VBXE and Artifacting (Ultima IV is monochrome)?

[bfollowell]

If you're looking for an excuse for another awesome, and low cost, upgrade, then yes, I'll enable you. You need a UAV!

 

[Mclaneinc]

I like the emulator for the artifacting, I can colour correct it to something I like best and if you are using composite there's a good chance you will get the bars on real hardware where Altirra remains pretty clean even when in artifact mode.

[Keatah]

Warning! Apple II screenshots!

4 hours ago, Faicuai said:

We all know (better) that NTSC was never a shitty standard. It is THE PRIME TV standard, and where / what Atari 8bit family was designed from. 

 

Thanks to it, and its exploits, a ton of people out-there enjoyed colorful images out of machines that really could not produced them on their own... and all in a controlled and predictable way. Just ask Woz and Apple II owners... NEVER heard ANYONE complaining the colorful screens rendered out of artifacting (!)

I've always looked at artifacting as a way to increase resolution. Not necessarily to obtain extra "not native" colors. But any additional or different colors were of course always welcome.

 

The Apple II didn't have any sort of videochip whatsoever. It just pulsed the signal based on bits the video scanner read from ram. So one could say all of the Apple II's hi-res graphics were artifacted 100% of the time. All of the time.

 

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Even TODAY, the latest demo efforts for venerable IBM PC/5150 show the amazing stuff you can get out of its analog video combined with wise artifacting. Around 1,000 colors, or more.

I think there is a demo (8088) that gets 4096 colors from the CGA adapter - which was designed to output only 4. Numbers may be wrong on the numbers but I recall it being quite impressive.

 

3 hours ago, Faicuai said:

Don't know about you guys, but I remember not getting enough wonder out of this "mysterious" NTSC rendering, back in the day ?

We had something like that on the Apple II titled Brian's Theme. Shipped with every DISK II + DOS 3.3 package. I loved experimenting and modding that program to see what other effects I could come up with.

 

 

Gotta love the detail there. I think we were getting like 560 dots across or something in the color image. Of course you were restricted to what colors could be adjacent to each other.

 

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And here is Flight Simulator II correctly rendered exactly as it was conceived, out of a stock 1983 800 (end-of-U.S. production), on composite output. Notice the peculiar difference on the artificial horizon between Disk-based and Cartridge-based version... I bet no-one has seen this... ?

 I didn't know there was a difference between the cart and the disk version - in terms of the colors and flipped Artificial Horizon. Since I do most all of my classic computing on emulators I just flicked the artifact slider to what looked good.

 

Now. As an Apple User I thought I'd slip in a few more screenies of artifacting on that system. Though generated with an emulator I compared against various technologies in real hardware. Like a 1084s and NTSC and Composite Color display. The visible differences between the methods are mostly accurate.

 

 

 

 

What I find impressive is just how similar artifacting is on the two architectures. And just how sharp images can be if you match your display and source just right. And though the screenies are emulated. Their differences are clearly visible as on my actual hardware. 1084s, color tv, RGB, Amdek 300. Sadly my shitty samsung t260hd won't display colors from the Apple II.

Edited March 6, 2020 by Keatah

[Keatah]

37 minutes ago, Mclaneinc said:

I like the emulator for the artifacting, I can colour correct it to something I like best and if you are using composite there's a good chance you will get the bars on real hardware where Altirra remains pretty clean even when in artifact mode.

 

Absolutely. It's situations like that which make emulation the superior choice. But a true hobbyist will likely have both real and emulated hardware at their disposal.

 

Beauty part of emulating is ease and consistency of color adjustments. And the ability to make a desktop icon for a certain setup/calibration.

[jamm]

1 hour ago, Mclaneinc said:

I like the emulator for the artifacting, I can colour correct it to something I like best and if you are using composite there's a good chance you will get the bars on real hardware where Altirra remains pretty clean even when in artifact mode.

I tried to get the right blue-and-brown artifacting colors in Flight Simulator on Altirra (as shown above by @Keatah and @Faicuai), but all I could get were the 'wrong' green-and-purple versions.  Does anyone know why, or have a working configuration?

