Multimedia and video tools

Video and multimedia tools let a computer capture, edit, compress and play moving images together with their sound. Digital video is a sequence of still pictures, or frames, shown quickly enough to appear continuous, each frame being a grid of coloured pixels. Because raw video at this detail produces enormous amounts of data, compression is essential, and most video tools are concerned in some way with reducing this data while keeping the picture acceptable.

Compression is performed by a codec, the method that encodes and later decodes the video. Modern codecs save space in two main ways: they remove redundancy within each frame, much as still-image compression does, and they store only the differences between successive frames, since consecutive pictures are usually very similar. MPEG-4 is a widely used family of such standards, and DivX is a well-known implementation that became popular for storing films compactly on a computer. The compressed video and its audio are then wrapped together in a container file format that keeps the streams synchronised.

The tools themselves fall into a few groups. Editors arrange clips on a timeline, allowing cuts, transitions, titles and a separate soundtrack. Encoders and converters change video from one codec or container to another, for example to fit a target size or to play on a particular device. Players decode and display the result, while capture utilities bring video in from cameras or other sources. Much of this software runs on Windows and a good deal of it is available as freeware.

Frequently asked questions

Why does video need to be compressed?

Uncompressed video stores a full grid of pixels for every frame, producing huge files. Compression with a codec greatly reduces the size so video can be stored and shared practically.

What is the difference between a codec and a container?

A codec is the method used to compress the picture and sound, while a container is the file format that holds the compressed streams together and keeps them synchronised.

What is DivX?

DivX is a popular video codec based on MPEG-4 compression, used to store films and other video in relatively small files while keeping reasonable quality.