(oesTex, interp_tc + 1.5 * xUnit).rgb);\n"
	+ "}\n";

	private int texMatrixLoc;
	private int xUnitLoc;
	private int coeffsLoc;;

	YuvConverter (EglBase.Context sharedContext) {
	eglBase = EglBase.create(sharedContext, EglBase.CONFIG_PIXEL_RGBA_BUFFER);
	eglBase.createDummyPbufferSurface();
	eglBase.makeCurrent();

	shader = new GlShader(VERTEX_SHADER, FRAGMENT_SHADER);
	shader.useProgram();
	texMatrixLoc = shader.getUniformLocation("texMatrix");
	xUnitLoc = shader.getUniformLocation("xUnit");
	coeffsLoc = shader.getUniformLocation("coeffs");
	GLES20.glUniform1i(shader.getUniformLocation("oesTex"), 0);
	GlUtil.checkNoGLES2Error("Initialize fragment shader uniform values.");
	// Initialize vertex shader attributes.
	shader.setVertexAttribArray("in_pos", 2, DEVICE_RECTANGLE);
	// If the width is not a multiple of 4 pixels, the texture
	// will be scaled up slightly and clipped at the right border.
	shader.setVertexAttribArray("in_tc", 2, TEXTURE_RECTANGLE);
	eglBase.detachCurrent();
	}

	synchronized void convert(ByteBuffer buf,
	int width, int height, int stride, int textureId, float [] transformMatrix) {
	if (released) {
	throw new IllegalStateException(
	"YuvConverter.convert called on released object");
	}

	// We draw into a buffer laid out like
	//
	// +---------+
	// \| \|
	// \| Y \|
	// \| \|
	// \| \|
	// +----+----+
	// \| U \| V \|
	// \| \| \|
	// +----+----+
	//
	// In memory, we use the same stride for all of Y, U and V. The
	// U data starts at offset \|height\| * \|stride\| from the Y data,
	// and the V data starts at at offset \|stride/2\| from the U
	// data, with rows of U and V data alternating.
	//
	// Now, it would have made sense to allocate a pixel buffer with
	// a single byte per pixel (EGL10.EGL_COLOR_BUFFER_TYPE,
	// EGL10.EGL_LUMINANCE_BUFFER,), but that seems to be
	// unsupported by devices. So do the following hack: Allocate an
	// RGBA buffer, of width \|stride\|/4. To render each of these
	// large pixels, sample the texture at 4 different x coordinates
	// and store the results in the four components.
	//
	// Since the V data needs to start on a boundary of such a
	// larger pixel, it is not sufficient that \|stride\| is even, it
	// has to be a multiple of 8 pixels.

	if (stride % 8 != 0) {
	throw new IllegalArgumentException(
	"Invalid stride, must be a multiple of 8");
	}
	if (stride < width){
	throw new IllegalArgumentException(
	"Invalid stride, must >= width");
	}

	int y_width = (width+3) / 4;
	int uv_width = (width+7) / 8;
	int uv_height = (height+1)/2;
	int total_height = height + uv_height;
	int size = stride * total_height;

	if (buf.capacity() < size) {
	throw new IllegalArgumentException("YuvConverter.convert called with too small buffer");
	}
	// Produce a frame buffer starting at top-left corner, not
	// bottom-left.
	transformMatrix =
	RendererCommon.multiplyMatrices(transformMatrix,
	RendererCommon.verticalFlipMatrix());

	// Create new pBuffferSurface with the correct size if needed.
	if (eglBase.hasSurface()) {
	if (eglBase.surfaceWidth() != stride/4 \|\|
	eglBase.surfaceHeight() != total_height){
	eglBase.releaseSurface();
	eglBase.createPbufferSurface(stride/4, total_height);
	}
	} else {
	eglBase.createPbufferSurface(stride/4, total_height);
	}

	eglBase.makeCurrent();

	GLES20.glActiveTexture(GLES20.GL_TEXTURE0);
	GLES20.glBindTexture(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, textureId);
	GLES20.glUniformMatrix4fv(texMatrixLoc, 1, false, transformMatrix, 0);

	// Draw Y
	GLES20.glViewport(0, 0, y_width, height);
	// Matrix * (1;0;0;0) / width. Note that opengl uses column major order.
	GLES20.glUniform2f(xUnitLoc,
	transformMatrix[0] / width,
	transformMatrix[1] / width);
	// Y'UV444 to RGB888, see
	// https://en.wikipedia.org/wiki/YUV#Y.27UV444_to_RGB888_conversion.
	// We use the ITU-R coefficients for U and V */
	GLES20.glUniform4f(coeffsLoc, 0.299f, 0.587f, 0.114f, 0.0f);
	GLES20.glDrawArrays(GLES20.GL_TRIANGLE_STRIP, 0, 4);

