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https://github.com/RetroPortingToolKit/psxrecomp
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tetrisgm
48 lines
1.8 KiB
C
48 lines
1.8 KiB
C
/*
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* guest_clock.h — pure guest-clock relationships shared by runtime code and
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* timing tests.
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*
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* The PS1 CPU clock is the common source for CRTC VBlank, SPU production, and
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* CD timing. Keeping these relationships here makes PAL×2 audits test the
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* same arithmetic used by the runtime instead of reproducing it in a script.
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*/
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#ifndef PSXRECOMP_GUEST_CLOCK_H
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#define PSXRECOMP_GUEST_CLOCK_H
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#include <stdint.h>
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#define PSX_GUEST_CPU_CLOCK_HZ 33868800ull
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#define PSX_GUEST_AUDIO_SAMPLE_HZ 44100ull
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#define PSX_GUEST_AUDIO_CYCLES_PER_SAMPLE 768ull
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static inline uint32_t psx_guest_crtc_period_cycles(uint32_t base_cycles,
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uint32_t multiplier) {
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if (multiplier < 1u) multiplier = 1u;
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if (base_cycles == 0u) return 0u;
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return base_cycles / multiplier;
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}
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/* Return the exact guest VBlank rate as a rational numerator/denominator.
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* Callers that need floating-point presentation can divide the two values;
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* tests can compare rates without introducing a rounding dependency. */
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static inline uint64_t psx_guest_crtc_hz_num(uint32_t period_cycles) {
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return period_cycles ? PSX_GUEST_CPU_CLOCK_HZ : 0ull;
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}
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static inline uint32_t psx_guest_crtc_hz_den(uint32_t period_cycles) {
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return period_cycles;
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}
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/* Consume guest cycles into 44.1 kHz SPU frames while preserving the exact
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* fractional-cycle remainder across calls. */
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static inline uint64_t psx_guest_audio_frames_for_cycles(uint64_t cycles,
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uint64_t *carry) {
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uint64_t remainder = carry ? *carry : 0ull;
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uint64_t total = cycles + remainder;
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uint64_t frames = total / PSX_GUEST_AUDIO_CYCLES_PER_SAMPLE;
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if (carry) *carry = total % PSX_GUEST_AUDIO_CYCLES_PER_SAMPLE;
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return frames;
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}
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#endif /* PSXRECOMP_GUEST_CLOCK_H */
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