From ef11c2bf97f096e5b4e821b38383af82b1b5cd32 Mon Sep 17 00:00:00 2001
From: tildearrow <me@tildearrow.org>
Date: Sat, 10 Jan 2026 03:44:58 -0500
Subject: [PATCH] implement tremolo in command stream player

---
 src/engine/cmdStream.cpp | 30 ++++++++++++++++++++++++------
 src/engine/cmdStream.h   | 11 +++++++++++
 2 files changed, 35 insertions(+), 6 deletions(-)

diff --git a/src/engine/cmdStream.cpp b/src/engine/cmdStream.cpp
index 9060d85a6..e3bdb2e74 100644
--- a/src/engine/cmdStream.cpp
+++ b/src/engine/cmdStream.cpp
@@ -172,6 +172,7 @@ bool DivCSPlayer::tick() {
         case 0xc8: // vol slide
           chan[i].volSpeed=(short)(bigEndian?stream.readS_BE():stream.readS());
           chan[i].volSpeedTarget=-1;
+          chan[i].tremoloDepth=0;
           break;
         case 0xc9: // porta
           chan[i].portaTarget=(int)((unsigned char)stream.readC())-60;
@@ -195,11 +196,18 @@ bool DivCSPlayer::tick() {
           chan[i].volSpeedTarget=arg0==0 ? -1 : arg1;
           break;
         }
-        case 0xcc: // tremolo (TODO)
-          stream.readC();
+        case 0xcc: // tremolo
+          unsigned char param=stream.readC();
+          chan[i].tremoloDepth=param&15;
+          chan[i].tremoloRate=param>>4;
+          chan[i].volSpeed=0;
+          chan[i].volSpeedTarget=-1;
+          sendVolume=true;
           break;
-        case 0xcd: // panbrello (TODO)
-          stream.readC();
+        case 0xcd: // panbrello
+          unsigned char param=stream.readC();
+          chan[i].panbrelloDepth=param&15;
+          chan[i].panbrelloRate=param>>4;
           break;
         case 0xce: // pan slide (TODO)
           stream.readC();
@@ -554,7 +562,7 @@ bool DivCSPlayer::tick() {
       if (mustTell) chan[i].readPos=stream.tell();
     }
 
-    if (sendVolume || chan[i].volSpeed!=0) {
+    if (sendVolume || chan[i].volSpeed!=0 || chan[i].tremoloDepth!=0) {
       int preSpeedVol=chan[i].volume;
       chan[i].volume+=chan[i].volSpeed;
       if (chan[i].volSpeedTarget!=-1) {
@@ -578,13 +586,20 @@ bool DivCSPlayer::tick() {
           chan[i].volSpeedTarget=-1;
         }
       }
+
       if (chan[i].volume<0) {
         chan[i].volume=0;
       }
       if (chan[i].volume>chan[i].volMax) {
         chan[i].volume=chan[i].volMax;
       }
-      e->dispatchCmd(DivCommand(DIV_CMD_VOLUME,i,chan[i].volume>>8));
+      if (chan[i].tremoloDepth>0) {
+        chan[i].tremoloPos+=chan[i].tremoloRate;
+        chan[i].tremoloPos&=127;
+        dispatchCmd(DivCommand(DIV_CMD_VOLUME,i,MAX(0,chan[i].volume-(tremTable[chan[i].tremoloPos]*chan[i].tremoloDepth))>>8));
+      } else {
+        e->dispatchCmd(DivCommand(DIV_CMD_VOLUME,i,chan[i].volume>>8));
+      }
     }
 
     if (sendPitch || chan[i].vibratoDepth!=0) {
@@ -716,6 +731,9 @@ bool DivCSPlayer::init() {
   for (int i=0; i<64; i++) {
     vibTable[i]=127*sin(((double)i/64.0)*(2*M_PI));
   }
+  for (int i=0; i<128; i++) {
+    tremTable[i]=255*0.5*(1.0-cos(((double)i/128.0)*(2*M_PI)));
+  }
 
   arpSpeed=1;
   bAccessTS=new unsigned short[bLen];
diff --git a/src/engine/cmdStream.h b/src/engine/cmdStream.h
index b38be0b04..24368fd6a 100644
--- a/src/engine/cmdStream.h
+++ b/src/engine/cmdStream.h
@@ -37,6 +37,8 @@ struct DivCSChannelState {
   int note, pitch;
   int volume, volMax, volSpeed, volSpeedTarget;
   int vibratoDepth, vibratoRate, vibratoPos, vibratoRange, vibratoShape;
+  int tremoloDepth, tremoloRate, tremoloPos;
+  int panbrelloDepth, panbrelloRate, panbrelloPos;
   int portaTarget, portaSpeed;
   unsigned char arp, arpStage, arpTicks;
 
@@ -61,6 +63,14 @@ struct DivCSChannelState {
     vibratoDepth(0),
     vibratoRate(0),
     vibratoPos(0),
+    vibratoRange(15),
+    vibratoShape(0),
+    tremoloDepth(0),
+    tremoloRate(0),
+    tremoloPos(0),
+    panbrelloDepth(0),
+    panbrelloRate(0),
+    panbrelloPos(0),
     portaTarget(0),
     portaSpeed(0),
     arp(0),
@@ -93,6 +103,7 @@ class DivCSPlayer {
   bool bigEndian;
 
   short vibTable[64];
+  short tremTable[128];
   public:
     unsigned char* getData();
     unsigned short* getDataAccess();