ref: 9228e6c128882dcb8bbd5a855eb7fb8a1a22d2a3
dir: /src/pitch.c/
/*
* (c) Fabien Coelho <fabien@coelho.net> 03/2000 for sox. see sox copyright.
*
* pitch shifting.
*
* I found a code on the Computer Music Journal web site
* <http://mitpress.mit.edu/e-journals/Computer_Music_Journal/>
* for pitch shifting the AD 1848 PC soundcards, with
* a lot of (unclear) pointer and integer arithmetics, and
* combine effects (feedback, delay, mixing).
*
* I tried to understand the code, dropped the other effects,
* translated the stuff in float so it's easier to understand,
* drop one of the lookup tables (I know that sin(pi/2-x) = cos(x)),
* and added interpolation and fade options of my own.
* cross fading is always symetric.
*
* Basically, the algorithm performs a resampling at the desire rate
* to achieve the shift (interpolation function) on small overlapping windows,
* and successive windows are faded in/out one into the other to
* rebuild the final signal.
*
* I'm quite disappointed. At first thought, I looked for an FT-based
* algorithm, something like "switch the signal to frequencies, shift
* frequencies, and come back to time", but it does not seem to work
* that way... at least not so easily. Or maybe my attempt was buggy.
*
* Here is the result. It can certainly be improved.
* The result buzzes some time.
* Lot of options available so than one can adjust the result.
*
* so as to lower the pitch, a larger window sounds better (30ms)?
* so as to upper the pitch, a smaller window... (10ms)?
*
* Some speed-optimization could be added at code size expanse/expense?
*/
#include "sox_i.h"
#include <stdlib.h>
#include <string.h>
#include <math.h> /* cos(), pow() */
/* cross fading options for transitions
*/
#define PITCH_FADE_COS 0 /* cosine */
#define PITCH_FADE_HAM 1 /* Hamming */
#define PITCH_FADE_LIN 2 /* linear */
#define PITCH_FADE_TRA 3 /* trapezoid */
#define PITCH_FADE_DEFAULT PITCH_FADE_COS
/* interpolation options
*/
#define PITCH_INTERPOLE_CUB 0 /* cubic */
#define PITCH_INTERPOLE_LIN 1 /* linear */
#define PITCH_INTERPOLE_DEFAULT PITCH_INTERPOLE_CUB
/* default window width
*/
#define PITCH_DEFAULT_WIDTH ((double)(20.0e0)) /* 20 ms */
/* linear factors for the Hamming window
0<=i<=n: HAM_n(i) = HAM0 + HAM1*cos(i*PI/n)
*/
#define HAM1 ((double)(0.46e0))
#define HAM0 ((double)(0.54e0))
/* state of buffer management... */
typedef enum { pi_input, pi_compute, pi_output } pitch_state_t;
/* structure hold by the effect descriptor. */
typedef struct
{
/* OPTIONS
*/
double shift; /* shift in cents, >0 to treble, <0 to bass */
double width; /* sweep size in ms */
int interopt; /* interpole option */
int fadeopt; /* fade option */
double coef; /* coefficient used by trapezoid */
/* what about coef1/coef2 for hamming... */
/* COMPUTATION
*/
double rate; /* sweep rate, around 1.0 */
unsigned int step; /* size of half a sweep, rounded to integer... */
double * fade; /* fading factors table lookup, ~ 1.0 -> ~ 0.0 */
int overlap; /* needed overlap */
double * tmp; /* temporary buffer */
double * acc; /* accumulation buffer */
unsigned int iacc; /* part of acc already output */
sox_size_t size; /* size of buffer for processing chunks. */
unsigned int index; /* index of next empty input item. */
sox_ssample_t *buf; /* bufferize input */
pitch_state_t state; /* buffer management status. */
} * pitch_t;
/* // debug functions
static char * fadeoptname(int opt)
{
switch (opt)
{
case PITCH_FADE_COS: return "cosine";
case PITCH_FADE_HAM: return "hamming";
case PITCH_FADE_LIN: return "linear";
case PITCH_FADE_TRA: return "trapezoid";
default: return "UNEXPECTED";
}
}
static void debug(pitch_t pitch, char * where)
{
sox_debug("%s: ind=%d sz=%ld step=%d o=%d rate=%f ia=%d st=%d fo=%s",
where, pitch->index, pitch->size, pitch->step, pitch->overlap,
pitch->rate, pitch->iacc, pitch->state, fadeoptname(pitch->fadeopt));
}
*/
/* compute f(x) as a linear interpolation...
