iirfilter.c File Reference

different IIR filters implementation More...

#include <math.h>
#include "libavutil/attributes.h"
#include "libavutil/common.h"
#include "iirfilter.h"

Classes
struct	FFIIRFilterCoeffs
	IIR filter global parameters. More...
struct	FFIIRFilterState
	IIR filter state. More...

Macros
#define	MAXORDER   30
	maximum supported filter order
#define	CONV_S16(dest, source)   dest = av_clip_int16(lrintf(source));
#define	CONV_FLT(dest, source)   dest = source;
#define	FILTER_BW_O4_1(i0, i1, i2, i3, fmt)
#define	FILTER_BW_O4(type, fmt)
#define	FILTER_DIRECT_FORM_II(type, fmt)
#define	FILTER_O2(type, fmt)

Typedefs
typedef struct FFIIRFilterCoeffs	FFIIRFilterCoeffs
	IIR filter global parameters.
typedef struct FFIIRFilterState	FFIIRFilterState
	IIR filter state.

Functions
av_cold struct FFIIRFilterCoeffs *	ff_iir_filter_init_coeffs (void *avc, enum IIRFilterType filt_type, enum IIRFilterMode filt_mode, int order, float cutoff_ratio, float stopband, float ripple)
	Initialize filter coefficients. More...
av_cold struct FFIIRFilterState *	ff_iir_filter_init_state (int order)
	Create new filter state. More...
void	ff_iir_filter (const struct FFIIRFilterCoeffs *c, struct FFIIRFilterState *s, int size, const int16_t *src, ptrdiff_t sstep, int16_t *dst, ptrdiff_t dstep)
	Perform IIR filtering on signed 16-bit input samples. More...
void	ff_iir_filter_flt (const struct FFIIRFilterCoeffs *c, struct FFIIRFilterState *s, int size, const float *src, ptrdiff_t sstep, float *dst, ptrdiff_t dstep)
	Perform IIR filtering on floating-point input samples. More...
av_cold void	ff_iir_filter_free_statep (struct FFIIRFilterState **state)
	Free and zero filter state. More...
av_cold void	ff_iir_filter_free_coeffsp (struct FFIIRFilterCoeffs **coeffsp)
	Free filter coefficients. More...
void	ff_iir_filter_init (FFIIRFilterContext *f)
	Initialize FFIIRFilterContext.

Detailed Description

different IIR filters implementation

Macro Definition Documentation

FILTER_BW_O4

#define FILTER_BW_O4	(		type,
			fmt
	)

Value:

{           \
    int i;                                  \
    const type *src0 = src;                 \
    type       *dst0 = dst;                 \
    for (i = 0; i < size; i += 4) {         \
        float in, res;                      \
        FILTER_BW_O4_1(0, 1, 2, 3, fmt);    \
        FILTER_BW_O4_1(1, 2, 3, 0, fmt);    \
        FILTER_BW_O4_1(2, 3, 0, 1, fmt);    \
        FILTER_BW_O4_1(3, 0, 1, 2, fmt);    \
    }                                       \
}

FILTER_BW_O4_1

#define FILTER_BW_O4_1	(		i0,
			i1,
			i2,
			i3,
			fmt
	)

Value:

in = *src0    * 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;                    \
    CONV_ ## fmt(*dst0, res)                            \
    s->x[i0] = in;                                      \
    src0    += sstep;                                   \
    dst0    += dstep;

FILTER_DIRECT_FORM_II

#define FILTER_DIRECT_FORM_II	(		type,
			fmt
	)

Value:

{                                  \
    int i;                                                                  \
    const type *src0 = src;                                                 \
    type       *dst0 = dst;                                                 \
    for (i = 0; i < size; i++) {                                            \
        int j;                                                              \
        float in, res;                                                      \
        in = *src0 * c->gain;                                               \
        for (j = 0; j < c->order; j++)                                      \
            in += c->cy[j] * s->x[j];                                       \
        res = s->x[0] + in + s->x[c->order >> 1] * c->cx[c->order >> 1];    \
        for (j = 1; j < c->order >> 1; j++)                                 \
            res += (s->x[j] + s->x[c->order - j]) * c->cx[j];               \
        for (j = 0; j < c->order - 1; j++)                                  \
            s->x[j] = s->x[j + 1];                                          \
        CONV_ ## fmt(*dst0, res)                                            \
        s->x[c->order - 1] = in;                                            \
        src0              += sstep;                                         \
        dst0              += dstep;                                         \
    }                                                                       \
}

FILTER_O2

#define FILTER_O2	(		type,
			fmt
	)

Value:

{                                              \
    int i;                                                                  \
    const type *src0 = src;                                                 \
    type       *dst0 = dst;                                                 \
    for (i = 0; i < size; i++) {                                            \
        float in = *src0   * c->gain  +                                     \
                   s->x[0] * c->cy[0] +                                     \
                   s->x[1] * c->cy[1];                                      \
        CONV_ ## fmt(*dst0, s->x[0] + in + s->x[1] * c->cx[1])              \
        s->x[0] = s->x[1];                                                  \
        s->x[1] = in;                                                       \
        src0   += sstep;                                                    \
        dst0   += dstep;                                                    \
    }                                                                       \
}

Function Documentation

ff_iir_filter()

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

Perform IIR filtering on signed 16-bit 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

ff_iir_filter_flt()

void ff_iir_filter_flt	(	const struct FFIIRFilterCoeffs *	coeffs,
		struct FFIIRFilterState *	state,
		int	size,
		const float *	src,
		ptrdiff_t	sstep,
		float *	dst,
		ptrdiff_t	dstep
	)

Perform IIR filtering on floating-point 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

ff_iir_filter_free_coeffsp()

av_cold void ff_iir_filter_free_coeffsp

(

struct FFIIRFilterCoeffs **

coeffs

)

Free filter coefficients.

Parameters

coeffs

pointer allocated with ff_iir_filter_init_coeffs()

ff_iir_filter_free_statep()

av_cold void ff_iir_filter_free_statep

(

struct FFIIRFilterState **

state

)

Free and zero filter state.

Parameters

state

pointer to pointer allocated with ff_iir_filter_init_state()

ff_iir_filter_init_coeffs()

av_cold struct FFIIRFilterCoeffs* ff_iir_filter_init_coeffs	(	void *	avc,
		enum IIRFilterType	filt_type,
		enum IIRFilterMode	filt_mode,
		int	order,
		float	cutoff_ratio,
		float	stopband,
		float	ripple
	)

Initialize filter coefficients.

Parameters

avc	a pointer to an arbitrary struct of which the first field is a pointer to an AVClass struct
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

ff_iir_filter_init_state()

av_cold struct FFIIRFilterState* ff_iir_filter_init_state

(

int

order

)

Create new filter state.

Parameters

order

filter order

Returns

pointer to new filter state or NULL if state creation fails