 

[phaeron]

5 hours ago, jamm said:

I tried to get the right blue-and-brown artifacting colors in Flight Simulator on Altirra (as shown above by @Keatah and @Faicuai), but all I could get were the 'wrong' green-and-purple versions.  Does anyone know why, or have a working configuration?

View > Adjust Colors > Artifacting Phase, adjust to around 170d. Different Atari models produce different artifacting colors.

 

[jamm]

50 minutes ago, phaeron said:

View > Adjust Colors > Artifacting Phase, adjust to around 170d. Different Atari models produce different artifacting colors.

 

Perfect - thank you!

[zzip]

On 3/5/2020 at 12:43 PM, bfollowell said:

Yeah, I know some software publishers back in the day used artifacting to their advantage, to get colors or more colors, but usually it was a side effect and the image was never really intended to look that way, even though we've all grown accustomed to it. It's been decades since I played Ultima, but I'm mainly thinking of the original. Wasn't it pretty much a monochrome game anyway? Not sure about IV. I never made it past III.

 

They were all written on Apple II, which used a system very similar to artifacting to produce colors.   So when ported to Atari, they used artifacting to the same effect.   No they weren't really intended to be monochrome.

[+Stephen]

So - there is a GTIA only core available for VBXE that gets rid of many of the extra features.  Would it be possible (since we don't have the blitter and other stuff) to add artifacting to that maybe?

[Rybags]

For that core I imagine all sorts of things could be added.

But I'm not sure any firmware type has active development or support.

[+Nezgar]

On 3/6/2020 at 11:05 AM, Faicuai said:

And here is Flight Simulator II correctly rendered exactly as it was conceived, out of a stock 1983 800 (end-of-U.S. production), on composite output. Notice the peculiar difference on the artificial horizon between Disk-based and Cartridge-based version... I bet no-one has seen this... 

Heh, because the disk version was written on an 800, so it will look correct on that... and the XE cart was probably modified/"corrected" when Atari Corp noticed the colours were backwards on XE machines. And of course that cart will in turn look incorrect when used on an 800...

[flashjazzcat]

9 hours ago, Stephen said:

So - there is a GTIA only core available for VBXE that gets rid of many of the extra features.

The main purpose of the GTIA core appears to be PAL blending (to support APAC mode and others). And yet even with the ability to select that core, I still end up just switching over to the legacy video output whenever I want to see PAL blending, etc. It's easy enough. And I never want to see artifacting.

 

I don't think there's a great deal of space left even in the GTIA core, since it necessitated some line buffering, IIRC.

[Rybags]

Yep, generally if something's got PAL blending then it'll be 80 pixel video, sometimes 160.  So the loss of video quality is much less of an issue by switching to legacy output.

 

Just looking at the core in the Zip file, the GTIA one packs down to about half the FX core size so likely there's plenty of room left.

For line buffering - that'd have to use RAM internal to the AVR wouldn't it?

[flashjazzcat]

Yes: when I talk about space, I don't necessarily mean code footprint, but utilisation of the FPGA resources. But I have no special knowledge here: perhaps there's plenty of space and I just remembered wrongly.

 

[Rybags]

A quick look at Altera EP1K50 - seems to have 40960 data bits = 5K.

I suppose that could be a scarce resource if 2 scanlines need to be buffered, and we're probably looking at 24 bits of colourspace info per pixel, and possibly keeping track of 352 or more per scanline.

And that AVR is from the current Lotharek version (or at least the pic on his site).  Earlier revisions probably used a less powerful AVR.

[leech]

5 hours ago, flashjazzcat said:

Yes: when I talk about space, I don't necessarily mean code footprint, but utilisation of the FPGA resources. But I have no special knowledge here: perhaps there's plenty of space and I just remembered wrongly.

 

Yeah, I would just hope for any old stuff and new would look correctly going out of the VBXE port.  I thought when you modded mine the normal 5pin DIN still worked, but either I screwed it up, or am remembering it wrong (not that I've done any additional work to your wonderful upgrade job.)

I am finding that Ultima IV is one of those that I think look great on my 2 800s, but the blue is red and the green is blue on the Stock 130XE.  Granted, that might be due to different versions of Ultima IV, as for some weird reason I can't get my SDrive Max to load on the 130XE, but works fine on the 800s, yet can't get the SIO2PC/USB working on the 800, but it does on the 130XE...

