Adaptive Bitwidth Compression for Low Power Video Memory Design

Vasily MOSHNYAGA  

Publication
IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E85-A   No.4   pp.797-803
Publication Date: 2002/04/01
Online ISSN: 
DOI: 
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section of Selected Papers from the 14th Workshop on Circuits and Systems in Karuizawa)
Category: 
Keyword: 
bit-compression,  low power,  video memory,  adaptive technique,  

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Summary: 
Due to large capacitance, high access ratio and wide access bitwidth, frame memory is one of the most energy consuming devices in modern video encoders. This paper proposes a new architectural technique to reduce energy dissipation of frame memory through adaptive bitwith compression. Unlike related approaches, the technique utilizes the fixed order of memory accesses and data correlation of video sequences, by dynamically adjusting the memory bitwidth to the number of bits changed per pixel. Instead of treating the data bits independently, we group the most significant bits together, activating the corresponding group of bit-lines adaptively to data variation. The approach is not restricted to the specific bit-patterns nor depends on the storage phase. It works equally well on read and write accesses, as well as during precharging. Simulations show that using this method we can reduce the total energy consumption of the frame memory cell array by 20% without affecting the picture quality. The implementation scheme is simple yet compact.