GCC Code Coverage Report
Directory: ../../../ffmpeg/ Exec Total Coverage
File: src/libavcodec/iirfilter.c Lines: 70 115 60.9 %
Date: 2020-07-13 04:22:34 Branches: 26 73 35.6 %

Line Branch Exec Source
1
/*
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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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 */
21
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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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27
#include <math.h>
28
29
#include "libavutil/attributes.h"
30
#include "libavutil/common.h"
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32
#include "iirfilter.h"
33
34
/**
35
 * IIR filter global parameters
36
 */
37
typedef struct FFIIRFilterCoeffs {
38
    int   order;
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    float gain;
40
    int   *cx;
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    float *cy;
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} FFIIRFilterCoeffs;
43
44
/**
45
 * IIR filter state
46
 */
47
typedef struct FFIIRFilterState {
48
    float x[1];
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} FFIIRFilterState;
50
51
/// maximum supported filter order
52
#define MAXORDER 30
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54
1
static av_cold int butterworth_init_coeffs(void *avc,
55
                                           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)
59
{
60
    int i, j;
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    double wa;
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    double p[MAXORDER + 1][2];
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64
1
    if (filt_mode != FF_FILTER_MODE_LOWPASS) {
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        av_log(avc, AV_LOG_ERROR, "Butterworth filter currently only supports "
66
                                  "low-pass filter mode\n");
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        return -1;
68
    }
69
1
    if (order & 1) {
70
        av_log(avc, AV_LOG_ERROR, "Butterworth filter currently only supports "
71
                                  "even filter orders\n");
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        return -1;
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    }
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75
1
    wa = 2 * tan(M_PI * 0.5 * cutoff_ratio);
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77
1
    c->cx[0] = 1;
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3
    for (i = 1; i < (order >> 1) + 1; i++)
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2
        c->cx[i] = c->cx[i - 1] * (order - i + 1LL) / i;
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81
1
    p[0][0] = 1.0;
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1
    p[0][1] = 0.0;
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5
    for (i = 1; i <= order; i++)
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4
        p[i][0] = p[i][1] = 0.0;
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5
    for (i = 0; i < order; i++) {
86
        double zp[2];
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4
        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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4
        zp[0] = cos(th) * wa;
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4
        zp[1] = sin(th) * wa;
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4
        a_re  = zp[0] + 2.0;
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4
        c_re  = zp[0] - 2.0;
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4
        a_im  =
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4
        c_im  = zp[1];
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4
        zp[0] = (a_re * c_re + a_im * c_im) / (c_re * c_re + c_im * c_im);
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4
        zp[1] = (a_im * c_re - a_re * c_im) / (c_re * c_re + c_im * c_im);
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20
        for (j = order; j >= 1; j--) {
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16
            a_re    = p[j][0];
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16
            a_im    = p[j][1];
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16
            p[j][0] = a_re * zp[0] - a_im * zp[1] + p[j - 1][0];
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16
            p[j][1] = a_re * zp[1] + a_im * zp[0] + p[j - 1][1];
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        }
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4
        a_re    = p[0][0] * zp[0] - p[0][1] * zp[1];
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4
        p[0][1] = p[0][0] * zp[1] + p[0][1] * zp[0];
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4
        p[0][0] = a_re;
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    }
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1
    c->gain = p[order][0];
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5
    for (i = 0; i < order; i++) {
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4
        c->gain += p[i][0];
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4
        c->cy[i] = (-p[i][0] * p[order][0] + -p[i][1] * p[order][1]) /
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4
                   (p[order][0] * p[order][0] + p[order][1] * p[order][1]);
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    }
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1
    c->gain /= 1 << order;
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116
1
    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 &&
127
        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");
130
        return -1;
131
    }
132
    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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137
    cos_w0 = cos(M_PI * cutoff_ratio);
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    sin_w0 = sin(M_PI * cutoff_ratio);
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140
    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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1
    int ret = 0;
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171

1
    if (order <= 0 || order > MAXORDER || cutoff_ratio >= 1.0)
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        return NULL;
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1
    if (!(c     = av_mallocz(sizeof(*c)))                            ||
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1
        !(c->cx = av_malloc (sizeof(c->cx[0]) * ((order >> 1) + 1))) ||
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1
