Many times you want to mix a computer signal (eg a presentation or song words) with a set of video cameras and/or dvd players.

Video cameras etc, generally use Composite video (the little phono connector) and a computer will use higher resolution RGB or even DVI signals and connectors.

How can these be mixxed together, and how about overlaying the text from a computer over the top of the video cameras?

{mosˍfbˍdiscuss:2}

Under Construction, come back soon and there will be more!! 

Maybe you want to do something like this:

Here we have 2 signals, a camera and a PC . The actual output signal here is XGA, the video had to be resized and compressed to make it usable on the web. However you can see, that we can fade between the computer and the Video camera, and can also 'key' out the blue background to have an overlay effect where the Words appear over the top of the camera.

How did we do that?

The above video was simply done done by using a TV One 1T-C2-250, its name is a bit of a mouthful but it's a Video Switcher/Scaler! It simply takes a Computer signal and a Composite (or S-Video) signal and outputs as a computer type signal. -This output ensures highest quality, as the PC's words are not being re-scaled. There are buttons on the front to control the unit, there is also an Infra-red remote control etc.... you can find out more about this on our Product Information page, or see the spec in the shop.

Taking it further...

You can easily add to the above setup by using a Composite Video Mixer, such as the Edirol V4 ... This would let you have 4 composite video sources - eg 4 cameras, and mix them as well as then fading to the PC, or overlaying the Text from the PC whilst still mixing between cameras. Of course, if 4 cameras is too much, then you can connect a VCR or a DVD player instead. (Click the image to the right for a full screen view) 

As the output of the TV One switcher is XGA, you'll ensure great quality all the way through to your projector.

What about Scan Converters?

In these examples we are using a 'Scaler' to scale UP the Composite video sources to XGA, the other method would be to Scale DOWN the computer signal into Composite video - a device to do this would be called a Scan Converter.

The reason we don't want to use a Scan Converter, is because the computer signal will loose quality. The Signal resolution of XGA is 1024x768, and Composite Video (PAL) is 720x576. If you work out the number of pixels, that's 786,432 verse 414,720 - so XGA has nearly twice the number of pixels.

In the blue/orange diagram to the right, we see that the original XGA gets converted to PAL and then back up again to XGA. You may think this if fine and that the quality would be the same, but this isn't the case...The original XGA is converted down to PAL by the scan converter - this will loose quality. Depending on the quality (and price!) of the scan converter the quality difference will vary. The LCD in a Video Projector are normally XGA resolution - and so the projector will scale up the PAL video up to XGA - this won't increase the quality, just the size, and so will make the lower quality image more noticeable. Find out more on our Scan Converters page .

Under Construction, come back soon and there will be more!!

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