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pepto
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 Posted: Sun Dec 15, 2002 9:06 am Post subject: C64 emulation |
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Hi there...
@ Trixter:
| Quote: | | "How good is the emulator?" Meaning, how exact are the graphics we are seeing? |
@ Sesse:
| Quote: | | Wouldn't C64 be one of the few platforms where there are almost _perfect_ emulators available? |
@ KithKanan:
| Quote: | | Yes and no. The graphics are almost spot on. |
I would vote "NO!" to emulators... Anybody is able to run the demos in an emulator himself, but not everybody has access to the real hardware and believe me, emulators look waaaay different than the original machines.
The worst part of c64-emulation (apart from the sound-emulation) is the emulation of the colors. The 16 colors of the c64 have been made for the YUV color-space of TV/video and most emulators replace this with a crappy "looks somehow like it" RGB-version. As MPEG2 also encodes into the YUV colorspace, it would be the best idea to capture the signal from a real c64.
c64 emulation became a lot better in the last year, as I did some research on the colors (see http://www.pepto.de/projects/colorvic/) and later John 'Graham' Selck joined me and after giving me a hand implemented them into CCS64 and Vice along with his PAL-emulation.
However... even if this looks a lot better than before, it's still far from perfect and I recently bought some capture-hardware (delivers uncompressed YUV via Firewire, although the driver doesn't work 100% yet) in order to get the emulated colors as close as possible in a second attempt. Unfortunately this will take some time as I have too much of a real-life nowadays... 
An important effect in the video-signal of the c64 is for example, that vertically in a c64 "frame", 2 lines share one color-signal line. So if you fill the screen with a brown line, a blue line, a brown line (and so on...), you'll get some sort of violet across the whole screen. c64 gfx-ppl make use of these techniques in order to get more colors onto the screen. This color-bleed also happens horizontally by about 4 pixels or something. This is what John 'Graham' Selck implemented into CCS64 and Vice with PAL-emulation, but this again is approximated an doesn't look exactly like on the real thing yet.
Another problem is, that the video-signal of the c64 isn't 100% valid PAL. In order to avoid flicker, the Commodore engineers implemented a trick into the signal which forces TV's and PAL-monitors (a lot of capture-devices have problems with this) to "draw" the two fields, which make a PAL frame, exactly above eachother (I think they do this by sending a line too much in one of the two fields). Usually one field draws the even lines of a PAL frame and the other one draws the odd lines. The c64 signal however only outputs one sort of lines (either even OR odd... I'm not sure) and the other ones stay black. This looks a lot better than it sounds, as the phosphor of CRT's shines bright enough to leave those black lines pretty much unnoticed. One c64 "frame" fits completely into one PAL field, so the 50 c64 "frames" a second fit pretty well into the tricked PAL video signal. This looks beautiful on TVs and PAL monitors, as you have real 50 FPS (in terms of the c64) and it's virtually flicker-free, but I'm not sure how you would represent this in a MPEG2 video-stream for the DVD.
It would flicker a lot and look stupid in scrollers, if you would just send one c64 "frame" in even lines of a PAL frame and the next c64 "frame" as the odd lines of the PAL frame. And I don't think you could play a lot of tricks with a MPEG2 stream.
Well... there are more problems if you want to capture demos like "Risen from Oblivion" by Crest on the c128, as they also use tweak-modes where they play tricks with the U and V part of the YUV signal in order to produce new colors. I'm not sure how easy it would be to capture those recent newskool demos and it's impossible yet to emulate them.
This should be enough for now... Trixter... Please contact me via eMail if you have questions... I have a little experience in capturing the signal of the c64 as good as possible... Telling you about what I experienced would probably help in preventing you from doing the same mistakes I did.
I think it is possible to capture c64 demos to a DVD in pretty decent quality, but I also think that this isn't very easy or possible in a short time-frame and it also needs careful planning, some investments, a little research and time...
Speaking of Amiga demos... This would also turn out to be more difficult than you might think. Recent kick-ass amiga-demos require PPC accelerator cards and OpenGL graphics cards and output VGA (like "Planet Potion" for example... some bad captures are available here and there on the net)... a lot of demos also require a 68060 CPU (etc)... Amiga-demos didn't stop at the vanilla A500 or A1200, even if this is what the oldskool demos used. (BTW... @z5/A.D.A.: You have a great site) And it would (apart from the oldskool-classics) be those demos (requiring expensive upgraded exotic Amigas) which would be interesting to have on DVD as only few ppl (the ones owning the original hardware) are able to enjoy those recent new-skool demos which are so great.
