float3 safeNormalize(float3 value)
{
	float len = max(length(value), 0.0001);
	return value / len;
}

float luma709(float3 color)
{
	return dot(color, float3(0.2126, 0.7152, 0.0722));
}

float4 shadeVideo(ShaderContext context)
{
	float4 src = context.sourceColor;
	float3 color = saturate(src.rgb);

	float3 keyColor = safeNormalize(max(screenColor.rgb, float3(0.0001, 0.0001, 0.0001)));
	float3 sampleColor = safeNormalize(max(color, float3(0.0001, 0.0001, 0.0001)));

	float chromaDistance = length(sampleColor - keyColor);
	float matteCenter = threshold - erodeDilate;
	float matteFeather = max(softness + edgeSoftness, 0.0005);
	float alpha = smoothstep(matteCenter - matteFeather, matteCenter + matteFeather, chromaDistance);

	alpha = saturate((alpha - clipBlack) / max(clipWhite - clipBlack, 0.0001));
	alpha = saturate(alpha + edgeBoost);

	float greenExcess = max(0.0, color.g - max(color.r, color.b));
	float spillReduction = greenExcess * despill;

	float3 despilled = color;
	despilled.g = max(0.0, despilled.g - spillReduction);

	float neutral = luma709(despilled);
	despilled.rb += spillReduction * 0.25;
	despilled = lerp(float3(neutral, neutral, neutral), despilled, 0.92);

	float3 premultiplied = saturate(despilled) * alpha;
	return float4(premultiplied, alpha);
}