| /* |
| * 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 |
| * different IIR filters implementation |
| */ |
| |
| #include "iirfilter.h" |
| #include <math.h> |
| #include "libavutil/attributes.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 av_cold 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 av_cold 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_coeffsp(&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_statep(struct FFIIRFilterState **state) |
| { |
| av_freep(state); |
| } |
| |
| av_cold void ff_iir_filter_free_coeffsp(struct FFIIRFilterCoeffs **coeffsp) |
| { |
| struct FFIIRFilterCoeffs *coeffs = *coeffsp; |
| if(coeffs){ |
| av_freep(&coeffs->cx); |
| av_freep(&coeffs->cy); |
| } |
| av_freep(coeffsp); |
| } |
| |
| void ff_iir_filter_init(FFIIRFilterContext *f) { |
| f->filter_flt = ff_iir_filter_flt; |
| |
| if (HAVE_MIPSFPU) |
| ff_iir_filter_init_mips(f); |
| } |
| |
| #ifdef TEST |
| #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_coeffsp(&fcoeffs); |
| ff_iir_filter_free_statep(&fstate); |
| return 0; |
| } |
| #endif /* TEST */ |
