From a862a8ae5978332e1300d76d73082acdbf3f273d Mon Sep 17 00:00:00 2001
From: tildearrow <me@tildearrow.org>
Date: Tue, 13 Jan 2026 19:08:05 -0500
Subject: [PATCH] dev242 - OPL4: add options for default FM/PCM leve

issue #2711
---
 src/engine/engine.h         |  4 ++--
 src/engine/fileOps/fur.cpp  | 12 ++++++++++++
 src/engine/platform/opl.cpp | 21 +++++++++++++++++----
 src/engine/platform/opl.h   |  3 ++-
 src/gui/sysConf.cpp         | 32 ++++++++++++++++++++++++++++++++
 5 files changed, 65 insertions(+), 7 deletions(-)

diff --git a/src/engine/engine.h b/src/engine/engine.h
index 20220b28f..3c3602544 100644
--- a/src/engine/engine.h
+++ b/src/engine/engine.h
@@ -56,8 +56,8 @@ class DivWorkPool;
 
 #define DIV_UNSTABLE
 
-#define DIV_VERSION "dev241"
-#define DIV_ENGINE_VERSION 241
+#define DIV_VERSION "dev242"
+#define DIV_ENGINE_VERSION 242
 // for imports
 #define DIV_VERSION_MOD 0xff01
 #define DIV_VERSION_FC 0xff02
diff --git a/src/engine/fileOps/fur.cpp b/src/engine/fileOps/fur.cpp
index 204c2d502..62db6732e 100644
--- a/src/engine/fileOps/fur.cpp
+++ b/src/engine/fileOps/fur.cpp
@@ -2395,6 +2395,18 @@ bool DivEngine::loadFur(unsigned char* file, size_t len, int variantID) {
       }
     }
 
+    // OPL4 default mix levels
+    if (ds.version<242) {
+      for (int i=0; i<ds.systemLen; i++) {
+        if (ds.system[i]==DIV_SYSTEM_OPL4 || ds.system[i]==DIV_SYSTEM_OPL4_DRUMS) {
+          ds.systemFlags[i].set("fmMixL",7);
+          ds.systemFlags[i].set("fmMixR",7);
+          ds.systemFlags[i].set("pcmMixL",7);
+          ds.systemFlags[i].set("pcmMixR",7);
+        }
+      }
+    }
+
     // warn on partial pitch linearity
     if (ds.compatFlags.linearPitch>1) {
       ds.compatFlags.linearPitch=1;
diff --git a/src/engine/platform/opl.cpp b/src/engine/platform/opl.cpp
index 8dd37fdb7..a63e37658 100644
--- a/src/engine/platform/opl.cpp
+++ b/src/engine/platform/opl.cpp
@@ -2903,10 +2903,10 @@ void DivPlatformOPL::reset() {
       // Reset wavetable header
       immWrite(0x202,PCM_IN_RAM?0x10:0x00);
       // initialize mixer volume
-      fmMixL=7;
-      fmMixR=7;
-      pcmMixL=7;
-      pcmMixR=7;
+      fmMixL=fmMixLDef;
+      fmMixR=fmMixRDef;
+      pcmMixL=pcmMixLDef;
+      pcmMixR=pcmMixRDef;
       immWrite(PCM_ADDR_MIX_FM,((7-fmMixR)<<3)|(7-fmMixL));
       immWrite(PCM_ADDR_MIX_PCM,((7-pcmMixR)<<3)|(7-pcmMixL));
     } else {
@@ -3190,6 +3190,19 @@ void DivPlatformOPL::setFlags(const DivConfig& flags) {
   compatPan=flags.getBool("compatPan",false);
   compatYPitch=flags.getBool("compatYPitch",false);
 
