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a-EQ: DSP bugfix

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Previously there were large spurious spikes in the signal when
the bandwidth parameter was adjusted on a pure sine tone
for the peaking circuits. This has been *greatly* reduced if not
eliminated by fixing a typo in two of the equations.
This commit is contained in:
Damien Zammit 2017-06-08 02:04:12 +10:00
parent c4a4857b87
commit ca815acd61
1 changed files with 2 additions and 2 deletions
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4
libs/plugins/a-eq.lv2/a-eq.c
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@ -270,12 +270,12 @@ activate(LV2_Handle instance)
static void linear_svf_set_peq(struct linear_svf *self, float gdb, float sample_rate, float cutoff, float bandwidth) static void linear_svf_set_peq(struct linear_svf *self, float gdb, float sample_rate, float cutoff, float bandwidth)
{ {
double f0 = (double)cutoff; double f0 = (double)cutoff;
double q = (double)pow(2.0, 1.0 / bandwidth) / (pow(2.0, bandwidth) - 1.0); double q = (double)pow(2.0, 0.5 * bandwidth) / (pow(2.0, bandwidth) - 1.0);
double sr = (double)sample_rate; double sr = (double)sample_rate;
double A = pow(10.0, gdb/40.0); double A = pow(10.0, gdb/40.0);
self->g = tan(M_PI * (f0 / sr)); self->g = tan(M_PI * (f0 / sr));
self->k = 1.0 / (q * A); self->k = 1.0 / q;
self->a[0] = 1.0 / (1.0 + self->g * (self->g + self->k)); self->a[0] = 1.0 / (1.0 + self->g * (self->g + self->k));
self->a[1] = self->g * self->a[0]; self->a[1] = self->g * self->a[0];