/*
YV12 chroma upsampling fixer
by Kurt Bernhard 'Leak' Pruenner

Use with YV12 output if the half-resolution chroma 
gets upsampled in hardware by doubling the values
instead of interpolating between them.

(i.e. if you're getting blocky red edges on dark 
backgrounds...)
*/

sampler s0 : register(s0);
float4 p0 : register(c0);
float4 p1 : register(c1);

#define width (p0[0])
#define height (p0[1])

float4 getPixel(float2 tex, float dx, float dy)
{
	tex.x+=dx;
	tex.y+=dy;
	
	return tex2D(s0, tex);
}

float4 rgb2yuv(float4 rgb)
{
	float4x4 coeffs=
		{
			 0.299, 0.587, 0.114, 0.000,
			-0.147,-0.289, 0.436, 0.000,
			 0.615,-0.515,-0.100, 0.000,
			 0.000, 0.000, 0.000, 0.000
		};
		
	return mul(coeffs,rgb);
}

float4 yuv2rgb(float4 yuv)
{
	float4x4 coeffs=
		{
			 1.000, 0.000, 1.140, 0.000,
			 1.000,-0.395,-0.581, 0.000,
			 1.000, 2.032, 0.000, 0.000,
			 0.000, 0.000, 0.000, 0.000
		};
	
	return mul(coeffs,yuv);
}

float4 main(float2 tex : TEXCOORD0) : COLOR
{
	float dx=1/width;
	float dy=1/height;
	
	float4 yuv00=rgb2yuv(getPixel(tex,-dx,-dy));
	float4 yuv01=rgb2yuv(getPixel(tex,-dx,  0));
	float4 yuv02=rgb2yuv(getPixel(tex,-dx, dy));
	float4 yuv10=rgb2yuv(getPixel(tex,  0,-dy));
	float4 yuv11=rgb2yuv(getPixel(tex,  0,  0));
	float4 yuv12=rgb2yuv(getPixel(tex,  0, dy));
	float4 yuv20=rgb2yuv(getPixel(tex, dx,-dy));
	float4 yuv21=rgb2yuv(getPixel(tex, dx,  0));
	float4 yuv22=rgb2yuv(getPixel(tex, dx, dy));

	float4 yuv=
		(yuv00*1+yuv01*2+yuv02*1+
		 yuv10*2+yuv11*4+yuv12*2+
		 yuv20*1+yuv21*2+yuv22*1)/16;
	
	yuv.r=yuv11.r;

	return yuv2rgb(yuv);
}