talk/app/webrtc/objc/RTCEAGLVideoRenderer.mm - platform/external/webrtc - Git at Google

 /*
  * libjingle
  * Copyright 2014, Google Inc.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
  *
  *  1. Redistributions of source code must retain the above copyright notice,
  *     this list of conditions and the following disclaimer.
  *  2. Redistributions in binary form must reproduce the above copyright notice,
  *     this list of conditions and the following disclaimer in the documentation
  *     and/or other materials provided with the distribution.
  *  3. The name of the author may not be used to endorse or promote products
  *     derived from this software without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
  * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
  * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
  * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
  * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */

 #if !defined(__has_feature) || !__has_feature(objc_arc)
 #error "This file requires ARC support."
 #endif

 #import "RTCEAGLVideoRenderer.h"

 #import <OpenGLES/ES2/gl.h>
 #import "RTCI420Frame.h"

 // TODO(tkchin): check and log openGL errors. Methods here return BOOLs in
 // anticipation of that happening in the future.

 // Convenience macro for writing shader code that converts a code snippet into
 // a C string during the C preprocessor step.
 #define RTC_STRINGIZE(...) #__VA_ARGS__

 // Vertex shader doesn't do anything except pass coordinates through.
 static const char kVertexShaderSource[] = RTC_STRINGIZE(
   attribute vec2 position;
   attribute vec2 texcoord;
   varying vec2 v_texcoord;
   void main() {
     gl_Position = vec4(position.x, position.y, 0.0, 1.0);
     v_texcoord = texcoord;
   }
 );

 // Fragment shader converts YUV values from input textures into a final RGB
 // pixel. The conversion formula is from http://www.fourcc.org/fccyvrgb.php.
 static const char kFragmentShaderSource[] = RTC_STRINGIZE(
   precision highp float;
   varying vec2 v_texcoord;
   uniform lowp sampler2D s_textureY;
   uniform lowp sampler2D s_textureU;
   uniform lowp sampler2D s_textureV;
   void main() {
     float y, u, v, r, g, b;
     y = texture2D(s_textureY, v_texcoord).r;
     u = texture2D(s_textureU, v_texcoord).r;
     v = texture2D(s_textureV, v_texcoord).r;
     u = u - 0.5;
     v = v - 0.5;
     r = y + 1.403 * v;
     g = y - 0.344 * u - 0.714 * v;
     b = y + 1.770 * u;
     gl_FragColor = vec4(r, g, b, 1.0);
   }
 );

 // Compiles a shader of the given |type| with GLSL source |source| and returns
 // the shader handle or 0 on error.
 GLuint CreateShader(GLenum type, const GLchar* source) {
   GLuint shader = glCreateShader(type);
   if (!shader) {
     return 0;
   }
   glShaderSource(shader, 1, &source, NULL);
   glCompileShader(shader);
   GLint compileStatus = GL_FALSE;
   glGetShaderiv(shader, GL_COMPILE_STATUS, &compileStatus);
   if (compileStatus == GL_FALSE) {
     glDeleteShader(shader);
     shader = 0;
   }
   return shader;
 }

 // Links a shader program with the given vertex and fragment shaders and
 // returns the program handle or 0 on error.
 GLuint CreateProgram(GLuint vertexShader, GLuint fragmentShader) {
   if (vertexShader == 0 || fragmentShader == 0) {
     return 0;
   }
   GLuint program = glCreateProgram();
   if (!program) {
     return 0;
   }
   glAttachShader(program, vertexShader);
   glAttachShader(program, fragmentShader);
   glLinkProgram(program);
   GLint linkStatus = GL_FALSE;
   glGetProgramiv(program, GL_LINK_STATUS, &linkStatus);
   if (linkStatus == GL_FALSE) {
     glDeleteProgram(program);
     program = 0;
   }
   return program;
 }

