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The magic of NTSC's artifacting...


Faicuai

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...You will need plenty of bandwidth on your video-path, but you will be surprised with the final results...

 

Here's latest FLOP-magazine image (included on the release), shown on NTSC from Y/C (sVideo) output and then the exact same image just switching to Composite output (click / touch the images to view at proper size):

 

Y/C (sVideo):

13DA19E8-23F3-4857-AB98-4459F95097A0.thumb.jpeg.cf72ef4b25efbb190b9288610bc22112.jpeg

 

Composite:

3598F858-B79D-4A70-B22D-A846E7ED10E3.thumb.jpeg.604a4ca0b82e9b6d7e10bbbb2ae5edc3.jpeg

 

Note that both inputs have been carefully calibrated for vis-a-vis response of luminance, chrominance, black-point, white-points and Gamma (subjectively). In other words, an ACP rendering appear virtually identical (on those dimensions) on both interfaces. I would need to test RF output but need a high-quality de-modulator for this.

 

And the exact same effect is seen on Avery's Video Player... wait until you see how your screen explodes with color when watching 60fps NTSC videos via Composite...

 

?

Edited by Faicuai
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This is likely the result of a cheap 2D chroma comb filter in the display that is switched out when S-Video is used, similarly to what some PAL displays use. It's intended to try to reduce types of demodulation artifacts at the cost of reducing vertical chroma resolution, so it isn't needed when Y/C are kept separate. You'll see different results with adaptive 2D or 3D comb filters.

 

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Well it's kinda gray zone on NTSC here. This image uses good old interleaving of luma and chroma lines. That's only supposed to work in PAL. Averaging of chroma from 2 consecutive lines is firm part of PAL color encoding. There is no need for that in NTSC though.

Modern TVs usually do chroma blending on composite regardless if it's NTSC or PAL. Some even do it on S-video, even if they shouldn't.

I was wondering if I should bother with fixing this image for NTSC by shifting the palette. In the end I did. So I'm happy it was worth it. Looks very true to the original.

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54 minutes ago, phaeron said:

This is likely the result of a cheap 2D chroma comb filter in the display that is switched out when S-Video is used, similarly to what some PAL displays use. It's intended to try to reduce types of demodulation artifacts at the cost of reducing vertical chroma resolution, so it isn't needed when Y/C are kept separate. You'll see different results with adaptive 2D or 3D comb filters.

 

There is no such 2D comb-filter in my display.

 

In fact, there is no filter or analog-signal support (other than VGA) of any kind, whatsoever.

 

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23 minutes ago, Faicuai said:

There is no such 2D comb-filter in my display.

 

In fact, there is no filter or analog-signal support (other than VGA) of any kind, whatsoever.

In that case, it'd be in the composite/S-Video to VGA converter you're using.

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20 minutes ago, phaeron said:

In that case, it'd be in the composite/S-Video to VGA converter you're using.

Well, not either:

 

"High Quality, Super Adaptive 2D Y/C Comb separation"

"High performance, 10-bit Multi-standard Video decoder"

"Auto CUE-C, Chroma Upsampling Error detection and correction"

"12-bit Ditgital-to-Analog converters (DACs)"

 

DVDO iScan HD/+. And it yields on the same results on its bigger brother, the iScan VP50-Pro.

 

And output is not being delivered on VGA interface. It is being delivered on DVI.

 

That's what it really is. The bottom-line is that Composite here looks a helluva better than SVideo Y/C, for this type of image.

 

 

 

Edited by Faicuai
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11 minutes ago, Faicuai said:

"High Quality, Super Adaptive 2D Y/C Comb separation"

 

This is the comb filter, they just don't use the word "filter". In your case, it is an adaptive filter, but it's not typically documented how the adaptive logic responds to a signal like the Atari's where the chroma doesn't invert phase on each line, which reduces the effectiveness of such filters.

 

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8 minutes ago, phaeron said:

 

This is the comb filter, they just don't use the word "filter". In your case, it is an adaptive filter, but it's not typically documented how the adaptive logic responds to a signal like the Atari's where the chroma doesn't invert phase on each line, which reduces the effectiveness of such filters.

 

I noticed the above phenomena quite a long time ago.... and tested on not just my video-processors, but my LCD TVs (which have their own analog-video decoding stage).

 

The results is that My Sony Bravia large-screen and lower-cost Vizio's they all exhibit the same phenomena, with this particular type of image. Denser, more intense color response when feeding these images through Composite....

 

I do need to check with the video decode of my Sony DVCAM DSR-11 deck (with its own analog-to-digital conversion) and see how it handles it... I presume will also confirm the same as Sony Bravia.

 

 

Edited by Faicuai
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Imho it makes perfect sense. At least in PAL. Chroma averaging in PAL is done to cancel phase shifts cause by HF signal bounces. So it's mainly done for HF signal.

But composite input is usually connected just after the HF tuner, before all chroma separation. So chroma averaging affects it too. S-video is fed after chroma separation, so it's not affected.

NTSC only TV wouldn't even have the averaging hardware (especially the 1 line delay loop). But modern TVs are universal, they have to handle PAL, so they have the hardware (even if it's more likely something digital these days). And it might actually help with chroma noise.

 

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2 hours ago, R0ger said:

(...)

I was wondering if I should bother with fixing this image for NTSC by shifting the palette. In the end I did. So I'm happy it was worth it. Looks very true to the original.

 

To your eyes, which of the two samples posted here look truer to the original?

