From 607d3e252c43d67cea54ec222ef1767a86b3660b Mon Sep 17 00:00:00 2001
From: Ilari Liusvaara <ilari.liusvaara@elisanet.fi>
Date: Thu, 5 Dec 2013 08:48:21 +0200
Subject: [PATCH 4/9] Fix sound DC levels

This was causing popping in Mega Man (I)
---
 libgambatte/src/sound/channel1.cpp | 6 +++---
 libgambatte/src/sound/channel2.cpp | 6 +++---
 libgambatte/src/sound/channel3.cpp | 8 ++++----
 libgambatte/src/sound/channel4.cpp | 4 ++--
 4 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/libgambatte/src/sound/channel1.cpp b/libgambatte/src/sound/channel1.cpp
index c517965..dd83894 100644
--- a/libgambatte/src/sound/channel1.cpp
+++ b/libgambatte/src/sound/channel1.cpp
@@ -218,13 +218,13 @@ void Channel1::loadState(SaveState const &state) {
 
 void Channel1::update(uint_least32_t *buf, unsigned const soBaseVol, unsigned cycles) {
 	unsigned const outBase = envelopeUnit_.dacIsOn() ? soBaseVol & soMask_ : 0;
-	unsigned const outLow = outBase * (0 - 15ul);
 	unsigned const endCycles = cycleCounter_ + cycles;
 
 	for (;;) {
 		unsigned const outHigh = master_
-		                            ? outBase * (envelopeUnit_.getVolume() * 2 - 15ul)
-		                            : outLow;
+		                            ? outBase * (envelopeUnit_.getVolume())
+		                            : 0;
+		unsigned const outLow = -outHigh;
 		unsigned const nextMajorEvent = std::min(nextEventUnit_->counter(), endCycles);
 		unsigned out = dutyUnit_.isHighState() ? outHigh : outLow;
 
diff --git a/libgambatte/src/sound/channel2.cpp b/libgambatte/src/sound/channel2.cpp
index f154249..6024d79 100644
--- a/libgambatte/src/sound/channel2.cpp
+++ b/libgambatte/src/sound/channel2.cpp
@@ -122,13 +122,13 @@ void Channel2::loadState(SaveState const &state) {
 
 void Channel2::update(uint_least32_t *buf, unsigned const soBaseVol, unsigned cycles) {
 	unsigned const outBase = envelopeUnit_.dacIsOn() ? soBaseVol & soMask_ : 0;
-	unsigned const outLow = outBase * (0 - 15ul);
 	unsigned const endCycles = cycleCounter_ + cycles;
 
 	for (;;) {
 		unsigned const outHigh = master_
-		                            ? outBase * (envelopeUnit_.getVolume() * 2 - 15ul)
-		                            : outLow;
+		                            ? outBase * (envelopeUnit_.getVolume())
+		                            : 0;
+		unsigned const outLow = -outHigh;
 		unsigned const nextMajorEvent = std::min(nextEventUnit->counter(), endCycles);
 		unsigned out = dutyUnit_.isHighState() ? outHigh : outLow;
 
diff --git a/libgambatte/src/sound/channel3.cpp b/libgambatte/src/sound/channel3.cpp
index c583949..f25c96d 100644
--- a/libgambatte/src/sound/channel3.cpp
+++ b/libgambatte/src/sound/channel3.cpp
@@ -156,8 +156,8 @@ void Channel3::update(uint_least32_t *buf, unsigned const soBaseVol, unsigned cy
 			unsigned const nextMajorEvent =
 				std::min(lengthCounter_.counter(), endCycles);
 			unsigned out = master_
-				? ((sampleBuf_ >> (~wavePos_ << 2 & 4) & 0xF) >> rshift_) * 2 - 15ul
-				: 0 - 15ul;
+				? ((sampleBuf_ >> (~wavePos_ << 2 & 4) & 0xF) >> rshift_) * 2 - (15 >> rshift_)
+				: 0;
 			out *= outBase;
 
 			while (waveCounter_ <= nextMajorEvent) {
@@ -171,7 +171,7 @@ void Channel3::update(uint_least32_t *buf, unsigned const soBaseVol, unsigned cy
 				++wavePos_;
 				wavePos_ &= 0x1F;
 				sampleBuf_ = waveRam_[wavePos_ >> 1];
-				out = ((sampleBuf_ >> (~wavePos_ << 2 & 4) & 0xF) >> rshift_) * 2 - 15ul;
+				out = ((sampleBuf_ >> (~wavePos_ << 2 & 4) & 0xF) >> rshift_) * 2 - (15 >> rshift_);
 				out *= outBase;
 			}
 
@@ -188,7 +188,7 @@ void Channel3::update(uint_least32_t *buf, unsigned const soBaseVol, unsigned cy
 				break;
 		}
 	} else {
-		unsigned const out = outBase * (0 - 15ul);
+		unsigned const out = 0;
 		*buf += out - prevOut_;
 		prevOut_ = out;
 		cycleCounter_ += cycles;
diff --git a/libgambatte/src/sound/channel4.cpp b/libgambatte/src/sound/channel4.cpp
index bc0a312..0abd4fb 100644
--- a/libgambatte/src/sound/channel4.cpp
+++ b/libgambatte/src/sound/channel4.cpp
@@ -224,11 +224,11 @@ void Channel4::loadState(SaveState const &state) {
 
 void Channel4::update(uint_least32_t *buf, unsigned const soBaseVol, unsigned cycles) {
 	unsigned const outBase = envelopeUnit_.dacIsOn() ? soBaseVol & soMask_ : 0;
-	unsigned const outLow = outBase * (0 - 15ul);
 	unsigned const endCycles = cycleCounter_ + cycles;
 
 	for (;;) {
-		unsigned const outHigh = outBase * (envelopeUnit_.getVolume() * 2 - 15ul);
+		unsigned const outHigh = outBase * (envelopeUnit_.getVolume());
+		unsigned const outLow = -outHigh;
 		unsigned const nextMajorEvent = std::min(nextEventUnit_->counter(), endCycles);
 		unsigned out = lfsr_.isHighState() ? outHigh : outLow;
 
-- 
2.1.3