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I'm trying to make some optimizations in a private video player for Linux aiming to improve performance because playing MP4 files are heavy on the CPU, since the video frames are encoded in YV12 and OpenGL doesn't provide a native way to display this format. Right now there's a code that runs on the CPU to converts YV12 to RGB before the image is sent to the GPU for display, and this consumes 100% of CPU processing.

I'm currently investigating how to decode YV12 frames without having to write a shader to do the YV12 -> RGB conversion. As far I as understand, one way to do this is through the GL_MESA_ycbcr_texture, apparently supported by my system (reported by glxinfo).

In this Fedora Box I have an ATI Technologies Inc RV610 video device [Radeon HD 2400 PRO], which is a decent video card. Then, I downloaded the yuvrect test and made a few changes to replace GL_TEXTURE_RECTANGLE_NV for a texture that is supported by this card: GL_TEXTURE_RECTANGLE_ARB.

However, when I execute this modified application it outputs:

The MESA driver reports *unsupported texture format in setup_hardware_state*

I noticed that this error shows up when glPopMatrix(); is executed from the Display() callback. Now, this doesn't seem like a bug in my application because I ran this exact same code on another Fedora box (same system) which has a different video card: Intel Corporation Sandy Bridge Integrated Graphics Controller (rev 09) , and it works beatifully.

The only visible difference between the 2 binaries are the libraries they are linked with. On the (problematic) ATI card ldd reports:

linux-gate.so.1 =>  (0x00da3000)
libGL.so.1 => /usr/lib/libGL.so.1 (0x077bd000)
libGLU.so.1 => /usr/lib/libGLU.so.1 (0x0783b000)
libglut.so.3 => /usr/lib/libglut.so.3 (0x005a9000)
libGLEW.so.1.5 => /usr/lib/libGLEW.so.1.5 (0x00aa3000)
libstdc++.so.6 => /usr/lib/libstdc++.so.6 (0x057e2000)
libm.so.6 => /lib/libm.so.6 (0x004e4000)
libgcc_s.so.1 => /lib/libgcc_s.so.1 (0x0053f000)
libc.so.6 => /lib/libc.so.6 (0x00358000)
libX11.so.6 => /usr/lib/libX11.so.6 (0x0071b000)
libXext.so.6 => /usr/lib/libXext.so.6 (0x009c5000)
libXdamage.so.1 => /usr/lib/libXdamage.so.1 (0x00af7000)
libXfixes.so.3 => /usr/lib/libXfixes.so.3 (0x00b76000)
libXxf86vm.so.1 => /usr/lib/libXxf86vm.so.1 (0x0014e000)
libdrm.so.2 => /usr/lib/libdrm.so.2 (0x00101000)
libpthread.so.0 => /lib/libpthread.so.0 (0x00510000)
libdl.so.2 => /lib/libdl.so.2 (0x0052d000)
libXi.so.6 => /usr/lib/libXi.so.6 (0x00110000)
/lib/ld-linux.so.2 (0x00337000)
libxcb.so.1 => /usr/lib/libxcb.so.1 (0x00859000)
librt.so.1 => /lib/librt.so.1 (0x00534000)
libXau.so.6 => /usr/lib/libXau.so.6 (0x00854000)

Meanwhile, on the Intel card you can see that it linked with libv4l and some other libraries while the ATI didn't! I wonder if this have anything to do with the problem I'm facing:

