From: Kostya Shishkov Date: Thu, 28 Aug 2008 04:53:57 +0000 (+0000) Subject: Add generic IIR filter interface with Butterworth lowpass filter implementation X-Git-Url: https://git.sesse.net/?a=commitdiff_plain;h=a169f49881fb9ce7cd55fdb654fb4b3057f8ddad;p=ffmpeg Add generic IIR filter interface with Butterworth lowpass filter implementation and remove obsoleted old lowpass filter. Originally committed as revision 15005 to svn://svn.ffmpeg.org/ffmpeg/trunk --- diff --git a/libavcodec/iirfilter.c b/libavcodec/iirfilter.c new file mode 100644 index 00000000000..bcaa021b60e --- /dev/null +++ b/libavcodec/iirfilter.c @@ -0,0 +1,164 @@ +/* + * IIR filter + * Copyright (c) 2008 Konstantin Shishkov + * + * This file is part of FFmpeg. + * + * FFmpeg 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. + * + * FFmpeg 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 FFmpeg; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + */ + +/** + * @file iirfilter.c + * different IIR filters implementation + */ + +#include "iirfilter.h" +#include +#include + +/** + * 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 + +struct FFIIRFilterCoeffs* ff_iir_filter_init_coeffs(enum IIRFilterType filt_type, + enum IIRFilterMode filt_mode, + int order, float cutoff_ratio, + float stopband, float ripple) +{ + int i, j, size; + FFIIRFilterCoeffs *c; + double wa; + complex p[MAXORDER + 1]; + + if(filt_type != FF_FILTER_TYPE_BUTTERWORTH || filt_mode != FF_FILTER_MODE_LOWPASS) + return NULL; + if(order <= 1 || (order & 1) || order > MAXORDER || cutoff_ratio >= 1.0) + return NULL; + + c = av_malloc(sizeof(FFIIRFilterCoeffs)); + c->cx = av_malloc(sizeof(c->cx[0]) * ((order >> 1) + 1)); + c->cy = av_malloc(sizeof(c->cy[0]) * order); + c->order = order; + + 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] = 1.0; + for(i = 1; i <= order; i++) + p[i] = 0.0; + for(i = 0; i < order; i++){ + complex zp; + double th = (i + (order >> 1) + 0.5) * M_PI / order; + zp = cexp(I*th) * wa; + zp = (zp + 2.0) / (zp - 2.0); + + for(j = order; j >= 1; j--) + p[j] = zp*p[j] + p[j - 1]; + p[0] *= zp; + } + c->gain = creal(p[order]); + for(i = 0; i < order; i++){ + c->gain += creal(p[i]); + c->cy[i] = creal(-p[i] / p[order]); + } + c->gain /= 1 << order; + + return c; +} + +struct FFIIRFilterState* ff_iir_filter_init_state(int order) +{ + FFIIRFilterState* s = av_mallocz(sizeof(FFIIRFilterState) + sizeof(s->x[0]) * (order - 1)); + return s; +} + +#define FILTER(i0, i1, i2, i3) \ + 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; \ + +void ff_iir_filter(const struct FFIIRFilterCoeffs *c, struct FFIIRFilterState *s, int size, const int16_t *src, int sstep, int16_t *dst, int dstep) +{ + int i; + + if(c->order == 4){ + for(i = 0; i < size; i += 4){ + float in, res; + + FILTER(0, 1, 2, 3); + FILTER(1, 2, 3, 0); + FILTER(2, 3, 0, 1); + FILTER(3, 0, 1, 2); + } + }else{ + for(i = 0; i < size; i++){ + int j; + float in, res; + in = *src * 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]; + *dst = av_clip_int16(lrintf(res)); + s->x[c->order - 1] = in; + src += sstep; + dst += sstep; + } + } +} + +void ff_iir_filter_free_state(struct FFIIRFilterState *state) +{ + av_free(state); +} + +void ff_iir_filter_free_coeffs(struct FFIIRFilterCoeffs *coeffs) +{ + if(coeffs){ + av_free(coeffs->cx); + av_free(coeffs->cy); + } + av_free(coeffs); +} + diff --git a/libavcodec/lowpass.h b/libavcodec/iirfilter.h similarity index 50% rename from libavcodec/lowpass.h rename to libavcodec/iirfilter.h index 6a779077463..ac948d8959b 