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Guest Message by DevFuse

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why does my vip 622 pixelate?


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22 replies to this topic

#21 OFFLINE   johnsbin

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Posted 03 April 2007 - 03:40 PM

All 720p devices have to scale UP 1080i content. That's right - UP. That's because 1080i is not 1080, its 540x2. So you have several steps involved such as scaling up to 1080p then back down to 720p and do all this on the fly immediately. Your scaler is the source of your pixelation, on top of any artifact presented by the source.

I'm very open to source capture and encoding causing pixelation and other digital artifacts. You can plainly see it when the broadcaster cranks up the compression when the field goes to wide view versus when there is a closeup on a player or especially the commentators and they want to present the best picture possible.

But I'm not going to subscribe to "it has to be the source since I can't see how it could be any of my stuff" philosophy. Sounds too much like its always someone else's fault.

You said yourself ESPNs 720p looks better than someone else's 1080i on your equipment.

It will be nice when all points in the process are improved. We win!
ViP622, Optoma HD70, 90" screen

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#22 OFFLINE   rustamust

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Posted 03 April 2007 - 04:04 PM

Stretching to 1366 X 768 is not the same as scaling from 1080i.

Rustamust: What res output is your 622 set for? Is your Mits CRT RPTV? CRTs are a completely different animal.


622 is set for 1080i and its a CRT RPTV. I love it and the 622 together.

#23 OFFLINE   podder320

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Posted 03 April 2007 - 07:25 PM

I think this thread has a lot of different answers because the original poster wasn't clear in what he meant by "pixellation." That word can describe a large family of image quality problems. Without more information, everybody projects his own meaning onto it.

Here's an example from the recent NCAA tournament on CBS: when I watched games on KPIX-San Francisco from the Dish, there were often bad macroblocks across about 25% of the frame shortly after the arena's photo strobes went off. (Whole-image brightness changes require lots of bits in MPEG.) When I switched to my OTA antenna to watch the same game on the same channel (still through the 622), this never happened. Conclusion: it was introduced in the MPEG stream during the recompression / bit budgeting that was happening in Denver. I wrote to dishquality@echostar.com about it and got a form letter in reply about trading off MPEG quality vs. "increased customer choice and value" (that is, more channels).

Ragman, can you be that specific about what you're seeing, so we have some hope of offering an explanation?

For example: "I can record and play back the effect I'm seeing and it appears even on freeze-frames." That would eliminate motion artifacts in your display.

"I see large colored blocks that stay behind when things on the screen move. They clean themselves up after a second or two." That would suggest signal dropouts or transient errors in the data stream. It could be a problem in your rooftop dish or the cables running to your 622.

"There is a halo of bright dots around small, high-contrast objects." That's an MPEG compression artifact based on the bit budget that E* assigns to the channel you're watching. Not a defect per se, but if you turn down your TV's brightness and sharpness settings it might be less noticeable.

...any of those sound familiar? Or something else? Can we buy a vowel?




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