TTAllpass2b.cpp

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/** @file
 *
 * @ingroup dspFilterLib
 *
 * @brief #TTAllpass2b is a second-order allpass filter.
 *
 * @details A second-order Z^2 building-block allpass filter.
 *  This allpass filter uses a fixed delay of 2 samples (M=2). *
 *
 * @authors Timothy Place, Trond Lossius
 *
 * @copyright Copyright © 2010, Timothy Place @n
 * This code is licensed under the terms of the "New BSD License" @n
 * http://creativecommons.org/licenses/BSD/
 */


#include "TTAllpass2b.h"

#define thisTTClass         TTAllpass2b
#define thisTTClassName     "allpass.2b"
#define thisTTClassTags     "dspFilterLib, audio, processor, filter, allpass"

#ifdef TT_PLATFORM_WIN
#include <Algorithm>
#endif

TT_AUDIO_CONSTRUCTOR,
    mC1(0),
    mC2(0)
{
    TTChannelCount initialMaxNumChannels = arguments;

    addAttribute(C1, kTypeFloat64);
    addAttribute(C2, kTypeFloat64);
    
    addMessage(clear);
    addUpdates(MaxNumChannels);

    setAttributeValue(kTTSym_maxNumChannels,    initialMaxNumChannels);
    setProcessMethod(processAudio);
}


TTAllpass2b::~TTAllpass2b()
{
    ;
}


TTErr TTAllpass2b::updateMaxNumChannels(const TTValue& oldMaxNumChannels, TTValue&)
{
    mX1.resize(mMaxNumChannels);
    mX2.resize(mMaxNumChannels);
    mX3.resize(mMaxNumChannels);
    mX4.resize(mMaxNumChannels);
    mY1.resize(mMaxNumChannels);
    mY2.resize(mMaxNumChannels);
    mY3.resize(mMaxNumChannels);
    mY4.resize(mMaxNumChannels);
    clear();
    return kTTErrNone;
}


TTErr TTAllpass2b::clear()
{
    mX1.assign(mMaxNumChannels, 0.0);
    mX2.assign(mMaxNumChannels, 0.0);
    mX3.assign(mMaxNumChannels, 0.0);
    mX4.assign(mMaxNumChannels, 0.0);
    mY1.assign(mMaxNumChannels, 0.0);
    mY2.assign(mMaxNumChannels, 0.0);
    mY3.assign(mMaxNumChannels, 0.0);
    mY4.assign(mMaxNumChannels, 0.0);
    return kTTErrNone;
}


TTErr TTAllpass2b::calculateValue(const TTFloat64& x, TTFloat64& y, TTPtrSizedInt channel)
{
    TTFloat64 w1 = mC1 * (mX2[channel] - mY2[channel]);
    TTFloat64 w2 = mC2 * (x - mY4[channel]);
    
    y = w1 + w2 + mX4[channel];

    TTZeroDenormal(y);
    
    mX4[channel] = mX3[channel];
    mY4[channel] = mY3[channel];
    mX3[channel] = mX2[channel];
    mY3[channel] = mY2[channel];
    mX2[channel] = mX1[channel];
    mY2[channel] = mY1[channel];
    mX1[channel] = x;
    mY1[channel] = y;
    return kTTErrNone;
}


TTErr TTAllpass2b::processAudio(TTAudioSignalArrayPtr inputs, TTAudioSignalArrayPtr outputs)
{
    TT_WRAP_CALCULATE_METHOD(calculateValue);
}