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Dave,


If you feed the LCD projector an interlaced signal - its internal scaler will have to convert it to progressive.


A lot of internal scalers leave much to be desired in terms of de-interlacing. Many can't do inverse telecine [3:2 pulldown]

properly - and you end up with jagged diagonals.


The projector's internal scaler tries to merge the 2 interlaced fields - but, as above - it might not do it

correctly.
 

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Discussion Starter · #3 ·
Thank you.


So basically, it is the poor interlacing of the projector.


So, if your projector has good de-interlacing (better than your P-scan DVD player), then you would be better off sending it an interlaced signal vs. a progressive signal?
 

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But don't you get a problem when sending a progressive signal that is not at the projector's native resolution? Say you send a 480p signal from a DVD player to a projector with 720p native resolution. That means the 480i signal is scaled from 480i to 480p then sent to the projector. The 480p signal is converted back to 480i and scaled up to 720p. Can't all the conversions degrade the signal? Am I wrong in there somewhere?
 

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Usually, no.


The projector does not convert 480p to 480i then scale. The projector either takes 480i and deinterlaces to 480p or takes 480p directly and then scales to it's native resolution. Scaling (interpolating) isn't done with interlaced signals since you're missing half the fields. Scaling a progressive signal is pretty straightforward (simple math) and is usually done quite well. If a fault is to be found it's usually the poor deinterlacing circuits of the projector or the fact that the analog signal must be converted to digital before deinterlacing. On a DVD player the deinterlacing is done in the digital domain before being converted into analog so the quality can be very high.


Basically, you need to determine which has the better deinterlacer, the projector or the progressive player. If the projector is better send it 480i. If the player, 480p.


Of course, if you have a DVI capable display get a DVI output player (like the new V, Inc Bravo). Then the first, last and only digital to analog conversion will be your retina. All deinterlacing and scaling will be done digitally without noise or errors.


[edited for typo]
 

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Thanks rusty, just thought I'd ask to be sure. I'm sending my TV3 scaler a 480i signal and letting it do the scaling until I buy a DVI DVD player. Then it's a straight digital path the the projector.
 

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Quote:
Originally posted by Toxarch
But don't you get a problem when sending a progressive signal that is not at the projector's native resolution? Say you send a 480p signal from a DVD player to a projector with 720p native resolution. That means the 480i signal is scaled from 480i to 480p then sent to the projector. The 480p signal is converted back to 480i and scaled up to 720p. Can't all the conversions degrade the signal? Am I wrong in there somewhere?
The internal scaler has to do 2 things - deinterlace an interlaced signal, and secondly scale to the native resolution

of the digital panel.


BOTH those operations have to be done - the question is which hardware is best at doing it.


The stumbling block is usually the de-interlace step. That's where internal scalers usually fall down - because

it is a trickier step, especially on telecine [3:2 pulldown] material.


If you have a progressive DVD player that is smarter at deinterlacing than the projector's internal scaler - then

let it do the deinterlace; i.e convert 480i to 480p.


Then the projector's scaler will scale the 480p to the native resolution of the chip - say 720p.


Once the signal is deinterlaced, there's no reason to go back to 480i. The internal scaler simply scales 480p to

720p.


As above, both operations have to be done, and there's no superfluous transformations, such as converting back to

480i as you state above.
 
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