mirror of
https://github.com/RetroPortingToolKit/psxrecomp
synced 2026-10-30 11:37:21 -04:00
Alex Vanderveen
79 lines
3.7 KiB
C
79 lines
3.7 KiB
C
/*
|
|
* host_clock.h — the host's simulation/presentation pacing clock.
|
|
*
|
|
* TWO INDEPENDENT DEADLINES: when the next guest frame is due, and when the
|
|
* next PRESENTED frame is due. They coincide for a host that presents once per
|
|
* guest frame, which is what this engine does today. Decoupling them lets the
|
|
* display run at its own steady cadence while the guest runs at whatever rate
|
|
* the machine manages. `alpha` is the interpolation weight between two
|
|
* simulated frames for a presenter that wants to blend.
|
|
*
|
|
* PORTED FROM snesrecomp, runner/src/desktop/host_clock.{h,c}, where it is
|
|
* SnesHostClock and had itself been lifted out of SuperMetroidRecomp's
|
|
* sm_video.c. The logic is transcribed unchanged; only the names and the
|
|
* default frame rate differ. Keeping it recognisable across the three
|
|
* recompilers is deliberate: a divergence should be a deliberate edit with a
|
|
* reason, not drift.
|
|
*
|
|
* WHY IT IS HERE. `frame_pacing.c` is a DEADLINE CAP — it holds the frame to
|
|
* 59.94 Hz when the guest is running fast, and when the guest is slower than
|
|
* real time it re-anchors and runs free (frame_pacing.c, the debt comment).
|
|
* That is the right answer for pacing the SIMULATION and is unchanged. It has
|
|
* no answer for the display's cadence when the guest cannot keep up: every
|
|
* frame is then rounded up to a whole refresh interval and the result is
|
|
* visible judder. This clock is the other half — it decides WHEN TO DRAW,
|
|
* independently of how fast the guest is going.
|
|
*
|
|
* It is also the engine-side half of the seam docs/LAUNCHER_CORE.md cuts:
|
|
* "pacing *of the simulation*" stays in the engine, "pacing of presentation,
|
|
* vsync policy" moves to the launcher. Having the presentation clock as its own
|
|
* object is what makes that split a move rather than a rewrite.
|
|
*
|
|
* Measured on the sibling N64 project, which took this port first: decoupling
|
|
* at 30 Hz made the guest 11.6 % FASTER while giving a steady cadence, because
|
|
* a frame that is not DRAWN was still SIMULATED. Capping the cadence instead --
|
|
* holding the emulation thread to the deadline -- cost 37 % of guest speed.
|
|
*/
|
|
#ifndef PSXRECOMP_HOST_CLOCK_H
|
|
#define PSXRECOMP_HOST_CLOCK_H
|
|
|
|
#include <stdbool.h>
|
|
#include <stdint.h>
|
|
|
|
#ifdef __cplusplus
|
|
extern "C" {
|
|
#endif
|
|
|
|
/* NTSC PSX frame rate; matches main.cpp's PSX_FRAME_PERIOD_MS = 1000/59.94. */
|
|
#define PSX_HOST_NTSC_HZ 59.94
|
|
|
|
typedef struct PsxHostClock {
|
|
double next_simulation, next_presentation;
|
|
double simulation_hz, presentation_hz;
|
|
uint64_t simulation_frames, presentations, missed_presentations;
|
|
} PsxHostClock;
|
|
|
|
void psx_host_clock_reset(PsxHostClock* c, double now,
|
|
double simulation_hz, double presentation_hz);
|
|
bool psx_host_clock_simulation_due(const PsxHostClock* c, double now);
|
|
/* `elapsed_periods` is how many guest frame periods the simulated frame
|
|
* actually spanned; a lag frame spans more than one. */
|
|
void psx_host_clock_simulation_done(PsxHostClock* c, double now,
|
|
bool preserve_debt, double elapsed_periods);
|
|
bool psx_host_clock_presentation_due(const PsxHostClock* c, double now);
|
|
void psx_host_clock_presentation_done(PsxHostClock* c, double now);
|
|
double psx_host_clock_alpha(const PsxHostClock* c, double now);
|
|
double psx_host_clock_next_deadline(const PsxHostClock* c);
|
|
|
|
/* Which presentation rate to run at: an explicit fps when it is one the clock
|
|
* supports, else the display's refresh, clamped. 0 = display / every frame.
|
|
* Accepts any rate from 20 up, because the point is running BELOW the panel
|
|
* rate when the guest cannot keep up, not above it. */
|
|
bool psx_host_valid_fps(unsigned fps);
|
|
double psx_host_presentation_hz(unsigned fps, double display_refresh);
|
|
|
|
#ifdef __cplusplus
|
|
}
|
|
#endif
|
|
#endif /* PSXRECOMP_HOST_CLOCK_H */
|