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Old 23rd May 2024, 5:54 pm   #1
Keith
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Default Wierd effect on TV22

Hi there,


I wonder if someone can suggest a reason for a wierd picture on a TV22.
I'm feeding video from a PC using Modelines to get the 405 line video. The pictures attached are from the computer monitor and then the TV22. It looks as if smooth level changes cause discrete jumps in brightness. The test card looks fine.

Any help would be appreciated.
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Old 23rd May 2024, 6:53 pm   #2
The Philpott
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Default Re: Wierd effect on TV22

Do you have a duplicate cable so you can check it by substitution?

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Old 23rd May 2024, 7:04 pm   #3
Keith
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Default Re: Wierd effect on TV22

Hi Dave,


Thanks for the reply. Not sure which cable you are referring to. The PC output is from a dual output Radeon graphics card. This feeds a modulator which outputs on band 1 via coax to the TV22 aerial input. The test card is just a .jpg via the same system,

This arrangement has worked perfectly in the past but hasn't been used for a couple of years.
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Old 23rd May 2024, 10:38 pm   #4
Graham G3ZVT
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Default Re: Wierd effect on TV22

Keith, just remind me are you still using Vidblaster X to source your pictures?

Is it that anything from a "player" module gives that strange aliasing effect and anything from a "still-store" is OK?
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Old 23rd May 2024, 11:27 pm   #5
The Philpott
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Default Re: Wierd effect on TV22

Hi Keith, being suspicious of (any) data lead is one of the first things that spring to me mind, so I always suggest it as something (inexpensive) to eliminate from enquiries!

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Old 24th May 2024, 8:15 am   #6
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Default Re: Wierd effect on TV22

Unless I am missing this, it looks like it needs "picture shift". On the crt.
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Old 24th May 2024, 8:35 am   #7
Keith
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Default Re: Wierd effect on TV22

Thanks for the replies. I did wonder about the level into the modulator, Graham. I shall try reducing it.
Yes, it does need a vertical shift which I can easily do but I want to get to the bottom of the weird video first.
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Old 24th May 2024, 10:04 am   #8
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Default Re: Wierd effect on TV22

Graham,
No I'm not using Vidblaster. I just use VLC fo everything. The test card is just a .jpg (also via VLC) which looks fine but maybe it outputs a lower level than the videos.


Incidentally I got an email notification of your post re modulation level but the post hasn't appeared on the forum....strange!
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Old 24th May 2024, 4:14 pm   #9
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Default Re: Wierd effect on TV22

There was an error in my last post. The test card was actually produced from Windows picture viewer ( and looked perfect). If I now use VLC to produce the same image, it has distorted effect. The photo from the TV22 screen shows the image from Windows Picture Viewer (top) and from VLC (below) so I now think it is an artifact of VLC. Reducing the modulator input doesn't affect the problem. I think I will now re-install an earlier version of VLC.
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Old 26th May 2024, 10:30 pm   #10
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Default Re: Wierd effect on TV22

Well, this is still proving impossible to sort out at present. I tried earlier versions 1.01 and 2.?? of VLC. These exhibited a different problem to the current version - the window was visible on the TV but contained no image. i.e. black. Image on the computer monitor was fine.


So I'm still confused. This is all done using the "extend display horizontally onto display 2" which has always been OK in the past. i.e slide the VLC screen to the left and hit "F" for full screen.


I tried selecting "clone display 1 on display 2" Here the image looks OK but the line standard has reverted so I'm seeing four narrow images. Is this a limitation of Modelines?


I am faithfully reciting my well used mantra "This worked once so it should work again"!

I have 5 days to get this sorted as I've promised to have a working TV22 for our village open gardens event! A still picture stating "Normal service will be resumed as soon as possible" just won't cut it....
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Old 27th May 2024, 8:51 am   #11
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Default Re: Wierd effect on TV22

Keith
Have you checked the signal source output, I have had some weird picture effects on old TVs as a result of too strong a signal going into or from the modulator flattening the range as the early TVs didn't have much in the way of AGC, For example feeding my TV22 from an Aurora needs at least 10db signal reduction to work.
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Old 27th May 2024, 2:24 pm   #12
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Default Re: Wierd effect on TV22

Hi Chris,
Thanks for the reply. I have now found an alternative 32 bit media player (SM player) that will work with my the old XP PC that I use. The good news is that it pretty much solves the problem, although there is still a bit of peak flattening going on. Interestingly I had to select the "Direct 3D" video driver otherwise the window had no video in it. Maybe that's the problem with the old versions of VLP. I shall investigate further. Anyway, at least the pressure is off for our village event (phew!).
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Old 30th May 2024, 3:50 pm   #13
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Default Re: Wierd effect on TV22

Just a quick update for those who might encounter similar problems.

In my case the problem was the wrong o/p driver on VLC. It had defaulted to "automatic". There are a number of options on the "video" tab which all look fine on the PC monitor but give different effects on the output to the TV22 via the modulator. The one that caused the effect shown was "Open GL" - no idea what it's for! The one that gives the best result is "Direct3Ddraw". It's worth noting that you have to restart the video for the change to take effect.

So we seem to be back in business, although how I manged to hit on the right set up initially I'll never know.
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