Audio encoder, audio decoder, method for encoding and audio information, method for decoding an audio information and computer program using an optimized hash table

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 acquire 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 bit-plane 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 hash table ari_hash_m is defined as given in FIGS. 22(1), 22(2), 22(3) and 22(4);
• wherein the arithmetic decoder is configured to evaluate the hash table, to determine whether the numeric current context value is identical to a table context value described by an entry of the hash table or to determine an interval described by entries of the hash table within which the numeric current context value lies, and to derive a mapping rule index value describing a selected mapping rule in dependence on a result of the evaluation,
• wherein a mapping rule index value is individually associated to a numeric context value being a significant state value;
• wheren the audio decoder is implemented as a hardware apparatus, or a computer, or a combination of a hardware apparatus and a computer.

A method for providing a decoded audio information on the basis of an encoded audio information, the method comprising:

• 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
• providing a time-domain audio representation using the decoded spectral values, in order to acquire the decoded audio information;
• wherein providing the plurality of decoded spectral values comprises selecting 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-plan 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 bit-plane 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 numeric current context value is determined in dependence on a plurality of previously decoded spectral values;
• wherein 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, is evaluated in order to select the mapping rule,
• wherein the hash table is evaluated using the algorithm
• i = i_min;
• while ((i_max−i_min)>1)
• {
• i = i_min+((i_max−i_min)/2);
• j = ari_hash_m[i];
• if (c<(j>>8))
• i_max = i;
• else if (c>(j>>8))
• i_min=i;
• else
• return(j&0xFF);
• }
• return ari_lookup_m[i_max];
• wherein c designates a variable representing the numeric current context value or a scaled version thereof;
• wherein i is a variable describing a current hash table index value;
• wherein i_min is a variable initialized to designate a hash table index value of a first entry of the hash table and selectively updated in dependence on a comparison between c and (j>>8);
• wherein the condition “c<(j>>8)” defines that a state value described by the variable c is smaller than a state value described by the table entry ari_hash_m[i];
• wherein “j&0xFF” describes a mapping rule index value described by the table entry ari_hash_m[i];
• wherein i_max is a variable initialized to designate a hash table index value of a last entry of the hash table and selectively updated in dependence on a comparison between c and (j>>8);
• wherein the condition “c>(j>>8)” defines that a state value described by the variable c is larger than a state value described by the table entry ari_hash_m[i];
• wherein j is a variable;
• wherein the return value designates an index pki of a probability model, and is a mapping rule index value;
• wherein ari_hash_m designates the hash table;
• wherein ari_hash_m[i] designates an entry of the hash table ari_hash_m comprising hash table index value i;
• wherein ari_lookup_m designates a mapping table;
• wherein ari_lookup_m[i_max] designates an entry of the mapping table ari_lookup_m comprising mapping table index value i_max;
• wherein the hash table ari_hash_m is defined as given in FIGS. 22(1), 22(2), 22(3), 22(4);
• and
• wherein the mapping table ari_lookup_m is defined as given in FIG. 21;
• and
• wherein a mapping rule index value is individually associated to a numeric context value being a significant state value.

A method for providing a decoded audio information on the basis of an encoded audio information, the method comprising:

• 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
• providing a time-domain audio representation using the decoded spectral values, in order to acquire the decoded audio information;
• wherein providing a plurality of decoded spectral values comprises selecting 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 bit-plane 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 numeric current context value is determined in dependence on a plurality of previously decoded spectral values;
• wherein 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, is evaluated in order to select the mapping rule,
• wherein the hash table ari_hash_m is defined as given in FIGS. 22(1), 22(2), 22(3) and 22(4);
• wherein the hash table is evaluated to determine whether the numeric current context value is identical to a table context value described by an entry of the hash table or to determine an interval described by entries of the hash table within which the numeric current context value lies, and
• wherein a mapping rule index value describing a selected mapping rule is derived in dependence on a result of the evaluation;
• wherein a mapping rule index value is individually associated to a numeric context value being a significant state value.

