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FFmpeg/libavfilter/asrc_anoisesrc.c
George Boyle 6e156075b0 avfilter: Add blue and violet noise generation filters 
For the blue and violet noise, I took the pink and brown noise
respectively and subtracted the offsets instead of adding them. When I
eyeball the frequency spectrum of the resulting outputs it looks correct
to me, i.e. the blue graph appears to be a mirror image of the pink, and
the same can be said of the violet and the brown. I did not do anything
else to confirm the correctness.
2017-07-19 19:51:04 +02:00

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/*
* Copyright (c) 2015 Kyle Swanson <k@ylo.ph>.
*
* 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/opt.h"
#include "audio.h"
#include "avfilter.h"
#include "internal.h"
#include "libavutil/lfg.h"
#include "libavutil/random_seed.h"
typedef struct ANoiseSrcContext {
const AVClass *class;
int sample_rate;
double amplitude;
int64_t duration;
int64_t color;
int64_t seed;
int nb_samples;
int64_t pts;
int infinite;
double (*filter)(double white, double *buf);
double buf[7];
AVLFG c;
} ANoiseSrcContext;
enum NoiseMode {
NM_WHITE,
NM_PINK,
NM_BROWN,
NM_BLUE,
NM_VIOLET,
NM_NB
};
#define OFFSET(x) offsetof(ANoiseSrcContext, x)
#define FLAGS AV_OPT_FLAG_AUDIO_PARAM|AV_OPT_FLAG_FILTERING_PARAM
static const AVOption anoisesrc_options[] = {
{ "sample_rate", "set sample rate", OFFSET(sample_rate), AV_OPT_TYPE_INT, {.i64 = 48000}, 15, INT_MAX, FLAGS },
{ "r", "set sample rate", OFFSET(sample_rate), AV_OPT_TYPE_INT, {.i64 = 48000}, 15, INT_MAX, FLAGS },
{ "amplitude", "set amplitude", OFFSET(amplitude), AV_OPT_TYPE_DOUBLE, {.dbl = 1.}, 0., 1., FLAGS },
{ "a", "set amplitude", OFFSET(amplitude), AV_OPT_TYPE_DOUBLE, {.dbl = 1.}, 0., 1., FLAGS },
{ "duration", "set duration", OFFSET(duration), AV_OPT_TYPE_DURATION, {.i64 = 0}, 0, INT64_MAX, FLAGS },
{ "d", "set duration", OFFSET(duration), AV_OPT_TYPE_DURATION, {.i64 = 0}, 0, INT64_MAX, FLAGS },
{ "color", "set noise color", OFFSET(color), AV_OPT_TYPE_INT, {.i64 = 0}, 0, NM_NB - 1, FLAGS, "color" },
{ "colour", "set noise color", OFFSET(color), AV_OPT_TYPE_INT, {.i64 = 0}, 0, NM_NB - 1, FLAGS, "color" },
{ "c", "set noise color", OFFSET(color), AV_OPT_TYPE_INT, {.i64 = 0}, 0, NM_NB - 1, FLAGS, "color" },
{ "white", 0, 0, AV_OPT_TYPE_CONST, {.i64 = NM_WHITE}, 0, 0, FLAGS, "color" },
{ "pink", 0, 0, AV_OPT_TYPE_CONST, {.i64 = NM_PINK}, 0, 0, FLAGS, "color" },
{ "brown", 0, 0, AV_OPT_TYPE_CONST, {.i64 = NM_BROWN}, 0, 0, FLAGS, "color" },
{ "blue", 0, 0, AV_OPT_TYPE_CONST, {.i64 = NM_BLUE}, 0, 0, FLAGS, "color" },
{ "violet", 0, 0, AV_OPT_TYPE_CONST, {.i64 = NM_VIOLET}, 0, 0, FLAGS, "color" },
{ "seed", "set random seed", OFFSET(seed), AV_OPT_TYPE_INT64, {.i64 = -1}, -1, UINT_MAX, FLAGS },
{ "s", "set random seed", OFFSET(seed), AV_OPT_TYPE_INT64, {.i64 = -1}, -1, UINT_MAX, FLAGS },
{ "nb_samples", "set the number of samples per requested frame", OFFSET(nb_samples), AV_OPT_TYPE_INT, {.i64 = 1024}, 1, INT_MAX, FLAGS },
{ "n", "set the number of samples per requested frame", OFFSET(nb_samples), AV_OPT_TYPE_INT, {.i64 = 1024}, 1, INT_MAX, FLAGS },
{NULL}
};
AVFILTER_DEFINE_CLASS(anoisesrc);
static av_cold int query_formats(AVFilterContext *ctx)
{
ANoiseSrcContext *s = ctx->priv;
static const int64_t chlayouts[] = { AV_CH_LAYOUT_MONO, -1 };
int sample_rates[] = { s->sample_rate, -1 };
static const enum AVSampleFormat sample_fmts[] = {
AV_SAMPLE_FMT_DBL,
AV_SAMPLE_FMT_NONE
};
AVFilterFormats *formats;
AVFilterChannelLayouts *layouts;
int ret;
formats = ff_make_format_list(sample_fmts);
if (!formats)
return AVERROR(ENOMEM);
