AUDIO ENCODER, AUDIO DECODER, METHOD FOR ENCODING AND AUDIO INFORMATION, METHOD FOR DECODING AN AUDIO INFORMATION AND COMPUTER PROGRAM USING A MODIFICATION OF A NUMBER REPRESENTATION OF A NUMERIC PREVIOUS CONTEXT VALUE.

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 also configured to modify a number representation of a numeric previous context value, describing a context state associated with one or more previously decoded spectral values, in dependence on a context subregion value, to obtain a number representation of a numeric current context value describing a context state associated with one or more spectral values to be decoded. An audio encoder uses a similar concept.