Fixed performance issue with IIR filter

Passing samples with zero value (0.0) causes very slow processing of
IIR filter on my test machine 'nuedel'. I don't know why.
To solve this, I add a very small number to each input sample.
pull/1/head
Andreas Eversberg 3 years ago
parent f86adf4bb5
commit 31fca59294
  1. 8
      src/libfilter/iir_filter.c
  2. 5
      src/libfm/fm.c

@ -104,7 +104,7 @@ void iir_notch_init(iir_filter_t *filter, double frequency, int samplerate, int
filter->b1 = filter->a1;
filter->b2 = (1 - K / Q + K * K) * norm;
}
void iir_process(iir_filter_t *filter, sample_t *samples, int length)
{
double a0, a1, a2, b1, b2;
@ -126,7 +126,8 @@ void iir_process(iir_filter_t *filter, sample_t *samples, int length)
/* process filter */
for (i = 0; i < length; i++) {
in = *samples;
/* add a small value, otherwise this loop will perform really bad on my 'nuedel' machine!!! */
in = *samples + 0.000000001;
for (j = 0; j < iterations; j++) {
out = in * a0 + z1[j];
z1[j] = in * a1 + z2[j] - b1 * out;
@ -163,7 +164,8 @@ void iir_process_baseband(iir_filter_t *filter, float *baseband, int length)
/* process filter */
for (i = 0; i < length; i++) {
in = *baseband;
/* add a small value, otherwise this loop will perform really bad on my 'nuedel' machine!!! */
in = *baseband + 0.000000001;
for (j = 0; j < iterations; j++) {
out = in * a0 + z1[j];
#ifdef DEBUG_NAN

@ -92,7 +92,6 @@ int fm_mod_init(fm_mod_t *mod, double samplerate, double offset, double amplitud
/* generate ramp up with ramp_length */
for (i = 0; i < mod->ramp_length; i++)
mod->ramp_tab[i] = 0.5 - cos(M_PI * i / mod->ramp_length) / 2.0;
mod->ramp_tab[0] = mod->ramp_tab[1] / 2.0; /* never be 0 */
return 0;
}
@ -199,10 +198,6 @@ again:
dev = offset + *frequency++;
power++;
length--;
/* somehow we need to have some value, otherwise IIR filter will be very slow!
* we still continue with a carrier, but it has very low amplitude.
* the low amplitude is set in ramp_tab[0]
*/
if (fast_math) {
phase += 65536.0 * dev / rate;
if (phase < 0.0)

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