ref: 60e502a9b5a169a508bf9b8872c6fa371ecf8c1d
dir: /src/speed.c/
/* * (c) Fabien Coelho <fabien@coelho.net> for sox, 03/2000. * * see sox copyright. * * speed up or down the sound, like a tape. * basically it's like resampling without resampling;-) * this could be done just by changing the rate of the file? * I don't know whether any rate is admissible. * implemented with a slow automaton, but it's easier than one more buffer. * I think it is especially inefficient. */ #include "st_i.h" #include <math.h> /* pow */ #include <string.h> /* type used for computations. */ #ifndef SPEED_FLOAT #define SPEED_FLOAT float #define SPEED_FLOAT_SCAN "%f" #endif /* constants */ #define FOUR ((SPEED_FLOAT)(4.0e0)) #define ONE ((SPEED_FLOAT)(1.0e0)) #define HALF ((SPEED_FLOAT)(0.5e0)) #define ONESIXTH ((SPEED_FLOAT)(1.0e0/6.0e0)) #define ZERO ((SPEED_FLOAT)(0.0e0)) #define SPEED_USAGE "speed [-c] factor (default 1.0, <1 slows, -c: factor in cent)" /* automaton status */ typedef enum { sp_input, sp_transfer, sp_compute } buffer_state_t; /* internal structure */ typedef struct { /* options */ SPEED_FLOAT factor; /* speed factor. */ /* internals. */ int clipped; /* number of clipped values to report */ SPEED_FLOAT rate; /* rate of buffer sweep */ int compression; /* integer compression of the signal. */ int index; /* how much of the input buffer is filled */ st_sample_t *ibuf; /* small internal input buffer for compression */ SPEED_FLOAT cbuf[4]; /* computation buffer for interpolation */ SPEED_FLOAT frac; /* current index position in cbuf */ int icbuf; /* available position in cbuf */ buffer_state_t state; /* automaton status */ } * speed_t; /* static void debug(char * where, speed_t s) { fprintf(stderr, "%s: f=%f r=%f comp=%d i=%d ic=%d frac=%f state=%d v=%f\n", where, s->factor, s->rate, s->compression, s->index, s->icbuf, s->frac, s->state, s->cbuf[0]); } */ /* compute f(x) with a cubic interpolation... */ static SPEED_FLOAT cub( SPEED_FLOAT fm1, /* f(-1) */ SPEED_FLOAT f0, /* f(0) */ SPEED_FLOAT f1, /* f(1) */ SPEED_FLOAT f2, /* f(2) */ SPEED_FLOAT x) /* 0.0 <= x < 1.0 */ { /* a x^3 + b x^2 + c x + d */ register SPEED_FLOAT a, b, c, d; d = f0; b = HALF * (f1+fm1) - f0; a = ONESIXTH * (f2-f1+fm1-f0-FOUR*b); c = f1 - a - b - d; return ((a * x + b) * x + c) * x + d; } /* clip if necessary, and report. */ static st_sample_t clip(speed_t speed, SPEED_FLOAT v) { if (v < -ST_SAMPLE_MAX) { speed->clipped++; return -ST_SAMPLE_MAX; } else if (v > ST_SAMPLE_MAX) { speed->clipped++; return ST_SAMPLE_MAX; } else return (st_sample_t) v; } /* get options. */ int st_speed_getopts(eff_t effp, int n, char **argv) { speed_t speed = (speed_t) effp->priv; int cent = 0; speed->factor = ONE; /* default */ if (n>0 && !strcmp(argv[0], "-c")) { cent = 1; argv++; n--; } if (n && (!sscanf(argv[0], SPEED_FLOAT_SCAN, &speed->factor) || (cent==0 && speed->factor<=ZERO))) { printf("n = %d cent = %d speed = %f\n",n,cent,speed->factor); st_fail(SPEED_USAGE); return ST_EOF; } else if (cent != 0) /* CONST==2**(1/1200) */ { speed->factor = pow(1.00057778950655, speed->factor); /* fprintf(stderr, "Speed factor: %f\n", speed->factor);*/ } return ST_SUCCESS; } /* start