ref: ee69779a3e0547fa25c98df3f3ce6fd5fd64829e
dir: /src/echo.c/
/*
* August 24, 1998
* Copyright (C) 1998 Juergen Mueller And Sundry Contributors
* This source code is freely redistributable and may be used for
* any purpose. This copyright notice must be maintained.
* Juergen Mueller And Sundry Contributors are not responsible for
* the consequences of using this software.
*/
/*
* This is the "echo.c" while the old "echo.c" from version 12 moves to
* "reverb.c" satisfying the definitions made in the Guitar FX FAQ.
*
*
* Echo effect for dsp.
*
* Flow diagram scheme for n delays ( 1 <= n <= MAX_ECHOS ):
*
* * gain-in ___
* ibuff -----------+------------------------------------------>| |
* | _________ | |
* | | | * decay 1 | |
* +----->| delay 1 |------------------------->| |
* | |_________| | |
* | _________ | + |
* | | | * decay 2 | |
* +---------->| delay 2 |-------------------->| |
* | |_________| | |
* : _________ | |
* | | | * decay n | |
* +--------------->| delay n |--------------->|___|
* |_________| |
* | * gain-out
* |
* +----->obuff
*
* Usage:
* echo gain-in gain-out delay-1 decay-1 [delay-2 decay-2 ... delay-n decay-n]
*
* Where:
* gain-in, decay-1 ... decay-n : 0.0 ... 1.0 volume
* gain-out : 0.0 ... volume
* delay-1 ... delay-n : > 0.0 msec
*
* Note:
* when decay is close to 1.0, the samples can begin clipping and the output
* can saturate!
*
* Hint:
* 1 / out-gain > gain-in ( 1 + decay-1 + ... + decay-n )
*
*/
/*
* Sound Tools reverb effect file.
*/
#include <stdlib.h> /* Harmless, and prototypes atof() etc. --dgc */
#include <math.h>
#include "st_i.h"
static st_effect_t st_echo_effect;
#define DELAY_BUFSIZ ( 50L * ST_MAXRATE )
#define MAX_ECHOS 7 /* 24 bit x ( 1 + MAX_ECHOS ) = */
/* 24 bit x 8 = 32 bit !!! */
/* Private data for SKEL file */
typedef struct echostuff {
int counter;
int num_delays;
double *delay_buf;
float in_gain, out_gain;
float delay[MAX_ECHOS], decay[MAX_ECHOS];
st_ssize_t samples[MAX_ECHOS], maxsamples;
st_size_t fade_out;
} *echo_t;
/* Private data for SKEL file */
/*
* Process options
*/
static int st_echo_getopts(eff_t effp, int n, char **argv)
{
echo_t echo = (echo_t) effp->priv;
int i;
echo->num_delays = 0;
if ((n < 4) || (n % 2))
{
st_fail(st_echo_effect.usage);
return (ST_EOF);
}
i = 0;
sscanf(argv[i++], "%f", &echo->in_gain);
sscanf(argv[i++], "%f", &echo->out_gain);
while (i < n) {
if ( echo->num_delays >= MAX_ECHOS )
st_fail("echo: to many delays, use less than %i delays",
MAX_ECHOS);
/* Linux bug and it's cleaner. */
sscanf(argv[i++], "%f", &echo->delay[echo->num_delays]);
sscanf(argv[i++], "%f", &echo->decay[echo->num_delays]);
echo->num_delays++;
}
return (ST_SUCCESS);
}
/*
* Prepare for processing.