linux-gate.so.1 =>  (0x008d6000)
/usr/lib/libv4l/v4l1compat.so (0x00345000)
libGL.so.1 => /usr/lib/libGL.so.1 (0x4fb85000)
libGLU.so.1 => /usr/lib/libGLU.so.1 (0x4fc10000)
libglut.so.3 => /usr/lib/libglut.so.3 (0x005a9000)
libGLEW.so.1.5 => /usr/lib/libGLEW.so.1.5 (0x4fc82000)
libstdc++.so.6 => /usr/lib/libstdc++.so.6 (0x42ca7000)
libm.so.6 => /lib/libm.so.6 (0x41fbc000)
libgcc_s.so.1 => /lib/libgcc_s.so.1 (0x42017000)
libc.so.6 => /lib/libc.so.6 (0x41e30000)
libv4l1.so.0 => /usr/lib/libv4l1.so.0 (0x00110000)
libX11.so.6 => /usr/lib/libX11.so.6 (0x421f8000)
libXext.so.6 => /usr/lib/libXext.so.6 (0x424c0000)
libXdamage.so.1 => /usr/lib/libXdamage.so.1 (0x42c0e000)
libXfixes.so.3 => /usr/lib/libXfixes.so.3 (0x42d98000)
libXxf86vm.so.1 => /usr/lib/libXxf86vm.so.1 (0x432a2000)
libdrm.so.2 => /usr/lib/libdrm.so.2 (0x4247b000)
libpthread.so.0 => /lib/libpthread.so.0 (0x41fe8000)
libdl.so.2 => /lib/libdl.so.2 (0x42005000)
libXi.so.6 => /usr/lib/libXi.so.6 (0x42748000)
/lib/ld-linux.so.2 (0x41e0f000)
libv4l2.so.0 => /usr/lib/libv4l2.so.0 (0x4217c000)
libxcb.so.1 => /usr/lib/libxcb.so.1 (0x42337000)
librt.so.1 => /lib/librt.so.1 (0x4200c000)
libv4lconvert.so.0 => /usr/lib/libv4lconvert.so.0 (0x42357000)
libXau.so.6 => /usr/lib/libXau.so.6 (0x421f3000)
libjpeg.so.62 => /usr/lib/libjpeg.so.62 (0x43317000)

If you want to run the example below you'll need readtex.c , readtex.h and girl.rgb, and compile it with: g++ yuvrect.cpp -o yuvrect -lGL -lGLU -lglut -lGLEW

#include <assert.h>
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <GL/glew.h>
#include <GL/glut.h>

#include "readtex.c"   /* I know, this is a hack. */

#define TEXTURE_FILE "girl.rgb"

static GLfloat Xrot = 0, Yrot = 0, Zrot = 0;
static GLint ImgWidth, ImgHeight;
static GLushort *ImageYUV = NULL;


static void DrawObject(void)
{
   glBegin(GL_QUADS);

   glTexCoord2f(0, 0);
   glVertex2f(-1.0, -1.0);

   glTexCoord2f(ImgWidth, 0);
   glVertex2f(1.0, -1.0);

   glTexCoord2f(ImgWidth, ImgHeight);
   glVertex2f(1.0, 1.0);

   glTexCoord2f(0, ImgHeight);
   glVertex2f(-1.0, 1.0);

   glEnd();
}


static void Display( void )
{
   glClear( GL_COLOR_BUFFER_BIT );

   glPushMatrix();
      glRotatef(Xrot, 1.0, 0.0, 0.0);
      glRotatef(Yrot, 0.0, 1.0, 0.0);
      glRotatef(Zrot, 0.0, 0.0, 1.0);
      DrawObject();
   glPopMatrix(); // <--- error message comes from this call

   glutSwapBuffers();
}


static void Reshape( int width, int height )
{
   glViewport( 0, 0, width, height );
   glMatrixMode( GL_PROJECTION );
   glLoadIdentity();
   glFrustum( -1.0, 1.0, -1.0, 1.0, 10.0, 100.0 );
   glMatrixMode( GL_MODELVIEW );
   glLoadIdentity();
   glTranslatef( 0.0, 0.0, -15.0 );
}


static void Key( unsigned char key, int x, int y )
{
   (void) x;
   (void) y;
   switch (key) {
      case 27:
         exit(0);
         break;
   }
   glutPostRedisplay();
}


static void SpecialKey( int key, int x, int y )
{
   float step = 3.0;
   (void) x;
   (void) y;

   switch (key) {
      case GLUT_KEY_UP:
         Xrot += step;
         break;
      case GLUT_KEY_DOWN:
         Xrot -= step;
         break;
      case GLUT_KEY_LEFT:
         Yrot += step;
         break;
      case GLUT_KEY_RIGHT:
         Yrot -= step;
         break;
   }
   glutPostRedisplay();
}        

static void Init( int argc, char *argv[] )
{
   GLuint texObj = 100;
   const char *file;

   printf("Checking GL_ARB_texture_rectangle\n");
   if (!glutExtensionSupported("GL_ARB_texture_rectangle")) {
      printf("Sorry, GL_NV_texture_rectangle is required\n");
      exit(0);
   }

