Input Devices : Video Capture

Computers store videos as a sequence of still images called frames. These images are displayed quickly one after the other (rather like a flick-book) to create the illusion of a moving picture. Inputting a video into a computer is known as capturing the video. When you want to capture a video sequence you must tell the computer :

• Size : How big you want the image you capture to be. e.g. should it take up the whole screen, 1/2 the screen, 1/8th of the screen ... ?
• Frame Rate : How frequently the frames should be captured from the video.

If you want to capture large images you may have to settle for a slow frame rate which will make the captured video film look jittery. If you want a fast frame rate you may only be able to capture a small image size.

The three most common devices that can be used to capture videos are :

Video Digitiser	A video digitiser takes an image from a video camera or television and converts it so that it can be stored on a computer. Video digitisers can capture large images at fast frame rates. Many video digitisers now incorporate a television tuner so that television pictures can be captured directly.
Web Camera	A web camera captures video images for transmission over the Internet. Web cameras capture small images at a slow frame rate. They are cheap to buy.
Digital Camera	Most digital cameras that take photographs can also capture short video sequences.

GCSE ICT Companion 04 - (C) P Meakin 2004