StackOverflow2013

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POOpenGL Texture Rate too slow?
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copied!<p>I have a 5 megapixel texture that I am having trouble updating. The texture is displayed on a rectangle not dissimilar to a video stream.</p> <p>The OpenGL commands execute quickly, but the real texture update rate is sub optimal, perhaps only 3 actual frames per second. There is some change, but not much change when using a smaller texture (500x500). </p> <p>The machine has a NVIDIA gtx 570</p> <p>My initial efforts were to use <code>glTexSubImage2D</code> and <code>glBufferSubData</code>, but these performed slightly worse than the memory mapped scheme.</p> <p>Is there any way to force the graphics card to update the texture? How is video streaming software written?</p> <p><strong>Render Loop</strong></p> <pre><code>void glStream::paintGL() { glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glLoadIdentity(); program1.bind(); program1.setUniformValue("texture", 0); program1.enableAttributeArray(vertexAttr1); program1.enableAttributeArray(vertexTexr1); program1.setAttributeArray(vertexAttr1, vertices.constData()); program1.setAttributeArray(vertexTexr1, texCoords.constData()); // glECheck(); glBindTexture(GL_TEXTURE_2D, textures[0]); glBindBuffer(GL_PIXEL_UNPACK_BUFFER_ARB,pbos[0]); void* memory = glMapBuffer(GL_PIXEL_UNPACK_BUFFER_ARB,GL_WRITE_ONLY); device->fillBuffer((unsigned char *)memory,heightGL,widthGL); // takes 2ms (not long) glUnmapBuffer(GL_PIXEL_UNPACK_BUFFER_ARB); glTexSubImage2D(GL_TEXTURE_2D,0,0,0,widthGL,heightGL,GL_LUMINANCE,GL_UNSIGNED_BYTE, NULL); glDrawArrays(GL_TRIANGLES, 0, vertices.size()); glBindBuffer(GL_PIXEL_UNPACK_BUFFER_ARB,0); glBindTexture(GL_TEXTURE_2D,0); // program1.disableAttributeArray(vertexTexr1); program1.disableAttributeArray(vertexAttr1); program1.release(); glECheck();//no errors } </code></pre> <p><strong>Texture Reservation</strong></p> <pre><code>void glStream::reserveTextures() { assert(numGLFrames>0); assert(glGenBuffers); displayBuff = (GLubyte*) calloc(numGLFrames*widthGL*heightGL,sizeof(GLubyte));//GL_RGB8 memset(displayBuff,100,numGLFrames*widthGL*heightGL*sizeof(GLubyte)); glGenBuffers(1,&pbos[0]); glBindBuffer(GL_PIXEL_UNPACK_BUFFER_ARB, pbos[0]); glBufferData(GL_PIXEL_UNPACK_BUFFER_ARB, numGLFrames*widthGL*heightGL*sizeof(GLubyte), &displayBuff[0], GL_STREAM_DRAW); glBindBuffer(GL_PIXEL_UNPACK_BUFFER_ARB, 0); glGenTextures(1,&textures[0]); glBindTexture(GL_TEXTURE_2D,textures[0]); glTexImage2D(GL_TEXTURE_2D,0,GL_LUMINANCE, widthGL,heightGL,0,GL_LUMINANCE,GL_UNSIGNED_BYTE,NULL); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_GENERATE_MIPMAP, GL_FALSE); glBindTexture(GL_TEXTURE_2D,0); } </code></pre> <p><strong>Initialization</strong></p> <pre><code>void glStream::initializeGL() { GLenum err = glewInit(); if (GLEW_OK != err) { const char * emssage = (const char*)glewGetErrorString(err); QMessageBox::information(0, "OpenGL 3.x Context Example", emssage); exit(20); } glDisable(GL_DEPTH_TEST); QGLShader *vshader1 = new QGLShader(QGLShader::Vertex, this); const char *vsrc1 = "attribute vec2 coord2d; \n" "attribute mediump vec4 texCoord;\n" "varying mediump vec4 texc;\n" "void main() \n" "{ \n" " gl_Position = vec4(coord2d, 0.0, 1.0); \n" " texc = texCoord;\n" "} \n"; vshader1->compileSourceCode(vsrc1); QGLShader *fshader1 = new QGLShader(QGLShader::Fragment, this); const char *fsrc1 = "uniform sampler2D texture;\n" "varying mediump vec4 texc;\n" "void main(void)\n" "{\n" " gl_FragColor = texture2D(texture, texc.st);\n" "}\n"; fshader1->compileSourceCode(fsrc1); program1.addShader(vshader1); program1.addShader(fshader1); program1.link(); vertexAttr1 = program1.attributeLocation( "coord2d"); vertexTexr1 = program1.attributeLocation( "texCoord"); // Create the vertex buffer. vertices.clear(); float u=1; #define AVEC -u,u #define BVEC -u,-u #define CVEC u,u #define DVEC u,-u vertices << QVector2D(AVEC);vertices << QVector2D(BVEC); vertices << QVector2D(CVEC);vertices << QVector2D(BVEC); vertices << QVector2D(DVEC);vertices << QVector2D(CVEC); // Create the texture vertex buffer #define TAVEC 0,1 #define TBVEC 0,0 #define TCVEC 1,1 #define TDVEC 1,0 texCoords << QVector2D(TAVEC);texCoords << QVector2D(TBVEC); texCoords << QVector2D(TCVEC);texCoords << QVector2D(TBVEC); texCoords << QVector2D(TDVEC);texCoords << QVector2D(TCVEC); glECheck(); reserveTextures(); } </code></pre> <p><strong>Edit 1</strong></p> <p>I am confident that fill buffer comes up with a new texture because in some other part of the code I write this texture to a file and it is indeed different. Its a sad day when my File IO is faster then a OpenGL texture.</p> <p><strong>Edit 2</strong> I tried out FRAPS and I verified that the render loop is going at ~18 FPS, but the visible updates are slower (maybe 3 FPS). What could account for such a discrepancy?</p>

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