ref: 77ec7a16652b4fbb88d3706397d961ee06265b4d
dir: /src/stretch.c/
/* libSoX Basic time stretcher.
* (c) march/april 2000 Fabien COELHO <fabien@coelho.net> for sox.
*
* cross fade samples so as to go slower or faster.
*
* The filter is based on 6 parameters:
* - stretch factor f
* - window size w
* - input step i
* output step o=f*i
* - steady state of window s, ss = s*w
* - type of cross fading
*
* I decided of the default values of these parameters based
* on some small non extensive tests. maybe better defaults
* can be suggested.
*
* It cannot handle different number of channels.
* It cannot handle rate change.
*/
#include "sox_i.h"
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#define DEFAULT_SLOW_SHIFT_RATIO 0.8
#define DEFAULT_FAST_SHIFT_RATIO 1.0
#define DEFAULT_STRETCH_WINDOW 20.0 /* ms */
/* I'm planing to put some common fading stuff outside.
It's also used in pitch.c
*/
typedef enum { sox_linear_fading } sox_fading_t;
#define DEFAULT_FADING sox_linear_fading
typedef enum { input_state, output_state } stretch_status_t;
typedef struct {
/* options
* FIXME: maybe shift could be allowed > 1.0 with factor < 1.0 ???
*/
double factor; /* strech factor. 1.0 means copy. */
double window; /* window in ms */
sox_fading_t fade; /* type of fading */
double shift; /* shift ratio wrt window. <1.0 */
double fading; /* fading ratio wrt window. <0.5 */
/* internal stuff */
stretch_status_t state; /* automaton status */
sox_size_t size; /* buffer size */
sox_size_t index; /* next available element */
sox_sample_t *ibuf; /* input buffer */
sox_size_t ishift; /* input shift */
sox_size_t oindex; /* next evailable element */
double * obuf; /* output buffer */
sox_size_t oshift; /* output shift */
sox_size_t fsize; /* fading size */
double * fbuf; /* fading, 1.0 -> 0.0 */
} priv_t;
/*
* Process options
*/
static int sox_stretch_getopts(sox_effect_t * effp, int n, char **argv)
{
priv_t * stretch = (priv_t *) effp->priv;
/* default options */
stretch->factor = 1.0; /* default is no change */
stretch->window = DEFAULT_STRETCH_WINDOW;
stretch->fade = sox_linear_fading;
if (n > 0 && !sscanf(argv[0], "%lf", &stretch->factor)) {
sox_fail("error while parsing factor");
return lsx_usage(effp);
}
if (n > 1 && !sscanf(argv[1], "%lf", &stretch->window)) {
sox_fail("error while parsing window size");
return lsx_usage(effp);
}
if (n > 2) {
switch (argv[2][0]) {
case 'l':
case 'L':
stretch->fade = sox_linear_fading;
break;
default:
sox_fail("error while parsing fade type");
return lsx_usage(effp);
}
}
/* default shift depends whether we go slower or faster */
stretch->shift = (stretch->factor <= 1.0) ?
DEFAULT_FAST_SHIFT_RATIO: DEFAULT_SLOW_SHIFT_RATIO;
if (n > 3 && !sscanf(argv[3], "%lf", &stretch->shift)) {
sox_fail("error while parsing shift ratio");
return lsx_usage(effp);
}
if (stretch->shift > 1.0 || stretch->shift <= 0.0) {
sox_fail("error with shift ratio value");
return lsx_usage(effp);
}
/* default fading stuff...
it makes sense for factor >= 0.5 */
if (stretch->factor < 1.0)
stretch->fading = 1.0 - (stretch->factor * stretch->shift);
else
stretch->fading = 1.0 - stretch->shift;
if (stretch->fading > 0.5)
stretch->fading = 0.5;
if (n > 4 && !sscanf(argv[4], "%lf", &stretch->fading)) {
sox_fail("error while parsing fading ratio");
return lsx_usage(effp);
}
if (stretch->fading > 0.5 || stretch->fading < 0.0) {
sox_fail("error with fading ratio value");
return lsx_usage(effp);
}
return SOX_SUCCESS;
}
/*
* Start processing
*/
static int sox_stretch_start(sox_effect_t * effp)
{
priv_t * stretch = (priv_t *)effp->priv;
sox_size_t i;
if (stretch->factor == 1)
return SOX_EFF_NULL;
stretch->state = input_state;
stretch->size = (int)(effp->out_signal.rate * 0.001 * stretch->window);
/* start in the middle of an input to avoid initial fading... */
stretch->index = stretch->size / 2;
stretch->ibuf = lsx_malloc(stretch->size * sizeof(sox_sample_t));
/* the shift ratio deal with the longest of ishift/oshift
hence ishift<=size and oshift<=size. */
if (stretch->factor < 1.0) {
stretch->ishift = stretch->shift * stretch->size;
stretch->oshift = stretch->factor * stretch->ishift;
} else {
stretch->oshift = stretch->shift * stretch->size;
stretch->ishift = stretch->oshift / stretch->factor;
}
assert(stretch->ishift <= stretch->size);
