Wavy NES Output

[teknix1]

Hi,

I was getting ready to install my new NESRGB into my Famicom AV, but noticed some issues on the video output. Something is making the composite output wavy at the top of the image. I still tried to install the NESRGB but the result is the same. So there's a fault somewhere in my Famicom AV. Here's a video to demonstrate the issue, look at the curtain at the top of the screen.
https://onedrive.live.com/redir?resid=2 ... video%2cTS

I have some electronics knowledge but don't know where to begin debugging this. I tried different PPUs and installed a new 1.5A regulator but the output is always the same. Any help is greatly appreciated.

Thanks in advance!
Nic

[Voultar]

That sounds like a failing capacitor issue to me.

[teknix1]

That sounds like a failing capacitor issue to me.

Oh yeah? That's a good start. Any clue which one I should look at first?

Thanks
Nic

[Voultar]

It definitely sounds like a power conditioning issue. If you've ruled the power adapter out, check the power filter cap.

[teknix1]

Excellent, I will do that tonight. Thanks for the suggestion!

Nic

[Sixfortyfive]

Both NES consoles that I've tested video capture on (one un-modded front-loader, one top-loader w/ NESRGB) have this same behavior. I just assumed it was normal.

[Pasky]

This is normal. It's not power interference, this is caused by the NES's missing pixel at the top left of the screen every other frame. It confuses some capture devices and even tv's and you get that distortion on the top. It's ironic because the missing pixel was designed to improve the image quality on older televisions by messing with the video timing but causes some modern tv sets to freak out and create that curl at the top but it eventually corrects itself which is why the top is only affected. If you play the video frame by frame you'll notice the capture is perfectly square every other frame.

[Sixfortyfive]

I also assumed that the reason why this largely went unnoticed is because it would normally be masked by overscan.

[Pasky]

I also assumed that the reason why this largely went unnoticed is because it would normally be masked by overscan.

Correct. It's on my JVC RGB monitor. I don't believe Sony professional monitors are affected, but unsure.

[teknix1]

That's too bad, seems like all my TVs and monitors exhibit the issue. Is there a way to rectify this? It show up on my scaled up image through my XRGB3, it's right in the center of the screen.

Also, is there a name for this extra bit so I can do some research online?

Thanks
Nic

[Pasky]

No. It's an issue with the NES's PPU itself, as this was how it was designed. It's possible for vile tim to fix it with the NESRGB as Kevtris has done it with his FPGA adapter, but I don't know if he would ever implement it, he seems rather slow to respond to things as well.

http://wiki.nesdev.com/w/index.php/PPU_frame_timing

See the even/odd frame for the cause. Doing this supposedly made a stationary image look better over composite video. When rendering is disabled the pixel does not disappear and when it is enabled it skips that pixel.

[teknix1]

Ok, I understand, thanks for the information. Hopefully Tim will fix it at some point.

[Pasky]

Just FYI, the xrgb mini accepts it properly and does not display the distortion.

[keropi]

could it be that this missing pixel from the PPU be the cause of upper screen flashing on my LG sets??? you can see it in the upper part of the screen and some minor flashing on the bottom: https://www.youtube.com/watch?v=2UTWT6Fc_vA

other sets and framemeister are fine though...

[Pasky]

I'm unsure. it's possible since it's oddly there at the top of the screen only, I don't know if that would explain the bottom screen flashing however. Does it happen on all games or just certain colors or?

I have a rom that disables background rendering (which stops the nes from skipping the odd frame tick) which would mean if it's still flashing then it's not the PPU issue.

https://www.dropbox.com/s/korhspmwsvzvd ... s.nes?dl=0

After pressing start to begin, rendering should be disabled and the distortion should stop. If it doesn't, it's not the pixel.

[keropi]

well it doesn't happen in all games, just those what have bright backgrounds or something...
another person on amibay is getting the same with his install on a twin-fami and LG sets.

I remember I had made another vid, with either c-sync or original famicomAV composite: https://www.youtube.com/watch?v=zkKFgF7k3s8
seems it's another issue, else the original composite would behave the same ? sorry for derailing the thread

[teknix1]

My XRGB Mini just came in today, I plugged in everything and unfortunately the distortion is still there. It doesn't seem to be as bad as with the XRGB3. Boy is this device simpler to use than the XRGB3! Pasky are you sure you are not having any distortion? Could you try SMB3 and look at the curtains in the intro? If you really aren't seeing any and the image isn't cropped by zooming or some other setting, would you mind sharing your settings?

Thanks
Nic

[Pasky]

Yes I'm certain it isn't there with the xrgb mini, I'm not certain if it's the mini or if it's my tv that matters though. My JVC RGB monitor shows the curl at the top, but my sony LCD's do not with the xrgb mini neither does my PEXHDcap using the XRGB mini.

[Shining]

I had/have this issue with the XRGB-Mini as well. First, my vanilla AV Famicom hooked up through comopsit displayed this issue. Then i got it modified for RGB (Playchoice-10 PPU) and it disappeared. Then i got it re-modified with the NESRGB kit and the issue came back. I remember the modder telling me that he had to "change PPUV to #CS" to make my cable (Official Gamecube RGB cable) compatible with the XRGB-Mini/NESRGB.

[teknix1]

Hmmm, I'm already using #CS in my mod. I remember trying all the possible sync sources from the nesrgb when I had my xrgb3 and none of them fixed the issue. It's really not as bad with the mini when compared to the xrgb3, I think I will leave it alone. Unless someone comes up with a great fix.

Thanks
Nic