static int start(sox_effect_t * effp)
{
priv_t * p = (priv_t *)effp->priv;
dft_filter_t * f = p->base.filter_ptr;
if (!f->num_taps) {
double Fn = effp->in_signal.rate * .5;
double * h[2];
int i, n, post_peak, longer;
if (p->Fc0 >= Fn || p->Fc1 >= Fn) {
lsx_fail("filter frequency must be less than sample-rate / 2");
return SOX_EOF;
}
h[0] = lpf(Fn, p->Fc0, p->tbw0, &p->num_taps[0], p->att, &p->beta,p->round);
h[1] = lpf(Fn, p->Fc1, p->tbw1, &p->num_taps[1], p->att, &p->beta,p->round);
if (h[0])
invert(h[0], p->num_taps[0]);
longer = p->num_taps[1] > p->num_taps[0];
n = p->num_taps[longer];
if (h[0] && h[1]) {
for (i = 0; i < p->num_taps[!longer]; ++i)
h[longer][i + (n - p->num_taps[!longer])/2] += h[!longer][i];
if (p->Fc0 < p->Fc1)
invert(h[longer], n);
free(h[!longer]);
}
if (p->phase != 50)
lsx_fir_to_phase(&h[longer], &n, &post_peak, p->phase);
else post_peak = n >> 1;
if (effp->global_info->plot != sox_plot_off) {
char title[100];
sprintf(title, "SoX effect: sinc filter freq=%g-%g",
p->Fc0, p->Fc1? p->Fc1 : Fn);
lsx_plot_fir(h[longer], n, effp->in_signal.rate,
effp->global_info->plot, title, -p->beta * 10 - 25, 5.);
return SOX_EOF;
}
lsx_set_dft_filter(f, h[longer], n, post_peak);
}
static void init_dft_filter(rate_shared_t * p, unsigned which, int num_taps,
sox_sample_t const h[], double Fp, double Fc, double Fn, double att,
int multiplier, double phase, sox_bool allow_aliasing)
{
dft_filter_t * f = &p->half_band[which];
int dft_length, i;
if (f->num_taps)
return;
if (h) { // for half_fir_coefs_low
dft_length = lsx_set_dft_length(num_taps);
f->coefs = lsx_aligned_calloc(dft_length, sizeof(*f->coefs));
for (i = 0; i < num_taps; ++i)
f->coefs[(i + dft_length - num_taps + 1) & (dft_length - 1)]
= h[abs(num_taps / 2 - i)] / dft_length * 2 * multiplier;
f->post_peak = num_taps / 2;
}
else {
double * h2 = lsx_design_lpf(Fp, Fc, Fn, allow_aliasing, att, &num_taps, 0, -1.);
if (phase != 50)
lsx_fir_to_phase(&h2, &num_taps, &f->post_peak, phase);
else f->post_peak = num_taps / 2;
dft_length = lsx_set_dft_length(num_taps);
f->coefs = lsx_aligned_calloc(dft_length, sizeof(*f->coefs));
for (i = 0; i < num_taps; ++i)
f->coefs[(i + dft_length - num_taps + 1) & (dft_length - 1)]
= h2[i] / dft_length * 2 * multiplier;
lsx_free(h2);
}
assert(num_taps & 1);
f->num_taps = num_taps;
f->dft_length = dft_length;
f->tmp_buf = lsx_aligned_malloc(dft_length*sizeof(FFTComplex)/2);
ff_rdft_x(dft_length, 1, f->coefs, f->tmp_buf);
}