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Discussion Starter · #1 ·
Correct me if I am wrong, but is the LT150 cinema mode sorta like the Wega 16:9 enhanced mode? In other words, do you get the full resolution of anamorphic DVDs with this mode? If not, what's the benefit?


thanks!

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[This message has been edited by Chuckster (edited 10-08-2001).]
 

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Chuckster,

I'll take a crack at it. The Full DVD 480 lines are scaled to 576 in the LT150. So, yes you get them all. The squeeze is done in the PJ and the lt150 scaler doesn't have to work so hard (1.2 vs 1.6) so less artifacts.


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Thanks for clearing this up for me as well. I see why it uses 576 lines (1024/576 = 1.78 = 16:9).


But, I'm still wondering about something that I've alluded to elsewhere but still don't know the answer to. If I plug in a DVD player and combine the LT150's native mode with the cinema mode, what do I get? I don't suppose there's any chance that it would result in a 854x480 resolution, would it? I would think that this would be best as it would be a 16:9 mode which didn't have to scale the vertical resolution (though it would still scale the horizontal resolution from 720 -> 854).


If not, can what I'm suggesting be accomplished through other means (HTPC, RP91, etc.)? Or, is what I'm suggesting a terrible idea due to other issues (e.g. - decreased brightness)?


Scott

 

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As far as I know, Cinema Mode on the NEC projectors is implemented via the internal projector A/D converter and scaler circuitry. Any time you engage such extra image processing, you are trading off image quality. The usual most optimum scheme is to always drive a 4:3 image to the VGA input, and have the projector set at [email protected] for film and [email protected] for video source, "Native" resolution, and "Natural 1" gamma. Handle the aspect ratio changes and letterboxing, etc. outboard in a scaler/line doubler or HTPC.


The only time I would use "Cinema Mode" is when for some reason I had to accept 16:9 source aspect ratio to this 4:3 display aspect ratio projector.


Gary
 

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Gary, thanks for the advice, and don't take this the wrong way, but that still doesn't help me get it. It's probably just because I'm thick-headed, but I guess I want some more factual data.


I realize that the cinema mode is scaling. My question is: If you run a DVD at native mode and cinema mode (if such a thing is possible) will it scale the image horizontally while leaving the vertical resolution alone (at 480p)?


If so, I would think this should produce a pretty nice image. But since you've brought the HTPC into the discussion, let me ask another question:


Just what is an HTPC doing that is so wonderful as compared to what the internal scaler of the LT150. This is probably a very complex question, so feel free to "dumb it down" a bit and I'll ask more detailed questions to follow.


Let me tell you where I'm coming from here (in case my initial reply here didn't make it clear)...I'm working under the assumption (probably wrong) that scaling is bad, except when you can scale by a whole number (e.g. - scale 480 to 960). Why not just leave a 480p signal at 480p? Why scale it up to 576 if you don't have to? Granted, by scaling, you're using up more of the LCD (probably wrong term to use since we're talking about DLPs here) which gives more brightness. But, I would think that the negatives of scaling artifacts would outweigh the advantage in brightness. Please school me.


Scott
 

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The difference between cinema mode (whatever that is) and what the Sony does, is that the Sony takes its "dots" and pushes them closer together.


The LT150 cannot make its pixels closer together. It can only use fewer dots,


This is why so many people are wanting an anamorphic lens that will take all the resolution the LT150 can make, and squeeze it together. That will be similar to what the Sony's accomplish with their "squeeze".


I will have to wait, since my anamorphic lens was delivered leaking. I kind of expected that, since Fed-ex had totally lost it for a few days.


You're right that scaling to even intervals is easier. One difference between the onboard scalers and a software scaler in an HTPC is that the people who write a scalar program for your HTPC have full access to your PC, and can say, "It will run better with XXX Meg of ram," etc.


The people who implement the scaling in the NEC have a dedicated chip. It was designed for that purpose, but does not have the capacity of your PC.


Also, the software scalars can be much more easily updated. A deadline to produce a product does not set it in stone.


There are other considerations, too. But mainly it is due to the available resources.


Best Regards,

Doug




[This message has been edited by shodoug (edited 10-08-2001).]
 

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Scott,


Scaling is always bad, even when you are using an integer scaling factor such as 2, not because it's inherently bad, but because of the required A/D conversion needed prior to scaling. It doesn't matter if you feed the projector composite video, S-video, component video, or RGB(VGA) - these are all analog signals and require A/D conversion prior to digital scaling.


"Native" resolution and scaling are mutually exclusive, any time you invoke the aspect ratio mode of the projector you engage the A/D and scaler circuits. The result will necessarily be worse than passing a clean 4:3 signal in native XGA resolution. Note that it doesn't matter if you use the "Aspect Ratio" remote button, the projector menus, or serial port commands, the result is the same - the A/D and scaler circuits are invoked.


The real advantage to the HTPC is it is a relatively inexpensive way to scale to projector native resolution with a very good quality scaling engine and D/A converter - the circuits built into the PC video board. The video boards have been evolving like mad because of competition (mostly video gaming), but the least expensive video board has a much better scaler than the one in the projector.


