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Grainy image on HD72

563 Views 3 Replies 3 Participants Last post by ZBoomer, May 9, 2006

BeerMoney

Discussion Starter · May 7, 2006

I recently bought the HD72 and set it up on a folding table as I have not decided on a screen yet. There are times when the image appears "grainy". The pixels seem larger than normal, almost as if the pj is focusing. Id does happen when a scene changes or the action is fast. I was watching the Lakers lose to Phoenix a little while ago and I noticed the graininess. Could this be an issue with the quality of the image from the source? I'm using the Discovery theater channel as my benchmark, That's an amazing channel.

What could be causing the graininess I see?

Any thouhgts would be appreciated.

Oh..I almost forgot. I have a Direct TVHD box connected the the pj via HDMI. The image is projected onto a light yellow wall and is about 100" diagonal.

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jrwhite

· #2 · May 7, 2006

Hi BeerMoney,

As you see the 'graininess' during scene cuts or fast moving scenes, it's most likely that you're seeing macroblocking. This is an MPEG2 artifact. This happens when the rapid motion action or rapid cuts within a scene causes the MPEG2 compression to ramp-up to keep within the bandwidth limits of the broadcast channel. Sometimes this is the originating signal itself, but, more often than not is the statistical multiplexing based re-compression done by service providers.

I'm sure your PJ is fine.

Jonathan

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BeerMoney

Discussion Starter · #3 · May 7, 2006

Thanks!

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ZBoomer

· #4 · May 9, 2006

The worst place to see if I've noticed is when light levels change dramatically in a scene. The compression algorithm can't keep up with the rapid changes.

For instance, if you catch a scene with flash bulbs going off rapidly, or a strobe light (dance floor scene) macroblocking is so bad you can barely freaking see the image.

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