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/* |
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* IIR filter |
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* Copyright (c) 2008 Konstantin Shishkov |
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* |
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* This file is part of FFmpeg. |
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* |
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* FFmpeg is free software; you can redistribute it and/or |
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* modify it under the terms of the GNU Lesser General Public |
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* License as published by the Free Software Foundation; either |
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* version 2.1 of the License, or (at your option) any later version. |
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* |
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* FFmpeg is distributed in the hope that it will be useful, |
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* but WITHOUT ANY WARRANTY; without even the implied warranty of |
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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* Lesser General Public License for more details. |
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* |
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* You should have received a copy of the GNU Lesser General Public |
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* License along with FFmpeg; if not, write to the Free Software |
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
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*/ |
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/** |
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* @file |
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* different IIR filters implementation |
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*/ |
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#include <math.h> |
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#include "libavutil/attributes.h" |
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#include "libavutil/common.h" |
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#include "iirfilter.h" |
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/** |
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* IIR filter global parameters |
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*/ |
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typedef struct FFIIRFilterCoeffs { |
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int order; |
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float gain; |
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int *cx; |
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float *cy; |
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} FFIIRFilterCoeffs; |
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/** |
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* IIR filter state |
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*/ |
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typedef struct FFIIRFilterState { |
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float x[1]; |
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} FFIIRFilterState; |
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/// maximum supported filter order |
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#define MAXORDER 30 |
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static av_cold int butterworth_init_coeffs(void *avc, |
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struct FFIIRFilterCoeffs *c, |
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enum IIRFilterMode filt_mode, |
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int order, float cutoff_ratio, |
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float stopband) |
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{ |
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int i, j; |
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double wa; |
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double p[MAXORDER + 1][2]; |
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✗✓ |
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if (filt_mode != FF_FILTER_MODE_LOWPASS) { |
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av_log(avc, AV_LOG_ERROR, "Butterworth filter currently only supports " |
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"low-pass filter mode\n"); |
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return -1; |
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} |
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✗✓ |
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if (order & 1) { |
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av_log(avc, AV_LOG_ERROR, "Butterworth filter currently only supports " |
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"even filter orders\n"); |
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return -1; |
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} |
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wa = 2 * tan(M_PI * 0.5 * cutoff_ratio); |
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c->cx[0] = 1; |
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✓✓ |
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for (i = 1; i < (order >> 1) + 1; i++) |
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c->cx[i] = c->cx[i - 1] * (order - i + 1LL) / i; |
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p[0][0] = 1.0; |
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p[0][1] = 0.0; |
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✓✓ |
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for (i = 1; i <= order; i++) |
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p[i][0] = p[i][1] = 0.0; |
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✓✓ |
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for (i = 0; i < order; i++) { |
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double zp[2]; |
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double th = (i + (order >> 1) + 0.5) * M_PI / order; |
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double a_re, a_im, c_re, c_im; |
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zp[0] = cos(th) * wa; |
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zp[1] = sin(th) * wa; |
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a_re = zp[0] + 2.0; |
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c_re = zp[0] - 2.0; |
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a_im = |
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c_im = zp[1]; |
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zp[0] = (a_re * c_re + a_im * c_im) / (c_re * c_re + c_im * c_im); |
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zp[1] = (a_im * c_re - a_re * c_im) / (c_re * c_re + c_im * c_im); |
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✓✓ |
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for (j = order; j >= 1; j--) { |
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a_re = p[j][0]; |
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a_im = p[j][1]; |
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p[j][0] = a_re * zp[0] - a_im * zp[1] + p[j - 1][0]; |
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p[j][1] = a_re * zp[1] + a_im * zp[0] + p[j - 1][1]; |
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} |
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a_re = p[0][0] * zp[0] - p[0][1] * zp[1]; |
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p[0][1] = p[0][0] * zp[1] + p[0][1] * zp[0]; |
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p[0][0] = a_re; |
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} |
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c->gain = p[order][0]; |
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✓✓ |
