Scrolling vertical black bar in live tv picture

[jaymann]

Sorry for the long post in advance...

I've had this problem since day one and gave searched high and low to try to fix, but no luck so far. Any help is appreciated.

I have a scientific atlantic explorer digital cable STB, using S-video out to regular Sony TV. 2 x PVR250 MCEs, ATI 9600 non-pro, i'm using the s-video in from the digital STB, one using a split analog cable.

Here's the problem - i get a scrolling, 4-5 inch wide vertical black "bar" or black area that moves from left to right across the screen in the digital, s-video picture only. The analog TV-tuner picture is great, no issues. It can be quite subtle (some people see it as a brightening and darkening of the whole picture), and can be seen clearly on a channel with a darker, one-color background or in darker scenes. It scrolls across about once per second. It does show up in recorded files as well of course. Here are all the things I've tried and ruled out:

-not the hauppauge card itself - same problem occurs running the s-video through the other card
-used the most updated hauppauge drivers off the hauppauge site
-not sagetv itself - same problem in beyond TV trial
-not the s-video cable - replaced it and also tried composite in, no difference
-changed the decoder to NVDVD - better picture overall, but no change to the specific problem
-tried 3d on/off, overlay vs vmr9, hardware accel on/off, every other setting i could think of! no change
-deinterlacing on/off (although s-video is deinterlaced, so this is kind of irrelevant, but still seems like it could be some kind of interlacing problem)
-various refresh rates off the ATI card, no change
-updated ati drivers, no change
-changed the various settings on the ATI card (flicker removal, etc)
-problem isn't from the STB at least in terms of running s-video or composite (or coax) digital signal direct to TV - problem doesn't show up

I'd post a screen shot but its hard to see in a single frame - you need a few seconds of video to see it. in a single frame it just looks like one side of the picture is slightly darker than the other.

Depending on the settings, (vid quality, etc), the rolling black area will actually pixelate a bit as well. Also depending on settings the bar can be more dispersed or more defined, but it is always there.

Its driving me crazy to the point where i have my analog cable PVR as the primary decoder - the image is not quite as good except for the fact that it doesn't have the scrolling black area.

The fact that it is the digital signal only provides a clue, but nothing i have been able to track down.

thanks for any help or suggestions!

[salsbst]

ground loop? Are the computer and STB on the same electrical circuit? If not, see if you can get them on the same one.

[jaymann]

i had read about ground loop interference but wasn't sure how to test or correct. Everything is on the same outlet and i must admit that I've daisy-chained 2 power-bars to achieve this (since the other plug is used for a homeplug networking node). Not the best set-up. Is there a recommended way to check for a ground loop problem? Connect a wire from the STB to HTPC?

[salsbst]

Well, there's this: http://www.findarticles.com/p/articl..._1/ai_88680232 which does seem to suggest that your interference is not the ground loop problem.

I'm starting to suspect your capture card.

Have you tried using a composite rather than s-video cable? Perhaps the s-video shielding is off on the card.

Have you tried re-seating the card or moving it to a different PCI slot or (temporarily) computer?

[zoundz]

If it's a vertical bar scrolling horizontally, it is not a ground loop humbar. Usually a vertical bar like that is indicative of crosstalk between 2 different video signals. What you are seeing is the horizontal sync of one video signal superimposed on the other. No two unsynchronized video signals have exactly the same horizontal freq.

I didn't quite understand your description of the wiring setup, but it sounded like you were sending the S-Video signal from one of the sources through the other source. (STB through video card or the other way around?). If that's the case, you are probably suffering from inadequate isolation between the sources. This could be an iffy shielding situation or inherent in the hardware. You might need to resort to an outboard switch rather than relying on the input selection switching of whichever one is downstream of the other. The RCA 6x1 switchers seem to work pretty well for under $100.

[jaymann]

I may have made the setup seem more complicated than it actually is. I have the 2 of the Hauppauge PVR 250 MCEs, and only one digital STB, so one PVR gets the s-video in direct from the STB and the other gets co-ax in and uses the TV tuner (cable is split prior to the set-top box). Should be a pretty typical set-up i would think.

Now - I *DO* also run a co-ax out from the STB direct to the TV - this allows the wife to watch TV the "old school" way while i'm still tweaking the Sage setup. She just uses the "TV/VIDEO" button on the TV to switch the input. I wonder if running both cable out and s-video out of the STB is causing a problem. I'll check that tonight.

Its not the one PVR card either - tried that one and tested by switching the inputs around (s-video into the other one and co-ax into the first one). Same problem occurs on the other PVR when i run the s-video in.

Same goes for composite in - tried it instead of s-video and also replaced the s-video cable i was using. no luck there. Also replaced the s-video from my ATI card to the TV-in. My ATI card only has s-video and dvi out so no other outs i can try there if it is in fact an ATI problem, but again, the ATI outputs perfectly for the co-ax PVR signal, so by itself is not the source of the problem.

It *does* seem like some kind of interference between two signals. If i run the STB s-video out direct into the TV to test it - clean picture. But as soon as the signal goes through the PVR and out my video card to the TV (all with S-Video), the interference appears. But since this would be how everyone with a STB sets up their system, my problem could not be unique.

[salsbst]

I wonder if running both cable and s-video out of the STB is causing a problem. I'll check that tonight.

I agree... try removing the connection between the TV and the STB.

Not that I know what I'm talking about or anything

[jaymann]

well it was definitely crosstalk between the signals running through the TV. It appears that it was the TV itself introducing the crosstalk. The fix was a little strange though - removing the co-ax in to the TV (from the STB) changed the inteference but didn't actually remove it. It DID go away though once i fiddled with the cable connection from the STB to the TV. So it seems that the TV cable-in plug was the source of a leaky signal interfering with the other signal going into the video 1 input. anyway - it works so who cares! thanks again for the help on this board!