*/
static double lin(
double f0, /* f(0) */
double f1, /* f(1) */
double x) /* 0.0 <= x < 1.0 */
{
return f0 * (1.0 - x) + f1 * x;
}
/* compute f(x) as a cubic function...
*/
static double cub(
double fm1, /* f(-1) */
double f0, /* f(0) */
double f1, /* f(1) */
double f2, /* f(2) */
double x) /* 0.0 <= x < 1.0 */
{
/* a x^3 + b x^2 + c x + d */
register double a, b, c, d;
d = f0;
b = 0.5 * (f1+fm1) - f0;
a = (1.0/6.0) * (f2-f1+fm1-f0-4.0*b);
c = f1 - a - b - d;
return ((a * x + b) * x + c) * x + d;
}
/* interpolate a quarter (half a window)
*
* ibuf buffer of ilen length is swept at rate speed.
* result put in output buffer obuf of size olen.
*/
static void interpolation(
pitch_t pitch,
const sox_ssample_t *ibuf, sox_size_t ilen,
double * out, sox_size_t olen,
double rate) /* signed */
{
register int i, size;
register double index;
size = pitch->step; /* size == olen? */
if (rate>0) /* sweep forwards */
{
for (index=0.0, i=0; i<(int)olen; i++, index+=rate)
{
register int ifl = (int) index; /* FLOOR */
register double frac = index - ifl;
if (pitch->interopt==PITCH_INTERPOLE_LIN)
out[i] = lin((double) ibuf[ifl],
(double) ibuf[ifl+1],
frac);
else
out[i] = cub((double) ibuf[ifl-1],
(double) ibuf[ifl],
(double) ibuf[ifl+1],
(double) ibuf[ifl+2],
frac);
}
}
else /* rate < 0, sweep backwards */
{
for (index=ilen-1, i=olen-1; i>=0; i--, index+=rate)
{
register int ifl = (int) index; /* FLOOR */
register double frac = index - ifl;
if (pitch->interopt==PITCH_INTERPOLE_LIN)
out[i] = lin((double) ibuf[ifl],
(double) ibuf[ifl+1],
frac);
else
out[i] = cub((double) ibuf[ifl-1],
(double) ibuf[ifl],
(double) ibuf[ifl+1],
(double) ibuf[ifl+2],
frac);
}
}
}
/* from input buffer to acc
*/
static void process_intput_buffer(pitch_t pitch)
{
register int i, len = pitch->step;
/* forwards sweep */
interpolation(pitch,
pitch->buf+pitch->overlap, pitch->step+pitch->overlap,
pitch->tmp, pitch->step,
pitch->rate);
for (i=0; i<len; i++)
pitch->acc[i] = pitch->fade[i]*pitch->tmp[i];
/* backwards sweep */
interpolation(pitch,
pitch->buf, pitch->step+pitch->overlap,
pitch->tmp, pitch->step,
-pitch->rate);
for (i=0; i<len; i++)
pitch->acc[i] += pitch->fade[pitch->step-i-1]*pitch->tmp[i];
}
/*
* Process options
*/
static int sox_pitch_getopts(sox_effect_t * effp, int n, char **argv)
{
pitch_t pitch = (pitch_t) effp->priv;
/* get pitch shift */
pitch->shift = 0.0; /* default is no change */
if (n && !sscanf(argv[0], "%lf", &pitch->shift))
return sox_usage(effp);
/* sweep size in ms */
pitch->width = PITCH_DEFAULT_WIDTH;
if (n>1 && !sscanf(argv[1], "%lf", &pitch->width))
return sox_usage(effp);
/* interpole option */
pitch->interopt = PITCH_INTERPOLE_DEFAULT;
if (n>2)
{
switch(argv[2][0])
{
case 'l':
case 'L':
pitch->interopt = PITCH_INTERPOLE_LIN;
break;
case 'c':
case 'C':
pitch->interopt = PITCH_INTERPOLE_CUB;
break;
default:
return sox_usage(effp);
}
}
/* fade option */
pitch->fadeopt = PITCH_FADE_DEFAULT; /* default */
