Audio encoders, audio decoders, methods and computer programs adapting an encoding and decoding of least significant bits

An audio encoder for providing encoded audio information on a basis of input audio information,

• wherein the audio encoder is configured to acquire spectral values representing an audio content of the input audio information,
• wherein the audio encoder is configured to encode at least a plurality of the spectral values, in order to an acquire encoded information representing the spectral values,
• wherein the audio encoder is configured to jointly encode two or more most significant bits per spectral value, to acquire respective symbol codes for a set of spectral values using an arithmetic encoding,
• wherein a respective symbol code represents two or more most significant bits per spectral value for one or more spectral values,
• wherein the audio encoder is configured to encode one or more least significant bits associated with one or more of the spectral values in dependence on a bit budget available,
• such that one or more least significant bits associated with one or more of the spectral values are encoded, while no least significant bits are encoded for one or more other spectral values for which two or more most significant bits are encoded and which comprise more bits than the two or more most significant bits;
• wherein the audio encoder is configured to provide the encoded audio information using the encoded information representing the spectral values,
• wherein the audio encoder is configured to be switchable between
• a first mode in which an encoding of non-zero spectral values in a higher frequency range is omitted in case that an available bit budget is used up by an encoding of spectral values in a lower frequency range and in which least significant bits are encoded for all spectral values for which one or more most significant bits are encoded and which comprise more bits than the one or more most significant bits, and
• a second mode in which one or more least significant bits associated with one or more of the spectral values are encoded, while no least significant bits are encoded for one or more other spectral values for which one or more most significant bits are encoded and which comprise more bits than the one or more most significant bits, and
• wherein the audio encoder is configured to provide a bitstream flag which is comprised in the encoded audio information in order to indicate whether the audio encoder operates in the first mode or in the second mode.

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

• acquiring decoded spectral values on a basis of encoded information representing the spectral values;
• jointly decoding two or more most significant bits per spectral value on a basis of respective symbol codes for a set of spectral values using an arithmetic decoding, wherein a respective symbol code represents two or more most significant bits per spectral value for one or more spectral values;
• decoding one or more least significant bits associated with one or more of the spectral values in dependence on how much least significant bit information is available;
• and
• providing the decoded audio information using the spectral values,
• wherein the method further comprises operating in
• a first mode in which a decoding of spectral values in a higher frequency range is omitted in response to a signaling from an encoder and in which least significant bits are decoded for all spectral values for which one or more most significant bits are decoded and which comprise more bits than the one or more most significant bits, or
• a second mode in which one or more least significant bits associated with one or more of the spectral values are decoded, while no least significant bits are decoded for one or more other spectral values for which one or more most significant bits are decoded and which comprise more bits than the one or more most significant bits, and
• wherein the method further comprises evaluating a bitstream flag which is comprised in the encoded audio information in order to decide whether to operate in the first mode or in the second mode.

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

• acquiring spectral values representing an audio content of the input audio information;
• encoding at least a plurality of the spectral values, in order to acquire an encoded information representing the spectral values;
• jointly encoding two or more most significant bits per spectral value, to acquire respective symbol codes for a set of spectral values, using an arithmetic encoding, wherein a respective symbol code represents two or more most significant bits per spectral value for one or more spectral values;
• encoding one or more least significant bits associated with one or more of the spectral values in dependence on a bit budget available;
• and
• providing the encoded audio information using the encoded information representing the spectral values,
• wherein the method further comprises operating in
• a first mode in which an encoding of non-zero spectral values in a higher frequency range is omitted in case that an available bit budget is used up by an encoding of spectral values in a lower frequency range and in which least significant bits are encoded for all spectral values for which one or more most significant bits are encoded and which comprise more bits than the one or more most significant bits, or
• a second mode in which one or more least significant bits associated with one or more of the spectral values are encoded, while no least significant bits are encoded for one or more other spectral values for which one or more most significant bits are encoded and which comprise more bits than the one or more most significant bits, and
• wherein the method further comprises providing a bitstream flag which is comprised in the encoded audio information in order to indicate whether the first mode or the second mode is used.

A non-transitory digital storage medium having a computer program stored thereon to perform, when the computer program is run by a computer, a method for providing decoded audio information on a basis of encoded audio information, the method comprising:

• acquiring decoded spectral values on a basis of encoded information representing the spectral values,
• jointly decoding two or more most significant bits per spectral value on a basis of respective symbol codes for a set of spectral values using an arithmetic decoding, wherein a respective symbol code represents two or more most significant bits per spectral value for one or more spectral values;
• decoding one or more least significant bits associated with one or more of the spectral values in dependence on how much least significant bit information is available and
• providing the decoded audio information using the spectral values,
• wherein the method further comprises operating in
• a first mode in which a decoding of spectral values in a higher frequency range is omitted in response to a signaling from the encoder and in which least significant bits are decoded for all spectral values for which one or more most significant bits are decoded and which comprise more bits than the one or more most significant bits, or
• a second mode in which one or more least significant bits associated with one or more of the spectral values are decoded, while no least significant bits are decoded for one or more other spectral values for which one or more most significant bits are decoded and which comprise more bits than the one or more most significant bits, and
• wherein the method further comprises evaluating a bitstream flag which is comprised in the encoded audio information in order to decide whether to operate in the first mode or in the second mode.

A non-transitory digital storage medium having a computer program stored thereon to perform, when the computer program is run by a computer, a method for providing encoded audio information on a basis of input audio information, the method comprising:

• acquiring spectral values representing an audio content of the input audio information;
• encoding at least a plurality of the spectral values, in order to acquire ag encoded information representing the spectral values;
• jointly encoding two or more most significant bits per spectral value, to acquire respective symbol codes for a set of spectral values, using an arithmetic encoding, wherein a respective symbol code represents two or more most significant bits per spectral value for one or more spectral values;
• encoding one or more least significant bits associated with one or more of the spectral values in dependence on a bit budget available;
• and
• providing the encoded audio information using the encoded information representing the spectral values,
• wherein the method further comprises operating in
• a first mode in which an encoding of non-zero spectral values in a higher frequency range is omitted in case that an available bit budget is used up by an encoding of spectral values in a lower frequency range and in which least significant bits are encoded for all spectral values for which one or more most significant bits are encoded and which comprise more bits than the one or more most significant bits, or
• a second mode in which one or more least significant bits associated with one or more of the spectral values are encoded, while no least significant bits are encoded for one or more other spectral values for which one or more most significant bits are encoded and which comprise more bits than the one or more most significant bits, and
• wherein the method further comprises providing a bitstream flag which is comprised in the encoded audio information in order to indicate whether the first mode or the second mode is used.