Re: What causes pixaliation on an HD set???
Most likely it's present in the source material arriving at the TV.
Next most likely reason is that the TV's processing is less sophisticated and cannot keep up with decoding (decompressing) the incoming source material.
ATSC HDTV and also hi-def DVD does not have all 1920 x 1080 pixels per frame stored and transmitted individually but rather various compression techniques are used to reduce the amount of aggregate data. Particularly with cable TV systems, the compression may be so great that it is impossible to recover all of the picture detail. In analog video, "compression" shows up first as smoothed over horizontal details aka reduced horizontal resolution. In digital video, compression deficiencies usually show up first as checkerboarded coarsesness here and there.
Video hints:
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