From 20d28e80a5c861a9d5f449ea911ab75b4f37ad0d Mon Sep 17 00:00:00 2001
From: Jef <jef@targetspot.com>
Date: Tue, 24 Sep 2024 14:54:57 +0200
Subject: Initial community commit

---
 .../openmpt-trunk/sounddsp/AGC.cpp                 | 141 +++++++++++++++++++++
 1 file changed, 141 insertions(+)
 create mode 100644 Src/external_dependencies/openmpt-trunk/sounddsp/AGC.cpp

(limited to 'Src/external_dependencies/openmpt-trunk/sounddsp/AGC.cpp')

diff --git a/Src/external_dependencies/openmpt-trunk/sounddsp/AGC.cpp b/Src/external_dependencies/openmpt-trunk/sounddsp/AGC.cpp
new file mode 100644
index 00000000..fac3408a
--- /dev/null
+++ b/Src/external_dependencies/openmpt-trunk/sounddsp/AGC.cpp
@@ -0,0 +1,141 @@
+/*
+ * AGC.cpp
+ * -------
+ * Purpose: Automatic Gain Control
+ * Notes  : Ugh... This should really be removed at some point.
+ * Authors: Olivier Lapicque
+ *          OpenMPT Devs
+ * The OpenMPT source code is released under the BSD license. Read LICENSE for more details.
+ */
+
+
+#include "stdafx.h"
+#include "../sounddsp/AGC.h"
+
+
+OPENMPT_NAMESPACE_BEGIN
+
+	
+//////////////////////////////////////////////////////////////////////////////////
+// Automatic Gain Control
+
+#ifndef NO_AGC
+
+#define AGC_PRECISION		10
+#define AGC_UNITY			(1 << AGC_PRECISION)
+
+// Limiter
+#define MIXING_LIMITMAX		(0x08100000)
+#define MIXING_LIMITMIN		(-MIXING_LIMITMAX)
+
+
+static UINT ProcessAGC(int *pBuffer, int *pRearBuffer, std::size_t nSamples, std::size_t nChannels, int nAGC)
+{
+	if(nChannels == 1)
+	{
+		while(nSamples--)
+		{
+			int val = (int)(((int64)*pBuffer * (int32)nAGC) >> AGC_PRECISION);
+			if(val < MIXING_LIMITMIN || val > MIXING_LIMITMAX) nAGC--;
+			*pBuffer = val;
+			pBuffer++;
+		}
+	} else
+	{
+		if(nChannels == 2)
+		{
+			while(nSamples--)
+			{
+				int fl = (int)(((int64)pBuffer[0] * (int32)nAGC) >> AGC_PRECISION);
+				int fr = (int)(((int64)pBuffer[1] * (int32)nAGC) >> AGC_PRECISION);
+				bool dec = false;
+				dec = dec || (fl < MIXING_LIMITMIN || fl > MIXING_LIMITMAX);
+				dec = dec || (fr < MIXING_LIMITMIN || fr > MIXING_LIMITMAX);
+				if(dec) nAGC--;
+				pBuffer[0] = fl;
+				pBuffer[1] = fr;
+				pBuffer += 2;
+			}
+		} else if(nChannels == 4)
+		{
+			while(nSamples--)
+			{
+				int fl = (int)(((int64)pBuffer[0] * (int32)nAGC) >> AGC_PRECISION);
+				int fr = (int)(((int64)pBuffer[1] * (int32)nAGC) >> AGC_PRECISION);
+				int rl = (int)(((int64)pRearBuffer[0] * (int32)nAGC) >> AGC_PRECISION);
+				int rr = (int)(((int64)pRearBuffer[1] * (int32)nAGC) >> AGC_PRECISION);
+				bool dec = false;
+				dec = dec || (fl < MIXING_LIMITMIN || fl > MIXING_LIMITMAX);
+				dec = dec || (fr < MIXING_LIMITMIN || fr > MIXING_LIMITMAX);
+				dec = dec || (rl < MIXING_LIMITMIN || rl > MIXING_LIMITMAX);
+				dec = dec || (rr < MIXING_LIMITMIN || rr > MIXING_LIMITMAX);
+				if(dec) nAGC--;
+				pBuffer[0] = fl;
+				pBuffer[1] = fr;
+				pRearBuffer[0] = rl;
+				pRearBuffer[1] = rr;
+				pBuffer += 2;
+				pRearBuffer += 2;
+			}
+		}
+	}
+	return nAGC;
+}
+
+
+CAGC::CAGC()
+{
+	Initialize(true, 44100);
+}
+
+
+void CAGC::Process(int *MixSoundBuffer, int *RearSoundBuffer, std::size_t count, std::size_t nChannels)
+{
+	UINT agc = ProcessAGC(MixSoundBuffer, RearSoundBuffer, count, nChannels, m_nAGC);
+	// Some kind custom law, so that the AGC stays quite stable, but slowly
+	// goes back up if the sound level stays below a level inversely proportional
+	// to the AGC level. (J'me comprends)
+	if((agc >= m_nAGC) && (m_nAGC < AGC_UNITY))
+	{
+		m_nAGCRecoverCount += count;
+		if(m_nAGCRecoverCount >= m_Timeout)
+		{
+			m_nAGCRecoverCount = 0;
+			m_nAGC++;
+		}
+	} else
+	{
+		m_nAGC = agc;
+		m_nAGCRecoverCount = 0;
+	}
+}
+
+
+void CAGC::Adjust(UINT oldVol, UINT newVol)
+{
+	m_nAGC = m_nAGC * oldVol / newVol;
+	if (m_nAGC > AGC_UNITY) m_nAGC = AGC_UNITY;
+}
+
+
+void CAGC::Initialize(bool bReset, DWORD MixingFreq)
+{
+	if(bReset)
+	{
+		m_nAGC = AGC_UNITY;
+		m_nAGCRecoverCount = 0;
+	}
+	m_Timeout = (MixingFreq >> (AGC_PRECISION-8)) >> 1;
+}
+
+
+#else
+
+
+MPT_MSVC_WORKAROUND_LNK4221(AGC)
+
+
+#endif // NO_AGC
+
+
+OPENMPT_NAMESPACE_END
-- 
cgit