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727 posts

Ultimate Geek
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Topic # 67883 10-Sep-2010 00:44
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This is probably an easy one.
My 2-week old Panasonic 50V20 is very nice indeed, especially compared to the 25 year old 29" CRT it replaced.

I've not yet got the calibration adjusted to my liking, but that needs to wait a bit until I "run in" the panel.

One thing I've noticed, and being new to this area, can't be sure about.  Occasionally I'll see colour banding in areas where there is a very gradual colour gradient.  I'm assuming that's an artefact due to compression of the source material, rather than a problem with the TVs ability to display it.

I've noticed this mostly (perhaps exclusively) on Freeview-satellite, so it's possibly an issue with the nasty STB I'm using at the moment too.

What's the true story on this? 


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21910 posts

Uber Geek
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  Reply # 378430 10-Sep-2010 01:09
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Well, freeview satellite wont help with its crap bit-rate, but I have seen it many places - TV is still only 8 bit colour and that will show banding on most gradients since there is only 200ish levels of each colour.

Analog hookups can make it worse, and if you are using composite because you got a trademe special $80 junker, well you get what you pay for with those, they are barely fit to drive a 21" philips K9.


727 posts

Ultimate Geek
+1 received by user: 7

  Reply # 378523 10-Sep-2010 11:34
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Very good. I'm going to go with signal compression as the main cause until proven otherwise. I may generate a few more test gradients and see what I can see. I produced a PNG with gradients from white to each of the primaries across the image, and couldn't detect obvious banding - mind you, that was a 16-bit png.

The hook-up is a bit farcical at the moment I must admit, but with reason. The satellite signal goes to a very basic STB (on loan from a supplier until my Vu+ Duo arrives), composite from there to a VCR (believe it or not - but that's the only way I can record!), and composite again to the TV. I'd not be surprised if there were some weak links in that chain. Once I get the Vu+, it will be HDMI from there to the TV.


21910 posts

Uber Geek
+1 received by user: 4603


  Reply # 378624 10-Sep-2010 17:04
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No, you are using composite, that will be more of an issue than the compression for banding, the compression causes blocking where you will see squares of solid colour, not nice even bands of it.

Chances are the DAC in the settop is a 9 bit one, and the chroma decode on the TV will also have a low bit depth on it.

IMO TVs should pop up a warning when you select a composite input warning you that its crap from 50 years ago and telling you to use component at minimum, like computer monitors do when you give them a non native resolution.


727 posts

Ultimate Geek
+1 received by user: 7

  Reply # 378629 10-Sep-2010 17:41
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Righty-o then. I can look forward to great improvements with HDMI.

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