I do have to comment that it's hilarious to see the 130XE on top of an 800...

 

I actually think one of my 800s are a CTIA one, but I can't seem to find a BASIC ATR file, though now that I've cleared a bunch of crap off my Ultimate Cart, I'll see if that'll let it read it (it seemed to randomly work before).

[drac030]

You guys seem to need a separate device, some sort of Video Crippler, which inserted between the Supervideo or RGB output and a monitor would convert the high quality signal back into the joys of the Composite Video or old antenna TV signal. The device should have some switch to select modes of operation, like PAL/NTSC CV and PAL/NTSC antenna. Lotharek, if you are reading this, when you will have made loads of money from that, please remember that the idea was mine

Edited March 8, 2020 by drac030

[phaeron]

I don't think it's correct to characterize artifacting as poor quality output. It was deliberately used by several well-known games, and recognized as a legitimately useful technique even by Atari (it is described in De Re Atari Appendix D). Heck, even a couple of games used pattern artifacting in PAL, and that is very much harder to use effectively.

 

It wouldn't make sense to combine PAL line blending with NTSC artifacting given that they are exclusive to each video system. PAL line blending is considerably simpler, however, as it really only requires a delay line and some averaging logic. An on-chip RGB delay line is one way to do this, but there are potentially cheaper ways, such as storing the hue values in a delay line in external RAM and cycling the DAC twice per Atari pixel to get the two values for blending.

 

NTSC artifacting is actually not very easy to do well and would probably take more chip resources than PAL line blending. Basic on/off pattern recognition works and is reasonably cheap, but has a couple of downsides. One is that it is not overall luminance preserving and tends to lighten or darken some shapes, making colored shapes look too thin and filling in corners of text characters:

 

 

It also can't reproduce color fringing effects very well, which are responsible for more subtle effects like the three colors on the top of the castle wall in Ultima IV:

 

 

In my experience, a good quality NTSC filter can't be done at 320 pixel rate (7MHz); it needs to pixel double up to 640 rate (14MHz).

 

The cheapest hardware implementation I can think of that could handle this would be a shift register holding the history of the last 4-7 hires pixels translated through one wide-input, narrow-output lookup table to drive a second narrow-input, wide-lookup table with signed RGB values to add to the normal RGB output. This would be cutting some corners, but would probably produce passable output. A full blown filter like I use in Altirra would be fairly expensive, it either needs a large amount of shift and multiply/add elements or large precomputed lookup tables.

 

 

[leech]

I am guessing this is PAL vs NTSC version...

 

[flashjazzcat]

Doesn't the hardware required to create these authentic effects already exist in every A8 with a composite pin on the monitor jack? Or am I somehow missing the point?

 

 

[jamm]

3 minutes ago, flashjazzcat said:

Doesn't the hardware required to create these authentic effects already exist in every A8 with a composite pin on the monitor jack? Or am I somehow missing the point?

 

 

I think the idea is that you could get good, clean video and on top of that simulate the color artifacting effects of NTSC composite.  So you'd get the desirable "extra" colors without the undesirable noise.  Basically what you get in something like Altirra's emulation.

Edited March 8, 2020 by jamm

[flashjazzcat]

Right. So: UAV?

 

[jamm]

Yes, but you currently have to feed UAV output into a composite input (I haven't done it myself, but I assume that works).  If it were done in firmware, then you'd get the effect regardless of signal path, and could potentially turn it off and on at will.  Given the discussion, though, it sounds like the amount of effort involved would be pretty significant and the number of titles that really would benefit would be small.

[+Stephen]

2 minutes ago, flashjazzcat said:

Right. So: UAV?

 

Which coincidentally, also allows for phase adjustments (i.e., 800 vs 130XE artifacting colours).

[flashjazzcat]

17 minutes ago, jamm said:

Yes, but you currently have to feed UAV output into a composite input (I haven't done it myself, but I assume that works).

Yes: it works. A/V inputs are still extremely common on TVs (especially those to which it is possible to connect a VBXE A8), so one can leave both video outputs connected to the display device and switch between them with the remote control. I do exactly that here... it does not get much easier than that.

 

Edited March 8, 2020 by flashjazzcat