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Discussion Starter · #1 ·
I have a 5030HD. When there are very fast motions on screen, the pixels suddenly bundle into quarter inch squares. Is this because the response time of the individual pixel is not fast enough? Can anyone please explain this?
 

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Discussion Starter · #3 ·
I receive all my signals from TWC in NYC. Now you mentioned it, and I think you are right. I do not recall seeing the squares with DVDs. But shouldn't cable and satelite subscrbers notice them too?
 

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Do you have Digital Cable with TWC. You should not see the compression blocks on fast moving material on your lower (analog) channels.


Yes - all digital cable and satellite subscribers will see them depending on the programming and compression.
 

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Yes Chris, I do have digital cable and these compression blocks are visible in other non-HD channels also. Are you implying that OTA transmissons will not have this effect? Is this effect mentioned in other threads? But then you can't really notice them 5-6 feet away.


ws
 

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I don't believe compression artifacts show up as 1/4 inch blocks.

You are seeing pixelization due to insufficient bandwidth

or signal strength into or out of the set top box. I have both

satellite and digital cable and digital cable shows no compression

artifacts that I can see - compared to DirecTV. From reading

similar reports in the local HDTV programming threads, what

you describe sounds like a provider or infrastructure problem.


larry
 

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I am not talking about just your HD channels having this but any digital channel. OTA transmissions can have this as well - as PooperScooper said if there is not enough bandwidth.


As far as not seeing them - on digital cable your lower channels (at least the first 20-30) are not normally digital but still analog stations. These stations shouldn't show any of the blocking.
 

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The artifact you are describing is called "macroblocks" and occurs with MPEG compression (used by digital cable, satellite, DVD, and OTA digital/HD TV) with lower bitrate and fast motion in a scene. DVDs are able to eliminate or reduce the effect because they use a relatively high bitrate for their resolution and also have the advantage of multipass off-line encoding to use a higher bitrate on the fast motion scenes and less on the slow-motion scenes. The others unfortunately use real-time encoding (one pass) and can't vary the bitrate a lot and also tend to use lower bitrates then is required for higher quality fast motion scenes. The amount of such artifacts will vary with each, some stations and networks use more compression and lower bitrate than others. The WB network for example uses 14Mb/sec compared to 19Mb/sec on other networks for HD programming and so you get a lot of macroblocks on fast motion scenes on WB's HD shows like Smallville.
 

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Yes, Thumberboy, thanks. Macroblock is the term I never remember.

In the WB case (I don't get WB HD), then everybody

sees the problem, yes? With an infrastructure problem and

good "source", some people see the macroblocks and others

don't. eg. When Comcast rolled out INHD, some people local

to me were complaining of macroblocks and such, and I had

no problems at all during the time frame they we stating.


I very rarely see any macroblocking on HD - OTA and cable.

When I do it's apparent it's a "glitch".


larry
 
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