ref: 8dfc09d5e2ca3e9dfa06d251ec58fbd1d6b5d6dd
dir: /src/rate.c/
/*
* August 21, 1998
* Copyright 1998 Fabrice Bellard.
*
* [Rewrote completly the code of Lance Norskog And Sundry
* Contributors with a more efficient algorithm.]
*
* 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.
*/
/*
* Sound Tools rate change effect file.
*/
#include "st_i.h"
#ifndef USE_OLD_RATE
#include <math.h>
/*
* Linear Interpolation.
*
* The use of fractional increment allows us to use no buffer. It
* avoid the problems at the end of the buffer we had with the old
* method which stored a possibly big buffer of size
* lcm(in_rate,out_rate).
*
* Limited to 16 bit samples and sampling frequency <= 65535 Hz. If
* the input & output frequencies are equal, a delay of one sample is
* introduced. Limited to processing 32-bit count worth of samples.
*
* 1 << FRAC_BITS evaluating to zero in several places. Changed with
* an (unsigned long) cast to make it safe. MarkMLl 2/1/99
*/
#define FRAC_BITS 16
/* Private data */
typedef struct ratestuff {
unsigned long opos_frac; /* fractional position of the output stream in input stream unit */
unsigned long opos;
unsigned long opos_inc_frac; /* fractional position increment in the output stream */
unsigned long opos_inc;
unsigned long ipos; /* position in the input stream (integer) */
st_sample_t ilast; /* last sample in the input stream */
} *rate_t;
/*
* Process options
*/
int st_rate_getopts(eff_t effp, int n, char **argv)
{
if (n)
{
st_fail("Rate effect takes no options.");
return (ST_EOF);
}
return (ST_SUCCESS);
}
/*
* Prepare processing.
*/
int st_rate_start(eff_t effp)
{
rate_t rate = (rate_t) effp->priv;
unsigned long incr;
if (effp->ininfo.rate == effp->outinfo.rate)
{
st_fail("Input and Output rates must be different to use rate effect");
return(ST_EOF);
}
if (effp->ininfo.rate >= 65535 || effp->outinfo.rate >= 65535)
{
st_fail("rate effect can only handle rates <= 65535");
return (ST_EOF);
}
if (effp->ininfo.size == ST_SIZE_DWORD ||
effp->ininfo.size == ST_SIZE_DDWORD)
{
st_warn("rate effect reduces data to 16 bits");
}
rate->opos_frac=0;
rate->opos=0;
/* increment */
incr=(unsigned long)((double)effp->ininfo.rate / (double)effp->outinfo.rate *
(double) ((unsigned long) 1 << FRAC_BITS));
rate->opos_inc_frac = incr & (((unsigned long) 1 << FRAC_BITS)-1);
rate->opos_inc = incr >> FRAC_BITS;
rate->ipos=0;
rate->ilast = 0;
return (ST_SUCCESS);
}
/*
* Processed signed long samples from ibuf to obuf.
* Return number of samples processed.
*/
int st_rate_flow(eff_t effp, st_sample_t *ibuf, st_sample_t *obuf,
st_size_t *isamp, st_size_t *osamp)
{
rate_t rate = (rate_t) effp->priv;
st_sample_t *istart,*iend;
st_sample_t *ostart,*oend;
st_sample_t ilast,icur,out;
unsigned long tmp;
double t;
ilast=rate->ilast;
istart = ibuf;
iend = ibuf + *isamp;
ostart = obuf;
oend = obuf + *osamp;
while (obuf < oend) {
/* Safety catch to make sure we have input samples. */
if (ibuf >= iend) goto the_end;
/* read as many input samples so that ipos > opos */
while (rate->ipos <= rate->opos) {
ilast = *ibuf++;
rate->ipos++;
/* See if we finished the input buffer yet */
if (ibuf >= iend) goto the_end;
}
icur = *ibuf;
/* interpolate */
t=(double) rate->opos_frac / ((unsigned long) 1 << FRAC_BITS);
out = (double) ilast * (1.0 - t) + (double) icur * t;
/* output sample & increment position */
*obuf++=(st_sample_t) out;
tmp = rate->opos_frac + rate->opos_inc_frac;
rate->opos = rate->opos + rate->opos_inc + (tmp >> FRAC_BITS);
rate->opos_frac = tmp & (((unsigned long) 1 << FRAC_BITS)-1);
}
the_end:
*isamp = ibuf - istart;
*osamp = obuf - ostart;
rate->ilast = ilast;
return (ST_SUCCESS);
}
/*
* Do anything required when you stop reading samples.
* Don't close input file!