Besides... Doesn't A500's and A1200's use a similar PAL trick to that of the c64? I'm not sure...
Well... This should be enough for now... just my 2 pence... 
I think I will buy a copy of Mindcandy Volume 1 in the near future although I never owned a PeeCee in my life (they suck). The only PeeCee demos I know are "2nd reality", "the product" and "heaven seven"...
Maybe you should ask for extensive help from the c64 and Amiga demo-scene for producing additional DVD's as you don't seem to know THAT much about those parts of the scene (especially recent productions) and probably won't be able to get all the fancy hardware required, instead of doing a quick and dirty emulator-based approach of some old demos, that nobody would really be happy with...
Regards...
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Philip 'pepto' Timmermann |
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metamorphosis
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| Posted: Sun Dec 15, 2002 12:02 pm Post subject: |
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| Speaking on behalf of the MindCandy-buyers from Norway (and other Scandinavian countries), the best thing for Volume 2 would be to feature massive amounts of Amiga-stuff, some C64/Atari-stash and even more "eyecandy" (read: New PC-demos that look and sound *good* :) |
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Sesse
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| Posted: Sun Dec 15, 2002 12:10 pm Post subject: |
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| gloom wrote: | | Speaking on behalf of the MindCandy-buyers from Norway (and other Scandinavian countries), the best thing for Volume 2 would be to feature massive amounts of Amiga-stuff, some C64/Atari-stash and even more "eyecandy" (read: New PC-demos that look and sound *good* :) |
I don't really see why you should be entitled to speaking on behalf of anybody but yourself. :-) I partly agree with you, but I'd believe there are MindCandy-buyers in Norway who don't ;-) |
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metamorphosis
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| Posted: Sun Dec 15, 2002 12:23 pm Post subject: |
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| Sesse: I'm talking about the people who have bought the first one from us and actually gotten back to us with questions / feature-requests for the second one. So yes; I am entitled to imply that many norwegians want Amiga-stuff. :) |
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z5
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| Posted: Mon Dec 16, 2002 3:44 am Post subject: Re: C64 emulation |
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| pepto wrote: | Hi there...
Speaking of Amiga demos... This would also turn out to be more difficult than you might think. Recent kick-ass amiga-demos require PPC accelerator cards and OpenGL graphics cards and output VGA (like "Planet Potion" for example... some bad captures are available here and there on the net)... a lot of demos also require a 68060 CPU (etc)... Amiga-demos didn't stop at the vanilla A500 or A1200, even if this is what the oldskool demos used. (BTW... @z5/A.D.A.: You have a great site) And it would (apart from the oldskool-classics) be those demos (requiring expensive upgraded exotic Amigas) which would be interesting to have on DVD as only few ppl (the ones owning the original hardware) are able to enjoy those recent new-skool demos which are so great.
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Hmm...interesting point here. Some people believe that the Amiga scene stopped at 1994-95 but i don't agree at all. So indeed, an 68060 would be crucial for the newer demos. An intro like Gift/Potion sure is a classic (groundbreaking stuff on 68k) and would definately have it's place on a DVD. Same goes for demos like Lapsuus/Maturefurk, Concrete/Ephidrena, The castle/Loonies, Perfect Circle/TBL..., maybe even a 4k by Ephidrena... They are as classic as Nine fingers, State of the art, ... were for the oldskool time (in my humble opinion ofcourse). And indeed, it would really be something really special if ppc releases like Planet Potion/Potion were on the DVD. This would indeed add a lot of value to producing an Amiga DVD because not a lot of people have seen this intro.
z5/A.D.A. |
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Trixter
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| Posted: Mon Dec 16, 2002 7:40 am Post subject: Re: C64 emulation |
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| pepto wrote: | Another problem is, that the video-signal of the c64 isn't 100% valid PAL. In order to avoid flicker, the Commodore engineers implemented a trick into the signal which forces TV's and PAL-monitors (a lot of capture-devices have problems with this) to "draw" the two fields, which make a PAL frame, exactly above eachother (I think they do this by sending a line too much in one of the two fields). Usually one field draws the even lines of a PAL frame and the other one draws the odd lines. The c64 signal however only outputs one sort of lines (either even OR odd... I'm not sure) and the other ones stay black. This looks a lot better than it sounds, as the phosphor of CRT's shines bright enough to leave those black lines pretty much unnoticed. One c64 "frame" fits completely into one PAL field, so the 50 c64 "frames" a second fit pretty well into the tricked PAL video signal. This looks beautiful on TVs and PAL monitors, as you have real 50 FPS (in terms of the c64) and it's virtually flicker-free, but I'm not sure how you would represent this in a MPEG2 video-stream for the DVD.