if (n>3)
{
switch (argv[3][0]) /* what a parser;-) */
{
case 'l':
case 'L':
pitch->fadeopt = PITCH_FADE_LIN;
break;
case 't':
case 'T':
pitch->fadeopt = PITCH_FADE_TRA;
break;
case 'h':
case 'H':
pitch->fadeopt = PITCH_FADE_HAM;
break;
case 'c':
case 'C':
pitch->fadeopt = PITCH_FADE_COS;
break;
default:
return sox_usage(effp);
}
}
pitch->coef = 0.25;
if (n>4 && (!sscanf(argv[4], "%lf", &pitch->coef) ||
pitch->coef<0.0 || pitch->coef>0.5))
return sox_usage(effp);
return SOX_SUCCESS;
}
/*
* Start processing
*/
static int sox_pitch_start(sox_effect_t * effp)
{
pitch_t pitch = (pitch_t) effp->priv;
register int sample_rate = effp->outinfo.rate;
unsigned int i;
/* computer inner stuff... */
pitch->state = pi_input;
/* Should I trust pow?
* BTW, the twelfth root of two is 1.0594630943592952645618252,
* if we consider an equal temperament.
*/
pitch->rate = pow(2.0, pitch->shift/1200.0);
/* size is half of the actual target window size, because of symetry.
*/
pitch->step = ((pitch->width*(0.0005))*sample_rate);
/* make size odd? do we care? */
/* if (!(size & 1)) size++; */
/* security for safe cubic interpolation */
if (pitch->rate > 1.0)
pitch->overlap = (int) ((pitch->rate-1.0)*pitch->step) + 2;
else
pitch->overlap = 2;
pitch->size = pitch->step + 2*pitch->overlap;
pitch->fade = (double *) xmalloc(pitch->step*sizeof(double));
pitch->tmp = (double *) xmalloc(pitch->step*sizeof(double));
pitch->acc = (double *) xmalloc(pitch->step*sizeof(double));
pitch->buf = (sox_ssample_t *) xmalloc(pitch->size*sizeof(sox_ssample_t));
pitch->index = pitch->overlap;
/* default initial signal */
for (i=0; i<pitch->size; i++)
pitch->buf[i] = 0;
if (pitch->fadeopt == PITCH_FADE_HAM)
{
/* does it make sense to have such an option? */
register double pi_step = M_PI / (pitch->step-1);
for (i=0; i<pitch->step; i++)
pitch->fade[i] = (double) (HAM0 + HAM1*cos(pi_step*i));
}
else if (pitch->fadeopt == PITCH_FADE_COS)
{
register double pi_2_step = M_PI_2 / (pitch->step-1);
pitch->fade[0] = 1.0; /* cos(0) == 1.0 */
for (i=1; i<pitch->step-1; i++)
pitch->fade[i] = (double) cos(pi_2_step*i);
pitch->fade[pitch->step-1] = 0.0; /* cos(PI/2) == 0.0 */
}
else if (pitch->fadeopt == PITCH_FADE_LIN)
{
register double stepth = 1.0 / (pitch->step-1);
pitch->fade[0] = 1.0;
for (i=1; i<pitch->step-1; i++)
pitch->fade[i] = (pitch->step-i-1) * stepth;
pitch->fade[pitch->step-1] = 0.0;
}
else if (pitch->fadeopt == PITCH_FADE_TRA)
{
/* 0 <= coef <= 0.5 */
register unsigned int plat = (int) (pitch->step*pitch->coef);
register double slope = 1.0 / (pitch->step - 2*plat);
for (i=0; i<plat; i++)
pitch->fade[i] = 1.0;
for (; i<pitch->step-plat; i++)
pitch->fade[i] = slope * (pitch->step-plat-i-1);
for (; i<pitch->step; i++)
pitch->fade[i] = 0.0;
}
else
{
sox_fail("unexpected PITCH_FADE parameter %d", pitch->fadeopt);
return SOX_EOF;
}
if (pitch->shift == 0)
return SOX_EFF_NULL;
return SOX_SUCCESS;
}
/* Processes input.