	// Draw U
	GLES20.glViewport(0, height, uv_width, uv_height);
	// Matrix * (1;0;0;0) / (width / 2). Note that opengl uses column major order.
	GLES20.glUniform2f(xUnitLoc,
	2.0f * transformMatrix[0] / width,
	2.0f * transformMatrix[1] / width);
	GLES20.glUniform4f(coeffsLoc, -0.169f, -0.331f, 0.499f, 0.5f);
	GLES20.glDrawArrays(GLES20.GL_TRIANGLE_STRIP, 0, 4);

	// Draw V
	GLES20.glViewport(stride/8, height, uv_width, uv_height);
	GLES20.glUniform4f(coeffsLoc, 0.499f, -0.418f, -0.0813f, 0.5f);
	GLES20.glDrawArrays(GLES20.GL_TRIANGLE_STRIP, 0, 4);

	GLES20.glReadPixels(0, 0, stride/4, total_height, GLES20.GL_RGBA,
	GLES20.GL_UNSIGNED_BYTE, buf);

	GlUtil.checkNoGLES2Error("YuvConverter.convert");

	// Unbind texture. Reportedly needed on some devices to get
	// the texture updated from the camera.
	GLES20.glBindTexture(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, 0);
	eglBase.detachCurrent();
	}

	synchronized void release() {
	released = true;
	eglBase.makeCurrent();
	shader.release();
	eglBase.release();
	}
	}

	private final Handler handler;
	private final EglBase eglBase;
	private final SurfaceTexture surfaceTexture;
	private final int oesTextureId;
	private YuvConverter yuvConverter;

	// These variables are only accessed from the \|handler\| thread.
	private OnTextureFrameAvailableListener listener;
	// The possible states of this class.
	private boolean hasPendingTexture = false;
	private volatile boolean isTextureInUse = false;
	private boolean isQuitting = false;
	// \|pendingListener\| is set in setListener() and the runnable is posted to the handler thread.
	// setListener() is not allowed to be called again before stopListening(), so this is thread safe.
	private OnTextureFrameAvailableListener pendingListener;
	final Runnable setListenerRunnable = new Runnable() {
	@Override
	public void run() {
	Logging.d(TAG, "Setting listener to " + pendingListener);
	listener = pendingListener;
	pendingListener = null;
	// May have a pending frame from the previous capture session - drop it.
	if (hasPendingTexture) {
	// Calling updateTexImage() is neccessary in order to receive new frames.
	updateTexImage();
	hasPendingTexture = false;
	}
	}
	};

	private SurfaceTextureHelper(EglBase.Context sharedContext, Handler handler) {
	if (handler.getLooper().getThread() != Thread.currentThread()) {
	throw new IllegalStateException("SurfaceTextureHelper must be created on the handler thread");
	}
	this.handler = handler;

	eglBase = EglBase.create(sharedContext, EglBase.CONFIG_PIXEL_BUFFER);
	try {
	// Both these statements have been observed to fail on rare occasions, see BUG=webrtc:5682.
	eglBase.createDummyPbufferSurface();
	eglBase.makeCurrent();
	} catch (RuntimeException e) {
	// Clean up before rethrowing the exception.
	eglBase.release();
	handler.getLooper().quit();
	throw e;
	}

	oesTextureId = GlUtil.generateTexture(GLES11Ext.GL_TEXTURE_EXTERNAL_OES);
	surfaceTexture = new SurfaceTexture(oesTextureId);
	surfaceTexture.setOnFrameAvailableListener(new SurfaceTexture.OnFrameAvailableListener() {
	@Override
	public void onFrameAvailable(SurfaceTexture surfaceTexture) {
	hasPendingTexture = true;
	tryDeliverTextureFrame();
	}
	});
	}

	private YuvConverter getYuvConverter() {
	// yuvConverter is assigned once
	if (yuvConverter != null)
	return yuvConverter;

	synchronized(this) {
	if (yuvConverter == null)
	yuvConverter = new YuvConverter(eglBase.getEglBaseContext());
	return yuvConverter;
	}
	}