        !(c->cy = av_malloc (sizeof(c->cy[0]) * order)))
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        goto free;
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1
    c->order = order;
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180
1
    switch (filt_type) {
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1
    case FF_FILTER_TYPE_BUTTERWORTH:
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1
        ret = butterworth_init_coeffs(avc, c, filt_mode, order, cutoff_ratio,
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                                      stopband);
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1
        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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1
    if (!ret)
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1
        return c;
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free:
197
    ff_iir_filter_free_coeffsp(&c);
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    return NULL;
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}
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1
av_cold struct FFIIRFilterState *ff_iir_filter_init_state(int order)
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{
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1
    FFIIRFilterState *s = av_mallocz(sizeof(FFIIRFilterState) + sizeof(s->x[0]) * (order - 1));
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1
    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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#define FILTER_BW_O4_1(i0, i1, i2, i3, fmt)             \
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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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#define FILTER_BW_O4(type, fmt) {           \
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    int i;                                  \
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    const type *src0 = src;                 \
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    type       *dst0 = dst;                 \
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    for (i = 0; i < size; i += 4) {         \
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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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    }                                       \
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}
237
238
#define FILTER_DIRECT_FORM_II(type, fmt) {                                  \
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    int i;                                                                  \
240
    const type *src0 = src;                                                 \
241
    type       *dst0 = dst;                                                 \
242
    for (i = 0; i < size; i++) {                                            \
243
        int j;                                                              \
244
        float in, res;                                                      \
245
        in = *src0 * c->gain;                                               \
246
        for (j = 0; j < c->order; j++)                                      \
247
            in += c->cy[j] * s->x[j];                                       \
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        res = s->x[0] + in + s->x[c->order >> 1] * c->cx[c->order >> 1];    \
249
        for (j = 1; j < c->order >> 1; j++)                                 \
250
            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;                                            \
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        src0              += sstep;                                         \
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        dst0              += dstep;                                         \
257
    }                                                                       \
258
}
259
260
#define FILTER_O2(type, fmt) {                                              \
261
    int i;                                                                  \
262
    const type *src0 = src;                                                 \
263
    type       *dst0 = dst;                                                 \
264
    for (i = 0; i < size; i++) {                                            \
265
        float in = *src0   * c->gain  +                                     \
266
                   s->x[0] * c->cy[0] +                                     \
267
                   s->x[1] * c->cy[1];                                      \
268
        CONV_ ## fmt(*dst0, s->x[0] + in + s->x[1] * c->cx[1])              \
269
        s->x[0] = s->x[1];                                                  \
270
        s->x[1] = in;                                                       \
271
        src0   += sstep;                                                    \
272
        dst0   += dstep;                                                    \
273
    }                                                                       \
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}
275
276
1
void ff_iir_filter(const struct FFIIRFilterCoeffs *c,
277
                   struct FFIIRFilterState *s, int size,
278
                   const int16_t *src, ptrdiff_t sstep,
279
                   int16_t *dst, ptrdiff_t dstep)
280
{
281
1
    if (c->order == 2) {
282
        FILTER_O2(int16_t, S16)
283
1
    } else if (c->order == 4) {
284
257
        FILTER_BW_O4(int16_t, S16)
285
    } else {
286
        FILTER_DIRECT_FORM_II(int16_t, S16)
287
    }
288
1
}
289
290
void ff_iir_filter_flt(const struct FFIIRFilterCoeffs *c,
291
                       struct FFIIRFilterState *s, int size,
292
                       const float *src, ptrdiff_t sstep,
293
                       float *dst, ptrdiff_t dstep)
294
{
295
    if (c->order == 2) {
296
        FILTER_O2(float, FLT)
297
    } else if (c->order == 4) {
298
        FILTER_BW_O4(float, FLT)
299
    } else {
300
        FILTER_DIRECT_FORM_II(float, FLT)
301
    }
302
}
303
304
1
av_cold void ff_iir_filter_free_statep(struct FFIIRFilterState **state)
305
{
306
1
    av_freep(state);
307
1
}
308
309
12
av_cold void ff_iir_filter_free_coeffsp(struct FFIIRFilterCoeffs **coeffsp)
310
{
311
12
    struct FFIIRFilterCoeffs *coeffs = *coeffsp;
312
12
    if (coeffs) {
313
1
        av_freep(&coeffs->cx);
314
1
        av_freep(&coeffs->cy);
315
    }
316
12
    av_freep(coeffsp);
317
12
}
318
319
11
void ff_iir_filter_init(FFIIRFilterContext *f) {
320
11
    f->filter_flt = ff_iir_filter_flt;
321
322
    if (HAVE_MIPSFPU)
323
        ff_iir_filter_init_mips(f);
324
11
}