| 摘要 |
An efficient, fast-decoding, order-preserving, easily implementable, length-based (L-based) arithmetic coding method, apparatus, and manufacture for an m-ary alphabet {1 ,..., i ,..., m}is provided. The coding method combines recursive division of intervals on a number line into sub-intervals whose lengths are proportional to symbol probability and which are ordered in lexical order with the constraint that probabilities be estimated as negative powers of two (1/2, 1/4, 1/8, etc.). As a consequence, the advantageous preservation of lexical order and computational efficiency are both realized. High speed operation is achieved, because shifts take the place of multiplications. The coding apparatus in accordance with the invention preferably includes either a single decoding table to achieve fast decoding, or two decoding tables to achieve fast decoding as well as order preservation. The decoding process can conveniently be performed by constructing a decoding table for the C register. The C register is initialized with the leading bits of the codestring. The decoded symbol is the symbol i, i being the greatest integer that makes the C-register value greater than or equal to P(i). <IMAGE> |
