ref: 9404875aa5445a570c2edff8718986becce3ced2
dir: /src/vol.c/
/*
* (c) 20/03/2000 Fabien COELHO <fabien@coelho.net> for sox.
*
* Change volume of 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() */
static st_effect_t st_vol_effect;
#define LOG_10_20 ((double)(0.1151292546497022842009e0))
typedef struct {
double gain; /* amplitude gain. */
int uselimiter; /* boolean: are we using the limiter? */
double limiterthreshhold;
double limitergain; /* limiter gain. */
int limited; /* number of limited values to report. */
int totalprocessed;
} * vol_t;
/*
* Process options: gain (float) type (amplitude, power, dB)
*/
static int st_vol_getopts(eff_t effp, int n, char **argv)
{
vol_t vol = (vol_t) effp->priv;
vol->gain = 1.0; /* default is no change */
vol->uselimiter = 0; /* default is no limiter */
if (n && (!sscanf(argv[0], "%lf", &vol->gain)))
{
st_fail(st_vol_effect.usage);
return ST_EOF;
}
/* adjust gain depending on type (what a great parser;-) */
if (n>1)
{
switch (argv[1][0])
{
case 'd': /* decibels to amplitude */
case 'D':
vol->gain = exp(vol->gain*LOG_10_20);
break;
case 'p':
case 'P': /* power to amplitude, keep phase change */
if (vol->gain > 0.0)
vol->gain = sqrt(vol->gain);
else
vol->gain = -sqrt(-vol->gain);
break;
case 'a': /* amplitude */
case 'A':
default:
break;
}
}
if (n>2)
{
if ((fabs(vol->gain) < 1.0) || !sscanf(argv[2], "%lf", &vol->limitergain) || !((vol->limitergain > 0.0) && (vol->limitergain < 1.0)))
{
st_fail(st_vol_effect.usage);
return ST_EOF;
}
vol->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.) */
vol->limiterthreshhold = ST_SAMPLE_MAX * (1.0 - vol->limitergain) / (fabs(vol->gain) - vol->limitergain);
}
return ST_SUCCESS;
}
/*
* Start processing
*/
static int st_vol_start(eff_t effp)
{
vol_t vol = (vol_t) effp->priv;
if (effp->outinfo.channels != effp->ininfo.channels) {
st_fail("vol cannot handle different channels (in %d, out %d)"
" use avg or pan", effp->ininfo.channels, effp->outinfo.channels);
return ST_EOF;
}
if (effp->outinfo.rate != effp->ininfo.rate) {
st_fail("vol cannot handle different rates (in %ld, out %ld)"
" use resample", effp->ininfo.rate, effp->outinfo.rate);
return ST_EOF;
}
vol->limited = 0;
vol->totalprocessed = 0;
return ST_SUCCESS;
}
/*
* Process data.
*/
static int st_vol_flow(eff_t effp, const st_sample_t *ibuf, st_sample_t *obuf,
st_size_t *isamp, st_size_t *osamp)
{
vol_t vol = (vol_t) effp->priv;
register double gain = vol->gain;
register double limiterthreshhold = vol->limiterthreshhold;
register double sample;
register st_size_t len;
len = min(*osamp, *isamp);
/* report back dealt with amount. */
*isamp = len; *osamp = len;
if (vol->uselimiter)
{
vol->totalprocessed += len;
for (;len>0; len--)
{
sample = *ibuf++;
if (sample > limiterthreshhold)
{
sample = (ST_SAMPLE_MAX - vol->limitergain * (ST_SAMPLE_MAX - sample));
vol->limited++;
}
else if (sample < -limiterthreshhold)
{
sample = -(ST_SAMPLE_MAX - vol->limitergain * (ST_SAMPLE_MAX + sample));
/* FIXME: MIN is (-MAX)-1 so need to make sure we
* don't go over that. Probably could do this
* check inside the above equation but I didn't
* think it thru.
*/
if (sample < ST_SAMPLE_MIN)
sample = ST_SAMPLE_MIN;
vol->limited++;
} else
sample = gain * sample;
ST_SAMPLE_CLIP_COUNT(sample, effp->clips);
*obuf++ = sample;
}
}
else
{
/* quite basic, with clipping */
for (;len>0; len--)
{
sample = gain * *ibuf++;
ST_SAMPLE_CLIP_COUNT(sample, effp->clips);
*obuf++ = sample;
}
}
return ST_SUCCESS;
}
/*
* Do anything required when you stop reading samples.
* Don't close input file!
*/
static int st_vol_stop(eff_t effp)
{
vol_t vol = (vol_t) effp->priv;
if (vol->limited)
{
st_warn("limited %d values (%d percent).",
vol->limited, (int) (vol->limited * 100.0 / vol->totalprocessed));
}
return ST_SUCCESS;
}
static st_effect_t st_vol_effect = {
"vol",
"Usage: vol gain [ type [ limitergain ] ]"
" (default type=amplitude: 1.0 is constant, <0.0 change phase;\n"
" type=power 1.0 is constant; type=dB: 0.0 is constant, +6 doubles ampl.)\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)",
ST_EFF_MCHAN,
st_vol_getopts,
st_vol_start,
st_vol_flow,
st_effect_nothing_drain,
st_vol_stop,
st_effect_nothing
};
const st_effect_t *st_vol_effect_fn(void)
{
return &st_vol_effect;
}