From 6d76b7cd94e1269cbaa20e61d8315014fdc6054e Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Sun, 17 Feb 2019 21:50:15 -0500
Subject: [PATCH] Attempts to ensure proper colour output during alternating
 PAL lines.

---
 Outputs/OpenGL/ScanTargetGLSLFragments.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Outputs/OpenGL/ScanTargetGLSLFragments.cpp b/Outputs/OpenGL/ScanTargetGLSLFragments.cpp
index 2f8a0da09..fa6b3705c 100644
--- a/Outputs/OpenGL/ScanTargetGLSLFragments.cpp
+++ b/Outputs/OpenGL/ScanTargetGLSLFragments.cpp
@@ -194,7 +194,7 @@ std::string ScanTarget::sampling_function() const {
 
 		case InputDataType::PhaseLinkedLuminance8:
 			fragment_shader +=
-				"uint iPhase = uint((angle * 2.0 / 3.141592654) ) & 3u;";
+				"uint iPhase = uint(step(sign(angle), 0.0) * 3) ^ uint(abs(angle * 2.0 / 3.141592654) ) & 3u;";
 
 			fragment_shader +=
 				is_svideo ?