 // When modelview and projection matrices are identity (default) the world is
 // contained in the square around origin with unit size 2. Drawing to these
 // coordinates is equivalent to drawing to the entire screen. The texture is
 // stretched over that square using texture coordinates (u, v) that range
 // from (0, 0) to (1, 1) inclusive. Texture coordinates are flipped vertically
 // here because the incoming frame has origin in upper left hand corner but
 // OpenGL expects origin in bottom left corner.
 const GLfloat gVertices[] = {
     // X, Y, U, V.
     -1, -1, 0, 1,  // Bottom left.
     1,  -1, 1, 1,  // Bottom right.
     1,  1,  1, 0,  // Top right.
     -1, 1,  0, 0,  // Top left.
 };

 // |kNumTextures| must not exceed 8, which is the limit in OpenGLES2. Two sets
 // of 3 textures are used here, one for each of the Y, U and V planes. Having
 // two sets alleviates CPU blockage in the event that the GPU is asked to render
 // to a texture that is already in use.
 static const GLsizei kNumTextureSets = 2;
 static const GLsizei kNumTextures = 3 * kNumTextureSets;

 @implementation RTCEAGLVideoRenderer {
   EAGLContext* _context;
   BOOL _isInitialized;
   NSUInteger _currentTextureSet;
   // Handles for OpenGL constructs.
   GLuint _textures[kNumTextures];
   GLuint _program;
   GLuint _vertexBuffer;
   GLint _position;
   GLint _texcoord;
   GLint _ySampler;
   GLint _uSampler;
   GLint _vSampler;
 }

 + (void)initialize {
   // Disable dithering for performance.
   glDisable(GL_DITHER);
 }

 - (instancetype)initWithContext:(EAGLContext*)context {
   NSAssert(context != nil, @"context cannot be nil");
   if (self = [super init]) {
     _context = context;
   }
   return self;
 }

 - (BOOL)drawFrame:(RTCI420Frame*)frame {
   if (!_isInitialized) {
     return NO;
   }
   if (_lastDrawnFrame == frame) {
     return NO;
   }
   [self ensureGLContext];
   if (![self updateTextureSizesForFrame:frame] ||
       ![self updateTextureDataForFrame:frame]) {
     return NO;
   }
   glClear(GL_COLOR_BUFFER_BIT);
   glBindBuffer(GL_ARRAY_BUFFER, _vertexBuffer);
   glDrawArrays(GL_TRIANGLE_FAN, 0, 4);
   _lastDrawnFrame = frame;
   return YES;
 }

 - (void)setupGL {
   if (_isInitialized) {
     return;
   }
   [self ensureGLContext];
   if (![self setupProgram]) {
     return;
   }
   if (![self setupTextures]) {
     return;
   }
   if (![self setupVertices]) {
     return;
   }
   glUseProgram(_program);
   glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
   glClearColor(0, 0, 0, 1);
   _isInitialized = YES;
 }

 - (void)teardownGL {
   if (!_isInitialized) {
     return;
   }
   [self ensureGLContext];
   glDeleteProgram(_program);
   _program = 0;
   glDeleteTextures(kNumTextures, _textures);
   glDeleteBuffers(1, &_vertexBuffer);
   _vertexBuffer = 0;
   _isInitialized = NO;
 }

 #pragma mark - Private

 - (void)ensureGLContext {
   if ([EAGLContext currentContext] != _context) {
     NSAssert(_context, @"context shouldn't be nil");
     [EAGLContext setCurrentContext:_context];
   }
 }