Remember that the LT150 is a presentation projector optimized for the VGA input, the video inputs are "extra features" which got implemented as inexpensively as possible. The very best video display occurs when you process the video in an external processor such as a HTPC or a high quality external scaler capable of XGA resolution.


There is one projector which offers no scaling - the Plus HE-3100, aka "The Piano", which behaves exactly as you desire, using the center portion of it's display for displaying DVDs in 480p/16:9 mode on the center 480 pixel rows, and displaying SVGA/4:3 otherwise. Other very expensive projectors made by Sharp, Faroudja, etc. are designed with much higher quality scaling engines and A/D converters - but such features demand premium pricing.


Driving an inexpensive projector like the LT-150 at it's native 1024X768 resolution with the correct 4:3 aspect ratio image, is the best way to get max performance from the very good light engine and avoid the effects of the inexpensive built-in converter and scaler circuits.


Gary
 

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So when playing back an anamorphic disc, which of the

following configuration yields a better image? Does it depend on your DVD player?


(1) DVD output = 16:9 and LT150 = cinema mode

(2) DVD output = 4:3 and LT150 = normal mode

 

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You are indeed best off sending the digital projector its native rate, and avoiding using its scaling features if possible.


HOWEVER, you should really NEVER set your DVD player to the 4:3 output screen setting. If you do this, it will downconvert anamorphic disks by converting it into a 4:3 image, dropping resolution in the way. The extra resolution contained on anamorphic disks will never get out of the DVD player and into the display device.
 

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Hopefully I can shed some light on this issue...


I have the LT-150, the RP-91 DVD player, a Panamorph, a Samsung HDTV tuner, an HTPC, and a DaLite High Power screen (96"x72").


After much fiddling, I have to agree with those who have said that the LT-150 with a HTPC is MUCH better than a near perfect 480p signal. For best 16x9/anamorphic DVD performance from a standalone DVD player, the DVD player should be set for a 16:9 display and the LT-150 set to Cinema. I must also reiterate what the other posts say: DO NOT SET THE DVD PLAYER TO 4:3. You will be killing your resolution. This is for 16:9 material only however. If you want the big 4:3 image of 4:3 material, then by all means set the player to 4:3.


My observations of DVD 480p from the RP-91 (set to 16:9) with the LT-150:


Maybe it makes perfect sense, but the Panamorph with the LT-150 set to Normal versus no Panny and set to Cinema only results in a brighter image, not a smoother one. The 'jaggies' are more pronounced when expanding 480p into 768. This is obviously what's needed for the Panny to work with 16:9 material (tall skinny people) or for a full size 4:3 image of 4:3 material. But then when it's squeezed back to 16:9 with the Panny, the image looks nearly identical to the Cinema mode (576 lines) with no Panny. In essence it's squeezing the bigger jaggies back down to where they would have been in Cinema mode w/o the Panny.


I would almost call the scaler in the NEC more of a line 'replicator'. It seems to display mostly pairs of duplicate lines with no apparent signs of interpolation or smoothing between physical panel lines. This is what would seem to account for the jaggies getting 'bigger' when taking 480p into 768 versus into 576, and it would also seem to explain my subjective observation that there's no smoothness benefit to the Panamorph with the LT-150 and a standalone DVD player. And yes, before anybody jumps the gun, I do have the RP-91 in progressive mode (another pretty blue light on the front panel...).


I will say at this point that my HTPC with a Radeon VE and the Panny is AWESOME. And there IS a substantial improvement in smoothness using the Panny with the PC-scaled image of a 16:9 anamorphic DVD (tall skinny, 768 lines active) versus a letterboxed 16:9 and no Panny (576 lines active). It is bettered only by 720p out of my HDTV box. The PBS demo loops are breathtaking, not just awesome.


To sum up:


The best standalone DVD player performance with the LT-150 is having the DVD player in 16:9 mode and the NEC in Cinema.


The best DVD picture is from a source that can supply the native panel resolution of 768 lines (HTPC or external scaler). There has been some discussion here and at Tom LaStrange's site that a 1,024x576 desktop from a HTPC can yield a better picture ( http://lastrange.com/ht/lt150.shtml ). I have not tried this since it would not work properly with my Panamorph.


Hope this helps, and sorry for the long post...


On another note, I carried my Panny in to Pecar's (my trusty local HT store) to have a look at it with the new Sharp 9000 and 2.35:1 material. Wow is all I can say. The Sharp has a resize button on the remote that will vertically stretch 2.35 to fill the screen. Very cool.


- Dieter
 

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Let me clarify what I said earlier. When using a HTPC, absolutely you want to set the software DVD player output to 1024X768, 4:3 aspect ratio, and set the projector for "Native" resolution and "Natural 1" gamma. This remains true whether or not the source DVD is anamorphic or letterboxed.


I believe Jim Ferguson's remark above is correct for standalone DVD players - it's absolutely the best way if you have no choice but to use the internal projector scaler. The only circumstances where it is not true is when you use the HTPC or high quality scaler with XGA resolution output - where you are bypassing such projector circuitry. The final signal driven to the LCD panels is always 1024X768, whether or not the top or bottom portions are muted off with the projector scaler "Aspect Ratio" function. It's better to scale an anamorphic source in the HTPC or external XGA scaler than in the projector, for the reasons mentioned before.


Gary
 
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