Function initChromaPhaseTables

source/NTSC.cpp:919–1080

Build the 4 phase chroma lookup table The YI'Q' colors are hard-coded ===========================================================================

// The YI'Q' colors are hard-coded
//===========================================================================
static void initChromaPhaseTables (void)
{
	int phase,s,t,n;
	real z,y0,y1,c,i,q;
	real phi,zz;
	float brightness;
	double r64,g64,b64;
	float  r32,g32,b32;	

	for (phase = 0; phase < 4; ++phase)
	{
		phi = (phase * RAD_90) + CYCLESTART;
		for (s = 0; s < NTSC_NUM_SEQUENCES; ++s)
		{
			t = s;
			y0 = y1 = c = i = q = 0.0;

			for (n = 0; n < 12; ++n)
			{
				z = (real)(0 != (t & 0x800));
				t = t << 1;

				for(int k = 0; k < 2; k++ )
				{
					//z = z * 1.25;
					zz = initFilterSignal(z);
					c  = initFilterChroma(zz); // "Mostly" correct _if_ CYCLESTART = PI/4 = 45 degrees
					y0 = initFilterLuma0 (zz);
					y1 = initFilterLuma1 (zz - c);

					c = c * 2.f;
					i = i + (c * cos(phi) - i) / 8.f;
					q = q + (c * sin(phi) - q) / 8.f;

					phi += RAD_45;
				} // k
			} // samples

			brightness = clampZeroOne( (float)z );
			g_aBnWMonitor[s].b = (uint8_t)(brightness * 255);
			g_aBnWMonitor[s].g = (uint8_t)(brightness * 255);
			g_aBnWMonitor[s].r = (uint8_t)(brightness * 255);
			g_aBnWMonitor[s].a = 255;

			brightness = clampZeroOne( (float)y1);
			g_aBnwColorTV[s].b = (uint8_t)(brightness * 255);
			g_aBnwColorTV[s].g = (uint8_t)(brightness * 255);
			g_aBnwColorTV[s].r = (uint8_t)(brightness * 255);
			g_aBnwColorTV[s].a = 255;
			
			/*
				YI'V' to RGB

				[r g b] = [y i v][ 1      1      1    ]
				                 [0.956  -0.272 -1.105]
				                 [0.621  -0.647  1.702]

				[r]   [1   0.956  0.621][y]