Folded VLSI architectures for discrete wavelet transforms

Two classes of novel folded VLSI architectures are presented. They are the word-level folded architecture and the bit-level folded or digit-serial architecture, for implementation of discrete wavelet transforms. In the word-level folded architecture, the computations of all wavelet levels are folded to the same low-pass and high-pass filters. The number of registers in the folded architecture is minimized by the use of generalized life time analysis. The advantage of the word-level folded architecture is low latency, and its drawbacks are increased hardware area, less than 100% hardware utilization, and complex routing and interconnection required by the converters used in this architecture. These drawbacks are eliminated in the alternate bit-level folded digit-serial architecture which requires simpler control circuits, routing, and interconnection, and achieves complete hardware utilization, at the expense of an increase in the system latency and some constraints on the wordlength. In latency-critical applications, the use of the word-level folded architecture is proposed. If latency is not so critical, the use of the bit-level digit-serial architecture is proposed