From 2ec235170ee0adc764f797a10dd717b00e751742 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Thu, 21 Mar 2024 20:43:55 -0400
Subject: [PATCH] Finish the thought on magic constants.

---
 Machines/Acorn/Archimedes/Video.hpp |  4 ++--
 Outputs/CRT/CRT.cpp                 | 14 ++++++++++----
 Outputs/CRT/CRT.hpp                 | 17 ++++++++++++++++-
 3 files changed, 28 insertions(+), 7 deletions(-)

diff --git a/Machines/Acorn/Archimedes/Video.hpp b/Machines/Acorn/Archimedes/Video.hpp
index e227f3f3e..4cd1b0767 100644
--- a/Machines/Acorn/Archimedes/Video.hpp
+++ b/Machines/Acorn/Archimedes/Video.hpp
@@ -222,11 +222,11 @@ private:
 		crt_.set_new_timing(
 			24'000'000 / (divider * 312 * 50),	/* Cycle per line. */
 			312,								/* Height of display. */
-			Outputs::Display::ColourSpace::YIQ,	/* Composite colour space. */
+			Outputs::CRT::PAL::ColourSpace,
 			Outputs::CRT::PAL::ColourCycleNumerator,
 			Outputs::CRT::PAL::ColourCycleDenominator,
 			Outputs::CRT::PAL::VerticalSyncLength,
-			true);
+			Outputs::CRT::PAL::AlternatesPhase);
 	}
 };
 
diff --git a/Outputs/CRT/CRT.cpp b/Outputs/CRT/CRT.cpp
index b6b0fb0ba..beb60f391 100644
--- a/Outputs/CRT/CRT.cpp
+++ b/Outputs/CRT/CRT.cpp
@@ -120,17 +120,23 @@ void CRT::set_new_display_type(int cycles_per_line, Outputs::Display::Type displ
 			set_new_timing(
 				cycles_per_line,
 				(displayType == Outputs::Display::Type::PAL50) ? 312 : 262,
-				Outputs::Display::ColourSpace::YUV,
+				PAL::ColourSpace,
 				PAL::ColourCycleNumerator,
 				PAL::ColourCycleDenominator,
 				PAL::VerticalSyncLength,
-				true);
-					// i.e. 283.7516 colour cycles per line; 2.5 lines = vertical sync.
+				PAL::AlternatesPhase);
 		break;
 
 		case Outputs::Display::Type::NTSC60:
 			scan_target_modals_.intended_gamma = 2.2f;
-			set_new_timing(cycles_per_line, 262, Outputs::Display::ColourSpace::YIQ, 455, 2, 6, false);			// i.e. 227.5 colour cycles per line, 3 lines = vertical sync.
+			set_new_timing(
+				cycles_per_line,
+				262,
+				NTSC::ColourSpace,
+				NTSC::ColourCycleNumerator,
+				NTSC::ColourCycleDenominator,
+				NTSC::VerticalSyncLength,
+				NTSC::AlternatesPhase);
 		break;
 	}
 }
diff --git a/Outputs/CRT/CRT.hpp b/Outputs/CRT/CRT.hpp
index bd1bc1b6c..eb69fa3ff 100644
--- a/Outputs/CRT/CRT.hpp
+++ b/Outputs/CRT/CRT.hpp
@@ -20,11 +20,26 @@ namespace Outputs::CRT {
 
 namespace PAL {
 
-// PAL: 283.7516 colour cycles per line; 2.5 lines = vertical sync.
+// 283.7516 colour cycles per line; 2.5 lines of vertical sync.
 static constexpr int ColourCycleNumerator = 709379;
 static constexpr int ColourCycleDenominator = 2500;
 static constexpr int VerticalSyncLength = 5;
 
+static constexpr auto ColourSpace = Outputs::Display::ColourSpace::YUV;
+static constexpr bool AlternatesPhase = true;
+
+}
+
+namespace NTSC {
+
+// 227.5 colour cycles per line; 3 lines of vertical sync.
+static constexpr int ColourCycleNumerator = 455;
+static constexpr int ColourCycleDenominator = 2;
+static constexpr int VerticalSyncLength = 6;
+
+static constexpr auto ColourSpace = Outputs::Display::ColourSpace::YIQ;
+static constexpr bool AlternatesPhase = false;
+
 }
 
 class CRT;