Method and apparatus for low bit rate encoding and decoding

An apparatus for low bit rate encoding, comprising:

• an important-spectrum component processing unit that extracts important-spectrum components from a spectral signal in a frequency domain and quantizes the important-spectrum components;
• a noise component processing unit that extracts residual-spectrum components other than the important-spectrum components from the spectral signal in the frequency domain, and calculates and quantizes noise levels for the residual-spectrum components;
• and
• a lossless encoding unit that losslessly encodes the important-spectrum components and the noise level and outputs encoded bitstreams.

A computer-readable storage medium encoded with processing instructions for causing a processor to execute a method of low bit rate encoding, the method comprising:

• transforming an input audio signal from the time domain to the frequency domain;
• extracting important-spectrum components from a spectral signal in a frequency domain, and quantizing the important-spectrum components;
• extracting residual-spectrum components other than the important-spectrum components from the spectral signal in the frequency domain, and calculating and quantizing a noise level of the residual-spectrum components;
• and
• encoding the quantized important-spectrum components and the quantized noise level losslessly, and outputting encoded bitstreams.

A method of low bit rate decoding, comprising:

• decoding input bitstreams into spectral signals losslessly;
• dequantizing quantized important-spectrum components of decoded spectral signals;
• dequantizing a noise level of additional information of the decoded spectral signals to generate noise components;
• combining the dequantized important-spectrum components and the noise components to be output as spectral signals in a frequency domain;
• and
• generating spectral signals in a time domain from the spectral signals in the frequency domain.

An apparatus for low bit rate decoding, comprising:

• a lossless decoding unit that decodes input bitstreams into spectral signals losslessly;
• an important-spectrum component dequantizing unit that dequantizes quantized important-spectrum components of the decoded spectral signals;
• a noise component processing unit that dequantizes a noise level of additional information of the decoded spectral signals to generate noise components;
• a spectrum combining unit that combines the dequantized important-spectrum components and the noise components to be output as spectral signals in a frequency domain;
• and
• a signal generating unit that generates spectral signals in a time domain from the spectral signals in the frequency domain.

A computer-readable storage medium encoded with processing instructions for causing a processor to execute a method of low bit rate decoding, comprising:

• decoding input bitstreams into spectral signals losslessly;
• dequantizing quantized important-spectrum components of decoded spectral signals;
• dequantizing a noise level of additional information of the decoded spectral signals to generate noise components;
• combining the dequantized important-spectrum components and the noise components to be output as spectral signals in a frequency domain;
• and
• generating spectral signals in a time domain from the spectral signals in the frequency domain.