347 lines
10 KiB
C
347 lines
10 KiB
C
/*
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* Copyright (c) Markus Schmidt and Christian Holschuh
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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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#include "libavutil/opt.h"
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#include "avfilter.h"
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#include "internal.h"
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#include "audio.h"
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typedef struct LFOContext {
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double freq;
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double offset;
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int srate;
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double amount;
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double pwidth;
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double phase;
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} LFOContext;
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typedef struct SRContext {
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double target;
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double real;
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double samples;
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double last;
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} SRContext;
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typedef struct ACrusherContext {
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const AVClass *class;
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double level_in;
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double level_out;
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double bits;
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double mix;
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int mode;
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double dc;
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double idc;
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double aa;
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double samples;
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int is_lfo;
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double lforange;
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double lforate;
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double sqr;
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double aa1;
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double coeff;
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int round;
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double sov;
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double smin;
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double sdiff;
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LFOContext lfo;
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SRContext *sr;
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} ACrusherContext;
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#define OFFSET(x) offsetof(ACrusherContext, x)
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#define A AV_OPT_FLAG_AUDIO_PARAM|AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_RUNTIME_PARAM
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static const AVOption acrusher_options[] = {
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{ "level_in", "set level in", OFFSET(level_in), AV_OPT_TYPE_DOUBLE, {.dbl=1}, 0.015625, 64, A },
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{ "level_out","set level out", OFFSET(level_out), AV_OPT_TYPE_DOUBLE, {.dbl=1}, 0.015625, 64, A },
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{ "bits", "set bit reduction", OFFSET(bits), AV_OPT_TYPE_DOUBLE, {.dbl=8}, 1, 64, A },
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{ "mix", "set mix", OFFSET(mix), AV_OPT_TYPE_DOUBLE, {.dbl=.5}, 0, 1, A },
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{ "mode", "set mode", OFFSET(mode), AV_OPT_TYPE_INT, {.i64=0}, 0, 1, A, "mode" },
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{ "lin", "linear", 0, AV_OPT_TYPE_CONST, {.i64=0}, 0, 0, A, "mode" },
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{ "log", "logarithmic", 0, AV_OPT_TYPE_CONST, {.i64=1}, 0, 0, A, "mode" },
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{ "dc", "set DC", OFFSET(dc), AV_OPT_TYPE_DOUBLE, {.dbl=1}, .25, 4, A },
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{ "aa", "set anti-aliasing", OFFSET(aa), AV_OPT_TYPE_DOUBLE, {.dbl=.5}, 0, 1, A },
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{ "samples", "set sample reduction", OFFSET(samples), AV_OPT_TYPE_DOUBLE, {.dbl=1}, 1, 250, A },
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{ "lfo", "enable LFO", OFFSET(is_lfo), AV_OPT_TYPE_BOOL, {.i64=0}, 0, 1, A },
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{ "lforange", "set LFO depth", OFFSET(lforange), AV_OPT_TYPE_DOUBLE, {.dbl=20}, 1, 250, A },
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{ "lforate", "set LFO rate", OFFSET(lforate), AV_OPT_TYPE_DOUBLE, {.dbl=.3}, .01, 200, A },
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{ NULL }
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};
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AVFILTER_DEFINE_CLASS(acrusher);
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static double samplereduction(ACrusherContext *s, SRContext *sr, double in)
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{
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sr->samples++;
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if (sr->samples >= s->round) {
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sr->target += s->samples;
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sr->real += s->round;
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if (sr->target + s->samples >= sr->real + 1) {
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sr->last = in;
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sr->target = 0;
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sr->real = 0;
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}
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sr->samples = 0;
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}
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return sr->last;
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}
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static double add_dc(double s, double dc, double idc)
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{
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return s > 0 ? s * dc : s * idc;
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}
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static double remove_dc(double s, double dc, double idc)
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{
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return s > 0 ? s * idc : s * dc;
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}
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static inline double factor(double y, double k, double aa1, double aa)
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{
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return 0.5 * (sin(M_PI * (fabs(y - k) - aa1) / aa - M_PI_2) + 1);
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}
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static double bitreduction(ACrusherContext *s, double in)
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{
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const double sqr = s->sqr;
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const double coeff = s->coeff;
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const double aa = s->aa;
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const double aa1 = s->aa1;
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double y, k;
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// add dc
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in = add_dc(in, s->dc, s->idc);
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// main rounding calculation depending on mode
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// the idea for anti-aliasing:
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// you need a function f which brings you to the scale, where
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// you want to round and the function f_b (with f(f_b)=id) which
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// brings you back to your original scale.
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//
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// then you can use the logic below in the following way:
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// y = f(in) and k = roundf(y)
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// if (y > k + aa1)
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// k = f_b(k) + ( f_b(k+1) - f_b(k) ) * 0.5 * (sin(x - PI/2) + 1)
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// if (y < k + aa1)
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// k = f_b(k) - ( f_b(k+1) - f_b(k) ) * 0.5 * (sin(x - PI/2) + 1)
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//
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// whereas x = (fabs(f(in) - k) - aa1) * PI / aa
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// for both cases.
