From 8dac6800be952bb48afec48ec2e5c597f7aefae3 Mon Sep 17 00:00:00 2001
From: Ilari Liusvaara <ilari.liusvaara@elisanet.fi>
Date: Thu, 5 Dec 2013 08:46:03 +0200
Subject: [PATCH 3/3] Fix sound DC levels

This was causing popping in Mega Man (I)
---
 libgambatte/src/sound/channel1.cpp | 5 ++---
 libgambatte/src/sound/channel2.cpp | 4 ++--
 libgambatte/src/sound/channel3.cpp | 6 +++---
 libgambatte/src/sound/channel4.cpp | 5 ++---
 4 files changed, 9 insertions(+), 11 deletions(-)

diff --git a/libgambatte/src/sound/channel1.cpp b/libgambatte/src/sound/channel1.cpp
index 6b9ccf1..915ab1a 100644
--- a/libgambatte/src/sound/channel1.cpp
+++ b/libgambatte/src/sound/channel1.cpp
@@ -220,14 +220,13 @@ void Channel1::loadState(const SaveState &state) {
 
 void Channel1::update(uint_least32_t *buf, const unsigned soBaseVol, unsigned cycles) {
 	const unsigned outBase = envelopeUnit.dacIsOn() ? soBaseVol & soMask : 0;
-	const unsigned outLow = outBase * (0 - 15ul);
 	const unsigned endCycles = cycleCounter + cycles;
 	
 	for (;;) {
-		const unsigned outHigh = master ? outBase * (envelopeUnit.getVolume() * 2 - 15ul) : outLow;
+		const unsigned outHigh = master ? outBase * (envelopeUnit.getVolume()) : 0;
+		const unsigned outLow = -outHigh;
 		const unsigned nextMajorEvent = nextEventUnit->getCounter() < endCycles ? nextEventUnit->getCounter() : endCycles;
 		unsigned out = dutyUnit.isHighState() ? outHigh : outLow;
-		
 		while (dutyUnit.getCounter() <= nextMajorEvent) {
 			*buf = out - prevOut;
 			prevOut = out;
diff --git a/libgambatte/src/sound/channel2.cpp b/libgambatte/src/sound/channel2.cpp
index 6bd5b04..dc74d7c 100644
--- a/libgambatte/src/sound/channel2.cpp
+++ b/libgambatte/src/sound/channel2.cpp
@@ -125,11 +125,11 @@ void Channel2::loadState(const SaveState &state) {
 
 void Channel2::update(uint_least32_t *buf, const unsigned soBaseVol, unsigned cycles) {
 	const unsigned outBase = envelopeUnit.dacIsOn() ? soBaseVol & soMask : 0;
-	const unsigned outLow = outBase * (0 - 15ul);
 	const unsigned endCycles = cycleCounter + cycles;
 	
 	for (;;) {
-		const unsigned outHigh = master ? outBase * (envelopeUnit.getVolume() * 2 - 15ul) : outLow;
+		const unsigned outHigh = master ? outBase * (envelopeUnit.getVolume()) : 0;
+		const unsigned outLow = -outHigh;
 		const unsigned nextMajorEvent = nextEventUnit->getCounter() < endCycles ? nextEventUnit->getCounter() : endCycles;
 		unsigned out = dutyUnit.isHighState() ? outHigh : outLow;
 		while (dutyUnit.getCounter() <= nextMajorEvent) {
diff --git a/libgambatte/src/sound/channel3.cpp b/libgambatte/src/sound/channel3.cpp
index ec2c8ed..758f3d5 100644
--- a/libgambatte/src/sound/channel3.cpp
+++ b/libgambatte/src/sound/channel3.cpp
@@ -155,7 +155,7 @@ void Channel3::update(uint_least32_t *buf, const unsigned soBaseVol, unsigned cy
 		
 		for (;;) {
 			const unsigned nextMajorEvent = lengthCounter.getCounter() < endCycles ? lengthCounter.getCounter() : endCycles;
-			unsigned out = outBase * (master ? ((sampleBuf >> (~wavePos << 2 & 4) & 0xF) >> rShift) * 2 - 15ul : 0 - 15ul);
+			unsigned out = outBase * (master ? ((sampleBuf >> (~wavePos << 2 & 4) & 0xF) >> rShift) * 2 - (15 >> rShift) : 0);
 		
 			while (waveCounter <= nextMajorEvent) {
 				*buf += out - prevOut;
@@ -168,7 +168,7 @@ void Channel3::update(uint_least32_t *buf, const unsigned soBaseVol, unsigned cy
 				++wavePos;
 				wavePos &= 0x1F;
 				sampleBuf = waveRam[wavePos >> 1];
-				out = outBase * (/*master ? */((sampleBuf >> (~wavePos << 2 & 4) & 0xF) >> rShift) * 2 - 15ul/* : 0 - 15ul*/);
+				out = outBase * (/*master ? */((sampleBuf >> (~wavePos << 2 & 4) & 0xF) >> rShift) * 2 - (15 >> rShift)/* : 0 - 15ul*/);
 			}
 		
 			if (cycleCounter < nextMajorEvent) {
@@ -184,7 +184,7 @@ void Channel3::update(uint_least32_t *buf, const unsigned soBaseVol, unsigned cy
 				break;
 		}
 	} else {
-		unsigned const out = outBase * (0 - 15ul);
+		unsigned const out = outBase * 0;
 		*buf += out - prevOut;
 		prevOut = out;
 		cycleCounter += cycles;
diff --git a/libgambatte/src/sound/channel4.cpp b/libgambatte/src/sound/channel4.cpp
index b646dff..5132303 100644
--- a/libgambatte/src/sound/channel4.cpp
+++ b/libgambatte/src/sound/channel4.cpp
@@ -264,14 +264,13 @@ void Channel4::loadState(const SaveState &state) {
 
 void Channel4::update(uint_least32_t *buf, const unsigned soBaseVol, unsigned cycles) {
 	const unsigned outBase = envelopeUnit.dacIsOn() ? soBaseVol & soMask : 0;
-	const unsigned outLow = outBase * (0 - 15ul);
 	const unsigned endCycles = cycleCounter + cycles;
 	
 	for (;;) {
-		const unsigned outHigh = /*master ? */outBase * (envelopeUnit.getVolume() * 2 - 15ul)/* : outLow*/;
+		const unsigned outHigh = /*master ? */outBase * (envelopeUnit.getVolume())/* : outLow*/;
+		const unsigned outLow = -outHigh;
 		const unsigned nextMajorEvent = nextEventUnit->getCounter() < endCycles ? nextEventUnit->getCounter() : endCycles;
 		unsigned out = lfsr.isHighState() ? outHigh : outLow;
-		
 		while (lfsr.getCounter() <= nextMajorEvent) {
 			*buf += out - prevOut;
 			prevOut = out;
-- 
1.8.5