mirror of
https://github.com/librempeg/librempeg
synced 2024-11-23 11:39:47 +00:00
347 lines
12 KiB
C
347 lines
12 KiB
C
/*
|
|
* IIR filter
|
|
* Copyright (c) 2008 Konstantin Shishkov
|
|
*
|
|
* This file is part of Libav.
|
|
*
|
|
* Libav is free software; you can redistribute it and/or
|
|
* modify it under the terms of the GNU Lesser General Public
|
|
* License as published by the Free Software Foundation; either
|
|
* version 2.1 of the License, or (at your option) any later version.
|
|
*
|
|
* Libav is distributed in the hope that it will be useful,
|
|
* but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
* Lesser General Public License for more details.
|
|
*
|
|
* You should have received a copy of the GNU Lesser General Public
|
|
* License along with Libav; if not, write to the Free Software
|
|
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
|
|
*/
|
|
|
|
/**
|
|
* @file
|
|
* different IIR filters implementation
|
|
*/
|
|
|
|
#include "iirfilter.h"
|
|
#include <math.h>
|
|
#include "libavutil/common.h"
|
|
|
|
/**
|
|
* IIR filter global parameters
|
|
*/
|
|
typedef struct FFIIRFilterCoeffs{
|
|
int order;
|
|
float gain;
|
|
int *cx;
|
|
float *cy;
|
|
}FFIIRFilterCoeffs;
|
|
|
|
/**
|
|
* IIR filter state
|
|
*/
|
|
typedef struct FFIIRFilterState{
|
|
float x[1];
|
|
}FFIIRFilterState;
|
|
|
|
/// maximum supported filter order
|
|
#define MAXORDER 30
|
|
|
|
static int butterworth_init_coeffs(void *avc, struct FFIIRFilterCoeffs *c,
|
|
enum IIRFilterMode filt_mode,
|
|
int order, float cutoff_ratio,
|
|
float stopband)
|
|
{
|
|
int i, j;
|
|
double wa;
|
|
double p[MAXORDER + 1][2];
|
|
|
|
if (filt_mode != FF_FILTER_MODE_LOWPASS) {
|
|
av_log(avc, AV_LOG_ERROR, "Butterworth filter currently only supports "
|
|
"low-pass filter mode\n");
|
|
return -1;
|
|
}
|
|
if (order & 1) {
|
|
av_log(avc, AV_LOG_ERROR, "Butterworth filter currently only supports "
|
|
"even filter orders\n");
|
|
return -1;
|
|
}
|
|
|
|
wa = 2 * tan(M_PI * 0.5 * cutoff_ratio);
|
|
|
|
c->cx[0] = 1;
|
|
for(i = 1; i < (order >> 1) + 1; i++)
|
|
c->cx[i] = c->cx[i - 1] * (order - i + 1LL) / i;
|
|
|
|
p[0][0] = 1.0;
|
|
p[0][1] = 0.0;
|
|
for(i = 1; i <= order; i++)
|
|
p[i][0] = p[i][1] = 0.0;
|
|
for(i = 0; i < order; i++){
|
|
double zp[2];
|
|
double th = (i + (order >> 1) + 0.5) * M_PI / order;
|
|
double a_re, a_im, c_re, c_im;
|
|
zp[0] = cos(th) * wa;
|
|
zp[1] = sin(th) * wa;
|
|
a_re = zp[0] + 2.0;
|
|
c_re = zp[0] - 2.0;
|
|
a_im =
|
|
c_im = zp[1];
|
|
zp[0] = (a_re * c_re + a_im * c_im) / (c_re * c_re + c_im * c_im);
|
|
zp[1] = (a_im * c_re - a_re * c_im) / (c_re * c_re + c_im * c_im);
|
|
|
|
for(j = order; j >= 1; j--)