 - (BOOL)setupProgram {
   NSAssert(!_program, @"program already set up");
   GLuint vertexShader = CreateShader(GL_VERTEX_SHADER, kVertexShaderSource);
   GLuint fragmentShader =
       CreateShader(GL_FRAGMENT_SHADER, kFragmentShaderSource);
   _program = CreateProgram(vertexShader, fragmentShader);
   // Shaders are created only to generate program.
   if (vertexShader) {
     glDeleteShader(vertexShader);
   }
   if (fragmentShader) {
     glDeleteShader(fragmentShader);
   }
   if (!_program) {
     return NO;
   }
   _position = glGetAttribLocation(_program, "position");
   _texcoord = glGetAttribLocation(_program, "texcoord");
   _ySampler = glGetUniformLocation(_program, "s_textureY");
   _uSampler = glGetUniformLocation(_program, "s_textureU");
   _vSampler = glGetUniformLocation(_program, "s_textureV");
   if (_position < 0 || _texcoord < 0 || _ySampler < 0 || _uSampler < 0 ||
       _vSampler < 0) {
     return NO;
   }
   return YES;
 }

 - (BOOL)setupTextures {
   glGenTextures(kNumTextures, _textures);
   // Set parameters for each of the textures we created.
   for (GLsizei i = 0; i < kNumTextures; i++) {
     glActiveTexture(GL_TEXTURE0 + i);
     glBindTexture(GL_TEXTURE_2D, _textures[i]);
     glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
     glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
     glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
     glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
   }
   return YES;
 }

 - (BOOL)updateTextureSizesForFrame:(RTCI420Frame*)frame {
   if (frame.height == _lastDrawnFrame.height &&
       frame.width == _lastDrawnFrame.width &&
       frame.chromaWidth == _lastDrawnFrame.chromaWidth &&
       frame.chromaHeight == _lastDrawnFrame.chromaHeight) {
     return YES;
   }
   GLsizei lumaWidth = frame.width;
   GLsizei lumaHeight = frame.height;
   GLsizei chromaWidth = frame.chromaWidth;
   GLsizei chromaHeight = frame.chromaHeight;
   for (GLint i = 0; i < kNumTextureSets; i++) {
     glActiveTexture(GL_TEXTURE0 + i * 3);
     glTexImage2D(GL_TEXTURE_2D,
                  0,
                  GL_LUMINANCE,
                  lumaWidth,
                  lumaHeight,
                  0,
                  GL_LUMINANCE,
                  GL_UNSIGNED_BYTE,
                  0);

     glActiveTexture(GL_TEXTURE0 + i * 3 + 1);
     glTexImage2D(GL_TEXTURE_2D,
                  0,
                  GL_LUMINANCE,
                  chromaWidth,
                  chromaHeight,
                  0,
                  GL_LUMINANCE,
                  GL_UNSIGNED_BYTE,
                  0);

     glActiveTexture(GL_TEXTURE0 + i * 3 + 2);
     glTexImage2D(GL_TEXTURE_2D,
                  0,
                  GL_LUMINANCE,
                  chromaWidth,
                  chromaHeight,
                  0,
                  GL_LUMINANCE,
                  GL_UNSIGNED_BYTE,
                  0);
   }
   return YES;
 }

 - (BOOL)updateTextureDataForFrame:(RTCI420Frame*)frame {
   NSUInteger textureOffset = _currentTextureSet * 3;
   NSAssert(textureOffset + 3 <= kNumTextures, @"invalid offset");
   NSParameterAssert(frame.yPitch == frame.width);
   NSParameterAssert(frame.uPitch == frame.chromaWidth);
   NSParameterAssert(frame.vPitch == frame.chromaWidth);

   glActiveTexture(GL_TEXTURE0 + textureOffset);
   // When setting texture sampler uniforms, the texture index is used not
   // the texture handle.
   glUniform1i(_ySampler, textureOffset);
   glTexImage2D(GL_TEXTURE_2D,
                0,
                GL_LUMINANCE,
                frame.width,
                frame.height,
                0,
                GL_LUMINANCE,
                GL_UNSIGNED_BYTE,
                frame.yPlane);

   glActiveTexture(GL_TEXTURE0 + textureOffset + 1);
   glUniform1i(_uSampler, textureOffset + 1);
   glTexImage2D(GL_TEXTURE_2D,
                0,
                GL_LUMINANCE,
                frame.chromaWidth,
                frame.chromaHeight,
                0,
                GL_LUMINANCE,
                GL_UNSIGNED_BYTE,
                frame.uPlane);

   glActiveTexture(GL_TEXTURE0 + textureOffset + 2);
   glUniform1i(_vSampler, textureOffset + 2);
   glTexImage2D(GL_TEXTURE_2D,
                0,
                GL_LUMINANCE,
                frame.chromaWidth,
                frame.chromaHeight,
                0,
                GL_LUMINANCE,
                GL_UNSIGNED_BYTE,
                frame.vPlane);

