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

An audio decoder for providing a decoded audio information on the basis of an encoded audio information is configured to obtain decoded spectral values on the basis of an encoded information representing the spectral values. The audio decoder is configured to jointly decode two or more most significant bits per spectral value on the 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. The audio decoder is configured to decode 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, such that 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. The audio decoder is configured to provide the decoded audio information using the spectral values. Modifications of the audio decoder are possible. An audio encoder is also described.