Abstract
This paper proposes an enhancement of the two levels dictionary based compression. The enhancement is based on optimizing the mapping tables overhead of the second level compression, usually variable length code, that used over the first level compression (the dictionary based one). The case study will be applied on `A-M' compression and will introduce the `A-M' dictionary version 2. This work guarantees the reduction of overhead from the second level compression up to 45% of the original mapping table. Besides, the use of `A-M' dictionary reduces the processing effort of recreation of dynamic dictionary. The idea is based on reducing the dictionary field of the mapping table by sorting, grouping, and then eliminating common parts (6 Most Significant Bits - MSB) of the dictionary words during compression, which is reconstructed back during decompression. The process is completely transparent with respect to the two levels of compression (dictionary and variable length) and can be applied not only for the `A-M' compression, but also for any other dictionary based compression technique.