AUDIO ENCODER, AUDIO DECODER, METHOD FOR ENCODING AND AUDIO INFORMATION, METHOD FOR DECODING AN AUDIO INFORMATION AND COMPUTER PROGRAM USING A HASH TABLE DESCRIBING BOTH SIGNIFICANT STATE VALUES AND INTERVAL BOUNDARIES

摘要

An audio decoder for providing a decoded audio information on the basis of an encoded audio information comprises an arithmetic decoder for providing a plurality of decoded spectral values on the basis of an arithmetically encoded representation of the spectral values, and a frequency-domain-to-time-domain converter for providing a time-domain audio representation using the decoded spectral values, in order to obtain the decoded audio information. The arithmetic decoder is configured to select a mapping rule describing a mapping of a code value onto a symbol code in dependence on a context state described by a numeric current context value. The arithmetic decoder is configured to determine the numeric current context value in dependence on a plurality of previously decoded spectral values. The arithmetic decoder is configured to evaluate a hash table, entries of which define both significant state values amongst the numeric context values and boundaries of intervals of numeric context values, in order to select the mapping rule. A mapping rule index value is individually associated to a numeric context value being a significant state value, and a common mapping rule index value is associated to different numeric context values laying within an interval bounded by interval boundaries. An audio encoded uses a similar concept.