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Tries: separate filters for chroma and luma, plus a post-separation sharpen filter on the latter.

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This commit is contained in:
Thomas Harte 2020-09-03 13:18:21 -04:00
parent 6efd8782fe
commit 0288a1974b
2 changed files with 45 additions and 29 deletions
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34
OSBindings/Mac/Clock Signal/ScanTarget/CSScanTarget.mm
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@ -99,7 +99,7 @@ struct Uniforms {
float zoom; float zoom;
simd::float2 offset; simd::float2 offset;
simd::float3 chromaCoefficients[8]; simd::float3 chromaCoefficients[8];
float lumaCoefficients[8]; simd::float2 lumaCoefficients[8];
float radiansPerPixel; float radiansPerPixel;
float cyclesMultiplier; float cyclesMultiplier;
}; };
@ -580,23 +580,39 @@ using BufferingScanTarget = Outputs::Display::BufferingScanTarget;
} }
chromaCoefficients[7].x = 1.0f; chromaCoefficients[7].x = 1.0f;
// Luminance is under-filtered during the separation phase in order not to subtract too much from chrominance; // Luminance will be very soft as a result of the separation phase; apply a sharpen filter to try to undo that.
// therefore an additional filtering is applied here.
if(!isSVideoOutput) { if(!isSVideoOutput) {
SignalProcessing::FIRFilter luminancefilter(15, float(_lineBufferPixelsPerLine), 0.0f, colourCyclesPerLine * 0.8f); constexpr float sharpen[] = {
const auto calculatedLumaCoefficients = luminancefilter.get_coefficients(); 0.0042115543f,
0.0f,
-0.0641804263f,
-0.252418578f,
-0.589709163f,
0.987914681f,
0.627704679f,
-0.426862389f,
0.627704679f
};
for(size_t c = 0; c < 8; ++c) { for(size_t c = 0; c < 8; ++c) {
chromaCoefficients[c].x = calculatedLumaCoefficients[c]; chromaCoefficients[c].x = sharpen[c];
} }
} }
} }
// Generate the luminance separation filter. // Generate the luminance separation filter.
{ {
// TODO: support separate high-low filters for chroma and luma, rather than treating that as purely subtractive.
auto *const luminanceCoefficients = uniforms()->lumaCoefficients; auto *const luminanceCoefficients = uniforms()->lumaCoefficients;
SignalProcessing::FIRFilter luminancefilter(15, float(_lineBufferPixelsPerLine), 0.0f, colourCyclesPerLine); SignalProcessing::FIRFilter lumaPart(15, float(_lineBufferPixelsPerLine), 0.0f, colourCyclesPerLine * 0.5f);
const auto calculatedCoefficients = luminancefilter.get_coefficients(); SignalProcessing::FIRFilter chromaPart(15, float(_lineBufferPixelsPerLine), 0.0f, colourCyclesPerLine * 1.1f);
memcpy(luminanceCoefficients, calculatedCoefficients.data(), sizeof(float)*8);
const auto lumaCoefficients = lumaPart.get_coefficients();
const auto chromaCoefficients = chromaPart.get_coefficients();
for(size_t c = 0; c < 8; ++c) {
luminanceCoefficients[c].x = lumaCoefficients[c];
luminanceCoefficients[c].y = chromaCoefficients[c];
}
} }
// Store radians per pixel. TODO: is this now orphaned? Should I keep it anyway? // Store radians per pixel. TODO: is this now orphaned? Should I keep it anyway?

