Optimal timings

The advanced timing options on the OSSC allow for fine control over how the output image is generated and how the analogue signal is sampled. In some cases it is possible to adjust these values to perfectly match the incoming analogue signal from a console. This results in a very sharp image (possibly even too sharp for many people's tastes).

The table below contains some preliminary timings for popular consoles, it should be considered a work in progress, do not be surprised if further fine tuning is required.

Console / mode	Dots per scanline / no. scanlines / @dotclk	OSSC base mode	Modified parameters	Notes	PC modeline
NES 256x240 @60.10Hz	341* / 262 / @5.37MHz(NTSC) [1][2][3]	256x240		To reduce jitter in couple topmost lines, try disabling ""Allow TVP HPLL2x" and/or using mask. * one scanline is typically 1 dot shorter on every other frame	Modeline "ossc_nes_1280x720_60.08" 80.55 1280 1385 1510 1705 720 729 738 786 -hsync -vsync
SNES 256x239/224 @60.10Hz	341* / 262 / @5.37MHz(NTSC) @5.32MHz(PAL) [4]	256x240		* one scanline is typically 1 dot shorter on every other frame	Modeline "ossc_snes_1280x720_60.08" 80.55 1280 1385 1510 1705 720 729 738 786 -hsync -vsync
Mega Drive 320x224 @60Hz	320×8 + 86×10 (?) / 262 / @53.693175MHz(NTSC) @53.203425MHz(PAL)	320x240	H.samplerate=428 (?)
Mega Drive 256x224 @60Hz	342 / 262 / @5.37MHz(NTSC) @5.32MHz(PAL) [5][6]	256x240	H.samplerate=342
N64 320x240 @60Hz	773.25 (?) / 262 / @12.17MHz(NTSC) @12.41MHz(PAL) [7][8]	320x240	H.samplerate=387, H.synclen=22, H.backporch=36	Every other visible dot (of 640) is interpolated
PSX 320x240 @59.82Hz	426.625 (?) / 263 / @6.71MHz(NTSC) @6.65MHz(PAL) [9] [10]	320x240	H.active=320, H.samplerate=427, H.synclen=76, H.backporch=63	Example games: Chrono Cross
PSX 384x240 @59.82Hz	487.5 / 263 / @7.67MHz(NTSC)	320x240	H.active=384, H.samplerate=487, H.synclen=63, H.backporch=18	Example games: Ape Escape, Castlevania SotN (menus only)
PSX 256x240 @59.82Hz	341.25 / 263 / @5.369MHz(NTSC)	256x240	H.active=256, H.samplerate=341, H.synclen=26, H.backporch=39	Example games: Adventure of Little Ralph, Castlevania SotN (in-game only)
PSX 512x240 @59.82Hz	682.5 / 263 / @10.74MHz(NTSC)	240p	H.active=512, H.samplerate=683, H.synclen=10, H.backporch=117	Example games: Crash Bandicoot (resolution of the dithering)
Saturn 320x240 @60Hz	427 / 263 / @6.71MHz(NTSC) [11][]	320x240	H.samplerate=427
Neo-Geo MVS 320x240 @59.19Hz	384 / 264 / @6.00MHz [12]	320x240	H.samplerate=384, H.backporch=25
DC VGA @60Hz	858 / 525 / @27MHz [13]	480p	H active=640
GBI ULL 480p @59.72Hz	866 / 522 / @27MHz ?	480p	H samplerate=866 ?
CPS2 384x224 @59.64Hz	512 / 262 / @8MHz	320x240	H.samplerate=512, H.active=384, H.backporch=66
PC-98 640x400 @56.4Hz	848 / 440 / @21.0526MHz	640x384	H.samplerate=848, H.backporch=80, H.synclen=64,, V.active=400, V.backporch=25
Seibu SPI	? / 293 (?)	?

Horizontal multiplication factors

Frame width is multiplied by an integer factor defined below while picture area is multiplied by the value in parenthesis (if different) to maintain correct aspect ratio. Vertical multiplication factor is defined directly by line multiplication mode. For example, consider 320x240 in line3x mode. Frame size is multiplied by 4 in horizontal direction, and by 3 in vertical direction to generate a frame of 1280x720 which is ideal for 720p output. However, picture area is only multiplied by 3 in horizontal direction so that effective area (960x720) maintains 4:3 ratio of the source.

	320x240	256x240 (4:3)	256x240 (8:7)
Line2x	2x	3x	3x(2x)
Line3x	4x(3x)	5x(4x)	5x(3x)
Line4x	4x	5x	5x(4x)
Line5x	5x*	6x*	6x(5x)*

• With Line5x, horizontal active and mask are adjusted internally so that frame width of 1600 or 1920 (depending on "Line5x format") is always generated. In 1920x1080 format, vertical active and backporch are also internally adjusted (-24 and +12) to generate suitable frame height.

The FirebrandX optimal timing method

Community member FirebrandX has produced a useful YouTube video tutorial on how to discover optimal video timings. This video can be viewed here.