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for (i = 0; i < order; i++) { |
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c->gain += p[i][0]; |
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c->cy[i] = (-p[i][0] * p[order][0] + -p[i][1] * p[order][1]) / |
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(p[order][0] * p[order][0] + p[order][1] * p[order][1]); |
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} |
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c->gain /= 1 << order; |
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return 0; |
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} |
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static av_cold int biquad_init_coeffs(void *avc, struct FFIIRFilterCoeffs *c, |
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enum IIRFilterMode filt_mode, int order, |
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float cutoff_ratio, float stopband) |
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{ |
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double cos_w0, sin_w0; |
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double a0, x0, x1; |
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if (filt_mode != FF_FILTER_MODE_HIGHPASS && |
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filt_mode != FF_FILTER_MODE_LOWPASS) { |
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av_log(avc, AV_LOG_ERROR, "Biquad filter currently only supports " |
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"high-pass and low-pass filter modes\n"); |
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return -1; |
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} |
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if (order != 2) { |
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av_log(avc, AV_LOG_ERROR, "Biquad filter must have order of 2\n"); |
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return -1; |
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} |
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cos_w0 = cos(M_PI * cutoff_ratio); |
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sin_w0 = sin(M_PI * cutoff_ratio); |
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a0 = 1.0 + (sin_w0 / 2.0); |
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if (filt_mode == FF_FILTER_MODE_HIGHPASS) { |
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c->gain = ((1.0 + cos_w0) / 2.0) / a0; |
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x0 = ((1.0 + cos_w0) / 2.0) / a0; |
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x1 = (-(1.0 + cos_w0)) / a0; |
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} else { // FF_FILTER_MODE_LOWPASS |
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c->gain = ((1.0 - cos_w0) / 2.0) / a0; |
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x0 = ((1.0 - cos_w0) / 2.0) / a0; |
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x1 = (1.0 - cos_w0) / a0; |
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} |
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c->cy[0] = (-1.0 + (sin_w0 / 2.0)) / a0; |
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c->cy[1] = (2.0 * cos_w0) / a0; |
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// divide by gain to make the x coeffs integers. |
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// during filtering, the delay state will include the gain multiplication |
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c->cx[0] = lrintf(x0 / c->gain); |
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c->cx[1] = lrintf(x1 / c->gain); |
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return 0; |
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} |
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1 |
av_cold struct FFIIRFilterCoeffs *ff_iir_filter_init_coeffs(void *avc, |
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enum IIRFilterType filt_type, |
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enum IIRFilterMode filt_mode, |
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int order, float cutoff_ratio, |
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float stopband, float ripple) |
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{ |
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FFIIRFilterCoeffs *c; |
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int ret = 0; |
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✓✗✓✗
✗✓ |
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if (order <= 0 || order > MAXORDER || cutoff_ratio >= 1.0) |
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return NULL; |
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✓✗ |
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if (!(c = av_mallocz(sizeof(*c))) || |
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✓✗ |
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!(c->cx = av_malloc (sizeof(c->cx[0]) * ((order >> 1) + 1))) || |
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✗✓ |
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!(c->cy = av_malloc (sizeof(c->cy[0]) * order))) |
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goto free; |
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c->order = order; |
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✓✗✗ |
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switch (filt_type) { |
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case FF_FILTER_TYPE_BUTTERWORTH: |
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ret = butterworth_init_coeffs(avc, c, filt_mode, order, cutoff_ratio, |
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stopband); |
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break; |
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case FF_FILTER_TYPE_BIQUAD: |
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ret = biquad_init_coeffs(avc, c, filt_mode, order, cutoff_ratio, |
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stopband); |
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break; |
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default: |
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av_log(avc, AV_LOG_ERROR, "filter type is not currently implemented\n"); |
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goto free; |
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} |
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✓✗ |
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if (!ret) |
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return c; |
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free: |
197 |
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ff_iir_filter_free_coeffsp(&c); |
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return NULL; |
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} |
200 |
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av_cold struct FFIIRFilterState *ff_iir_filter_init_state(int order) |
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{ |
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FFIIRFilterState *s = av_mallocz(sizeof(FFIIRFilterState) + sizeof(s->x[0]) * (order - 1)); |
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return s; |
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} |
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#define CONV_S16(dest, source) dest = av_clip_int16(lrintf(source)); |
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#define CONV_FLT(dest, source) dest = source; |
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211 |
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#define FILTER_BW_O4_1(i0, i1, i2, i3, fmt) \ |
212 |
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in = *src0 * c->gain + \ |
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c->cy[0] * s->x[i0] + \ |
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c->cy[1] * s->x[i1] + \ |
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c->cy[2] * s->x[i2] + \ |
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c->cy[3] * s->x[i3]; \ |
