ref: 76caa137725af8725d869657b9c91f7a1523ea0e
dir: /src/compand.c/
/*
* Compander effect
*
* Written by Nick Bailey (nick@polonius.demon.co.uk or
* N.J.Bailey@leeds.ac.uk). Hope page for this effect:
* http://www.ee.keeds.ac.uk/homes/NJB/Softwere/Compand/compand.html
*
* Copyright 1999 Chris Bagwell And Nick Bailey
* This source code is freely redistributable and may be used for
* any purpose. This copyright notice must be maintained.
* Chris Bagwell And Nick Bailey are not responsible for
* the consequences of using this software.
*/
#include <string.h>
#include <stdlib.h>
#include <math.h>
#include "st.h"
/* Private data for SKEL file */
typedef struct {
int expectedChannels; /* Also flags that channels aren't to be treated
individually when = 1 and input not mono */
int transferPoints; /* Number of points specified on the transfer
function */
double *attackRate; /* An array of attack rates */
double *decayRate; /* ... and of decay rates */
double *transferIns; /* ... and points on the transfer function */
double *transferOuts;
double *volume; /* Current "volume" of each channel */
LONG *lastSamp; /* Remeber the value of the previous sample */
double outgain; /* Post processor gain */
} *compand_t;
/*
* Process options
*
* Don't do initialization now.
* The 'info' fields are not yet filled in.
*/
void compand_getopts(effp, n, argv)
eff_t effp;
int n;
char **argv;
{
compand_t l = (compand_t) effp->priv;
if (n < 2 || n > 4)
fail("Wrong number of arguments for the compander effect\n"
"Use: {<attack_time>,<decay_time>}+ {<dB_in>,<db_out>}+ "
"[<dB_postamp>]\n"
"where {}+ means `one or more in a comma-separated, "
"white-space-free list'\n"
"and [] indications possible omission. dB values are floating\n"
"point or `-inf'; times are in seconds.");
else { /* Right no. of args, but are they well formed? */
char *s;
int rates, tfers, i, commas;
/* Start by checking the attack and decay rates */
for (s = argv[0], commas = 0; *s; ++s)
if (*s == ',') ++commas;
if (commas % 2 == 0) /* There must be an even number of
attack/decay parameters */
fail("compander: Odd number of attack & decay rate parameters");
rates = 1 + commas/2;
if ((l->attackRate = malloc(sizeof(double) * rates)) == NULL ||
(l->decayRate = malloc(sizeof(double) * rates)) == NULL ||
(l->volume = malloc(sizeof(double) * rates)) == NULL ||
(l->lastSamp = calloc(rates, sizeof(LONG))) == NULL)
fail("Out of memory");
l->expectedChannels = rates;
/* Now tokenise the rates string and set up these arrays. Keep
them in seconds at the moment: we don't know the sample rate yet. */
s = strtok(argv[0], ","); i = 0;
do {
l->attackRate[i] = atof(s); s = strtok(NULL, ",");
l->decayRate[i] = atof(s); s = strtok(NULL, ",");
++i;
} while (s != NULL);
/* Same business, but this time for the transfer function */
for (s = argv[1], commas = 0; *s; ++s)
if (*s == ',') ++commas;
if (commas % 2 == 0) /* There must be an even number of
transfer parameters */
fail("compander: Odd number of transfer function parameters\n"
"Each input value in dB must have a corresponding output value");
tfers = 3 + commas/2; /* 0, 0 at start; 1, 1 at end */
if ((l->transferIns = malloc(sizeof(double) * tfers)) == NULL ||
(l->transferOuts = malloc(sizeof(double) * tfers)) == NULL)
fail("Out of memory");
l->transferPoints = tfers;
l->transferIns[0] = 0.0; l->transferOuts[0] = 0.0;
l->transferIns[tfers-1] = 1.0; l->transferOuts[tfers-1] = 1.0;
s = strtok(argv[1], ","); i = 1;
do {
if (!strcmp(s, "-inf"))
fail("Input signals of zero level must always generate zero output");
l->transferIns[i] = pow(10.0, atof(s)/20.0);
if (l->transferIns[i] > 1.0)
fail("dB values are relative to maximum input, and, ipso facto, "
"cannot exceed 0");
if (l->transferIns[i] == 1.0) /* Final point was explicit */
--(l->transferPoints);
if (i > 0 && l->transferIns[i] <= l->transferIns[i-1])
fail("Transfer function points don't have strictly ascending "
"input amplitude");
s = strtok(NULL, ",");
l->transferOuts[i] = strcmp(s, "-inf") ?
pow(10.0, atof(s)/20.0) : 0;
s = strtok(NULL, ",");
++i;
} while (s != NULL);
/* If there is a postprocessor gain, store it */
if (n >= 3) l->outgain = pow(10.0, atof(argv[2])/20.0);
else l->outgain = 1.0;
/* Set the initial "volume" to be attibuted to the input channels.
