ref: d37d609371b1aeba86c071cfff14b66f4fd5438b
dir: /src/pan.c/
/*
* (c) 20/03/2000 Fabien COELHO <fabien@coelho.net> for sox.
*
* Same copyright as SOX. See Sox (and Sun?;-)
*
* Change panorama of sound file with basic linear volume interpolation.
* The human ear is not sensible to phases? What about delay? too short?
*
* Volume is kept constant (?).
* Beware of saturations!
* Operations are carried out on floats.
* Can handle different number of channels.
* Cannot handle rate change.
*
* Initially based on avg effect.
* pan 0.0 basically behaves as avg.
*/
#include "st_i.h"
/* type for computations.
float mantissa is okay for 8 or 16 bits signals.
maybe a little bit short for 24 bits.
switch to double if you're not happy.
*/
#ifndef PAN_FLOAT
#define PAN_FLOAT float /* float or double */
#define PAN_FLOAT_SCAN "%f" /* "%f" or "%lf" */
#endif
/* constants */
#define TWO ((PAN_FLOAT)(2.0e0))
#define ONEHALF ((PAN_FLOAT)(1.5e0))
#define ONE ((PAN_FLOAT)(1.0e0))
#define MONE ((PAN_FLOAT)(-1.0e0))
#define HALF ((PAN_FLOAT)(0.5e0))
#define QUARTER ((PAN_FLOAT)(0.25e0))
#define ZERO ((PAN_FLOAT)(0.0e0))
/* error message */
#define PAN_USAGE "Usage: pan direction (in [-1.0 .. 1.0])"
/* structure to hold pan parameter */
typedef struct {
/* pan option
*/
PAN_FLOAT dir; /* direction, from left (-1.0) to right (1.0) */
/* local data
*/
int clipped; /* number of clipped values */
} * pan_t;
/*
* Process options
*/
int st_pan_getopts(eff_t effp, int n, char **argv)
{
pan_t pan = (pan_t) effp->priv;
pan->dir = ZERO; /* default is no change */
pan->clipped = 0;
if (n && (!sscanf(argv[0], PAN_FLOAT_SCAN, &pan->dir) ||
pan->dir < MONE || pan->dir > ONE))
{
st_fail(PAN_USAGE);
return ST_EOF;
}
return ST_SUCCESS;
}
/*
* Start processing
*/
int st_pan_start(eff_t effp)
{
if (effp->outinfo.channels==1)
st_warn("PAN onto a mono channel...");
if (effp->outinfo.rate != effp->ininfo.rate)
{
st_fail("PAN cannot handle different rates (in=%ld, out=%ld)"
" use resample or rate", effp->ininfo.rate, effp->outinfo.rate);
return ST_EOF;
}
return ST_SUCCESS;
}
/* clip value if necessary. see comments about such a function in vol.c
* Okay, it might be quite slow to have such a function for so small
* a task. Hopefully the function can be inlined by the compiler?
*/
static st_sample_t clip(pan_t pan, PAN_FLOAT value)
{
if (value < -ST_SAMPLE_MAX)
{
pan->clipped++;
return -ST_SAMPLE_MAX;
}
else if (value > ST_SAMPLE_MAX)
{
pan->clipped++;
return ST_SAMPLE_MAX;
} /* else */
return (st_sample_t) value;
}
#ifndef MIN
#define MIN(s1,s2) ((s1)<(s2)?(s1):(s2))
#endif
#define UNEXPECTED_CHANNELS \
st_fail("unexpected number of channels (in=%d, out=%d)", ich, och); \
return ST_EOF
/*
* Process either isamp or osamp samples, whichever is smaller.
