[mythtv-users] Video out & a stereo

Ray Olszewski ray at comarre.com
Mon Jun 23 12:30:51 EDT 2003


At 11:07 AM 6/23/2003 -0700, Poul Petersen wrote:
> > I'm having issues hooking up my MythTV box to my entertainment system. 
> First off I usually run all audio video equipment through my stereo then 
> have a single line going to my TV. This did not work with the computers 
> SVideo out connection, the screen would scroll. So I then just hooked the 
> computer up directly to the TV using the composite out and just ran the 
> sound through the stereo. This works for the most part. The only problem 
> I still have is that it is causing some sort of feedback to the stereo, 
> and other video sources I try to use will have screen issues if the 
> computer is hooked up to the TV. If I unplug the video cable from the 
> computer all works well.
> >
> > Has anyone else experienced this sort of thing? Are there any filters 
> or something that I could get to take care of this issue?
>
>         I wonder if this could be some sort of differential grounding 
> problem.
>If the stereo, TV and mythbox are not plugged into the same house circuit, 
>you might
>try that (try using the same outlet). If you have bad circuit grounding, 
>you can
>actually get current flowing through your ground wires - I've actually seen
>a situation where a monitor was fried because the ground on the outlet it 
>was plugged into
>had a potential difference from the computer outlet ground.

A grounding problem is the natural thought for the second problem (the one 
with audio) he describes.

As to the first problem (video rolls when connected through the stereo) ... 
way back in the Dark Ages, before there was Macrovision to protect 
commercial videotapes against unauthorized duplication, a trick video 
publishers used was to put a weak vertical-hold signal on the tape, so that 
the image rolled during playback of copies ... or sometimes even the 
original tape, depending on the equipment ... the last part being the 
reason this approach faded away.

So the original (video rolling) problem may be that running the signal 
through the stereo weakens it enough to interfere with VH. If so, my guess 
is that you'll need either an in-line amplifier for the video signal (check 
flea markets, I'd guess ... these used to be very common) or a replacement 
for some piece of the (undescribed) hardware involved ... probably the 
video card.





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