From 9efcd9a096841f78767826badc9a44f1bdb6d91e Mon Sep 17 00:00:00 2001
From: refractionpcsx2 <refraction@gmail.com>
Date: Mon, 25 Jan 2021 12:08:39 +0000
Subject: [PATCH] SPU2: Improve SPDIF Bitstream Bypass on Core 0, track MADR

Required for GTA Vice City to work
---
 pcsx2/SPU2/Dma.cpp       |  2 +-
 pcsx2/SPU2/ReadInput.cpp | 31 +++++++++++++++++++++----------
 pcsx2/SPU2/defs.h        |  1 +
 pcsx2/SPU2/spu2sys.cpp   |  4 +++-
 pcsx2/SaveState.h        |  2 +-
 5 files changed, 27 insertions(+), 13 deletions(-)

diff --git a/pcsx2/SPU2/Dma.cpp b/pcsx2/SPU2/Dma.cpp
index fdd727905c..1149eb5d03 100644
--- a/pcsx2/SPU2/Dma.cpp
+++ b/pcsx2/SPU2/Dma.cpp
@@ -133,7 +133,7 @@ void V_Core::AutoDMAReadBuffer(int mode) //mode: 0= split stereo; 1 = do not spl
 
 			if (DMAPtr != nullptr)
 				memcpy(GetMemPtr(0x2000 + (Index << 10) + spos), DMAPtr + InputDataProgress, 0x200);
-			MADR += 0x200;
+			InputDataTransferred += 0x200;
 			InputDataLeft -= 0x100;
 			InputDataProgress += 0x100;
 			leftbuffer = !leftbuffer;
diff --git a/pcsx2/SPU2/ReadInput.cpp b/pcsx2/SPU2/ReadInput.cpp
index ae48b03043..b59db92564 100644
--- a/pcsx2/SPU2/ReadInput.cpp
+++ b/pcsx2/SPU2/ReadInput.cpp
@@ -82,28 +82,39 @@ StereoOut32 V_Core::ReadInput_HiFi()
 StereoOut32 V_Core::ReadInput()
 {
 	StereoOut32 retval;
-
-	if ((Index != 1) || ((PlayMode & 2) == 0))
+	s16 ReadIndex = OutPos;
+	if ((Index == 1) || ((PlayMode & 2) == 0))
 	{
 		for (int i = 0; i < 2; i++)
-			if (Cores[i].IRQEnable && 0x2000 + (Index << 10) + OutPos == (Cores[i].IRQA & 0xfffffdff))
+			if (Cores[i].IRQEnable && 0x2000 + (Index << 10) + ReadIndex == (Cores[i].IRQA & 0xfffffdff))
 				SetIrqCall(i);
 
 		retval = StereoOut32(
-			(s32)(*GetMemPtr(0x2000 + (Index << 10) + OutPos)),
-			(s32)(*GetMemPtr(0x2200 + (Index << 10) + OutPos)));
+			(s32)(*GetMemPtr(0x2000 + (Index << 10) + ReadIndex)),
+			(s32)(*GetMemPtr(0x2200 + (Index << 10) + ReadIndex)));
 	}
 
 #ifdef PCSX2_DEVBUILD
 	DebugCores[Index].admaWaveformL[OutPos % 0x100] = retval.Left;
 	DebugCores[Index].admaWaveformR[OutPos % 0x100] = retval.Right;
 #endif
-	
-	if (OutPos == 0x100 || OutPos == 0x0 || OutPos == 0x80 || OutPos == 0x180)
+
+	// Simulate MADR increase, GTA VC tracks the MADR address for calculating a certain point in the buffer
+	if (InputDataTransferred)
 	{
-		if (OutPos == 0x100)
+		u32 amount = std::min(InputDataTransferred, (u32)0x180);
+		MADR += amount;
+		InputDataTransferred -= amount;
+	}
+
+	if (PlayMode == 2 && Index == 0) //Bitstream bypass refills twice as quickly (GTA VC)
+		ReadIndex = (ReadIndex * 2) & 0x1FF;
+
+	if (ReadIndex == 0x100 || ReadIndex == 0x0 || ReadIndex == 0x80 || ReadIndex == 0x180)
+	{
+		if (ReadIndex == 0x100)
 			InputPosWrite = 0;
-		else if (OutPos == 0)
+		else if (ReadIndex == 0)
 			InputPosWrite = 0x100;
 
 		if (InputDataLeft >= 0x100)
@@ -123,7 +134,7 @@ StereoOut32 V_Core::ReadInput()
 				}
 				
 				InputDataLeft = 0;
-				DMAICounter = 0x200 * 4;
+				DMAICounter = InputDataTransferred * 4;
 				LastClock = *cyclePtr;
 			}
 		}
diff --git a/pcsx2/SPU2/defs.h b/pcsx2/SPU2/defs.h
index 3f43c98a99..9e11fc9d33 100644
--- a/pcsx2/SPU2/defs.h
+++ b/pcsx2/SPU2/defs.h
@@ -406,6 +406,7 @@ struct V_Core
 	s32 DMAICounter;   // DMA Interrupt Counter
 	u32 LastClock;     // DMA Interrupt Clock Cycle Counter
 	u32 InputDataLeft; // Input Buffer
+	u32 InputDataTransferred; // Used for simulating MADR increase (GTA VC)
 	u32 InputPosWrite;
 	u32 InputDataProgress;
 
diff --git a/pcsx2/SPU2/spu2sys.cpp b/pcsx2/SPU2/spu2sys.cpp
index 38a7b9012d..9cb4bed0c4 100644
--- a/pcsx2/SPU2/spu2sys.cpp
+++ b/pcsx2/SPU2/spu2sys.cpp
@@ -134,8 +134,9 @@ void V_Core::Init(int index)
 	NoiseOut = 0;
 	AutoDMACtrl = 0;
 	InputDataLeft = 0;
-	InputPosWrite = 0;
+	InputPosWrite = 0x100;
 	InputDataProgress = 0;
+	InputDataTransferred = 0;
 	ReverbX = 0;
 	LastEffect.Left = 0;
 	LastEffect.Right = 0;
@@ -1530,6 +1531,7 @@ static void __fastcall RegWrite_Core(u16 value)
 				thiscore.AdmaInProgress = 0;
 				thiscore.InputDataLeft = 0;
 				thiscore.DMAICounter = 0;
+				thiscore.InputDataTransferred = 0;
 			}
 			break;
 
diff --git a/pcsx2/SaveState.h b/pcsx2/SaveState.h
index be278e0e9b..52b8cf9b52 100644
--- a/pcsx2/SaveState.h
+++ b/pcsx2/SaveState.h
@@ -24,7 +24,7 @@
 //  the lower 16 bit value.  IF the change is breaking of all compatibility with old
 //  states, increment the upper 16 bit value, and clear the lower 16 bits to 0.
 
-static const u32 g_SaveVersion = (0x9A19 << 16) | 0x0000;
+static const u32 g_SaveVersion = (0x9A1A << 16) | 0x0000;
 
 // this function is meant to be used in the place of GSfreeze, and provides a safe layer
 // between the GS saving function and the MTGS's needs. :)