1 files changed, 81 insertions, 0 deletions
diff --git a/plugins/gme/game-music-emu-0.6pre/gme/SPC_Filter.cpp b/plugins/gme/game-music-emu-0.6pre/gme/SPC_Filter.cpp
new file mode 100644
index 00000000..4e5d8f60
--- /dev/null
+++ b/plugins/gme/game-music-emu-0.6pre/gme/SPC_Filter.cpp
@@ -0,0 +1,81 @@
+// snes_spc 0.9.0. http://www.slack.net/~ant/
+
+#include "Spc_Filter.h"
+
+/* Copyright (C) 2007 Shay Green. This module is free software; you
+can redistribute it and/or modify it under the terms of the GNU Lesser
+General Public License as published by the Free Software Foundation; either
+version 2.1 of the License, or (at your option) any later version. This
+module is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
+details. You should have received a copy of the GNU Lesser General Public
+License along with this module; if not, write to the Free Software Foundation,
+Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */
+
+#include "blargg_source.h"
+
+void SPC_Filter::clear() { memset( ch, 0, sizeof ch ); }
+
+SPC_Filter::SPC_Filter()
+{
+	enabled = true;
+	gain    = gain_unit;
+	bass    = bass_norm;
+	clear();
+}
+
+void SPC_Filter::run( short io [], int count )
+{
+	require( (count & 1) == 0 ); // must be even
+	
+	int const gain = this->gain;
+	if ( enabled )
+	{
+		int const bass = this->bass;
+		chan_t* c = &ch [2];
+		do
+		{
+			// cache in registers
+			int sum = (--c)->sum;
+			int pp1 = c->pp1;
+			int p1  = c->p1;
+			
+			for ( int i = 0; i < count; i += 2 )
+			{
+				// Low-pass filter (two point FIR with coeffs 0.25, 0.75)
+				int f = io [i] + p1;
+				p1 = io [i] * 3;
+				
+				// High-pass filter ("leaky integrator")
+				int delta = f - pp1;
+				pp1 = f;
+				int s = sum >> (gain_bits + 2);
+				sum += (delta * gain) - (sum >> bass);
+				
+				// Clamp to 16 bits
+				if ( (short) s != s )
+					s = (s >> 31) ^ 0x7FFF;
+				
+				io [i] = (short) s;
+			}
+			
+			c->p1  = p1;
+			c->pp1 = pp1;
+			c->sum = sum;
+			++io;
+		}
+		while ( c != ch );
+	}
+	else if ( gain != gain_unit )
+	{
+		short* const end = io + count;
+		while ( io < end )
+		{
+			int s = (*io * gain) >> gain_bits;
+			if ( (short) s != s )
+				s = (s >> 31) ^ 0x7FFF;
+			*io++ = (short) s;
+		}
+	}
+}