135 replies to this topic

[danwinslow]

Me too, I want to buy a couple more.

[candle]

sorry guys, i'm able to do 5 more boards (in right circumstances (ie someone buying altera ep1k50tc144-3n for me - in digikey, or avnet in states) and thats it
then only thing you really can do is to wait (a bit indefinitly ) for v3

[flashjazzcat]

That's too bad, but any of us with even ONE machine with a VBXE in it should count ourselves very lucky indeed.

A question: what are the hardware differences (if any, apart from the oscillator, presumably) between the PAL and NTSC VBXEs?

[candle]

none
just frequency of crysta used differs, nothing else

[thgill]

Does the VBXE pass all the Atari video out to the RGB monitor or only VBXE specific code?

I guess I am wondering that with a VBXE installed would a RGB monitor be all you need to enjoy everything on the atari, old and new a like? Or still need to maintain a second display for non VBXE software.

Edited by thgill, Fri Jan 28, 2011 12:13 PM.

[flashjazzcat]

All video data - "stock" and VBXE-specific - goes through the RGB output. You'll only need a second display (and retain the original chroma/luma output jack) if you want to preserve one or two things VBXE doesn't emulate, like PAL colour blending (IIRC) and artifacting.

Edited by flashjazzcat, Fri Jan 28, 2011 12:18 PM.

[Rybags]

Your existing video still works as normal, but doesn't show any VBXE generated stuff.

The RGB from VBXE displays all video, VBXE also does GTIA emulation and merges with any VBXE specific stuff for video display that goes to RGB.
So you need an RGB monitor or a device which converts the RGB to S-Video or whatever type you want to use if you don't have a monitor that can do RGB at 16 KHz.

[thgill]

artifacting.

School me on this artifacting idea. I am very new to the A8 platform (picking up my first 800XL tonite!) and I am not 100% sure I understand this completely.

From what I have read, artifacting is pretty much just a trick used to appear to generate more colors on screen via RF or composite video output than the system can actually generate. I am guessing due to the rather crap nature of RF and composite since luminance and chrominance are combined into the video signal and with that there tends to be some bleeding/blending between pixels.

With that said, I am also supposing that all svideo mods also don't display artifacting?

Is the lack of artifacting even a really big issue? Did a lot of developers really program with it in mind? I know Choplifter gets mentioned as suffering when artifacting isn't there as the colors are all jacked up.

[candle]

for ntsc system this is bigger issue (lack of it), on pal machines - colors got by artifacting looks like crap in the first place, so i don't think there is a single game that would use it (its just mine uneducated on that matter opinion and i might be wrong)
i'm pretty sure that pal artifacting is removed by s-video mods, but not pal color blending (they are interline effects, not interpixel) and works using another phenomena or system (pal) feature, thus pics like Albert Einstein logo in Numen looks washed out
this could be emulated within gtia-emu core (core concept is something you need to dig yourself in vbxe thread, as its beyond the scope of this one), but currently isn't

i have no real knowledge about artifacting on ntsc systems, but i do find ntsc ataris output unacteptable for modern displays (too blurry, colors inconsistent, etc) - but this is again limited to 2 units - 1200xl which has problems of its own, and 800xl
plus i never tryed artifacting games on these two - just powered them up and dislike what i saw

[phaeron]

Artifacting is color graphics produced by interpretation of high-frequency luma (brightness) signals as chroma (color). This is due to incomplete separation of luma and chroma, made more difficult by the video produced by this style of computer (lack of interlace and slightly different horizontal timing means that the chroma subcarrier doesn't invert between either scanlines or frames). On the Apple II, it was the only way to produce color, and when such games were ported to the Atari sometimes they just used Graphics 8 and kept the artifacting. It was also occasionally used to draw color bars next to 40 column text, such as in Pitstop II.

With NTSC, the dot clock by the Atari in hi-res mode is exactly twice the color subcarrier -- 7.16MHz. This means that an alternating pattern of on and off dots produces a color, and the opposite pattern produces the opposite color. Depending on the hardware, doing this with black and white pixels produces green/purple or blue/red. Other colors can be used for the alternation in which case the artifact color includes the source colors by vector sum. The interaction between luma and chroma also causes color fringing on sharp edges and intermediate colors to appear where sharp color contrasts occur; these are usually unwanted in any case.

