OSSC to PC CRT – doesn't fill the screen.

[drojman]

Hi folks,

I’m using the OSSC with my original xbox. The 480p image it puts out is really nice. However I do have an issue. I can’t adjust the monitor using the OSD controls enough to actually completely fill the screen horizontally. I don’t really know how it works, but I’m assuming it’s because the OSSC is outputing a wider image than what is actually being displayed if that makes any sense.

Is there anything I can do to correct this? It’s not terrible, since it’s probably half an inch off the width of the monitor, so it’s fairly large still, but I would like to fix it if possible.

Thanks.

[nmalinoski]

If you’re trying to display a 16:9-ratio 480p image, and your monitor doesn’t have an aspect ratio control, there really isn’t much you can do; anamorphic widescreen video is compressed into a 4:3 frame, which is then intended to be stretched horizontally by the display, which means you need a display that can do that.

Normally, I’d say that the OSSC’s lack of a framebuffer prevents it from doing these kinds of transformations, but I would think a horizontal stretch/reframe would be quite possible with its linebuffer.

[drojman]

All the monitor has is the ability to stretch it, on a step basis, you can’t directly choose the aspect ratio. There is an auto adjust where it centers the image but that just leaves me with the black bars all around. Vertically I have more than enough room to expand the image.

But said the H adjustment on my monitor is already at about 80 and if I stretch it all the way to 100 it doesn’t quite reach.

I’ve seen suggestions that you can adjust the sampling rate but honestly I have no idea where to start.

[Harrumph]

You have a Crt monitor with DVI-D input or you’re using a HDMI to analog converter?
I don’t quite know if the active area has any practical meaning in the analog realm (I’m guessing it does not) but you can try changing h.active to 704. Likewise, increasing h.samplerate may not do anything either, because in analog it’s not the amount of samples originally that matters, rather the total time of the scanline, and this cannot be changed by the OSSC.

[drojman]

Yep, it’s running through a HDMI to VGA converter.

I’ll try editing those, I’m fairly sure I’ve messed about with them on here and had little success.

The annoying thing is I had an iiyama CRT that worked great and I could widen the image enough, although thinking about it the Dell CRT I have no is two inches bigger so the screen size is still probably larger than the iiyama.

[nmalinoski]

What make/model of CRT are you trying to use?

If you’re using a 4:3 VGA CRT, it doesn’t seem unreasonable that you wouldn’t be able to stretch the image horizontally enough to fill the width of the screen, because such a monitor wouldn’t have been designed to accommodate that sort of content. I would either disable widescreen modes on the Xbox to use the display’s intended image format, or I’d use an additional video processor between the OSSC and the CRT that can perform the horizontal stretching so the monitor receives the image in the proper aspect ratio (and then you’ll need to deal with letterboxing).

If, however, you’re using a 16:9 or 16:10 CRT, and it doesn’t have any aspect ratio controls like you said (adjusting horizontal size does not count), then you’ll need an additional video processor to perform the horizontal stretching so the monitor receives the image in the proper aspect ratio. You may also wish to consider using a Framemeister, which would be able to correctly stretch an anamorphic widescreen image.

[drojman]

Oh it’s a 4:3 CRT.

A Dell P1130 to be exact, but surely that should be able to take image from the OSSC? Or is it the case that despite the game being 4:3, the image the OSSC outputs is 16:9. and the CRT is just trying to accomodate that?

I would consider an additional processor if such a one would exist that would work easily between the OSSC and the monitor, however I’m guessing one that would work nicely for gaming would be really expensive?

Edit:

Some games fill the screen perfectly. Odd.

[nmalinoski]

It’s going to depend on everything is configured. I would expect good results having the Xbox configured for 480p and widescreen disabled; and the OSSC set to pass-through 480p and line2x 480i (these are defaults). If your monitor supports 960p, you should be able to swing line4x on 480i and line2x on 480p, but test with the smaller dimensions first.

If you’ve got the Xbox set to allow widescreen, it’ll output anamorphic widescreen in compatible games/menus, which is still a 4:3 frame (and the OSSC doesn’t read the aspect ratio metadata from the Xbox’s component output, so it has no idea it’s not 4:3), so that’ll give you that horizontal squishing in those instances.

Depending on the input you’re using on the OSSC, you might also end up with some weirdness with DTV 480p enabled (defaulted on for AV1, AV2; defaulted off for AV3), which makes the OSSC increase the sample rate, giving you 720×480 output (Typical dimensions of consumer-grade SD/ED content); changing ‘480p in sampler’ from ‘Auto’ to ‘VESA 640×480@60’ might give you a wider image at the expense of a slightly incorrect aspect ratio (which you should be able to adjust using the monitor’s image adjustments) or slight clipping of the left and right sides.

[drojman]

Okay, I’m wondering now if it’s just due to the internal rendering resolution of the game. Halo and TimeSplitters both render perfectly to the edge of the screen. Mortal Kombat doesn’t. These are all NTSC copies running in 480p, so it should all be the same.

Thanks for thetip RE the DTV thing. Unfortunately there was no difference. Looking at it here next to me now, it really is just a half a centimeter away from filling the screen, so it’s more of an annoyance than a real issue. I wonder if there’s a way I can configure the monitor internally to stretch the image more.

[nmalinoski]

I’m not so sure with the Xbox, but I know PS2 games often had overscan built in, because that was normal back then. It wouldn’t surprise me if there were some games on the Xbox that still did that; that was an awkward generation, as far as video output goes.

[drojman]

Yeah, PS2 it definitely is like that. I tried a game I think Mortal Kombat in 480i, and I get junk pixels in the top left (normal I believe) which are rendered right to the edge of the screen, even though the game image itself doesn’t stretch that far.

Definitely some odd behaviour though. Vertically stretching Halo enough to get the image just perfect, I then load another game and its waaaaay stretched vertically.

[drojman]

Just a quick update, I tried my Xbox directly into my TV, cutting out the OSSC completely. Seems that some games do indeed render differently, despite being the same output resolution. Not a problem in the end, but interesting to know.

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