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As written, this doesn't make sense; maybe you meant to write something else. If an entire field is black, the demo flickers like hell and will run at 25fps maximum. But hopefully I'm misunderstanding you.
Please please contact me at trixter@oldskool.org -- Your message above has been extremely helpful and I'd like to go over some things with you. One thing you'll be relieved to hear is that my capture hardware captures 4:2:2 YUV so that won't be a problem  |
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Black Monk
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| Posted: Mon Dec 16, 2002 11:47 am Post subject: |
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http://www.hardsid.com/
For C64 emulation (if you went emulation versus the original hardware, which it doesn't sound like you are anyway) couldn't you use something like that to "solve" the sound quality, at least?
Just wonderin'. |
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Guest
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| Posted: Mon Dec 16, 2002 11:47 am Post subject: Re: C64 emulation |
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| Trixter wrote: |
As written, this doesn't make sense; maybe you meant to write something else. If an entire field is black, the demo flickers like hell and will run at 25fps maximum. But hopefully I'm misunderstanding you.
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Hook up your C64 to a TV some time and look closely. What the C64 does is send two "even" fields or two "odd" fields (I forget which) as one "frame" to the TV instead of one field of even scanlines and one field of odd scanlines. The TV traces over the same set of half of the scanlines, at the full 60hz, for a very flicker-free effect (but with some scanlines never drawn, resulting in black between every drawn line, masked somewhat by the blurriness of older TVs). Not just the C64 but plenty of other old video game systems draw this way.
No video capture card supports this properly, but I can still watch my C64 alright because I use DScaler as my TV viewing program and it has a "deinterlace" mode called "old game" that seems to interpret the frames the right way. |
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Trixter
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| Posted: Mon Dec 16, 2002 12:25 pm Post subject: |
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I have an NTSC C64 right now -- will it exhibit the same issue? (If so, I am dying to try this, please confirm...)
So if the same field is output twice, instead of the odd field output a half-pixel shifted down (which is what the normal signal looks like), then all I have to do to solve the problem is throw one field away -- but of course this will bring the maximum framerate of the C64 down to 25fps.
IS a PAL C64's maximum framerate 25fps? If so, then the signal makes perfect sense -- doubling-up the even field is what I would do, even. But if it's not, then I need a 50Hz/60Hz program to test this -- anyone got any quick BASIC program I could type in that would exhibit 50Hz/60Hz motion so I can test with my capture hardware? |
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Guest
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| Posted: Mon Dec 16, 2002 1:35 pm Post subject: |
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| Trixter wrote: | I have an NTSC C64 right now -- will it exhibit the same issue? (If so, I am dying to try this, please confirm...)
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I'm pretty sure NTSC C64 does the same thing. I also think you misunderstand. When it sends the TV signal two of the "same" field, I don't mean that they are identical. Essentially an NTSC C64 runs in a 320x240x60hz mode, but instead of alternating between drawing a field of even scanlines and then a field of odd scanlines it draws a field of even scanlines... and then draws another field of even scanlines...
Your video capture card recieves this signal and says "this can't be right" and puts the two fields of "even" scanlines together into a frame as if they were a normal frame composed of "even" and "odd" fields, which is why a C64 and other old video game systems don't look quite right when either bobbed OR weaved and DScaler includes another "old game" mode that presumably just interprets the captured video as 640x240x60hz, like that hypothetical divx file you were mentioning on pouet that you thought would take a 2ghz P4 to decode. |
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pepto
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| Posted: Mon Dec 16, 2002 2:55 pm Post subject: Re: c64 emulation |
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Hi again...
@ Trixter:
| Quote: | | But hopefully I'm misunderstanding you. |
Unfortunately you do...
| Quote: | | One thing you'll be relieved to hear is that my capture hardware captures 4:2:2 YUV so that won't be a problem |
This is good news... I think MPEG2 does 4:2:0 though IIRC... but better too much precision, than too little... 
| Quote: | | I'd like to go over some things with you. |
I'll eMail you either in the next few days or after x-mas... Damn... I wish I wouldn't be so busy all the time...  Please be a little patient with me...
| Quote: | | IS a PAL C64's maximum framerate 25fps? |
No... The PAL C64 has a maximum framerate of 50fps.
