TTAllpass4a.cpp

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/** @file
 *
 * @ingroup dspFilterLib
 *
 * @brief #TTAllpass4a is a fourth-order allpass filter.
 *
 * @details Essentially the same as #TTAllpass2a, but with some signs flipped.
 *  Based on Fredric J. Harris (2004): Multirate Signal Processing for Communication Systems, Prentice Hall, Chapter 10, Figure 42.
 *
 *
 * @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 "TTAllpass4a.h"

#define thisTTClass         TTAllpass4a
#define thisTTClassName     "allpass.4a"
#define thisTTClassTags     "dspFilterLib, audio, processor, filter, allpass"

#ifdef TT_PLATFORM_WIN
#include <Algorithm>
#endif

TT_AUDIO_CONSTRUCTOR,
    mD1(0),
    mD2(0),
    mD3(0),
    mD4(0)
{
    TTChannelCount initialMaxNumChannels = arguments;

    addAttribute(D1, kTypeFloat64);
    addAttribute(D2, kTypeFloat64);
    addAttribute(D3, kTypeFloat64);
    addAttribute(D4, kTypeFloat64);
    
    addMessage(clear);
    addUpdates(MaxNumChannels);

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


TTAllpass4a::~TTAllpass4a()
{
    ;
}


TTErr TTAllpass4a::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 TTAllpass4a::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 TTAllpass4a::calculateValue(const TTFloat64& x, TTFloat64& y, TTPtrSizedInt channel)
{
    TTFloat64 w1 = mD1 * (mX3[channel] - mY1[channel]);
    TTFloat64 w2 = mD2 * (mX2[channel] - mY2[channel]);
    TTFloat64 w3 = mD3 * (mX1[channel] - mY3[channel]);
    TTFloat64 w4 = mD4 * (x            - mY4[channel]);
    
    y = w1 + w2 + w3 + w4 + mX4[channel];

    TTZeroDenormal(y);
    
    // TODO: Is there something faster that we can do below rather all of this copying?
    // If we could have a pointer that just incremented it seems like it would be faster
    // But then we need some clever bit twiddling to efficiently do the wrapping...
    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 TTAllpass4a::processAudio(TTAudioSignalArrayPtr inputs, TTAudioSignalArrayPtr outputs)
{
    TT_WRAP_CALCULATE_METHOD(calculateValue);
}