*/
static int st_echo_start(eff_t effp)
{
echo_t echo = (echo_t) effp->priv;
int i;
float sum_in_volume;
long j;
echo->maxsamples = 0L;
if ( echo->in_gain < 0.0 )
{
st_fail("echo: gain-in must be positive!");
return (ST_EOF);
}
if ( echo->in_gain > 1.0 )
{
st_fail("echo: gain-in must be less than 1.0!");
return (ST_EOF);
}
if ( echo->out_gain < 0.0 )
{
st_fail("echo: gain-in must be positive!");
return (ST_EOF);
}
for ( i = 0; i < echo->num_delays; i++ ) {
echo->samples[i] = echo->delay[i] * effp->ininfo.rate / 1000.0;
if ( echo->samples[i] < 1 )
{
st_fail("echo: delay must be positive!");
return (ST_EOF);
}
if ( echo->samples[i] > (st_ssize_t)DELAY_BUFSIZ )
{
st_fail("echo: delay must be less than %g seconds!",
DELAY_BUFSIZ / (float) effp->ininfo.rate );
return (ST_EOF);
}
if ( echo->decay[i] < 0.0 )
{
st_fail("echo: decay must be positive!" );
return (ST_EOF);
}
if ( echo->decay[i] > 1.0 )
{
st_fail("echo: decay must be less than 1.0!" );
return (ST_EOF);
}
if ( echo->samples[i] > echo->maxsamples )
echo->maxsamples = echo->samples[i];
}
echo->delay_buf = (double *) xmalloc(sizeof (double) * echo->maxsamples);
for ( j = 0; j < echo->maxsamples; ++j )
echo->delay_buf[j] = 0.0;
/* Be nice and check the hint with warning, if... */
sum_in_volume = 1.0;
for ( i = 0; i < echo->num_delays; i++ )
sum_in_volume += echo->decay[i];
if ( sum_in_volume * echo->in_gain > 1.0 / echo->out_gain )
st_warn("echo: warning >>> gain-out can cause saturation of output <<<");
echo->counter = 0;
echo->fade_out = echo->maxsamples;
return (ST_SUCCESS);
}
/*
* Processed signed long samples from ibuf to obuf.
* Return number of samples processed.
*/
static int st_echo_flow(eff_t effp, const st_sample_t *ibuf, st_sample_t *obuf,
st_size_t *isamp, st_size_t *osamp)
{
echo_t echo = (echo_t) effp->priv;
int len, done;
int j;
double d_in, d_out;
st_sample_t out;
len = ((*isamp > *osamp) ? *osamp : *isamp);
for(done = 0; done < len; done++) {
/* Store delays as 24-bit signed longs */
d_in = (double) *ibuf++ / 256;
/* Compute output first */
d_out = d_in * echo->in_gain;
for ( j = 0; j < echo->num_delays; j++ ) {
d_out += echo->delay_buf[
(echo->counter + echo->maxsamples - echo->samples[j]) % echo->maxsamples]
* echo->decay[j];
}
/* Adjust the output volume and size to 24 bit */
d_out = d_out * echo->out_gain;
out = ST_24BIT_CLIP_COUNT((st_sample_t) d_out, effp->clips);
*obuf++ = out * 256;
/* Store input in delay buffer */
echo->delay_buf[echo->counter] = d_in;
/* Adjust the counter */
echo->counter = ( echo->counter + 1 ) % echo->maxsamples;
}
/* processed all samples */
return (ST_SUCCESS);
}
/*
* Drain out reverb lines.
*/
static int st_echo_drain(eff_t effp, st_sample_t *obuf, st_size_t *osamp)
{
echo_t echo = (echo_t) effp->priv;
double d_in, d_out;
st_sample_t out;
int j;
st_size_t done;
done = 0;
/* drain out delay samples */
while ( ( done < *osamp ) && ( done < echo->fade_out ) ) {
d_in = 0;
d_out = 0;
for ( j = 0; j < echo->num_delays; j++ ) {
d_out += echo->delay_buf[
(echo->counter + echo->maxsamples - echo->samples[j]) % echo->maxsamples]
* echo->decay[j];
}
/* Adjust the output volume and size to 24 bit */
d_out = d_out * echo->out_gain;
out = ST_24BIT_CLIP_COUNT((st_sample_t) d_out, effp->clips);
*obuf++ = out * 256;
/* Store input in delay buffer */
echo->delay_buf[echo->counter] = d_in;
/* Adjust the counters */
echo->counter = ( echo->counter + 1 ) % echo->maxsamples;
done++;
echo->fade_out--;
};
/* samples played, it remains */
*osamp = done;
if (echo->fade_out == 0)
return ST_EOF;
else
return ST_SUCCESS;
}
/*
* Clean up reverb effect.
*/
static int st_echo_stop(eff_t effp)
{
echo_t echo = (echo_t) effp->priv;
free((char *) echo->delay_buf);
echo->delay_buf = (double *) -1; /* guaranteed core dump */
return (ST_SUCCESS);
}
static st_effect_t st_echo_effect = {
"echo",
"Usage: echo gain-in gain-out delay decay [ delay decay ... ]",
0,
st_echo_getopts,
st_echo_start,
st_echo_flow,
st_echo_drain,
st_echo_stop,
st_effect_nothing
};
const st_effect_t *st_echo_effect_fn(void)
{
return &st_echo_effect;
}