C64 / C128 Video on HDMI screen - improving image quality possible?

[TinkeringSteve]

Hello all,

I have dug out a Commodore C128 (mostly used in C64 mode) when making room in dad's garage, tried whether it still works. Lo and behold - yes! Inclunding all SID voices. PSU measures fine on both DC and AC voltages.

But my attempts to make this display adequately on my HDMI monitor were rather underwhelming.
I have tried 2 different S-Video (or SCART, in the other case) to HDMI upconverters.
So I am using the C and Y signals, not composite.

The first one has a true color image but cannot do 4:3. But it's not exatcly clear either.


The other one seems to be of older design, can do 4:3 but the color is totally out of whack.


I remember when I was a kid, I had a dedicated Commodore monitor, and although the memories are blurry, it seems like the image on that monitor was better than even the first one below. (not on TV via RF modulator, of course)

On the better of the 2 images, you can see a clear pattern of noise, perfectly, equidistantly repeated:

• alternating sections of generally brighter blue vertical bars, and darker bars
• the seams of the vertical bars are a thinner light blue stripe, which go pretty much perfectly
      through the center of what would be a 8-pixel column in the C64's resolution.
• superimposed on that is some more random seeming, higher resolution noise
• these noise patterns are static, as in, not moving in position or intensity
• more rarely, some random cyan pixel cloud of fruitflies buzzing around randomly will appear,
      in low density - if I move the cable around, or just unplug/replug the SVideo, it vanishes.
      I guess that one is the converter going nuts due to some noise that tickled something it in.

I wonder where these regular patterns come from.
I'd assume, not from the HDMI converter, but noise from the source itself?

I now saw that the cable has no shield.
Would using a cable with own shields for luminance and chrominance be a good idea?

I also read the luminance signal of the C64 is higher than the later defined S-Video standard.
On the scope it did seem roughly double as high than the spec'd 850 or so mV-pp.
Some people put a 330R resistor in series there - I wonder how that would ever create a defined signal...
I'm not exactly an expert, but I tried a pi-form resistor attenuator on the chroma signal at ~ 75 Ohm and -6dB - didn't do any good.
Although I'm not sure the problem is the chroma signal (on the first image! ). it looks like varying brightness to me, not color shift. The luma does not look too high in amplitude.

Has anyone ever gotten a more decent signal on a modern monitor, using one of those ubiquitous HDMI up-converters?

[Ian.M]

Do you have a HDMI converter that can take RGB input?  If so, you'll almost certainly do better buffering the C128's digital RGBI TTL level output signals, and combining them in a matrix to get normal 0.7V'ish 75R analog RGB.  That gets all the C128 chroma level and colorburst frequency and stability issues literally out of the picture. NTSC was bad enough from an accurate broadcast source carefully locked to an accurate master oscillator.  By the time you've generated it in an aging 8 bit computer, probably suffering from chroma oscillator drift, and  digitized it in a cheap HDMI converter that certainly doesn't have a high precision master oscillator its no wonder it looks like a dog's breakfast of moire patterns.

If you don't have any converter that can take analog RGB input, well the arcade community solved the IBM(ish) CGA (which is also TTL level RGBI) to HDMI problem a while back, and if you have a North American C128 its RGBI output is virtually indistinguishable from IBM CGA, so converter boards are readily available.  I'm fairly sure many of them work with RGBI with 50Hz, 625 line sync timings (i.e. PAL or SECAM compatible) if you have an European / rest of world version, but do check the specific board you order does!

[TinkeringSteve]

Hrm! Interesting. I associated that D-sub video port with "for 80 column mode only" for some reason. I remember that I successfully connected an EGA monitor the school was to throw in the bin.
It's PAL land here. Heh. Amazon has one of them CGA boards for around 20 bucks. I guess I might try that.

Is chroma oscillator drift something fixable? ( with reasonable effort )

[Ian.M]

Sorry for misleading you.  I hadn't realized the C128 video systems were such a mess until I delved into its service manual: http://zetaweb.org/web/manuals/C128%20Service%20Manual.pdf  You are correct, the VIC IIe video processor doesn't even output RGBI video, and those lines come from the VDC chip, that although it can do 40 column modes is exclusively used (officially) for the 80 column text 'business' mode.   