   _currentTextureSet = (_currentTextureSet + 1) % kNumTextureSets;
   return YES;
 }

 - (BOOL)setupVertices {
   NSAssert(!_vertexBuffer, @"vertex buffer already set up");
   glGenBuffers(1, &_vertexBuffer);
   if (!_vertexBuffer) {
     return NO;
   }
   glBindBuffer(GL_ARRAY_BUFFER, _vertexBuffer);
   glBufferData(GL_ARRAY_BUFFER, sizeof(gVertices), gVertices, GL_DYNAMIC_DRAW);

   // Read position attribute from |gVertices| with size of 2 and stride of 4
   // beginning at the start of the array. The last argument indicates offset
   // of data within |gVertices| as supplied to the vertex buffer.
   glVertexAttribPointer(
       _position, 2, GL_FLOAT, GL_FALSE, 4 * sizeof(GLfloat), (void*)0);
   glEnableVertexAttribArray(_position);

   // Read texcoord attribute from |gVertices| with size of 2 and stride of 4
   // beginning at the first texcoord in the array. The last argument indicates
   // offset of data within |gVertices| as supplied to the vertex buffer.
   glVertexAttribPointer(_texcoord,
                         2,
                         GL_FLOAT,
                         GL_FALSE,
                         4 * sizeof(GLfloat),
                         (void*)(2 * sizeof(GLfloat)));
   glEnableVertexAttribArray(_texcoord);

   return YES;
 }

 @end
	/*
	* libjingle
	* Copyright 2014, Google Inc.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions are met:
	*
	* 1. Redistributions of source code must retain the above copyright notice,
	* this list of conditions and the following disclaimer.
	* 2. Redistributions in binary form must reproduce the above copyright notice,
	* this list of conditions and the following disclaimer in the documentation
	* and/or other materials provided with the distribution.
	* 3. The name of the author may not be used to endorse or promote products
	* derived from this software without specific prior written permission.
	*
	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
	* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
	* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
	* EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
	* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
	* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
	* OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
	* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
	* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
	* ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	*/

	#if !defined(__has_feature) \|\| !__has_feature(objc_arc)
	#error "This file requires ARC support."
	#endif

	#import "RTCEAGLVideoRenderer.h"

	#import <OpenGLES/ES2/gl.h>
	#import "RTCI420Frame.h"

	// TODO(tkchin): check and log openGL errors. Methods here return BOOLs in
	// anticipation of that happening in the future.

	// Convenience macro for writing shader code that converts a code snippet into
	// a C string during the C preprocessor step.
	#define RTC_STRINGIZE(...) #__VA_ARGS__

	// Vertex shader doesn't do anything except pass coordinates through.
	static const char kVertexShaderSource[] = RTC_STRINGIZE(
	attribute vec2 position;
	attribute vec2 texcoord;
	varying vec2 v_texcoord;
	void main() {
	gl_Position = vec4(position.x, position.y, 0.0, 1.0);
	v_texcoord = texcoord;
	}
	);