*/
static int sox_pitch_flow(sox_effect_t * effp, const sox_ssample_t *ibuf, sox_ssample_t *obuf,
sox_size_t *isamp, sox_size_t *osamp)
{
pitch_t pitch = (pitch_t) effp->priv;
int i, size;
sox_size_t len, iindex, oindex;
size = pitch->size;
/* size to process */
len = min(*isamp, *osamp);
iindex = 0;
oindex = 0;
/* warning:
because of the asynchronous nature of buffering,
the output index can reach the buffer limits before full consumption.
I put the input index just in case.
If the code is correct, eithier len or iindex is redundant.
*/
while (len>0 && iindex<*isamp && oindex<*osamp)
{
if (pitch->state == pi_input)
{
register int tocopy = min(pitch->size-pitch->index, len);
memcpy(pitch->buf+pitch->index, ibuf+iindex, tocopy*sizeof(sox_ssample_t));
len -= tocopy;
pitch->index += tocopy;
iindex += tocopy;
if (pitch->index==pitch->size)
pitch->state = pi_compute;
}
if (pitch->state == pi_compute)
{
process_intput_buffer(pitch);
pitch->state = pi_output;
pitch->iacc = 0;
}
if (pitch->state == pi_output)
{
int toout = min(*osamp-oindex, pitch->step-pitch->iacc);
for (i=0; i<toout; i++)
{
float f;
f = pitch->acc[pitch->iacc++];
SOX_SAMPLE_CLIP_COUNT(f, effp->clips);
obuf[oindex++] = f;
}
if (pitch->iacc == pitch->step)
{
pitch->state = pi_input;
/* shift input buffer. memmove? */
for (i=0; i<2*pitch->overlap; i++)
pitch->buf[i] = pitch->buf[i+pitch->step];
pitch->index = 2*pitch->overlap;
}
}
}
/* report consumption. */
*isamp = iindex;
*osamp = oindex;
return SOX_SUCCESS;
}
/* at the end...
*/
static int sox_pitch_drain(sox_effect_t * effp, sox_ssample_t *obuf, sox_size_t *osamp)
{
pitch_t pitch = (pitch_t) effp->priv;
sox_size_t i;
if (pitch->state == pi_input)
{
/* complete input buffer content with 0. */
for (i=pitch->index; i<pitch->size; i++)
pitch->buf[i] = 0;
pitch->state = pi_compute;
}
if (pitch->state == pi_compute)
{
process_intput_buffer(pitch);
pitch->state = pi_output;
pitch->iacc = 0;
}
/* (pitch->state == pi_output) */
for (i=0; i<*osamp && i<pitch->index-pitch->overlap;)
{
float f;
f = pitch->acc[pitch->iacc++];
SOX_SAMPLE_CLIP_COUNT(f, effp->clips);
obuf[i++] = f;
}
/* report... */
*osamp = i;
if ((pitch->index - pitch->overlap) == 0)
return SOX_EOF;
else
return SOX_SUCCESS;
}
/*
* Do anything required when you stop reading samples.
* Don't close input file!
*/
static int sox_pitch_stop(sox_effect_t * effp)
{
pitch_t pitch = (pitch_t) effp->priv;
free(pitch->fade);
free(pitch->tmp);
free(pitch->acc);
free(pitch->buf);
return SOX_SUCCESS;
}
static sox_effect_handler_t sox_pitch_effect = {
"pitch",
"shift width interpole fade\n"
" (in cents, in ms, cub/lin, cos/ham/lin/trap)"
" (defaults: 0 20 c c)",
SOX_EFF_LENGTH,
sox_pitch_getopts,
sox_pitch_start,
sox_pitch_flow,
sox_pitch_drain,
sox_pitch_stop,
NULL
};
const sox_effect_handler_t *sox_pitch_effect_fn(void)
{
return &sox_pitch_effect;
}