Quality Switching for your Projector
By: Anthony D. Coppedge, CTS for Oxygen Ministries
You've found the perfect graphic to match the sermon series, the images work flawlessly with your worship songs and it looks great on your computer monitor. Oh, if it only looked that good on the projection screen.
This scenario is far more common than you might think. Your computer (PC or Mac) can create stunning images because of the excellent resolutions available. The trouble is, how do you quickly and cleanly change sources between computer, DVD or VHS and keep the quality the same at the projector?
Some churches have used scan converters to send their computer to a video mixer. Others have used a scaler to up-convert their video inputs. Which one is right for you?
BASIC ANSWER
There is always a loss in picture quality when down-converting (Scan Converting) from computer to video. An inexpensive scan converter (less than $1,000) is going to degrade the image severely, but a very good scan converter ($2,000 or higher) will offer only a slight loss of quality from the original computer image.
The original quality of the image is based upon the output resolution of the
computer and the resolution of the graphic. It is not uncommon to have 800 x 600, 1024x768 or even 1280 x 1024 as computer outputs. The higher these numbers (resolutions), the better the quality (nice and crisp, not blocky).
It is best to find out what the "native resolution" of the projector is
(1024 x 768 or 1208x1024), and send the exact same output
resolution from the computer to the projector. This will yield the best
looking-image for that projector, ensuring your graphics and text remain super sharp and crisp.
A scan converter comes in when you want to run a video signal to the
projector instead of the computer resolution signal. Why do this?
Let's assume you have a VCR, a DVD player and a computer that all need to be projected. To make "seamless" (no glitches, no blue or black screens in between) transitions between the DVD, VCR and computer, we need to 'agree' on a standard type of signal. The least expensive way to do this is with a video switcher.
Since computer signals are completely different from video signals, we need to make the computer common (scan convert) bringing it down to video. Now we can use a video mixer to dissolve, cut, wipe and key in video - because all three sources (in our example) are now video.
Another reason to use a scan converter is when your church is large enough to have a need for live video on the screens. We call this IMAG - Image MAGnification. The application of switching multiple live camera sources usually dictates the need for a video switcher.
In the above scenario, we lost resolution coming down from computer to video. But what if resolution is paramount? Glad you asked.
If you need pristine computer images and rarely use video (VHS, DVD or even a rare video camera shot), then a scaler is ideal. A scaler keeps the computer resolution perfect by sending the project a single computer resolution output. A scaler also up-converts any video signals to computer resolution. Just like with the video mixer example above, the scaler helps the various input types 'agree' on a standard type of signal, except this time it's a high-resolution computer signal.
ADVANCED ANSWER
In order to send the computer signal and video signals together (from our example
above) we can take a high-resolution Scan Converter to down-convert the
computer to video. The more expensive scan converters ($1,500 to $4,000)
look significantly better than an inexpensive scan converter. That's
because they actually process the information better and look for the best use of their algorithms to determine compression and anti-flicker methods.
Is it important to note that mixers/switchers like the Panasonic MX20, MX50 and Focus Enhancements MXPro all accept S-video and composite video. The Focus Enhancements MXDVPro includes two "firewire" (digital compressed) inputs. However, for video to look really crisp, component analog (Y,U,V; Y, Pb, Pr; RGsB) or SDI (Serial Digital Interface) is the preferred standard definition video input type.
Using a higher-end scan converter (with component or SDI outputs) will interface wonderfully and provide a very nice image. The cost differences, however, are tremendous. For example, the Ross Synergy 100 switcher is about (list) $20K. With a professional switcher like this, you can look just like the major TV networks in terms of 3D DVE's (Digital Video Effects), DSK's (down stream keys) and video processing.
The good quality Scalers ($2,000 - $6,000) will take video and up-convert very nicely to progressive scan images. In fact, you can now buy Scalers that have seamless switchers built right in that allow for cuts and cross-fades (dissolves) between computer and video sources...with all of the output at a fixed resolution to match the projector.
There are even dual and even triple scaler models on the market that make truly seamless input changes and multiple DSK or Picture-In-Picture effects possible. These high-end scaling units start at around $7,000 and can easily cost more than $20,000.
Scaling, therefore, is in fact the best quality image...but you usually won't be able to do all of the DVE's or DSK's like you can in a video switcher. The trade-off of quality versus flexibility must be decided by your unique application.
SUMMARY
You can use Scalers if you want the ultimate in quality pictures and don't need lots of mixing options. If you want to have that "TV look", however, you can use Scan Converters to down convert computers to match video.
Don't forget, the weakest link will kill the picture, so the highest level of video signal across the entire signal chain will yield better images no matter which methodology you choose. Again, remember, a $.99 cheapo connector just made that system worth $.99, so ensure that all of the pieces of the system are of sufficient quality.
Anthony D. Coppedge, CTS
Church Media Consultant
Anthony is heavily involved with Fellowship Church in Grapevine, TX. He has been speaking at technology conferences since 1995, and frequently contributes to magazines such as Church Business Magazine, Sound & Communications and Pro A/V, and is a featured columnist with Church Production Magazine and Lifeway.com
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