[mythtv-users] TV-out problems

[Richard Lee-Morlang]

On Tue, 2003-04-22 at 13:35, Dave Weaver wrote:
> However this is all somewhat spoiled by a horizontal sweeping flicker -
> about 3 'sweeps' per second. It's a bit like what you see when you see
> computer monitors on TV, except it's a vertical lines moving in a
> horizontal sweeping motion.

I had similar problems but with horizontal lines moving in a vertical
direction.

>From the research I did, it seems this is referred to as banding (at
least in my case), and is caused by noise picked up by your cables. In
my case, there were four primary sources of noise:

1) a hub I had sitting near the rest of my equipment - when turned on,
it severely interfered with the cable TV signal. The kind of
interference varied depending on the channel. Solution: get rid of the
hub.
2) if you have a cable tv signal or tv antenna plugged directly into
your TV, the ground on that connection can interact with the ground on
the cable connected to your computer, and cause noise in the image.
Solution: unplug the cable from the tv, since I'm using myth to tune
channels now anyway
3) I had a splitter on my cable connection so I could connect both my
vcr and my myth box to the cable signal. When I connected the myth box
directly, bypassing the splitter, the picture improved significantly.
4) I had bought a new NVidia Ti4200 card for my myth box. While trying
to solve my noise problems, I noticed a small improvement in signal and
picture quality when I tried my old NVidia MX440 card.

I also managed to add a lot of noise by trying out a different S-Video
cable.

I would suggest:
1) turn off every electric device you can, hopefully leaving just your
TV and computer running. If that improves the signal quality, turn
devices back on, one by one, to see which ones contribute to noise
2) eliminate as many device interconnections on your computer and TV as
possible. Start with only the power cords, and the video connection to
the TV. Then gradually add more connections, starting with the cable
signal to your tuner card. Take note of how each added connection
affects the picture quality.
3) avoid running any cables near any of your device power supplies as
much as possible

If you can narrow down where the noise is coming from by trial and error
and process of elimination, you might find that all you need to do is go
out and by a cable with better shielding to solve your problems. 

Rick