TTAllpass1.h

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/** @file
 *
 * @ingroup dspFilterLib
 *
 * @brief #TTAllpass1 is a first order allpass filter
 *
 * @details
 *
 * @authors Timothy Place, Trond Lossius
 *
 * @copyright Copyright © 2003, Timothy Place @n
 * This code is licensed under the terms of the "New BSD License" @n
 * http://creativecommons.org/licenses/BSD/
 */


#ifndef __TT_ALLPASS1_H__
#define __TT_ALLPASS1_H__

#include "TTDSP.h"
#include "TTDelayBuffer.h"


/** An allpass filter. */
class TTAllpass1 : public TTAudioObjectBase {
    TTCLASS_SETUP(TTAllpass1)

protected:

    TTFloat64           mDelay;             ///< Attribute: delay time in milliseconds
    TTFloat64           mDelayMax;          ///< Maximum delay time in milliseconds (how long is the buffer?)
    TTUInt32            mDelayInSamples;    ///< Delay time in samples (internal)       
    TTUInt32            mDelayMaxInSamples; ///< size of the delay buffers
    TTFloat64           mGain;              ///< Attribute: gain in db
    TTFloat64           mLinearGain;        ///< Attribute: linear gain coefficient

    TTDelayBufferVector mFeedforward;       ///< ff buffers for each channel
    TTDelayBufferVector mFeedback;          ///< fb buffers for each channel
    
    
    // Notifications
    TTErr updateMaxNumChannels(const TTValue& oldMaxNumChannels, TTValue&);
    TTErr updateSampleRate(const TTValue& oldSampleRate, TTValue&);

    /** Internal initialization of buffers and pointers etc. */
    TTErr init(TTUInt64 newDelayMaxInSamples);
    
    // internal - position the buffer pointers
    void reset();

    
    /** Attribute accessor. */
    TTErr setDelay(const TTValue& newValue);

    /** Attribute Accessor */
    TTErr setDelayInSamples(const TTValue& newValue);
    
    /** Attribute Accessor */
    TTErr setDelayMax(const TTValue& newValue);
    
    /** Attribute Accessor */
    TTErr setDelayMaxInSamples(const TTValue& newValue);
    
    /** Attribute accessor. */
    TTErr setGain(const TTValue& newValue);
    
    /** Attribute accessor. */
    TTErr setLinearGain(const TTValue& newValue);
    
    /** This algorithm uses an IIR filter, meaning that it relies on feedback.  If the filter should
     *  not be producing any signal (such as turning audio off and then back on in a host) or if the
     *  feedback has become corrupted (such as might happen if a NaN is fed in) then it may be 
     *  neccesary to clear the filter by calling this method.
     *  @return Returns a TTErr error code.                                             */
    TTErr clear();
    

    TTErr calculateValue(const TTFloat64& x, TTFloat64& y, TTDelayBufferPtr* data);
    TTErr processAudio(TTAudioSignalArrayPtr inputs, TTAudioSignalArrayPtr outputs);

    /** Unit Tests  
     @param returnedTestInfo        Used to return test information
     @return                        #TTErr error code if the method fails to execute, else #kTTErrNone.
     */
    virtual TTErr test(TTValue& returnedTestInfo);  
};


#endif // __TT_ALLPASS1_H__