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https://github.com/cookiengineer/audacity
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80 lines
2.2 KiB
C++
80 lines
2.2 KiB
C++
/***************************************************/
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/*! \class DelayA
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\brief STK allpass interpolating delay line class.
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This Delay subclass implements a fractional-length digital
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delay-line using a first-order allpass filter. A fixed maximum
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length of 4095 and a delay of 0.5 is set using the default
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constructor. Alternatively, the delay and maximum length can be
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set during instantiation with an overloaded constructor.
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An allpass filter has unity magnitude gain but variable phase
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delay properties, making it useful in achieving fractional delays
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without affecting a signal's frequency magnitude response. In
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order to achieve a maximally flat phase delay response, the
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minimum delay possible in this implementation is limited to a
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value of 0.5.
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by Perry R. Cook and Gary P. Scavone, 1995 - 2005.
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*/
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/***************************************************/
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#ifndef STK_DELAYA_H
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#define STK_DELAYA_H
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#include "Delay.h"
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namespace Nyq
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{
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class DelayA : public Delay
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{
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public:
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//! Default constructor creates a delay-line with maximum length of 4095 samples and zero delay.
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DelayA();
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//! Overloaded constructor which specifies the current and maximum delay-line lengths.
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/*!
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An StkError will be thrown if the delay parameter is less than
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zero, the maximum delay parameter is less than one, or the delay
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parameter is greater than the maxDelay value.
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*/
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DelayA(StkFloat delay, unsigned long maxDelay);
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//! Class destructor.
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~DelayA();
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//! Clears the internal state of the delay line.
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void clear();
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//! Set the delay-line length
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/*!
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The valid range for \e theDelay is from 0.5 to the maximum delay-line length.
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*/
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void setDelay(StkFloat delay);
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//! Return the current delay-line length.
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StkFloat getDelay(void) const;
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//! Return the value which will be output by the next call to tick().
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/*!
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This method is valid only for delay settings greater than zero!
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*/
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StkFloat nextOut(void);
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protected:
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StkFloat computeSample( StkFloat input );
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StkFloat alpha_;
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StkFloat coeff_;
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StkFloat apInput_;
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StkFloat nextOutput_;
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bool doNextOut_;
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};
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} // namespace Nyq
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#endif
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