*/
int st_rate_stop(eff_t effp)
{
/* nothing to do */
return (ST_SUCCESS);
}
#else /* USE_OLD_RATE */
/*
* 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.
*/
/*
* Sound Tools rate change effect file.
*/
#include <math.h>
/*
* Least Common Multiple Linear Interpolation
*
* Find least common multiple of the two sample rates.
* Construct the signal at the LCM by interpolating successive
* input samples as straight lines. Pull output samples from
* this line at output rate.
*
* Of course, actually calculate only the output samples.
*
* LCM must be 32 bits or less. Two prime number sample rates
* between 32768 and 65535 will yield a 32-bit LCM, so this is
* stretching it.
*/
/*
* Algorithm:
*
* Generate a master sample clock from the LCM of the two rates.
* Interpolate linearly along it. Count up input and output skips.
*
* Input: |inskip | | | | |
*
*
*
* LCM: | | | | | | | | | | |
*
*
*
* Output: | outskip | | |
*
*
*/
/* Private data for Lerp via LCM file */
typedef struct ratestuff {
st_rate_t lcmrate; /* least common multiple of rates */
unsigned long inskip, outskip; /* LCM increments for I & O rates */
unsigned long total;
unsigned long intot, outtot; /* total samples in LCM basis */
st_sample_t lastsamp; /* history */
} *rate_t;
/*
* Process options
*/
int st_rate_getopts(eff_t effp, int n, char **argv)
{
if (n)
{
st_fail(st_rate_effect.usage);
return (ST_EOF);
}
return (ST_SUCCESS);
}
/*
* Prepare processing.
*/
int st_rate_start(eff_t effp)
{
rate_t rate = (rate_t) effp->priv;
rate->lcmrate = st_lcm((st_sample_t)effp->ininfo.rate, (st_sample_t)effp->outinfo.rate);
/* Cursory check for LCM overflow.
* If both rate are below 65k, there should be no problem.
* 16 bits x 16 bits = 32 bits, which we can handle.
*/
rate->inskip = rate->lcmrate / effp->ininfo.rate;
rate->outskip = rate->lcmrate / effp->outinfo.rate;
rate->total = rate->intot = rate->outtot = 0;
rate->lastsamp = 0;
return (ST_SUCCESS);
}
/*
* Processed signed long samples from ibuf to obuf.
* Return number of samples processed.
*/
int st_rate_flow(eff_t effp, st_sample_t *ibuf, st_sample_t *obuf,
st_size_t *isamp, st_size_t *osamp)
{
rate_t rate = (rate_t) effp->priv;
int len, done;
st_sample_t *istart = ibuf;
st_sample_t last;
done = 0;
if (rate->total == 0) {
/* Emit first sample. We know the fence posts meet. */
*obuf = *ibuf++;
rate->lastsamp = *obuf++ / 65536L;
done = 1;
rate->total = 1;
/* advance to second output */
rate->outtot += rate->outskip;
/* advance input range to span next output */
while ((rate->intot + rate->inskip) <= rate->outtot){
last = *ibuf++ / 65536L;
rate->intot += rate->inskip;
}
}
/* start normal flow-through operation */
last = rate->lastsamp;
/* number of output samples the input can feed */
len = (*isamp * rate->inskip) / rate->outskip;
if (len > *osamp)
len = *osamp;
for(; done < len; done++) {
*obuf = last;
*obuf += ((float)((*ibuf / 65536L) - last)* ((float)rate->outtot -
rate->intot))/rate->inskip;
*obuf *= 65536L;
obuf++;
/* advance to next output */
rate->outtot += rate->outskip;
/* advance input range to span next output */
while ((rate->intot + rate->inskip) <= rate->outtot){
last = *ibuf++ / 65536L;
rate->intot += rate->inskip;
if (ibuf - istart == *isamp)
goto out;
}
/* long samples with high LCM's overrun counters! */
if (rate->outtot == rate->intot)
rate->outtot = rate->intot = 0;
}
out:
*isamp = ibuf - istart;
*osamp = len;
rate->lastsamp = last;
return (ST_SUCCESS);
}
/*
* Do anything required when you stop reading samples.
* Don't close input file!
*/
int st_rate_stop(eff_t effp)
{
/* nothing to do */
return (ST_SUCCESS);
}
#endif /* USE_OLD_RATE */
static st_effect_t st_rate_effect = {
"rate",
"Usage: Rate effect takes no options",
ST_EFF_RATE,
st_rate_getopts,
st_rate_start,
st_rate_flow,
st_effect_nothing_drain,
st_effect_nothing
};
const st_effect_t *st_rate_effect_fn(void)
{
return &st_rate_effect;
}