Audio delay line with feedback for comb filter, flange, chorus and short echo effects. More...

#include <AudioDelayFeedback.h>

Public Member Functions
	AudioDelayFeedback ()
	Constructor.

	AudioDelayFeedback (uint16_t delaytime_cells)
	Constructor. More...

	AudioDelayFeedback (uint16_t delaytime_cells, int8_t feedback_level)
	Constructor. More...

int16_t	next (int8_t input)
	Input a value to the delay and retrieve the signal in the delay line at the position delaytime_cells. More...

int16_t	next (int8_t input, uint16_t delaytime_cells)
	Input a value to the delay, retrieve the signal in the delay line at the position delaytime_cells, and add feedback from the output to the input. More...

int16_t	next (int8_t input, Q16n16 delaytime_cells)
	Input a value to the delay, retrieve the signal in the delay line at the interpolated fractional position delaytime_cells, and add feedback from the output to the input. More...

void	write (int8_t input)
	Input a value to the delay but don't change the delay time or retrieve the output signal. More...

void	writeFeedback (int8_t input)
	Input a value to the delay but don't advance the write position, change the delay time or retrieve the output signal. More...

void	write (int8_t input, uint16_t offset)
	Input a value to the delay at an offset from the current write position. More...

int16_t	read (Q16n16 delaytime_cells)
	Retrieve the signal in the delay line at the interpolated fractional position delaytime_cells. More...

int16_t	read ()
	Retrieve the signal in the delay line at the current stored delaytime_cells. More...

void	setDelayTimeCells (uint16_t delaytime_cells)
	Set delay time expressed in samples. More...

void	setDelayTimeCells (Q16n16 delaytime_cells)
	Set delay time expressed in samples, fractional Q16n16 for an interpolating delay. More...

void	setDelayTimeCells (float delaytime_cells)
	Set delay time expressed in samples, fractional float for an interpolating delay. More...

void	setFeedbackLevel (int8_t feedback_level)
	Set the feedback gain. More...

Detailed Description

template<uint16_t NUM_BUFFER_SAMPLES, int8_t INTERP_TYPE = LINEAR>
class AudioDelayFeedback< NUM_BUFFER_SAMPLES, INTERP_TYPE >

Audio delay line with feedback for comb filter, flange, chorus and short echo effects.

Template Parameters

NUM_BUFFER_SAMPLES is the length of the delay buffer in samples, and should be a power of two. The maximum delay length which will fit in an atmega328 is half that of a plain AudioDelay object, in this case 256 cells, or about 15 milliseconds. AudioDelayFeedback uses int16_t sized cells to accomodate the higher amplitude of direct input to the delay as well as the feedback, without losing precision. Output is only the delay line signal. If you want to mix the delay with the input, do it in your sketch. AudioDelayFeedback uses more processing and memory than a plain AudioDelay, but allows for more dramatic effects with feedback.

INTERP_TYPE a choice of LINEAR (default) or ALLPASS interpolation. LINEAR is better for sweeping delay times, ALLPASS may be better for reverb-like effects.

Definition at line 40 of file AudioDelayFeedback.h.

Constructor & Destructor Documentation

◆ AudioDelayFeedback() [1/2]

template<uint16_t NUM_BUFFER_SAMPLES, int8_t INTERP_TYPE = LINEAR>

AudioDelayFeedback< NUM_BUFFER_SAMPLES, INTERP_TYPE >::AudioDelayFeedback ( uint16_t delaytime_cells )

inline

Constructor.

Parameters

delaytime_cells delay time expressed in cells. For example, 128 cells delay at AUDIO_RATE 16384 would produce a time delay of 128/16384 = 0.0078125 s = 7.8 ms Put another way, num_cells = delay_seconds * AUDIO_RATE.

Definition at line 55 of file AudioDelayFeedback.h.

◆ AudioDelayFeedback() [2/2]

template<uint16_t NUM_BUFFER_SAMPLES, int8_t INTERP_TYPE = LINEAR>

AudioDelayFeedback< NUM_BUFFER_SAMPLES, INTERP_TYPE >::AudioDelayFeedback	(	uint16_t	delaytime_cells,
		int8_t	feedback_level
	)

inline

Constructor.