40
OSBindings/Mac/Clock Signal/ScanTarget/ScanTarget.metal
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@ -38,7 +38,7 @@ struct Uniforms {
// Describes the FIR filter in use for luma filtering; also 15 coefficients // Describes the FIR filter in use for luma filtering; also 15 coefficients
// symmetrical around the centre. // symmetrical around the centre.
float lumaCoefficients[8]; float2 lumaCoefficients[8];
// Maps from pixel offsets into the composition buffer to angular difference. // Maps from pixel offsets into the composition buffer to angular difference.
float radiansPerPixel; float radiansPerPixel;
@ -416,26 +416,26 @@ kernel void separateLumaKernel( texture2d<float, access::read> inTexture [[textu
constant Uniforms &uniforms [[buffer(0)]], constant Uniforms &uniforms [[buffer(0)]],
constant int &offset [[buffer(1)]]) { constant int &offset [[buffer(1)]]) {
const float4 centreSample = inTexture.read(gid + uint2(7, offset)); const float4 centreSample = inTexture.read(gid + uint2(7, offset));
const float rawSamples[] = { const float2 rawSamples[] = {
inTexture.read(gid + uint2(0, offset)).r, inTexture.read(gid + uint2(0, offset)).rr,
inTexture.read(gid + uint2(1, offset)).r, inTexture.read(gid + uint2(1, offset)).rr,
inTexture.read(gid + uint2(2, offset)).r, inTexture.read(gid + uint2(2, offset)).rr,
inTexture.read(gid + uint2(3, offset)).r, inTexture.read(gid + uint2(3, offset)).rr,
inTexture.read(gid + uint2(4, offset)).r, inTexture.read(gid + uint2(4, offset)).rr,
inTexture.read(gid + uint2(5, offset)).r, inTexture.read(gid + uint2(5, offset)).rr,
inTexture.read(gid + uint2(6, offset)).r, inTexture.read(gid + uint2(6, offset)).rr,
centreSample.r, centreSample.rr,
inTexture.read(gid + uint2(8, offset)).r, inTexture.read(gid + uint2(8, offset)).rr,
inTexture.read(gid + uint2(9, offset)).r, inTexture.read(gid + uint2(9, offset)).rr,
inTexture.read(gid + uint2(10, offset)).r, inTexture.read(gid + uint2(10, offset)).rr,
inTexture.read(gid + uint2(11, offset)).r, inTexture.read(gid + uint2(11, offset)).rr,
inTexture.read(gid + uint2(12, offset)).r, inTexture.read(gid + uint2(12, offset)).rr,
inTexture.read(gid + uint2(13, offset)).r, inTexture.read(gid + uint2(13, offset)).rr,
inTexture.read(gid + uint2(14, offset)).r, inTexture.read(gid + uint2(14, offset)).rr,
}; };
#define Sample(x, y) uniforms.lumaCoefficients[y] * rawSamples[x] #define Sample(x, y) uniforms.lumaCoefficients[y] * rawSamples[x]
const float luminance = const float2 luminance =
Sample(0, 0) + Sample(1, 1) + Sample(2, 2) + Sample(3, 3) + Sample(4, 4) + Sample(5, 5) + Sample(6, 6) + Sample(0, 0) + Sample(1, 1) + Sample(2, 2) + Sample(3, 3) + Sample(4, 4) + Sample(5, 5) + Sample(6, 6) +
Sample(7, 7) + Sample(7, 7) +
Sample(8, 6) + Sample(9, 5) + Sample(10, 4) + Sample(11, 3) + Sample(12, 2) + Sample(13, 1) + Sample(14, 0); Sample(8, 6) + Sample(9, 5) + Sample(10, 4) + Sample(11, 3) + Sample(12, 2) + Sample(13, 1) + Sample(14, 0);
@ -444,8 +444,8 @@ kernel void separateLumaKernel( texture2d<float, access::read> inTexture [[textu
// TODO: determine why centreSample.a doesn't seem to be giving the real composite amplitude, and stop // 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. // hard-coding 0.15f and 7.0f below.
outTexture.write(float4( outTexture.write(float4(
luminance / (1.0f - 0.15f), luminance.r / (1.0f - 0.15f),
(centreSample.gb - float2(0.5f)) * (centreSample.r - luminance) * 28.0f + float2(0.5f), (centreSample.gb - float2(0.5f)) * (centreSample.r - luminance.g) * 28.0f + float2(0.5f),
1.0f 1.0f
), ),
gid + uint2(7, offset)); gid + uint2(7, offset));