For the C64, there is at least one mod that *DOES* generate hardware RGBI video from a FPGA replacement for the VIC chip, but I suspect most users are reluctant to go down that road, for cost or originality reasons.  It could probably be ported to the C128 VIC IIe chip pinout, if you are as experienced with FPGAs as the original mod creator! 

I also found this: https://techwithdave.davevw.com/2019/05/rgb64.html namely 'shadowing' text written to the VIC screen on a 40 column text mode VDC screen.  However that's no help whatsoever for graphics modes or anything that bypasses the ROM routines it patches (i.e. all games).

I therefore regret that RGBI => HDMI video, while essential to be able to use the full capabilities of your C128 wont be any help with your original problem of crappy video in C64 compatible modes.   To resolve the dot crawl and moire pattern mess, you'd need the capability to either lock the C128 or the component video => HDMI converter to the other's clock. 

Fully genlocking a C128 would be an absolute nightmare, requiring extensive hardware mods to pick up various timing signals, and replacing the master crystal of the 8701 clock generator with a narrow range VCO, controlled to 'drift' the oscillator frequency until the VIC's line and frame sync signals are in phase with the external source then phase lock the oscillator and trim the dot clock phase, but if you can find a HDMI converter that accepts an external dot clock input, well the 8701's dot clock output is available on pin 6 of the expansion connector, so no hardware mods would be required.  You may still need an external PLL to get the 17.43447MHz dot clock (nom. PAL models) to a harmonically locked frequency within the range the converter will accept.   

C20 is the trimmer for the 8701's crystal.  You'll find it under the little hole in the lid of the separate screening can on the main board behind the modulator.  Careful trimming using a ceramic bladed^* trim tool may help improve compatibility with a particular TV or composite/component video to HDMI converter, though as the oscillator circuit isn't ovenised its still going to drift as the C128 warms up.

* The extra capacitance of a metal bladed screwdriver shifts the frequency and makes trimming a crystal a royal PITA.  You can use a plastic bladed trim tool but their blades are very weak and tend to break off in the trimmer.  Trim tools with a plastic shaft and a tiny low capacitance brass blade insert are readily available but their shaft is likely to be too thick for the hole in the lid of the screening can.  Therefore its worth paying the premium for a ceramic bladed trim tool then 'babying' it so you don't break or chip its blade. e.g. *NEVER* drop it, *NEVER* put it in a bag or draw with other metal tools without a cover over its blade, and *ALWAYS* check the trimmer isn't seized using an ordinary jewelers screwdriver before applying the ceramic trim tool.

[Bicurico]

My advice:

1) Keep your original unmodded C128 or sell it to collectors. Do not modify ir or replace IC´s, seeking to fix the video quality on modern monitors.

2) Buy a Commodore monitor (1084S-D2) that can handle both video outputs of a C128. This will cost you around 100-200 Euro/US$ depending on the state of the monitor and your luck. Prices are going up, so you may need to spend more money.

3) If you just seek to actually use a C64/C128 (in 40/80 columns mode, including CP/M) then by all means get a Raspberry Pi and install the amazing BMC64. This will give you all you need with 99.99% perfect emulation (not even sure why there is 0.01% missing). Buy CBM keyboard stickers (very cheap) and glue them on a dedicated USB keyboard. This is IMHO the cheapest way to get back to CBM computers.

4) Do NOT waste money in RGB Digital to RGB Analogue converter, plus Frequency Upscaler, plus RGB CRT monitor with VGA input. This will be more expensive than getting a propper CBM monitor and you will have ton of cables, bare PCB´s and two extra PSU´s on the desk. And in the end, the image quality is still not perfect...

Regards,
Vitor

[TinkeringSteve]

I wonder how, again, all those good ratings on these 20..50 bucks s-videro to HDMI converters on amazon came to be...
If all those things basically suck, just to different degrees.

