Function vSyncInfoCalc

pcsx2/Counters.cpp:203–260

}

static void vSyncInfoCalc(vSyncTimingInfo* info, double framesPerSecond, u32 scansPerFrame)
{
	constexpr double clock = static_cast<double>(PS2CLK);

	const u64 Frame = clock * 10000ULL / framesPerSecond;
	const u64 Scanline = Frame / scansPerFrame;

	// There are two renders and blanks per frame. This matches the PS2 test results.
	// The PAL and NTSC VBlank periods respectively lasts for approximately 22 and 26 scanlines.
	// An older test suggests that these periods are actually the periods that VBlank is off, but
	// Legendz Gekitou! Saga Battle runs very slowly if the VBlank period is inverted.
	// Some of the more timing sensitive games and their symptoms when things aren't right:
	// Dynasty Warriors 3 Xtreme Legends - fake save corruption when loading save
	// Jak II - random speedups
	// Shadow of Rome - FMV audio issues
	const bool ntsc_hblank = gsVideoMode != GS_VideoMode::PAL && gsVideoMode != GS_VideoMode::DVD_PAL;
	const u64 HalfFrame = Frame / 2;
	const float extra_scanlines = static_cast<float>(IsProgressiveVideoMode()) * (ntsc_hblank ? 0.5f : 1.5f);
	const u64 Blank = Scanline * ((ntsc_hblank ? 22.5f : 24.5f) + extra_scanlines);
	const u64 Render = HalfFrame - Blank;
	const u64 GSBlank = Scanline * ((ntsc_hblank ? 3.5 : 3) + extra_scanlines); // GS VBlank/CSR Swap happens roughly 3.5(NTSC) and 3(PAL) Scanlines after VBlank Start

	// Important!  The hRender/hBlank timer ratio below is set according to PS2 tests.
	// in EE Cycles taken from PAL system:
	// 18876 cycles for hsync
	// 15796 cycles for hsync are low (render)
	// Ratio: 83.68298368298368
	u64 hRender = Scanline * 0.8368298368298368f;
	u64 hBlank = Scanline - hRender;

	if (!IsInterlacedVideoMode())
	{
		hBlank /= 2;
		hRender /= 2;
	}

	//TODO: Carry fixed-point math all the way through the entire vsync and hsync counting processes, and continually apply rounding
	//as needed for each scheduled v/hsync related event. Much better to handle than this messed state.
	info->Framerate = framesPerSecond;
	info->GSBlank = (u32)(GSBlank / 10000);
	info->Render = (u32)(Render / 10000);
	info->Blank = (u32)(Blank / 10000);
	const u64 accumilated_vrender = (Render % 10000) + (Blank % 10000);
	info->Render += (u32)(accumilated_vrender / 10000);

	info->hRender = (u32)(hRender / 10000);
	info->hBlank = (u32)(hBlank / 10000);
	info->hScanlinesPerFrame = scansPerFrame;

	const u64 accumilatedHRenderError = (hRender % 10000) + (hBlank % 10000);
	const u64 accumilatedHFractional = accumilatedHRenderError % 10000;
	info->hRender += (u32)(accumilatedHRenderError / 10000);
	info->hSyncError = (u32)((accumilatedHFractional * (scansPerFrame / (IsInterlacedVideoMode() ? 2 : 1))) / 10000);

	// Note: In NTSC modes there is some small rounding error in the vsync too,
	// however it would take thousands of frames for it to amount to anything and
	// is thus not worth the effort at this time.
}