|
|
{
|
|
a_re = p[j][0];
|
|
a_im = p[j][1];
|
|
p[j][0] = a_re*zp[0] - a_im*zp[1] + p[j-1][0];
|
|
p[j][1] = a_re*zp[1] + a_im*zp[0] + p[j-1][1];
|
|
}
|
|
a_re = p[0][0]*zp[0] - p[0][1]*zp[1];
|
|
p[0][1] = p[0][0]*zp[1] + p[0][1]*zp[0];
|
|
p[0][0] = a_re;
|
|
}
|
|
c->gain = p[order][0];
|
|
for(i = 0; i < order; i++){
|
|
c->gain += p[i][0];
|
|
c->cy[i] = (-p[i][0] * p[order][0] + -p[i][1] * p[order][1]) /
|
|
(p[order][0] * p[order][0] + p[order][1] * p[order][1]);
|
|
}
|
|
c->gain /= 1 << order;
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int biquad_init_coeffs(void *avc, struct FFIIRFilterCoeffs *c,
|
|
enum IIRFilterMode filt_mode, int order,
|
|
float cutoff_ratio, float stopband)
|
|
{
|
|
double cos_w0, sin_w0;
|
|
double a0, x0, x1;
|
|
|
|
if (filt_mode != FF_FILTER_MODE_HIGHPASS &&
|
|
filt_mode != FF_FILTER_MODE_LOWPASS) {
|
|
av_log(avc, AV_LOG_ERROR, "Biquad filter currently only supports "
|
|
"high-pass and low-pass filter modes\n");
|
|
return -1;
|
|
}
|
|
if (order != 2) {
|
|
av_log(avc, AV_LOG_ERROR, "Biquad filter must have order of 2\n");
|
|
return -1;
|
|
}
|
|
|
|
cos_w0 = cos(M_PI * cutoff_ratio);
|
|
sin_w0 = sin(M_PI * cutoff_ratio);
|
|
|
|
a0 = 1.0 + (sin_w0 / 2.0);
|
|
|
|
if (filt_mode == FF_FILTER_MODE_HIGHPASS) {
|
|
c->gain = ((1.0 + cos_w0) / 2.0) / a0;
|
|
x0 = ((1.0 + cos_w0) / 2.0) / a0;
|
|
x1 = (-(1.0 + cos_w0)) / a0;
|
|
} else { // FF_FILTER_MODE_LOWPASS
|
|
c->gain = ((1.0 - cos_w0) / 2.0) / a0;
|
|
x0 = ((1.0 - cos_w0) / 2.0) / a0;
|
|
x1 = (1.0 - cos_w0) / a0;
|
|
}
|
|
c->cy[0] = (-1.0 + (sin_w0 / 2.0)) / a0;
|
|
c->cy[1] = (2.0 * cos_w0) / a0;
|
|
|
|
// divide by gain to make the x coeffs integers.
|
|
// during filtering, the delay state will include the gain multiplication
|
|
c->cx[0] = lrintf(x0 / c->gain);
|
|
c->cx[1] = lrintf(x1 / c->gain);
|
|
|
|
return 0;
|
|
}
|
|
|
|
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)
|
|
{
|
|
FFIIRFilterCoeffs *c;
|
|
int ret = 0;
|
|
|
|
if (order <= 0 || order > MAXORDER || cutoff_ratio >= 1.0)
|
|
return NULL;
|
|
|
|
FF_ALLOCZ_OR_GOTO(avc, c, sizeof(FFIIRFilterCoeffs),
|
|
init_fail);
|
|
FF_ALLOC_OR_GOTO (avc, c->cx, sizeof(c->cx[0]) * ((order >> 1) + 1),
|
|
init_fail);
|
|
FF_ALLOC_OR_GOTO (avc, c->cy, sizeof(c->cy[0]) * order,
|
|
init_fail);
|
|
c->order = order;
|
|
|
|
switch (filt_type) {
|
|
case FF_FILTER_TYPE_BUTTERWORTH:
|
|
ret = butterworth_init_coeffs(avc, c, filt_mode, order, cutoff_ratio,
|
|
stopband);
|
|
break;
|
|
case FF_FILTER_TYPE_BIQUAD:
|
|
ret = biquad_init_coeffs(avc, c, filt_mode, order, cutoff_ratio,
|
|
stopband);
|
|
break;
|
|
default:
|
|
av_log(avc, AV_LOG_ERROR, "filter type is not currently implemented\n");
