2. Overview of MPEG video compression principles

Video encoders fall into two main categories: encoders for production, where access to each frame is important, particularly for editing, and encoders for broadcast, where the emphasis is on linear video playback. The MPEG family has been designed to meet both needs. It therefore uses two main technologies: spatial compression and temporal compression:

• Intra" spatial compression aims to reduce data redundancy in the image (figure 1 );

• Inter" temporal compression aims to encode only what changes from one frame to the next (figure