TV Simulation

[eshu]

I think Stella's filters are a poor approximation of what the video from a 2600 actually looks like on a TV. These filters that just screw up the image in random ways are quite obsolete now that we have Blargg's NTSC Libraries, which faithfully simulate the artifacts of NTSC signals.

 

I'm so addicted to these filters that I can't seem to play the pixel-perfect crispy versions anymore. Hopefully the next version of Stella will have actual NTSC emulation.

 

That library does look pretty sweet, but I think it is based around processing a single image at a time - so it wouldn't do anything for the phospher effect that is often used on the VCS. It would be great if someone could integrate it with the work that has already been done, but I don't think that would be a particularly easy task.

 

I haven't seen a VCS on a CRT for quite a while but I didn't think the new functions in Stella made that bad an approximation if it - I definitely think it's a lot better than just having the alt-p option for phospher effect which I think pretty much just merges two frames.

Edited November 3, 2009 by eshu

[tokumaru]

OK, let's continue the discussion here, bofore we get too off-topic in the Castlevania thread.

 

I have an implementation of Blargg's filters for Stella already.

That's great! I hope everything works out well. Looking forward to the next release, even if it takes a while.

 

That library does look pretty sweet, but I think it is based around processing a single image at a time - so it wouldn't do anything for the phospher effect that is often used on the VCS.

That's true. Something else would have to be done about that. It will probably stay like it is now though, consecutive frames will be blended, but each one will have been previously processed by the NTSC filter. I don't have many VCS games, and it's been a while since I played something that heavily relied on flickering, so I can't say how bad it actually looks on a TV, but it's probably safe to say that the frames don't blend as cleanly as in emulators.

 

I haven't seen a VCS on a CRT for quite a while but I didn't think the new functions in Stella made that bad an approximation if it

The problem is that they are subjective approximations. For example, we know the images were blurry, so a generic blurring algorithm is used. That blurring, however, is not the same kind that results from NTSC encoding, it's just a generic blur. The same goes for color bleed, dot crawl, noise... there is a reason why all those things exist, and they will only look authentic if what causes them is emulated, and this is why the NTSC filters are so great.

 

I understand that for players the NTSC filter may look like nothing more than a novelty, but for developers it is very important. Some times there are certain color combinations that don't work well (causing strange patterns when used close to each other), dithering patterns can look weird, small details might not stand out as much as desired... Real NTSC emulation lets you catch those problems, while the fake filters don't.

[+Random Terrain]

What do you call the things that look like shadows next to objects on the left and right sides? And right next to a shadow, the color is often brighter.

[eshu]

I have an implementation of Blargg's filters for Stella already.

That's great! I hope everything works out well. Looking forward to the next release, even if it takes a while.

 

Indeed excelent news!!

 

The problem is that they are subjective approximations. For example, we know the images were blurry, so a generic blurring algorithm is used. That blurring, however, is not the same kind that results from NTSC encoding, it's just a generic blur. The same goes for color bleed, dot crawl, noise... there is a reason why all those things exist, and they will only look authentic if what causes them is emulated, and this is why the NTSC filters are so great.

 

I do understand this, I just hadn't dared to dream anything as good as the Blargg filters would be coming any time soon.

 

I understand that for players the NTSC filter may look like nothing more than a novelty, but for developers it is very important. Some times there are certain color combinations that don't work well (causing strange patterns when used close to each other), dithering patterns can look weird, small details might not stand out as much as desired... Real NTSC emulation lets you catch those problems, while the fake filters don't.

 

That's exactly why I thought this topic would be ok on the programming forum.

 

It's not just about avoiding problems - you can also take advantage of the way the image is processed to gain the appearence of extra colours, less jagged graphics etc..

 

It's not relevant to the 2600 because of the horizontal resolution, but one of the most impressive effects achieved this way is artifacting: http://www.atarimagazines.com/compute/issue25/033_1_GRAPHICS_8_IN_FOUR_COLORS_USING_ARTIFACTS.php

 

What do you call the things that look like shadows next to objects on the left and right sides? And right next to a shadow, the color is often brighter.

 

I'm not sure, but I think it might be a form of "color bleed": http://blargg.fileave.com/ntsc-parameters/

Edited November 4, 2009 by eshu

[tokumaru]

It's not just about avoiding problems - you can also take advantage of the way the image is processed to gain the appearence of extra colours, less jagged graphics etc..

Exactly.

 

It's not relevant to the 2600 because of the horizontal resolution, but one of the most impressive effects achieved this way is artifacting: http://www.atarimagazines.com/compute/issue25/033_1_GRAPHICS_8_IN_FOUR_COLORS_USING_ARTIFACTS.php

 

This is similar to what's possible with CGA video cards using composite video: http://en.wikipedia.org/wiki/Color_Graphics_Adapter#Special_effects_on_composite_color_monitors

 

I believe DosBox, the DOS emulator, can emulate these artifacts. I don't think many games used this "feature" though.