File syn_biquad.h¶

FileList > dsp > syn_biquad.h

Fixed-point Q16.16 Biquad filter (Direct Form I).

#include "../common/syn_defs.h"
#include "../util/syn_qmath.h"

Classes¶

Type	Name
struct	SYN_FilterBiquad Fixed-point Q16.16 Biquad filter state (Direct Form I).
struct	SYN_FilterBiquadCascade Multi-stage cascaded biquad filter structure for high-order filtering.

Public Functions¶

Type	Name
void	syn_filter_biquad_bandpass (SYN_FilterBiquad * f, q16_t fc, q16_t fs, q16_t q) Initialize a biquad bandpass filter.
SYN_Status	syn_filter_biquad_cascade_init (SYN_FilterBiquadCascade * c, uint8_t num_stages) Initialize a cascaded biquad filter structure.
void	syn_filter_biquad_cascade_process_block (SYN_FilterBiquadCascade * c, const q16_t * in, q16_t * out, uint16_t count) Process a block of samples through all active biquad stages.
void	syn_filter_biquad_cascade_reset (SYN_FilterBiquadCascade * c) Reset all delay lines across all stages in the biquad cascade.
q16_t	syn_filter_biquad_cascade_update (SYN_FilterBiquadCascade * c, q16_t sample) Process a single sample sequentially through all active biquad stages.
void	syn_filter_biquad_highpass (SYN_FilterBiquad * f, q16_t fc, q16_t fs) Initialize a biquad highpass filter.
void	syn_filter_biquad_init (SYN_FilterBiquad * f, q16_t b0, q16_t b1, q16_t b2, q16_t a1, q16_t a2) Initialize a biquad filter with raw coefficients.
void	syn_filter_biquad_lowpass (SYN_FilterBiquad * f, q16_t fc, q16_t fs) Initialize a biquad lowpass filter.
void	syn_filter_biquad_notch (SYN_FilterBiquad * f, q16_t fc, q16_t fs, q16_t q) Initialize a biquad notch (band-reject) filter.
void	syn_filter_biquad_process_block (SYN_FilterBiquad * f, const q16_t * in, q16_t * out, uint16_t count) Process a block of samples through the biquad filter.
void	syn_filter_biquad_reset (SYN_FilterBiquad * f) Reset biquad filter delay lines to zero.
q16_t	syn_filter_biquad_update (SYN_FilterBiquad * f, q16_t sample) Process a single sample through the biquad filter.

Macros¶

Type	Name
define	SYN_BIQUAD_CASCADE_MAX_STAGES `8`

Public Functions Documentation¶

function syn_filter_biquad_bandpass¶

Initialize a biquad bandpass filter.

void syn_filter_biquad_bandpass (
    SYN_FilterBiquad * f,
    q16_t fc,
    q16_t fs,
    q16_t q
)

Constant-skirt-gain bandpass. Peak gain = 1.0 at center frequency.

Parameters:

f Filter instance.
fc Center frequency (Hz) in Q16.16.
fs Sample rate (Hz) in Q16.16.
q Quality factor in Q16.16 (higher = narrower band).

function syn_filter_biquad_cascade_init¶

Initialize a cascaded biquad filter structure.

SYN_Status syn_filter_biquad_cascade_init (
    SYN_FilterBiquadCascade * c,
    uint8_t num_stages
)

Parameters:

c Cascade instance.
num_stages Number of active biquad stages (1 to SYN_BIQUAD_CASCADE_MAX_STAGES).

Returns:

SYN_OK on success.

function syn_filter_biquad_cascade_process_block¶

Process a block of samples through all active biquad stages.

void syn_filter_biquad_cascade_process_block (
    SYN_FilterBiquadCascade * c,
    const q16_t * in,
    q16_t * out,
    uint16_t count
)

Parameters:

c Cascade instance.
in Input sample array.
out Output sample array (may alias in).
count Number of samples to process.

function syn_filter_biquad_cascade_reset¶

Reset all delay lines across all stages in the biquad cascade.

void syn_filter_biquad_cascade_reset (
    SYN_FilterBiquadCascade * c
)

Parameters:

c Cascade instance.

function syn_filter_biquad_cascade_update¶

Process a single sample sequentially through all active biquad stages.

q16_t syn_filter_biquad_cascade_update (
    SYN_FilterBiquadCascade * c,
    q16_t sample
)

Parameters:

c Cascade instance.
sample Input sample in Q16.16.

Returns:

Filtered output in Q16.16.

function syn_filter_biquad_highpass¶

Initialize a biquad highpass filter.

void syn_filter_biquad_highpass (
    SYN_FilterBiquad * f,
    q16_t fc,
    q16_t fs
)

Computes standard Butterworth highpass coefficients in Q16.16.

Parameters:

f Filter instance.
fc Cutoff frequency (Hz) in Q16.16.
fs Sample rate (Hz) in Q16.16.

function syn_filter_biquad_init¶

Initialize a biquad filter with raw coefficients.

void syn_filter_biquad_init (
    SYN_FilterBiquad * f,
    q16_t b0,
    q16_t b1,
    q16_t b2,
    q16_t a1,
    q16_t a2
)

Parameters:

f Filter instance.
b0 Feedforward coefficient b0 (Q16.16).
b1 Feedforward coefficient b1 (Q16.16).
b2 Feedforward coefficient b2 (Q16.16).
a1 Feedback coefficient a1 (Q16.16).
a2 Feedback coefficient a2 (Q16.16).

function syn_filter_biquad_lowpass¶

Initialize a biquad lowpass filter.

void syn_filter_biquad_lowpass (
    SYN_FilterBiquad * f,
    q16_t fc,
    q16_t fs
)

Computes standard Butterworth coefficients in Q16.16.

Parameters:

f Filter instance.
fc Cutoff frequency (Hz) in Q16.16.
fs Sample rate (Hz) in Q16.16.

function syn_filter_biquad_notch¶

Initialize a biquad notch (band-reject) filter.

void syn_filter_biquad_notch (
    SYN_FilterBiquad * f,
    q16_t fc,
    q16_t fs,
    q16_t q
)

Rejects frequencies near fc, passes all others.

Parameters:

f Filter instance.
fc Notch center frequency (Hz) in Q16.16.
fs Sample rate (Hz) in Q16.16.
q Quality factor in Q16.16 (higher = narrower notch).

function syn_filter_biquad_process_block¶

Process a block of samples through the biquad filter.

void syn_filter_biquad_process_block (
    SYN_FilterBiquad * f,
    const q16_t * in,
    q16_t * out,
    uint16_t count
)

Parameters:

f Biquad filter instance.
in Input sample array (n elements).
out Output sample array (n elements). May alias in.
count Number of samples to process.

function syn_filter_biquad_reset¶

Reset biquad filter delay lines to zero.

void syn_filter_biquad_reset (
    SYN_FilterBiquad * f
)

Parameters:

f Filter instance.

function syn_filter_biquad_update¶

Process a single sample through the biquad filter.

q16_t syn_filter_biquad_update (
    SYN_FilterBiquad * f,
    q16_t sample
)

Uses 64-bit intermediate calculations to prevent overflows.

Parameters:

f Biquad filter instance.
sample Input sample in Q16.16.

Returns:

Filtered output in Q16.16.

Macro Definition Documentation¶

define SYN_BIQUAD_CASCADE_MAX_STAGES¶

#define SYN_BIQUAD_CASCADE_MAX_STAGES `8`

The documentation for this class was generated from the following file src/syntropic/dsp/syn_biquad.h