int count;
};
-TimeFilter *ff_timefilter_new(double clock_period,
- double feedback2_factor,
- double feedback3_factor)
+/* 1 - exp(-x) using a 3-order power series */
+static double qexpneg(double x)
+{
+ return 1 - 1 / (1 + x * (1 + x / 2 * (1 + x / 3)));
+}
+
+TimeFilter *ff_timefilter_new(double time_base,
+ double period,
+ double bandwidth)
{
TimeFilter *self = av_mallocz(sizeof(TimeFilter));
- self->clock_period = clock_period;
- self->feedback2_factor = feedback2_factor;
- self->feedback3_factor = feedback3_factor;
+ double o = 2 * M_PI * bandwidth * period * time_base;
+ self->clock_period = time_base;
+ self->feedback2_factor = qexpneg(M_SQRT2 * o);
+ self->feedback3_factor = qexpneg(o * o) / period;
return self;
}
/// update loop
self->cycle_time += FFMAX(self->feedback2_factor, 1.0 / self->count) * loop_error;
- self->clock_period += self->feedback3_factor * loop_error / period;
+ self->clock_period += self->feedback3_factor * loop_error;
}
return self->cycle_time;
}
+double ff_timefilter_eval(TimeFilter *self, double delta)
+{
+ return self->cycle_time + self->clock_period * delta;
+}
+
#ifdef TEST
#include "libavutil/lfg.h"
#define LFG_MAX ((1LL << 32) - 1)