sdk/android/api/org/webrtc/YuvConverter.java - src.git - 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.opengl.GLES11Ext;
 import android.opengl.GLES20;
 import java.nio.ByteBuffer;
 import java.nio.FloatBuffer;
 import org.webrtc.VideoFrame.I420Buffer;
 import org.webrtc.VideoFrame.TextureBuffer;

 /**
  * Class for converting OES textures to a YUV ByteBuffer. It should be constructed on a thread with
  * an active EGL context, and only be used from that thread.
  */
 public class YuvConverter {
   // 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.
   });

   // clang-format off
   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 OES_FRAGMENT_SHADER =
         "#extension GL_OES_EGL_image_external : require\n"
       + "precision mediump float;\n"
       + "varying vec2 interp_tc;\n"
       + "\n"
       + "uniform samplerExternalOES tex;\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(tex, interp_tc - 1.5 * xUnit).rgb);\n"
       + "  gl_FragColor.g = coeffs.a + dot(coeffs.rgb,\n"
       + "      texture2D(tex, interp_tc - 0.5 * xUnit).rgb);\n"
       + "  gl_FragColor.b = coeffs.a + dot(coeffs.rgb,\n"
       + "      texture2D(tex, interp_tc + 0.5 * xUnit).rgb);\n"
       + "  gl_FragColor.a = coeffs.a + dot(coeffs.rgb,\n"
       + "      texture2D(tex, interp_tc + 1.5 * xUnit).rgb);\n"
       + "}\n";

   private static final String RGB_FRAGMENT_SHADER =
         "precision mediump float;\n"
       + "varying vec2 interp_tc;\n"
       + "\n"
       + "uniform sampler2D tex;\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(tex, interp_tc - 1.5 * xUnit).rgb);\n"
       + "  gl_FragColor.g = coeffs.a + dot(coeffs.rgb,\n"
       + "      texture2D(tex, interp_tc - 0.5 * xUnit).rgb);\n"
       + "  gl_FragColor.b = coeffs.a + dot(coeffs.rgb,\n"
       + "      texture2D(tex, interp_tc + 0.5 * xUnit).rgb);\n"
       + "  gl_FragColor.a = coeffs.a + dot(coeffs.rgb,\n"
       + "      texture2D(tex, interp_tc + 1.5 * xUnit).rgb);\n"
       + "}\n";
   // clang-format on

   private final ThreadUtils.ThreadChecker threadChecker = new ThreadUtils.ThreadChecker();
   private final GlTextureFrameBuffer textureFrameBuffer;
   private TextureBuffer.Type shaderTextureType;
   private GlShader shader;
   private int texMatrixLoc;
   private int xUnitLoc;
   private int coeffsLoc;
   private boolean released = false;

   /**
    * This class should be constructed on a thread that has an active EGL context.
    */
   public YuvConverter() {
     threadChecker.checkIsOnValidThread();
     textureFrameBuffer = new GlTextureFrameBuffer(GLES20.GL_RGBA);
   }

   /** Converts the texture buffer to I420. */
   public I420Buffer convert(TextureBuffer textureBuffer) {
     final int width = textureBuffer.getWidth();
     final int height = textureBuffer.getHeight();

     // SurfaceTextureHelper requires a stride that is divisible by 8.  Round width up.
     // See SurfaceTextureHelper for details on the size and format.
     final int stride = ((width + 7) / 8) * 8;
     final int uvHeight = (height + 1) / 2;
     // Due to the layout used by SurfaceTextureHelper, vPos + stride * uvHeight would overrun the
     // buffer.  Add one row at the bottom to compensate for this.  There will never be data in the
     // extra row, but now other code does not have to deal with v stride * v height exceeding the
     // buffer's capacity.
     final int size = stride * (height + uvHeight + 1);
     ByteBuffer buffer = JniCommon.allocateNativeByteBuffer(size);
     convert(buffer, width, height, stride, textureBuffer.getTextureId(),
         RendererCommon.convertMatrixFromAndroidGraphicsMatrix(textureBuffer.getTransformMatrix()),
         textureBuffer.getType());