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res = (s->x[i0] + in) * 1 + \ |
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(s->x[i1] + s->x[i3]) * 4 + \ |
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s->x[i2] * 6; \ |
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CONV_ ## fmt(*dst0, res) \ |
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s->x[i0] = in; \ |
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src0 += sstep; \ |
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dst0 += dstep; |
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225 |
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#define FILTER_BW_O4(type, fmt) { \ |
226 |
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int i; \ |
227 |
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const type *src0 = src; \ |
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type *dst0 = dst; \ |
229 |
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for (i = 0; i < size; i += 4) { \ |
230 |
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float in, res; \ |
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FILTER_BW_O4_1(0, 1, 2, 3, fmt); \ |
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FILTER_BW_O4_1(1, 2, 3, 0, fmt); \ |
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FILTER_BW_O4_1(2, 3, 0, 1, fmt); \ |
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FILTER_BW_O4_1(3, 0, 1, 2, fmt); \ |
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} \ |
236 |
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} |
237 |
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238 |
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#define FILTER_DIRECT_FORM_II(type, fmt) { \ |
239 |
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int i; \ |
240 |
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const type *src0 = src; \ |
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type *dst0 = dst; \ |
242 |
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for (i = 0; i < size; i++) { \ |
243 |
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int j; \ |
244 |
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float in, res; \ |
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in = *src0 * c->gain; \ |
246 |
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for (j = 0; j < c->order; j++) \ |
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in += c->cy[j] * s->x[j]; \ |
248 |
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res = s->x[0] + in + s->x[c->order >> 1] * c->cx[c->order >> 1]; \ |
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for (j = 1; j < c->order >> 1; j++) \ |
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res += (s->x[j] + s->x[c->order - j]) * c->cx[j]; \ |
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for (j = 0; j < c->order - 1; j++) \ |
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s->x[j] = s->x[j + 1]; \ |
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CONV_ ## fmt(*dst0, res) \ |
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s->x[c->order - 1] = in; \ |
255 |
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src0 += sstep; \ |
256 |
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dst0 += dstep; \ |
257 |
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} \ |
258 |
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} |
259 |
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260 |
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#define FILTER_O2(type, fmt) { \ |
261 |
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int i; \ |
262 |
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const type *src0 = src; \ |
263 |
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type *dst0 = dst; \ |
264 |
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for (i = 0; i < size; i++) { \ |
265 |
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float in = *src0 * c->gain + \ |
266 |
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s->x[0] * c->cy[0] + \ |
267 |
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s->x[1] * c->cy[1]; \ |
268 |
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CONV_ ## fmt(*dst0, s->x[0] + in + s->x[1] * c->cx[1]) \ |
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s->x[0] = s->x[1]; \ |
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s->x[1] = in; \ |
271 |
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src0 += sstep; \ |
272 |
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dst0 += dstep; \ |
273 |
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} \ |
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} |
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276 |
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1 |
void ff_iir_filter(const struct FFIIRFilterCoeffs *c, |
277 |
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struct FFIIRFilterState *s, int size, |
278 |
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const int16_t *src, ptrdiff_t sstep, |
279 |
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int16_t *dst, ptrdiff_t dstep) |
280 |
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{ |
281 |
✗✓ |
1 |
if (c->order == 2) { |
282 |
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FILTER_O2(int16_t, S16) |
283 |
✓✗ |
1 |
} else if (c->order == 4) { |
284 |
✓✓ |
257 |
FILTER_BW_O4(int16_t, S16) |
285 |
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} else { |
286 |
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FILTER_DIRECT_FORM_II(int16_t, S16) |
287 |
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} |
288 |
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1 |
} |
289 |
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290 |
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void ff_iir_filter_flt(const struct FFIIRFilterCoeffs *c, |
291 |
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struct FFIIRFilterState *s, int size, |
292 |
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const float *src, ptrdiff_t sstep, |
293 |
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float *dst, ptrdiff_t dstep) |
294 |
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{ |
295 |
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if (c->order == 2) { |
296 |
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FILTER_O2(float, FLT) |
297 |
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} else if (c->order == 4) { |
298 |
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FILTER_BW_O4(float, FLT) |
299 |
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} else { |
300 |
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FILTER_DIRECT_FORM_II(float, FLT) |
301 |
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} |
302 |
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} |
303 |
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304 |
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1 |
av_cold void ff_iir_filter_free_statep(struct FFIIRFilterState **state) |
305 |
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{ |
306 |
|
1 |
av_freep(state); |
307 |
|
1 |
} |
308 |
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309 |
|
12 |
av_cold void ff_iir_filter_free_coeffsp(struct FFIIRFilterCoeffs **coeffsp) |
310 |
|
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{ |
311 |
|
12 |
struct FFIIRFilterCoeffs *coeffs = *coeffsp; |
312 |
✓✓ |
12 |
if (coeffs) { |
313 |
|
1 |
av_freep(&coeffs->cx); |
314 |
|
1 |
av_freep(&coeffs->cy); |
315 |
|
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} |
316 |
|
12 |
av_freep(coeffsp); |
317 |
|
12 |
} |
318 |
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319 |
|
11 |
void ff_iir_filter_init(FFIIRFilterContext *f) { |
320 |
|
11 |
f->filter_flt = ff_iir_filter_flt; |
321 |
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322 |
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if (HAVE_MIPSFPU) |
323 |
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ff_iir_filter_init_mips(f); |
324 |
|
11 |
} |