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/*
* $Id$
*
* ***** BEGIN LGPL LICENSE BLOCK *****
*
* Copyright 2009 Jörg Hermann Müller
*
* This file is part of AudaSpace.
*
* AudaSpace 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 3 of the License, or
* (at your option) any later version.
*
* AudaSpace 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 AudaSpace. If not, see <http://www.gnu.org/licenses/>.
*
* ***** END LGPL LICENSE BLOCK *****
*/
#include "AUD_ButterworthReader.h"
#include "AUD_Buffer.h"
#include <cstring>
#include <cmath>
#ifndef M_PI
#define M_PI 3.14159265358979323846
#endif
#define BWPB41 0.76536686473
#define BWPB42 1.84775906502
#define CC channels + channel
AUD_ButterworthReader::AUD_ButterworthReader(AUD_IReader* reader,
float frequency) :
AUD_EffectReader(reader)
{
AUD_Specs specs = reader->getSpecs();
int samplesize = AUD_SAMPLE_SIZE(specs);
m_buffer = new AUD_Buffer(); AUD_NEW("buffer")
m_outvalues = new AUD_Buffer(samplesize * 5); AUD_NEW("buffer")
memset(m_outvalues->getBuffer(), 0, samplesize * 5);
m_invalues = new AUD_Buffer(samplesize * 5); AUD_NEW("buffer")
memset(m_invalues->getBuffer(), 0, samplesize * 5);
m_position = 0;
// calculate coefficients
float omega = 2 * tan(frequency * M_PI / specs.rate);
float o2 = omega * omega;
float o4 = o2 * o2;
float x1 = o2 + 2 * BWPB41 * omega + 4;
float x2 = o2 + 2 * BWPB42 * omega + 4;
float y1 = o2 - 2 * BWPB41 * omega + 4;
float y2 = o2 - 2 * BWPB42 * omega + 4;
float o228 = 2 * o2 - 8;
float norm = x1 * x2;
m_coeff[0][0] = 0;
m_coeff[0][1] = (x1 + x2) * o228 / norm;
m_coeff[0][2] = (x1 * y2 + x2 * y1 + o228 * o228) / norm;
m_coeff[0][3] = (y1 + y2) * o228 / norm;
m_coeff[0][4] = y1 * y2 / norm;
m_coeff[1][4] = m_coeff[1][0] = o4 / norm;
m_coeff[1][3] = m_coeff[1][1] = 4 * o4 / norm;
m_coeff[1][2] = 6 * o4 / norm;
}
AUD_ButterworthReader::~AUD_ButterworthReader()
{
delete m_buffer; AUD_DELETE("buffer")
delete m_outvalues; AUD_DELETE("buffer")
delete m_invalues; AUD_DELETE("buffer");
}
void AUD_ButterworthReader::read(int & length, sample_t* & buffer)
{
sample_t* buf;
sample_t* outvalues;
sample_t* invalues;
outvalues = m_outvalues->getBuffer();
invalues = m_invalues->getBuffer();
AUD_Specs specs = m_reader->getSpecs();
m_reader->read(length, buf);
if(m_buffer->getSize() < length * AUD_SAMPLE_SIZE(specs))
m_buffer->resize(length * AUD_SAMPLE_SIZE(specs));
buffer = m_buffer->getBuffer();
int channels = specs.channels;
for(int channel = 0; channel < channels; channel++)
{
for(int i = 0; i < length; i++)
{
invalues[m_position * CC] = buf[i * CC];
outvalues[m_position * CC] = 0;
for(int j = 0; j < 4; j++)
{
outvalues[m_position * CC] += m_coeff[1][j] *
invalues[((m_position + j) % 5) * CC] -
m_coeff[0][j] *
outvalues[((m_position + j) % 5) * CC];
}
buffer[i * CC] = outvalues[m_position * CC];
m_position = (m_position + 4) % 5;
}
}
}
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