Z-coder: a fast adaptive binary arithmetic coder
US6476740B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Dec 14, 2001 |
| Grant date | Nov 5, 2002 |
| Priority date | — |
| Expiry date | Dec 14, 2021 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03M7/4006
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A binary arithmetic coder and decoder provides improved coding accuracy due to improved probability estimation and adaptation. They also provide improved decoding speed through a “fast path” design wherein decoding of a most probable symbol requires few computational steps. Coded data represents data that is populated by more probable symbols (“MPS”) and less probable symbols (“LPS”). In an embodiment, a decoder receives a segment of the coded data as a binary fraction C. It defines a coding interval of possible values of C, the interval extending from a variable lower bound A to a constant upper bound 1. For each position in the decoded symbol string, the decoder computes a test value Z that subdivides the coding interval into sub-intervals according to the relative probabilities that an MPS or an LPS occurs in the position. A first sub-interval extends from the lower bound A to the test value z; the second sub-interval extending from the test value Z to 1. If C is greater than Z, the decoder emits an MPS for the current position in the decoded symbol string and sets the lower bound A to the test variable Z for use during decoding of the next po…
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