   printf("Checking GL_MESA_ycbcr_texture\n");
   if (!glutExtensionSupported("GL_MESA_ycbcr_texture")) {
      printf("Sorry, GL_MESA_ycbcr_texture is required\n");
      exit(0);
   }

   glPixelStorei(GL_UNPACK_ALIGNMENT, 1);

   glBindTexture(GL_TEXTURE_RECTANGLE_ARB, texObj);
#ifdef LINEAR_FILTER
   /* linear filtering looks much nicer but is much slower for Mesa */
   glTexParameteri(GL_TEXTURE_RECTANGLE_ARB, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
   glTexParameteri(GL_TEXTURE_RECTANGLE_ARB, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
#else
   glTexParameteri(GL_TEXTURE_RECTANGLE_ARB, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
   glTexParameteri(GL_TEXTURE_RECTANGLE_ARB, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
#endif

   if (argc > 1)
      file = argv[1];
   else
      file = TEXTURE_FILE;

   ImageYUV = LoadYUVImage(file, &ImgWidth, &ImgHeight);
   if (!ImageYUV) {
      printf("Couldn't read %s\n", TEXTURE_FILE);
      exit(0);
   }

   printf("Image: %dx%d\n", ImgWidth, ImgHeight);

   printf("Calling glTexImage2D\n");
   glTexImage2D(GL_TEXTURE_RECTANGLE_ARB, 0,
                GL_YCBCR_MESA, ImgWidth, ImgHeight, 0,
                GL_YCBCR_MESA, GL_UNSIGNED_SHORT_8_8_MESA, ImageYUV);
   printf("Called glTexImage2D\n");
   assert(glGetError() == GL_NO_ERROR);
   printf("* Assert #1\n");

   glTexSubImage2D(GL_TEXTURE_RECTANGLE_ARB, 0,
                   0, 0, ImgWidth, ImgHeight,
                   GL_YCBCR_MESA, GL_UNSIGNED_SHORT_8_8_MESA, ImageYUV);

   assert(glGetError() == GL_NO_ERROR);
   printf("* Assert #2\n");

   glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);

   glEnable(GL_TEXTURE_RECTANGLE_ARB);

   glShadeModel(GL_FLAT);
   glClearColor(0.3, 0.3, 0.4, 1.0);

   if (argc > 1 && strcmp(argv[1], "-info")==0) {
      printf("GL_RENDERER   = %s\n", (char *) glGetString(GL_RENDERER));
      printf("GL_VERSION    = %s\n", (char *) glGetString(GL_VERSION));
      printf("GL_VENDOR     = %s\n", (char *) glGetString(GL_VENDOR));
      printf("GL_EXTENSIONS = %s\n", (char *) glGetString(GL_EXTENSIONS));
   }
}


int main( int argc, char *argv[] )
{
   glutInit( &argc, argv );
   glutInitWindowSize( 300, 300 );
   glutInitWindowPosition( 0, 0 );
   glutInitDisplayMode( GLUT_RGB | GLUT_DOUBLE );
   glutCreateWindow(argv[0] );
   glewInit();

   Init( argc, argv );

   glutReshapeFunc( Reshape );
   glutKeyboardFunc( Key );
   glutSpecialFunc( SpecialKey );
   glutDisplayFunc( Display );

   glutMainLoop();
   return 0;
}

Any tips to solve this issue, guys?

karlphillip
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  • Is it actually **glPopMatrix** causing the error, or is the error message only flushed after **DrawObject**? On Fedora, you might need to get the lib4vl-devel package and / or patch (upgrade) MESA. It seems unlikely Mesa would have a dependency for colorspace encoding, but maybe it's worth a try. – Brett Hale Jan 20 '12 at 04:33
  • GDB tells me that it's `glPopMatrix()` that causes the error msg. – karlphillip Jan 20 '12 at 11:29

1 Answers1

5

this can most likely be accounted to a driver error, or something. I won't help you with that. However, it is not worth it to shy away from shaders. Using shaders, you can forget about the GL_MESA_ycbcr_texture and make your app more compatible.

