Category : C Source Code
Archive   : SOX.ZIP
Filename : ECHO.C

 
Output of file : ECHO.C contained in archive : SOX.ZIP

/*
* July 5, 1991
* Copyright 1991 Lance Norskog And Sundry Contributors
* This source code is freely redistributable and may be used for
* any purpose. This copyright notice must be maintained.
* Lance Norskog And Sundry Contributors are not responsible for
* the consequences of using this software.
*/

/*
** Echo effect. based on:
**
** echoplex.c - echo generator
**
** Copyright (C) 1989 by Jef Poskanzer.
**
** Permission to use, copy, modify, and distribute this software and its
** documentation for any purpose and without fee is hereby granted, provided
** that the above copyright notice appear in all copies and that both that
** copyright notice and this permission notice appear in supporting
** documentation. This software is provided "as is" without express or
** implied warranty.
*/

/*
* Sound Tools echo effect file.
*/

#include "st.h"
#include

#define FADE_THRESH 10
#define MYBUFSIZ 256
#define DELAYBUFSIZ ( 50 * MAXRATE )
#define MAXDELAYS 30

struct echoplex {
int counter;
int numdelays;
long *delaybuf;
float delay[MAXDELAYS], atten[MAXDELAYS];
long samples[MAXDELAYS], maxsamples;
long pl, ppl, pppl;
};

/* Private data for SKEL file */
typedef struct echostuff {
struct echoplex *echoplex;
} *echo_t;

#define abs(a) ((a) >= 0 ? (a) : -(a))

long clip24();

double atof();

extern writing;

/*
* Process options
*/
echo_getopts(effp, n, argv)
eff_t effp;
int n;
char **argv;
{
echo_t echo = (echo_t) effp->priv;
struct echoplex *e;
int i;

echo->echoplex = (struct echoplex *) malloc(sizeof(struct echoplex));
e = echo->echoplex;
e->numdelays = 0;
e->maxsamples = 0;

if ((n == 0) || (n & 1))
fail("Usage: echo delay attenuation [ delay attenuation ... ]");

i = 0;
while (i < n) {
e->delay[e->numdelays] = atof( argv[i++] );
e->atten[e->numdelays] = atof( argv[i++] );
e->numdelays++;
}
}

/*
* Prepare for processing.
*/
echo_start(effp)
eff_t effp;
{
echo_t echo = (echo_t) effp->priv;
struct echoplex *e = echo->echoplex;
int i;

for(i = 0; i < e->numdelays; i++) {
e->samples[i] = e->delay[i] * effp->ininfo.rate;
if ( e->samples[i] < 1 )
fail(" delay must positive, aye!");
if ( e->samples[i] > DELAYBUFSIZ )
fail("Echo: delay must be less than %g seconds",
DELAYBUFSIZ / (float) effp->ininfo.rate );
if ( e->atten[i] < 0.0 )
fail("attenuation must positive, aye!\n" );
if ( e->samples[i] > e->maxsamples )
e->maxsamples = e->samples[i];
}
if (! (e->delaybuf = (long *) malloc(sizeof (long) * e->maxsamples)))
fail("Echo: Cannot malloc %d bytes\n",
sizeof(long) * e->maxsamples);
for ( i = 0; i < e->maxsamples; ++i )
e->delaybuf[i] = 0;
e->pppl = e->ppl = e->pl = 0x7fffff; /* fade-outs */
e->counter = 0;
}

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

echo_flow(effp, ibuf, obuf, isamp, osamp)
eff_t effp;
long *ibuf, *obuf;
int *isamp, *osamp;
{
echo_t echo = (echo_t) effp->priv;
struct echoplex *e = echo->echoplex;
int len, done;
int i, j;

long l;

i = e->counter;
len = ((*isamp > *osamp) ? *osamp : *isamp);
for(done = 0; done < len; done++) {
/* Store delays as 24-bit signed longs */
l = *ibuf++ / 256;
for ( j = 0; j < e->numdelays; ++j )
l = l +
e->delaybuf[( i + e->maxsamples - e->samples[j]) % e->maxsamples] * e->atten[j];
l = clip24(l);
e->delaybuf[i] = l;
*obuf++ = l * 256;
i++; /* XXX need a % maxsamples here ? */
i %= e->maxsamples;
}
e->counter = i;
/* processed all samples */
}

/*
* Drain out echo lines.
*/
echo_drain(effp, obuf, osamp)
eff_t effp;
long *obuf;
long *osamp;
{
echo_t echo = (echo_t) effp->priv;
struct echoplex *e = echo->echoplex;
long l;
int i, j, done;

i = e->counter;
done = 0;
/* drain out delay samples */
do {
l = 0;
for ( j = 0; j < e->numdelays; ++j )
l +=
e->delaybuf[(i + e->maxsamples - e->samples[j]) % e->maxsamples] * e->atten[j];
l = clip24(l);
e->delaybuf[i] = l;
obuf[done++] = l * 256;
e->pppl = e->ppl;
e->ppl = e->pl;
e->pl = l;
i++; /* need a % maxsamples here ? */
i %= e->maxsamples;
} while((done < *osamp) &&
((abs(e->pl) + abs(e->ppl) + abs(e->pppl)) > FADE_THRESH));
e->counter = i;
*osamp = done;
/* drain will not be called again */
}

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

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

long
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;
}




  3 Responses to “Category : C Source Code
Archive   : SOX.ZIP
Filename : ECHO.C

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