Fast VLSI architecture for 8 x 8 2D DCT
Hughes de Perthuis, E. Bercovici, A. de Grandmaison, Mohamed Akil · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 1995
Discrete Cosine Transform (DCT) is one of the most popular lossy techniques used today in video compression schemes. It allows to take advantage of the properties of natural images. Indeed thanks to their continuity for small surfaces (typically 8 X 8 pixels), they ask for a more compact description in the frequential plan than in the spatial one. A coupled quantization also brings further compression gain as it is now possible to degrade more the high frequencies of the image to which human eye is less sensitive. The drawback is that DCT puts heavy stress on computational resources and can be a bottleneck to cheap real time video. We here introduce a VLSI architecture which combines excellent performance with a small die size as we use an algorithm which maps very well on silicon. Through a reordering of the samples, regularity and complexity of the computations involved are greatly improved. This allows to divide the process into two parallel parts, one for even samples, the other for odd ones. As the number of coefficients required is decreased, fixed multipliers can be used. A simple join of the two parts' results followed by a normalization merged with quantization will give 8 X 8 2D DCT after a total of 64 cycles.