HighShelfFilter< T > Class Template Reference

Second-order high-shelf filter (BiQuad DF2). Boosts or cuts frequencies above the shelf frequency by the specified gain (in dB) while leaving lower frequencies unchanged. Commonly used in tone controls and equalization. Coefficients are derived from the Audio EQ Cookbook. More...

#include <Filter.h>

Inheritance diagram for HighShelfFilter< T >:

Public Member Functions
	HighShelfFilter ()=default
	HighShelfFilter (float frequency, float sampleRate, float gain, float slope=1.0f)
void	begin (float frequency, float sampleRate, float gain, float slope=1.0f)
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::HighShelfFilter< T >

Second-order high-shelf filter (BiQuad DF2). Boosts or cuts frequencies above the shelf frequency by the specified gain (in dB) while leaving lower frequencies unchanged. Commonly used in tone controls and equalization. Coefficients are derived from the Audio EQ Cookbook.

Parameters

frequency	shelf transition frequency in Hz
sampleRate	sample rate in Hz
gain	boost/cut in dB (positive = boost, negative = cut)
slope	shelf slope (default 1.0; values < 1.0 give a gentler slope)

Author

pschatzmann

Copyright

GNU General Public License v3.0

Template Parameters

T

sample type (use float or double). NOTE: q1_14_t (or any fixed-point type with only ~1 bit of headroom above +-1.0) does not work here – HighShelfFilterDF1 does NOT fix this the way it fixes the other filters. Its coefficients scale with the linear gain factor 10^(gain_dB/40) and, for a low shelf frequency relative to sampleRate, already exceed a q1_14_t-sized range at just +1dB of gain (measured, not a theoretical edge case). begin() logs an error (LOGE) via checkCoeffRange() when this happens.

Constructor & Destructor Documentation

HighShelfFilter() [1/2]

template<typename T = float>

HighShelfFilter ( )

default

HighShelfFilter() [2/2]

template<typename T = float>

HighShelfFilter ( float  frequency, float  sampleRate, float  gain, float  slope = 1.0f  )

inline

Member Function Documentation

begin()

template<typename T = float>

void begin ( float  frequency, float  sampleRate, float  gain, float  slope = 1.0f  )

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

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

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