How does Reality compare to MPEG-2 based editing systems?
A. MPEG-2 and JPEG are based on the same basic principles. They both use the DCT transform together with some sort of compression to reduce, sort, and pack the image into a smaller file size. Since this compression is accomplished on a frame by frame (or field by field) basis, it is known as interframe compression and the resulting images can be referred to as I frames. MPEG differs from JPEG in that it can additionally store only the differences between frames. MPEG calculates what has changed between frames, and stores only the changed data (intraframe compression). If this data that is stored only contains information for video moving forward in time, the data that is stored is called a P frame (predictive). If the data that is stored contains information for both forward video play, and reverse data, then it is called a B frame (bi-directional). While bi-directional or B frames are a bit self explanatory, the P frame name is a bit misleading. P frames do not contain predictive data
