Digital video is basically a large series of compressed digital images. The compression also contains a temporal dimension instead of only a spatial dimension, like in the case of still image compression standards (JPEG etc.). This means that video images are compressed also by comparing images with each other and determining which areas of an image can be reused in encoding the following or previous images. This way only part of an image has to be encoded and the rest can be taken from the other images. A large compression ratio can be achieved specially in scenes, where there is very little motion. If you want to know more about basic digital image concepts just CLICK HERE. The digital video world differs quite a lot from its analog counterpart. The main difference is that a digital video contains a huge amount of discrete number values. Most of the digital video data is usually converted from analog video sources and today the main use of digital video standards is therefore in transmitting the digitized version of analog video through satellites and cables. In the future the video world is expected to turn all-digital.

The digital video standards, like MPEG-1, AVI and QuickTime, are almost always lossy compression standards. The reason is simple : transmitting an uncompressed digitized PAL-signal would require about 166 Mbit/s (=720 * 576 * 25 frames/s * 16 bits)! Analog VHS video quality can be achieved with a little over 1 Mbit/s using MPEG-1 and TV-studio quality with 5 - 10 Mbit/s using MPEG-2. This offers a major advantage: One analog satellite PAL-channel can be converted to a digital transmission channel with a bitrate of 36 Mbit/s and therefore, depending of quality, 4-10 digital video channels can be tranmitted instead of one analog. Digital video will make the same kind of improvements in video quality that digital audio (CDs) made to audio quality.

The digital video is also suitable for use in computers and computer networks, like the Internet. If there is no data tranmission errors, the quality is always the same, no matter how many copies are made. The use of digital video in PCs is nowadays hugely increasing as the digital video technology improves.