*/
int st_pan_flow(eff_t effp, st_sample_t *ibuf, st_sample_t *obuf,
st_size_t *isamp, st_size_t *osamp)
{
pan_t pan = (pan_t) effp->priv;
register st_size_t len;
st_size_t done;
char ich, och;
register PAN_FLOAT left, right, dir, hdir;
dir = pan->dir; /* -1 <= dir <= 1 */
hdir = HALF * dir; /* -0.5 <= hdir <= 0.5 */
left = HALF - hdir; /* 0 <= left <= 1 */
right = HALF + hdir; /* 0 <= right <= 1 */
ich = effp->ininfo.channels;
och = effp->outinfo.channels;
len = MIN(*osamp/och,*isamp/ich);
/* report back how much is processed. */
*isamp = len*ich;
*osamp = len*och;
/* 9 different cases to handle: (1,2,4) X (1,2,4) */
switch (och) {
case 1: /* pan on mono channel... not much sense. just avg. */
switch (ich) {
case 1: /* simple copy */
for (done=0; done<len; done++)
*obuf++ = *ibuf++;
break;
case 2: /* average 2 */
for (done=0; done<len; done++)
*obuf++ = clip(pan, HALF*ibuf[0] + HALF*ibuf[1]),
ibuf += 2;
break;
case 4: /* average 4 */
for (done=0; done<len; done++)
*obuf++ = clip(pan,
QUARTER*ibuf[0] + QUARTER*ibuf[1] +
QUARTER*ibuf[2] + QUARTER*ibuf[3]),
ibuf += 4;
break;
default:
UNEXPECTED_CHANNELS;
break;
} /* end first switch in channel */
break;
case 2:
switch (ich) {
case 1: /* linear */
for (done=0; done<len; done++)
{
obuf[0] = clip(pan, left * ibuf[0]);
obuf[1] = clip(pan, right * ibuf[0]);
obuf += 2;
ibuf++;
}
break;
case 2: /* linear panorama.
* I'm not sure this is the right way to do it.
*/
if (dir <= ZERO) /* to the left */
{
register PAN_FLOAT volume, cll, clr, cr;
volume = ONE - HALF*dir;
cll = volume*(ONEHALF-left);
clr = volume*(left-HALF);
cr = volume*(ONE+dir);
for (done=0; done<len; done++)
{
obuf[0] = clip(pan, cll * ibuf[0] + clr * ibuf[1]);
obuf[1] = clip(pan, cr * ibuf[1]);
obuf += 2;
ibuf += 2;
}
}
else /* to the right */
{
register PAN_FLOAT volume, cl, crl, crr;
volume = ONE + HALF*dir;
cl = volume*(ONE-dir);
crl = volume*(right-HALF);
crr = volume*(ONEHALF-right);
for (done=0; done<len; done++)
{
obuf[0] = clip(pan, cl * ibuf[0]);
obuf[1] = clip(pan, crl * ibuf[0] + crr * ibuf[1]);
obuf += 2;
ibuf += 2;
}
}
break;
case 4:
if (dir <= ZERO) /* to the left */
{
register PAN_FLOAT volume, cll, clr, cr;
volume = ONE - HALF*dir;
cll = volume*(ONEHALF-left);
clr = volume*(left-HALF);
cr = volume*(ONE+dir);
for (done=0; done<len; done++)
{
register PAN_FLOAT ibuf0, ibuf1;
/* build stereo signal */
ibuf0 = HALF*ibuf[0] + HALF*ibuf[2];
ibuf1 = HALF*ibuf[1] + HALF*ibuf[3];
/* pan it */
obuf[0] = clip(pan, cll * ibuf0 + clr * ibuf1);
obuf[1] = clip(pan, cr * ibuf1);
obuf += 2;
ibuf += 4;
}
}
else /* to the right */
{
register PAN_FLOAT volume, cl, crl, crr;
volume = ONE + HALF*dir;
cl = volume*(ONE-dir);
crl = volume*(right-HALF);
crr = volume*(ONEHALF-right);
