480i 240p Interlacing etc

[invzim]

Posted this over at Arcade Otaku, and was sent here..

I'm scoping out parts (and techhnologies) needed to make an RGB upscaler, because the cheapo ones suck, and the xrgb2 is just not easily available, and the new frame meister is a bit expensive and has no VGA out. Anyho, a couple of the AD chips I'm looking at support 480i/576i.

I know the basics of interlacing, odd/even frames, 30hz etc, but not sure I completely understand it.

Is the interlace part just describing what/how the bitmap looks, but with the timing/retrace stuff identical to 240p? I.e if I had a 240p board and displayed an image with odd/even lines each alternating frame, would that be considered 480i?

[fagin]

Unless this is simply a "pet project" don't bother. You'll end up putting way too much time and effort into something, that can already be had for easy money off eBay (2nd hand).

Quick question.... why do you want to aim for a 480i ouput?

[invzim]

Unless this is simply a "pet project" don't bother. You'll end up putting way too much time and effort into something, that can already be had for easy money off eBay (2nd hand).

Quick question.... why do you want to aim for a 480i ouput?

Of course it is a "pet project", all good projects are Otoh, I've made a few hundred JVS-PACs, and I think at least some of the people using them would like an easy to use high quality upscaler to run JAMMA games on 31k only CRTs.

I don't aim for 480i output, the interlace question is in regards to input and AD converter IC's. None of the ones I've looked at specify support for 240p, but a few have support for 480i/576i. The pixelclock logic probably expects 640 or more pixels pr line, but that is fixable if the rest is equal.

I got an XRGB2 myself, and really like it. My only complain is that it doesn't do rtype2 for some reason, and it is a bit cumbersome with the JAP scart input when you first get it, and of course that it is tricky to track down and can be very expensive for what it is.

[Fudoh]

This is a very complicated topic.

The problem with (probably all of) the ICs you're looking at is that they do some kind of cheap deinterlacing by merging two successive fields into one frame. If you allow this you end up at a quality level of the the GBS8220 boards do. And with them being available for a mere $30 I don't see any reason why to take on such a project.

What would be great indeed would be a real linedoubler in the classic sense of the word. No deinterlacing at all, but just a pure 240p to 480p conversion. This would show shabby results on actual 480i content, but it would be awesome for 240p. That's basically what the 240p does and unfortunately I can't think of any IC to accomplish this. That's why Micomsoft - even for the Framemeister - had to opt for a FPGA solution ahain for the initial 240p processing.

The difference between 240p and 480i in technical terms is a half-line offset which tells the display either to display the fields on different line offsets (480i) or without any offset (240p). As long as you're just looking at A/D conversion, the difference shouldn't matter and the ICs should work with both types of signal. The problem is the next step.

And PS: The XRGB2 should do R-Type2 just fine. The problem is more likely that the monitor can't handle the output refresh rate....

[invzim]

The difference between 240p and 480i in technical terms is a half-line offset which tells the display either to display the fields on different line offsets (480i) or without any offset (240p). As long as you're just looking at A/D conversion, the difference shouldn't matter and the ICs should work with both types of signal. The problem is the next step.

And PS: The XRGB2 should do R-Type2 just fine. The problem is more likely that the monitor can't handle the output refresh rate....

Thanks for insights!

Where do you find/extract the half-line offset?

I don't plan on doing de-interlacing at all, at least not to begin with, and the targeted sources are RGB 15khz stuff. The ADC's I'm looking at are not "monolithic", i.e. they don't process the video at all - but you do have to fiddle about with PLL (clock) settings, which is the source of my need to understand 480i.

The plan is to use a small FPGA, or even CPLD to do the processing of the pixels coming from the AD chip. I also plan do to it pretty much real-time, doing a group of lines in one go and using the incoming sync signals to generate a double pixelclock.

And unfortunately, the xrgb2 does not do rtype 2 just fine It cuts the top/bottom so you can't see your score.

[Artemio]

Although it doens't cover 240p directly since it is not part of the standard at all, this book might help you: http://www.amazon.com/Digital-Video-Sec ... b_title_bk

[Ed Oscuro]

And unfortunately, the xrgb2 does not do rtype 2 just fine It cuts the top/bottom so you can't see your score.

The XRGB-2, or your monitor? The raw signal should have the whole frame in there. And, of course a silly question, but you did try using the output resizing/moving commands (all of them) from the XRGB-2 front panel, right?

[invzim]

I think the r-type (irem m72) is a known issue, http://www.youtube.com/watch?v=zkuc-9dlrs0 - ffwd to 14:00, the same issue I have.

[Fudoh]

But even if you were to create a linedoubler which ignores all the input timings and just blindly doubles, only a handful of old monitors would be able to show 512p55 from a R-Type PCB. And *none* of any modern TV sets for sure.

[dieKatze88]

Still, wouldn't a device that blindly doubles the number of lines displayed be incredibly useful to a lot of people?

Even if it doesn't work with one great game, it would work with a thousand other great games. I support this. I have had 3 different JVS-PACs in my hand (proxy buy for friends), they're fantastic products.

[Fudoh]

absolutely, I would appreciate any approach on a new upscaler. Anything with better quality than a GBS8220 would be highly welcomed by a huge number of players.