ret = ff_set_common_formats (ctx, formats);
if (ret < 0)
return ret;
layouts = avfilter_make_format64_list(chlayouts);
if (!layouts)
return AVERROR(ENOMEM);
ret = ff_set_common_channel_layouts(ctx, layouts);
if (ret < 0)
return ret;
formats = ff_make_format_list(sample_rates);
if (!formats)
return AVERROR(ENOMEM);
return ff_set_common_samplerates(ctx, formats);
}
static double white_filter(double white, double *buf)
{
return white;
}
static double pink_filter(double white, double *buf)
{
double pink;
/* http://www.musicdsp.org/files/pink.txt */
buf[0] = 0.99886 * buf[0] + white * 0.0555179;
buf[1] = 0.99332 * buf[1] + white * 0.0750759;
buf[2] = 0.96900 * buf[2] + white * 0.1538520;
buf[3] = 0.86650 * buf[3] + white * 0.3104856;
buf[4] = 0.55000 * buf[4] + white * 0.5329522;
buf[5] = -0.7616 * buf[5] - white * 0.0168980;
pink = buf[0] + buf[1] + buf[2] + buf[3] + buf[4] + buf[5] + buf[6] + white * 0.5362;
buf[6] = white * 0.115926;
return pink * 0.11;
}
static double blue_filter(double white, double *buf)
{
double blue;
/* Same as pink_filter but subtract the offsets rather than add */
buf[0] = 0.0555179 * white - 0.99886 * buf[0];
buf[1] = 0.0750759 * white - 0.99332 * buf[1];
buf[2] = 0.1538520 * white - 0.96900 * buf[2];
buf[3] = 0.3104856 * white - 0.86650 * buf[3];
buf[4] = 0.5329522 * white - 0.55000 * buf[4];
buf[5] = -0.016898 * white + 0.76160 * buf[5];
blue = buf[0] + buf[1] + buf[2] + buf[3] + buf[4] + buf[5] + buf[6] + white * 0.5362;
buf[6] = white * 0.115926;
return blue * 0.11;
}
static double brown_filter(double white, double *buf)
{
double brown;
brown = ((0.02 * white) + buf[0]) / 1.02;
buf[0] = brown;
return brown * 3.5;
}
static double violet_filter(double white, double *buf)
{
double violet;
violet = ((0.02 * white) - buf[0]) / 1.02;
buf[0] = violet;
return violet * 3.5;
}
static av_cold int config_props(AVFilterLink *outlink)
{
AVFilterContext *ctx = outlink->src;
ANoiseSrcContext *s = ctx->priv;
if (s->seed == -1)
s->seed = av_get_random_seed();
av_lfg_init(&s->c, s->seed);
if (s->duration == 0)
s->infinite = 1;
s->duration = av_rescale(s->duration, s->sample_rate, AV_TIME_BASE);
switch (s->color) {
case NM_WHITE: s->filter = white_filter; break;
case NM_PINK: s->filter = pink_filter; break;
case NM_BROWN: s->filter = brown_filter; break;
case NM_BLUE: s->filter = blue_filter; break;
case NM_VIOLET: s->filter = violet_filter; break;
}
return 0;
}
static int request_frame(AVFilterLink *outlink)
{
AVFilterContext *ctx = outlink->src;
ANoiseSrcContext *s = ctx->priv;
AVFrame *frame;
int nb_samples, i;
double *dst;
if (!s->infinite && s->duration <= 0) {
return AVERROR_EOF;
} else if (!s->infinite && s->duration < s->nb_samples) {
nb_samples = s->duration;
} else {
nb_samples = s->nb_samples;
}
if (!(frame = ff_get_audio_buffer(outlink, nb_samples)))
return AVERROR(ENOMEM);
dst = (double *)frame->data[0];
for (i = 0; i < nb_samples; i++) {
double white;
white = s->amplitude * ((2 * ((double) av_lfg_get(&s->c) / 0xffffffff)) - 1);
dst[i] = s->filter(white, s->buf);
}
if (!s->infinite)
s->duration -= nb_samples;
frame->pts = s->pts;
s->pts += nb_samples;
return ff_filter_frame(outlink, frame);
}
static const AVFilterPad anoisesrc_outputs[] = {
{
.name = "default",
.type = AVMEDIA_TYPE_AUDIO,
.request_frame = request_frame,
.config_props = config_props,
},
{ NULL }
};
AVFilter ff_asrc_anoisesrc = {
.name = "anoisesrc",
.description = NULL_IF_CONFIG_SMALL("Generate a noise audio signal."),
.query_formats = query_formats,
.priv_size = sizeof(ANoiseSrcContext),
.inputs = NULL,
.outputs = anoisesrc_outputs,
.priv_class = &anoisesrc_class,
};
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