But this thing here looks great (somewhereat 2/3 orso should be an image of it working)


Not currently available at my country's  Amazon, but alternate suggestions cost 100..200 bucks
Ok, I hadn't bargained for that order of magnitude when thinking how nice it would be of getting  this running again.

I have used VICE for ages, but rarely. It's not really the same
I doubt you can get commodore monitors that are still good? Actually, the only anything-CRT still looking good I saw in the past 10 years or so was a Trinitron made in the early 2000's or so.

[Bud]

The vertical stripes you are seeing us a fundamental C64 issue caused by internal leak of video clock into the luma and chroma lines inside the video (VIC) chip. Google for "lumafix" mod to reduce the stripes. Basically that mod takes the clock signal, inverts it and adds into the luma signal so most of the clock cancels out and a clearer image results.
I think if you do that your first image will be great since its looks sharp already.
The color pixel bursts may come from luma signal sharp amplitude transitions being interpreted by the color decoder in the TV or the converter as color. The reason being luma having wide bandwidth so part of the spectrum falls into the chroma channel and is decoded as color. The Y/C separation is not too good in Commodore so you get that cross contamination. You can try to reduce this effect by reducing amplitude of luma signal.

[TinkeringSteve]

Whoa, that sounds promising!

About the luma bleeding issue - would using two separate pieces of e.g. RG179 shielded cable for luma and chroma reduce this effect? (I have none here, or I'd already have tried it )

[Bud]

I do not think so. I am not familiar with C128 video output circuit but in C64 luma and chroma channels are connected at some point to mix and produce composite channel. It would be required to either break the connection ( which will kill the composite output) or redesign the video buffer to improve isolation between them.
You may get away with just dropping the luma amplitude (i am assuming you are using S-Video output), it is possible that the bleeding occurs inside your converter or TV   if the signal is too strong. You can also try to play with your TV settings, sometime reducing color saturation may be all it takes. Oversaturated colors are hard on the eyes anyways when playing games.

[Alex Eisenhut]

I heard good things about this one

https://www.retrotink.com/

[TinkeringSteve]

Looks interesting.
Apparently someting similar for ~ 1/2 price is at aliexpress the "retroscaler2x", supposedly als with zero lag.

I have meanwhile tried another box off amazon which cost around 50 eur: "Mcbazel ODV" it was called.
http://mcbazel.com/index.php/product/odv-composite-rca-s-video-ypbpr-to-hdmi-converter/
It has so far the best image of the 3 I've tried.
But that page claims it does line doubling... when I press the button it can make a weird distorted image thats double as normal, lol, but that is not what I imagine line doubling would be. Ok maybe the normal looking image IS line doubling and the distorted one not, I don't know a lot about how analog video works.
And btw. I'm using a TFT that I have set to either "leave as is" or scaling to the highest possible size without altering the aspect ratio.
The latter mode is what I ended up using with this box, so I get a filled screen - save for the sides because 4:3.
Otherwise what comes out of this box is tiny.

The vertical lines are still thre, of course. I saw one readily made "lumafix" PCb on ebay for ~ 15 bucks, that's ok, will have it in a couple weeks and then let's see. I hope it also fits in the C128 (wasn't there some shielding stuff there over the board...). Or I really need to dig in the basement to get out a C64 I presumably still have.

By far the worst being one of those square shaped metal boxes with SCART input of different pseudo brand names - that this guy here also rightly calls the worst It does 4:3 at least, but you've seen the totally discolored image in the 1st post.


I wasn't even aware of image lag, or problems when content is moving.

[Alex Eisenhut]

I've learned results are highly variable, because analog video was so forgiving on CRTs no one bothered to follow any kind of standard when generating video. Plus there were so many controls exposed to the user.

I have several cheap scalers and they worked reasonably well on my C64. So I figured they are good enough. Nope. Recently I dug up some VIC-20s and none of them work. The scaler tries to display the screen, it looks like it's tuning the signal in from Mars, then gives up.

My SX-64 works but the colors are muted. My Plus 4 works in black and white.