Unless specified, choose 1.0 (maximum) otherwise clipping will
result if the user has seleced a long attack time */
for (i = 0; i < l->expectedChannels; ++i) {
double v = n>=4 ? pow(10.0, atof(argv[3])/20) : 1.0;
l->volume[i] = v;
}
}
}
/*
* Prepare processing.
* Do all initializations.
*/
void compand_start(effp)
eff_t effp;
{
compand_t l = (compand_t) effp->priv;
int i;
# ifdef DEBUG
{
printf("Starting compand effect\n");
printf("\nRate %ld, size %d, style %d, output gain %g.\n",
effp->outinfo.rate, effp->outinfo.size, effp->outinfo.style,
l->outgain);
printf("%d input channel(s) expected: actually %d\n",
l->expectedChannels, effp->outinfo.channels);
printf("\nAttack and decay rates\n"
"======================\n");
for (i = 0; i < l->expectedChannels; ++i)
printf("Channel %d: attack = %-12g decay = %-12g\n",
i, l->attackRate[i], l->decayRate[i]);
printf("\nTransfer function (linear values)\n"
"================= =============\n");
for (i = 0; i < l->transferPoints; ++i)
printf("%12g -> %-12g\n",
l->transferIns[i], l->transferOuts[i]);
}
# endif
/* Convert attack and decay rates using number of samples */
for (i = 0; i < l->expectedChannels; ++i) {
if (l->attackRate[i] > 1.0/effp->outinfo.rate)
l->attackRate[i] = 1.0 -
exp(-1.0/(effp->outinfo.rate * l->attackRate[i]));
else
l->attackRate[i] = 1.0;
if (l->decayRate[i] > 1.0/effp->outinfo.rate)
l->decayRate[i] = 1.0 -
exp(-1.0/(effp->outinfo.rate * l->decayRate[i]));
else
l->decayRate[i] = 1.0;
}
}
/*
* Update a volume value using the given sample
* value, the attack rate and decay rate
*/
static void doVolume(double *v, double samp, compand_t l, int chan)
{
double s = samp/(~((LONG)1<<31));
double delta = s - *v;
if (delta > 0.0) /* increase volume according to attack rate */
*v += delta * l->attackRate[chan];
else /* reduce volume according to decay rate */
*v += delta * l->decayRate[chan];
}
/*
* Processed signed long samples from ibuf to obuf.
* Return number of samples processed.
*/
void compand_flow(effp, ibuf, obuf, isamp, osamp)
eff_t effp;
LONG *ibuf, *obuf;
int *isamp, *osamp;
{
compand_t l = (compand_t) effp->priv;
int len = (*isamp > *osamp) ? *osamp : *isamp;
int filechans = effp->outinfo.channels;
int done;
for (done = 0; done < len;
done += filechans, obuf += filechans, ibuf += filechans) {
int chan;
/* Maintain the volume fields by simulating a leaky pump circuit */
for (chan = 0; chan < filechans; ++chan) {
if (l->expectedChannels == 1 && filechans > 1) {
/* User is expecting same compander for all channels */
int i;
double maxsamp = 0.0;
for (i = 0; i < filechans; ++i) {
double rect = fabs(ibuf[i]);
if (rect > maxsamp) maxsamp = rect;
}
doVolume(&l->volume[0], maxsamp, l, 0);
break;
} else
doVolume(&l->volume[chan], fabs(ibuf[chan]), l, chan);
}
/* Volume memory is updated: perform compand */
for (chan = 0; chan < filechans; ++chan) {
double v = l->expectedChannels > 1 ?
l->volume[chan] : l->volume[0];
double outv;
int piece;
for (piece = 1 /* yes, 1 */;
piece < l->transferPoints;
++piece)
if (v >= l->transferIns[piece - 1] &&
v < l->transferIns[piece])
break;
outv = l->transferOuts[piece-1] +
(l->transferOuts[piece] - l->transferOuts[piece-1]) *
(v - l->transferIns[piece-1]) /
(l->transferIns[piece] - l->transferIns[piece-1]);
obuf[chan] = ibuf[chan]*(outv/v)*l->outgain;
}
}
*isamp = len; *osamp = len;
}