for (done=0; done<len; done++)
{
register PAN_FLOAT ibuf0, ibuf1;
ibuf0 = HALF*ibuf[0] + HALF*ibuf[2];
ibuf1 = HALF*ibuf[1] + HALF*ibuf[3];
obuf[0] = clip(pan, cl * ibuf0);
obuf[1] = clip(pan, crl * ibuf0 + crr * ibuf1);
obuf += 2;
ibuf += 4;
}
}
break;
default:
UNEXPECTED_CHANNELS;
break;
} /* end second switch in channel */
break;
case 4:
switch (ich) {
case 1: /* linear */
{
register PAN_FLOAT cr, cl;
cl = HALF*left;
cr = HALF*right;
for (done=0; done<len; done++)
{
obuf[0] = clip(pan, cl * ibuf[0]);
obuf[2] = obuf[0];
obuf[1] = clip(pan, cr * ibuf[0]);
ibuf[3] = obuf[1];
obuf += 4;
ibuf++;
}
}
break;
case 2: /* simple linear panorama */
if (dir <= ZERO) /* to the left */
{
register PAN_FLOAT volume, cll, clr, cr;
volume = HALF - QUARTER*dir;
cll = volume * (ONEHALF-left);
clr = volume * (left-HALF);
cr = volume * (ONE+dir);
for (done=0; done<len; done++)
{
obuf[0] = clip(pan, cll * ibuf[0] + clr * ibuf[1]);
obuf[2] = obuf[0];
obuf[1] = clip(pan, cr * ibuf[1]);
ibuf[3] = obuf[1];
obuf += 4;
ibuf += 2;
}
}
else /* to the right */
{
register PAN_FLOAT volume, cl, crl, crr;
volume = HALF + QUARTER*dir;
cl = volume * (ONE-dir);
crl = volume * (right-HALF);
crr = volume * (ONEHALF-right);
for (done=0; done<len; done++)
{
obuf[0] = clip(pan, cl * ibuf[0]);
obuf[2] = obuf[0];
obuf[1] = clip(pan, crl * ibuf[0] + crr * ibuf[1]);
ibuf[3] = obuf[1];
obuf += 4;
ibuf += 2;
}
}
break;
case 4:
/* maybe I could improve the formula to reverse...
also, turn only by quarters.
*/
if (dir <= ZERO) /* to the left */
{
register PAN_FLOAT cown, cright;
cright = -dir;
cown = ONE + dir;
for (done=0; done<len; done++)
{
obuf[0] = clip(pan, cown*ibuf[0] + cright*ibuf[1]);
obuf[1] = clip(pan, cown*ibuf[1] + cright*ibuf[3]);
obuf[2] = clip(pan, cown*ibuf[2] + cright*ibuf[0]);
obuf[3] = clip(pan, cown*ibuf[3] + cright*ibuf[2]);
obuf += 4;
ibuf += 4;
}
}
else /* to the right */
{
register PAN_FLOAT cleft, cown;
cleft = dir;
cown = ONE - dir;
for (done=0; done<len; done++)
{
obuf[0] = clip(pan, cleft*ibuf[2] + cown*ibuf[0]);
obuf[1] = clip(pan, cleft*ibuf[0] + cown*ibuf[1]);
obuf[2] = clip(pan, cleft*ibuf[3] + cown*ibuf[2]);
obuf[3] = clip(pan, cleft*ibuf[1] + cown*ibuf[3]);
obuf += 4;
ibuf += 4;
}
}
break;
default:
UNEXPECTED_CHANNELS;
break;
} /* end third switch in channel */
break;
default:
UNEXPECTED_CHANNELS;
break;
} /* end switch out channel */
return ST_SUCCESS;
}
/*
* Do anything required when you stop reading samples.
* Don't close input file!
*
* Should have statistics on right, left, and output amplitudes.
*/
int st_pan_stop(eff_t effp)
{
pan_t pan = (pan_t) effp->priv;
if (pan->clipped) {
st_warn("PAN clipped %d values, maybe adjust volume?",
pan->clipped);
}
return ST_SUCCESS;
}