Very frustrating. Looks like it's back to the CRT for me...

[Ian.M]

The vertical lines are still there, of course. I saw one readily made "lumafix" PCb on ebay for ~ 15 bucks, that's ok, will have it in a couple weeks and then let's see. I hope it also fits in the C128 (wasn't there some shielding stuff there over the board...). Or I really need to dig in the basement to get out a C64 I presumably still have.

Better start digging out your C64, as the C128 and C64 Lumafix mod boards are very different due to the different number of pins on the C64 and C128 VIC chips. This looks like the one you need for the C128: https://www.ebay.com/itm/383720762628

[TinkeringSteve]

Damn! Thx for the pointer. Ok. Tie to convince brother to take it, as he also recently dug out is C64 

That batallion of trim pots looks like... not fun... I can hardly wait of setting it up, haha.

I have looked for analog monitors... they want some real money for that, and it's hard to tell how "burnt out" they already are from afar...
And then they are so damn clunky I might even buy one, but there is nowhere to put it.

[TinkeringSteve]

Btw, any of you got experience with the "Pi1541" "hat" for the Raspi3?

Suposedly fully emulates a 1541 floppy - which the SD2IEC sdcard thingy I have apparently doesn't, and some types of games apparently won't run on it because of that. Haven't read that far yet whether that are multi disk games (although one should be able to press the "next disk in folder" button on the thing, I guess), or some games actually put code in the 6502 in the floppy and it's because of yet...

[Bicurico]

I have the PI1541 - actually I have two of them.
It fully emulates a 1541 and thus allows some games to store and run their code on the 1541 board which runs a 6502 CPU. It allows to use custom ROM images like JiffyDOS.
The SD2IEC only simulates a 1541 with a fastloader. This is a totally different league.
If you are looking at this - make sure to read about the BMC64. It is great!

[TinkeringSteve]

Ok, I now have also tried the RetroScaler 2x, which is a 1/2 price clone of the RetroTink, overall picture looks about the same, just that I got, what some other people got - a vertical white line (and the last scan line being a bit "bitten off" at the beginning),
which some people call normal and a bug of the VIC.

Like here:
https://www.lemon64.com/forum/viewtopic.php?t=73229
https://videogameperfection.com/forums/topic/retrotink-2x-pro-commodore-64-white-line-left-hand-side-of-image/

So the one guy there in the 2nd thread wants to sell this as the retrotink doing a really good job and it not being visible because cheaper scalers doing a bad job.

Ob, but I don't have this artifact on the ODV thing for around 50 bucks that I linked to in an earlier post.
And the overall image looks slightly better on it, too.
Just that it, indeed, does not scale - but my TFT does that, whle retaining the 4:3 aspect ratio if I tell it to, so I don't care.

The ODV is so far the best of these converters I tried - if you don't mind it not up-scaling.

[Bud]

just that I got, what some other people got - a vertical white line (and the last scan line being a bit "bitten off" at the beginning),
which some people call normal and a bug of the VIC

I am pretty sure this is the case, as this luma spike can be seen on a scope at the beginning of the lines in the luma output of the VIC.. Some of the external converters may do extended blanking either by design or unintentionally  so this luma spike gets blanked.

[thinkfat]

Youtube channel to watch: Adrians Digital Basement.

[Bud]

To watch why?

[thinkfat]

To watch why?

There's several videos discussing/trying different lumafix variants for the C64/C128. Might be useful.

[Bud]

I see. The downside is the guy just showed and tried a few kits without actually investigating, measuring and explaining the problem.

[TinkeringSteve]

To watch why?

There's several videos discussing/trying different lumafix variants for the C64/C128. Might be useful.

Wasn't that the guy who doesn't get lumafixes to work on his setup, to his linking anyway? I've seen other channels where it made an improvement.

[thinkfat]

I see. The downside is the guy just showed and tried a few kits without actually investigating, measuring and explaining the problem.

Yes, he's not a true "chef", more the "barbecue" type of cook. Still got some nuggets in the channel.

