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/*
* 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/ffmath.h"
#include "libavutil/opt.h"
#include "avfilter.h"
#include "audio.h"
#define MAX_ORDER 30
typedef struct Coeffs {
double g;
double a1;
double b0, b1;
} Coeffs;
typedef struct ATiltContext {
const AVClass *class;
double freq;
double level;
double slope;
double width;
int order;
Coeffs coeffs[MAX_ORDER];
AVFrame *w;
int (*filter_channels)(AVFilterContext *ctx, void *arg, int jobnr, int nb_jobs);
} ATiltContext;
static double prewarp(double w, double T, double wp)
{
return wp * tan(w * T * 0.5) / tan(wp * T * 0.5);
}
static double mz(int i, double w0, double r, double alpha)
{
return w0 * pow(r, -alpha + i);
}
static double mp(int i, double w0, double r)
{
return w0 * pow(r, i);
}
static double mzh(int i, double T, double w0, double r, double alpha)
{
return prewarp(mz(i, w0, r, alpha), T, w0);
}
static double mph(int i, double T, double w0, double r)
{
return prewarp(mp(i, w0, r), T, w0);
}
static void set_tf1s(Coeffs *coeffs, double b1, double b0, double a0,
double w1, double sr, double alpha)
{
double c = 1.0 / tan(w1 * 0.5 / sr);
double d = a0 + c;
coeffs->b1 = (b0 - b1 * c) / d;
coeffs->b0 = (b0 + b1 * c) / d;
coeffs->a1 = (a0 - c) / d;
coeffs->g = a0 / b0;
}
static void set_filter(AVFilterContext *ctx,
int order, double sr, double f0,
double bw, double alpha)
{
ATiltContext *s = ctx->priv;
const double w0 = 2. * M_PI * f0;
const double f1 = f0 + bw;
const double w1 = 1.;
const double r = pow(f1 / f0, 1.0 / (order - 1.0));
const double T = 1. / sr;
for (int i = 0; i < order; i++) {
Coeffs *coeffs = &s->coeffs[i];
set_tf1s(coeffs, 1.0, mzh(i, T, w0, r, alpha), mph(i, T, w0, r),
w1, sr, alpha);
}
}
static int get_coeffs(AVFilterContext *ctx)
{
ATiltContext *s = ctx->priv;
AVFilterLink *inlink = ctx->inputs[0];
set_filter(ctx, s->order, inlink->sample_rate, s->freq, s->width, s->slope);
return 0;
}
typedef struct ThreadData {
AVFrame *in, *out;
} ThreadData;
#define FILTER(name, type) \
static int filter_channels_## name(AVFilterContext *ctx, void *arg, \
int jobnr, int nb_jobs) \
{ \
ATiltContext *s = ctx->priv; \
ThreadData *td = arg; \
AVFrame *out = td->out; \
AVFrame *in = td->in; \
const int start = (in->ch_layout.nb_channels * jobnr) / nb_jobs; \
const int end = (in->ch_layout.nb_channels * (jobnr+1)) / nb_jobs; \
const type level = s->level; \
\
for (int ch = start; ch < end; ch++) { \
const type *src = (const type *)in->extended_data[ch]; \
type *dst = (type *)out->extended_data[ch]; \
\
for (int b = 0; b < s->order; b++) { \
Coeffs *coeffs = &s->coeffs[b]; \
const type g = coeffs->g; \
const type a1 = coeffs->a1; \
const type b0 = coeffs->b0; \
const type b1 = coeffs->b1; \
type *w = ((type *)s->w->extended_data[ch]) + b * 2; \
\
for (int n = 0; n < in->nb_samples; n++) { \
type sain = b ? dst[n] : src[n] * level; \
