libavcodec/iirfilter.c File Reference

different IIR filters implementation More...

#include "iirfilter.h"
#include <complex.h>
#include <math.h>

Go to the source code of this file.

Data Structures
struct	FFIIRFilterCoeffs
	IIR filter global parameters. More...
struct	FFIIRFilterState
	IIR filter state. More...
Defines
#define	MAXORDER   30
	maximum supported filter order
#define	FILTER(i0, i1, i2, i3)
Functions
struct FFIIRFilterCoeffs *	ff_iir_filter_init_coeffs (enum IIRFilterType filt_type, enum IIRFilterMode filt_mode, int order, float cutoff_ratio, float stopband, float ripple)
	Initialize filter coefficients.
struct FFIIRFilterState *	ff_iir_filter_init_state (int order)
	Create new filter state.
void	ff_iir_filter (const struct FFIIRFilterCoeffs *c, struct FFIIRFilterState *s, int size, const int16_t *src, int sstep, int16_t *dst, int dstep)
	Perform lowpass filtering on input samples.
void	ff_iir_filter_free_state (struct FFIIRFilterState *state)
	Free filter state.
void	ff_iir_filter_free_coeffs (struct FFIIRFilterCoeffs *coeffs)
	Free filter coefficients.

---

Detailed Description

different IIR filters implementation

Definition in file iirfilter.c.

---

Define Documentation

#define FILTER	(	i0,
		i1,
		i2,
		i3		)

Value:

in =   *src * c->gain                         \
         + c->cy[0]*s->x[i0] + c->cy[1]*s->x[i1]  \
         + c->cy[2]*s->x[i2] + c->cy[3]*s->x[i3]; \
    res =  (s->x[i0] + in      )*1                \
         + (s->x[i1] + s->x[i3])*4                \
         +  s->x[i2]            *6;               \
    *dst = av_clip_int16(lrintf(res));            \
    s->x[i0] = in;                                \
    src += sstep;                                 \
    dst += dstep;                                 \

Definition at line 106 of file iirfilter.c.

#define MAXORDER   30

maximum supported filter order

Definition at line 49 of file iirfilter.c.

Referenced by ff_iir_filter_init_coeffs().

---

Function Documentation

void ff_iir_filter	(	const struct FFIIRFilterCoeffs *	coeffs,
		struct FFIIRFilterState *	state,
		int	size,
		const int16_t *	src,
		int	sstep,
		int16_t *	dst,
		int	dstep
	)

Perform lowpass filtering on input samples.

Parameters:

	coeffs	pointer to filter coefficients
	state	pointer to filter state
	size	input length
	src	source samples
	sstep	source stride
	dst	filtered samples (destination may be the same as input)
	dstep	destination stride

Definition at line 118 of file iirfilter.c.

void ff_iir_filter_free_coeffs

(

struct FFIIRFilterCoeffs *

coeffs

)

Free filter coefficients.

Parameters:

coeffs

pointer allocated with ff_iir_filter_init_coeffs()

Definition at line 156 of file iirfilter.c.

void ff_iir_filter_free_state

(

struct FFIIRFilterState *

state

)

Free filter state.

Parameters:

state

pointer allocated with ff_iir_filter_init_state()

Definition at line 151 of file iirfilter.c.

struct FFIIRFilterCoeffs* ff_iir_filter_init_coeffs	(	enum IIRFilterType	filt_type,
		enum IIRFilterMode	filt_mode,
		int	order,
		float	cutoff_ratio,
		float	stopband,
		float	ripple
	)			[read]

Initialize filter coefficients.

Parameters:

	filt_type	filter type (e.g. Butterworth)
	filt_mode	filter mode (e.g. lowpass)
	order	filter order
	cutoff_ratio	cutoff to input frequency ratio
	stopband	stopband to input frequency ratio (used by bandpass and bandstop filter modes)
	ripple	ripple factor (used only in Chebyshev filters)

Returns:

pointer to filter coefficients structure or NULL if filter cannot be created

Definition at line 51 of file iirfilter.c.

struct FFIIRFilterState* ff_iir_filter_init_state

(

int

order

)

[read]

Create new filter state.

Parameters:

order

filter order

Returns:

pointer to new filter state or NULL if state creation fails

Definition at line 100 of file iirfilter.c.