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Infocus X1 - any disadvantage to using DVD player zoom?

499 Views 8 Replies 2 Participants Last post by  mbaxter
This question is of a technical nature, regarding pixels and how they are mapped. Bob Williams might be the best man to answer it but I welcome all info.

I have an Infocus X1, a Panasonic XP30 DVD player, and a High Power 16:9 ratio screen. 1.78 and 1.85 movies look great on my screen because at these ratios, the masking is perfect. 2.35 movies have black borders top & bottom.

The Panasonic XP30 DVD player has a zoom function. When you play a 2.35 ratio DVD, and hit the zoom button, it expands it to 16:9 format. You lose some picture on the left & right side, but you regain proper masking, as the movie now fills the 16:9 screen perfectly. The only problem I can see is, to use the zoom feature, you have to set the XP30's output mode to "4:3 letterbox" or "4:3 pan & scan", and you have to also set the X1 to 4:3. Normally, I'd have both the DVD player and the X1 set to 16:9 output, but XP30 zoom function doesn't work if the output is set to 16:9.

Ok, so the point is, you can effectively convert a 2.35 DVD to 16:9 on the X1 by using zoom, as long as both the player & X1 are set to 4:3. Is there any technical disadvantage to doing this? Does it screw up the pixel mapping? Does it introduce some other error?

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You won't get your 1:1 pixel mapping that you're used to with 16:9 on both the player and the projector, which is the primary thing that I can see might bother you right off.

You have to decide how important that is to you for yourself though.

On the other hand, you won't be losing those pixels that the 1:1 mapping drops on the X1, they'll be scaled.

Watch some things both ways, and see which bothers you more - the letterbox bars, or the scaling.
I understand about the pixel to pixel mapping for 16:9 material, where the X1 chops off extra pixels from the top and sides to get 800x450. But what about 2.35 material? Do you end up with 800x360 pixels?
I think it depends on your source (both DVD and player) - for what it's worth, with the scenario described(4:3 settings), you'll be getting 480 lines of resolution, even though it will have to be scaled.

With digital projectors, the size of the pixels is always fixed - the implications aren't always obvious, but basically if you're projecting an image that fills your screen, you're always using the same number of pixels on the projector, regardless of the settings (16:9, 4:3, native)

Actually, in typing this out, it made me realize that you're likely going to have those 30 lines projected off the top/bottom of the screen because of the difference between 4:3 and 16:9.

In 16:9 mode, the X1 takes 480 lines, chops 30 of them and displays 450. Your scenario will be displaying a full 480 lines, so you're going to have part of your picture spill off the top, no?

Maybe my understanding of the 1:1 on the X1 is incorrect, but the best way to see would be to try it.
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Even if you set the X1 for 16:9 aspect, I don't think it does the 800x450 cropping if you play the DVD from an HTPC. I think it only does this when receiving a 480p or 480i signal. When you play a DVD from HTPC, the X1 is seeing 1024x768 or 800x600, not 480p or 480i. I wish Bob Williams were around...
If you go through HTPC (at a 4:3 ratio), you wouldn't set the X1 to 16:9 mode, you'd be doing all scaling in the HTPC.

My experience is that displaying a 4:3 image in 16:9 mode makes the X1 do all the scaling, so you'd be losing the benefits of HTPC, right?

If you're doing HTPC and 16:9 mode, you're going to want to set your HTPC resolution to 800x480(450?) or something similar, so that the X1 does the 1:1 pixel mapping
That makes sense. One thing I have noticed about the X1 is that I can display my 1024x768 desktop when the projector is in 16:9 mode. It just squashes everything vertically to fit. In other words, the X1 takes 1024x768 pixels and compresses it down to 800x450 pixels.

Which makes me wonder, what type of DVD playback would look better:

-Play DVD from the HTPC at 1024x768 in anamorphic mode (where the image is vertically stretched to fill the entire 4:3 area) and set the X1 to 16:9 so that it squeezes the incoming 1024x768 down to the correct aspect ratio.

-Play DVD from the HTPC at 1024x768 in widescreen mode (where the image is in the correct aspect ratio, with black bars top & bottom) and set the X1 to 4:3.

-Play DVD from the HTPC with the computer's native resolution set to 850x480 and have the X1 set to 16:9 mode. X1 would then crop this to 800x450.

With any of these three choices, you end up with an image that uses 800x450 pixels on the X1, but is scaled in different ways. It would be interesting to know which is "best".

This topic probably needs a thread in the HTPC forum as well.
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My guess (and that's all that it is - I don't have a HTPC setup) is that the third option would produce the best picture, since then the HTPC would be doing all the scaling, and the X1 would be doing none.

The other options would involve scaling in both places, though a third option of the PC at 800x600 and the X1 at 4:3 would probably look the same, and be easier to set up in the first place.
One thing I'm still a little unclear about, what is the actual native resolution of a DVD anyway? When you look at the properties for a DVD disk it always says 720x480. But then we hear about how the X1 crops down to 800x450. So what is the actual, original resolution of a DVD movie before any scaling or cropping?
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