2f9396e24a
The slope encodes the drift between the device clock and the computer clock. Its real value is expected very close to 1. To estimate it, just assume it is exactly 1. Since the clock is used to estimate very close points in the future, the error caused by clock drift is totally negligible, and in practice it is way lower than the slope estimation error. Therefore, only estimate the offset.
43 lines
1 KiB
C
43 lines
1 KiB
C
#ifndef SC_CLOCK_H
|
|
#define SC_CLOCK_H
|
|
|
|
#include "common.h"
|
|
|
|
#include "util/tick.h"
|
|
|
|
struct sc_clock_point {
|
|
sc_tick system;
|
|
sc_tick stream;
|
|
};
|
|
|
|
/**
|
|
* The clock aims to estimate the affine relation between the stream (device)
|
|
* time and the system time:
|
|
*
|
|
* f(stream) = slope * stream + offset
|
|
*
|
|
* Theoretically, the slope encodes the drift between the device clock and the
|
|
* computer clock. It is expected to be very close to 1.
|
|
*
|
|
* Since the clock is used to estimate very close points in the future (which
|
|
* are reestimated on every clock update, see delay_buffer), the error caused
|
|
* by clock drift is totally negligible, so it is better to assume that the
|
|
* slope is 1 than to estimate it (the estimation error would be larger).
|
|
*
|
|
* Therefore, only the offset is estimated.
|
|
*/
|
|
struct sc_clock {
|
|
unsigned range;
|
|
sc_tick offset;
|
|
};
|
|
|
|
void
|
|
sc_clock_init(struct sc_clock *clock);
|
|
|
|
void
|
|
sc_clock_update(struct sc_clock *clock, sc_tick system, sc_tick stream);
|
|
|
|
sc_tick
|
|
sc_clock_to_system_time(struct sc_clock *clock, sc_tick stream);
|
|
|
|
#endif
|