Parameters

delaytime_cells	delay time expressed in cells. For example, 128 cells delay at AUDIO_RATE 16384 would produce a time delay of 128/16384 = 0.0078125 s = 7.8 ms Put another way, num_cells = delay_seconds * AUDIO_RATE.
feedback_level	is the feedback level from -128 to 127 (representing -1 to 1).

Definition at line 65 of file AudioDelayFeedback.h.

Member Function Documentation

◆ next() [1/3]

template<uint16_t NUM_BUFFER_SAMPLES, int8_t INTERP_TYPE = LINEAR>

int16_t AudioDelayFeedback< NUM_BUFFER_SAMPLES, INTERP_TYPE >::next ( int8_t input )

inline

Input a value to the delay and retrieve the signal in the delay line at the position delaytime_cells.

Parameters

input the signal input.

Note: slower than next(int8_t input, uint16_t delaytime_cells)

Definition at line 75 of file AudioDelayFeedback.h.

◆ next() [2/3]

template<uint16_t NUM_BUFFER_SAMPLES, int8_t INTERP_TYPE = LINEAR>

int16_t AudioDelayFeedback< NUM_BUFFER_SAMPLES, INTERP_TYPE >::next	(	int8_t	input,
		uint16_t	delaytime_cells
	)

inline

Input a value to the delay, retrieve the signal in the delay line at the position delaytime_cells, and add feedback from the output to the input.

Parameters

input	the signal input.
delaytime_cells	indicates the delay time in terms of cells in the delay buffer. It doesn't change the stored internal value of _delaytime_cells.

Note: Timing: 4us

Definition at line 92 of file AudioDelayFeedback.h.

◆ next() [3/3]

template<uint16_t NUM_BUFFER_SAMPLES, int8_t INTERP_TYPE = LINEAR>

int16_t AudioDelayFeedback< NUM_BUFFER_SAMPLES, INTERP_TYPE >::next	(	int8_t	input,
		Q16n16	delaytime_cells
	)

inline

Input a value to the delay, retrieve the signal in the delay line at the interpolated fractional position delaytime_cells, and add feedback from the output to the input.

Parameters

input	the signal input.
delaytime_cells	is a fractional number to set the delay time in terms of cells or partial cells in the delay buffer. It doesn't change the stored internal value of _delaytime_cells.

Definition at line 117 of file AudioDelayFeedback.h.

◆ read() [1/2]

template<uint16_t NUM_BUFFER_SAMPLES, int8_t INTERP_TYPE = LINEAR>

int16_t AudioDelayFeedback< NUM_BUFFER_SAMPLES, INTERP_TYPE >::read ( Q16n16 delaytime_cells )

inline

Retrieve the signal in the delay line at the interpolated fractional position delaytime_cells.

It doesn't change the stored internal value of _delaytime_cells or feedback the output to the input.

Parameters

delaytime_cells indicates the delay time in terms of cells in the delay buffer.

Definition at line 186 of file AudioDelayFeedback.h.

◆ read() [2/2]

template<uint16_t NUM_BUFFER_SAMPLES, int8_t INTERP_TYPE = LINEAR>

int16_t AudioDelayFeedback< NUM_BUFFER_SAMPLES, INTERP_TYPE >::read ( )

inline

Retrieve the signal in the delay line at the current stored delaytime_cells.

It doesn't change the stored internal value of _delaytime_cells or feedback the output to the input.

Definition at line 196 of file AudioDelayFeedback.h.

◆ setDelayTimeCells() [1/3]

template<uint16_t NUM_BUFFER_SAMPLES, int8_t INTERP_TYPE = LINEAR>

void AudioDelayFeedback< NUM_BUFFER_SAMPLES, INTERP_TYPE >::setDelayTimeCells ( uint16_t delaytime_cells )

inline

Set delay time expressed in samples.

Parameters

delaytime_cells delay time expressed in cells, with each cell played per tick of AUDIO_RATE. For example, 128 cells delay at AUDIO_RATE would produce a time delay of 128/16384 = 0.0078125 s = 7.8 ms Put another way, num_cells = delay_seconds * AUDIO_RATE.

Definition at line 208 of file AudioDelayFeedback.h.

◆ setDelayTimeCells() [2/3]

template<uint16_t NUM_BUFFER_SAMPLES, int8_t INTERP_TYPE = LINEAR>

void AudioDelayFeedback< NUM_BUFFER_SAMPLES, INTERP_TYPE >::setDelayTimeCells ( Q16n16 delaytime_cells )

inline

Set delay time expressed in samples, fractional Q16n16 for an interpolating delay.

