From ba28706092fbb7c9255b456a040d8fcfcfbb7b9d Mon Sep 17 00:00:00 2001
From: Nathaniel Walizer <robots.are.love@gmail.com>
Date: Tue, 7 Jan 2025 02:51:00 -0800
Subject: [PATCH] Clean up sweep and envelope restarts

 - SMB3 pipe/shrink sound still a little off
---
 src/apu.c | 34 +++++++++++++++-------------------
 1 file changed, 15 insertions(+), 19 deletions(-)

diff --git a/src/apu.c b/src/apu.c
index 98e630b..1039f58 100644
--- a/src/apu.c
+++ b/src/apu.c
@@ -81,8 +81,6 @@ static void nes_apu_write_square(nes_apu_Channel* channel,
                 ((val & apu_Square_Period) >> 4)
             );
         channel->flags |= apu_Channel_Reload;
-        //channel->sweep_delay = 0;
-        //channel->step = 0;
 
     } else if (2 <= reg) {
         channel->reg[reg] = val;
@@ -90,14 +88,11 @@ static void nes_apu_write_square(nes_apu_Channel* channel,
                 (apu_channel_raw_timer_value(channel) /*+ 1*/) * 2
             ) * nes_clock_cpu_div;
         if (3 == reg) {
-            //channel->flags |= apu_Channel_Reload; // TODO: No?
-//            channel->sweep_delay = 0; // TODO: No?
-//            channel->step = 7;
-//            channel->envelope = 15;
-            //channel->envelope = (channel->reg[0] & apu_Envelope_Volume);
+//            channel->flags |= apu_Channel_Reload;
+            channel->delay = 0;
+            // Envelope and step are already restarted
         }
     }
-    // TODO?
 }
 
 static void nes_apu_write_triangle(nes_apu_Channel* channel,
@@ -235,12 +230,15 @@ static inline void nes_apu_clock_length(nes_apu_Channel* channel,
 
 static inline void nes_apu_clock_sweep(nes_apu_Channel* channel,
                                        int adjust) {
+    int decrement = 1;
+
     if (channel->flags & apu_Channel_Reload) {
         channel->flags &= ~apu_Channel_Reload;
-        channel->sweep_delay = channel->sweep_period;
+        decrement = 0;
+    }
 
-    } else if (channel->sweep_delay == 0) {
-        channel->sweep_delay = channel->sweep_period;
+    if (channel->sweep_delay == 0) {
+        decrement = 0;
         if (    (channel->reg[1] & apu_Square_Enable) &&
                 0 != (channel->reg[1] & apu_Square_Shift)) {
             int delta = (
@@ -255,9 +253,12 @@ static inline void nes_apu_clock_sweep(nes_apu_Channel* channel,
                 channel->period = 0;
             }
         }
+    }
 
-    } else {
+    if (decrement) {
         channel->sweep_delay--;
+    } else {
+        channel->sweep_delay = channel->sweep_period;
     }
 }
 
@@ -317,13 +318,8 @@ void nes_apu_write(nes_apu* apu, uint16_t addr, uint8_t val) {
             if (    chan != apu_Channel_DMC &&
                     (apu->status & (1 << chan))) {
                 channel->length = apu_length_lut[val >> 3];
-//                channel->step = (uint8_t)-1;
-                /*if (chan != apu_Channel_Triangle)*/ {
-                    channel->flags |= apu_Channel_Start;
-//                    channel->envelope = 15;
-                    // TODO
-//                    channel->env_delay = channel->env_period;
-                }
+                channel->step = (uint8_t)-1;
+                channel->flags |= apu_Channel_Start;
             }
         }
         channel->write(channel, reg, val);