	// Fragment shader converts YUV values from input textures into a final RGB
	// pixel. The conversion formula is from http://www.fourcc.org/fccyvrgb.php.
	static const char kFragmentShaderSource[] = RTC_STRINGIZE(
	precision highp float;
	varying vec2 v_texcoord;
	uniform lowp sampler2D s_textureY;
	uniform lowp sampler2D s_textureU;
	uniform lowp sampler2D s_textureV;
	void main() {
	float y, u, v, r, g, b;
	y = texture2D(s_textureY, v_texcoord).r;
	u = texture2D(s_textureU, v_texcoord).r;
	v = texture2D(s_textureV, v_texcoord).r;
	u = u - 0.5;
	v = v - 0.5;
	r = y + 1.403 * v;
	g = y - 0.344 * u - 0.714 * v;
	b = y + 1.770 * u;
	gl_FragColor = vec4(r, g, b, 1.0);
	}
	);

	// Compiles a shader of the given \|type\| with GLSL source \|source\| and returns
	// the shader handle or 0 on error.
	GLuint CreateShader(GLenum type, const GLchar* source) {
	GLuint shader = glCreateShader(type);
	if (!shader) {
	return 0;
	}
	glShaderSource(shader, 1, &source, NULL);
	glCompileShader(shader);
	GLint compileStatus = GL_FALSE;
	glGetShaderiv(shader, GL_COMPILE_STATUS, &compileStatus);
	if (compileStatus == GL_FALSE) {
	glDeleteShader(shader);
	shader = 0;
	}
	return shader;
	}

	// Links a shader program with the given vertex and fragment shaders and
	// returns the program handle or 0 on error.
	GLuint CreateProgram(GLuint vertexShader, GLuint fragmentShader) {
	if (vertexShader == 0 \|\| fragmentShader == 0) {
	return 0;
	}
	GLuint program = glCreateProgram();
	if (!program) {
	return 0;
	}
	glAttachShader(program, vertexShader);
	glAttachShader(program, fragmentShader);
	glLinkProgram(program);
	GLint linkStatus = GL_FALSE;
	glGetProgramiv(program, GL_LINK_STATUS, &linkStatus);
	if (linkStatus == GL_FALSE) {
	glDeleteProgram(program);
	program = 0;
	}
	return program;
	}

	// When modelview and projection matrices are identity (default) the world is
	// contained in the square around origin with unit size 2. Drawing to these
	// coordinates is equivalent to drawing to the entire screen. The texture is
	// stretched over that square using texture coordinates (u, v) that range
	// from (0, 0) to (1, 1) inclusive. Texture coordinates are flipped vertically
	// here because the incoming frame has origin in upper left hand corner but
	// OpenGL expects origin in bottom left corner.
	const GLfloat gVertices[] = {
	// X, Y, U, V.
	-1, -1, 0, 1, // Bottom left.
	1, -1, 1, 1, // Bottom right.
	1, 1, 1, 0, // Top right.
	-1, 1, 0, 0, // Top left.
	};

	// \|kNumTextures\| must not exceed 8, which is the limit in OpenGLES2. Two sets
	// of 3 textures are used here, one for each of the Y, U and V planes. Having
	// two sets alleviates CPU blockage in the event that the GPU is asked to render
	// to a texture that is already in use.
	static const GLsizei kNumTextureSets = 2;
	static const GLsizei kNumTextures = 3 * kNumTextureSets;

	@implementation RTCEAGLVideoRenderer {
	EAGLContext* _context;
	BOOL _isInitialized;
	NSUInteger _currentTextureSet;
	// Handles for OpenGL constructs.
	GLuint _textures[kNumTextures];
	GLuint _program;
	GLuint _vertexBuffer;
	GLint _position;
	GLint _texcoord;
	GLint _ySampler;
	GLint _uSampler;
	GLint _vSampler;
	}

	+ (void)initialize {
	// Disable dithering for performance.
	glDisable(GL_DITHER);
	}

	- (instancetype)initWithContext:(EAGLContext*)context {
	NSAssert(context != nil, @"context cannot be nil");
	if (self = [super init]) {
	_context = context;
	}
	return self;
	}

