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Compression of sequences of images. Video compression algorithms use the fact that there are usually only small changes from one "frame" to the next so they only need to encode the starting frame and a sequence of differences between frames. This is known as "inter-frame coding" or "3D coding".
MPEG is a committee producing standards in this area and also the name of their standard algorithm. H.261 is another standard.
See also Integrated Information Technology, 3DO, full-motion video, Online Media.