100644 --- a/libavcodec/lowpass.h +++ b/libavcodec/iirfilter.h @@ -1,5 +1,5 @@ /* - * Lowpass IIR filter + * IIR filter * Copyright (c) 2008 Konstantin Shishkov * * This file is part of FFmpeg. @@ -20,27 +20,48 @@ */ /** - * @file lowpass.h - * lowpass filter interface + * @file iirfilter.h + * IIR filter interface */ -#ifndef FFMPEG_LOWPASS_H -#define FFMPEG_LOWPASS_H +#ifndef FFMPEG_IIRFILTER_H +#define FFMPEG_IIRFILTER_H #include "avcodec.h" -struct FFLPFilterCoeffs; -struct FFLPFilterState; +struct FFIIRFilterCoeffs; +struct FFIIRFilterState; + +enum IIRFilterType{ + FF_FILTER_TYPE_BESSEL, + FF_FILTER_TYPE_BUTTERWORTH, + FF_FILTER_TYPE_CHEBYSHEV, + FF_FILTER_TYPE_ELLIPTIC, +}; + +enum IIRFilterMode{ + FF_FILTER_MODE_LOWPASS, + FF_FILTER_MODE_HIGHPASS, + FF_FILTER_MODE_BANDPASS, + FF_FILTER_MODE_BANDSTOP, +}; /** * Initialize filter coefficients. * + * @param filt_type filter type (e.g. Butterworth) + * @param filt_mode filter mode (e.g. lowpass) * @param order filter order * @param cutoff_ratio cutoff to input frequency ratio + * @param stopband stopband to input frequency ratio (used by bandpass and bandstop filter modes) + * @param ripple ripple factor (used only in Chebyshev filters) * * @return pointer to filter coefficients structure or NULL if filter cannot be created */ -const struct FFLPFilterCoeffs* ff_lowpass_filter_init_coeffs(int order, float cutoff_ratio); +struct FFIIRFilterCoeffs* ff_iir_filter_init_coeffs(enum IIRFilterType filt_type, + enum IIRFilterMode filt_mode, + int order, float cutoff_ratio, + float stopband, float ripple); /** * Create new filter state. @@ -49,23 +70,21 @@ const struct FFLPFilterCoeffs* ff_lowpass_filter_init_coeffs(int order, float cu * * @return pointer to new filter state or NULL if state creation fails */ -struct FFLPFilterState* ff_lowpass_filter_init_state(int order); +struct FFIIRFilterState* ff_iir_filter_init_state(int order); -#if 0 //enable with arbitrary order filter implementation, use av_free() for filter state only for now /** * Free filter coefficients. * - * @param coeffs pointer allocated with ff_lowpass_filter_init_coeffs() + * @param coeffs pointer allocated with ff_iir_filter_init_coeffs() */ -void ff_lowpass_filter_free_coeffs(struct FFLPFilterCoeffs *coeffs); +void ff_iir_filter_free_coeffs(struct FFIIRFilterCoeffs *coeffs); /** * Free filter state. * - * @param state pointer allocated with ff_lowpass_filter_init_state() + * @param state pointer allocated with ff_iir_filter_init_state() */ -void ff_lowpass_filter_free_state(struct FFLPFilterState *state); -#endif +void ff_iir_filter_free_state(struct FFIIRFilterState *state); /** * Perform lowpass filtering on input samples. @@ -78,6 +97,7 @@ void ff_lowpass_filter_free_state(struct FFLPFilterState *state); * @param dst filtered samples (destination may be the same as input) * @param dstep destination stride */ -void ff_lowpass_filter(const struct FFLPFilterCoeffs *coeffs, struct FFLPFilterState *state, int size, int16_t *src, int sstep, int16_t *dst, int dstep); +void ff_iir_filter(const struct FFIIRFilterCoeffs *coeffs, struct FFIIRFilterState *state, + int size, const int16_t *src, int sstep, int16_t *dst, int dstep); -#endif /* FFMPEG_LOWPASS_H */ +#endif /* FFMPEG_IIRFILTER_H */ diff --git a/libavcodec/lowpass.c b/libavcodec/lowpass.c deleted file mode 100644 index 7159a1ee023..00000000000 --- a/libavcodec/lowpass.c +++ /dev/null @@ -1,129 +0,0 @@ -/* - * Lowpass IIR filter - * Copyright (c) 2008 Konstantin Shishkov - * - * This