	- (BOOL)drawFrame:(RTCI420Frame*)frame {
	if (!_isInitialized) {
	return NO;
	}
	if (_lastDrawnFrame == frame) {
	return NO;
	}
	[self ensureGLContext];
	if (![self updateTextureSizesForFrame:frame] \|\|
	![self updateTextureDataForFrame:frame]) {
	return NO;
	}
	glClear(GL_COLOR_BUFFER_BIT);
	glBindBuffer(GL_ARRAY_BUFFER, _vertexBuffer);
	glDrawArrays(GL_TRIANGLE_FAN, 0, 4);
	_lastDrawnFrame = frame;
	return YES;
	}

	- (void)setupGL {
	if (_isInitialized) {
	return;
	}
	[self ensureGLContext];
	if (![self setupProgram]) {
	return;
	}
	if (![self setupTextures]) {
	return;
	}
	if (![self setupVertices]) {
	return;
	}
	glUseProgram(_program);
	glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
	glClearColor(0, 0, 0, 1);
	_isInitialized = YES;
	}

	- (void)teardownGL {
	if (!_isInitialized) {
	return;
	}
	[self ensureGLContext];
	glDeleteProgram(_program);
	_program = 0;
	glDeleteTextures(kNumTextures, _textures);
	glDeleteBuffers(1, &_vertexBuffer);
	_vertexBuffer = 0;
	_isInitialized = NO;
	}

	#pragma mark - Private

	- (void)ensureGLContext {
	if ([EAGLContext currentContext] != _context) {
	NSAssert(_context, @"context shouldn't be nil");
	[EAGLContext setCurrentContext:_context];
	}
	}

	- (BOOL)setupProgram {
	NSAssert(!_program, @"program already set up");
	GLuint vertexShader = CreateShader(GL_VERTEX_SHADER, kVertexShaderSource);
	GLuint fragmentShader =
	CreateShader(GL_FRAGMENT_SHADER, kFragmentShaderSource);
	_program = CreateProgram(vertexShader, fragmentShader);
	// Shaders are created only to generate program.
	if (vertexShader) {
	glDeleteShader(vertexShader);
	}
	if (fragmentShader) {
	glDeleteShader(fragmentShader);
	}
	if (!_program) {
	return NO;
	}
	_position = glGetAttribLocation(_program, "position");
	_texcoord = glGetAttribLocation(_program, "texcoord");
	_ySampler = glGetUniformLocation(_program, "s_textureY");
	_uSampler = glGetUniformLocation(_program, "s_textureU");
	_vSampler = glGetUniformLocation(_program, "s_textureV");
	if (_position < 0 \|\| _texcoord < 0 \|\| _ySampler < 0 \|\| _uSampler < 0 \|\|
	_vSampler < 0) {
	return NO;
	}
	return YES;
	}

	- (BOOL)setupTextures {
	glGenTextures(kNumTextures, _textures);
	// Set parameters for each of the textures we created.
	for (GLsizei i = 0; i < kNumTextures; i++) {
	glActiveTexture(GL_TEXTURE0 + i);
	glBindTexture(GL_TEXTURE_2D, _textures[i]);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
	}
	return YES;
	}

	- (BOOL)updateTextureSizesForFrame:(RTCI420Frame*)frame {
	if (frame.height == _lastDrawnFrame.height &&
	frame.width == _lastDrawnFrame.width &&
	frame.chromaWidth == _lastDrawnFrame.chromaWidth &&
	frame.chromaHeight == _lastDrawnFrame.chromaHeight) {
	return YES;
	}
	GLsizei lumaWidth = frame.width;
	GLsizei lumaHeight = frame.height;
	GLsizei chromaWidth = frame.chromaWidth;
	GLsizei chromaHeight = frame.chromaHeight;
	for (GLint i = 0; i < kNumTextureSets; i++) {
	glActiveTexture(GL_TEXTURE0 + i * 3);
	glTexImage2D(GL_TEXTURE_2D,
	0,
	GL_LUMINANCE,
	lumaWidth,
	lumaHeight,
	0,
	GL_LUMINANCE,
	GL_UNSIGNED_BYTE,
	0);

