Audio encoder, audio decoder, method for encoding an audio information, method for decoding an audio information and computer program using a detection of a group of previously-decoded spectral values

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 a spectral value or a preprocessed version thereof, using a variable length codeword, wherein the arithmetic encoder is configured to map a spectral value, or a value of a most significant bitplane of a spectral value onto a code value,
• wherein the arithmetic encoder is configured to select a mapping rule describing a mapping of a spectral value, or of a most significant bitplane of a spectral value, onto a code value, in dependence on a context state;
• wherein the arithmetic encoder is configured to determine the current context state in dependence on a plurality of previously-encoded spectral values;
• wherein the arithmetic encoder is configured to detect a group of a plurality of previously-encoded spectral values, which fulfill, individually or taken together, a predetermined condition regarding their magnitudes, and to determine or modify the current context state in dependence on a result of the detection;
• wherein the arithmetic encoder is configured to set the current context state to be within a range of values which signals the detection of a group of a plurality of previously-encoded adjacent spectral values which fulfill, individually or taken together, a predetermined condition regarding their magnitudes, in response to the detection;
• and
• wherein the audio encoder is implemented using a hardware apparatus, or using a computer, or using 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;
• 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 representing a spectral value, or a most-significant bit-plane of a spectral value, in an encoded form onto a symbol code representing a spectral value, or a most-significant bit-plane of a spectral value, in a decoded form, in dependence on a context state;
• wherein the current context state is determined in dependence on a plurality of previously decoded spectral values;
• wherein a group of a plurality of previously-decoded spectral values, which fulfill, individually or taken together, a predetermined condition regarding their magnitudes is detected, and wherein the current context state is determined or modified in dependence on a result of the detection:
• and
• wherein the method comprises setting the current context state to be within a range of values which signals a detection of a group of a plurality of previously-decoded adjacent spectral values which fulfill, individually or taken together, a predetermined condition regarding their magnitudes, in response to the detection.

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 a spectral value, or a preprocessed version thereof, using a variable-length codeword, wherein a spectral value or a value of a most significant bitplane of a spectral value is mapped onto a code value;
• wherein a mapping rule describing a mapping of a spectral value, or of a most significant bitplane of a spectral value, onto a code value is selected in dependence on a context state;
• wherein a current context state is determined in dependence on a plurality of previously-encoded adjacent spectral values;
• wherein a group of a plurality of previously-encoded spectral values, which fulfill, individually or together, a predetermined condition regarding their magnitudes, is detected and the current context state is determined or modified in dependence on a result of the detection:
• and
• wherein the method comprises setting the current context state to be within a range of values which signals a detection of a group of a plurality of previously-encoded adjacent spectral values which fulfill, individually or taken together, a predetermined condition regarding their magnitudes, in response to the detection.

A non-transitory computer readable medium comprising 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;
• 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 representing a spectral value, or a most-significant bit-plane of a spectral value, in an encoded form onto a symbol code representing a spectral value, or a most-significant bit-plane of a spectral value, in a decoded form, in dependence on a context state,
• wherein the current context state is determined in dependence on a plurality of previously decoded spectral values,
• wherein a group of a plurality of previously-decoded spectral values, which fulfill, individually or taken together, a predetermined condition regarding their magnitudes is detected, and wherein the current context state is determined or modified in dependence on a result of the detection, and
• wherein the method comprises setting the current context state to be within a range of values which signals a detection of a group of a plurality of previously-decoded adjacent spectral values which fulfill, individually or taken together, a predetermined condition regarding their magnitudes, in response to the detection, when the program runs on a computer.

A non-transitory computer readable medium comprising 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 a spectral value, or a preprocessed version thereof, using a variable-length codeword, wherein a spectral value or a value of a most significant bitplane of a spectral value is mapped onto a code value;
• wherein a mapping rule describing a mapping of a spectral value, or of a most significant bitplane of a spectral value, onto a code value is selected in dependence on a context state;
• wherein a current context state is determined in dependence on a plurality of previously-encoded adjacent spectral values;
• wherein a group of a plurality of previously-encoded spectral values, which fulfill, individually or together, a predetermined condition regarding their magnitudes, is detected and the current context state is determined or modified in dependence on a result of the detection;
• and
• wherein the method comprises setting the current context state to be within a range of values which signals a detection of a group of a plurality of previously-encoded adjacent spectral values which fulfill, individually or taken together, a predetermined condition regarding their magnitudes, in response to the detection;
• when the program runs on a computer.