Multiplication free scaled 8 x 8 DCT algorithm with 530 additions

The known idea of the rational DCT computations employs multiply approximation, where overall accuracy is not affected due to the rounding-off and truncations, which are intrinsic to the quantization process in the image/video compression. Besides higher computational efficiency, the multiplication free scheme can take advantage of the full-length processor word of 32-bit or newest 64-bit microprocessors, being applied to the packed pixel pairs. In this paper we propose the scaled DCT algorithm, that uses 30 `essential' multiplications by (root)2 and 64 `non-essential' by three constants (which are closed to 5, 3 and 2). The number of additions in the approximation version of the algorithm is considerably fewer than in the known multiplication free 8 X 8 DCT computational scheme. Other advantage of the algorithm is its symmetry, i.e. almost all the computational modules used in both forward and inverse DCT implementations are the same rather than transpositional ones. A performance of the software implementations of MJPEG codec for Pentium PC, based on the algorithm presented, as well as its applicability to the high resolution software-only playback in various video standards, is also discussed.