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Panasonic 46PZ80 - shimmering effect on horizontal lines

Bruce Morrison

Active Member
Hi, I hope someone can explain this to me as I'm not particularly technical.

I've recently bought the Panasonic 46PZ80 (UK model) and I've been playing a standard DVD (upscaled to 1080p) that has a static scene including a window shutter in the distance with closely spaced horizontal slats. This in effect was an area of alternating light and dark horizontal lines close together. Although the shot was absolutely static, I noticed that there was constant "shimmering" over this area of the image.

I know that a similar kind of shimmering typically occurs on CRT TVs displaying an interlaced image - but I was quite surprised to see it on a plasma panel, which of course is displaying progressively.

What is this effect known as, and why does it occur on a progressive display? Would this kind of shimmering be reduced at all by Blu-ray?

Any answers or comments very much appreciated - thanks.
 

sandos

Standard Member
DVDs are interlaced. Even if your dvd-player deinterlaces does not mean it does it perfectly, and I doubt it is even possible to do it perfectly, although a static scene should in theory be easy.

Blu-ray should not produce this, afaik. Not with 24p material for sure.
 

Bruce Morrison

Active Member
DVDs are interlaced. Even if your dvd-player deinterlaces does not mean it does it perfectly, and I doubt it is even possible to do it perfectly, although a static scene should in theory be easy.

Blu-ray should not produce this, afaik. Not with 24p material for sure.


Hmmm...my DVD player is a progressive scan upscaling player (the Denon 2930), which has the Optix Reon scaling/deinterlacing chip. It's certainly supposed to do a very good job of upscaling (and also deinterlacing as far as I know).

I'm currently taking the signal out of the player as 1080p. Maybe I should try taking it out as 1080i and allow the TV to do the deinterlacing. I'll give it a try, but somehow I'm not sure that it's going to make that much difference. I'll report back!

As the scene is static, I'm still wondering whether the effect I'm seeing is something different from the kind of shimmering that would be produced by an interlaced display (which I think is usually apparent only with motion).

Thanks for your response anyway.
 

Bruce Morrison

Active Member
Another point that's just occurred to me - I think I'm still running the TV with the overscan option switched on (as this is recommended for ordinary viewing of broadcasts). For DVDs, this is presumably causing a pixel re-mapping, which could possibly cause this sort of effect (?). So I'll try it this evening with overscan off and see if there's any improvement.
 

Bruce Morrison

Active Member
Well I've tried switching off the overscan and also letting the TV do the deinterlacing. Neither has made any difference - I'm still getting this very noticeable shimmering over an area of closely spaced light and dark horizontal bars in a static scene.

The DVD concerned is actually a filmed opera performance, dating from 1999. It ought to be good quality, but I'm now coming to the tentative conclusion that it is simply a poorly mastered DVD - possibly with a low bitrate.

However, if anyone can suggest other causes of this shimmering effect on a 1080p plasma panel, I'd still be very interested to hear your thoughts.
 

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