HDTVs are built to display HD material, but SD television signals were designed for [older] CRT television sets. While most HDTVs have on-board signal processing for viewing normal television, it's often a compromise of quality and cost.
Dscaler is free software that turns a normal PC into a very high end video scaler. NTSC and PAL video are both delivered in interlaced format -- in a nutshell, half of each video frame is drawn at a time, NTSC drawing the screen 60 times each second, but delivering 30 frames per second. We'll use Dscaler to grab the incoming television signal, de-interlace it and scale it for our display. (In our case, a projector with a 103 inch wide screen.) While this How-To covers using windows software, die-hard linux fans should check out tvtime at http://tvtime.sourceforge.net
Update: ffdshow http://ffdshow.sourceforge.net. can make use of the dscaler dlls, but still runs on windows. [Thanks Larry]
For this project you will need:
- HTPC suitable computer running Windows 2000 or XP
- bt848 or bt878 based tv capture card
- Dscaler software from http://deinterlace.sourceforge.net
We'll be getting our video signal from either the TiVo or the laserdisc player. (Don't laugh too hard, certain movies can only be found in their original form on LD.) Both have S-video outputs, so we wanted a capture card with s-video input. Our ATI TV-Wonder PCI card has a single s-video input, so we use our surround receiver to switch between the TiVo and Laserdisc. Since the receiver handles all the sound switching, we don't use any of the sound features of the capture card.
Don't mistake the capture cards that work with Dscaler for the more expensive hardware encoding type. The type of card you need is usually available for under $50. There's a large number of manufacturers that make cards with right chip set. The basic Hauppauge WinTV or ATI TV-Wonder cards both work great. If you already have a card, you might want to check the supported cards list.
Dscaler doesn't need much CPU, but it does want a decent video card. The HTPC for the projector is a 2GHz Pentium 4 with a lowly GeForce4 mx AGP video card, and 1GB of ram running Windows XP.
Install your capture card and the latest drivers. Download Dscaler 4 (not 5). The installer is standard fare. When Dscaler is started for the first time, the General Hardware Setup screen will appear.
Select the appropriate options for your setup. If you're using fairly recent hardware, these probably won't make a big difference in performance.
In normal use, Dscaler will be running fullscreen. When it is, the usual File menus won't be visable. All of these menu items may be accessed by right clicking anywhere on the Dscaler window, fullscreen or not. Right click and select View, then Full Screen. Now Dscaler will run fullscreen every time it's started up.
To get set up Dscaler needs to know which capture card it's supposed to be using. Right click or use the file menu to select sources, and choose your card.
You may need to adjust the settings for the card you're using. Right click and choose "Bt Card" then "Setup Card / Tuner". If you're going to use the card to tune in cable or over the air signals, you may need to select the tuner chip that's on your card to get it working properly. For our setup, the default "No Tuner/Unknown" option worked fine.
Now the input for the video needs to be selected. Right click and choose Bt Card, then your input choice.
The aspect ratio of your video source needs to be set. Normal television is 1.33 or 4:3 format. Right click, choose AspectRatio, then 4:3 FullScreen.
Finally, the the aspect ratio of your display needs to be set. If you have a recent HDTV, it's probably 16:9 or 1.78. Those with projectors are dependent on their screen. Our screen is a 2.35:1 "Scope" size. If your video appears too wide or narrow, you may have your display aspect ratio set incorrectly.
Now it's time to enjoy the new higher quality video. The results on our setup were impressive. Be sure to try out the various de-interlace algorithms under the Deinterlace menu. Our favorite is Video (Greedy, High Motion).
How well does it work?
This pair of screen shots is from the deinterlace website. They are taken from a VHS copy of Titanic by by Mark Rejhon.
If you're interested in a dedicated hardware solution, DVDO hardware seems to have a good reputation. Check them out at http://www.dvdo.com/