Comments on: Novel full-search schemes for speeding up image coding using vector quantization

Vector quantization (VQ) is a well-known signal compression method. In the framework of VQ, fast search method is one of the key issues because it is the time bottleneck for practical VQ applications. Based on the law-of-cosines and the triangle inequality, the previous work [C.C. Chang, I.C. Lin, Novel full-search schemes for speeding up image coding using vector quantization, Real-Time Imaging 10 (2004) 95–102] has proposed a very efficient fast search method for VQ encoding. However, there still exist a large computational redundancy in its Scheme 1 and some incorrect expressions in its Scheme 2. This paper aims at improving these two issues further by (1) proposing a more efficient implementation method for the Scheme 1 and (2) rewiring the Scheme 2 for correctness. Meanwhile, a mathematical analysis on computational complexity and the experimental results are given to show the effectiveness of the proposed implementation method of the Scheme 1 in this paper.