interlaced upconversion question (1 Viewer)

[Daniel Uri]

I'm having trouble with this one:
some HDTV internal scalers upconvert 480i to 480p while others upconvert to 1080i. It seems that some of these latter HDTV's even convert 480p input to 1080i before display. Which should theoretically (and actually) look better: the 480p (either via progressive DVD player input or HDTV scaler upconversion) or the 1080i??? Or is it a tie???

 

[Allan Jayne]

IMHO the most superb 480p display on an HDTV has alternate frames slightly staggered to look like 960i. In addition some blending of adjacent scan lines is done to smooth out diagonals further.
IMHO the visual difference between 1080i and 960i is very small especially if the original source was 480i or 480p. While the added scan lines of 1080i make the picture a bit smoother, the upconversion of 480p to 1080i involves duplicating and inserting scan lines every here and there. The latter can produce slight stretching of small text moving vertically.
If the source is 480i, converting to 1080i without converting to 480p first will cause significant degrading of quality.
480p is converted to 1080i in order to have just one scanning speed on the CRT's which in turn guarantees that only one set of convergence and geometry settings per aspect/zoom setting is needed.
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