sfFDN::SignalDependentFractionalDelay Class Reference

A signal-dependent fractional delay filter. More...

#include <nonlinear.h>

Inheritance diagram for sfFDN::SignalDependentFractionalDelay:

Collaboration diagram for sfFDN::SignalDependentFractionalDelay:

Public Member Functions
	SignalDependentFractionalDelay (const SignalDependentFractionalDelayOptions &options={})
	Constructs a signal-dependent fractional delay.
void	SetD (float d)
	Sets the interpolation weight.
float	GetD () const noexcept SFFDN_NONBLOCKING
	Returns the interpolation weight.
float	Tick (float input) noexcept SFFDN_NONBLOCKING
	Processes a single sample.
void	Process (const AudioBuffer &input, AudioBuffer &output) noexcept SFFDN_NONBLOCKING override
	Processes the audio buffer.
uint32_t	InputChannelCount () const noexcept SFFDN_NONBLOCKING override
	Returns the number of input channels this processor expects.
uint32_t	OutputChannelCount () const noexcept SFFDN_NONBLOCKING override
	Returns the number of output channels this processor produces.
void	Clear () override
	Clears the delay state.
std::unique_ptr< AudioProcessor >	Clone () const override
	Creates a copy of the processor.
Public Member Functions inherited from sfFDN::AudioProcessor

Additional Inherited Members
Protected Member Functions inherited from sfFDN::AudioProcessor
	AudioProcessor (const AudioProcessor &)=default
AudioProcessor &	operator= (const AudioProcessor &)=default
	AudioProcessor (AudioProcessor &&) noexcept=default
AudioProcessor &	operator= (AudioProcessor &&) noexcept=default

Detailed Description

A signal-dependent fractional delay filter.

Implements the filter of Fig. 5 of the paper, after J. R. Pierce and S. A. Van Duyne, "A passive nonlinear digital filter design which facilitates physics-based sound synthesis of highly nonlinear musical instruments", J. Acoust. Soc. Amer., 1997, and V. Välimäki, T. Tolonen and M. Karjalainen, "Signal-dependent nonlinearities for physical models using time-varying fractional delay filters", Proc. ICMC, 1998.

The input is split into its positive and negative half-wave rectified components, each is delayed by a different fractional amount, and the two are summed:

\[ p(n) = \max(x(n), 0), \qquad q(n) = \min(x(n), 0), \\ y(n) = d\,q(n) + (1 - d)\,q(n-1) + d\,p(n-2) + (1 - d)\,p(n-1). \]

The two interpolators are linear and carry complementary weights, so the positive component is delayed by \(1 + d\) samples and the negative one by \(1 - d\). The result keeps the fundamental and the overall amplitude of a sinusoidal input but distorts it around its zero crossings, generating even harmonics. It is a milder effect than ControllableFullWaveRectifier, and a good alternative to it on sustained input.

Note

The delayed positive and negative components overlap by up to one sample, so a zero-mean periodic signal can lose up to one sample of energy per period. The operation is therefore slightly lossy rather than strictly energy preserving, and the loss grows with frequency. It does not endanger the stability of the enclosing network. It needs no dc blocker.

Constructor & Destructor Documentation

SignalDependentFractionalDelay()

sfFDN::SignalDependentFractionalDelay::SignalDependentFractionalDelay ( const SignalDependentFractionalDelayOptions & options = {} )

explicit

Constructs a signal-dependent fractional delay.

Parameters

options

The configuration options.

Exceptions

std::invalid_argument

if d is not in [0, 1].

Member Function Documentation

Clear()

void sfFDN::SignalDependentFractionalDelay::Clear ( )

overridevirtual

Clears the delay state.

The interpolation weight is left untouched.

Implements sfFDN::AudioProcessor.

Clone()

std::unique_ptr< AudioProcessor > sfFDN::SignalDependentFractionalDelay::Clone ( ) const

overridevirtual

Creates a copy of the processor.

The delay state is carried over.

Implements sfFDN::AudioProcessor.

InputChannelCount()

uint32_t sfFDN::SignalDependentFractionalDelay::InputChannelCount ( ) const

overridevirtualnoexcept

Returns the number of input channels this processor expects.

This is always 1.

Implements sfFDN::AudioProcessor.

OutputChannelCount()

uint32_t sfFDN::SignalDependentFractionalDelay::OutputChannelCount ( ) const

overridevirtualnoexcept

Returns the number of output channels this processor produces.

This is always 1.

Implements sfFDN::AudioProcessor.

Process()

void sfFDN::SignalDependentFractionalDelay::Process ( const AudioBuffer & input, AudioBuffer & output )

overridevirtualnoexcept

Processes the audio buffer.

Note

The input and output buffers must have one channel and the same number of samples.

Implements sfFDN::AudioProcessor.

SetD()

void sfFDN::SignalDependentFractionalDelay::SetD

(

float

d

)

Sets the interpolation weight.

Parameters

d	The interpolation weight, in [0, 1].

Exceptions

std::invalid_argument

if d is not in [0, 1].

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The documentation for this class was generated from the following file:

• include/sffdn/nonlinear.h