We are going to use plain old GL_LUMINANCE_ALPHA format, so the image loads become:

glTexImage2D(GL_TEXTURE_RECTANGLE_ARB, 0,
            GL_LUMINANCE_ALPHA, ImgWidth, ImgHeight, 0,
            GL_LUMINANCE_ALPHA, GL_UNSIGNED_BYTE, ImageYUV);

glTexSubImage2D(GL_TEXTURE_RECTANGLE_ARB, 0,
               0, 0, ImgWidth, ImgHeight,
               GL_LUMINANCE_ALPHA, GL_UNSIGNED_BYTE, ImageYUV);

Then about the shaders:

static const char *p_s_vertex_shader =
    "varying vec2 t;"
    "void main()"
    "{"
    "    t = gl_MultiTexCoord0.xy;"
    "    gl_Position = ftransform();"
    "}";
static const char *p_s_fragment_shader =
    "#extension GL_ARB_texture_rectangle : enable\n"
    "varying vec2 t;"
    "uniform sampler2DRect tex;"
    "void main()"
    "{"
    "    vec2 tcEven = vec2(floor(t.x * .5) * 2.0, t.y);"
    "    vec2 tcOdd = vec2(tcEven.x + 1.0, t.y);"
    "    float Cb = texture2DRect(tex, tcEven).x - .5;"
    "    float Cr = texture2DRect(tex, tcOdd).x - .5;"
    "    float y = texture2DRect(tex, t).w;" // redundant texture read optimized away by texture cache
    "    float r = y + 1.28033 * Cr;"
    "    float g = y - .21482 * Cb - .38059 * Cr;"
    "    float b = y + 2.12798 * Cb;"
    "    gl_FragColor = vec4(r, g, b, 1.0);"
    "}";
int v = glCreateShader(GL_VERTEX_SHADER);
int f = glCreateShader(GL_FRAGMENT_SHADER);
int p = glCreateProgram();
glShaderSource(v, 1, &p_s_vertex_shader, 0);
glShaderSource(f, 1, &p_s_fragment_shader, 0);
glCompileShader(v);
//CheckShader(v);
glCompileShader(f);
//CheckShader(f);
glAttachShader(p, v);
glAttachShader(p, f);
glLinkProgram(p);
glUseProgram(p);
glUniform1i(glGetUniformLocation(p, "tex"), 0);

This come after the textures, somewhere at the end of Init(). And that's it, works like a charm. For debugging, it's probably better to include the CheckShader() as well (it reports compile errors in shaders):

bool CheckShader(int n_shader_object)
{
    int n_tmp;
    glGetShaderiv(n_shader_object, GL_COMPILE_STATUS, &n_tmp);
    bool b_compiled = n_tmp == GL_TRUE;
    int n_log_length;
    glGetShaderiv(n_shader_object, GL_INFO_LOG_LENGTH, &n_log_length);
    // query status ...

    if(n_log_length > 1) {
        char *p_s_temp_info_log;
        if(!(p_s_temp_info_log = (char*)malloc(n_log_length)))
            return false;
        int n_tmp;
        glGetShaderInfoLog(n_shader_object, n_log_length, &n_tmp,
            p_s_temp_info_log);
        assert(n_tmp <= n_log_length);

        fprintf(stderr, "%s\n", p_s_temp_info_log);
        free(p_s_temp_info_log);
    }
    // get/concat info-log

    return b_compiled;
}

The shader version will probably be a little bit slower than hardware optimized version, but i'd say it's nothing to worry about.

If you decide to give the code a try, and have any problems with it, let me know ...

EDIT: There actually was a problem running this on ATi, finally it turned out that there was error passing a varying variable "t", in other words this doesn't work:

static const char *p_s_vertex_shader =
    "varying vec2 t;"
    "void main()"
    "{"
    "    t = gl_MultiTexCoord0.xy;"
    "    gl_Position = ftransform();"
    "}";
static const char *p_s_fragment_shader =
    "#extension GL_ARB_texture_rectangle : enable\n"
    "varying vec2 t;"
    "uniform sampler2DRect tex;"
    "void main()"
    "{"
    "    gl_FragColor = texture2DRect(tex, t);"
    "}";