     final int yPos = 0;
     final int uPos = yPos + stride * height;
     // Rows of U and V alternate in the buffer, so V data starts after the first row of U.
     final int vPos = uPos + stride / 2;

     buffer.position(yPos);
     buffer.limit(yPos + stride * height);
     ByteBuffer dataY = buffer.slice();

     buffer.position(uPos);
     buffer.limit(uPos + stride * uvHeight);
     ByteBuffer dataU = buffer.slice();

     buffer.position(vPos);
     buffer.limit(vPos + stride * uvHeight);
     ByteBuffer dataV = buffer.slice();

     // SurfaceTextureHelper uses the same stride for Y, U, and V data.
     return JavaI420Buffer.wrap(width, height, dataY, stride, dataU, stride, dataV, stride,
         () -> { JniCommon.freeNativeByteBuffer(buffer); });
   }

   /** Deprecated, use convert(TextureBuffer). */
   @Deprecated
   void convert(ByteBuffer buf, int width, int height, int stride, int srcTextureId,
       float[] transformMatrix) {
     convert(buf, width, height, stride, srcTextureId, transformMatrix, TextureBuffer.Type.OES);
   }

   private void initShader(TextureBuffer.Type textureType) {
     if (shader != null) {
       shader.release();
     }

     final String fragmentShader;
     switch (textureType) {
       case OES:
         fragmentShader = OES_FRAGMENT_SHADER;
         break;
       case RGB:
         fragmentShader = RGB_FRAGMENT_SHADER;
         break;
       default:
         throw new IllegalArgumentException("Unsupported texture type.");
     }

     shaderTextureType = textureType;
     shader = new GlShader(VERTEX_SHADER, fragmentShader);
     shader.useProgram();
     texMatrixLoc = shader.getUniformLocation("texMatrix");
     xUnitLoc = shader.getUniformLocation("xUnit");
     coeffsLoc = shader.getUniformLocation("coeffs");
     GLES20.glUniform1i(shader.getUniformLocation("tex"), 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);
   }

   private void convert(ByteBuffer buf, int width, int height, int stride, int srcTextureId,
       float[] transformMatrix, TextureBuffer.Type textureType) {
     threadChecker.checkIsOnValidThread();
     if (released) {
       throw new IllegalStateException("YuvConverter.convert called on released object");
     }
     if (textureType != shaderTextureType) {
       initShader(textureType);
     }

     // 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());

     final int frameBufferWidth = stride / 4;
     final int frameBufferHeight = total_height;
     textureFrameBuffer.setSize(frameBufferWidth, frameBufferHeight);

     // Bind our framebuffer.
     GLES20.glBindFramebuffer(GLES20.GL_FRAMEBUFFER, textureFrameBuffer.getFrameBufferId());
     GlUtil.checkNoGLES2Error("glBindFramebuffer");

     GLES20.glActiveTexture(GLES20.GL_TEXTURE0);
     GLES20.glBindTexture(textureType.getGlTarget(), srcTextureId);
     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, frameBufferWidth, frameBufferHeight, GLES20.GL_RGBA, GLES20.GL_UNSIGNED_BYTE, buf);

     GlUtil.checkNoGLES2Error("YuvConverter.convert");

     // Restore normal framebuffer.
     GLES20.glBindFramebuffer(GLES20.GL_FRAMEBUFFER, 0);
     GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, 0);

     // Unbind texture. Reportedly needed on some devices to get
     // the texture updated from the camera.
     GLES20.glBindTexture(textureType.getGlTarget(), 0);
   }

   public void release() {
     threadChecker.checkIsOnValidThread();
     released = true;
     if (shader != null) {
       shader.release();
     }
     textureFrameBuffer.release();
   }
 }
	/*
	* 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.opengl.GLES11Ext;
	import android.opengl.GLES20;
	import java.nio.ByteBuffer;
	import java.nio.FloatBuffer;
	import org.webrtc.VideoFrame.I420Buffer;
	import org.webrtc.VideoFrame.TextureBuffer;