As DScale user already tried to explain... The signal consists of 2 odd fields (if both are odd or both are even isn't known exactly... but it's only one kind of them) in a PAL frame instead of 1 even and 1 odd... BUT... they aren't the same... every 1/50th of a second a new PAL field gets drawn from a c64 "frame" to the exact same line-locations as any PAL field coming from the c64... so every "2nd" line of the PAL frame (according to the official PAL standard) remains black as no field ever draws there... the other lines get populated with new content every 1/50th second...
Some ppl refer to this as "progressive half vertical resolution PAL"... BTW: If somebody reads this and is able to point me to official specs or at least a real name for this pseudo-standard or anything about it on the net, I would appreciate it a lot...
On another note: Please don't use any of the late c64's with the cost-reduced 9V chips (like the 8580 SID), but prefer one with the 12V chips (like the 6581 SID) as the ones with the 9V chips have some signal leak somewhere and there are light vertical stripe artifacts all over the screen coming from the VIC-II AFAIK...
@ DScale user:
| Quote: | | I also think you misunderstand. |
Thanks for describing this is more detail... 
| Quote: | | Essentially an NTSC C64 runs in a 320x240x60hz mode. |
I wouldn't say this, as this would exclude the famous "border", which almost any demo uses... IIRC the main area in the center is 320x240 alone...
Regards...
--
Philip 'pepto' Timmermann |
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Guest
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| Posted: Mon Dec 16, 2002 3:30 pm Post subject: Re: c64 emulation |
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| pepto wrote: |
I wouldn't say this, as this would exclude the famous "border", which almost any demo uses... IIRC the main area in the center is 320x240 alone...
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The main area in the center is 320x200, thanks to the border area those 320x200 pixels are 1:1 height:width on NTSC.
On PAL... well... PAL has a smaller "main screen" area (compared to total screen height/width) and MUCH larger borders because the total res is something like 360 x 288 instead of 360 x 240 (I forget the exact width of the side borders) for NTSC. |
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Trixter
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| Posted: Mon Dec 16, 2002 11:19 pm Post subject: Re: c64 emulation |
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| pepto wrote: | On another note: Please don't use any of the late c64's with the cost-reduced 9V chips (like the 8580 SID), but prefer one with the 12V chips (like the 6581 SID) as the ones with the 9V chips have some signal leak somewhere and there are light vertical stripe artifacts all over the screen coming from the VIC-II AFAIK...
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How would I tell? Meaning, I don't own ANY PAL C64, so if I were buying one from some ebay person overseas, how could I tell them to check for me so I don't buy a cheaper later model? Just the classic brown case, or some better way?
BTW: Thanks to you both for your help. Reading the DScaler help file helped me understand what is going on, and I am confident I can deal with it (in fact, the output is EASIER to deal with than unraveling traditional interlaced footage). I am surprised at DScaler's method of dealing with it -- they essentially throw away half of the information/motion -- but then again I have never liked any form of deinterlacing since they all do that anyway. |
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Guest
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| Posted: Tue Dec 17, 2002 12:21 am Post subject: Re: c64 emulation |
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| Trixter wrote: | How would I tell? Meaning, I don't own ANY PAL C64, so if I were buying one from some ebay person overseas, how could I tell them to check for me so I don't buy a cheaper later model? Just the classic brown case, or some better way?
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Classic brown case is your best way. They switched over to the cost reduced hardware so soon after switching to the cream case that the odds of finding a non-cost-reduced cream case C64 are pretty low. The later revision of the SID that the cream case C64s usually have is considered inferior as well, often making samples nearly inaudible.
| Trixter wrote: | | I am surprised at DScaler's method of dealing with it -- they essentially throw away half of the information/motion -- but then again I have never liked any form of deinterlacing since they all do that anyway. |
The difference between "old game" and "even frame" or "odd frame" is that "old game" doesn't throw away half the motion. They don't mention this right out, but they say that "old game" works for "any frame rate, not just 25 or 30hz" which is a dead giveaway. Also, old game properly handles the 60hz flickering in Super Mario Bros when you lose super -- (looks like Mario is being drawn every other scanline in "weave", which is an incorrect rendering), so I know it correctly handles 60hz progressive half vertical resolution. |
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Sesse
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| Posted: Tue Dec 17, 2002 9:11 am Post subject: |
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| Huh, Super Mario Bros? Weren't we talking C64 here, or does NES do the same thing? :-) |
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