[Shadowfire]

I spent quite a while working at this same issue as the OP.
Here are my recommendations from best to worst.

1.  Get rid of/ignore the C128, get a C-64C or later model breadbox C-64 if you want the 6581 (get one which has the PLA IC instead of the discrete glue logic is ideal, PLA replacements are readily available if it goes bad, and all of these models have the reliable 8701 PLL IC instead of the 3-chip PLL solution of the earliest models), install the C64 Video Enhancer (videogameperfection.com was where I purchased my kit from), and use a TV set which accepts component video (a component -> HDMI adapter may also work but I have not tried that and so have no recommendations).
Rationale:  The C-64/C-128 VIC-II chip has terrible interference/crosstalk from the internal clocks, resulting in vertical stripes.  The only way to actually get rid of these is with the C64 Video enhancer, which re-implements the VIC-II chip in an FPGA and outputs a clean signal.  The output looks like an emulator on a PC monitor, super sharp, and pixel perfect.
2.  Get a commodore 1084 monitor and hook it up via luma/chroma.  These have limited bandwidth which masks the terrible clock interference, and look fantastic for a CRT.  The 1702 monitor is a second place here, it also has a "clean" display but the dot pitch is larger and image clarity is worse if you look at the two displays side by side.
3.  Get a retrotink which has S-Video input, and a C-64/128 -> S-video adapter cable.  This is the "best of the worst" solution.  You'll see all that crap interference that the VIC-II is generating and that modern displays have the bandwidth to actually display, but the retrotink will ensure that the TV's internal scaler doesn't mangle the C-64's native 240p output.  You can also lump the other specialized high quality scan rate converters (generally over $100) in with this option.  Lumafix will make the display a little bit better, but you will still see it on a modern LCD.
4. Anything else:  (Lumafix alone, cheap scalers, attempting to hook up C-64 video directly to the TV with either S-Video on an older set, or composite on a newer one):  It might not like the C-64's slightly off-NTSC sync and not show anything.  It might struggle with it and have horizontal curling at the top or bottom along with distorted colors (on an LCD!).  I've even seen displays with solid red backgrounds show a checkerboard red/pink pattern if the horizontal sync doesn't track the C-64's output well.  Finally, if you win the video decoder lottery, you could get something that's the same as a retrotink.  You will never get anything better than the retrotink, that's for sure.

Lumafix is a pain in the rear to configure, but when properly configured, does in fact reduce the intensity of the stripes, but on an LCD screen you will still see them, as it cannot eliminate them.  The 1084/1702 monitors still look better than a Lumafix/Retrotink combo because of this.

I have a C-128DCR which I was thinking about doing a board for the C-64 video enhancer.  Unfortunately, on the 128D, the video enclosure is almost entirely under the power supply and there's really not much vertical clearance to work with.  It would require either milling out a part of the video RF shield to allow the cable to escape, or leaving off the top of the RF shield entirely.  Since there was no way to do it "correctly" I abandoned the project after scoping it out.  I use a C-64C with the FPGA video enhancer.

[TinkeringSteve]

Retrotink is NOT the best for C64! It and the clone I menioned have the "white stripe" problem!

CRT is just inacceptable bulk, and often already too dark (worn tube).
Not a real option for my taste.

As said, the "Mcbazel ODV" has a distinctly overall better image than all other tested, including the clone of retrotink.
Its only downside is that it does not up-scale, which is not relevant for my versatile monitor that can be set to scale but retain aspect ratio.
I got that one to be able to also play old 4:3 PC games, and I'd reckon that I'm not the only fancier of older games who has a monitor like that, so an up-scaling feature of a HDMI converter is kinda irrelevant.
The tip with TV's video inputs still perhaps helpful to others reading. I myself don't have a TV, and that's unlikely to change.

So that hyped Retrotink thing is not all that impressive. Especially not for the price.