	/**
	* Class for converting OES textures to a YUV ByteBuffer. It should be constructed on a thread with
	* an active EGL context, and only be used from that thread.
	*/
	public class YuvConverter {
	// 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.
	});

	// clang-format off
	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 OES_FRAGMENT_SHADER =
	"#extension GL_OES_EGL_image_external : require\n"
	+ "precision mediump float;\n"
	+ "varying vec2 interp_tc;\n"
	+ "\n"
	+ "uniform samplerExternalOES tex;\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(tex, interp_tc - 1.5 * xUnit).rgb);\n"
	+ " gl_FragColor.g = coeffs.a + dot(coeffs.rgb,\n"
	+ " texture2D(tex, interp_tc - 0.5 * xUnit).rgb);\n"
	+ " gl_FragColor.b = coeffs.a + dot(coeffs.rgb,\n"
	+ " texture2D(tex, interp_tc + 0.5 * xUnit).rgb);\n"
	+ " gl_FragColor.a = coeffs.a + dot(coeffs.rgb,\n"
	+ " texture2D(tex, interp_tc + 1.5 * xUnit).rgb);\n"
	+ "}\n";

	private static final String RGB_FRAGMENT_SHADER =
	"precision mediump float;\n"
	+ "varying vec2 interp_tc;\n"
	+ "\n"
	+ "uniform sampler2D tex;\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(tex, interp_tc - 1.5 * xUnit).rgb);\n"
	+ " gl_FragColor.g = coeffs.a + dot(coeffs.rgb,\n"
	+ " texture2D(tex, interp_tc - 0.5 * xUnit).rgb);\n"
	+ " gl_FragColor.b = coeffs.a + dot(coeffs.rgb,\n"
	+ " texture2D(tex, interp_tc + 0.5 * xUnit).rgb);\n"
	+ " gl_FragColor.a = coeffs.a + dot(coeffs.rgb,\n"
	+ " texture2D(tex, interp_tc + 1.5 * xUnit).rgb);\n"
	+ "}\n";
	// clang-format on

	private final ThreadUtils.ThreadChecker threadChecker = new ThreadUtils.ThreadChecker();
	private final GlTextureFrameBuffer textureFrameBuffer;
	private TextureBuffer.Type shaderTextureType;
	private GlShader shader;
	private int texMatrixLoc;
	private int xUnitLoc;
	private int coeffsLoc;
	private boolean released = false;

	/**
	* This class should be constructed on a thread that has an active EGL context.
	*/
	public YuvConverter() {
	threadChecker.checkIsOnValidThread();
	textureFrameBuffer = new GlTextureFrameBuffer(GLES20.GL_RGBA);
	}

	/** Converts the texture buffer to I420. */
	public I420Buffer convert(TextureBuffer textureBuffer) {
	final int width = textureBuffer.getWidth();
	final int height = textureBuffer.getHeight();

	// SurfaceTextureHelper requires a stride that is divisible by 8. Round width up.
	// See SurfaceTextureHelper for details on the size and format.
	final int stride = ((width + 7) / 8) * 8;
	final int uvHeight = (height + 1) / 2;
	// Due to the layout used by SurfaceTextureHelper, vPos + stride * uvHeight would overrun the
	// buffer. Add one row at the bottom to compensate for this. There will never be data in the
	// extra row, but now other code does not have to deal with v stride * v height exceeding the
	// buffer's capacity.
	final int size = stride * (height + uvHeight + 1);
	ByteBuffer buffer = JniCommon.allocateNativeByteBuffer(size);
	convert(buffer, width, height, stride, textureBuffer.getTextureId(),
	RendererCommon.convertMatrixFromAndroidGraphicsMatrix(textureBuffer.getTransformMatrix()),
	textureBuffer.getType());

