HA1 - Task 1 Glossary

Pixel- A pixel or pel, is the smallest controllable element of a picture shown on the screen, the way the pixel is presented corresponds to it's physical coordinates. Each screen is divided into a matrix of thousands, sometimes even millions of pixels. Each individual pixel can only be one colour, because pixels are so small they blend together to make different shades or colours.

Resolution- Resolution refers to the clarity and sharpness of an image, this term is often used to describe monitors, printers and bit-mapped graphic images. More pixels are used up to make a more detailed image, the less pixels make up a less detailed image. Bitmap images are composed of pixels, the images resolution is the number of Pixels Per Inch (PPI) in the bitmap grid. Two main aspects to every bitmap image are, its size (width and height) and resolution (number of pixels per inch).

Screen ratios- The ratio of a screen or image describes the proportional relationship between the width and height. It is usually shown as two numbers that are separated by a colon, for example 16:9 and 4:3. For an x:y ratio,the size of the image doesn't matter, if the width is divided into x units of equal length and the height is measured using the same length unit, the height will be measured to be y units. The most popular ratio used today in the presentation of films in cinemas are 1.85:1 and 2.39:1. Two common video aspect ratios are 4:3 (1.22:1), which is the universal format of the 20^th century. And finally 16:9 (1.77:1) which is universally known for high-definition and European digital television. In still camera photography, the most common aspect ratios are 4:3, 3:2, and more recently being found in consumer cameras 16:9.

Frame rate- The human visual system can process 10 to 12 separate images per second, understanding each of them individually. Early silent films had a frame rate ranging from 14 to 24 frames per second, which created the sense of motion, but it was perceived as a jerky motion. When recording or playing a video, the frame rate tells us exactly how many frames per second. 

Video formats- A video format defines the way that video is recorded and stored, it usually specifies: Codec/compressor, frame rate, frame size, frame aspect ratio, pixel aspect ratio, scanning method (interlaced or progressive). The most common formats are DV, HDV and AVCHD. Type-based files like DV and HDV can be moved to a computer for editing with Firewire without any problems. Although file-based formats like AVCHD are already stored as files which then can be moved to a computer for editing via USB or a card reader.

Video compression- Codec is short for coder-decoder and describes the method which the video data is encoded into a files and then decoded when the file is played back. A lot of videos are compressed during encoding and so the terms codec and compressor are often used. Transcoding is the term used for the process of converting from one codec to another. Codecs can be Lossless, which means they do not throw any data away, or Lossy, which means that some data is lost during encoding. Lossless codecs are  of higher quality than lossy codecs, however they produce larger files.