The length of the index may vary. For example, the first index can be represented by 1 bit, the 2nd and 3rd by 2 bits each, the 4th, 5th, 6th, and 7th by 3 bits each, and so on. The above example, as most other illustrative examples in the literature, does not result in real compression. Actually, more bits are used to represent the indices than the original data. This is because the length of the input data in the example is too short.
Decompression works in the reverse fashion.
The decoder knows that the last symbol of the most recent dictionary entry is the first symbol of the next parse block. This knowledge is used to resolve possible conflict in the decoder. This loss of optimality is most likely due to the finite dictionary size. V. References A. Gersho and R. M. Gray, Vector Quantization and Signal Compression . Proceedings of the IRE , Vol.