Moving images presented as a sequence of static images (called "frames") representing snapshots of the scene, taken at regularly spaced time intervals, e.g. 50 frames per second. Apart from the frame rate, other important properties of a video are the resolution and colour depth of the individual images.Digital video data is typically stored and transmitted in a format like MPEG or H.264 that includes synchoronised sound. Unlike broadcast television, digital video on a computer or network uses compression. Compression is even more important for video that for static images due to the large amount of data involved in even a short video. Furthermore, compression allows video to be transmitted via a channel whose bandwidth is less than the raw data rate implied by the resolution and frame rate. This allows the recipient to start displaying the video before the transmission is complete, a process known as streaming. Compression can be relatively slow but decompression is done in real-time with the picture quality and frame rate varying with the processing power available and the size and scaling of the picture. There are many types of software for displaying video on computers including Windows Media Player from Microsoft, QuickTime from Apple Computer, DivX, VLC, RealPlayer and Acorn Computers' Replay.
Last updated: 2011-01-04