Average-sense optimality and competitive optimality for almost instantaneous VF codes
Average-sense optimality and competitive optimality for almost instantaneous VF codes
复制标题
几乎瞬时 VF 代码的平均感知最优性和竞争最优性
DOI：
10.1109/18.945241
复制
发表时间：
2001
期刊：
影响因子：
--
通讯作者：
H. Yokoo
中科院分区：
文献类型：
--
作者：
Hirosuke Yamamoto;H. Yokoo
研究了几乎瞬时变长变定长（AIVF）码C/sub AIVF/的单次编码和重复编码问题，C/sub AIVF/除了包含正常VF码C/sub PVF/外，还包含一些非正常VF码.本文给出了一种在C/sub AIVF/中构造平均意义最优（a-最优）AIVF码的算法。该算法还可以用于获得具有多个解析树的AIVF码，该AIVF码可以获得良好的重复编码性能。一般来说，如果A/spl ges/3，则用于单次编码的a-最优码和用于重复编码的好码在A进制情况下比通斯托尔（1967）码更有效，尽管它们在二进制情况下与通斯托尔码一致。竞争最优（c-最优）VF码也被认为是一次性编码，它表明，c-最优码并不总是存在于C/sub PVF/和C/sub AIVF/。当A=2或3时，当c-最优码存在时，通斯托尔码在C/sub PVF/中是c-最优的，而a-最优码在C/sub AIVF/中是c-最优的，但当A/spl ges/4时，a-最优码在C/sub AIVF/中并不总是c-最优的.
One-shot coding and repeated coding are considered for the class of almost instantaneous variable-to-fixed length (AIVF) codes, C/sub AIVF/, which includes some nonproper VF codes in addition to the class of proper VF codes, C/sub PVF/. An algorithm is given to construct the average-sense optimal (a-optimal) AIVF code in one-shot coding that attains the maximum average parse length in C/sub AIVF/. The algorithm can also be used to obtain an AIVF code with multiple parse trees, which can attain good performance for repeated coding. Generally, the a-optimal code for one-shot coding and the good code for repeated coding are more efficient than the Tunstall (1967) code in A-ary cases if A/spl ges/3 although they coincide with the Tunstall code in the binary case. The competitively optimal (c-optimal) VF code is also considered for one-shot coding, and it is shown that the c-optimal code does not always exist in C/sub PVF/ and in C/sub AIVF/. Furthermore, whenever the c-optimal code exists, the Tunstall code is c-optimal in C/sub PVF/ and the a-optimal code obtained by our algorithm is c-optimal in C/sub AIVF/ if A=2 or 3, but the a-optimal code is not always c-optimal in C/sub AIVF/ if A/spl ges/4.