From 5cd8d86eef7cc34485b6a1017a7a666cab629d84 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Thu, 3 Sep 2020 20:48:44 -0400
Subject: [PATCH] Switches to dynamic generation of the 'sharpness' filter,
correcting issues with the Apple II (amongst others).
---
.../Clock Signal/ScanTarget/CSScanTarget.mm | 26 +++++++------------
1 file changed, 10 insertions(+), 16 deletions(-)
diff --git a/OSBindings/Mac/Clock Signal/ScanTarget/CSScanTarget.mm b/OSBindings/Mac/Clock Signal/ScanTarget/CSScanTarget.mm
index b1b404848..84e4bbc6c 100644
--- a/OSBindings/Mac/Clock Signal/ScanTarget/CSScanTarget.mm
+++ b/OSBindings/Mac/Clock Signal/ScanTarget/CSScanTarget.mm
@@ -575,24 +575,20 @@ using BufferingScanTarget = Outputs::Display::BufferingScanTarget;
SignalProcessing::FIRFilter chrominancefilter(15, float(_lineBufferPixelsPerLine), 0.0f, colourCyclesPerLine * 0.01f);
const auto calculatedChromaCoefficients = chrominancefilter.get_coefficients();
for(size_t c = 0; c < 8; ++c) {
- chromaCoefficients[c].y = chromaCoefficients[c].z = calculatedChromaCoefficients[c] * (isSVideoOutput ? 4.0f : 2.0f);
+ chromaCoefficients[c].y = chromaCoefficients[c].z = calculatedChromaCoefficients[c] * (isSVideoOutput ? 4.0f : 3.0f);
chromaCoefficients[c].x = 0.0f;
}
chromaCoefficients[7].x = 1.0f;
// Luminance will be very soft as a result of the separation phase; apply a sharpen filter to try to undo that.
+ // This is applied separately because the first composite processing step is going to select between the nominal
+ // chroma and luma parts to take the place of luminance depending on whether a colour burst was found, and high-pass
+ // filtering the chrominance channel would be visually detrimental.
+ //
+ // The 30 ['Hz' but per line, not per second] is somewhat arbitrary.
if(!isSVideoOutput) {
- constexpr float sharpen[] = {
- 0.0042115543f,
- 0.0f,
- -0.0641804263f,
- -0.252418578f,
- -0.589709163f,
- 0.987914681f,
- 0.627704679f,
- -0.426862389f,
- 0.627704679f
- };
+ SignalProcessing::FIRFilter sharpenFilter(15, float(_lineBufferPixelsPerLine), 20.0f, colourCyclesPerLine);
+ const auto sharpen = sharpenFilter.get_coefficients();
for(size_t c = 0; c < 8; ++c) {
chromaCoefficients[c].x = sharpen[c];
}
@@ -601,11 +597,9 @@ using BufferingScanTarget = Outputs::Display::BufferingScanTarget;
// 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;
- SignalProcessing::FIRFilter lumaPart(15, float(_lineBufferPixelsPerLine), 0.0f, colourCyclesPerLine * 0.75f);
- SignalProcessing::FIRFilter chromaPart(15, float(_lineBufferPixelsPerLine), 0.0f, colourCyclesPerLine * 1.0f);
+ SignalProcessing::FIRFilter lumaPart(15, float(_lineBufferPixelsPerLine), 0.0f, colourCyclesPerLine * 0.6f);
+ SignalProcessing::FIRFilter chromaPart(15, float(_lineBufferPixelsPerLine), 0.0f, colourCyclesPerLine * 1.25f);
const auto lumaCoefficients = lumaPart.get_coefficients();
const auto chromaCoefficients = chromaPart.get_coefficients();