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Fixes non-RGB colour composite generation.

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The hard-coded sharpen filter proves to be a really bad fit for the Apple II though.
This commit is contained in:
Thomas Harte 2020-09-03 19:04:17 -04:00
parent 0288a1974b
commit 74d0acdaec
2 changed files with 48 additions and 54 deletions
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4
OSBindings/Mac/Clock Signal/ScanTarget/CSScanTarget.mm
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@ -604,8 +604,8 @@ using BufferingScanTarget = Outputs::Display::BufferingScanTarget;
// TODO: support separate high-low filters for chroma and luma, rather than treating that as purely subtractive.
auto *const luminanceCoefficients = uniforms()->lumaCoefficients;
SignalProcessing::FIRFilter lumaPart(15, float(_lineBufferPixelsPerLine), 0.0f, colourCyclesPerLine * 0.5f);
SignalProcessing::FIRFilter chromaPart(15, float(_lineBufferPixelsPerLine), 0.0f, colourCyclesPerLine * 1.1f);
SignalProcessing::FIRFilter lumaPart(15, float(_lineBufferPixelsPerLine), 0.0f, colourCyclesPerLine * 0.75f);
SignalProcessing::FIRFilter chromaPart(15, float(_lineBufferPixelsPerLine), 0.0f, colourCyclesPerLine * 1.0f);
const auto lumaCoefficients = lumaPart.get_coefficients();
const auto chromaCoefficients = chromaPart.get_coefficients();

