From b6e4d9996ef38fbe43ca29c68ad9eec2abed304a Mon Sep 17 00:00:00 2001
From: goyuken <goyuken@4bbf4f03-6f44-549e-7e59-35d4b0962838>
Date: Sat, 29 Sep 2012 22:38:47 +0000
Subject: [PATCH] DCFilter: add a "push" mode more suited to being placed
 between a resampler and a metaspu Gambatte: change the order of output from
 "GB => resampler => metaspu => DCFilter" to "GB => resampler => DCFilter =>
 metaspu". This doesn't change anything under most circumstances, except when
 playing the emulator in slow motion (for instance, 50% throttle).  There, the
 metaspu sometimes adds silence to the output, which isn't actually silence if
 it has a different DC offset than the audio it's being mixed with.  Well, 50%
 throttle sound output will always suck anyway...

---
 .../Consoles/Nintendo/Gameboy/Gambatte.cs     | 16 +++++++++---
 BizHawk.Emulation/Sound/Utilities/DCFilter.cs | 26 +++++++++++++------
 2 files changed, 30 insertions(+), 12 deletions(-)

diff --git a/BizHawk.Emulation/Consoles/Nintendo/Gameboy/Gambatte.cs b/BizHawk.Emulation/Consoles/Nintendo/Gameboy/Gambatte.cs
index 18114ca4da..8e65deb69f 100644
--- a/BizHawk.Emulation/Consoles/Nintendo/Gameboy/Gambatte.cs
+++ b/BizHawk.Emulation/Consoles/Nintendo/Gameboy/Gambatte.cs
@@ -585,13 +585,15 @@ namespace BizHawk.Emulation.Consoles.GB
 		int soundbuffcontains = 0;
 
 		Sound.Utilities.SpeexResampler resampler;
-		ISoundProvider metaspu;
+		Sound.MetaspuSoundProvider metaspu;
+
+		Sound.Utilities.DCFilter dcfilter;
 
 		void InitSound()
 		{
-			var metaspu = new Sound.MetaspuSoundProvider(Sound.ESynchMethod.ESynchMethod_V);
-			resampler = new Sound.Utilities.SpeexResampler(2, 2097152, 44100, 2097152, 44100, metaspu.buffer.enqueue_samples);
-			this.metaspu = new Sound.Utilities.DCFilter(metaspu);// metaspu;
+			dcfilter = new Sound.Utilities.DCFilter();
+			metaspu = new Sound.MetaspuSoundProvider(Sound.ESynchMethod.ESynchMethod_V);
+			resampler = new Sound.Utilities.SpeexResampler(2, 2097152, 44100, 2097152, 44100, LoadThroughSamples);
 		}
 
 		void DisposeSound()
@@ -600,6 +602,12 @@ namespace BizHawk.Emulation.Consoles.GB
 			resampler = null;
 		}
 
+		void LoadThroughSamples(short[] buff, int length)
+		{
+			dcfilter.PushThroughSamples(buff, length * 2);
+			metaspu.buffer.enqueue_samples(buff, length);
+		}
+
 		public void GetSamples(short[] samples)
 		{
 			if (soundbuffcontains > 0)
diff --git a/BizHawk.Emulation/Sound/Utilities/DCFilter.cs b/BizHawk.Emulation/Sound/Utilities/DCFilter.cs
index e2575c6ce1..b910e1c1ec 100644
--- a/BizHawk.Emulation/Sound/Utilities/DCFilter.cs
+++ b/BizHawk.Emulation/Sound/Utilities/DCFilter.cs
@@ -25,8 +25,12 @@ namespace BizHawk.Emulation.Sound.Utilities
 		Queue<short> buffer;
 
 		const int depth = 65536;
-
-		public DCFilter(ISoundProvider input)
+		
+		/// <summary>
+		/// if input == null, run in detatched push mode
+		/// </summary>
+		/// <param name="input"></param>
+		public DCFilter(ISoundProvider input = null)
 		{
 			this.input = input;
 			this.buffer = new Queue<short>(depth * 2);
@@ -45,13 +49,13 @@ namespace BizHawk.Emulation.Sound.Utilities
 			input = null;
 			return ret;
 		}
-
-		public void GetSamples(short[] samples)
+		
+		/// <summary>
+		/// pass a set of samples through the filter.  should not be mixed with pull (ISoundProvider) mode
+		/// </summary>
+		public void PushThroughSamples(short[] samples, int length)
 		{
-
-			input.GetSamples(samples);
-
-			for (int i = 0; i < samples.Length; i += 2)
+			for (int i = 0; i < length; i += 2)
 			{
 				sumL -= buffer.Dequeue();
 				sumR -= buffer.Dequeue();
@@ -80,6 +84,12 @@ namespace BizHawk.Emulation.Sound.Utilities
 			}
 		}
 
+		public void GetSamples(short[] samples)
+		{
+			input.GetSamples(samples);
+			PushThroughSamples(samples, samples.Length);
+		}
+
 		public void DiscardSamples()
 		{
 			input.DiscardSamples();