[Bud]

Lumafix and such are difficult to adjust because "they are holding it wrong", lol. They mix the inverse clock signal into the composite signal. But the thing is that the interference mostly comes from Chroma output of the VIC. I guess noone bothered checking Luma and Chroma signals with a spectrum analyzer.  I did, so there you have it. Some of the Lumafix variations do add a portion of the inverse clock to Chroma but they do it incorrectly , when mixing in to Chroma the added clock should Not be inversed.

[JohnnyMalaria]

You'll never get a modern display to give you the same experience as an interlaced SD CRT. Get a used studio monitor off eBay. I was going to junk mine until I saw I could get $500 for it.

[Alex Eisenhut]

It really sucks and I spent a lot of time and energy and money on various "pro" and consumer scalers, and I agree with your assessment.

The only scaler I like is the Viewsonic VB50HRTV and its successors.

It seems to handle the crap C64 video just fine, albeit with all the flaws piped right through.

The "pro" scalers give you lots of control, but it turns out the controls are useless. I'd like to have complete control on how it digitizes the video but since they are professional units they assume perfect by-the-book video signals. So the controls are mostly for the output side. Not useful.

I also tried LCD TVs and it is also hit or miss. Only certain LCD TVs work.

I am sticking to my 1080 monitor. The 2002 is the same. I don't like the 1084 series as they are flakey and fail. The 1702/1701s are great but hard to find.

It's a shame that Commodore didn't try to address the very real noise problems with the VIC-II, for a flagship graphics and sound machine a very sloppy approach. Oh well.

[TinkeringSteve]

It's a shame that Commodore didn't try to address the very real noise problems with the VIC-II, for a flagship graphics and sound machine a very sloppy approach. Oh well.

Well it was all kinda rushed from that I remember.
An expression I got from the Bob Yannes interview.

[Bicurico]

The sales numbers of the VIC-20 and C64 prove that the design was perfect...

Who would care 40 years ago if there would be display issues on flat screens by 2020.

The cheapest options - as I said before - are:

- The C64 Maxi
- Raspberry Pi 3 running BMC64
- Using a CRT TV
- Using a 1701/1702 or 108x monitor

[Alex Eisenhut]

The sales numbers of the VIC-20 and C64 prove that the design was perfect...

No, it means it was good enough. If the chips were perfect, why did Commodore spin so many revisions? They could have spent a bit of time cleaning up the noise too.

[Rasz]

You'll never get a modern display to give you the same experience as an interlaced SD CRT

interlace is the key here for the 240p signal Im sure

. Get a used studio monitor off eBay. I was going to junk mine

so the CRT was soo good you wanted to throw it out

until I saw I could get $500 for it.

until someone told you its a veblen good
<taps on horehead>genius</>

The sales numbers of the VIC-20 and C64 prove that the design was perfect...

No, it means it was good enough. If the chips were perfect, why did Commodore spin so many revisions? They could have spent a bit of time cleaning up the noise too.

They did so many revisions because they only had inferior engineers left after usual Tramiel excess staff cleaning maneuver. He fired almost whole C64 team after product release - Bruce Crockett (manufacturing), Al Charpentier (VIC) and Robert Yannes (SID) went to start Ensoniq, company Creative had to buy to provide actually working DOS compatibility on PCI cards.
Commodore kept to this strategy even after Tramiel left, they similarly got rid of Amiga hardware team (Jay,RJ,Needle) resulting in shipping same chipsets for 7 years under different names. Whole 9 years of Amiga without HD floppy (required basic PLL update inside Paula).

I'd like to have complete control on how it digitizes the video but

no buts, I found the perfect solution, and its cheap too https://www.eevblog.com/forum/repair/convert-640x200-video-screen-to-640x480/msg3385758/#msg3385758

instead of digitizing video with ADC it uses comparators and tunes every single bit threshold individually, reconstructs digital signal perfectly. Specifically designed for 8 bit computers.

[Shadowfire]

Retrotink is NOT the best for C64! It and the clone I menioned have the "white stripe" problem!

