Merge pull request #578 from diizy/bandlimit

Bandlimited waveform generation

src/core/BandLimitedWave.cpp

@@ -0,0 +1,141 @@
+/*
+ * BandLimitedWave.h - helper functions for band-limited
+ *                    	waveform generation
+ *
+ * Copyright (c) 2014 Vesa Kivimäki <contact/dot/diizy/at/nbl/dot/fi>
+ *
+ * This file is part of Linux MultiMedia Studio - http://lmms.sourceforge.net
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This program 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
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public
+ * License along with this program (see COPYING); if not, write to the
+ * Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+ * Boston, MA 02110-1301 USA.
+ *
+ */
+
+#include "BandLimitedWave.h"
+
+
+WaveMipMap BandLimitedWave::s_waveforms[4] = {  };
+
+
+void BandLimitedWave::generateWaves()
+{
+	int i;
+
+// saw wave - BLSaw
+	for( i = 1; i <= MAXLEN; i++ )
+	{
+		const int len = 1 << i;
+		const double om = 1.0 / len;
+		double max = 0.0;
+		
+		for( int ph = 0; ph < len; ph++ )
+		{
+			int harm = 1;
+			double s = 0.0f;
+			do
+			{
+				const double amp = -1.0 / static_cast<double>( harm );
+				const double a2 = cos( om * harm * F_2PI );
+				s += amp * a2 * sin( static_cast<double>( ph * harm ) / static_cast<double>( len ) * F_2PI );
+				harm++;
+			} while( len/harm > 2 );
+			s_waveforms[ BandLimitedWave::BLSaw ].setSampleAt( i, ph, s );
+			max = qMax( max, qAbs( s ) );
+		}
+		// normalize
+		for( int ph = 0; ph < len; ph++ )
+		{
+			sample_t s = s_waveforms[ BandLimitedWave::BLSaw ].sampleAt( i, ph ) / max;
+			s_waveforms[ BandLimitedWave::BLSaw ].setSampleAt( i, ph, s );
+		}
+	}
+	
+// square wave - BLSquare
+	for( i = 1; i <= MAXLEN; i++ )
+	{
+		const int len = 1 << i;
+		const double om = 1.0 / len;
+		double max = 0.0;
+		
+		for( int ph = 0; ph < len; ph++ )
+		{
+			int harm = 1;
+			double s = 0.0f;
+			do
+			{
+				const double amp = 1.0 / static_cast<double>( harm );
+				const double a2 = cos( om * harm * F_2PI );
+				s += amp * a2 * sin( static_cast<double>( ph * harm ) / static_cast<double>( len ) * F_2PI );
+				harm += 2;
+			} while( len/harm > 2 );
+			s_waveforms[ BandLimitedWave::BLSquare ].setSampleAt( i, ph, s );
+			max = qMax( max, qAbs( s ) );
+		}
+		// normalize
+		for( int ph = 0; ph < len; ph++ )
+		{
+			sample_t s = s_waveforms[ BandLimitedWave::BLSquare ].sampleAt( i, ph ) / max;
+			s_waveforms[ BandLimitedWave::BLSquare ].setSampleAt( i, ph, s );
+		}
+	}
+
+
+// triangle wave - BLTriangle
+	for( i = 1; i <= MAXLEN; i++ )
+	{
+		const int len = 1 << i;
+		//const double om = 1.0 / len;
+		double max = 0.0;
+		
+		for( int ph = 0; ph < len; ph++ )
+		{
+			int harm = 1;
+			double s = 0.0f;
+			do
+			{
+				const double amp = 1.0 / static_cast<double>( harm * harm );
+				//const double a2 = cos( om * harm * F_2PI );
+				s += amp * /*a2 **/ sin( ( static_cast<double>( ph * harm ) / static_cast<double>( len ) + 
+						( ( harm + 1 ) % 4 == 0 ? 0.5 : 0.0 ) ) * F_2PI );
+				harm += 2;
+			} while( len/harm > 2 );
+			s_waveforms[ BandLimitedWave::BLTriangle ].setSampleAt( i, ph, s );
+			max = qMax( max, qAbs( s ) );
+		}
+		// normalize
+		for( int ph = 0; ph < len; ph++ )
+		{
+			sample_t s = s_waveforms[ BandLimitedWave::BLTriangle ].sampleAt( i, ph ) / max;
+			s_waveforms[ BandLimitedWave::BLTriangle ].setSampleAt( i, ph, s );
+		}
+	}
+	
+	
+// moog saw wave - BLMoog
+// basically, just add in triangle + 270-phase saw
+	for( i = 1; i <= MAXLEN; i++ )
+	{
+		const int len = 1 << i;
+		
+		for( int ph = 0; ph < len; ph++ )
+		{
+			const int sawph = ( ph + static_cast<int>( len * 0.75 ) ) % len;
+			const sample_t saw = s_waveforms[ BandLimitedWave::BLSaw ].sampleAt( i, sawph );
+			const sample_t tri = s_waveforms[ BandLimitedWave::BLTriangle ].sampleAt( i, ph );
+			s_waveforms[ BandLimitedWave::BLMoog ].setSampleAt( i, ph, ( saw + tri ) * 0.5f );
+		}
+	}
+	
+}

src/core/main.cpp

@@ -65,6 +65,7 @@
 #include "ProjectRenderer.h"
 #include "DataFile.h"
 #include "song.h"
+#include "BandLimitedWave.h"
 
 static inline QString baseName( const QString & _file )
 {
@@ -119,6 +120,8 @@ int main( int argc, char * * argv )
 			new QCoreApplication( argc, argv ) :
 					new QApplication( argc, argv ) ;
 
+	// generate bandlimited wavetables for instruments to use
+	BandLimitedWave::generateWaves();
 
 	Mixer::qualitySettings qs( Mixer::qualitySettings::Mode_HighQuality );
 	ProjectRenderer::OutputSettings os( 44100, false, 160,