From aad5d818f26aee716cdfcf9ff98b0c6aa3cd717e Mon Sep 17 00:00:00 2001
From: tildearrow <tildearrow@protonmail.com>
Date: Tue, 10 May 2022 16:22:40 -0500
Subject: [PATCH] YM2612: early full linear pitch experiment

u n t e s t e d
---
 src/engine/engine.cpp           | 71 +++++++++++++++++++--------------
 src/engine/engine.h             |  2 +-
 src/engine/platform/genesis.cpp |  5 ++-
 3 files changed, 44 insertions(+), 34 deletions(-)

diff --git a/src/engine/engine.cpp b/src/engine/engine.cpp
index 83bc56b8..7465c885 100644
--- a/src/engine/engine.cpp
+++ b/src/engine/engine.cpp
@@ -995,46 +995,55 @@ double DivEngine::calcBaseFreq(double clock, double divider, int note, bool peri
          base*(divider/clock);
 }
 
+#define CONVERT_FNUM_BLOCK(bf,bits,note) \
+  double tuning=song.tuning; \
+  if (tuning<400.0) tuning=400.0; \
+  if (tuning>500.0) tuning=500.0; \
+  int boundaryBottom=tuning*pow(2.0,0.25)*(divider/clock); \
+  int boundaryTop=2.0*tuning*pow(2.0,0.25)*(divider/clock); \
+  int block=(note)/12; \
+  if (block<0) block=0; \
+  if (block>7) block=7; \
+  bf>>=block; \
+  if (bf<0) bf=0; \
+  /* octave boundaries */ \
+  while (bf>0 && bf<boundaryBottom && block>0) { \
+    bf<<=1; \
+    block--; \
+  } \
+  if (bf>boundaryTop) { \
+    while (block<7 && bf>boundaryTop) { \
+      bf>>=1; \
+      block++; \
+    } \
+    if (bf>((1<<bits)-1)) { \
+      bf=(1<<bits)-1; \
+    } \
+  } \
+  /* logV("f-num: %d block: %d",bf,block); */ \
+  return bf|(block<<bits);
+
 unsigned short DivEngine::calcBaseFreqFNumBlock(double clock, double divider, int note, int bits) {
   if (song.linearPitch==2) { // full linear
     return (note<<7);
   }
-  double tuning=song.tuning;
-  if (tuning<400.0) tuning=400.0;
-  if (tuning>500.0) tuning=500.0;
   int bf=calcBaseFreq(clock,divider,note,false);
-  int boundaryBottom=tuning*pow(2.0,0.25)*(divider/clock);
-  int boundaryTop=2.0*tuning*pow(2.0,0.25)*(divider/clock);
-  int block=note/12;
-  if (block<0) block=0;
-  if (block>7) block=7;
-  bf>>=block;
-  if (bf<0) bf=0;
-  // octave boundaries
-  while (bf>0 && bf<boundaryBottom && block>0) {
-    bf<<=1;
-    block--;
-  }
-  if (bf>boundaryTop) {
-    while (block<7 && bf>boundaryTop) {
-      bf>>=1;
-      block++;
-    }
-    if (bf>((1<<bits)-1)) {
-      bf=(1<<bits)-1;
-    }
-  }
-  //logV("f-num: %d block: %d",bf,block);
-  return bf|(block<<bits);
+  CONVERT_FNUM_BLOCK(bf,bits,note)
 }
 
-int DivEngine::calcFreq(int base, int pitch, bool period, int octave, int pitch2, double clock, double divider) {
+int DivEngine::calcFreq(int base, int pitch, bool period, int octave, int pitch2, double clock, double divider, int blockBits) {
   if (song.linearPitch==2) {
     // do frequency calculation here
-    double fbase=(period?(song.tuning*0.0625):song.tuning)*pow(2.0,(float)(base+pitch+384)/(128.0*12.0));
-    return period?
-          (clock/fbase)/divider:
-          fbase*(divider/clock);
+    int nbase=base+pitch+pitch2;
+    double fbase=(period?(song.tuning*0.0625):song.tuning)*pow(2.0,(float)(nbase+384)/(128.0*12.0));
+    int bf=period?
+           (clock/fbase)/divider:
+           fbase*(divider/clock);
+    if (blockBits>0) {
+      CONVERT_FNUM_BLOCK(bf,blockBits,nbase>>7)
+    } else {
+      return bf;
+    }
   }
   if (song.linearPitch==1) {
     // global pitch multiplier
diff --git a/src/engine/engine.h b/src/engine/engine.h
index 9ac26d89..4fcc5f1b 100644
--- a/src/engine/engine.h
+++ b/src/engine/engine.h
@@ -484,7 +484,7 @@ class DivEngine {
     unsigned short calcBaseFreqFNumBlock(double clock, double divider, int note, int bits);
 
     // calculate frequency/period
-    int calcFreq(int base, int pitch, bool period=false, int octave=0, int pitch2=0, double clock=1.0, double divider=1.0);
+    int calcFreq(int base, int pitch, bool period=false, int octave=0, int pitch2=0, double clock=1.0, double divider=1.0, int blockBits=0);
 
     // convert panning formats
     int convertPanSplitToLinear(unsigned int val, unsigned char bits, int range);
diff --git a/src/engine/platform/genesis.cpp b/src/engine/platform/genesis.cpp
index 4b4771a3..2136efeb 100644
--- a/src/engine/platform/genesis.cpp
+++ b/src/engine/platform/genesis.cpp
@@ -471,7 +471,7 @@ void DivPlatformGenesis::tick(bool sysTick) {
   for (int i=0; i<6; i++) {
     if (i==2 && extMode) continue;
     if (chan[i].freqChanged) {
-      int fNum=parent->calcFreq(chan[i].baseFreq&0x7ff,chan[i].pitch,false,4,chan[i].pitch2);
+      int fNum=parent->calcFreq(chan[i].baseFreq&0x7ff,chan[i].pitch,false,4,chan[i].pitch2,chipClock,CHIP_FREQBASE,11);
       int block=(chan[i].baseFreq&0xf800)>>11;
       if (fNum<0) fNum=0;
       if (fNum>2047) {
@@ -495,7 +495,8 @@ void DivPlatformGenesis::tick(bool sysTick) {
             off=(double)s->centerRate/8363.0;
           }
         }
-        chan[i].freq=parent->calcFreq(chan[i].baseFreq,chan[i].pitch,false,4)+chan[i].pitch2;
+        // TODO: linear
+        chan[i].freq=parent->calcFreq(chan[i].baseFreq,chan[i].pitch,false,4,1,1)+chan[i].pitch2;
         dacRate=chan[i].freq*off;
         if (dacRate<1) dacRate=1;
         if (dumpWrites) addWrite(0xffff0001,dacRate);