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Old 10-22-2003, 06:34 AM   #1 (permalink)
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Default TV-Out -"interference" problem

Ok, I'm having a problem with my tv-out signal from my comp.

I'm running a generic GForce FX5200 video card and using a TV as a second monitor to run myHTPC. Now the problem is that I get loads of what appears to be an interferance pattern of some kind on my tv-out, which is kinda annoying and I;m having a hard time tracking down the cause.

I've recently upgraded my power suppply to a 300W Zalman Ultra Quiet and my mobo and cpu to a GIGABYTE GA-7VA and AMD AthlonXP 2600+ [2.08GHZ 333], using a GlobalWin FSP82 cpu-cooler.

The noise/interferance is still there so I'm guessing it didn't come from my older components.

Anyone got any ideas as to where this may come from or had a similar experiance?

Is this just a problem with the gaphics card not really being up to the job? And if so can anyone recomend a card that has a good quality tv-out signal?

I'm not really overly bothered about it being a top-rated games card, as long as it's got reasonably fast 3d and a good clean, quality picture, and not too pricey

cheers
ToMb
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Old 10-22-2003, 02:40 PM   #2 (permalink)
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First, what kind of monitor do you have? Second, whats the refresh rate do you have now? I had a similar problem, when I tried to increase my res to 1200*1600 from 1240*768 and 75Hz, and it made a funny noise.
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Old 10-22-2003, 03:24 PM   #3 (permalink)
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at least u can get ur vid card to give a output onto ur tv, i cant with my stinken geforce 4 ti4200
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Old 10-22-2003, 04:17 PM   #4 (permalink)
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make sure the bale going to the tv isnt passing near anything that can cause EMI. try moving the cable or the rv further away if possible cause i know when my friend setup a dual monitor system if he put the monitors to close together then he got interference on both. Also try with another cable and if possible try on another card a a friends house if possible
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Old 10-22-2003, 06:40 PM   #5 (permalink)
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Is the interferance slightly wavy diagonal lines? If it is I'm afraid its because your (and everyones for that matter) TV uses either 525 (NTSC) or 625 (PAL) scan lines (vertical res in pc speak). The problem is PC's don't use these resolutions and conversion is never perfect (plus interlacing probs etc).

No matter what you set the pc res at it will never match a TV (closest is 600 X 800 or the old 480 X 640).

Also, as noted above, interferance can also cause problems. Try getting your hands on a FERRITE coil or rod and wrap the video cable around it.

BUT there is some good news. If you watch movies (like I do) on your TV then get Zoomplayer which will allow you to resize the video file being played to anything you require.

I use a cheap ATI R9000 and its well up to the job of TV out work and plays most games at acceptable levels (but forget AA), but hey, who cares, at least I'm not some saddo watching movies on a tiny pc monitor with no mates.
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Old 10-23-2003, 06:02 AM   #6 (permalink)
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yeah, the interferance is indeed slightly wavy diagonal lines

I do indeed also use zoomplayer so I'll try getting zoomplayer to resize movies and stuff to the appropriate rez. Don't want to set the output to the TV to PAL rez tho (currently it's 1024*768) as then it's impossible to see what the hell's going on in myHTPC as all the text and boxes are huge!

I was under the impression that PAL resolution was 720*576 tho, or am I getting it confused with something else?

The pattern seems to sort of come and go in waves as well, which leads me to suspect that it is indeed interferance of some sort.

Found that the forums over at http://www.tvtool.info/ haev a lot of usefull info on this sort of thing as well. Unfortunately it seems that tv-tool itself doesn't yet support all the fancy options that I think I need to sort this out on GeForce FX based cards.

Anyways, I'm going to go buy a nice sheilded cable today and try plugging it into the s-video input of my flatmates tv and see if I still get any interferance. At the moment I'm just using the SCART input on my tv as I don't have an s-video input and as far as I understand, that's where some of the interferance/picture degredation might be comming from?

cheers
ToMb
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Old 10-23-2003, 04:53 PM   #7 (permalink)
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Hi ToMB,

Yeh, I'm in the UK (so PAL) and my ATI gfx card Displays are set to 1024 X 768 (pc monitor) and 1024 X 768 (TV PAL). The 1024 X 768 for the TV is NOT the output to the TV, BUT is the desktop res (ie the monitor res) that is to be CONVERTED to PAL (625 lines). If anything the TV display (if it was actually 1024 X 768) would make everything very small (the OPPOSITE of what you say myHTPC does). Maybe its BECAUSE its not doing the conversion corectly that you have the huge text boxes? I don't know the answer as I don't use myHTPC, sorry.

As for PAL, you may/may not be aware a TV (PAL) does not use all the available scan lines (625) but uses a maximum of 576 lines, this is because the TV tube design (and sometimes the case of the TV overlaps the screen anyway) does not allow the full 625 lines to be displayed. The cloaked lines (the ones you can't see) are called the 'overscan'. The TV standard of viewable lines for PAL TV is therefore 576 lines (a la PAL DVD's).

Hope the shielded cable works (and if so make a post, I could kill for one if it works!) but I thought it was because pc's use progressive scan (top to bottom) and TV's use interlaced (odd lines, then even lines to make one frame) hence the wave effect (plus, of course the conversion, AND the frequency which makes them come and go).

I haven't found a site yet that explains wether or not a gfx's card TV-out sends an interlaced signal to the telly or a progressive signal to the telly, but I do know that a DVD watched on the telly from the pc makes the wavy lines virtually unseen, which leads me to believe its an interlacing problem. Maybe the answer is one of those 100hz tellys instead of a standard PALs 50hz?
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