ref: 2c65075425ac1ba118a3b520554dc165b28afe90
dir: /src/flanger.c/
/*
* This library 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 of the License, or (at
* your option) any later version.
*
* This library 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 this library. If not, write to the Free Software Foundation,
* Fifth Floor, 51 Franklin Street, Boston, MA 02111-1301, USA.
*/
/* Effect: Stereo Flanger (c) 2006 robs@users.sourceforge.net */
#define st_flanger_usage \
"Usage: flanger [delay depth regen width speed shape phase interp]\n"
/*
" .\n" \
" /|regen\n" \
" / |\n" \
" +--( |------------+\n" \
" | \\ | | .\n" \
" _V_ \\| _______ | |\\ width ___\n" \
" | | ' | | | | \\ | |\n" \
" +-->| + |---->| DELAY |--+-->| )----->| |\n" \
" | |___| |_______| | / | |\n" \
" | delay : depth |/ | |\n" \
" In | : interp ' | | Out\n" \
" --->+ __:__ | + |--->\n" \
" | | |speed | |\n" \
" | | ~ |shape | |\n" \
" | |_____|phase | |\n" \
" +------------------------------------->| |\n" \
" |___|\n" \
"\n" \
" RANGE DEFAULT DESCRIPTION\n" \
"delay 0 10 0 base delay in milliseconds\n" \
"depth 0 10 2 added swept delay in milliseconds\n" \
"regen -95 +95 0 percentage regeneration (delayed signal feedback)\n" \
"width 0 100 71 percentage of delayed signal mixed with original\n" \
"speed 0.1 10 0.5 sweeps per second (Hz) \n" \
"shape -- sin swept wave shape: sine|triangle\n" \
"phase 0 100 25 swept wave percentage phase-shift for multi-channel\n" \
" (e.g. stereo) flange; 0 = 100 = same phase on each channel\n" \
"interp -- lin delay-line interpolation: linear|quadratic"
*/
/* TODO: Slide in the delay at the start? */
#include "st_i.h"
#include <math.h>
#include <string.h>
typedef enum {INTERP_LINEAR, INTERP_QUADRATIC} interp_t;
#define MAX_CHANNELS 4
typedef struct flanger {
/* Parameters */
double delay_min;
double delay_depth;
double feedback_gain;
double delay_gain;
double speed;
st_wave_t wave_shape;
double channel_phase;
interp_t interpolation;
/* Delay buffers */
double * delay_bufs[MAX_CHANNELS];
st_size_t delay_buf_length;
st_size_t delay_buf_pos;
double delay_last[MAX_CHANNELS];
/* Low Frequency Oscillator */
float * lfo;
st_size_t lfo_length;
st_size_t lfo_pos;
/* Balancing */
double in_gain;
} * flanger_t;
assert_static(sizeof(struct flanger) <= ST_MAX_EFFECT_PRIVSIZE,
/* else */ flanger_PRIVSIZE_too_big);
static enum_item const interp_enum[] = {
ENUM_ITEM(INTERP_,LINEAR)
ENUM_ITEM(INTERP_,QUADRATIC)
{0, 0}};
#define NUMERIC_PARAMETER(p, min, max) { \
char * end_ptr; \
double d; \
if (argc == 0) break; \
d = strtod(*argv, &end_ptr); \
if (end_ptr != *argv) { \
if (d < min || d > max || *end_ptr != '\0') { \
st_fail(effp->h->usage); \
return ST_EOF; \
} \
f->p = d; \
--argc, ++argv; \
} \
}
#define TEXTUAL_PARAMETER(p, enum_table) { \
enum_item const * e; \
if (argc == 0) break; \
e = find_enum_text(*argv, enum_table); \
if (e != NULL) { \
f->p = e->value; \
--argc, ++argv; \
} \
}
static int st_flanger_getopts(eff_t effp, int argc, char *argv[])
{
flanger_t f = (flanger_t) effp->priv;
/* Set non-zero defaults: */
f->delay_depth = 2;
f->delay_gain = 71;
f->speed = 0.5;
f->channel_phase= 25;
do { /* break-able block */
NUMERIC_PARAMETER(delay_min , 0 , 10 )
NUMERIC_PARAMETER(delay_depth , 0 , 10 )
NUMERIC_PARAMETER(feedback_gain,-95 , 95 )
NUMERIC_PARAMETER(delay_gain , 0 , 100)
NUMERIC_PARAMETER(speed , 0.1, 10 )
TEXTUAL_PARAMETER(wave_shape, st_wave_enum)
NUMERIC_PARAMETER(channel_phase, 0 , 100)
TEXTUAL_PARAMETER(interpolation, interp_enum)
} while (0);
if (argc != 0) {
st_fail(effp->h->usage);
return ST_EOF;
}
st_report("parameters:\n"
"delay = %gms\n"
"depth = %gms\n"
"regen = %g%%\n"
"width = %g%%\n"
"speed = %gHz\n"
"shape = %s\n"
"phase = %g%%\n"
"interp= %s",
f->delay_min,
