ref: c61a5fec6258b484fc7e5fbd2a088eff1c4571be
dir: /src/avg.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.
*
* Channel duplication code by Graeme W. Gill - 93/5/18
*/
/*
* Sound Tools stereo/quad -> mono mixdown effect file.
* and mono/stereo -> stereo/quad channel duplication.
*
* What's in a center channel?
*/
#include "st.h"
/* Private data for SKEL file */
typedef struct avgstuff {
int mix; /* How are we mixing it? */
} *avg_t;
#define MIX_CENTER 0
#define MIX_LEFT 1
#define MIX_RIGHT 2
/*
* Process options
*/
void avg_getopts(effp, n, argv)
eff_t effp;
int n;
char **argv;
{
avg_t avg = (avg_t) effp->priv;
/* NOTE :- should probably have a pan option for both */
/* 2 -> 1 and 1 -> 2 etc. conversion, rather than just */
/* left and right. If 4 channels is to be fully supported, */
/* front and back pan is also needed. (GWG) */
/* (should at least have MIX_FRONT and MIX_BACK) */
avg->mix = MIX_CENTER;
if (n) {
if(!strcmp(argv[0], "-l"))
avg->mix = MIX_LEFT;
else if (!strcmp(argv[0], "-r"))
avg->mix = MIX_RIGHT;
else
fail("Usage: avg [ -l | -r ]");
}
}
/*
* Start processing
*/
void
avg_start(effp)
eff_t effp;
{
switch (effp->outinfo.channels) {
case 1: switch (effp->ininfo.channels) {
case 2:
case 4:
return;
}
case 2: switch (effp->ininfo.channels) {
case 1:
case 4:
return;
}
case 4: switch (effp->ininfo.channels) {
case 1:
case 2:
return;
}
}
fail("Can't average %d channels into %d channels",
effp->ininfo.channels, effp->outinfo.channels);
}
/*
* Process either isamp or osamp samples, whichever is smaller.
*/
void avg_flow(effp, ibuf, obuf, isamp, osamp)
eff_t effp;
LONG *ibuf, *obuf;
int *isamp, *osamp;
{
avg_t avg = (avg_t) effp->priv;
int len, done;
switch (effp->outinfo.channels) {
case 1: switch (effp->ininfo.channels) {
case 2:
/* average 2 channels into 1 */
len = ((*isamp/2 > *osamp) ? *osamp : *isamp/2);
switch(avg->mix) {
case MIX_CENTER:
for(done = 0; done < len; done++) {
*obuf++ = ibuf[0]/2 + ibuf[1]/2;
ibuf += 2;
}
break;
case MIX_LEFT:
for(done = 0; done < len; done++) {
*obuf++ = ibuf[0];
ibuf += 2;
}
break;
case MIX_RIGHT:
for(done = 0; done < len; done++) {
*obuf++ = ibuf[1];
ibuf += 2;
}
break;
}
*isamp = len * 2;
*osamp = len;
break;
case 4:
/* average 4 channels into 1 */
len = ((*isamp/4 > *osamp) ? *osamp : *isamp/4);
switch(avg->mix) {
case MIX_CENTER:
for(done = 0; done < len; done++) {
*obuf++ = ibuf[0]/4 + ibuf[1]/4 +
ibuf[2]/4 + ibuf[3]/4;
ibuf += 4;
}
break;
case MIX_LEFT:
for(done = 0; done < len; done++) {
*obuf++ = ibuf[0]/2 + ibuf[2]/2;
ibuf += 4;
}
break;
case MIX_RIGHT:
for(done = 0; done < len; done++) {
*obuf++ = ibuf[1]/2 + ibuf[3]/2;
ibuf += 4;
}
break;
}
*isamp = len * 4;
*osamp = len;
break;
}
break;
case 2: switch (effp->ininfo.channels) {
case 1:
/* duplicate 1 channel into 2 */
len = ((*isamp > *osamp/2) ? *osamp/2 : *isamp);
switch(avg->mix) {
case MIX_CENTER:
for(done = 0; done < len; done++) {
obuf[0] = obuf[1] = ibuf[0];
ibuf += 1;
obuf += 2;
}
break;
case MIX_LEFT:
for(done = 0; done < len; done++) {
obuf[0] = ibuf[0];
obuf[1] = 0;
ibuf += 1;
obuf += 2;
}
break;
case MIX_RIGHT:
for(done = 0; done < len; done++) {
obuf[0] = 0;
obuf[1] = ibuf[0];
ibuf += 1;
obuf += 2;
}
break;
}
*isamp = len;
*osamp = len * 2;
break;
/*
* After careful inspection of CSOUND source code,
* I'm mildly sure the order is:
* front-left, front-right, rear-left, rear-right
*/
case 4:
/* average 4 channels into 2 */
len = ((*isamp/4 > *osamp/2) ? *osamp/2 : *isamp/4);
for(done = 0; done < len; done++) {
obuf[0] = ibuf[0]/2 + ibuf[2]/2;
obuf[1] = ibuf[1]/2 + ibuf[3]/2;
ibuf += 4;
obuf += 2;
}
*isamp = len * 4;
*osamp = len * 2;
break;
}
break;
case 4: switch (effp->ininfo.channels) {
case 1:
/* duplicate 1 channel into 4 */
len = ((*isamp > *osamp/4) ? *osamp/4 : *isamp);
switch(avg->mix) {
case MIX_CENTER:
for(done = 0; done < len; done++) {
obuf[0] = obuf[1] =
obuf[2] = obuf[3] = ibuf[0];
ibuf += 1;
obuf += 4;
}
break;
case MIX_LEFT:
for(done = 0; done < len; done++) {
obuf[0] = obuf[2] = ibuf[0];
obuf[1] = obuf[3] = 0;
ibuf += 1;
obuf += 4;
}
break;
case MIX_RIGHT:
for(done = 0; done < len; done++) {
obuf[0] = obuf[2] = 0;
obuf[1] = obuf[3] = ibuf[0];
ibuf += 1;
obuf += 4;
}
break;
}
*isamp = len;
*osamp = len * 4;
break;
case 2:
/* duplicate 2 channels into 4 */
len = ((*isamp/2 > *osamp/4) ? *osamp/4 : *isamp/2);
for(done = 0; done < len; done++) {
obuf[0] = obuf[2] = ibuf[0];
obuf[1] = obuf[3] = ibuf[1];
ibuf += 2;
obuf += 4;
}
*isamp = len * 2;
*osamp = len * 4;
break;
}
break;
} /* end switch out channels */
}
/*
* Do anything required when you stop reading samples.
* Don't close input file!
*
* Should have statistics on right, left, and output amplitudes.
*/
void avg_stop(effp)
eff_t effp;
{
/* nothing to do */
}