This document will focus on how to use a 'normal' 4:3 LCD/DLP data projector as high-end widescreen video projector for DVD.
There are 3 problems to overcome:
Unlike 3 tube CRT projectors, LCD/DLP projectors are not flexible since they have a fixed array of pixels and work best on a certain vertical frequency which matches the internal processing speed (usually 60Hz).
Data projectors use square pixels, just like the computer screen. Video however is not defined as square pixel (see CCIR-601).
Data projectors are 4:3, just like the computer screen. There are only a few 16:9 projectors, for instance the Sony VPL-VW10HT.
Use the s-video output of a 'normal' DVD player and connect it to the s-video input of the projector. The projector will deinterlace the s-video signal and scale the picture to full screen. The result is horrible and this is definitely *NOT* the way to do it!
Use a DVD player with progressive output (component YUV) and connect it to the component input of your projector. The problem is that most data projectors do not have a component input and only accept RGB anyway. Besides this problem most data projectors also not support the 480p mode and do not know how to scale the image properly. This solution is the way to go if you have a CRT projector.
Use a computer based DVD player and use the standard vga output. This way the computer can scale the image and the projector only has to display it without modification. This is something any projector can do!
Obviously we go for solution 3, but how do we solve the scaling problem? Before we proceed I want to explain my theory on this subject first. There are 2 way to scale the image:
Horizontal scaling: There are different devices to playback video and all of them they have different number of horizontal resolution: vcr (vhs) 220, s-vhs 400, laserdisc 425 and dvd >500. It seems that the horizontal resolution of video is not really hard defined. This conclusion also follows from the fact that the color component in the broadcast signal has half the resolution of the brightness component. This is also used in the mpeg compression, also known as 4:2:2 (YUV).
Vertical scaling: The number of vertical image lines is for each recording device the same (480 for NTSC and 576 for PAL), and is a hard fixed number. Also there is no such thing as half resolution for color in a vertical way, as is the case for horizontal.
Since we have to scale the video in some way, to convert from non square video pixels to square computer pixels,
the best way is only to scale horizontally and keep the number of vertical lines constant.
This way the image quality well be the highest, with the highest possible sharpness and most accurate colors.
Using the full screen modes PC DVD players offer, the image will be scaled both horizontally and vertically,
for instance from 720x480 to 800x450 in case of anamorphic NTSC.
To overcome this problem I have made some special scaling routines in Remote Selector, initially only for my own use.
These functions currently (Remote Selector V1.77) apply for the Mpact2 Entertainment Center, PowerDVD and WinDVD:
| Function | Video Window Resolution |
|---|---|
| NTSC 4:3 | 640 x 480 |
| NTSC 16:9 | 852 x 480 |
| NTSC LTBX | 852 x 640 |
| PAL 4:3 | 768 x 576 |
| PAL 16:9 | 1024 x 576 |
| PAL LTBX | 1024 x 768 |
The rest of the Windows desktop is covered with black topmost windows.
A seperate function 'Remove Borders' is added to get rid of these windows, in case you need to access the Windows desktop again.
If you enable the 'keep aspectratio' option of your DVD player program, you only need the 16:9 and LTBX functions.
The ini file of Remote Selector also contains 2 special settings in the [Preferences] section:
From the above it is obvious that a 800x600 projector is best to play NTSC DVD's.
The only small disadvantage is that you loose 26 pixels on either side of the picture (keeping 800x480 which is 15:9),
but I think that this is no problem, since a tv would hide exactly the same.
A 1024x768 projector is best for PAL DVD's, and always needs to upscale NTSC DVD's to use maximum resolution of your projector.
Make sure you enable the 'Force Weave' of your DVD player program.
Somehow movies are not encoded progressive on a PAL DVD and the player program will choose BOB mode when set to 'auto detect'.
The last thing you have to take care of is the refresh rate of your video card.
I have an Infocus LP-400 DLP projector, and it only works properly with 60Hz, otherwise the image shudders on movements.
This means that I have to set the refresh rate of my video card also to 60Hz.
Unfortunately the Mpact2 card does not work properly on 60Hz, so you have to keep it on 72Hz.
You will have to experiment a little with this. If 72Hz works properly, this is the setting to go for. Otherwise it will probably have to be 60Hz.