From f42a585feecbed89d1d3ff6cdd0d51dfdb41a6b9 Mon Sep 17 00:00:00 2001
From: zeromus <zeromus@users.noreply.github.com>
Date: Wed, 23 Sep 2015 20:28:38 -0500
Subject: [PATCH] snes - handle interlaced modes differently

---
 .../Consoles/Nintendo/SNES/LibsnesCore.cs     | 20 +++++++++----------
 1 file changed, 9 insertions(+), 11 deletions(-)

diff --git a/BizHawk.Emulation.Cores/Consoles/Nintendo/SNES/LibsnesCore.cs b/BizHawk.Emulation.Cores/Consoles/Nintendo/SNES/LibsnesCore.cs
index 15e132c525..aeac5f6022 100644
--- a/BizHawk.Emulation.Cores/Consoles/Nintendo/SNES/LibsnesCore.cs
+++ b/BizHawk.Emulation.Cores/Consoles/Nintendo/SNES/LibsnesCore.cs
@@ -1,4 +1,4 @@
-//TODO - add serializer, add interlace field variable to serializer
+//TODO - add serializer (?)
 
 //http://wiki.superfamicom.org/snes/show/Backgrounds
 
@@ -502,7 +502,6 @@ namespace BizHawk.Emulation.Cores.Nintendo.SNES
 			IsLagFrame = false;
 		}
 
-		int field = 0;
 		void snes_video_refresh(int* data, int width, int height)
 		{
 			bool doubleSize = Settings.AlwaysDoubleSize;
@@ -514,7 +513,6 @@ namespace BizHawk.Emulation.Cores.Nintendo.SNES
 			int yskip = 1, xskip = 1;
 
 			//if we are in high-res mode, we get double width. so, lets double the height here to keep it square.
-			//TODO - does interlacing have something to do with the correct way to handle this? need an example that turns it on.
 			if (width == 512)
 			{
 				vidHeight *= 2;
@@ -533,18 +531,18 @@ namespace BizHawk.Emulation.Cores.Nintendo.SNES
 			int srcPitch = 1024;
 			int srcStart = 0;
 
-			//for interlaced mode, we're gonna alternate fields. you know, like we're supposed to
 			bool interlaced = (height == 478 || height == 448);
 			if (interlaced)
 			{
-				srcPitch = 1024;
-				if (field == 1)
-					srcStart = 512; //start on second field
-				//really only half as high as the video output
+				//from bsnes in interlaced mode we have each field side by side
+				//so we will come in with a dimension of 512x448, say
+				//but the fields are side by side, so it's actually 1024x224.
+				//copy the first scanline from row 0, then the 2nd scanline from row 0 (offset 512)
+				//EXAMPLE: yu yu hakushu legal screens
+				lineDouble = false;
+				srcPitch = 512;
+				yskip = 1;
 				vidHeight /= 2;
-				height /= 2;
-				//alternate fields
-				field ^= 1;
 			}
 
 			if (dotDouble)