	final int yPos = 0;
	final int uPos = yPos + stride * height;
	// Rows of U and V alternate in the buffer, so V data starts after the first row of U.
	final int vPos = uPos + stride / 2;

	buffer.position(yPos);
	buffer.limit(yPos + stride * height);
	ByteBuffer dataY = buffer.slice();

	buffer.position(uPos);
	buffer.limit(uPos + stride * uvHeight);
	ByteBuffer dataU = buffer.slice();

	buffer.position(vPos);
	buffer.limit(vPos + stride * uvHeight);
	ByteBuffer dataV = buffer.slice();

	// SurfaceTextureHelper uses the same stride for Y, U, and V data.
	return JavaI420Buffer.wrap(width, height, dataY, stride, dataU, stride, dataV, stride,
	() -> { JniCommon.freeNativeByteBuffer(buffer); });
	}

	/** Deprecated, use convert(TextureBuffer). */
	@Deprecated
	void convert(ByteBuffer buf, int width, int height, int stride, int srcTextureId,
	float[] transformMatrix) {
	convert(buf, width, height, stride, srcTextureId, transformMatrix, TextureBuffer.Type.OES);
	}

	private void initShader(TextureBuffer.Type textureType) {
	if (shader != null) {
	shader.release();
	}

	final String fragmentShader;
	switch (textureType) {
	case OES:
	fragmentShader = OES_FRAGMENT_SHADER;
	break;
	case RGB:
	fragmentShader = RGB_FRAGMENT_SHADER;
	break;
	default:
	throw new IllegalArgumentException("Unsupported texture type.");
	}

	shaderTextureType = textureType;
	shader = new GlShader(VERTEX_SHADER, fragmentShader);
	shader.useProgram();
	texMatrixLoc = shader.getUniformLocation("texMatrix");
	xUnitLoc = shader.getUniformLocation("xUnit");
	coeffsLoc = shader.getUniformLocation("coeffs");
	GLES20.glUniform1i(shader.getUniformLocation("tex"), 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);
	}

	private void convert(ByteBuffer buf, int width, int height, int stride, int srcTextureId,
	float[] transformMatrix, TextureBuffer.Type textureType) {
	threadChecker.checkIsOnValidThread();
	if (released) {
	throw new IllegalStateException("YuvConverter.convert called on released object");
	}
	if (textureType != shaderTextureType) {
	initShader(textureType);
	}

	// 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());

	final int frameBufferWidth = stride / 4;
	final int frameBufferHeight = total_height;
	textureFrameBuffer.setSize(frameBufferWidth, frameBufferHeight);

	// Bind our framebuffer.
	GLES20.glBindFramebuffer(GLES20.GL_FRAMEBUFFER, textureFrameBuffer.getFrameBufferId());
	GlUtil.checkNoGLES2Error("glBindFramebuffer");

	GLES20.glActiveTexture(GLES20.GL_TEXTURE0);
	GLES20.glBindTexture(textureType.getGlTarget(), srcTextureId);
	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, frameBufferWidth, frameBufferHeight, GLES20.GL_RGBA, GLES20.GL_UNSIGNED_BYTE, buf);

	GlUtil.checkNoGLES2Error("YuvConverter.convert");

	// Restore normal framebuffer.
	GLES20.glBindFramebuffer(GLES20.GL_FRAMEBUFFER, 0);
	GLES20.glBindTexture(GLES20.GL_TEXTURE_2D, 0);

	// Unbind texture. Reportedly needed on some devices to get
	// the texture updated from the camera.
	GLES20.glBindTexture(textureType.getGlTarget(), 0);
	}

	public void release() {
	threadChecker.checkIsOnValidThread();
	released = true;
	if (shader != null) {
	shader.release();
	}
	textureFrameBuffer.release();
	}
	}