Arithmetic coding encoder and decoder system
US4905297A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 18, 1988 |
| Grant date | Feb 27, 1990 |
| Priority date | — |
| Expiry date | Nov 18, 2008 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06T9/005
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
Apparatus and method for compressing and de-compressing binary decision data by arithmetic coding and decoding wherein the estimated probability Qe of the less probable of the two decision events, or outcomes, adapts as decisions are successively encoded. To facilitate coding computations, an augend value A for the current number line interval is held to approximate one by renormalizing A whenever it becomes less than a prescribed minimum AMIN. When A is renormalized, the value of Qe is up-dated. The renormalization of A and up-dating of Qe are preferably based on a single-bit test. Also, each Qe value is preferably specified as a 12-bit value having the least significant bit set to 1 and having no more than four other bits set to 1. The number of Qe values in the 1/4 to 1/2 probability range is enhanced to improve coding efficiency. A decision coding parameter of preferably six bits indicates the sense of the more probable symbol (MPS) in one bit and identifies a corresponding Qe value with the remaining five bits. In addition to probability adaptation, the present invention discloses an allocation of bits in a code stream register in which preferably two spacer bits are inserted …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.