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Hopefully this will fix the build errors

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arcadez2003 2024-08-17 19:53:39 +01:00 committed by GitHub
parent 99dfc6d319
commit dd43fddb29
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1 changed files with 100 additions and 0 deletions
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src/sound/filter.c
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@ -132,3 +132,103 @@ filter* filter_lp_fir_alloc(double freq, int order) {
return f;
}
void filter2_setup(int type, double fc, double d, double gain,
struct filter2_context *filter)
{
double w; /* cutoff freq, in radians/sec */
double w_squared;
double den; /* temp variable */
double two_over_T = 2*Machine->sample_rate;
double two_over_T_squared = two_over_T * two_over_T;
/* calculate digital filter coefficents */
/*w = 2.0*M_PI*fc; no pre-warping */
w = Machine->sample_rate*2.0*tan(M_PI*fc/Machine->sample_rate); /* pre-warping */
w_squared = w*w;
den = two_over_T_squared + d*w*two_over_T + w_squared;
filter->a1 = 2.0*(-two_over_T_squared + w_squared)/den;
filter->a2 = (two_over_T_squared - d*w*two_over_T + w_squared)/den;
switch (type)
{
case FILTER_LOWPASS:
filter->b0 = filter->b2 = w_squared/den;
filter->b1 = 2.0*(filter->b0);
break;
case FILTER_BANDPASS:
filter->b0 = d*w*two_over_T/den;
filter->b1 = 0.0;
filter->b2 = -(filter->b0);
break;
case FILTER_HIGHPASS:
filter->b0 = filter->b2 = two_over_T_squared/den;
filter->b1 = -2.0*(filter->b0);
break;
default:
logerror("filter2_setup() - Invalid filter type for 2nd order filter.");
break;
}
filter->b0 *= gain;
filter->b1 *= gain;
filter->b2 *= gain;
}
/* Reset the input/output voltages to 0. */
void filter2_reset(struct filter2_context *filter)
{
filter->x0 = 0;
filter->x1 = 0;
filter->x2 = 0;
filter->y0 = 0;
filter->y1 = 0;
filter->y2 = 0;
}
/* Step the filter. */
void filter2_step(struct filter2_context *filter)
{
filter->y0 = -filter->a1 * filter->y1 - filter->a2 * filter->y2 +
filter->b0 * filter->x0 + filter->b1 * filter->x1 + filter->b2 * filter->x2;
filter->x2 = filter->x1;
filter->x1 = filter->x0;
filter->y2 = filter->y1;
filter->y1 = filter->y0;
}
/* Setup a filter2 structure based on an op-amp multipole bandpass circuit. */
void filter_opamp_m_bandpass_setup(double r1, double r2, double r3, double c1, double c2,
struct filter2_context *filter)
{
double r_in, fc, d, gain;
if (r1 == 0)
{
logerror("filter_opamp_m_bandpass_setup() - r1 can not be 0");
return; /* Filter can not be setup. Undefined results. */
}
if (r2 == 0)
{
gain = 1;
r_in = r1;
}
else
{
gain = r2 / (r1 + r2);
r_in = 1.0 / (1.0/r1 + 1.0/r2);
}
fc = 1.0 / (2 * M_PI * sqrt(r_in * r3 * c1 * c2));
d = (c1 + c2) / sqrt(r3 / r_in * c1 * c2);
gain *= -r3 / r_in * c2 / (c1 + c2);
filter2_setup(FILTER_BANDPASS, fc, d, gain, filter);
}