1 files changed, 101 insertions, 0 deletions
diff --git a/gst/modplug/libmodplug/snd_flt.cpp b/gst/modplug/libmodplug/snd_flt.cpp
new file mode 100644
index 00000000..0865e597
--- /dev/null
+++ b/gst/modplug/libmodplug/snd_flt.cpp
@@ -0,0 +1,101 @@
+/*
+ * This source code is public domain.
+ *
+ * Authors: Olivier Lapicque <olivierl@jps.net>
+*/
+
+#include "stdafx.h"
+#include "sndfile.h"
+
+// AWE32: cutoff = reg[0-255] * 31.25 + 100 -> [100Hz-8060Hz]
+// EMU10K1 docs: cutoff = reg[0-127]*62+100
+#define FILTER_PRECISION	8192
+
+#ifndef NO_FILTER
+
+#ifdef MSC_VER
+#define _ASM_MATH
+#endif
+
+#ifdef _ASM_MATH
+
+// pow(a,b) returns a^^b -> 2^^(b.log2(a))
+static float pow(float a, float b)
+{
+	long tmpint;
+	float result;
+	_asm {
+	fld b				// Load b
+	fld a				// Load a
+	fyl2x				// ST(0) = b.log2(a)
+	fist tmpint			// Store integer exponent
+	fisub tmpint		// ST(0) = -1 <= (b*log2(a)) <= 1
+	f2xm1				// ST(0) = 2^(x)-1
+	fild tmpint			// load integer exponent
+	fld1				// Load 1
+	fscale				// ST(0) = 2^ST(1)
+	fstp ST(1)			// Remove the integer from the stack
+	fmul ST(1), ST(0)	// multiply with fractional part
+	faddp ST(1), ST(0)	// add integer_part
+	fstp result			// Store the result
+	}
+	return result;
+}
+
+
+#else
+
+#include <math.h>
+
+#endif // _ASM_MATH
+
+
+DWORD CSoundFile::CutOffToFrequency(UINT nCutOff, int flt_modifier) const
+//-----------------------------------------------------------------------
+{
+	float Fc;
+
+	if (m_dwSongFlags & SONG_EXFILTERRANGE)
+		Fc = 110.0f * pow(2.0f, 0.25f + ((float)(nCutOff*(flt_modifier+256)))/(21.0f*512.0f));
+	else
+		Fc = 110.0f * pow(2.0f, 0.25f + ((float)(nCutOff*(flt_modifier+256)))/(24.0f*512.0f));
+	LONG freq = (LONG)Fc;
+	if (freq < 120) return 120;
+	if (freq > 10000) return 10000;
+	if (freq*2 > (LONG)gdwMixingFreq) freq = gdwMixingFreq>>1;
+	return (DWORD)freq;
+}
+
+
+// Simple 2-poles resonant filter
+void CSoundFile::SetupChannelFilter(MODCHANNEL *pChn, BOOL bReset, int flt_modifier) const
+//----------------------------------------------------------------------------------------
+{
+	float fc = (float)CutOffToFrequency(pChn->nCutOff, flt_modifier);
+	float fs = (float)gdwMixingFreq;
+	float fg, fb0, fb1;
+
+	fc *= (float)(2.0*3.14159265358/fs);
+	float dmpfac = pow(10.0f, -((24.0f / 128.0f)*(float)pChn->nResonance) / 20.0f);
+	float d = (1.0f-2.0f*dmpfac)* fc;
+	if (d>2.0) d = 2.0;
+	d = (2.0f*dmpfac - d)/fc;
+	float e = pow(1.0f/fc,2.0);
+
+	fg=1/(1+d+e);
+	fb0=(d+e+e)/(1+d+e);
+	fb1=-e/(1+d+e);
+
+	pChn->nFilter_A0 = (int)(fg * FILTER_PRECISION);
+	pChn->nFilter_B0 = (int)(fb0 * FILTER_PRECISION);
+	pChn->nFilter_B1 = (int)(fb1 * FILTER_PRECISION);
+
+	if (bReset)
+	{
+		pChn->nFilter_Y1 = pChn->nFilter_Y2 = 0;
+		pChn->nFilter_Y3 = pChn->nFilter_Y4 = 0;
+	}
+	pChn->dwFlags |= CHN_FILTER;
+}
+
+#endif // NO_FILTER