	/**
	* Start to stream textures to the given \|listener\|. If you need to change listener, you need to
	* call stopListening() first.
	*/
	public void startListening(final OnTextureFrameAvailableListener listener) {
	if (this.listener != null \|\| this.pendingListener != null) {
	throw new IllegalStateException("SurfaceTextureHelper listener has already been set.");
	}
	this.pendingListener = listener;
	handler.post(setListenerRunnable);
	}

	/**
	* Stop listening. The listener set in startListening() is guaranteded to not receive any more
	* onTextureFrameAvailable() callbacks after this function returns.
	*/
	public void stopListening() {
	Logging.d(TAG, "stopListening()");
	handler.removeCallbacks(setListenerRunnable);
	ThreadUtils.invokeAtFrontUninterruptibly(handler, new Runnable() {
	@Override
	public void run() {
	listener = null;
	pendingListener = null;
	}
	});
	}

	/**
	* Retrieve the underlying SurfaceTexture. The SurfaceTexture should be passed in to a video
	* producer such as a camera or decoder.
	*/
	public SurfaceTexture getSurfaceTexture() {
	return surfaceTexture;
	}

	/**
	* Retrieve the handler that calls onTextureFrameAvailable(). This handler is valid until
	* dispose() is called.
	*/
	public Handler getHandler() {
	return handler;
	}

	/**
	* Call this function to signal that you are done with the frame received in
	* onTextureFrameAvailable(). Only one texture frame can be in flight at once, so you must call
	* this function in order to receive a new frame.
	*/
	public void returnTextureFrame() {
	handler.post(new Runnable() {
	@Override public void run() {
	isTextureInUse = false;
	if (isQuitting) {
	release();
	} else {
	tryDeliverTextureFrame();
	}
	}
	});
	}

	public boolean isTextureInUse() {
	return isTextureInUse;
	}

	/**
	* Call disconnect() to stop receiving frames. OpenGL resources are released and the handler is
	* stopped when the texture frame has been returned by a call to returnTextureFrame(). You are
	* guaranteed to not receive any more onTextureFrameAvailable() after this function returns.
	*/
	public void dispose() {
	Logging.d(TAG, "dispose()");
	ThreadUtils.invokeAtFrontUninterruptibly(handler, new Runnable() {
	@Override
	public void run() {
	isQuitting = true;
	if (!isTextureInUse) {
	release();
	}
	}
	});
	}

	public void textureToYUV(ByteBuffer buf,
	int width, int height, int stride, int textureId, float [] transformMatrix) {
	if (textureId != oesTextureId)
	throw new IllegalStateException("textureToByteBuffer called with unexpected textureId");

	getYuvConverter().convert(buf, width, height, stride, textureId, transformMatrix);
	}

	private void updateTexImage() {
	// SurfaceTexture.updateTexImage apparently can compete and deadlock with eglSwapBuffers,
	// as observed on Nexus 5. Therefore, synchronize it with the EGL functions.
	// See https://bugs.chromium.org/p/webrtc/issues/detail?id=5702 for more info.
	synchronized (EglBase.lock) {
	surfaceTexture.updateTexImage();
	}
	}

	private void tryDeliverTextureFrame() {
	if (handler.getLooper().getThread() != Thread.currentThread()) {
	throw new IllegalStateException("Wrong thread.");
	}
	if (isQuitting \|\| !hasPendingTexture \|\| isTextureInUse \|\| listener == null) {
	return;
	}
	isTextureInUse = true;
	hasPendingTexture = false;

	updateTexImage();

	final float[] transformMatrix = new float[16];
	surfaceTexture.getTransformMatrix(transformMatrix);
	final long timestampNs = (Build.VERSION.SDK_INT >= Build.VERSION_CODES.ICE_CREAM_SANDWICH)
	? surfaceTexture.getTimestamp()
	: TimeUnit.MILLISECONDS.toNanos(SystemClock.elapsedRealtime());
	listener.onTextureFrameAvailable(oesTextureId, transformMatrix, timestampNs);
	}

	private void release() {
	if (handler.getLooper().getThread() != Thread.currentThread()) {
	throw new IllegalStateException("Wrong thread.");
	}
	if (isTextureInUse \|\| !isQuitting) {
	throw new IllegalStateException("Unexpected release.");
	}
	synchronized (this) {
	if (yuvConverter != null)
	yuvConverter.release();
	}
	GLES20.glDeleteTextures(1, new int[] {oesTextureId}, 0);
	surfaceTexture.release();
	eglBase.release();
	handler.getLooper().quit();
	}
	}