/* Setup texture units and fragment program */
void drawInit(void) {
	uint8_t		i, j, k;
	float		y, cb, cr;
	char 		fragProg[] = "!!ARBfp1.0\n\
	                              TEMP ycbcr;\n\
				      TEMP rgb;\n\
				      PARAM scale = { 0.8032226, 0.875, 0.875, 1.0 };\n\
				      TEX ycbcr.r, fragment.texcoord[0], texture[0], RECT;\n\
			              TEX ycbcr.g, fragment.texcoord[1], texture[1], RECT;\n\
			              TEX ycbcr.b, fragment.texcoord[2], texture[2], RECT;\n\
			              MUL ycbcr, ycbcr, scale;\n\
			              TEX rgb, ycbcr, texture[3], 3D;\n\
				      MUL result.color, rgb, fragment.color;\n\
				      END";

	/* YCbCR to RGB fragment program */
	globals.ycbcrtorgb = malloc(strlen(fragProg) + 1);
	strcpy(globals.ycbcrtorgb, fragProg);

	/* 3D lookup table for YCrCb to RGB conversion */
	glGenTextures(1, &globals.lut);
	glActiveTexture(GL_TEXTURE3);
	glBindTexture(GL_TEXTURE_3D, globals.lut);
	glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
	glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
 	glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_WRAP_S, GL_CLAMP);
	glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_WRAP_T, GL_CLAMP);
	glTexParameteri(GL_TEXTURE_3D, GL_TEXTURE_WRAP_R, GL_CLAMP);

	/* Build and load YCrCb to RGB lookup table */
	for(i = 0; i < 7; i++) {
		for(j = 0; j < 7; j++) {
			for(k = 0; k < 7; k++) {
				y = (float)k / 6.0;
				cb = (float)j / 6.0 - 0.5;
				cr = (float)i / 6.0 - 0.5;
				globals.defaultlut[i][j][k][0] = y + 1.402 * cr;
				globals.defaultlut[i][j][k][1] = y - 0.34414 * cb - 0.71414 * cr;
				globals.defaultlut[i][j][k][2] = y + 1.772 * cb;
			}
		}
	}
	glTexImage3D(GL_TEXTURE_3D, 0, GL_RGB, 8, 8, 8, 0, GL_RGB, GL_FLOAT, globals.defaultlut);

--

/* Setup GL to draw YCbCr 4:2:0 video */
void glSetupColourspaceConversion(void) {
	glActiveTexture(GL_TEXTURE0);
	glEnable(GL_TEXTURE_RECTANGLE_NV);

	glActiveTexture(GL_TEXTURE1);
	glEnable(GL_TEXTURE_RECTANGLE_NV);

	glActiveTexture(GL_TEXTURE2);
	glEnable(GL_TEXTURE_RECTANGLE_NV);

	glActiveTexture(GL_TEXTURE3);
	glEnable(GL_TEXTURE_3D);

	glEnable(GL_FRAGMENT_PROGRAM_ARB);
	glProgramStringARB(GL_FRAGMENT_PROGRAM_ARB, GL_PROGRAM_FORMAT_ASCII_ARB, strlen(globals.ycbcrtorgb), globals.ycbcrtorgb);
}

/* Setup GL to draw RGB interface elements */
void glUnsetupColourspaceConversion(void) {
	glActiveTexture(GL_TEXTURE0);
	glDisable(GL_TEXTURE_RECTANGLE_NV);

	glActiveTexture(GL_TEXTURE1);
	glDisable(GL_TEXTURE_RECTANGLE_NV);

	glActiveTexture(GL_TEXTURE2);
	glDisable(GL_TEXTURE_RECTANGLE_NV);

	glActiveTexture(GL_TEXTURE3);
	glDisable(GL_TEXTURE_3D);

	glDisable(GL_FRAGMENT_PROGRAM_ARB);
}



--

		/* Draw channel to Tx window in back buffer, yes it has to be upside down */
		glSetupColourspaceConversion();

		glActiveTexture(GL_TEXTURE0);
		glBindTexture(GL_TEXTURE_RECTANGLE_NV, state.channels[i].ytex);
		glActiveTexture(GL_TEXTURE1);
		glBindTexture(GL_TEXTURE_RECTANGLE_NV, state.channels[i].cbtex);
		glActiveTexture(GL_TEXTURE2);
		glBindTexture(GL_TEXTURE_RECTANGLE_NV, state.channels[i].crtex);

		glBegin(GL_QUADS);
		glMultiTexCoord2i(GL_TEXTURE0, 0, 0);
		glMultiTexCoord2i(GL_TEXTURE1, 0, 0);
		glMultiTexCoord2i(GL_TEXTURE2, 0, 0);
		glVertex2i(x, y + 576);
		glMultiTexCoord2i(GL_TEXTURE0, s->planeWidth[0], 0);
		glMultiTexCoord2i(GL_TEXTURE1, s->planeWidth[1], 0);
		glMultiTexCoord2i(GL_TEXTURE2, s->planeWidth[2], 0);
		glVertex2i(x + 720, y + 576);
		glMultiTexCoord2i(GL_TEXTURE0, s->planeWidth[0], s->planeHeight[0]);
		glMultiTexCoord2i(GL_TEXTURE1, s->planeWidth[1], s->planeHeight[1]);
		glMultiTexCoord2i(GL_TEXTURE2, s->planeWidth[2], s->planeHeight[2]);
		glVertex2i(x + 720, y);
		glMultiTexCoord2i(GL_TEXTURE0, 0, s->planeHeight[0]);
		glMultiTexCoord2i(GL_TEXTURE1, 0, s->planeHeight[1]);
		glMultiTexCoord2i(GL_TEXTURE2, 0, s->planeHeight[2]);
		glVertex2i(x, y);
		glEnd();

		glUnsetupColourspaceConversion();