Parameters

delaytime_cells delay time expressed in cells, with each cell played per tick of AUDIO_RATE. For example, 128 cells delay at AUDIO_RATE would produce a time delay of 128/16384 = 0.0078125 s = 7.8 ms Put another way, num_cells = delay_seconds * AUDIO_RATE.

Definition at line 220 of file AudioDelayFeedback.h.

◆ setDelayTimeCells() [3/3]

template<uint16_t NUM_BUFFER_SAMPLES, int8_t INTERP_TYPE = LINEAR>

void AudioDelayFeedback< NUM_BUFFER_SAMPLES, INTERP_TYPE >::setDelayTimeCells ( float delaytime_cells )

inline

Set delay time expressed in samples, fractional float for an interpolating delay.

Parameters

delaytime_cells delay time expressed in cells, with each cell played per tick of AUDIO_RATE. For example, 128 cells delay at AUDIO_RATE would produce a time delay of 128/16384 = 0.0078125 s = 7.8 ms Put another way, num_cells = delay_seconds * AUDIO_RATE.

Definition at line 232 of file AudioDelayFeedback.h.

◆ setFeedbackLevel()

template<uint16_t NUM_BUFFER_SAMPLES, int8_t INTERP_TYPE = LINEAR>

void AudioDelayFeedback< NUM_BUFFER_SAMPLES, INTERP_TYPE >::setFeedbackLevel ( int8_t feedback_level )

inline

Set the feedback gain.

Parameters

feedback_level is the feedback level from -128 to 127 (representing -1 to 1).

Definition at line 242 of file AudioDelayFeedback.h.

◆ write() [1/2]

template<uint16_t NUM_BUFFER_SAMPLES, int8_t INTERP_TYPE = LINEAR>

void AudioDelayFeedback< NUM_BUFFER_SAMPLES, INTERP_TYPE >::write ( int8_t input )

inline

Input a value to the delay but don't change the delay time or retrieve the output signal.

Parameters

input the signal input.

Definition at line 150 of file AudioDelayFeedback.h.

◆ write() [2/2]

template<uint16_t NUM_BUFFER_SAMPLES, int8_t INTERP_TYPE = LINEAR>

void AudioDelayFeedback< NUM_BUFFER_SAMPLES, INTERP_TYPE >::write	(	int8_t	input,
		uint16_t	offset
	)

inline

Input a value to the delay at an offset from the current write position.

Don't advance the main write position or change the stored delay time or retrieve the output signal.

Parameters

input	the signal input.
offset	the number of cells behind the ordinary write position where the input will be written.

Definition at line 174 of file AudioDelayFeedback.h.

◆ writeFeedback()

template<uint16_t NUM_BUFFER_SAMPLES, int8_t INTERP_TYPE = LINEAR>

void AudioDelayFeedback< NUM_BUFFER_SAMPLES, INTERP_TYPE >::writeFeedback ( int8_t input )

inline

Input a value to the delay but don't advance the write position, change the delay time or retrieve the output signal.

This can be useful for manually adding feedback to the delay line, "behind" the advancing write head.

Parameters

input the signal input.

Definition at line 162 of file AudioDelayFeedback.h.

Public Member Functions

Detailed Description

template<uint16_t NUM_BUFFER_SAMPLES, int8_t INTERP_TYPE = LINEAR> class AudioDelayFeedback< NUM_BUFFER_SAMPLES, INTERP_TYPE >

Constructor & Destructor Documentation

◆ AudioDelayFeedback() [1/2]

◆ AudioDelayFeedback() [2/2]

Member Function Documentation

◆ next() [1/3]

◆ next() [2/3]

◆ next() [3/3]

◆ read() [1/2]

◆ read() [2/2]

◆ setDelayTimeCells() [1/3]

◆ setDelayTimeCells() [2/3]

◆ setDelayTimeCells() [3/3]

◆ setFeedbackLevel()

◆ write() [1/2]

◆ write() [2/2]

◆ writeFeedback()

template<uint16_t NUM_BUFFER_SAMPLES, int8_t INTERP_TYPE = LINEAR>
class AudioDelayFeedback< NUM_BUFFER_SAMPLES, INTERP_TYPE >