type saout = sain * b0 + w[0] * b1 - w[1] * a1; \
\
w[0] = sain; \
w[1] = saout; \
\
dst[n] = saout * g; \
} \
} \
} \
\
return 0; \
}
FILTER(fltp, float)
FILTER(dblp, double)
static int config_input(AVFilterLink *inlink)
{
AVFilterContext *ctx = inlink->dst;
ATiltContext *s = ctx->priv;
switch (inlink->format) {
case AV_SAMPLE_FMT_FLTP: s->filter_channels = filter_channels_fltp; break;
case AV_SAMPLE_FMT_DBLP: s->filter_channels = filter_channels_dblp; break;
}
s->w = ff_get_audio_buffer(inlink, 2 * MAX_ORDER);
if (!s->w)
return AVERROR(ENOMEM);
return get_coeffs(ctx);
}
static int filter_frame(AVFilterLink *inlink, AVFrame *in)
{
AVFilterContext *ctx = inlink->dst;
ATiltContext *s = ctx->priv;
AVFilterLink *outlink = ctx->outputs[0];
ThreadData td;
AVFrame *out;
if (av_frame_is_writable(in)) {
out = in;
} else {
out = ff_get_audio_buffer(outlink, in->nb_samples);
if (!out) {
av_frame_free(&in);
return AVERROR(ENOMEM);
}
av_frame_copy_props(out, in);
}
td.in = in; td.out = out;
ff_filter_execute(ctx, s->filter_channels, &td, NULL, FFMIN(inlink->ch_layout.nb_channels,
ff_filter_get_nb_threads(ctx)));
if (out != in)
av_frame_free(&in);
return ff_filter_frame(outlink, out);
}
static int process_command(AVFilterContext *ctx, const char *cmd, const char *args,
char *res, int res_len, int flags)
{
int ret;
ret = ff_filter_process_command(ctx, cmd, args, res, res_len, flags);
if (ret < 0)
return ret;
return get_coeffs(ctx);
}
static av_cold void uninit(AVFilterContext *ctx)
{
ATiltContext *s = ctx->priv;
av_frame_free(&s->w);
}
#define OFFSET(x) offsetof(ATiltContext, x)
#define FLAGS AV_OPT_FLAG_AUDIO_PARAM|AV_OPT_FLAG_FILTERING_PARAM|AV_OPT_FLAG_RUNTIME_PARAM
static const AVOption atilt_options[] = {
{ "freq", "set central frequency",OFFSET(freq), AV_OPT_TYPE_DOUBLE, {.dbl=10000}, 20, 192000, FLAGS },
{ "slope", "set filter slope", OFFSET(slope), AV_OPT_TYPE_DOUBLE, {.dbl=0}, -1, 1, FLAGS },
{ "width", "set filter width", OFFSET(width), AV_OPT_TYPE_DOUBLE, {.dbl=1000}, 100, 10000, FLAGS },
{ "order", "set filter order", OFFSET(order), AV_OPT_TYPE_INT, {.i64=5}, 2,MAX_ORDER, FLAGS },
{ "level", "set input level", OFFSET(level), AV_OPT_TYPE_DOUBLE, {.dbl=1.}, 0., 4., FLAGS },
{ NULL }
};
AVFILTER_DEFINE_CLASS(atilt);
static const AVFilterPad inputs[] = {
{
.name = "default",
.type = AVMEDIA_TYPE_AUDIO,
.filter_frame = filter_frame,
.config_props = config_input,
},
};
const AVFilter ff_af_atilt = {
.name = "atilt",
.description = NULL_IF_CONFIG_SMALL("Apply spectral tilt to audio."),
.priv_size = sizeof(ATiltContext),
.priv_class = &atilt_class,
.uninit = uninit,
FILTER_INPUTS(inputs),
FILTER_OUTPUTS(ff_audio_default_filterpad),
FILTER_SAMPLEFMTS(AV_SAMPLE_FMT_FLTP, AV_SAMPLE_FMT_DBLP),
.process_command = process_command,
.flags = AVFILTER_FLAG_SUPPORT_TIMELINE_GENERIC |
AVFILTER_FLAG_SLICE_THREADS,
};
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