assert(stretch->oshift <= stretch->size);
stretch->oindex = stretch->index; /* start as synchronized */
stretch->obuf = lsx_malloc(stretch->size * sizeof(double));
stretch->fsize = (int)(stretch->fading * stretch->size);
stretch->fbuf = lsx_malloc(stretch->fsize * sizeof(double));
/* initialize buffers */
for (i = 0; i<stretch->size; i++)
stretch->ibuf[i] = 0;
for (i = 0; i<stretch->size; i++)
stretch->obuf[i] = 0.0;
if (stretch->fsize>1) {
double slope = 1.0 / (stretch->fsize - 1);
stretch->fbuf[0] = 1.0;
for (i = 1; i < stretch->fsize - 1; i++)
stretch->fbuf[i] = slope * (stretch->fsize - i - 1);
stretch->fbuf[stretch->fsize - 1] = 0.0;
} else if (stretch->fsize == 1)
stretch->fbuf[0] = 1.0;
sox_debug("start: (f=%.2f w=%.2f r=%.2f f=%.2f)"
" st=%d s=%d ii=%d is=%d oi=%d os=%d fs=%d\n",
stretch->factor, stretch->window, stretch->shift, stretch->fading,
stretch->state, stretch->size, stretch->index, stretch->ishift,
stretch->oindex, stretch->oshift, stretch->fsize);
return SOX_SUCCESS;
}
/* accumulates input ibuf to output obuf with fading fbuf */
static void combine(priv_t * stretch)
{
int i, size, fsize;
size = stretch->size;
fsize = stretch->fsize;
/* fade in */
for (i = 0; i < fsize; i++)
stretch->obuf[i] += stretch->fbuf[fsize - i - 1] * stretch->ibuf[i];
/* steady state */
for (; i < size - fsize; i++)
stretch->obuf[i] += stretch->ibuf[i];
/* fade out */
for (; i<size; i++)
stretch->obuf[i] += stretch->fbuf[i - size + fsize] * stretch->ibuf[i];
}
/*
* Processes flow.
*/
static int sox_stretch_flow(sox_effect_t * effp, const sox_sample_t *ibuf, sox_sample_t *obuf,
sox_size_t *isamp, sox_size_t *osamp)
{
priv_t * stretch = (priv_t *) effp->priv;
sox_size_t iindex = 0, oindex = 0;
sox_size_t i;
while (iindex<*isamp && oindex<*osamp) {
if (stretch->state == input_state) {
sox_size_t tocopy = min(*isamp-iindex,
stretch->size-stretch->index);
memcpy(stretch->ibuf + stretch->index, ibuf + iindex, tocopy * sizeof(sox_sample_t));
iindex += tocopy;
stretch->index += tocopy;
if (stretch->index == stretch->size) {
/* compute */
combine(stretch);
/* shift input */
for (i = 0; i + stretch->ishift < stretch->size; i++)
stretch->ibuf[i] = stretch->ibuf[i+stretch->ishift];
stretch->index -= stretch->ishift;
/* switch to output state */
stretch->state = output_state;
}
}
if (stretch->state == output_state) {
while (stretch->oindex < stretch->oshift && oindex < *osamp) {
float f;
f = stretch->obuf[stretch->oindex++];
SOX_SAMPLE_CLIP_COUNT(f, effp->clips);
obuf[oindex++] = f;
}
if (stretch->oindex >= stretch->oshift && oindex<*osamp) {
stretch->oindex -= stretch->oshift;
/* shift internal output buffer */
for (i = 0; i + stretch->oshift < stretch->size; i++)
stretch->obuf[i] = stretch->obuf[i + stretch->oshift];
/* pad with 0 */
for (; i < stretch->size; i++)
stretch->obuf[i] = 0.0;
stretch->state = input_state;
}
}
}
*isamp = iindex;
*osamp = oindex;
return SOX_SUCCESS;
}
/*
* Drain buffer at the end
* maybe not correct ? end might be artificially faded?
*/
static int sox_stretch_drain(sox_effect_t * effp, sox_sample_t *obuf, sox_size_t *osamp)
{
priv_t * stretch = (priv_t *) effp->priv;
sox_size_t i;
sox_size_t oindex = 0;
if (stretch->state == input_state) {
for (i=stretch->index; i<stretch->size; i++)
stretch->ibuf[i] = 0;
combine(stretch);
stretch->state = output_state;
}
while (oindex<*osamp && stretch->oindex<stretch->index) {
float f = stretch->obuf[stretch->oindex++];
SOX_SAMPLE_CLIP_COUNT(f, effp->clips);
obuf[oindex++] = f;
}
*osamp = oindex;
if (stretch->oindex == stretch->index)
return SOX_EOF;
else
return SOX_SUCCESS;
}
/*
* Do anything required when you stop reading samples.
* Don't close input file!
*/
static int sox_stretch_stop(sox_effect_t * effp)
{
priv_t * stretch = (priv_t *) effp->priv;
free(stretch->ibuf);
free(stretch->obuf);
free(stretch->fbuf);
return SOX_SUCCESS;
}
static sox_effect_handler_t sox_stretch_effect = {
"stretch",
"factor [window fade shift fading]\n"
" (expansion, frame in ms, lin/..., unit<1.0, unit<0.5)\n"
" (defaults: 1.0 20 lin ...)",
SOX_EFF_LENGTH | SOX_EFF_DEPRECATED,
sox_stretch_getopts,
sox_stretch_start,
sox_stretch_flow,
sox_stretch_drain,
sox_stretch_stop,
NULL, sizeof(priv_t)
};
const sox_effect_handler_t *sox_stretch_effect_fn(void)
{
return &sox_stretch_effect;
}