apply a mutated bisqwit's deemph approach instead

trunk/src/palette.cpp

@@ -86,8 +86,6 @@ pal *palo;
 	(type) (y + to_rgb [4] * i + to_rgb [5] * q)\
 )
 
-
-
 static void ApplyDeemphasisNTSC(int entry, u8& r, u8& g, u8& b)
 {
 				static float const to_float = 1.0f / 0xFF;
@@ -155,10 +153,101 @@ static void ApplyDeemphasisNTSC(int entry, u8& r, u8& g, u8& b)
 		{ 0.956f, 0.621f, -0.272f, -0.647f, -1.105f, 1.702f };
 	fb = YIQ_TO_RGB( y, i, q, default_decoder, float, fr, fg );
 
-	#define CLAMP(x) (x<0?0:(x>1.0f?1.0f:x))
+	#define CLAMP(x) ((x)<0?0:((x)>1.0f?1.0f:(x)))
 	r = (u8)(CLAMP(fr)*255);
 	g = (u8)(CLAMP(fg)*255);
 	b = (u8)(CLAMP(fb)*255);
+
+	//doesnt help
+	//float gamma=1.8f;
+ //       auto gammafix = [=](float f) { return f < 0.f ? 0.f : std::pow(f, 2.2f / gamma); };
+ //       auto clamp = [](int v) { return v<0 ? 0 : v>255 ? 255 : v; };
+ //       r = clamp(255 * gammafix(y +  0.946882f*i +  0.623557f*q));
+ //       g = clamp(255 * gammafix(y + -0.274788f*i + -0.635691f*q));
+ //       b = clamp(255 * gammafix(y + -1.108545f*i +  1.709007f*q));
+}
+
+float bisqwit_gammafix(float f, float gamma) { return f < 0.f ? 0.f : std::pow(f, 2.2f / gamma); }
+int bisqwit_clamp(int v) { return v<0 ? 0 : v>255 ? 255 : v; }
+
+// Calculate the luma and chroma by emulating the relevant circuits:
+int bisqwit_wave(int p, int color) { return (color+p+8)%12 < 6; }
+
+static void ApplyDeemphasisBisqwit(int entry, u8& r, u8& g, u8& b)
+{
+	if(entry<64) return;
+	int myr, myg, myb;
+	// The input value is a NES color index (with de-emphasis bits).
+	// We need RGB values. Convert the index into RGB.
+	// For most part, this process is described at:
+	//    http://wiki.nesdev.com/w/index.php/NTSC_video
+
+	// Decode the color index
+	int color = (entry & 0x0F), level = color<0xE ? (entry>>4) & 3 : 1;
+
+	// Voltage levels, relative to synch voltage
+	static const float black=.518f, white=1.962f, attenuation=.746f,
+		levels[8] = {.350f, .518f, .962f,1.550f,  // Signal low
+		1.094f,1.506f,1.962f,1.962f}; // Signal high
+
+	float lo_and_hi[2] = { levels[level + 4 * (color == 0x0)],
+		levels[level + 4 * (color <  0xD)] };
+
+
+
+	//fceux alteration: two passes
+	//1st pass calculates bisqwit's base color
+	//2nd pass calculates it with deemph
+	//finally, we'll do something dumb: find a 'scale factor' between them and apply it to the input palette. (later, we could pregenerate the scale factors)
+	//whatever, it gets the job done.
+	for(int pass=0;pass<2;pass++)
+	{
+		float y=0.f, i=0.f, q=0.f, gamma=1.8f;
+		for(int p=0; p<12; ++p) // 12 clock cycles per pixel.
+		{
+			// NES NTSC modulator (square wave between two voltage levels):
+			float spot = lo_and_hi[bisqwit_wave(p,color)];
+
+			// De-emphasis bits attenuate a part of the signal:
+			if(pass==1)
+			{
+				if(((entry & 0x40) && bisqwit_wave(p,12))
+					|| ((entry & 0x80) && bisqwit_wave(p, 4))
+					|| ((entry &0x100) && bisqwit_wave(p, 8))) spot *= attenuation;
+			}
+
+			// Normalize:
+			float v = (spot - black) / (white-black) / 12.f;
+
+			// Ideal TV NTSC demodulator:
+			y += v;
+			i += v * std::cos(3.141592653 * p / 6);
+			q += v * std::sin(3.141592653 * p / 6); // Or cos(... p-3 ... )
+			// Note: Integrating cos() and sin() for p-0.5 .. p+0.5 range gives
+			//       the exactly same result, scaled by a factor of 2*cos(pi/12).
+		}
+
+		// Convert YIQ into RGB according to FCC-sanctioned conversion matrix.
+
+		int rt = bisqwit_clamp(255 * bisqwit_gammafix(y +  0.946882f*i +  0.623557f*q,gamma));
+		int gt = bisqwit_clamp(255 * bisqwit_gammafix(y + -0.274788f*i + -0.635691f*q,gamma));
+		int bt = bisqwit_clamp(255 * bisqwit_gammafix(y + -1.108545f*i +  1.709007f*q,gamma));
+
+		if(pass==0) myr = rt, myg = gt, myb = bt;
+		else
+		{
+			float rscale = (float)rt / myr;
+			float gscale = (float)gt / myg;
+			float bscale = (float)bt / myb;
+			#define BCLAMP(x) ((x)<0?0:((x)>255?255:(x)))
+			if(myr!=0) r = (u8)(BCLAMP(r*rscale));
+			if(myg!=0) g = (u8)(BCLAMP(g*gscale));
+			if(myb!=0) b = (u8)(BCLAMP(b*bscale));
+		}
+	}
+
+
+
 }
 
 //classic algorithm
@@ -195,7 +284,7 @@ static void ApplyDeemphasisComplete(pal* pal512)
 		for(int p=0;p<64;p++,idx++)
 		{
 			pal512[idx] = pal512[p];
-			ApplyDeemphasisNTSC(idx,pal512[idx].r,pal512[idx].g,pal512[idx].b);
+			ApplyDeemphasisBisqwit(idx,pal512[idx].r,pal512[idx].g,pal512[idx].b);
 		}
 	}
 }