ref: 98cb9132420f6bfc2cc0ebd72f5de21b336ab0f4
dir: /pick.c/
/*
* 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.
*/
/*
* "pick" effect by Lauren Weinstein (lauren@vortex.com); 2/94
* Creates a 1 channel file by selecting a single channel from
* a 2 or 4 channel file. Does not currently allow creating a 2 channel
* file by selecting 2 channels from a 4 channel file.
*/
#include "st.h"
#include "libst.h"
/* Private data for SKEL file */
typedef struct pickstuff {
int chan; /* selected channel */
} *pick_t;
/* channel names are offset by 1 from actual channel byte array offsets */
#define CHAN_1 0
#define CHAN_2 1
#define CHAN_3 2
#define CHAN_4 3
/*
* Process options
*/
void
pick_getopts(effp, n, argv)
eff_t effp;
int n;
char **argv;
{
pick_t pick = (pick_t) effp->priv;
if (n == 1 && argv[0][0] == '-') { /* must specify channel to pick */
switch (argv[0][1]) {
case 'l':
pick->chan = CHAN_1;
return;
case 'r':
pick->chan = CHAN_2;
return;
case '1':
pick->chan = CHAN_1;
return;
case '2':
pick->chan = CHAN_2;
return;
case '3':
pick->chan = CHAN_3;
return;
case '4':
pick->chan = CHAN_4;
return;
}
}
pick->chan = -1; /* invalid option */
}
/*
* Start processing. Final option checking is done here since
* error/usage messages will vary based on the number of input/output
* channels selected, and that info is not available in pick_getopts()
* above.
*/
void
pick_start(effp)
eff_t effp;
{
pick_t pick = (pick_t) effp->priv;
if (effp->outinfo.channels != 1) /* must be one output channel */
fail("Can't pick with other than 1 output channel.");
if (effp->ininfo.channels != 2 && effp->ininfo.channels != 4)
fail("Can't pick with other than 2 or 4 input channels.");
if (effp->ininfo.channels == 2) { /* check for valid option */
if (pick->chan == -1 || pick->chan == CHAN_3 || pick->chan == CHAN_4)
fail("Must specify channel to pick: '-l', '-r', '-1', or '-2'.");
}
else /* must be 4 channels; check for valid option */
if (pick->chan == -1)
fail("Must specify channel to pick: '-1', '-2', '-3', or '-4'.");
}
/*
* Process signed long samples from ibuf to obuf,
* isamp or osamp samples, whichever is smaller,
* while picking appropriate channels.
*/
void pick_flow(effp, ibuf, obuf, isamp, osamp)
eff_t effp;
LONG *ibuf, *obuf;
int *isamp, *osamp;
{
pick_t pick = (pick_t) effp->priv;
int len, done;
switch (effp->ininfo.channels) {
case 2:
len = ((*isamp/2 > *osamp) ? *osamp : *isamp/2);
for(done = 0; done < len; done++) {
*obuf++ = ibuf[pick->chan];
ibuf += 2;
}
*isamp = len * 2;
*osamp = len;
break;
case 4:
len = ((*isamp/4 > *osamp) ? *osamp : *isamp/4);
for(done = 0; done < len; done++) {
*obuf++ = ibuf[pick->chan];
ibuf += 4;
}
*isamp = len * 4;
*osamp = len;
break;
}
}
/*
* Do anything required when you stop reading samples.
* Don't close input file!
*/
void pick_stop(effp)
eff_t effp;
{
/* nothing to do */
}