processing. */ int st_speed_start(eff_t effp) { speed_t speed = (speed_t) effp->priv; speed->clipped = 0; if (speed->factor >= ONE) { speed->compression = (int) speed->factor; /* floor */ speed->rate = speed->factor / speed->compression; } else { speed->compression = 1; speed->rate = speed->factor; } speed->ibuf = (st_sample_t *) malloc(speed->compression* sizeof(st_sample_t)); speed->index = 0; speed->state = sp_input; speed->cbuf[0] = ZERO; /* default previous value for interpolation */ speed->icbuf = 1; speed->frac = ZERO; if (!speed->ibuf) { st_fail("malloc failed"); return ST_EOF; } return ST_SUCCESS; } #ifndef MIN #define MIN(a,b) ((a)<(b)?(a):(b)) #endif /* transfer input buffer to computation buffer. */ static void transfer(speed_t speed) { register int i; register SPEED_FLOAT s = ZERO; for (i=0; i<speed->index; i++) s += (SPEED_FLOAT) speed->ibuf[i]; speed->cbuf[speed->icbuf++] = s / ((SPEED_FLOAT) speed->index); if (speed->icbuf == 4) speed->state = sp_compute; else speed->state = sp_input; speed->index = 0; } /* interpolate values */ static st_size_t compute(speed_t speed, st_sample_t *obuf, st_size_t olen) { st_size_t i; for(i = 0; i<olen && speed->frac < ONE; i++, speed->frac += speed->rate) obuf[i] = clip(speed, cub(speed->cbuf[0], speed->cbuf[1], speed->cbuf[2], speed->cbuf[3], speed->frac)); if (speed->frac >= ONE) { speed->frac -= ONE; speed->cbuf[0] = speed->cbuf[1]; speed->cbuf[1] = speed->cbuf[2]; speed->cbuf[2] = speed->cbuf[3]; speed->icbuf = 3; speed->state = sp_input; } return i; /* number of data out */ } /* handle a flow. */ int st_speed_flow(eff_t effp, st_sample_t *ibuf, st_sample_t *obuf, st_size_t *isamp, st_size_t *osamp) { speed_t speed; register st_size_t len, iindex, oindex; speed = (speed_t) effp->priv; len = MIN(*isamp, *osamp); iindex = 0; oindex = 0; while (iindex<len && oindex<len) { /* store to input buffer. */ if (speed->state==sp_input) { speed->ibuf[speed->index++] = ibuf[iindex++]; if (speed->index==speed->compression) speed->state = sp_transfer; } /* transfer to compute buffer. */ if (speed->state==sp_transfer) transfer(speed); /* compute interpolation. */ if (speed->state==sp_compute) oindex += compute(speed, obuf+oindex, len-oindex); } *isamp = iindex; *osamp = oindex; return ST_SUCCESS; } /* end of stuff. */ int st_speed_drain(eff_t effp, st_sample_t *obuf, st_size_t *osamp) { speed_t speed = (speed_t) effp->priv; st_size_t i, oindex; transfer(speed); /* fix up trail by emptying cbuf */ for (oindex=0, i=0; i<2 && oindex<*osamp;) { if (speed->state==sp_input) { speed->ibuf[speed->index++] = ZERO; i++; if (speed->index==speed->compression) speed->state = sp_transfer; } /* transfer to compute buffer. */ if (speed->state==sp_transfer) transfer(speed); /* compute interpolation. */ if (speed->state==sp_compute) oindex += compute(speed, obuf+oindex, *osamp-oindex); } *osamp = oindex; /* report how much was generated. */ return ST_SUCCESS; } /* stop processing. report overflows. */ int st_speed_stop(eff_t effp) { speed_t speed = (speed_t) effp->priv; if (speed->clipped) st_warn("SPEED: %d values clipped...", speed->clipped); free(speed->ibuf); return ST_SUCCESS; }