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Old 16th February 2003, 12:47   #1  |  Link
Zep
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Is this filter possible or impossible to code?

The problem I'm having appears to be luminance banding. Old VHS tapes and also my
analog cable on certain channels I get this interference band across the whole screen
horizontally and it slowly rolls. It is brighter in the middle and then fades above and below
to a normal picture. The color is fine just brighter in this band. I can get rid of it in
Photoshop perfectly by doing a inverse gradient fill over the band in the luminance channel
so i know it is possible but how to do it in an algorithm for use in a filter is beyond me.

here is an example clip of what i mean . It is 6 megs DivX 5.0.3 and no filters.

Banding.avi

My thoughts are the banding should be detectable because it is a straight horizontal
band across the whole screen and rolls very slowly and at a steady pace. This is
something you see in footage itself almost never so I thought its movement should
be detectable temporally.

Can any of you gurus here take a look at the clip and tell me if you think a filter
like that is possible and worth doing? Are there any band removers filters out
there that i missed? So far the best filter to at least soften the bands without
destroying the the rest of the picture via blurring and ghosting is Pixiedust filter.

Thanks


Zep
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Old 19th February 2003, 03:36   #2  |  Link
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Very difficult.

Have you tried playing it on more than one TV? Sometimes the problem is actually bad capacitors in the TV's power supply.
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Old 19th February 2003, 05:52   #3  |  Link
Zep
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This interference comes from the cable company. The VCR tuner picks it up, my TVs pick it up (all three of them) and of course the direct feed into my ATI 8500 all in wonder
picks it up. The cable itself goes into a basic splitter then 4 cables from there run to
different rooms in my house. I tested before the splitter and same thing.

It occurs only on certain channels. basically channel 2 to channel 14 which
happen to be where cbs, abc , nbc, wb, and fox are lol

all channels above 14 are rock solid but those channels have hardly anything worth
watching

The problem is it is analog cable TV feed and not digital. Some days it is fine and others
i get 4 bands but most of the time it is what you see in clip I posted.

Thanks for taking a look and i know if you think it is very difficult then it must be
since you make some of the best filters.

Oh there is one interesting thing i found after i posted. Temporal cleaner detects
the motion VERY WELL but cleaning up the bands it can not do since to get rid of them
you have to crank up the thresholds so much you destroy the whole picture. Turning
on lock luminance pixels works very well but then leaves trails/ghosting all over place on other real motion.
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Old 19th February 2003, 16:17   #4  |  Link
int 21h
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This looks alot like electrical interference to me... to me it just screams ground loop.

Try http://www.epanorama.net/documents/g...isolation.html for more general info...
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Old 19th February 2003, 19:06   #5  |  Link
Zep
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int 21h - thank you for the link

I checked many Hum Bar filters and I just purchased one for analog/digital CATV
and cable modems.

Lets see what a $70 gadget can do lol


Much better to try and fix it at the source than with filters after the fact
Besides this would help with watching TV straight up as well.

Now I hope UPS is fast for once lol

I will let everyone know if it worked once I get the thing and install it,


thx


Zep

Last edited by Zep; 20th February 2003 at 08:24.
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Old 6th March 2003, 01:48   #6  |  Link
Zep
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Will it came i installed it and $70 down the drain.

It was a jensen hum bar remover. worthless grrr.......

the only thing it MAYBE did was to soften the hum bars a little.
(I could be fooling myself via placebo effect lol)


oh well live and learn
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Old 6th March 2003, 01:52   #7  |  Link
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That's no good! At least you have time to return it
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Old 31st March 2003, 15:20   #8  |  Link
Zep
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problem solved!!!

Turns out my water pipes just are not so great for grounding modern tech.

So the cable tv guys came out and to my house and said i should install a ground
rod and get the cable off of the cold water pipe wich everything is grounded to in the
house as well as the electric company meter on outside of the house etc...

So i did. 8ft steel rod and sledge hammer and a little while later ground rod installed.
(Hard work hammering that sucker into the ground. needed to go in at least 6ft)

ran a wire from ground rod to cable tv in box on outside of house and presto!!!

rock solid pitcure on all channels

no need for over filtering now
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Old 2nd April 2003, 02:21   #9  |  Link
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So it was a ground loop problem Glad to hear you solved it.
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Old 2nd April 2003, 03:40   #10  |  Link
Zep
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yep it was


my guess is since everything in my house is grounded to the cold water
pipe that something is leaking voltage back and the water pipe just wasn't
good enough to ground it. Now with the cable TV on its own ground the picture
is rock solid and super sharp.

cool

might help my cable modem too which is also on the same cable
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