Artifacting isn't as useful in PAL for two reasons. First, the PAL chroma subcarrier is faster than the NTSC subcarrier, 4.43MHz instead of 3.58MHz. A PAL color cycle is 5/4ths of a hires pixel instead of two hires pixels as on NTSC, and this means that more luma detail can be encoded and preserved. It also means that you can't get a stable color out of pixel patterns because the Atari's dot clock doesn't line up, so the best you can get is some ugly rainbows. Second, the PAL color subcarrier reverses direction on alternating scanlines and displays average chroma components on adjacent lines, partially canceling some of the chroma artifacts. From what I've seen in pictures, you can get some colored vertical lines with PAL artifacting, and that's about it -- nothing like the solid colors you can get on NTSC.

My emulator Altirra has four different modes for emulating artifacting, each with increasing cost. The cheapest is simple NTSC artifacting, which just consists of a 3-tap horizontal filter on luma to detect alternation patterns and to kick in the artifacting color. This doesn't give fringing artifacts, but it's simple and fast. The second cheapest is simple PAL artifacting, which emulates the chroma averaging in the TV receiver. The algorithm is trivial -- just a 50/50 blend on the RGB chroma -- but it requires a scanline worth of storage, which I presume is at a premium on an FPGA.

The other two modes Altirra supports are the high-artifacting modes, which give fringing artifacts but are a lot more expensive. Both work by using digital filters that emulate the process of producing a 14MHz NTSC or 35.5MHz PAL signal and then separating it out again to produce 14MHz pixels (double hi-res). The NTSC algorithm is the cheaper of the two and uses three 24-tap filter banks with two phases each; the PAL algorithm I just added and is more costly as it requires 16 phases and a YCbCr-to-RGB conversion. The filter banks are large in order to avoid intermediate lookups and multiplies entirely (960K for the SSE2 specialization), but in a hardware implementation you'd probably want more arithmetic units and less ROM. In both cases, though, the output isn't as good as what you'd get from a good TV, partially because the algorithms could probably use some tuning and partially because the filter design prohibits non-linear elements.

[rdemming]

School me on this artifacting idea. I am very new to the A8 platform (picking up my first 800XL tonite!) and I am not 100% sure I understand this completely.

Others already have given a good explanation. But to see PAL artifacting read my "article" that compares VBXE output with composite and s-video output. Watch the pictures of Amaurote and SysInfo. You will see that the composite video output has artifacting colors while the VBXE RGB output is pure black/white.

Robert

Edited by rdemming, Mon Jan 31, 2011 3:23 AM.

[thgill]

Others already have given a good explanation. But to see PAL artifacting read my "article" that compares VBXE output with composite and s-video output. Watch the pictures of Amaurote and SysInfo. You will see that the composite video output has artifacting colors while the VBXE RGB output is pure black/white.

Robert

Very good comparison photos.

So its appears that generally speaking, with a few exceptions, that artifacting doesn't enhance the color and picture quality enough to offset the general sharpness and overall better readability that comes with both RGB or luma/chroma output. I guess in some situations artifacting would be beneficial, but in most it would appear to be a hindrance.

[flashjazzcat]

In those particular situations where you really want purple and green banding ruining your monochrome graphics, artifacting is just the best!

[enito]

Hi,

you still candle have in stock some vbxe2 in stock? im intersed in one..

let me know, greets!

[candle]

nothing last forever

[enito]

badly

but new parcel coming later? if yes, please include me ..thx!

[GlowingGhoul]

I'm also in for a couple of VBXE2's (or 3) when available again....

Edited by GlowingGhoul, Fri Jul 8, 2011 7:11 AM.

[candle]

v2 is not going to be continued - there is MOQ of 60pcs for Altera chips used there, and DAC is becoming hard to find
You need to wait (indefinitly as for now) for v3, or get together with 59 other members to reach MOQ for Altera

thats my reality - sorry

[enito]

ouch hope v3 coming...because is a nice work you made!!

i wait

[visionik]

Candle - is this the right Altera?

http://parts.digikey...50tc144-3n.html

[candle]

yes it is
but it usually get stuck on customs on my side, so importing it from the States makes it a bit uneeconomical (i've gone that route before)

[sloopy]

if you get enough orders in the US alone, maybe have someone in the US make them?

sloopy.

[Rybags]

Aren't all the resources needed to make your own available anyway ?

Although if a newer AVR is needed, then possibly the board layout has to change.

[orpheuswaking]

yes it is
but it usually get stuck on customs on my side, so importing it from the States makes it a bit uneeconomical (i've gone that route before)

And a train trip to Warsaw sucks

[candle]

car trip, because of where custom office is located
nevertheless it uterly sucks