f->delay_depth,
f->feedback_gain,
f->delay_gain,
f->speed,
st_wave_enum[f->wave_shape].text,
f->channel_phase,
interp_enum[f->interpolation].text);
return ST_SUCCESS;
}
static int st_flanger_start(eff_t effp)
{
flanger_t f = (flanger_t) effp->priv;
int c, channels = effp->ininfo.channels;
if (channels > MAX_CHANNELS) {
st_fail("Can not operate with more than %i channels", MAX_CHANNELS);
return ST_EOF;
}
/* Scale percentages to unity: */
f->feedback_gain /= 100;
f->delay_gain /= 100;
f->channel_phase /= 100;
/* Balance output: */
f->in_gain = 1 / (1 + f->delay_gain);
f->delay_gain /= 1 + f->delay_gain;
/* Balance feedback loop: */
f->delay_gain *= 1 - fabs(f->feedback_gain);
st_debug("in_gain=%g feedback_gain=%g delay_gain=%g\n",
f->in_gain, f->feedback_gain, f->delay_gain);
/* Create the delay buffers, one for each channel: */
f->delay_buf_length =
(f->delay_min + f->delay_depth) / 1000 * effp->ininfo.rate + 0.5;
++f->delay_buf_length; /* Need 0 to n, i.e. n + 1. */
++f->delay_buf_length; /* Quadratic interpolator needs one more. */
for (c = 0; c < channels; ++c)
f->delay_bufs[c] = xcalloc(f->delay_buf_length, sizeof(*f->delay_bufs[0]));
/* Create the LFO lookup table: */
f->lfo_length = effp->ininfo.rate / f->speed;
f->lfo = xcalloc(f->lfo_length, sizeof(*f->lfo));
st_generate_wave_table(
f->wave_shape,
ST_FLOAT,
f->lfo,
f->lfo_length,
(st_size_t)(f->delay_min / 1000 * effp->ininfo.rate + .5),
f->delay_buf_length - 2,
3 * M_PI_2); /* Start the sweep at minimum delay (for mono at least) */
st_debug("delay_buf_length=%u lfo_length=%u\n",
f->delay_buf_length, f->lfo_length);
return ST_SUCCESS;
}
static int st_flanger_flow(eff_t effp, st_sample_t const * ibuf,
st_sample_t * obuf, st_size_t * isamp, st_size_t * osamp)
{
flanger_t f = (flanger_t) effp->priv;
int c, channels = effp->ininfo.channels;
st_size_t len = (*isamp > *osamp ? *osamp : *isamp) / channels;
*isamp = *osamp = len * channels;
while (len--) {
f->delay_buf_pos =
(f->delay_buf_pos + f->delay_buf_length - 1) % f->delay_buf_length;
for (c = 0; c < channels; ++c) {
double delayed_0, delayed_1;
double delayed;
double in, out;
st_size_t channel_phase = c * f->lfo_length * f->channel_phase + .5;
double delay = f->lfo[(f->lfo_pos + channel_phase) % f->lfo_length];
double frac_delay = modf(delay, &delay);
st_size_t int_delay = (size_t)delay;
in = *ibuf++;
f->delay_bufs[c][f->delay_buf_pos] = in + f->delay_last[c] * f->feedback_gain;
delayed_0 = f->delay_bufs[c]
[(f->delay_buf_pos + int_delay++) % f->delay_buf_length];
delayed_1 = f->delay_bufs[c]
[(f->delay_buf_pos + int_delay++) % f->delay_buf_length];
if (f->interpolation == INTERP_LINEAR)
delayed = delayed_0 + (delayed_1 - delayed_0) * frac_delay;
else /* if (f->interpolation == INTERP_QUADRATIC) */
{
double a, b;
double delayed_2 = f->delay_bufs[c]
[(f->delay_buf_pos + int_delay++) % f->delay_buf_length];
delayed_2 -= delayed_0;
delayed_1 -= delayed_0;
a = delayed_2 *.5 - delayed_1;
b = delayed_1 * 2 - delayed_2 *.5;
delayed = delayed_0 + (a * frac_delay + b) * frac_delay;
}
f->delay_last[c] = delayed;
out = in * f->in_gain + delayed * f->delay_gain;
*obuf++ = ST_ROUND_CLIP_COUNT(out, effp->clips);
}
f->lfo_pos = (f->lfo_pos + 1) % f->lfo_length;
}
return ST_SUCCESS;
}
static int st_flanger_stop(eff_t effp)
{
flanger_t f = (flanger_t) effp->priv;
int c, channels = effp->ininfo.channels;
for (c = 0; c < channels; ++c)
free(f->delay_bufs[c]);
free(f->lfo);
memset(f, 0, sizeof(*f));
return ST_SUCCESS;
}
static st_effect_t st_flanger_effect = {
"flanger",
st_flanger_usage,
ST_EFF_MCHAN,
st_flanger_getopts,
st_flanger_start,
st_flanger_flow,
st_effect_nothing_drain,
st_flanger_stop,
st_effect_nothing
};
st_effect_t const * st_flanger_effect_fn(void)
{
return &st_flanger_effect;
}