S-Video cable carries luminance or brightness (Y) and colour (C) information separately, rather than as a composite signal (in which all brightness and colour information is blended together). When transmitted together, colour and brightness information must be extracted from one another by the television, often resulting in picture artefacts such as 'dot crawl' and colour bleeding. When using a DVD player, S-Video cables are a must and provide a dramatic improvement in picture quality over composite RCA connections, and should be used if component video connection is not possible.