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tech Q: how do 720p panels handle 1080i in projectors?

1134 Views 5 Replies 4 Participants Last post by  voicecoils
720p projectors are popular in this forum area, especially single chip 1280x720p dlp and 3 chip lcd machines.

I'd like to understand what 720p projectors are doing with an incoming 1080i signal.

I can see how the horizontal lines would accommodate 1080i as only 540p are needed at any one time, but how are the vertical lines handled ie 1920->1280?

Or does the projector scale 1920x540p (discarding the other field lines) to 1280x720p?

Or does the projector take 1920x1080i, deinterlace it to 1920x1080p and then scale 1080p -> 720p.

Do different 720p projectors do this differently?
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They all do it differently, obviously the last way is the best.
I believe most still use the older methods and are not properly deinterlacing 1080i to 1080p and then downrezzing to 720p. That process is what is being highly touted by the current round of high end VP's or projectors coming bundled with them.

Just an FYI- 720p projectors are popular in this forum because you are in the "Under $3,000 USD MSRP" as soon as 1080p hits this price I assure you 1080p projectors will be more popular.
What does "properly" deinterlacing 1080i to 1080p mean?
prop·er (prpr)


1. Characterized by appropriateness or suitability; fitting: the proper knife for cutting bread; not a proper moment for a joke.

2. Called for by rules or conventions; correct: the proper form for a business letter.

3. Strictly following rules or conventions, especially in social behavior; seemly: a proper lady; a proper gentleman.


a. Belonging to one; own: restored to his proper shape by the magician.

b. Characteristically belonging to the being or thing in question; peculiar: an optical effect proper to fluids.

5. Being within the strictly limited sense, as of a term designating something: the town proper, excluding the suburbs.

6. Ecclesiastical For use in the liturgy of a particular feast or season of the year.

7. Mathematics Of or relating to a subset of a given set when the set has at least one element not in the subset.

8. Worthy of the name; true: wanted a proper dinner, not just a snack.

9. Out-and-out; thorough: a proper whipping.


Thoroughly: beat the eggs good and proper.

n. Ecclesiastical also Proper

The parts of the liturgy that vary according to the particular feast or season of the year.


[Middle English propre, from Old French, from Latin proprius; see per1 in Indo-European roots.]


proper·ly adv.

proper·ness n.

I meant number 1.

Seriously ,I just meant they create the 540 line scenario vs creating the true 1080p frame.
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So the only safe way to know you are getting the best image possible from your source is to let an outboard scaler, who's scaling/deinterlacing algorithms you trust, scale everything to 1280x720p?

I guess that's really only the iscan VP30/VP50...$3k ouch
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