	glActiveTexture(GL_TEXTURE0 + i * 3 + 1);
	glTexImage2D(GL_TEXTURE_2D,
	0,
	GL_LUMINANCE,
	chromaWidth,
	chromaHeight,
	0,
	GL_LUMINANCE,
	GL_UNSIGNED_BYTE,
	0);

	glActiveTexture(GL_TEXTURE0 + i * 3 + 2);
	glTexImage2D(GL_TEXTURE_2D,
	0,
	GL_LUMINANCE,
	chromaWidth,
	chromaHeight,
	0,
	GL_LUMINANCE,
	GL_UNSIGNED_BYTE,
	0);
	}
	return YES;
	}

	- (BOOL)updateTextureDataForFrame:(RTCI420Frame*)frame {
	NSUInteger textureOffset = _currentTextureSet * 3;
	NSAssert(textureOffset + 3 <= kNumTextures, @"invalid offset");
	NSParameterAssert(frame.yPitch == frame.width);
	NSParameterAssert(frame.uPitch == frame.chromaWidth);
	NSParameterAssert(frame.vPitch == frame.chromaWidth);

	glActiveTexture(GL_TEXTURE0 + textureOffset);
	// When setting texture sampler uniforms, the texture index is used not
	// the texture handle.
	glUniform1i(_ySampler, textureOffset);
	glTexImage2D(GL_TEXTURE_2D,
	0,
	GL_LUMINANCE,
	frame.width,
	frame.height,
	0,
	GL_LUMINANCE,
	GL_UNSIGNED_BYTE,
	frame.yPlane);

	glActiveTexture(GL_TEXTURE0 + textureOffset + 1);
	glUniform1i(_uSampler, textureOffset + 1);
	glTexImage2D(GL_TEXTURE_2D,
	0,
	GL_LUMINANCE,
	frame.chromaWidth,
	frame.chromaHeight,
	0,
	GL_LUMINANCE,
	GL_UNSIGNED_BYTE,
	frame.uPlane);

	glActiveTexture(GL_TEXTURE0 + textureOffset + 2);
	glUniform1i(_vSampler, textureOffset + 2);
	glTexImage2D(GL_TEXTURE_2D,
	0,
	GL_LUMINANCE,
	frame.chromaWidth,
	frame.chromaHeight,
	0,
	GL_LUMINANCE,
	GL_UNSIGNED_BYTE,
	frame.vPlane);

	_currentTextureSet = (_currentTextureSet + 1) % kNumTextureSets;
	return YES;
	}

	- (BOOL)setupVertices {
	NSAssert(!_vertexBuffer, @"vertex buffer already set up");
	glGenBuffers(1, &_vertexBuffer);
	if (!_vertexBuffer) {
	return NO;
	}
	glBindBuffer(GL_ARRAY_BUFFER, _vertexBuffer);
	glBufferData(GL_ARRAY_BUFFER, sizeof(gVertices), gVertices, GL_DYNAMIC_DRAW);

	// Read position attribute from \|gVertices\| with size of 2 and stride of 4
	// beginning at the start of the array. The last argument indicates offset
	// of data within \|gVertices\| as supplied to the vertex buffer.
	glVertexAttribPointer(
	_position, 2, GL_FLOAT, GL_FALSE, 4 * sizeof(GLfloat), (void*)0);
	glEnableVertexAttribArray(_position);

	// Read texcoord attribute from \|gVertices\| with size of 2 and stride of 4
	// beginning at the first texcoord in the array. The last argument indicates
	// offset of data within \|gVertices\| as supplied to the vertex buffer.
	glVertexAttribPointer(_texcoord,
	2,
	GL_FLOAT,
	GL_FALSE,
	4 * sizeof(GLfloat),
	(void)(2 sizeof(GLfloat)));
	glEnableVertexAttribArray(_texcoord);

	return YES;
	}

	@end