Making a linedoubler.....

[fagin]

I've been speaking to Bencao74 about things and looking at building a linedoubler cropped up in conversation. It was only in passing as the logistics of building a 240p to 480p device would undoubtedly be fraught with issues. Bencao74 has looked at a couple of IC solutions, but with the envisaged "headache" that was surely to follow I suspect it will be a no goer.

Producing a unit that takes a 240p RGB signal and linedoubles to 480p "pin sharp" with no lag (aka XRGB) would be the ultimate goal, I'm sure you would agree.

Just been doing some research and I stumbled across these FPGA dev boards. I have no idea what they could be capable of doing, but is this something that could be a use for them?

On a side note......

I have stumbled across a project that some guy has done, with taking the output from a GBA and scaling it. The results look pretty awesome....





Does anyone know anything about using FPGA boards for this kind of purpose?

[Fudoh]

Scaling a GBA picture can't be compared to what you would like to achieve. The GBA project likely uses a LVDS connection to the LCD panel, which is a strictly digital link, so you don't have to deal with A/D, D/A conversions and frequencies as you would have to with analogue signals.

Speaking of FPGA processors: they are too expensive to build such a project for a small production run. DVDO used FPGAs in their VP20/30/50/50Pro series. Later on they took most of the FPGA features and put them into some ASIC design which then became the ABT2010 included in the Edge and the 2015 included in the Duo.

A FPGA will pretty much do anything you program into it. The number of gate arrays used for simple linedoubling shouldn't be too much, but even FPGA boards with little gates are quite expensive. The proper approach to build a linedoubler would be to chose a proper IC instead. Something low end from Marvell or Sigma or some old stock like a Sage FLI-2200.

[fagin]

Fudoh,
Ahhh.... didn't think about the A/D conversion stuff.

I assume the XRGB is FPGA based?

FPGA dev boards seem to vary massively in price, which I assume based on your statement, would partly be down to the number of gates?

The GBA project was based on a hacked PC video card iirc.

[Fudoh]

which I assume based on your statement, would partly be down to the number of gates?

probably. Eventually it likely comes down to the processing power you need.

Yes, the XRGB is FPGA based. Lumagen's Radiance uses a Gennum VXP plus a big FPGA.

[Ex-Cyber]

If you just want to do a barebones linedoubler and not some fancy unit with all kinds of scaling options and on-screen configuration, I don't think it would take a very big FPGA. You'd mostly need to look out for having enough block RAM for your line stores and enough I/O bandwidth to move the data in/out of the chip.

edit: you might draw some inspiration from this design.

[neorichieb1971]

I'd like something similar to deal with 4:3 content on a 16:9 TV.

My TV expands from 4:3 to 16:9 but nothing in between. This makes gaming a little bit of an eyesore or a barren wasteland layout.

If a product came out that stretched the screen so it was kinda anamorphically stretched by 15% I would like that better.

[SGGG2]

No link to the GBA project...

EDIT: http://axio.ms/projects/iiyamameetxilinx/

[undamned]

My TV expands from 4:3 to 16:9 but nothing in between. This makes gaming a little bit of an eyesore or a barren wasteland layout.

If a product came out that stretched the screen so it was kinda anamorphically stretched by 15% I would like that better.

Gross In the context of gaming, 4:3 content was designed that way specifically. Any manipulation of that ratio is perversion.
-ud

[Strider77]

10 to 15 percent is barely noticeable on game art. Look at the CPS2 saturn ports... they are stretched from the arcade boards original ratio.

[Fudoh]

they are stretched from the arcade boards original ratio.

are they ? I just assumed that the pixel aspect ratio was changed, since the Saturn doesn't support the high horizontal resolution of the CPS2 boards. I mean, despite the strechted CPS2 resolution of 384x224, the games are supposed to run in 4:3 on a cab. In what resolution are the Saturn versions running ? 320x224 I assume - with 16 lines of black borders to get to the full 240p resolution. Again in 4:3. So what they did was rescaling the art and sprites on the horizontal, but not changing the AR. Don't you think ?

[neorichieb1971]

Having a 4:3 on a 16:9 is grosser. I'd rather it be slightly distorted and take up 80% of the screen then what I've got at the moment.

My TV does full height at 4:3, or 16:9 by stretching it right across the horizontal plane. Either way it looks stupid.

[ED-057]

I just assumed that the pixel aspect ratio was changed, since the Saturn doesn't support the high horizontal resolution of the CPS2 boards. I mean, despite the strechted CPS2 resolution of 384x224, the games are supposed to run in 4:3 on a cab. In what resolution are the Saturn versions running ?

I think Saturn ports like Street Fighter Collection and such use the Saturn`s 352 mode, so the graphics appears slightly wider compared to the arcade.

[fagin]

Having a 4:3 on a 16:9 is grosser. I'd rather it be slightly distorted and take up 80% of the screen then what I've got at the moment.

Wash your mouth out!!!!

That's like saying one prefers composite video over RGB!

Each to their own though.

[fagin]

If you just want to do a barebones linedoubler and not some fancy unit with all kinds of scaling options and on-screen configuration, I don't think it would take a very big FPGA. You'd mostly need to look out for having enough block RAM for your line stores and enough I/O bandwidth to move the data in/out of the chip.

edit: you might draw some inspiration from this design.

Mmm... interesting.

[neorichieb1971]

You can't buy 4:3 in the UK anymore, unless its old/used or less than 20". I suppose you could get a monitor.

[fagin]

You can't buy 4:3 in the UK anymore, unless its old/used or less than 20". I suppose you could get a monitor.

