ref: f09c4ff40d21f9447f7c26a7f4b7dbdd6aa696a5
dir: /src/dcshift.c/
/*
* dcshift.c
* (c) 2000.04.15 Chris Ausbrooks <weed@bucket.pp.ualr.edu>
*
* based on vol.c which is
* (c) 20/03/2000 Fabien COELHO <fabien@coelho.net> for sox.
*
* DC shift a sound file, with basic linear amplitude formula.
* Beware of saturations! clipping is checked and reported.
* Cannot handle different number of channels.
* Cannot handle rate change.
*/
#include "st_i.h"
#include <math.h> /* exp(), sqrt() */
/* type used for computations.
*/
#ifndef DCSHIFT_FLOAT
#define DCSHIFT_FLOAT float
#define DCSHIFT_FLOAT_SCAN "%f"
#endif
/* constants
*/
#define ZERO ((DCSHIFT_FLOAT)(0.0e0))
#define LOG_10_20 ((DCSHIFT_FLOAT)(0.1151292546497022842009e0))
#define ONE ((DCSHIFT_FLOAT)(1.0e0))
#define TWENTY ((DCSHIFT_FLOAT)(20.0e0))
char *dcshift_usage = "Usage: dcshift shift [ limitergain ]\n"
"The peak limiter has a gain much less than 1.0 (ie 0.05 or 0.02) which is only\n"
"used on peaks to prevent clipping. (default is no limiter)";
#define DCSHIFT_USAGE dcshift_usage
typedef struct {
DCSHIFT_FLOAT dcshift; /* DC shift. */
int uselimiter; /* boolean: are we using the limiter? */
DCSHIFT_FLOAT limiterthreshhold;
DCSHIFT_FLOAT limitergain; /* limiter gain. */
int limited; /* number of limited values to report. */
int totalprocessed;
int clipped; /* number of clipped values to report. */
} * dcs_t;
/*
* Process options: dcshift (float) type (amplitude, power, dB)
*/
int st_dcshift_getopts(eff_t effp, int n, char **argv)
{
dcs_t dcs = (dcs_t) effp->priv;
dcs->dcshift = ONE; /* default is no change */
dcs->uselimiter = 0; /* default is no limiter */
if (n < 1)
{
st_fail(DCSHIFT_USAGE);
return ST_EOF;
}
if (n && (!sscanf(argv[0], DCSHIFT_FLOAT_SCAN, &dcs->dcshift)))
{
st_fail(DCSHIFT_USAGE);
return ST_EOF;
}
if (n>1)
{
if (!sscanf(argv[1], DCSHIFT_FLOAT_SCAN, &dcs->limitergain))
{
st_fail(DCSHIFT_USAGE);
return ST_EOF;
}
dcs->uselimiter = 1; /* ok, we'll use it */
/* The following equation is derived so that there is no
* discontinuity in output amplitudes */
/* and a ST_SAMPLE_MAX input always maps to a ST_SAMPLE_MAX output
* when the limiter is activated. */
/* (NOTE: There **WILL** be a discontinuity in the slope of the
* output amplitudes when using the limiter.) */
dcs->limiterthreshhold = ST_SAMPLE_MAX * (ONE - (fabs(dcs->dcshift) - dcs->limitergain));
}
return ST_SUCCESS;
}
/*
* Start processing
*/
int st_dcshift_start(eff_t effp)
{
dcs_t dcs = (dcs_t) effp->priv;
if (effp->outinfo.channels != effp->ininfo.channels)
{
st_warn("DCSHIFT cannot handle different channels (in=%d, out=%d)"
" use avg or pan", effp->ininfo.channels, effp->outinfo.channels);
}
if (effp->outinfo.rate != effp->ininfo.rate)
{
st_fail("DCSHIFT cannot handle different rates (in=%ld, out=%ld)"
" use resample or rate", effp->ininfo.rate, effp->outinfo.rate);
return ST_EOF;
}
dcs->clipped = 0;
dcs->limited = 0;
dcs->totalprocessed = 0;
return ST_SUCCESS;
}
/* conversion. clipping could be smoother at high ends?
* this could be a function on its own, with clip count and report
* handled by eff_t and caller.
*/
static st_sample_t clip(dcs_t dcs, const DCSHIFT_FLOAT v)
{
if (v > ST_SAMPLE_MAX)
{
dcs->clipped++;
return ST_SAMPLE_MAX;
}
else if (v < -ST_SAMPLE_MAX)
{
dcs->clipped++;
return -ST_SAMPLE_MAX;
}
/* else */
return (st_sample_t) v;
}
#ifndef MIN
#define MIN(s1,s2) ((s1)<(s2)?(s1):(s2))
#endif
/*
* Process data.
*/
int st_dcshift_flow(eff_t effp, st_sample_t *ibuf, st_sample_t *obuf,
st_size_t *isamp, st_size_t *osamp)
{
dcs_t dcs = (dcs_t) effp->priv;
register DCSHIFT_FLOAT dcshift = dcs->dcshift;
register DCSHIFT_FLOAT limitergain = dcs->limitergain;
register DCSHIFT_FLOAT limiterthreshhold = dcs->limiterthreshhold;
register DCSHIFT_FLOAT sample;
register st_size_t len;
len = MIN(*osamp, *isamp);
/* report back dealt with amount. */
*isamp = len; *osamp = len;
if (dcs->uselimiter)
{
dcs->totalprocessed += len;
for (;len>0; len--)
{
sample = *ibuf++;
if (sample > limiterthreshhold && dcshift > 0)
{
sample = (sample - limiterthreshhold) * limitergain / (ST_SAMPLE_MAX - limiterthreshhold) + limiterthreshhold + dcshift;
dcs->limited++;
}
else if (sample < -limiterthreshhold && dcshift < 0)
{
sample = (sample + limiterthreshhold) * limitergain / (ST_SAMPLE_MAX - limiterthreshhold) - limiterthreshhold + dcshift;
dcs->limited++;
}
else
{
sample = dcshift * ST_SAMPLE_MAX + sample;
}
*obuf++ = clip(dcs, sample);
}
}
else
{
/* quite basic, with clipping */
for (;len>0; len--)
*obuf++ = clip(dcs, dcshift * ST_SAMPLE_MAX + *ibuf++);
}
return ST_SUCCESS;
}
/*
* Do anything required when you stop reading samples.
* Don't close input file!
*/
int st_dcshift_stop(eff_t effp)
{
dcs_t dcs = (dcs_t) effp->priv;
if (dcs->limited)
{
st_warn("DCSHIFT limited %d values (%d percent).",
dcs->limited, (int) (dcs->limited * 100.0 / dcs->totalprocessed));
}
if (dcs->clipped)
{
if (dcs->dcshift > 0)
{
st_warn("DCSHIFT clipped %d values, dcshift=%f too high...",
dcs->clipped, dcs->dcshift);
}
else
{
st_warn("DCSHIFT clipped %d values, dcshift=%f too low...",
dcs->clipped, dcs->dcshift);
}
}
return ST_SUCCESS;
}