From 4f5c6cbbb5db7b31fa154d48189858ceeb20d539 Mon Sep 17 00:00:00 2001
From: tildearrow <me@tildearrow.org>
Date: Mon, 9 Sep 2024 19:28:16 -0500
Subject: [PATCH] SoundUnit: emulation changes

no longer uses int for the filter stages, instead using short
this makes a 1982 design cheaper and more viable
---
 src/engine/platform/sound/su.cpp | 11 ++++++-----
 src/engine/platform/sound/su.h   | 12 ++++++------
 2 files changed, 12 insertions(+), 11 deletions(-)

diff --git a/src/engine/platform/sound/su.cpp b/src/engine/platform/sound/su.cpp
index 8d5373cef..505a0d48b 100644
--- a/src/engine/platform/sound/su.cpp
+++ b/src/engine/platform/sound/su.cpp
@@ -146,7 +146,8 @@ void SoundUnit::NextSample(short* l, short* r) {
         }
       }
     }
-    fns[i]=ns[i]*chan[i].vol*((chan[i].flags0&8)?4:2);
+    fns[i]=ns[i]*chan[i].vol;
+    if (!(chan[i].flags0&8)) fns[i]>>=1;
     if ((chan[i].flags0&0xe0)!=0) {
       int ff=chan[i].cutoff;
       nslow[i]=nslow[i]+(((ff)*nsband[i])>>16);
@@ -259,12 +260,12 @@ void SoundUnit::NextSample(short* l, short* r) {
 
   // mix
   if (dsOut) {
-    tnsL=nsL[dsChannel]<<1;
-    tnsR=nsR[dsChannel]<<1;
+    tnsL=nsL[dsChannel]<<3;
+    tnsR=nsR[dsChannel]<<3;
     dsChannel=(dsChannel+1)&7;
   } else {
-    tnsL=(nsL[0]+nsL[1]+nsL[2]+nsL[3]+nsL[4]+nsL[5]+nsL[6]+nsL[7])>>2;
-    tnsR=(nsR[0]+nsR[1]+nsR[2]+nsR[3]+nsR[4]+nsR[5]+nsR[6]+nsR[7])>>2;
+    tnsL=(nsL[0]+nsL[1]+nsL[2]+nsL[3]+nsL[4]+nsL[5]+nsL[6]+nsL[7]);
+    tnsR=(nsR[0]+nsR[1]+nsR[2]+nsR[3]+nsR[4]+nsR[5]+nsR[6]+nsR[7]);
 
     IL1=minval(32767,maxval(-32767,tnsL))>>8;
     IL2=minval(32767,maxval(-32767,tnsR))>>8;
diff --git a/src/engine/platform/sound/su.h b/src/engine/platform/sound/su.h
index 8e8009568..091f7de73 100644
--- a/src/engine/platform/sound/su.h
+++ b/src/engine/platform/sound/su.h
@@ -33,12 +33,12 @@ class SoundUnit {
   int rcycle[8];
   unsigned int lfsr[8];
   signed char ns[8];
-  int fns[8];
-  int nsL[8];
-  int nsR[8];
-  int nslow[8];
-  int nshigh[8];
-  int nsband[8];
+  short fns[8];
+  short nsL[8];
+  short nsR[8];
+  short nslow[8];
+  short nshigh[8];
+  short nsband[8];
   int tnsL, tnsR;
   unsigned char ilBufPeriod;
   unsigned short ilBufPos;