ref: f09c4ff40d21f9447f7c26a7f4b7dbdd6aa696a5
dir: /src/swap.c/
/*
* swap - effect to swap ordering of channels in multi-channel audio.
*
* Written by Chris Bagwell (cbagwell@sprynet.com) - March 16, 1999
*
* Copyright 1999 Chris Bagwell And Sundry Contributors
* This source code is freely redistributable and may be used for
* any purpose. This copyright notice must be maintained.
* Chris Bagwell And Sundry Contributors are not responsible for
* the consequences of using this software.
*/
#include "st_i.h"
/* Private data for SKEL file */
typedef struct swapstuff {
int order[4];
} *swap_t;
/*
* Process options
*
* Don't do initialization now.
* The 'info' fields are not yet filled in.
*/
int st_swap_getopts(eff_t effp, int n, char **argv)
{
swap_t swap = (swap_t) effp->priv;
swap->order[0] = swap->order[1] = swap->order[2] = swap->order[3] = 0;
if (n)
{
if (n != 2 && n != 4)
{
st_fail("Usage: swap [1 2 | 1 2 3 4]");
return (ST_EOF);
}
else if (n == 2)
{
sscanf(argv[0],"%d",&swap->order[0]);
sscanf(argv[1],"%d",&swap->order[1]);
}
else
{
sscanf(argv[0],"%d",&swap->order[0]);
sscanf(argv[1],"%d",&swap->order[1]);
sscanf(argv[2],"%d",&swap->order[2]);
sscanf(argv[3],"%d",&swap->order[3]);
}
/* Some basic error checking */
if (swap->order[0] < 1 || swap->order[0] > 4)
swap->order[0] = 1;
if (swap->order[1] < 1 || swap->order[1] > 4)
swap->order[1] = 1;
/* If 2 and 3 weren't specified, this logic still forces
* it to equal 0 (our default)
*/
if (swap->order[2] < 1 || swap->order[2] > 4)
swap->order[2] = 1;
if (swap->order[3] < 1 || swap->order[3] > 4)
swap->order[3] = 1;
/* Convert to array offsets */
swap->order[0]--;
swap->order[1]--;
swap->order[2]--;
swap->order[3]--;
}
return (ST_SUCCESS);
}
/*
* Prepare processing.
* Do all initializations.
*/
int st_swap_start(eff_t effp)
{
swap_t swap = (swap_t) effp->priv;
if (effp->outinfo.channels == 1)
{
st_fail("Can't swap channels on mono data.");
return (ST_EOF);
}
if (effp->outinfo.channels == 2)
{
if (swap->order[2] || swap->order[3])
{
st_fail("invalid swap channel options used");
}
if (swap->order[0] != 0 && swap->order[0] != 1)
st_fail("invalid swap channel options used");
if (swap->order[1] != 0 && swap->order[1] != 1)
st_fail("invalid swap channel options used");
}
if (effp->outinfo.channels == 4)
{
if (!swap->order[2] && !swap->order[3])
st_fail("invalid swap channel options used");
}
/* If nothing set then default to the following order */
if (!swap->order[0] && !swap->order[1] &&
!swap->order[2] && !swap->order[3])
{
swap->order[0] = 1;
swap->order[1] = 0;
swap->order[2] = 3;
swap->order[3] = 2;
}
return (ST_SUCCESS);
}
/*
* Processed signed long samples from ibuf to obuf.
* Return number of samples processed.
*/
int st_swap_flow(eff_t effp, st_sample_t *ibuf, st_sample_t *obuf,
st_size_t *isamp, st_size_t *osamp)
{
swap_t swap = (swap_t) effp->priv;
int len, done;
switch (effp->outinfo.channels)
{
case 2:
/* Length to process will be buffer length / 2 since we
* work with two samples at a time.
*/
len = ((*isamp > *osamp) ? *osamp : *isamp) / 2;
for(done = 0; done < len; done++)
{
obuf[0] = ibuf[swap->order[0]];
obuf[1] = ibuf[swap->order[1]];
/* Advance buffer by 2 samples */
ibuf += 2;
obuf += 2;
}
*isamp = len * 2;
*osamp = len * 2;
break;
case 4:
/* Length to process will be buffer length / 4 since we
* work with four samples at a time.
*/
len = ((*isamp > *osamp) ? *osamp : *isamp) / 4;
for(done = 0; done < len; done++)
{
obuf[0] = ibuf[swap->order[0]];
obuf[1] = ibuf[swap->order[1]];
obuf[2] = ibuf[swap->order[2]];
obuf[3] = ibuf[swap->order[3]];
/* Advance buffer by 2 samples */
ibuf += 4;
obuf += 4;
}
*isamp = len * 4;
*osamp = len * 4;
break;
}
return (ST_SUCCESS);
}
/*
* Drain out remaining samples if the effect generates any.
*/
int st_swap_drain(eff_t effp, st_sample_t *obuf, st_size_t *osamp)
{
*osamp = 0;
return (ST_SUCCESS);
}
/*
* Do anything required when you stop reading samples.
* (free allocated memory, etc.)
*/
int st_swap_stop(eff_t effp)
{
/* nothing to do */
return (ST_SUCCESS);
}