ps2 240p timings

[phl0w]

Hi there,
I read for hours about optimal timings but cannot figure out (nor find) timings for PS2 games that are in 240p. I have a game (DDP DaiOuJou) that runs in 320×240. I use RGB Scart into the OSSC, and an HMDI cable from OSSC to my Gaming monitor. I chose 4x to have it displayed on my screen at 1280×960. The adv. timings show the following:

samplerate: 1560
synclen 72
h.backp 170
h. active 1280
v. synclen 3
v. back 15
v. active 240
phase 180°

OSSC info: 263-p
15,72khz 59,79Hz (sometimes it shows 59,82hz)

Can anyone help me with optimal timings, please, especially the sample rate seems weird.Thanks

[Zacabeb]

The sample rate looks to be based on square pixel NTSC timings oversampled at 2x.

The timings for original PlayStation games are slightly different from normal NTSC timings, given the non-interlaced output. The PlayStation2 in turn has a subpixel clock based on an integer multiple of the 13.5 MHz BT.601 standard, rather than being an multiple of the 44,100 kHz audio clock of the PlayStation. This further alters the desired timings when playing original PlayStation games on a PlayStation2.

Since the PlayStation2 outputs a narrower picture than a PlayStation because of the different subpixel clock, square NTSC timings might not be optimal when playing PlayStation games.

I suggest testing the following:
H.samplerate: 1716
H.synclen: 124
H.backporch: 194
H.active: 1280
V.synclen: 3
V.bachporch: 15
V.active: 240

If it works with your display, you might still need to tweak H.backporch to center the image. You might also get some clarity issues with games that use a 384 or 512 pixel resolution, though those issues exist also when using square pixel timings.

[phl0w]

Thanks for the in-depth response, really appreciate it.
I tried your suggestion and the sample rate* stretches the picture far beyond the borders the PS2 puts out.I had to reduce it to 1640 to get a picture within the resolution’s boundaries. I then payed around with back porch to center the image.
The thing with this game is that it’s a weird one. It’s output is 224×448 (in Tate like the arcade).

You might also get some clarity issues with games that use a 384 or 512 pixel resolution

I don’t care about other games. I maintain a ps2 exclusively for this game alone plus another shmup which has the same 224×448 output. That’s why I really wanna fine tune the OSSC for this kind of signal.
Any ideas or should I stick with 1640 if it works? Thing is I don’t notice a difference to the 1560 I had it set to before.

* you came up with that sample rate via pixel clock/h.frequency right? 13500000/15730=858,xxx -> x2 oversampling = 1716,xxx. I guess this would yield a proper picture for a standard 240p (320×240) signal? But the game being that weird (224×448) it’s a different thing.

another edit: I used line2x and it defaults to half the settings you recommended (858 samplerate and 62 h.synclen). However, at line2x my monitor renders it at 720×480 which is a 3:2 aspect ratio instead of 4:3.

[Zacabeb]

Since the signal gets oversampled, whichever timings produce the correct aspect ratio are the ones to go for unless you want pixel perfect sampling and scaling.

The timings I calculated were indeed based on the default BT.601 timings, with the assumption the game runs at 320 pixels width, doubled and centered within the 720 pixel active area.

The PlayStation2’s subpixel clock is usually quadruple BT.601 at ≈54 MHz, with the source resolution fit into the output through programmable pixel repetition. This means many standard raster widths (256, 320, 512, 640) get the same width in the output signal (2560 subpixels), while some others may not (384 for instance becomes slightly wider at 2688 subpixels). I don’t know what DonDonPachi DaiOuJou does to fit its resolution, but it might have set up the horizontal multiplier to a custom value.

[phl0w]

Thanks again, learning a lot.
I just found that line5x with format 1600×1200 produces the cleanest, sharpest image.
advanced timings are:
samplerate 2046
h.synclen 150
h.active 1600
v. synclen 3
v. back porch 15
v. active 240
phase 180°

Can I optimise this? There is a thin blue noise line to the left of the picture. How do I get rid of this?

EDIT: Found a note that at line5x 1600×1200 one should set samplerate to 1950. Did it and it got rid of the blue line and the image to my eyes really is as good as it gets, I guess.

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