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/*
* Copyright (c) 2022 Paul B Mahol
*
* 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
*/
#include "libavutil/channel_layout.h"
#include "libavutil/opt.h"
#include "audio.h"
#include "avfilter.h"
#include "filters.h"
#include "formats.h"
#include <float.h>
typedef struct AudioVirtualBassContext {
const AVClass *class;
double cutoff;
double strength;
double a[3], m[3], cf[2];
} AudioVirtualBassContext;
#define OFFSET(x) offsetof(AudioVirtualBassContext, x)
#define TFLAGS AV_OPT_FLAG_AUDIO_PARAM | AV_OPT_FLAG_FILTERING_PARAM | AV_OPT_FLAG_RUNTIME_PARAM
#define FLAGS AV_OPT_FLAG_AUDIO_PARAM | AV_OPT_FLAG_FILTERING_PARAM
static const AVOption virtualbass_options[] = {
{ "cutoff", "set virtual bass cutoff", OFFSET(cutoff), AV_OPT_TYPE_DOUBLE, {.dbl=250},100,500, FLAGS },
{ "strength", "set virtual bass strength", OFFSET(strength), AV_OPT_TYPE_DOUBLE, {.dbl=3}, 0.5, 3, TFLAGS },
{NULL}
};
AVFILTER_DEFINE_CLASS(virtualbass);
static int query_formats(AVFilterContext *ctx)
{
AVFilterChannelLayouts *in_layout = NULL, *out_layout = NULL;
AVFilterFormats *formats = NULL;
int ret;
if ((ret = ff_add_format (&formats, AV_SAMPLE_FMT_DBLP )) < 0 ||
(ret = ff_set_common_formats (ctx, formats )) < 0 ||
(ret = ff_add_channel_layout (&in_layout, &(AVChannelLayout)AV_CHANNEL_LAYOUT_STEREO)) < 0 ||
(ret = ff_channel_layouts_ref(in_layout, &ctx->inputs[0]->outcfg.channel_layouts)) < 0 ||
(ret = ff_add_channel_layout (&out_layout, &(AVChannelLayout)AV_CHANNEL_LAYOUT_2POINT1)) < 0 ||
(ret = ff_channel_layouts_ref(out_layout, &ctx->outputs[0]->incfg.channel_layouts)) < 0)
return ret;
return ff_set_common_all_samplerates(ctx);
}
static int config_input(AVFilterLink *inlink)
{
AVFilterContext *ctx = inlink->dst;
AudioVirtualBassContext *s = ctx->priv;
const double Q = 0.707;
double g, k;
g = tan(M_PI * s->cutoff / inlink->sample_rate);
k = 1. / Q;
s->a[0] = 1. / (1. + g * (g + k));
s->a[1] = g * s->a[0];
s->a[2] = g * s->a[1];
s->m[0] = 0.;
s->m[1] = 0.;
s->m[2] = 1.;
return 0;
}
#define SQR(x) ((x) * (x))
static double vb_fun(double x)
{
double y = 2.5 * atan(0.9 * x) + 2.5 * sqrt(1. - SQR(0.9 * x)) - 2.5;
return y < 0. ? sin(y) : y;
}
static void vb_stereo(AVFilterContext *ctx, AVFrame *out, AVFrame *in)
{
AudioVirtualBassContext *s = ctx->priv;
const double *lsrc = (const double *)in->extended_data[0];
const double *rsrc = (const double *)in->extended_data[1];
double *ldst = (double *)out->extended_data[0];
double *rdst = (double *)out->extended_data[1];
double *lfe = (double *)out->extended_data[2];
const double st = M_PI / s->strength;
const double a0 = s->a[0];
const double a1 = s->a[1];
const double a2 = s->a[2];
const double m0 = s->m[0];
const double m1 = s->m[1];
const double m2 = s->m[2];
double b0 = s->cf[0];
double b1 = s->cf[1];
memcpy(ldst, lsrc, in->nb_samples * sizeof(double));
memcpy(rdst, rsrc, in->nb_samples * sizeof(double));
for (int n = 0; n < in->nb_samples; n++) {
const double center = (lsrc[n] + rsrc[n]) * 0.5;
const double v0 = center;
const double v3 = v0 - b1;
const double v1 = a0 * b0 + a1 * v3;
const double v2 = b1 + a1 * b0 + a2 * v3;
double b, vb;
b0 = 2. * v1 - b0;
b1 = 2. * v2 - b1;
b = m0 * v0 + m1 * v1 + m2 * v2;
vb = sin(vb_fun(b) * st);
lfe[n] = vb;
}
s->cf[0] = b0;
s->cf[1] = b1;
}
static int filter_frame(AVFilterLink *inlink, AVFrame *in)
{
AVFilterContext *ctx = inlink->dst;
AVFilterLink *outlink = ctx->outputs[0];
AVFrame *out;
out = ff_get_audio_buffer(outlink, in->nb_samples);
if (!out) {
av_frame_free(&in);
return AVERROR(ENOMEM);
}
av_frame_copy_props(out, in);
vb_stereo(ctx, out, in);
av_frame_free(&in);
return ff_filter_frame(outlink, out);
}
static const AVFilterPad inputs[] = {
{
.name = "default",
.type = AVMEDIA_TYPE_AUDIO,
.filter_frame = filter_frame,
.config_props = config_input,
},
};
const AVFilter ff_af_virtualbass = {
.name = "virtualbass",
.description = NULL_IF_CONFIG_SMALL("Audio Virtual Bass."),
.priv_size = sizeof(AudioVirtualBassContext),
.priv_class = &virtualbass_class,
FILTER_INPUTS(inputs),
FILTER_OUTPUTS(ff_audio_default_filterpad),
FILTER_QUERY_FUNC(query_formats),
.flags = AVFILTER_FLAG_SUPPORT_TIMELINE_INTERNAL,
.process_command = ff_filter_process_command,
};
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