What white line are you talking about?
Here's my C128 NTSC hooked up to a 720p flatscreen via HDMI and the retrotink.
Note: I had to crop the original image to get it under the 4000kb forum file limit.
For the life of me, I have no idea what you are talking about.  Even with this photo you can clearly see the jailbars on the blue background (its actually worse in real life than in this picture), but there is no white line anywhere.
Edit:  I looked at the pictures in the the threads that you linked earlier, and did the standard POKE53280,0/POKE53281,0 to get a black background like in those pics, and still no line on the edge of the display like in those threads.  I'm not sure what to say, maybe its your TV?  I'll dig out my PAL C-64 and check it out in a bit.

[Shadowfire]

OK, I have done a little running of cables and made some findings.
This is the PAL C-64 (running on the only TV I have in the house that will actually show a PAL video signal) with the C-64 Video Enhancer.  There are moire patterns on this picture, but you don't see anything like that in person, its a pixel-perfect image.

I then put the retrotink on the PAL 64 and fed it into the same TV.

It seems that the Retrotink does indeed show a bright line on the left side of the display, but only if you use it with a PAL unit.
Edit: I would suggest contacting Mike Chi about this; however, this may be what the pal C-64 is actually putting out (in the old days with a TV this would be in the overscan area where you couldn't see it, similar to how the NES had a horrible edge when horizontal scrolling)
(confirmed by below post, seems to be a problem with the PAL VIC-II chips.  You don't remember it being there because it was offscreen on the TV/monitor you were using back then.  Another reason to go with the video enhancer.)

[Bicurico]

That line is a bug/feature of the VIC-II.

Code: [Select]

FWIW this is neither the color burst nor the sync signal. It is a bug/feature in the VIC chip that makes the first 1.5 or so pixels of every line white.

The color burst signal would be to the left of the white line, and is not usually visible. Color burst is some defined color at zero intensity - so on a TV this would show up as black. On a B/W monitor and composite input with horizontal position adjustment you can see this as a faint band on the left if you move the screen entirely to the right.

The sync signal is even further to the left, and is 'blacker than black', certainly not white.

Source: https://www.lemon64.com/forum/viewtopic.php?t=73229

Regards,
Vitor

[Rasz]

OK, I have done a little running of cables and made some findings.
This is the PAL C-64 (running on the only TV I have in the house that will actually show a PAL video signal) with the C-64 Video Enhancer.

this guy https://github.com/c0pperdragon/C64-Video-Enhancement ? This is totally skipping VIC-2 output, only way to successfully remove jailbars
works great with RGBtoHDMI https://videogameperfection.com/forums/topic/hdmi-output-using-raspberry-pi-zero/

[Shadowfire]

Yes, the C64VE is c0pperdragon's board.

The RGB2HDMI project is an RGB -> HDMI converter (just like it says) but it needs to be tuned to the clock frequency of the generating hardware to produce good results.  They are basically sampling the analog signal and it needs to sample near the center, not the edge, of a pixel.  This would probably work well* (I haven't used one but the theory seems to be sound) to convert the C64VE's output (which IIRC can be configured to output RGsB instead of YPbPr) to HDMI.

[Rasz]

Its sampling at ~96MHz, I say thats enough to catch perfect transitions

https://stardot.org.uk/forums/viewtopic.php?f=3&t=14430

[tszaboo]

If it is really a clock signal going into the component video signal, there must be a way to remove it, the good old way. Analog filters. If you would filter all the signals that are faster than the component video, so 4-ish MHz, you should be able to get rid of those lines. All you need is 3 opamps, and some passive circuits.

[Bud]

That line is a bug/feature of the VIC-II.

Code: [Select]

FWIW this is neither the color burst nor the sync signal. It is a bug/feature in the VIC chip that makes the first 1.5 or so pixels of every line white.

The color burst signal would be to the left of the white line, and is not usually visible. Color burst is some defined color at zero intensity - so on a TV this would show up as black. On a B/W monitor and composite input with horizontal position adjustment you can see this as a faint band on the left if you move the screen entirely to the right.

The sync signal is even further to the left, and is 'blacker than black', certainly not white.