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switch (s->mode) {
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case 0:
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default:
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// linear
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y = in * coeff;
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k = roundf(y);
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if (k - aa1 <= y && y <= k + aa1) {
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k /= coeff;
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} else if (y > k + aa1) {
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k = k / coeff + ((k + 1) / coeff - k / coeff) *
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factor(y, k, aa1, aa);
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} else {
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k = k / coeff - (k / coeff - (k - 1) / coeff) *
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factor(y, k, aa1, aa);
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}
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break;
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case 1:
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// logarithmic
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y = sqr * log(fabs(in)) + sqr * sqr;
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k = roundf(y);
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if(!in) {
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k = 0;
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} else if (k - aa1 <= y && y <= k + aa1) {
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k = in / fabs(in) * exp(k / sqr - sqr);
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} else if (y > k + aa1) {
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double x = exp(k / sqr - sqr);
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k = FFSIGN(in) * (x + (exp((k + 1) / sqr - sqr) - x) *
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factor(y, k, aa1, aa));
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} else {
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double x = exp(k / sqr - sqr);
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k = in / fabs(in) * (x - (x - exp((k - 1) / sqr - sqr)) *
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factor(y, k, aa1, aa));
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}
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break;
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}
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// mix between dry and wet signal
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k += (in - k) * s->mix;
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// remove dc
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k = remove_dc(k, s->dc, s->idc);
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return k;
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}
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static double lfo_get(LFOContext *lfo)
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{
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double phs = FFMIN(100., lfo->phase / FFMIN(1.99, FFMAX(0.01, lfo->pwidth)) + lfo->offset);
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double val;
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if (phs > 1)
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phs = fmod(phs, 1.);
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val = sin((phs * 360.) * M_PI / 180);
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return val * lfo->amount;
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}
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static void lfo_advance(LFOContext *lfo, unsigned count)
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{
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lfo->phase = fabs(lfo->phase + count * lfo->freq * (1. / lfo->srate));
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if (lfo->phase >= 1.)
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lfo->phase = fmod(lfo->phase, 1.);
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}
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static int filter_frame(AVFilterLink *inlink, AVFrame *in)
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{
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AVFilterContext *ctx = inlink->dst;
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ACrusherContext *s = ctx->priv;
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AVFilterLink *outlink = ctx->outputs[0];
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AVFrame *out;
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const double *src = (const double *)in->data[0];
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double *dst;
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const double level_in = s->level_in;
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const double level_out = s->level_out;
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const double mix = s->mix;
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int n, c;
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if (av_frame_is_writable(in)) {
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out = in;
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} else {
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out = ff_get_audio_buffer(inlink, in->nb_samples);
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if (!out) {
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av_frame_free(&in);
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return AVERROR(ENOMEM);
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}
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av_frame_copy_props(out, in);
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}
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dst = (double *)out->data[0];
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for (n = 0; n < in->nb_samples; n++) {
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if (s->is_lfo) {
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s->samples = s->smin + s->sdiff * (lfo_get(&s->lfo) + 0.5);
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s->round = round(s->samples);
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}
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for (c = 0; c < inlink->ch_layout.nb_channels; c++) {
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double sample = src[c] * level_in;
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sample = mix * samplereduction(s, &s->sr[c], sample) + src[c] * (1. - mix) * level_in;
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dst[c] = ctx->is_disabled ? src[c] : bitreduction(s, sample) * level_out;
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}
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src += c;
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dst += c;
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if (s->is_lfo)
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lfo_advance(&s->lfo, 1);
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}
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if (in != out)
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av_frame_free(&in);
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return ff_filter_frame(outlink, out);
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}
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static av_cold void uninit(AVFilterContext *ctx)
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{
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ACrusherContext *s = ctx->priv;
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av_freep(&s->sr);
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}
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static int config_input(AVFilterLink *inlink)
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{
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AVFilterContext *ctx = inlink->dst;
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ACrusherContext *s = ctx->priv;
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double rad, sunder, smax, sover;
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s->idc = 1. / s->dc;
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s->coeff = exp2(s->bits) - 1;
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s->sqr = sqrt(s->coeff / 2);
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s->aa1 = (1. - s->aa) / 2.;
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s->round = round(s->samples);
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rad = s->lforange / 2.;
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s->smin = FFMAX(s->samples - rad, 1.);
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sunder = s->samples - rad - s->smin;
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smax = FFMIN(s->samples + rad, 250.);
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sover = s->samples + rad - smax;
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smax -= sunder;
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s->smin -= sover;
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s->sdiff = smax - s->smin;
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s->lfo.freq = s->lforate;
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s->lfo.pwidth = 1.;
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s->lfo.srate = inlink->sample_rate;
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s->lfo.amount = .5;
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if (!s->sr)
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s->sr = av_calloc(inlink->ch_layout.nb_channels, sizeof(*s->sr));
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if (!s->sr)
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return AVERROR(ENOMEM);
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return 0;
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}
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static int process_command(AVFilterContext *ctx, const char *cmd, const char *args,
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char *res, int res_len, int flags)
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{
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AVFilterLink *inlink = ctx->inputs[0];
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int ret;
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ret = ff_filter_process_command(ctx, cmd, args, res, res_len, flags);
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if (ret < 0)
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return ret;
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return config_input(inlink);
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}
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static const AVFilterPad avfilter_af_acrusher_inputs[] = {
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{
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.name = "default",
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.type = AVMEDIA_TYPE_AUDIO,
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.config_props = config_input,
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.filter_frame = filter_frame,
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},
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};
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static const AVFilterPad avfilter_af_acrusher_outputs[] = {
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{
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.name = "default",
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.type = AVMEDIA_TYPE_AUDIO,
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},
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};
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const AVFilter ff_af_acrusher = {
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.name = "acrusher",
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.description = NULL_IF_CONFIG_SMALL("Reduce audio bit resolution."),
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.priv_size = sizeof(ACrusherContext),
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.priv_class = &acrusher_class,
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.uninit = uninit,
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FILTER_INPUTS(avfilter_af_acrusher_inputs),
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FILTER_OUTPUTS(avfilter_af_acrusher_outputs),
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FILTER_SINGLE_SAMPLEFMT(AV_SAMPLE_FMT_DBL),
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.process_command = process_command,
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.flags = AVFILTER_FLAG_SUPPORT_TIMELINE_INTERNAL,
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};
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