Patent ID: 8914296

Claim:
An audio decoder for providing a decoded audio information on the basis of an encoded audio information, the audio decoder comprising: an arithmetic decoder for providing a plurality of decoded spectral values on the basis of an arithmetically encoded representation of the spectral values comprised in the encoded audio information; 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; wherein the arithmetic decoder is configured to select a mapping rule describing a mapping of a code value of the arithmetically encoded representation of spectral values representing one or more of the spectral values, or a most significant bit-plane of one or more of the spectral values, in an encoded form, onto a symbol code representing one or more of the spectral values, or a most significant bitplane of one or more of the spectral values, in a decoded form, in dependence on a context state described by a numeric current context value; wherein the arithmetic decoder is configured to determine the numeric current context value in dependence on a plurality of previously decoded spectral values; wherein 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 non-significant state values amongst the numeric context values, in order to select the mapping rule, wherein the arithmetic decoder is configured to evaluate the hash table for finding a hash table index value i for which the value ari_hash_m[i]>>8 is equal or greater than c, while, if the found hash table index value i is greater than 0, the value ari_hash_m[i−1]>>8 is lower than c; wherein the arithmetic decoder is configured to select the mapping rule which is determined by a probability model index which equals to ari_hash_m[i]&0xFF when ari_hash_m[i]>>8 is equal to c, or equals to ari_lookup_m[i] otherwise; wherein the hash table ari_hash_m is defined as given in FIGS. 22 ( 1 ), 22 ( 2 ), 22 ( 3 ) and 22 ( 4 ); and wherein the mapping table ari_lookup_m is defined as given in FIG. 21 ; wherein a mapping rule index value is individually associated to a numeric context value being a significant state value; and wherein ari_hash_m[i] designates an entry of the hash table ari_hash_m comprising hash table index value i; wherein the audio decoder is implemented as a hardware apparatus, or a computer, or a combination of a hardware apparatus and a computer.