98
OSBindings/Mac/Clock Signal/ScanTarget/ScanTarget.metal
View File

@ -96,6 +96,11 @@ struct SourceInterpolator {
float colourAmplitude [[flat]];
};
struct CopyInterpolator {
float4 position [[position]];
float2 textureCoordinates;
};
// MARK: - Vertex shaders.
float2 textureLocation(constant Line *line, float offset, constant Uniforms &uniforms) {
@ -210,6 +215,25 @@ vertex SourceInterpolator scanToComposition( constant Uniforms &uniforms [[buffe
return result;
}
vertex CopyInterpolator copyVertex(uint vertexID [[vertex_id]], texture2d<float> texture [[texture(0)]]) {
CopyInterpolator vert;
const uint x = vertexID & 1;
const uint y = (vertexID >> 1) & 1;
vert.textureCoordinates = float2(
x * texture.get_width(),
y * texture.get_height()
);
vert.position = float4(
float(x) * 2.0 - 1.0,
1.0 - float(y) * 2.0,
0.0,
1.0
);
return vert;
}
// MARK: - Various input format conversion samplers.
@ -217,20 +241,28 @@ float2 quadrature(float phase) {
return float2(cos(phase), sin(phase));
}
float4 composite(float level, float2 quadrature, float amplitude) {
return float4(
level,
float2(0.5f) + quadrature*0.5f,
amplitude
);
}
// There's only one meaningful way to sample the luminance formats.
fragment float4 sampleLuminance1(SourceInterpolator vert [[stage_in]], texture2d<ushort> texture [[texture(0)]]) {
return float4(float3(texture.sample(standardSampler, vert.textureCoordinates).r), 1.0);
return composite(texture.sample(standardSampler, vert.textureCoordinates).r, quadrature(vert.colourPhase), vert.colourAmplitude);
}
fragment float4 sampleLuminance8(SourceInterpolator vert [[stage_in]], texture2d<float> texture [[texture(0)]]) {
return float4(float3(texture.sample(standardSampler, vert.textureCoordinates).r), 1.0);
return composite(texture.sample(standardSampler, vert.textureCoordinates).r, quadrature(vert.colourPhase), vert.colourAmplitude);
}
fragment float4 samplePhaseLinkedLuminance8(SourceInterpolator vert [[stage_in]], texture2d<float> texture [[texture(0)]]) {
const int offset = int(vert.colourPhase * 4.0);
auto sample = texture.sample(standardSampler, vert.textureCoordinates);
return float4(float3(sample[offset]), 1.0);
return composite(sample[offset], quadrature(vert.colourPhase), vert.colourAmplitude);
}
// The luminance/phase format can produce either composite or S-Video.
@ -254,12 +286,7 @@ fragment float4 sampleLuminance8Phase8(SourceInterpolator vert [[stage_in]], tex
fragment float4 compositeSampleLuminance8Phase8(SourceInterpolator vert [[stage_in]], texture2d<float> texture [[texture(0)]]) {
const float2 luminanceChroma = convertLuminance8Phase8(vert, texture);
const float level = mix(luminanceChroma.r, luminanceChroma.g, vert.colourAmplitude);
return float4(
level,
0.5 + 0.5*level*cos(vert.colourPhase),
0.5 + 0.5*level*sin(vert.colourPhase),
1.0
);
return composite(level, quadrature(vert.colourPhase), vert.colourAmplitude);
}
// All the RGB formats can produce RGB, composite or S-Video.
@ -309,11 +336,7 @@ float3 convertRed1Green1Blue1(SourceInterpolator vert, texture2d<ushort> texture
const auto colour = uniforms.fromRGB * clamp(convert##name(vert, texture), float3(0.0f), float3(1.0f)); \
const float2 colourSubcarrier = quadrature(vert.colourPhase); \
const float level = mix(colour.r, dot(colour.gb, colourSubcarrier), vert.colourAmplitude); \
return float4( \
level, \
float2(0.5f) + quadrature(vert.colourPhase)*0.5f, \
vert.colourPhase \
); \
return composite(level, colourSubcarrier, vert.colourAmplitude); \
}
DeclareShaders(Red8Green8Blue8, float)
@ -321,48 +344,19 @@ DeclareShaders(Red4Green4Blue4, ushort)
DeclareShaders(Red2Green2Blue2, ushort)
DeclareShaders(Red1Green1Blue1, ushort)
// MARK: - Shaders for copying from a same-sized texture to an MTKView's frame buffer.
struct CopyInterpolator {
float4 position [[position]];
float2 textureCoordinates;
};
vertex CopyInterpolator copyVertex(uint vertexID [[vertex_id]], texture2d<float> texture [[texture(0)]]) {
CopyInterpolator vert;
const uint x = vertexID & 1;
const uint y = (vertexID >> 1) & 1;
vert.textureCoordinates = float2(
x * texture.get_width(),
y * texture.get_height()
);
vert.position = float4(
float(x) * 2.0 - 1.0,
1.0 - float(y) * 2.0,
0.0,
1.0
);
return vert;
}
fragment float4 copyFragment(CopyInterpolator vert [[stage_in]], texture2d<float> texture [[texture(0)]]) {
return texture.sample(standardSampler, vert.textureCoordinates);
}
fragment float4 interpolateFragment(CopyInterpolator vert [[stage_in]], texture2d<float> texture [[texture(0)]]) {
return texture.sample(linearSampler, vert.textureCoordinates);
}
fragment float4 clearFragment() {
return float4(0.0, 0.0, 0.0, 0.64);
}
// MARK: -
fragment float4 interpolateFragment(CopyInterpolator vert [[stage_in]], texture2d<float> texture [[texture(0)]]) {
return texture.sample(linearSampler, vert.textureCoordinates);
}
// MARK: - Kernel functions
// MARK: - Compute kernels
/// Given input pixels of the form (luminance, 0.5 + 0.5*chrominance*cos(phase), 0.5 + 0.5*chrominance*sin(phase)), applies a lowpass
/// filter to the two chrominance parts, then uses the toRGB matrix to convert to RGB and stores.
@ -441,11 +435,11 @@ kernel void separateLumaKernel( texture2d<float, access::read> inTexture [[textu
Sample(8, 6) + Sample(9, 5) + Sample(10, 4) + Sample(11, 3) + Sample(12, 2) + Sample(13, 1) + Sample(14, 0);
#undef Sample
// TODO: determine why centreSample.a doesn't seem to be giving the real composite amplitude, and stop
// hard-coding 0.15f and 7.0f below.
// The mix/steps below ensures that the absence of a colour burst leads the colour subcarrier to be discarded.
const float isColour = step(0.01, centreSample.a);
outTexture.write(float4(
luminance.r / (1.0f - 0.15f),
(centreSample.gb - float2(0.5f)) * (centreSample.r - luminance.g) * 28.0f + float2(0.5f),
mix(luminance.g, luminance.r / (1.0f - centreSample.a), isColour),
isColour * (centreSample.gb - float2(0.5f)) * (centreSample.r - luminance.g) / mix(1.0f, centreSample.a, isColour) + float2(0.5f),
1.0f
),
gid + uint2(7, offset));