 

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The second one. There is clearly strong leak of chroma only lines to luma only lines. And that's what this GFX mode counts on.

On the first one there is very little color. There actually should be none, and I've seen it on some PAL TVs when using S-video. The difference look quite like if you turn on PAL artifacting in Altirra on and off. And that's what's actually happening in my opinion, even if it's NTSC.

 

The first one has more of 50% checkerboard pattern visible, but that's matter of exposure. I use that to decrease percepted flickering.

And the second one has that typical 'chroma noise' .. that sub-pixel chroma spikes leaking into luma, typical for composite and HF.

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19 minutes ago, R0ger said:

The source picture is here:

 

terry2.png.4cb7fb669829915a09f563f609acc9a7.png

 

And Altirra does very good in how it looks on PAL TV (with PAL artifacting set to high, frame blending on):

 

terry.thumb.png.25fdf2bb8c5fc6ddfdd7d53724ddf8d5.png

Wow! Remarkable!!!

 

Yes, my composite sample is coming very close the real thing (setting aside brightness). Even the greenish tones are there! Also, tight color calibration on NTSC (Atari) will be required to render them well.

 

And I asked because, when observing this in the past, on multiple images, it became crystal clear to me that images were not only enhanced.... but resulting colors were VERY real!

 

So, at this point, I have concluded that, if we can't extract something like my second (composite) sample, we will not enjoy these images as originally intended.

 

Cheers!

 

 

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1 hour ago, R0ger said:

As I said, I was under impression they can't work on NTSC at all. So good for you I guess ?

Gee, these cheap 2D chroma comb filters are killing me.... ??

 

But I must be honest and confess that I paid $90 bucks for it (and I know it is more expensive). One of the best deals I recall ever making...

 

535B6129-9156-4C7F-9371-D5914877F899.thumb.png.7c80c37a92ec4210002b38663c09e0b3.png

 

Cheers!

 

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10 hours ago, R0ger said:

As I said, I was under impression they can't work on NTSC at all. So good for you I guess ?

 

Myself and others on this forum -- who play in NTSC land -- have commented that the supposed "PAL ONLY Blending" is a myth. I've been saying it for years (probably more than ten years ago), with little or no response from anyone. I've also pointed out that I needed to use composite in order for it to work.

 

So, this is no new discovery/observation.

 

Edited by MrFish
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5 hours ago, MrFish said:

 

(...) I've been saying it for years (probably more than ten years ago), with little or no response from anyone. (...)

 

Too bad... Life's hard!

 

Reminds me of my color-calibration chanting... which sings how such a large group of people out-there are getting NTSC Atari colors WRONG on today's modern screens... (but life goes on, whether we cry or not...)

 

?

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1 hour ago, MrFish said:

It's no problem for me, just for those who sit there staring at the images with an NTSC S-Vid hookup, wishing the colors weren't so faint.

 

Then you can now rejoice that your voice has been heard or, at least, confirmed with some decent evidence.

 

Whoever does not listen now is most likely living in La-La-Land.

Edited by Faicuai
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3 minutes ago, MrFish said:

If you haven't already, something else you might want to look at with your composite connection is Project-M v2.0. Big payoff.

 

Project-M v2.0 (NTSC).xex 60.49 kB · 0 downloads

 

 

 

Already looked at it... ??

 

That was a HUGE eye opener... right after watching the 60fps Video Player through composite...

 

Both cases like DAY-and-NIGHT compared to the pale and desaturated sVideo rendition...

Edited by Faicuai
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On 7/3/2020 at 2:43 PM, phaeron said:

This is likely the result of a cheap 2D chroma comb filter in the display that is switched out when S-Video is used, similarly to what some PAL displays use. It's intended to try to reduce types of demodulation artifacts at the cost of reducing vertical chroma resolution, so it isn't needed when Y/C are kept separate. You'll see different results with adaptive 2D or 3D comb filters.

 

Would it be possible to add an NTSC option for this in Altirra, seeing it's possible on real hardware?

 

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1 hour ago, MrFish said:

 

Would it be possible to add an NTSC option for this in Altirra, seeing it's possible on real hardware?

 

Second that one, as I cant' reproduce what I am seeing on real HW (no matter what display-device I choose for it).

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1 hour ago, Faicuai said:

Second that one, as I cant' reproduce what I am seeing on real HW (no matter what display-device I choose for it).

Using low PAL artifacting with NTSC palette should work fine. High NTSC and PAL artifacting introduce luma to chroma aliasing (false colors on B&W hires images), which is quite different on PAL and NTSC, but for lowres, high PAL artifacting should also work fine, and get you very close.

But yeah, having extra option for chroma blend would be nice.

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41 minutes ago, R0ger said:

Using low PAL artifacting with NTSC palette should work fine. High NTSC and PAL artifacting introduce luma to chroma aliasing (false colors on B&W hires images), which is quite different on PAL and NTSC, but for lowres, high PAL artifacting should also work fine, and get you very close.

But yeah, having extra option for chroma blend would be nice.

It may sound ironic... but this whole thread got me to re-think this issue entirely... especially after reading your explanations (and Fish's) and reasoning over it.

 

Would it be that (what we are seeing happening with these images through NTSC-composite) the result of Artifacting or, instead, chroma / PAL-like blending... or a actually a cocktail of both? As for my own position, I am no longer sure it is artifacting...

 

Funny, I may have to probably re-name the title of this thread! 

 

??

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