file is part of FFmpeg. - * - * FFmpeg 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. - * - * FFmpeg 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 FFmpeg; if not, write to the Free Software - * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA - */ - -/** - * @file lowpass.c - * lowpass filter implementation - */ - -#include "lowpass.h" - -/********************** - * TODO: - * support filters with order != 4 - * calculate coefficients for filter instead of taking approximate ones from the table - *********************/ - -/** filter order */ -#define LOWPASS_FILTER_ORDER 4 - -/** - * IIR filter global parameters - */ -typedef struct FFLPFilterCoeffs{ - float gain; - float c[LOWPASS_FILTER_ORDER]; -}FFLPFilterCoeffs; - -/** - * filter data for 4th order IIR lowpass Butterworth filter - */ -static const FFLPFilterCoeffs lp_filter_coeffs[] = { - { 9.398085e-01, { -0.0176648009, 0.0000000000, -0.4860288221, 0.0000000000 } }, - { 6.816645e-01, { -0.4646665999, -2.2127207402, -3.9912017501, -3.2380429984 } }, - { 4.998150e-01, { -0.2498216698, -1.3392807613, -2.7693097862, -2.6386277439 } }, - { 3.103469e-01, { -0.0965076902, -0.5977763360, -1.4972580903, -1.7740085241 } }, - { 2.346995e-01, { -0.0557639007, -0.3623690447, -1.0304538354, -1.3066051440 } }, - { 1.528432e-01, { -0.0261686639, -0.1473794606, -0.6204721225, -0.6514716536 } }, - { 6.917529e-02, { -0.0202414073, 0.0780167640, -0.5277442247, 0.3631641670 } }, - { 6.178391e-02, { -0.0223681543, 0.1069446609, -0.5615167033, 0.4883976841 } }, - { 5.298685e-02, { -0.0261686639, 0.1473794606, -0.6204721225, 0.6514716536 } }, - { 2.229030e-02, { -0.0647354087, 0.4172275190, -1.1412129810, 1.4320761385 } }, - { 1.693903e-02, { -0.0823177861, 0.5192354923, -1.3444768251, 1.6365345642 } }, - { 7.374053e-03, { -0.1481421788, 0.8650973862, -1.9894244796, 2.1544844308 } }, - { 5.541768e-03, { -0.1742301048, 0.9921936565, -2.2090801108, 2.3024482658 } }, -}; - -/** cutoff ratios for lp_filter_data[] */ -static const float lp_cutoff_ratios[] = { - 0.5000000000, 0.4535147392, 0.4166666667, 0.3628117914, - 0.3333333333, 0.2916666667, 0.2267573696, 0.2187500000, - 0.2083333333, 0.1587301587, 0.1458333333, 0.1133786848, - 0.1041666667, -}; - -/** - * IIR filter state - */ -typedef struct FFLPFilterState{ - float x[LOWPASS_FILTER_ORDER]; -}FFLPFilterState; - -const struct FFLPFilterCoeffs* ff_lowpass_filter_init_coeffs(int order, float cutoff_ratio) -{ - int i, size; - - //we can create only order-4 filters with cutoff ratio <= 0.5 for now - if(order != LOWPASS_FILTER_ORDER) return NULL; - - size = sizeof(lp_cutoff_ratios) / sizeof(lp_cutoff_ratios[0]); - if(cutoff_ratio > lp_cutoff_ratios[0]) - return NULL; - for(i = 0; i < size; i++){ - if(cutoff_ratio >= lp_cutoff_ratios[i]) - break; - } - if(i == size) - i = size - 1; - return &lp_filter_coeffs[i]; -} - -struct FFLPFilterState* ff_lowpass_filter_init_state(int order) -{ - if(order != LOWPASS_FILTER_ORDER) return NULL; - return av_mallocz(sizeof(FFLPFilterState)); -} - -#define FILTER(i0, i1, i2, i3) \ - in = *src * c->gain \ - + c->c[0]*s->x[i0] + c->c[1]*s->x[i1] \ - + c->c[2]*s->x[i2] + c->c[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; \ - -void ff_lowpass_filter(const struct FFLPFilterCoeffs *c, struct FFLPFilterState *s, int size, int16_t *src, int sstep, int16_t *dst, int dstep) -{ - int i; - - for(i = 0; i < size; i += 4){ - float in, res; - - FILTER(0, 1, 2, 3); - FILTER(1, 2, 3, 0); - FILTER(2, 3, 0, 1); - FILTER(3, 0, 1, 2); - } -}