ref: 226e1dba5c5f44b4004ffe9c438c9c24af369a01
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.
* Pretty redundant with -v general option.
* 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 VOL_FLOAT
#define VOL_FLOAT float
#define VOL_FLOAT_SCAN "%f"
#endif
/* constants
*/
#define ZERO ((VOL_FLOAT)(0.0e0))
#define LOG_10_20 ((VOL_FLOAT)(0.1151292546497022842009e0))
#define ONE ((VOL_FLOAT)(1.0e0))
#define TWENTY ((VOL_FLOAT)(20.0e0))
#define VOL_USAGE \
"Usage: vol gain [ type [ limitergain ] ]" \
" (default type=amplitude: 1.0 is constant, <0.0 change phase;" \
" type=power 1.0 is constant; type=dB: 0.0 is constant, +6 doubles ampl.)" \
" The peak limiter has a gain much less than 1.0 (ie 0.05 or 0.02) which is only" \
" used on peaks to prevent clipping. (default is no limiter)"
typedef struct {
VOL_FLOAT gain; /* amplitude gain. */
int uselimiter; /* boolean: are we using the limiter? */
VOL_FLOAT limiterthreshhold;
VOL_FLOAT limitergain; /* limiter gain. */
int limited; /* number of limited values to report. */
int totalprocessed;
int clipped; /* number of clipped values to report. */
} * vol_t;
/*
* Process options: gain (float) type (amplitude, power, dB)
*/
int st_vol_getopts(eff_t effp, int n, char **argv)
{
vol_t vol = (vol_t) effp->priv;
vol->gain = ONE; /* default is no change */
vol->uselimiter = 0; /* default is no limiter */
if (n && (!sscanf(argv[0], VOL_FLOAT_SCAN, &vol->gain)))
{
st_fail(VOL_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 > ZERO)
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) < ONE) || !sscanf(argv[2], VOL_FLOAT_SCAN, &vol->limitergain) || !((vol->limitergain > ZERO) && (vol->limitergain < ONE)))
{
st_fail(VOL_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 * (ONE - vol->limitergain) / (fabs(vol->gain) - vol->limitergain);
}
return ST_SUCCESS;
}
/*
* Start processing
*/
int st_vol_start(eff_t effp)
{
vol_t vol = (vol_t) effp->priv;
if (effp->outinfo.channels != effp->ininfo.channels)
{
st_warn("VOL 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("VOL cannot handle different rates (in=%ld, out=%ld)"
" use resample or rate", effp->ininfo.rate, effp->outinfo.rate);
return ST_EOF;
}
vol->clipped = 0;
vol->limited = 0;
vol->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(vol_t vol, const VOL_FLOAT v)
{
if (v > ST_SAMPLE_MAX)
{
vol->clipped++;
return ST_SAMPLE_MAX;
}
else if (v < -ST_SAMPLE_MAX)
{
vol->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_vol_flow(eff_t effp, st_sample_t *ibuf, st_sample_t *obuf,
st_size_t *isamp, st_size_t *osamp)
{
vol_t vol = (vol_t) effp->priv;
register VOL_FLOAT gain = vol->gain;
register VOL_FLOAT limiterthreshhold = vol->limiterthreshhold;
register VOL_FLOAT 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));
vol->limited++;
}
else
{
sample = gain * sample;
}
*obuf++ = clip(vol, sample);
}
}
else
{
/* quite basic, with clipping */
for (;len>0; len--)
*obuf++ = clip(vol, gain * *ibuf++);
}
return ST_SUCCESS;
}
/*
* Do anything required when you stop reading samples.
* Don't close input file!
*/
int st_vol_stop(eff_t effp)
{
vol_t vol = (vol_t) effp->priv;
if (vol->limited)
{
st_warn("VOL limited %d values (%d percent).",
vol->limited, (int) (vol->limited * 100.0 / vol->totalprocessed));
}
if (vol->clipped)
{
st_warn("VOL clipped %d values, amplitude gain=%f too high...",
vol->clipped, vol->gain);
}
return ST_SUCCESS;
}