视频信号不过是传递视觉信息的一种方式，尽管存在很多差异和多种实现技术。视频信息可能来自VCR、 DVD播放器、本地广播的一个频道、有线电视、 卫星系统、Internet或者其它众多来源中的一种。
不变的是，视频信号要从一个设备传到另外一个设备。可能是从一个卫星机顶盒或者DVD播放器到电视，也可能是从机顶盒中的一个芯片到另一个芯片。尽管这看起来很简单，但是却有很多种要求， 因而有很多种实现方式。
模拟 VS. 数字
只到数年前，绝大多数视频设备是为模拟视频设计的， 数字视频仅限于专业应用，如视频编辑。由于成本持续下降， 现在普通消费者都在用数字视频。
Although there are many variations and implementation techniques, video signals are just a way of transfering visual information from one point to another. The information may be from a CCR, DVD player. a channel on a local broadcast, cable television,
or satellite system, the Internet, or one of many other sources.
Invariably, the video information must be transferred from one device to another. It could be from a satellite set-top box or DVD player to a television. Or it could be from one chip to another inside the satellite set-top box or television. Although it
seems simple, there are many different requirements, and therefore many different ways of doing it.
analog vs. digital
until a few years ago, most video equitment was designed for analog video. Digital video was confined to prefessional applications, such as video editing. The average comsumer now use digital video thanks to continuing falling costs. This trend has led to
the development of DVD players and recorders,
video data
Initially, video contained only gray scale (also called white-and-black) information.
while color broadcasts were being developed, attempts were made to transmit color video using analog RGB (red, green, blue) data.