File: echo.c

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/*
 * 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 defintions 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 */
#ifdef HAVE_MALLOC_H
#include <malloc.h>
#endif
#include <math.h>
#include "st.h"

#define DELAY_BUFSIZ ( 50L * 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];
	long	samples[MAX_ECHOS], maxsamples, fade_out;
} *echo_t;

/* Private data for SKEL file */


/* If we are not carefull with the output volume */
LONG echo_clip24(l)
LONG l;
{
	if (l >= ((LONG)1 << 24))
		return ((LONG)1 << 24) - 1;
	else if (l <= -((LONG)1 << 24))
		return -((LONG)1 << 24) + 1;
	else
		return l;
}



/*
 * Process options
 */
void echo_getopts(effp, n, argv) 
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))
	    fail("Usage: echo gain-in gain-out delay decay [ delay decay ... ]");

	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 )
			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++;
	}
}

/*
 * Prepare for processing.
 */
void echo_start(effp)
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 )
		fail("echo: gain-in must be positive!\n");
	if ( echo->in_gain > 1.0 )
		fail("echo: gain-in must be less than 1.0!\n");
	if ( echo->out_gain < 0.0 )
		fail("echo: gain-in must be positive!\n");
	for ( i = 0; i < echo->num_delays; i++ ) {
		echo->samples[i] = echo->delay[i] * effp->ininfo.rate / 1000.0;
		if ( echo->samples[i] < 1 )
		    fail("echo: delay must be positive!\n");
		if ( echo->samples[i] > DELAY_BUFSIZ )
			fail("echo: delay must be less than %g seconds!\n",
				DELAY_BUFSIZ / (float) effp->ininfo.rate );
		if ( echo->decay[i] < 0.0 )
		    fail("echo: decay must be positive!\n" );
		if ( echo->decay[i] > 1.0 )
		    fail("echo: decay must be less than 1.0!\n" );
		if ( echo->samples[i] > echo->maxsamples )
			echo->maxsamples = echo->samples[i];
	}
	if (! (echo->delay_buf = (double *) malloc(sizeof (double) * echo->maxsamples)))
		fail("echo: Cannot malloc %d bytes!\n", 
			sizeof(long) * 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 )
		warn("echo: warning >>> gain-out can cause saturation of output <<<");
	echo->counter = 0;
	echo->fade_out = echo->maxsamples;
}

/*
 * Processed signed long samples from ibuf to obuf.
 * Return number of samples processed.
 */

void echo_flow(effp, ibuf, obuf, isamp, osamp)
eff_t effp;
LONG *ibuf, *obuf;
int *isamp, *osamp;
{
	echo_t echo = (echo_t) effp->priv;
	int len, done;
	int j;
	
	double d_in, d_out;
	LONG 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 = echo_clip24((LONG) d_out);
		*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 */
}

/*
 * Drain out reverb lines. 
 */
void echo_drain(effp, obuf, osamp)
eff_t effp;
LONG *obuf;
int *osamp;
{
	echo_t echo = (echo_t) effp->priv;
	double d_in, d_out;
	LONG out;
	int j;
	long 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 = echo_clip24((LONG) d_out);
		*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;
}

/*
 * Clean up reverb effect.
 */
void echo_stop(effp)
eff_t effp;
{
	echo_t echo = (echo_t) effp->priv;

	free((char *) echo->delay_buf);
	echo->delay_buf = (double *) -1;   /* guaranteed core dump */
}