From 1fb05abc662bc7c1147ca27cf4c94065f22edc0c Mon Sep 17 00:00:00 2001
From: Washi <washiwashi1337@gmail.com>
Date: Sat, 16 Sep 2017 17:26:09 +0200
Subject: [PATCH] Sound channel 1 sfx improvements

---
 Emux.GameBoy/Audio/SquareChannel.cs      | 19 +++++++++++--------
 Emux.GameBoy/Audio/SquareSweepChannel.cs | 16 +++++++++++++---
 Emux/Audio/GameBoyAudioMixer.cs          |  2 +-
 3 files changed, 25 insertions(+), 12 deletions(-)

diff --git a/Emux.GameBoy/Audio/SquareChannel.cs b/Emux.GameBoy/Audio/SquareChannel.cs
index 523f57d..de528a6 100644
--- a/Emux.GameBoy/Audio/SquareChannel.cs
+++ b/Emux.GameBoy/Audio/SquareChannel.cs
@@ -24,7 +24,7 @@ namespace Emux.GameBoy.Audio
             _spu = spu;
         }
 
-        public byte NR0
+        public virtual byte NR0
         {
             get { return _nr0; }
             set { _nr0 = value; }
@@ -167,22 +167,25 @@ namespace Emux.GameBoy.Audio
 
             const float maxAmplitude = 0.05f;
 
-            double realFrequency = 131072.0 / (2048.0 - Frequency) / 2;
+            double realFrequency = 131072.0 / (2048.0 - Frequency);
             int sampleRate = ChannelOutput.SampleRate;
-            double timeDelta = (cycles / GameBoyCpu.OfficialClockFrequency) / cpuSpeedFactor * 2;
-            int sampleCount = (int) (timeDelta * sampleRate);
+            double timeDelta = (cycles / GameBoyCpu.OfficialClockFrequency) / cpuSpeedFactor;
+            int sampleCount = (int)(timeDelta * sampleRate * 2);
             float[] buffer = new float[sampleCount];
 
             if (!UseSoundLength || _length >= 0)
             {
-                for (int i = 0; i < buffer.Length; i++)
+                for (int i = 0; i < buffer.Length; i += 2)
                 {
-                    buffer[i] = (float) (maxAmplitude * (_volume / 15.0)                                // Volume adjustments.
-                        * Math.Sign(Math.Sin(2 * Math.PI * realFrequency * _coordinate / sampleRate))); // Square wave formula
+                    float sample = (float)(maxAmplitude * (_volume / 15.0)                                                 // Volume adjustments.
+                                           * Math.Sign(Math.Sin(2 * Math.PI * realFrequency * _coordinate / sampleRate))); // Square wave formula
+                    buffer[i] = sample;
+                    if (i < buffer.Length - 1)
+                        buffer[i + 1] = sample;
                     _coordinate = (_coordinate + 1) % sampleRate;
                 }
 
-                if(UseSoundLength)
+                if (UseSoundLength)
                     _length -= timeDelta;
             }
 
diff --git a/Emux.GameBoy/Audio/SquareSweepChannel.cs b/Emux.GameBoy/Audio/SquareSweepChannel.cs
index 6fcbd5f..178f8be 100644
--- a/Emux.GameBoy/Audio/SquareSweepChannel.cs
+++ b/Emux.GameBoy/Audio/SquareSweepChannel.cs
@@ -14,9 +14,19 @@ namespace Emux.GameBoy.Audio
             _spu = spu;
         }
 
+        public override byte NR0
+        {
+            get { return base.NR0; }
+            set
+            {
+                base.NR0 = value;
+                _frequencySweepClock = 0;
+            }
+        }
+
         public float SweepFrequency
         {
-            get { return (NR0 >> 4) / 128f; }
+            get { return ((NR0 >> 4) & 7) / 128f; }
         }
 
         public bool SweepIncrease
@@ -33,10 +43,10 @@ namespace Emux.GameBoy.Audio
         {
             if (SweepShiftCount > 0 && _spu.Device.Cpu.SpeedFactor > 0.5)
             {
-                double timeDelta = (cycles / GameBoyCpu.OfficialClockFrequency) / _spu.Device.Cpu.SpeedFactor * 2;
+                double timeDelta = (cycles / GameBoyCpu.OfficialClockFrequency) / _spu.Device.Cpu.SpeedFactor;
                 _frequencySweepClock += timeDelta;
                 
-                double sweepInterval = 1.0 / SweepFrequency;
+                double sweepInterval = SweepFrequency;
                 while (_frequencySweepClock >= sweepInterval)
                 {
                     _frequencySweepClock -= sweepInterval;
diff --git a/Emux/Audio/GameBoyAudioMixer.cs b/Emux/Audio/GameBoyAudioMixer.cs
index 5595729..fd11e32 100644
--- a/Emux/Audio/GameBoyAudioMixer.cs
+++ b/Emux/Audio/GameBoyAudioMixer.cs
@@ -105,7 +105,7 @@ namespace Emux.Audio
         {
             lock (this)
             {
-                if (IsRecording)
+                if (!IsRecording)
                     throw new InvalidOperationException("Cannot stop a recording when a recording is not happening.");
                 try
                 {