An audio encoder for providing an encoded audio information on the basis of an input audio information, the audio encoder comprising:

• an energy-compacting time-domain-to-frequency-domain converter for providing a frequency-domain audio representation on the basis of a time-domain representation of the input audio information, such that the frequency-domain audio representation comprises a set of spectral values;
• and
• an arithmetic encoder configured to encode one or more of the spectral values or a preprocessed version thereof using a variable length codeword, wherein the arithmetic encoder is configured to map one or more of the spectral values, or a value of a most significant bit-plane of one or more of the spectral values, onto a code value,
• wherein the arithmetic encoder is configured to select a mapping rule describing a mapping of the one or more spectral values, or of a most significant bit-plane of the one or more spectral values, onto the code value, in dependence on a context state described by a numeric current context value;
• and
• wherein the arithmetic encoder is configured to determine the numeric current context value in dependence on a plurality of previously-encoded spectral values;
• and
• wherein the arithmetic encoder 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 hash table ari_hash_m is defined as given in FIGS. 22(1), 22(2), 22(3) and 22(4);
• wherein the arithmetic encoder is configured to evaluate the hash table, to determine whether the numeric current context value is identical to a table context value described by an entry of the hash table or to determine an interval described by entries of the hash table within which the numeric current context value lies, and to derive a mapping rule index value describing a selected mapping rule in dependence on a result of the evaluation;
• wherein a mapping rule index value is individually associated to a numeric context value being a significant state value;
• wherein the audio encoder is implemented as a hardware apparatus, or a computer, or a combination of a hardware apparatus and a computer.

A method for providing an encoded audio information on the basis of an input audio information, the method comprising:

• providing a frequency-domain audio representation on the basis of a time-domain representation of the input audio information using an energy-compacting time-domain-to-frequency-domain conversion, such that the frequency-domain audio representation comprises a set of spectral values;
• and
• arithmetically encoding one or more of the spectral values or a preprocessed version thereof using a variable length codeword, wherein one or more of the spectral values, or a value of a most significant bit-plane of one or more of the spectral values, is mapped onto a code value,
• wherein a mapping rule describing a mapping of one or more of the spectral values, or of a most significant bit-plane of one or more of the spectral values, onto a code value, is selected in dependence on a context state described by a numeric current context value;
• and
• wherein the numeric current context value is determined in dependence on a plurality of previously-encoded spectral values;
• and
• wherein 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, is evaluated in order to select the mapping rule,
• 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 hash table is evaluated, to determine whether the numeric current context value is identical to a table context value described by an entry of the hash table or to determine an interval described by entries of the hash table within which the numeric current context value lies, and wherein a mapping rule index value describing a selected mapping rule is derived in dependence on a result of the evaluation;
• wherein a mapping rule index value is individually associated to a numeric context value being a significant state value.

A non-transitory computer-readable medium having stored thereon a computer program for performing the method for providing a decoded audio information on the basis of an encoded audio information, the method comprising:

• 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
• providing a time-domain audio representation using the decoded spectral values, in order to acquire the decoded audio information;
• wherein providing a plurality of decoded spectral values comprises selecting 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 bit-plane 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 numeric current context value is determined in dependence on a plurality of previously decoded spectral values;
• wherein 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, is evaluated in order to select the mapping rule,
• wherein the hash table ari_hash_m is defined as given in FIGS. 22(1), 22(2), 22(3) and 22(4);
• wherein the hash table is evaluated to determine whether the numeric current context value is identical to a table context value described by an entry of the hash table or to determine an interval described by entries of the hash table within which the numeric current context value lies, and
• wherein a mapping rule index value describing a selected mapping rule is derived in dependence on a result of the evaluation;
• wherein a mapping rule index value is individually associated to a numeric context value being a significant state value,
• when the computer program runs on a computer.

A non-transitory computer-readable medium having stored thereon a computer program for performing the method for providing an encoded audio information on the basis of an input audio information, the method comprising:

• providing a frequency-domain audio representation on the basis of a time-domain representation of the input audio information using an energy-compacting time-domain-to-frequency-domain conversion, such that the frequency-domain audio representation comprises a set of spectral values;
• and
• arithmetically encoding one or more of the spectral values or a preprocessed version thereof using a variable length codeword, wherein one or more of the spectral values, or a value of a most significant bit-plane of one or more of the spectral values, is mapped onto a code value,
• wherein a mapping rule describing a mapping of one or more of the spectral values, or of a most significant bit-plane of one or more of the spectral values, onto a code value, is selected in dependence on a context state described by a numeric current context value;
• and
• wherein the numeric current context value is determined in dependence on a plurality of previously-encoded spectral values;
• and
• wherein 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, is evaluated in order to select the mapping rule,
• 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 hash table is evaluated, to determine whether the numeric current context value is identical to a table context value described by an entry of the hash table or to determine an interval described by entries of the hash table within which the numeric current context value lies, and wherein a mapping rule index value describing a selected mapping rule is derived in dependence on a result of the evaluation;
• wherein a mapping rule index value is individually associated to a numeric context value being a significant state value,
• when the computer program runs on a computer.