AUD_EnvelopeFactory.cpp

Go to the documentation of this file.

/*
 * $Id: AUD_EnvelopeFactory.cpp 35141 2011-02-25 10:21:56Z jesterking $
 *
 * ***** BEGIN GPL LICENSE BLOCK *****
 *
 * Copyright 2009-2011 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 General Public License as published by
 * the Free Software Foundation; either version 2 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Audaspace; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * ***** END GPL LICENSE BLOCK *****
 */

#include "AUD_EnvelopeFactory.h"
#include "AUD_CallbackIIRFilterReader.h"

#include <cmath>

struct EnvelopeParameters
{
        float attack;
        float release;
        float threshold;
        float arthreshold;
};

sample_t envelopeFilter(AUD_CallbackIIRFilterReader* reader, EnvelopeParameters* param)
{
        float in = fabs(reader->x(0));
        float out = reader->y(-1);
        if(in < param->threshold)
                in = 0.0f;
        return (in > out ? param->attack : param->release) * (out - in) + in;
}

void endEnvelopeFilter(EnvelopeParameters* param)
{
        delete param;
}

AUD_EnvelopeFactory::AUD_EnvelopeFactory(AUD_IFactory* factory, float attack,
                                                                                 float release, float threshold,
                                                                                 float arthreshold) :
                AUD_EffectFactory(factory),
                m_attack(attack),
                m_release(release),
                m_threshold(threshold),
                m_arthreshold(arthreshold)
{
}

AUD_IReader* AUD_EnvelopeFactory::createReader() const
{
        AUD_IReader* reader = getReader();

        EnvelopeParameters* param = new EnvelopeParameters();
        param->arthreshold = m_arthreshold;
        param->attack = pow(m_arthreshold, 1.0f/(reader->getSpecs().rate * m_attack));
        param->release = pow(m_arthreshold, 1.0f/(reader->getSpecs().rate * m_release));
        param->threshold = m_threshold;

        return new AUD_CallbackIIRFilterReader(reader, 1, 2,
                                                                                   (doFilterIIR) envelopeFilter,
                                                                                   (endFilterIIR) endEnvelopeFilter,
                                                                                   param);
}