LowPassFilter< T > Class Template Reference

Second-order low-pass filter (BiQuad DF2). Attenuates frequencies above the cutoff frequency. Coefficients are derived from the Audio EQ Cookbook. More...

#include <Filter.h>

Inheritance diagram for LowPassFilter< T >:

Public Member Functions
	LowPassFilter ()=default
	LowPassFilter (float frequency, float sampleRate, float q=0.7071f)
void	begin (float frequency, float sampleRate, float q=0.7071f)
T	process (T value) override
	Processes the input value and returns the filtered output value.
void	reset () override

Protected Attributes
T	a_1 = 0
T	a_2 = 0
T	b_0 = 0
T	b_1 = 0
T	b_2 = 0
T	w_0 = 0
T	w_1 = 0

Detailed Description

template<typename T = float>
class audio_tools::LowPassFilter< T >

Second-order low-pass filter (BiQuad DF2). Attenuates frequencies above the cutoff frequency. Coefficients are derived from the Audio EQ Cookbook.

Parameters

frequency	cutoff frequency in Hz
sampleRate	sample rate in Hz
q	quality factor (default 0.7071 = Butterworth, no resonance peak)

Author

pschatzmann

Copyright

GNU General Public License v3.0

Template Parameters

T	sample type (use float or double; for fixed-point types like q1_14_t use LowPassFilterDF1 instead – DF2's single delay line needs much more dynamic range than the signal for low cutoff/sampleRate ratios and will saturate/misbehave in a bounded fixed-point type)

Constructor & Destructor Documentation

LowPassFilter() [1/2]

template<typename T = float>

LowPassFilter ( )

default

LowPassFilter() [2/2]

template<typename T = float>

LowPassFilter ( float  frequency, float  sampleRate, float  q = 0.7071f  )

inline

Member Function Documentation

begin()

template<typename T = float>

void begin ( float  frequency, float  sampleRate, float  q = 0.7071f  )

inline

process()

template<typename T = float>

T process ( T  in )

inlineoverridevirtualinherited

Processes the input value and returns the filtered output value.

Implements Filter< T >.

reset()

template<typename T = float>

void reset ( )

inlineoverridevirtualinherited

Clears the internal state (delay lines) without changing the coefficients. Call after reconfiguring filter parameters via begin() to avoid transients from stale state.

Reimplemented from Filter< T >.

Member Data Documentation

a_1

template<typename T = float>

T a_1 = 0

protectedinherited

a_2

template<typename T = float>

T a_2 = 0

protectedinherited

b_0

template<typename T = float>

T b_0 = 0

protectedinherited

b_1

template<typename T = float>

T b_1 = 0

protectedinherited

b_2

template<typename T = float>

T b_2 = 0

protectedinherited

w_0

template<typename T = float>

T w_0 = 0

protectedinherited

w_1

template<typename T = float>

T w_1 = 0

protectedinherited

---

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

• src/AudioTools/CoreAudio/AudioFilter/Filter.h