From 9f105d92a8e254cd5ba46d71cc8c32780c91c2b8 Mon Sep 17 00:00:00 2001
From: tildearrow <tildearrow@protonmail.com>
Date: Sun, 9 Oct 2022 17:24:24 -0500
Subject: [PATCH] VGM export: why

---
 src/engine/vgmOps.cpp | 56 ++++++++++++++++++++++++++++++-------------
 1 file changed, 39 insertions(+), 17 deletions(-)

diff --git a/src/engine/vgmOps.cpp b/src/engine/vgmOps.cpp
index 67817a5e..815436fd 100644
--- a/src/engine/vgmOps.cpp
+++ b/src/engine/vgmOps.cpp
@@ -807,6 +807,20 @@ void DivEngine::performVGMWrite(SafeWriter* w, DivSystem sys, DivRegWrite& write
   }
 }
 
+#define CHIP_VOL(_id,_mult) { \
+  double _vol=fabs(song.systemVol[i])*4.0*_mult; \
+  if (_vol<0.0) _vol=0.0; \
+  if (_vol>32767.0) _vol=32767.0; \
+  chipVol.push_back((_id)|(0x80000000)|(((unsigned int)_vol)<<16)); \
+}
+
+#define CHIP_VOL_SECOND(_id,_mult) { \
+  double _vol=fabs(song.systemVol[i])*4.0*_mult; \
+  if (_vol<0.0) _vol=0.0; \
+  if (_vol>32767.0) _vol=32767.0; \
+  chipVol.push_back((_id)|(0x80000100)|(((unsigned int)_vol)<<16)); \
+}
+
 SafeWriter* DivEngine::saveVGM(bool* sysToExport, bool loop, int version, bool patternHints) {
   if (version<0x150) {
     lastError="VGM version is too low";
@@ -910,6 +924,7 @@ SafeWriter* DivEngine::saveVGM(bool* sysToExport, bool loop, int version, bool p
   double loopFreq[DIV_MAX_CHANS];
   int loopSample[DIV_MAX_CHANS];
   bool sampleDir[DIV_MAX_CHANS];
+  std::vector<unsigned int> chipVol; 
 
   for (int i=0; i<DIV_MAX_CHANS; i++) {
     loopTimer[i]=0;
@@ -943,6 +958,7 @@ SafeWriter* DivEngine::saveVGM(bool* sysToExport, bool loop, int version, bool p
       case DIV_SYSTEM_SMS:
         if (!hasSN) {
           hasSN=disCont[i].dispatch->chipClock;
+          CHIP_VOL(0,1.0);
           willExport[i]=true;
           switch (song.systemFlags[i].getInt("chipType",0)) {
             case 1: // real SN
@@ -961,6 +977,7 @@ SafeWriter* DivEngine::saveVGM(bool* sysToExport, bool loop, int version, bool p
         } else if (!(hasSN&0x40000000)) {
           isSecond[i]=true;
           willExport[i]=true;
+          CHIP_VOL_SECOND(0,1.0);
           hasSN|=0x40000000;
           howManyChips++;
         }
@@ -1353,14 +1370,6 @@ SafeWriter* DivEngine::saveVGM(bool* sysToExport, bool loop, int version, bool p
     }
   }
 
-  //bool wantsExtraHeader=false;
-  /*for (int i=0; i<song.systemLen; i++) {
-    if (isSecond[i]) {
-      wantsExtraHeader=true;
-      break;
-    }
-  }*/
-
   // write chips and stuff
   w->writeI(hasSN);
   w->writeI(hasOPLL);
@@ -1422,8 +1431,15 @@ SafeWriter* DivEngine::saveVGM(bool* sysToExport, bool loop, int version, bool p
     w->writeC(0); // OPN
     w->writeC(0); // OPNA
   }
+  if (version>=0x160) {
+    int calcVolume=32.0*(log(song.masterVol)/log(2.0));
+    if (calcVolume<-63) calcVolume=-63;
+    if (calcVolume>192) calcVolume=192;
+    w->writeC(calcVolume&0xff); // volume
+  } else {
+    w->writeC(0); // volume
+  }
   // currently not used but is part of 1.60
-  w->writeC(0); // volume
   w->writeC(0); // reserved
   w->writeC(0); // loop count
   // 1.51
@@ -1507,15 +1523,21 @@ SafeWriter* DivEngine::saveVGM(bool* sysToExport, bool loop, int version, bool p
     w->writeI(0);
   }
 
-  /* TODO
   unsigned int exHeaderOff=w->tell();
-  if (wantsExtraHeader) {
-    w->writeI(4);
+  if (version>=0x170) {
+    logD("writing extended header...");
+    w->writeI(8);
+    w->writeI(0);
     w->writeI(4);
 
-    // write clocks
-    w->writeC(howManyChips);
-  }*/
+    // write chip volumes
+    logD("writing chip volumes (%ld)...",chipVol.size());
+    w->writeC(chipVol.size());
+    for (unsigned int& i: chipVol) {
+      logV("- %.8x",i);
+      w->writeI(i);
+    }
+  }
 
   unsigned int songOff=w->tell();
 
@@ -2015,10 +2037,10 @@ SafeWriter* DivEngine::saveVGM(bool* sysToExport, bool loop, int version, bool p
   }
   w->seek(0x34,SEEK_SET);
   w->writeI(songOff-0x34);
-  /*if (wantsExtraHeader) {
+  if (version>=0x170) {
     w->seek(0xbc,SEEK_SET);
     w->writeI(exHeaderOff-0xbc);
-  }*/
+  }
 
   remainingLoops=-1;
   playing=false;