Sequences of digital video images typically require vast amounts of electronic memory for storage, and occupy much bandwidth during transmission. Widely used image and video compression standards, such as JPEG and MPEG, use the two-dimensional discrete cosine transform (DCT) to achieve near-optimal compression of individual frames. This is done by decomposing the the frames into components of different spatial frequencies. This paper presents an extension of the DCT to the temporal dimension. It describes the implementation of a software based compression scheme which involves the computation of a three dimensional DCT of successive groups of eight frames. This compression scheme transforms the eight image frames into eight DCT frames with components of both spatial and temporal frequencies. The compression scheme was implemented and tested with standard MPEG video test sequences. It showed compression performance comparable to various MPEG implementations.
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