+  fmMixLDef=flags.getInt("fmMixL",4);
+  fmMixRDef=flags.getInt("fmMixR",4);
+  pcmMixLDef=flags.getInt("pcmMixL",7);
+  pcmMixRDef=flags.getInt("pcmMixR",7);
+  if (fmMixLDef<0) fmMixLDef=0;
+  if (fmMixLDef>7) fmMixLDef=7;
+  if (fmMixRDef<0) fmMixRDef=0;
+  if (fmMixRDef>7) fmMixRDef=7;
+  if (pcmMixLDef<0) pcmMixLDef=0;
+  if (pcmMixLDef>7) pcmMixLDef=7;
+  if (pcmMixRDef<0) pcmMixRDef=0;
+  if (pcmMixRDef>7) pcmMixRDef=7;
+
   for (int i=0; i<44; i++) {
     oscBuf[i]->setRate(rate);
   }
diff --git a/src/engine/platform/opl.h b/src/engine/platform/opl.h
index 676e7d4a9..571a16512 100644
--- a/src/engine/platform/opl.h
+++ b/src/engine/platform/opl.h
@@ -133,7 +133,8 @@ class DivPlatformOPL: public DivDispatch {
     const unsigned char* outChanMap;
     int chipFreqBase, chipRateBase;
     int delay, chipType, oplType, chans, melodicChans, totalChans, adpcmChan=-1, pcmChanOffs=-1, totalOutputs, ramSize;
-    int fmMixL=7, fmMixR=7, pcmMixL=7, pcmMixR=7;
+    int fmMixL, fmMixR, pcmMixL, pcmMixR;
+    int fmMixLDef, fmMixRDef, pcmMixLDef, pcmMixRDef;
     unsigned char lastBusy;
     unsigned char drumState;
     unsigned char drumVol[5];
diff --git a/src/gui/sysConf.cpp b/src/gui/sysConf.cpp
index 790c4eed4..95a51a0e1 100644
--- a/src/gui/sysConf.cpp
+++ b/src/gui/sysConf.cpp
@@ -2670,6 +2670,10 @@ bool FurnaceGUI::drawSysConf(int chan, int sysPos, DivSystem type, DivConfig& fl
     case DIV_SYSTEM_OPL4_DRUMS: {
       int clockSel=flags.getInt("clockSel",0);
       int ramSize=flags.getInt("ramSize",0);
+      int fmMixL=flags.getInt("fmMixL",4);
+      int fmMixR=flags.getInt("fmMixR",4);
+      int pcmMixL=flags.getInt("pcmMixL",7);
+      int pcmMixR=flags.getInt("pcmMixR",7);
 
       ImGui::Text(_("Clock rate:"));
       ImGui::Indent();
@@ -2726,10 +2730,38 @@ bool FurnaceGUI::drawSysConf(int chan, int sysPos, DivSystem type, DivConfig& fl
       }
       ImGui::Unindent();
 
+      ImGui::Text("FM volume:");
+      if (CWSliderInt(_("Left##FMMixL"),&fmMixL,0,7)) {
+        if (fmMixL<0) fmMixL=0;
+        if (fmMixL>7) fmMixL=7;
+        altered=true;
+      } rightClickable
+      if (CWSliderInt(_("Right##FMMixR"),&fmMixR,0,7)) {
+        if (fmMixR<0) fmMixR=0;
+        if (fmMixR>7) fmMixR=7;
+        altered=true;
+      } rightClickable
+
+      ImGui::Text("PCM volume:");
+      if (CWSliderInt(_("Left##PCMMixL"),&pcmMixL,0,7)) {
+        if (pcmMixL<0) pcmMixL=0;
+        if (pcmMixL>7) pcmMixL=7;
+        altered=true;
+      } rightClickable
+      if (CWSliderInt(_("Right##PCMMixR"),&pcmMixR,0,7)) {
+        if (pcmMixR<0) pcmMixR=0;
+        if (pcmMixR>7) pcmMixR=7;
+        altered=true;
+      } rightClickable
+
       if (altered) {
         e->lockSave([&]() {
           flags.set("clockSel",clockSel);
           flags.set("ramSize",ramSize);
+          flags.set("fmMixL",fmMixL);
+          flags.set("fmMixR",fmMixR);
+          flags.set("pcmMixL",pcmMixL);
+          flags.set("pcmMixR",pcmMixR);
         });
       }
       break;