From bcade6931a45163096c59c04f4f38223d8600f0a Mon Sep 17 00:00:00 2001
From: tildearrow <tildearrow@protonmail.com>
Date: Mon, 25 Apr 2022 01:42:26 -0500
Subject: [PATCH] YM2612: allow for DAC rate higher than 32KHz

issue #391
---
 src/engine/platform/genesis.cpp | 26 ++++++++++++++++++++++----
 src/engine/platform/genesis.h   |  2 ++
 2 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/src/engine/platform/genesis.cpp b/src/engine/platform/genesis.cpp
index 324a66e0..f2203fc3 100644
--- a/src/engine/platform/genesis.cpp
+++ b/src/engine/platform/genesis.cpp
@@ -86,14 +86,22 @@ void DivPlatformGenesis::acquire_nuked(short* bufL, short* bufR, size_t start, s
   static int os[2];
 
   for (size_t h=start; h<start+len; h++) {
+    if (!dacReady) {
+      dacDelay+=32000;
+      if (dacDelay>=rate) {
+        dacDelay-=rate;
+        dacReady=true;
+      }
+    }
     if (dacMode && dacSample!=-1) {
       dacPeriod+=dacRate;
       if (dacPeriod>=rate) {
         DivSample* s=parent->getSample(dacSample);
         if (s->samples>0) {
           if (!isMuted[5]) {
-            if (writes.size()<16) {
+            if (dacReady && writes.size()<16) {
               urgentWrite(0x2a,(unsigned char)s->data8[dacPos]+0x80);
+              dacReady=false;
             }
           }
           if (++dacPos>=s->samples) {
@@ -106,7 +114,7 @@ void DivPlatformGenesis::acquire_nuked(short* bufL, short* bufR, size_t start, s
               }
             }
           }
-          dacPeriod-=rate;
+          while (dacPeriod>=rate) dacPeriod-=rate;
         } else {
           dacSample=-1;
         }
@@ -155,14 +163,22 @@ void DivPlatformGenesis::acquire_ymfm(short* bufL, short* bufR, size_t start, si
   static int os[2];
 
   for (size_t h=start; h<start+len; h++) {
+    if (!dacReady) {
+      dacDelay+=32000;
+      if (dacDelay>=rate) {
+        dacDelay-=rate;
+        dacReady=true;
+      }
+    }
     if (dacMode && dacSample!=-1) {
       dacPeriod+=dacRate;
       if (dacPeriod>=rate) {
         DivSample* s=parent->getSample(dacSample);
         if (s->samples>0) {
           if (!isMuted[5]) {
-            if (writes.size()<16) {
+            if (dacReady && writes.size()<16) {
               urgentWrite(0x2a,(unsigned char)s->data8[dacPos]+0x80);
+              dacReady=false;
             }
           }
           if (++dacPos>=s->samples) {
@@ -175,7 +191,7 @@ void DivPlatformGenesis::acquire_ymfm(short* bufL, short* bufR, size_t start, si
               }
             }
           }
-          dacPeriod-=rate;
+          while (dacPeriod>=rate) dacPeriod-=rate;
         } else {
           dacSample=-1;
         }
@@ -858,6 +874,8 @@ void DivPlatformGenesis::reset() {
   dacPeriod=0;
   dacPos=0;
   dacRate=0;
+  dacDelay=0;
+  dacReady=true;
   dacSample=-1;
   sampleBank=0;
   lfoValue=8;
diff --git a/src/engine/platform/genesis.h b/src/engine/platform/genesis.h
index b9430306..aa7659fa 100644
--- a/src/engine/platform/genesis.h
+++ b/src/engine/platform/genesis.h
@@ -85,6 +85,8 @@ class DivPlatformGenesis: public DivDispatch {
     int dacRate;
     unsigned int dacPos;
     int dacSample;
+    int dacDelay;
+    bool dacReady;
     unsigned char sampleBank;
     unsigned char lfoValue;