How to display RGB24 video frame using opengl

Question

My task is to render a set of 50 RGB frames using openGL's glut library.

I tried: In 3D cube rotation, i have a set of vertices using which i render it to the window. However, in case of rendering the RGB frames what should be done? Below is the code using which i render my 3d cube:

#include <glut.h>

GLfloat vertices[24]={-1.0,-1.0,-1.0,1.0,-1.0,-1.0,1.0,1.0,-1.0,-1.0,1.0,-1.0,-1.0,-1.0,1.0,1.0,-1.0,1.0,1.0,1.0,1.0,-1.0,1.0,1.0};
GLfloat colors[24]={-1.0,-1.0,-1.0,1.0,-1.0,-1.0,1.0,1.0,-1.0,-1.0,1.0,-1.0,-1.0,-1.0,1.0,1.0,-1.0,1.0,1.0,1.0,1.0,-1.0,1.0,1.0};
GLubyte cubeIndices[24]={0,3,2,1,2,3,7,6,0,4,7,3,1,2,6,5,4,5,6,7,0,1,5,4};
static GLfloat theta[3]={0,0,0};
static GLint axis=2;

void display()
{
    glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);

    glLoadIdentity();
    glRotatef(theta[0],1.0,0.0,0.0);
    glRotatef(theta[1],0.0,1.0,0.0);
    glRotatef(theta[2],0.0,0.0,1.0);

    glDrawElements(GL_QUADS,24,GL_UNSIGNED_BYTE,cubeIndices);

    glutSwapBuffers();
    glFlush();
}

void spinCude()
{
    theta[axis]+=2.0;
    if(theta[axis]>360.0)
        theta[axis]-=360.0;
    display();
}
void init()
{
    glMatrixMode(GL_PROJECTION);
    glOrtho(-2.0,2.0,-2.0,2.0,-10.0,10.0);
    glMatrixMode(GL_MODELVIEW);
}

void mouse(int btn,int state, int x,int y)
{
    if(btn==GLUT_LEFT_BUTTON&& state==GLUT_DOWN) axis=0;
    if(btn==GLUT_MIDDLE_BUTTON&& state==GLUT_DOWN) axis=1;
    if(btn==GLUT_RIGHT_BUTTON&& state==GLUT_DOWN) axis=2;
}

void main(int argc, char **argv)
{
    glutInit(&argc,argv);
    glutInitDisplayMode(GLUT_DOUBLE|GLUT_RGB|GLUT_DEPTH);

    glutInitWindowSize(500,500);
    glutCreateWindow("Simple YUV Player");
    init();
    glutDisplayFunc(display);

    glutIdleFunc(spinCude);
    glutMouseFunc(mouse);
    glEnable(GL_DEPTH_TEST);

    glEnableClientState(GL_VERTEX_ARRAY);
    glVertexPointer(3,GL_FLOAT,0,vertices);

    //glEnableClientState(GL_COLOR_ARRAY);
    glVertexPointer(3,GL_FLOAT,0,colors);

    glutMainLoop();

}

Can anyone suggest me some example or tutorial such that i can modify above code to display RGB frames.

Answer 1

Once you have your RGB-Frame as raw-data in memory things are pretty straight-forward. Create a texture using glGenTextures, bind it using glBindTexture and upload the data via glTexImage2D or glTexSubImage2D. Then render a fullscreen quad or whatever you like with that texture. The benefit of that is that you could render multiple 'virtual' TVs in your scene just by rendering multiple quads with that same texture, imagine a TV-Store where the same video runs on dozen of TVs. glDrawPixels might also work but it is much less versatile.

I don't know if uploading via texture is the way to go (hardware accelerated movie playback programs like VLC are most likely doing something far more advanced), but it should be a good start.

Answer 2

As Marius already suggested, implement texture mapping first. It's rather straigth forward any texture mapping tutorial will do.

Rendering frames are not the best with OpenGL you should try to avoid them as much as you can since it may involve a client -> host memory copy which is really costy ( takes too much time ) or simply it just takes up too much memory. Anyways if you really have to do it just generate as much textures as you need with glGenTextures load them up with the textures by glTexImage2D and then flip over the frames with a simple loop in each frame.

P.S. Judging by your application's name "YUV Player" you may also need to convert the input data since OpenGL mostly uses RGB not YUV.