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Concerned about 720p conversion (1 Viewer)

May 21, 1999
I am about to buy an RP HDTV and have narrowed the choices down to the Sony KP46WT500 or the Toshiba 42HDX82. The issue now is 720p conversion. As I understand it, the Sony converts it to 480p while the Toshiba converts it to 1080i. On the other hand, the Toshiba converts 480p to 540p, which I understand is not necessarily better.

Anyone have experience with 720p converted to 480p and 1080i and care to share your thoughts? Is the conversion to 480P a significant loss? (There was a thread that touched on this but never really reached an answer.)

Ultimately, I could just wait and get the KP46WT510 which will supposedly convert 720p to 1080i; however, I'd rather not wait, for a number of reasons. (Anyone have any idea when it's supposed to be available, anyway?)

Also, does the 480p to 540p conversion significantly worse DVD picture quality? Does it improved the quality from a 480i source?

Allan Jayne

Senior HTF Member
Nov 1, 1998
Converting 720p to 480p definitely loses resolution and a lot of it, the result has vertical resolution no better than 480 lines.

A good 720p to 1080i conversion keeps most of the 720 lines of vertical resolution. A poor 720p to 1080i conversion cuts the vertical resolution to about 540 lines.

To do a good 720p to 1080i conversion, at the very least the odd 1080i fields (540 scan lines) must pick different scan lines from the 720p frames compared with what the even 1080i fields get. If the same scan lines or blends are chosen from the original 720p frames for both even and odd fields, the result is what you can call a 720p to 540p conversion.

Horizontal resolution quality can also vary, notably because every scaler has a "pixel width" which has to be at least 1280 to preserve all the horizontal detail. The pixel width is the number of pixels the incoming video is broken up into and does not have to be the same as the number of pixels in the incoming video format. All scalers work in the digital domain and so have to break up the incoming video into pixels going across.

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