|
|
goto init_fail;
|
|
}
|
|
|
|
if (!ret)
|
|
return c;
|
|
|
|
init_fail:
|
|
ff_iir_filter_free_coeffs(c);
|
|
return NULL;
|
|
}
|
|
|
|
av_cold struct FFIIRFilterState* ff_iir_filter_init_state(int order)
|
|
{
|
|
FFIIRFilterState* s = av_mallocz(sizeof(FFIIRFilterState) + sizeof(s->x[0]) * (order - 1));
|
|
return s;
|
|
}
|
|
|
|
#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) \
|
|
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;
|
|
|
|
#define FILTER_BW_O4(type, fmt) { \
|
|
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); \
|
|
} \
|
|
}
|
|
|
|
#define FILTER_DIRECT_FORM_II(type, fmt) { \
|
|
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; \
|
|
} \
|
|
}
|
|
|
|
#define FILTER_O2(type, fmt) { \
|
|
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; \
|
|
} \
|
|
}
|
|
|
|
void ff_iir_filter(const struct FFIIRFilterCoeffs *c,
|
|
struct FFIIRFilterState *s, int size,
|
|
const int16_t *src, int sstep, int16_t *dst, int dstep)
|
|
{
|
|
if (c->order == 2) {
|
|
FILTER_O2(int16_t, S16)
|
|
} else if (c->order == 4) {
|
|
FILTER_BW_O4(int16_t, S16)
|
|
} else {
|
|
FILTER_DIRECT_FORM_II(int16_t, S16)
|
|
}
|
|
}
|
|
|
|
void ff_iir_filter_flt(const struct FFIIRFilterCoeffs *c,
|
|
struct FFIIRFilterState *s, int size,
|
|
const float *src, int sstep, float *dst, int dstep)
|
|
{
|
|
if (c->order == 2) {
|
|
FILTER_O2(float, FLT)
|
|
} else if (c->order == 4) {
|
|
FILTER_BW_O4(float, FLT)
|
|
} else {
|
|
FILTER_DIRECT_FORM_II(float, FLT)
|
|
}
|
|
}
|
|
|
|
av_cold void ff_iir_filter_free_state(struct FFIIRFilterState *state)
|
|
{
|
|
av_free(state);
|
|
}
|
|
|
|
av_cold void ff_iir_filter_free_coeffs(struct FFIIRFilterCoeffs *coeffs)
|
|
{
|
|
if(coeffs){
|
|
av_free(coeffs->cx);
|
|
av_free(coeffs->cy);
|
|
}
|
|
av_free(coeffs);
|
|
}
|
|
|
|
#ifdef TEST
|
|
#undef printf
|
|
#include <stdio.h>
|
|
|
|
#define FILT_ORDER 4
|
|
#define SIZE 1024
|
|
int main(void)
|
|
{
|
|
struct FFIIRFilterCoeffs *fcoeffs = NULL;
|
|
struct FFIIRFilterState *fstate = NULL;
|
|
float cutoff_coeff = 0.4;
|
|
int16_t x[SIZE], y[SIZE];
|
|
int i;
|
|
|
|
fcoeffs = ff_iir_filter_init_coeffs(NULL, FF_FILTER_TYPE_BUTTERWORTH,
|
|
FF_FILTER_MODE_LOWPASS, FILT_ORDER,
|
|
cutoff_coeff, 0.0, 0.0);
|
|
fstate = ff_iir_filter_init_state(FILT_ORDER);
|
|
|
|
for (i = 0; i < SIZE; i++) {
|
|
x[i] = lrint(0.75 * INT16_MAX * sin(0.5*M_PI*i*i/SIZE));
|
|
}
|
|
|
|
ff_iir_filter(fcoeffs, fstate, SIZE, x, 1, y, 1);
|
|
|
|
for (i = 0; i < SIZE; i++)
|
|
printf("%6d %6d\n", x[i], y[i]);
|
|
|
|
ff_iir_filter_free_coeffs(fcoeffs);
|
|
ff_iir_filter_free_state(fstate);
|
|
return 0;
|
|
}
|
|
#endif /* TEST */
|