You don't need to though.... that's what the aspect ratio function is for on a widescreen set.

[undamned]

10 to 15 percent is barely noticeable on game art. Look at the CPS2 saturn ports... they are stretched from the arcade boards original ratio.

IIRC, the original CPSII frames look kinda stretched wide (just take a screen cap from mame). I heard somewhere that Capcom had designed their frames extra wide so that when the image was adjusted/sized on an arcade monitor (remember the joys of analog scaling?) to a proper 4:3 ratio it looked higher res?
-ud

[Fudoh]

to a proper 4:3 ratio it looked higher res

exactly!

[neorichieb1971]

The function might be there on a 16:9 TV to stretch a 4:3 but it looks like ass to me. Only having a choice of half the screen not used or a horribly distorted width is not really a good compromise imo.

Some TV's in the UK did 14:9 once upon a time. Something thats gone now a days.

[Strider77]

to a proper 4:3 ratio it looked higher res

exactly!

You are right... my analogy wasn't so great and I didn't word myself that great either. With CPS2 on saturn [ports] if I adjusted my display to make them look proper, that meant I had to readjust them back once I played something else non CPS2 on saturn. I didn't and don't bother b/c they looked great either way.

A better example are those SH3 shock inserts and other photoshop jobs I've done. I have stretched art in all of those all over the place but I never have heard one complaint that it looked stretched and wrong or any one say they noticed. That's b/c 10 to 15 percent is barely noticeable.

My main point, analogies aside [great or not so great].... if not stretched out like crazy it's not a big deal. I'm sure we have all played games in the arcades while growing up that the aspect ration was off by at LEAST 10 percent at some point and not even noticed or cared.

Movies... when dealing with real world images then I'll notice in a heartbeat and it drives me up the walls.

My TV does full height at 4:3, or 16:9 by stretching it right across the horizontal plane. Either way it looks stupid.

Wait... so you think it still looks stupid even when you set the 16x9 TV to display at 4x3?!? You must have hated letter boxed movies on 4x3 sets.

[bencao74]

hmm, what about this approach?



I think the core IC is the AL251 in this schematic. So it has a i2c interface and is in QFP64 package. So at least a MCU like AVR with i2c interface, an A/D changer plus this AL251 is needed.

I got in touch with the guys from averlogic. An evaluation board for the AL251 cost alone 230€. I got some docs either, if anyone is interested.

So at least such a project needs :

- HW Layouter with routing 64 pin ICs experience
- Experienced MCU Programmer ( forwarding a simple config to the AL251 via I2C)
- Electric guy with some experience on this A/D changer stuff

[Fudoh]

That's probably one of many ICs. Do you have any idea which device on the market uses the AL250/251 already ? It doesn't make sense to approach a certain IC without knowing how it handles upconversion in general. Many are completely unsuited to videogame upscaling.

[bencao74]

sure, just an starting point. The task to evaluate all this ICs is open ended. Alone this eval board here costs 230€. Hence I`Ve asked the product manager your question. I doubt that I`ll receive a meaningfull answer, since they wnt surely to sell their eval boards.

So a good evaluation starting point is to select a quite good and cheap scaler and then to get a clue about which IC are used?

Sounds like using the gbs8220 right from the start. It is cheap and has medium performance.... But is it then worth to build a sort of replacement?

[Fudoh]

So a good evaluation starting point is to select a quite good and cheap scaler and then to get a clue about which IC are used?

my initial suggestion was to pick a good and ONCE EXPENSIVE linedoubler or scaler and to see if it can be duplicated for little money today. There haven't been many ICs which are really suited for 240p material. The Genesis/Sage/Faroudja FLI-2200 (or 2300 with scaler) is one of them. The 2200 is 10 years old now and long out of production, but the IC manufacturers have lots of stock, both original and clones and I could imagine that they're quite cheap by now.

Sounds like using the gbs8220 right from the start. It is cheap and has medium performance.... But is it then worth to build a sort of replacement?

no, of course not. You wouldn't be able to produce something to match this price. It would be interesting though to tweak the firmware. The HDBoxPro has a proper setting for 240p material while the 8220 has not, although they use the same processor. Nevertheless performance remains mediocre - or medium as you've put it.

[fagin]

IMO this would only be worth doing if it was possible to replicate (or close to it) XRGB levels of linedoubling clarity for a good price.

Surely ambitous!

Anyone got the brains to reverse engineer a XRGB for 50p!

[bencao74]

jep, a I assumed, I was stepping in confidential information with my second mail. But the product manager told me some quantities :

"Alone in germany was started about 10 project in the last years. The part is use in industrial applications, farming, but also in medicine for converting video signals. In asia this part will be used for lcd panels with tv input or LCD procectors, not to mention video cut techniques. "

though doesn't help, really.. at least not the pushing words to make me buy the eval board ))

so, take a look at the 2200 ICs...

[fagin]

Doing some more digging around and I have found out that one of my original scalers uses the AL250 chipset. Inputs are limited to svhs or composite, but I will set it up and see how it looks. Haven't used it for years.

[fagin]

Utter gash...... but I suspect that is because of the quality of AD conversion (using a Phillips IC - 7111AHZ) from source and the fact that the AL250 is configured (in this scaler) to have maximum anti-aliasing etc etc. The luminance is terrible via this specific scaler to a LCD.

Unfortunately with this specific AD IC installed I can't even tap into the IC to accept a RGB signal.... it's CVBS or Y/C only analogue inputs.