ref: 2d3447046d9a464a8a6918189631a35b2f0a74ed
parent: 05180cc1749e52dd0faf65c1a07df4e78089c6f5
author: robs <robs>
date: Sun Jun 15 12:29:19 EDT 2008
moving things around
--- a/src/resample.c
+++ b/src/resample.c
@@ -51,7 +51,6 @@
#define Amask (Na-1)
#define Pmask (Np-1)
-#define MAXNWING (80<<Lc)
/* Description of constants:
*
* Nc - is the number of look-up values available for the lowpass filter
@@ -116,13 +115,7 @@
double *X, *Y; /* I/O buffers */
} priv_t;
-static void LpFilter(double c[],
- long N,
- double frq,
- double Beta,
- long Num);
-
-/* lsx_makeFilter is used by filter.c */
+/* lsx_makeFilter() declared in filter.c */
int lsx_makeFilter(double Imp[],
long Nwing,
double Froll,
@@ -585,141 +578,11 @@
return (Y - Ystart); /* Return the number of output samples */
}
-int lsx_makeFilter(double Imp[], long Nwing, double Froll, double Beta,
- long Num, int Normalize)
-{- double *ImpR;
- long Mwing, i;
-
- if (Nwing > MAXNWING) /* Check for valid parameters */
- return(-1);
- if ((Froll<=0) || (Froll>1))
- return(-2);
-
- /* it does help accuracy a bit to have the window stop at
- * a zero-crossing of the sinc function */
- Mwing = floor((double)Nwing/(Num/Froll))*(Num/Froll) +0.5;
- if (Mwing==0)
- return(-4);
-
- ImpR = lsx_malloc(sizeof(double) * Mwing);
-
- /* Design a Nuttall or Kaiser windowed Sinc low-pass filter */
- LpFilter(ImpR, Mwing, Froll, Beta, Num);
-
- if (Normalize) { /* 'correct' the DC gain of the lowpass filter */- long Dh;
- double DCgain;
- DCgain = 0;
- Dh = Num; /* Filter sampling period for factors>=1 */
- for (i=Dh; i<Mwing; i+=Dh)
- DCgain += ImpR[i];
- DCgain = 2*DCgain + ImpR[0]; /* DC gain of real coefficients */
- sox_debug("DCgain err=%.12f",DCgain-1.0);-
- DCgain = 1.0/DCgain;
- for (i=0; i<Mwing; i++)
- Imp[i] = ImpR[i]*DCgain;
-
- } else {- for (i=0; i<Mwing; i++)
- Imp[i] = ImpR[i];
- }
- free(ImpR);
- for (i=Mwing; i<=Nwing; i++) Imp[i] = 0;
- /* Imp[Mwing] and Imp[-1] needed for quadratic interpolation */
- Imp[-1] = Imp[1];
-
- return(Mwing);
-}
-
-/* LpFilter()
- *
- * reference: "Digital Filters, 2nd edition"
- * R.W. Hamming, pp. 178-179
- *
- * Izero() computes the 0th order modified bessel function of the first kind.
- * (Needed to compute Kaiser window).
- *
- * LpFilter() computes the coeffs of a Kaiser-windowed low pass filter with
- * the following characteristics:
- *
- * c[] = array in which to store computed coeffs
- * frq = roll-off frequency of filter
- * N = Half the window length in number of coeffs
- * Beta = parameter of Kaiser window
- * Num = number of coeffs before 1/frq
- *
- * Beta trades the rejection of the lowpass filter against the transition
- * width from passband to stopband. Larger Beta means a slower
- * transition and greater stopband rejection. See Rabiner and Gold
- * (Theory and Application of DSP) under Kaiser windows for more about
- * Beta. The following table from Rabiner and Gold gives some feel
- * for the effect of Beta:
- *
- * All ripples in dB, width of transition band = D*N where N = window length
- *
- * BETA D PB RIP SB RIP
- * 2.120 1.50 +-0.27 -30
- * 3.384 2.23 0.0864 -40
- * 4.538 2.93 0.0274 -50
- * 5.658 3.62 0.00868 -60
- * 6.764 4.32 0.00275 -70
- * 7.865 5.0 0.000868 -80
- * 8.960 5.7 0.000275 -90
- * 10.056 6.4 0.000087 -100
- */
-
-
-#define IzeroEPSILON 1E-21 /* Max error acceptable in Izero */
-
-static double Izero(double x)
-{- double sum, u, halfx, temp;
- long n;
-
- sum = u = n = 1;
- halfx = x/2.0;
- do {- temp = halfx/(double)n;
- n += 1;
- temp *= temp;
- u *= temp;
- sum += u;
- } while (u >= IzeroEPSILON*sum);
- return(sum);
-}
-
-static void LpFilter(double *c, long N, double frq, double Beta, long Num)
-{- long i;
-
- /* Calculate filter coeffs: */
- c[0] = frq;
- for (i=1; i<N; i++) {- double x = M_PI*(double)i/(double)(Num);
- c[i] = sin(x*frq)/x;
- }
-
- if (Beta>2) { /* Apply Kaiser window to filter coeffs: */- double IBeta = 1.0/Izero(Beta);
- for (i=1; i<N; i++) {- double x = (double)i / (double)(N);
- c[i] *= Izero(Beta*sqrt(1.0-x*x)) * IBeta;
- }
- } else { /* Apply Nuttall window: */- for(i = 0; i < N; i++) {- double x = M_PI*i / N;
- c[i] *= 0.36335819 + 0.4891775*cos(x) + 0.1365995*cos(2*x) + 0.0106411*cos(3*x);
- }
- }
-}
-
const sox_effect_handler_t *sox_resample_effect_fn(void)
{ static sox_effect_handler_t handler = {"resample", "[ -qs | -q | -ql ] [ rolloff [ beta ] ]",
- SOX_EFF_RATE, getopts, start, flow, drain, stop, NULL, sizeof(priv_t)
+ SOX_EFF_RATE | SOX_EFF_DEPRECATED, getopts, start, flow, drain, stop, NULL, sizeof(priv_t)
};
return &handler;
}