Source: https://www.lemon64.com/forum/viewtopic.php?t=73229

Regards,
Vitor

Right, it comes out of the VIC chip and can be clearly observed as a luminance spike on the oscilloscope at the beginning of an active line.

[Shadowfire]

My point is that the C-64 changes pixel colors with an 8mhz clock, and if the sampling clock isn't locked to it (even though it might be running 12x faster) you will have the oddball color change last 13 or 11 clock cycles.

[Rasz]

My point is that the C-64 changes pixel colors with an 8mhz clock, and if the sampling clock isn't locked to it (even though it might be running 12x faster) you will have the oddball color change last 13 or 11 clock cycles.

have you looked at the link? its training its sampling clock to the signal. Its even able to recover pixel perfect picture out of BBC micro, computer which varies its pixel clock depending on whats on the cpu bus.

[Alex Eisenhut]

Here's a new cheap one

https://www.ebay.ca/itm/New-VGA-to-TV-RCA-Composite-S-video-Converter-Cable-Adapter-Box-for-PC-Laptop/193312209376?hash=item2d024e39e0:g:JbwAAOSwhI9eYdmY

It has controls.

[Rasz]

Here's a new cheap one

https://www.ebay.ca/itm/New-VGA-to-TV-RCA-Composite-S-video-Converter-Cable-Adapter-Box-for-PC-Laptop/193312209376?hash=item2d024e39e0:g:JbwAAOSwhI9eYdmY

It has controls.

this works in the wrong direction
btw this exact model was already on the market in ~2004

[Alex Eisenhut]

Oh crap. Why is it so damn difficult to make a "RCA" (why can't they just label it video, NTSC, PAL, composite, or s-video?) to VGA with the same controls?

[JDet]

Hi together,

I dived in this subject almost three years ago.
I wanted to connect my old C128D-CR to a modern Display ... I already own a CRT with a SCART input and an old split cable DIN-8 + D-SUB-9 to SCART with a switch for choosing 40 col. or 80 col. mode. I searched through the infinite internet and found something like CGA2RGB converters for the 80 col. mode and the GBS-8200 to connect the D-SUB-9 to the CGA2RGB converter and then the CGA2RGB converter to the GBS-8200 and finally a VGA or DVI Display to the GBS-8200.
Fine - winner, winner, chickens dinner
But what's about the 40 col. mode??
So I developed my own solution to connect a C128 to a SCART display device.
It is not perfect - the 80 col. mode ist nice but the 40 col. mode with the LUMA, CHROMA & COMPOSITE signals depends on the cable and the quality of the display device. Many TVs with a SCART input do not support S-VIDEO (CHROMA&LUMA) with SCART or have a bad qualitiy.
It is a mess ... doesn't make a lot fun. My device works the best with a CRT.
You can watch my video, if you are interessted.
https://youtu.be/qOvFwwrAEIk

In my opinion @Rasz is right.
If you want to connect a C128 to a modern display with good picture quality, you have to use:
1. build or buy the RGBtoHDMI converter https://github.com/hoglet67/RGBtoHDMI/wiki with digital interface to use the 80 col. mode. You can connect the HDMI output of the Raspi Zero to the HDMI input of yout TV and enjoy the 80 col. mode of your C128
2. build or buy the C128 component video mod from c0pperdragon https://github.com/c0pperdragon/C64-Video-Enhancement/issues/64 I pushed c0pperdragon a little to design a smaller version that fits into the C128. So it is possible to get component output of the VICII / 40 col. mode. Currently you can't buy the new version for the C128. You can buy and use a version for the C64 https://videogameperfection.com/products/commodore-component-video/, but it is too big to mount it into a C128. If that is done, you can connect this mod to the component input of your display. Then you can enjoy 40 col. mode on your big TV.

The best solution would be a further development of c0pperdragons way.
Designing and building an FPGA based solution to grab the necessary signals direct from both video ICs (VDC & VICII) and generate an HDMI output signal.
That sounds simple, but unfortunately it will be tricky.
Is there anybody with FPGA knowledge and time to do such a project?  It would be challenging 

So cheers and RETRO ON.