/*-----------------------------------------------------------------------------
* Set the frequency of triangular oscillator
* The frequency is converted in a slope value.
* The initial value is set according to frac_phase which is a position
* in the period relative to the beginning of the period.
* For example: 0 is the beginning of the period, 1/4 is at 1/4 of the period
* relative to the beginning.
* -----------------------------------------------------------------------------*/
void set_triangle_frequency(triang_modulator mod, float freq, float sample_rate, float frac_phase)
{
float ns_period; /* period in numbers of sample */
if (freq <= 0f)
{
freq = 0.5f;
}
mod.freq = freq;
ns_period = sample_rate / freq;
/* the slope of a triangular osc (0 up to +1 down to -1 up to 0....) is equivalent
* to the slope of a saw osc (0 . +4) */
mod.inc = 4f / ns_period; /* positive slope */
/* The initial value and the sign of the slope depend of initial phase:
* initial value = = (ns_period * frac_phase) * slope
*/
mod.val = ns_period * frac_phase * mod.inc;
if (1f <= mod.val && mod.val < 3f)
{
mod.val = 2f - mod.val; /* 1.0 down to -1.0 */
mod.inc = -mod.inc; /* negative slope */
}
else if (3f <= mod.val)
{
mod.val = mod.val - 4f; /* -1.0 up to +1.0. */
}
/* else val < 1.0 */
}
/*-----------------------------------------------------------------------------
* Get current value of triangular oscillator
* y(n) = y(n-1) + dy
* -----------------------------------------------------------------------------*/
float get_mod_triang(triang_modulator mod)
{
mod.val = mod.val + mod.inc;
if (mod.val >= 1f)
{
mod.inc = -mod.inc;
return(1f);
}
if (mod.val <= -1f)
{
mod.inc = -mod.inc;
return(-1f);
}
return(mod.val);
}
public modulator()
{
sinus = new sinus_modulator();
triang = new triang_modulator();
}
