From 72dc7b5318eb6abc1486729afb253a21014f79b0 Mon Sep 17 00:00:00 2001
From: Brendan Robert <brendan.robert@gmail.com>
Date: Sat, 8 Aug 2015 04:03:13 -0500
Subject: [PATCH] Better-sounding noise generator, Halls of Doom in Ultima 5
 sounds much better

---
 src/main/java/jace/hardware/mockingboard/NoiseGenerator.java | 1 +
 src/main/java/jace/hardware/mockingboard/PSG.java            | 4 +++-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/main/java/jace/hardware/mockingboard/NoiseGenerator.java b/src/main/java/jace/hardware/mockingboard/NoiseGenerator.java
index 27ec51d..4e88482 100644
--- a/src/main/java/jace/hardware/mockingboard/NoiseGenerator.java
+++ b/src/main/java/jace/hardware/mockingboard/NoiseGenerator.java
@@ -39,6 +39,7 @@ public class NoiseGenerator extends TimedGenerator {
     }
     public static final int bit17 = 0x010000;
     public void updateRng() {
+        // noise = (noise >> 1) ^ ((noise & 1) ? 0x14000 : 0);
         int newBit17 = (rng & 0x04) > 0 == (rng & 0x01) > 0 ? bit17 : 0;
         rng = newBit17 + (rng >> 1);
     }
diff --git a/src/main/java/jace/hardware/mockingboard/PSG.java b/src/main/java/jace/hardware/mockingboard/PSG.java
index ed9d600..67b9a81 100644
--- a/src/main/java/jace/hardware/mockingboard/PSG.java
+++ b/src/main/java/jace/hardware/mockingboard/PSG.java
@@ -207,6 +207,7 @@ public class PSG {
         /* Also, note that period = 0 is the same as period = 1. This is mentioned */
         /* in the YM2203 data sheets. However, this does NOT apply to the Envelope */
         /* period. In that case, period = 0 is half as period = 1. */
+        value = value & 0x0ff;
         switch (r) {
             case ACoarse:
             case AFine:
@@ -221,7 +222,8 @@ public class PSG {
                 channels.get(2).setPeriod(getReg(Reg.CFine) + (getReg(Reg.CCoarse) << 8));
                 break;
             case NoisePeriod:
-                noiseGenerator.setPeriod(value);
+                if (value == 0) value = 32;
+                noiseGenerator.setPeriod(value+16);
                 noiseGenerator.counter = 0;
                 break;
             case Enable: