A new flexible architecture for variable length DCT targeting shape-adaptive transform

Shape-assisted block-based texture coding methodologies such as the shape-adaptive DCT raise the need for an architecture which can perform efficiently the transform of variable length N. This paper presents a 1D DCT architecture satisfying the given requirement in terms of scalability and modularity for 2⩽N⩽8. The architecture employs a canonical-signed-digit serial multiplication to reduce hardware resources and requires only one multiplier to perform the final scaling. A proposed algorithm searching for an optimal assignment of cosine factors leads to a resource saving of about 12% for the multiplication blocks if carry-ripple-adders are assumed to be used. Different area and speed requirements are possible since only feed-forward paths are involved and easily pipelined. The architecture represents a trade-off between time-recursive, fully modular but operation non-efficient structure and multiplication efficient but irregular and fixed-length implementation