And to easily fix this, one can just remove the vertex shader and let the fixed pipeline write texture coordinates. So this works on ATi as well:

static const char *p_s_vertex_shader = null; // no vertex shader
static const char *p_s_fragment_shader =
    "#extension GL_ARB_texture_rectangle : enable\n"
    "uniform sampler2DRect tex;"
    "void main()"
    "{"
    "    vec2 t = gl_TexCoord[0];" // use fixed pipeline output 
    "    gl_FragColor = texture2DRect(tex, t);"
    "}";
Face Bloke
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  • I would love to see the code in my question using this stuff. I tried myself but my version didn't worked, I got a light-yellow rectangle draw in the screen, and the `CheckShader()` call didn't return any errors. – karlphillip Jan 20 '12 at 17:39
  • Hi, you mean the complete source code? See here: http://www.luki.webzdarma.cz/up/YCbCrShader.cpp (this is all the code in one file, kind of messy but works for me). I'm not sure if i changed anything ... so try running it and if it doesn't work, I'll try to think of something else ... – Face Bloke Jan 23 '12 at 08:15
  • Your code does work on other machines with *NVIDIA GeForce 7300* (Windows) and *Intel Corporation Sandy Bridge Integrated Graphics Controller (rev 09)* (Fedora Linux), but it doesn't display anything on *ATI Technologies Inc RV610 video device [Radeon HD 2400 PRO]* (Fedora Linux), which is very weird. It also doesn't print errors anymore. This issue is probably related to my video card drivers or a faulty GPU. Do you agree? – karlphillip Jan 23 '12 at 12:04
  • Well, I agree that ATi support of OpenGL is sometimes quite different. Let's try modifying the shader so only the y component is displayed. It should be modified to this: static const char *p_s_fragment_shader = "#extension GL_ARB_texture_rectangle : enable\n" "varying vec2 t;" "uniform sampler2DRect tex;" "void main()" "{" " float y = texture2DRect(tex, t).w;" " gl_FragColor = vec4(y, y, y, 1.0);" "}"; That should display grayscale image even on ati (sorry about posting code in comments). – Face Bloke Jan 23 '12 at 12:48
  • Thanks! Unfortunately that didn't work as well. The area where the image should appear in the image is gray though. Any more tips to pinpoint the problem? – karlphillip Jan 23 '12 at 13:32
  • Okay, that actually makes it simple. Either the ARB_texture_rectangle is broken, or texcoords are being not passed correctly on ATi. Let's try making it power-of-two texture. I'll repost the source code, but the modifications are just switching texture rectangle for texture 2d and setting texture size to 256x256 (it was 190 something, so there will be some unused space). Link: http://www.luki.webzdarma.cz/up/YCbCrShader_256.cpp – Face Bloke Jan 23 '12 at 13:58
  • Awesome. I just tested this new code and it still doesn't work on my machine, which indicates that the problem might be in *texcoords*. Is this right? – karlphillip Jan 23 '12 at 15:59
  • On a side note, can you confirm that this shaders convert YV12 to RGB? – karlphillip Jan 23 '12 at 16:16
  • Yes, that is correct. Let's try removing vertex shader and see what this does: http://www.luki.webzdarma.cz/up/YCbCrShader_novs.cpp (i'm afraid i gotta go home in a minute, but we WILL solve this) – Face Bloke Jan 23 '12 at 16:19
  • Yes, the (original post) shader converts YV12 to RGB. On my machine it displays an image of a girl (girl.rgb) that was converted to YV12, loaded to texture and displayed with conversion to RGB, using a shader. The "fixed"/debugging posts i'm linking here do not perform the conversion. But we will restore it as soon as we can find out where the problem with displaying a texture is. – Face Bloke Jan 23 '12 at 16:22
  • What do you know, the new code displayed correctly the gray image. Fantastic job! – karlphillip Jan 23 '12 at 17:01
  • let us [continue this discussion in chat](http://chat.stackoverflow.com/rooms/6972/discussion-between-karlphillip-and-face-bloke) – karlphillip Jan 23 '12 at 18:45
  • You've been very helpful so far! I decided to ask another question related to this subject in another thread so you can get more rep points if you are able to help again: http://stackoverflow.com/questions/8977489/problems-converting-yv12-to-rgb-through-glsl – karlphillip Jan 23 '12 at 19:35