Removing RGB jail bars idea?

[Drakon]

Lumclaw try using composite sync instead of composite video and see if that works. Also what's this "screen rolling" ? I've never heard of or seen this issue.

[lumclaw]

Lumclaw try using composite sync instead of composite video and see if that works. Also what's this "screen rolling" ? I've never heard of or seen this issue.

I guess so. At the moment I have two model 1 rgb cables, it'd be OK to make one composite sync. Soldering tools have to come first...

Yeah the screen rolling isn't related to this topic. I was just pointing out lifting pin 50 did not fix it.
This CRT's component input doesn't seem to like something about Genesis video. In certain places, the picture rolls. Usually when large amounts of white are shown. Sonic 3 "file select" and "chaos emerald results" screens for example. Also the snowboard segment of Ice Cap Zone.

But composite sync won't work on the RGB to component device we both own. You mentioned that earlier yourself.

[Drakon]

I guess so. At the moment I have two model 1 rgb cables, it'd be OK to make one composite sync. Soldering tools have to come first...

Yeah the screen rolling isn't related to this topic. I was just pointing out lifting pin 50 did not fix it.
This CRT's component input doesn't seem to like something about Genesis video. In certain places, the picture rolls. Usually when large amounts of white are shown. Sonic 3 "file select" and "chaos emerald results" screens for example. Also the snowboard segment of Ice Cap Zone.

But composite sync won't work on the RGB to component device we both own. You mentioned that earlier yourself.

Oh yeah I had no idea you're using the same one. Anyway you can wire up a four pin crystal oscillator to feed a subcarrier signal into the encoder that's separate from the vdp subcarrier you can try that. 3.579 / 3.58 mhz is the right speed oscillator. I've run my cxa1145 off of a four pin oscillator as this speed and got colour fine....

Now that I think of it before I got scrolling jailbars when doing that...I wonder if disconnecting the vdp subcarrier would eliminate the jailbars when using an oscillator to drive the cxa1145.

[lumclaw]

Right. The CRT's component screen rolling already happened before I disconnected subcarrier. Jailbars are what went away.

It's the HDMI encoder where disconnecting subcarrier seems to be a problem.

I don't think I'll worry about cxa1145 more than necessary. Having rgb this solid, messed up composite video or not (I doubt I currently own a model 1 composite cable) isn't an immediate concern.

[Drakon]

Right. The CRT's component screen rolling already happened before I disconnected subcarrier. Jailbars are what went away.

It's the HDMI encoder where disconnecting subcarrier seems to be a problem.

I don't think I'll worry about cxa1145 more than necessary. Having rgb this solid, messed up composite video or not (I doubt I currently own a model 1 composite cable) isn't an immediate concern.

Okay I took out my tester genesis with the subcarrier disconnected. I wired a crystal oscillator into the cxa1145 and wired up s-video. I still got scrolling jailbars, very noticable. Either the oscillator is somehow not working right or the interference is also in the rgb lines themselves. Next I plugged the s-video modded 32x into the system with vdp pin 50 disconnected and there it was again...weaker scrolling jailbars. Plugging the s-video modded 32x into the system that still has the subcarrier wired up gives me no scrolling jailbars in s-video, no jailbars at all. But the subcarrier is adding jailbars to the rgb when I wire up rgb to component. Still the scrolling jailbars from the 32x are much weaker than the scrolling jailbars from the cxa1145.

I still don't understand what you mean by screen rolling. Mind taking a pic please?

Also does the hdmi encoder take rgb or component video? If it's taking rgb, then use composite sync instead of composite video and see if that fixes your problem with it.

In conclusion with my experimentation disconnecting the subcarrier at the vdp removes jailbars in rgb. However disconnecting the subcarrier makes the jailbars start scrolling horizontally in s-video / other formats no matter what video encoder you're using. Also rgb seems to have zero rainbow banding and it doesn't matter if the subcarrier is connected or not. I can't explain why these systems work this way....but they do.

[lumclaw]

Pics don't capture the full effect. Since it's presumably happening up to 60 times per second. Screen rolling resembles a vertical hold problem. In weaker situations, it's closer to 'shaking' than rolling.

Could it be incorrect resistors making the signal too strong for this CRT? Games do look rather bright.

Sonic 3 & Knuckles. 60hz, VA2 Japanese Megadrive.

[Drakon]

I dunno I've never had screen rolling. Try adding resistors and see what happens

[lumclaw]

I'm not ready for that. I'll have to get a test kit and built skills first.

[Drakon]

I'm not ready for that. I'll have to get a test kit and built skills first.

repost from my forum:

I've been busy with commissions but I felt like taking a day off from commission work. My component video capture device has been here for a while now so I unpackaged it and got to work with some component video screenshot goodness. The picture I got on the capture device was extremely unstable. I tried using different rgb to component encoders on my genesis system and got the same unstable effect. I tried my own software as well as the software that came with the capture device, changed all the software settings, but nothing would make it stable. The next logical step was to try adding component to the signal lines themselves. Since the picture is unstable I just assumed stability would be caused by luma and not the colour lines. First idea was to use a capacitor. I looked at the existing circuit on my rgb to component pcb and there's a whopping 1000 uf cap on the luma line right before it goes out the rca jack....so much for that idea. The next idea was to add a resistor, I added a 50 ohm resistor in between the rgb to component encoder and the capture device and suddenly the image became 100% stable!

Now for a sega genesis component video screenshot party.

First with everything as original (well pretty much)



Now with the colour subcarrier line lifted from the pcb at the vdp chip:



Let's see those same shots with the sharpness turned up ultra high.

Default wiring:



With the subcarrier lifted (vdp pin 50)



It seems that thread on assemblergames is completely correct about the subcarrier problem...win!

[keropi]

I have solved the "bars" issue on both my megadrive1 and sms2 by using c-sync instead of composite...

this is before (notice the brown stones pattern) :





and after:



I had similar results on my VA5 megadrive1 , on both shots there is no signal processing from the lcd tv , all enhancements are OFF and using GAME mode.

[lumclaw]

That's pretty weird. A different type of lines than usual. Wavy instead.

Speaking of lines and sega... I did get those common Famicom lines using a genesis rf box + psu. At least that proves my CRT accepts such rf perfectly on like channel 95 or so.

[Drakon]

That's pretty weird. A different type of lines than usual. Wavy instead.

Speaking of lines and sega... I did get those common Famicom lines using a genesis rf box + psu. At least that proves my CRT accepts such rf perfectly on like channel 95 or so.

composite is wavey by nature it's a pretty nasty quality signal. Composite video will get jailbars mixed into it because it's generated with the colour subcarrier. Of course as my screenshots show disconnecting the subcarrier makes it so using composite video won't cause jailbars when used with rgb. Or atleast nothing strong enough to notice.

[keropi]

yeah on my machines (PAL version) I only got those wavy bars... my CDX also has them but I am not eager to mod it ATM... LOL

[grimm]

Ive been trying to read all these pages to understand this issue.. Im taking it a downscaler will not fix the jailbar issue? I just got a 32x, and my jailbars has become worse using the 32x hardware.

[lumclaw]

Ive been trying to read all these pages to understand this issue.. Im taking it a downscaler will not fix the jailbar issue? I just got a 32x, and my jailbars has become worse using the 32x hardware.

There's more than one type of jailbar. Straight or wavy matters.

Hmm, 32x should not make jailbars worse when using RGB...