Audio-Encoding/Decoding Method and System of Lattice-Type Vector Quantizing

An audio decoding method of lattice vector quantization, comprising:

• decoding coded bits of each amplitude envelope in a to-be-decoded bit steam to obtain an amplitude envelope quantization exponent of each coding sub-band;
• performing bit allocation on each coding sub-band, and performing decoding, inverse quantization and inverse normalization of pyramid lattice vector quantization on a low bit coding sub-band to obtain frequency domain coefficients of the low bit coding sub-band, and performing decoding, inverse quantization and inverse normalization of sphere lattice vector quantization on a high bit coding sub-band to obtain frequency domain coefficients of the high bit coding sub-band;
• wherein, the low bit coding sub-band is a coding sub-band in which a number of bits allocated to one frequency domain coefficient is less than a preset threshold value, the high bit coding sub-band is a coding sub-band in which a number of bits allocated to one frequency domain coefficient is greater than or equal to the preset threshold value;
• and
• performing an inverse modified discrete cosine transform (IMDCT) on the frequency domain coefficients for which noise filling has been performed to obtain a final audio signal.

An audio coding system of lattice vector quantization, comprising:

• a modified discrete cosine transform (MDCT) unit, an amplitude envelope calculating unit, an amplitude envelope quantizing and coding unit, a bit allocating unit, a normalization processing unit, a classification lattice vector quantizing and coding unit and a bit stream multiplexer;
• wherein,
• the MDCT unit is configured to perform the MDCT on an audio signal to generate frequency domain coefficients;
• the amplitude envelope calculating unit is connected to the MDCT unit and configured to divide the frequency domain coefficients generated by the MDCT unit into a plurality of coding sub-bands, and calculate an amplitude envelope value of each coding sub-band;
• the amplitude envelope quantizing and coding unit is connected to the amplitude envelope calculating unit and configured to quantize and code the amplitude envelope value of each coding sub-band to generate coded bits of the amplitude envelope of each coding sub-band;
• the bit allocating unit is connected to the amplitude envelope quantizing and coding unit and configured to perform bit allocation to obtain a number of coded bits allocated to each frequency domain coefficient in each coding sub-band;
• the normalization processing unit is connected to the MDCT unit and configured to use a quantization amplitude envelope value of the coding sub-band to perform normalization processing on all the frequency domain coefficients in each coding sub-band;
• the classification lattice vector quantizing and coding unit is connected to the normalization processing unit and the bit allocating unit and configured to perform quantization and coding on normalized to-be-quantized vectors in a low bit coding sub-band and a high bit coding sub-band with pyramid lattice vector quantization and sphere lattice vector quantization respectively to obtain the coded bits of the frequency domain coefficients;
• wherein, the low bit coding sub-band is a coding sub-band in which the number of bits allocated to one frequency domain coefficient is less than a preset threshold value, the high bit coding sub-band is a coding sub-band in which the number of bits allocated to one frequency domain coefficient is greater than or equal to the preset threshold value;
• the bit stream multiplexer is connected to the amplitude envelope quantizing and coding unit and the classification lattice vector quantizing and coding unit and configured to multiplex the coded bits of each coding sub-band and the coded bits of the frequency domain coefficients to send to a decoding side.

An audio decoding system of lattice vector quantization, comprising:

• a bit stream demultiplexer, a coding sub-band amplitude envelope decoding unit, a bit allocating unit, a frequency domain coefficient decoding unit, a classification lattice vector quantization inverse quantizing unit, an inverse normalization processing unit, a noise filling unit and an inverse modified discrete cosine transform (IMDCT) unit, wherein,
• the bit stream demultiplexer is configured to separate coded bits of an amplitude envelope from a to-be-decoded bit stream;
• the coding sub-band amplitude envelope decoding unit is connected to the bit stream demultiplexer and configured to decode the coded bits of the amplitude envelope output by the bit stream demultiplexer to obtain an amplitude envelope quantization exponent of each coding sub-band;
• the bit allocating unit is connected to the amplitude envelope decoding unit and configured to perform bit allocation to obtain a number of coded bits allocated to each frequency domain coefficient in each coding sub-band;
• the frequency domain coefficient decoding unit is connected to the amplitude envelope decoding unit and the bit allocating unit and configured to decode a low bit coding sub-band to obtain a quantization index of the low bit coding sub-band;
• and decode a high bit coding sub-band to obtain an index vector of the high bit coding sub-band, wherein, the low bit coding sub-band is a coding sub-band in which the number of bits allocated to one frequency domain coefficient is less than a preset threshold value, the high bit coding sub-band is a coding sub-band in which the number of bits allocated to one frequency domain coefficient is greater than or equal to the preset threshold value;
• the classification lattice vector quantization inverse quantizing unit is configured to perform inverse quantization of the pyramid lattice vector quantization on the quantization index of the low bit coding sub-band, and perform inverse quantization of the sphere lattice vector quantization on the index vector of the high bit coding sub-band;
• the inverse normalization processing unit is configured to perform inverse normalization on values after the inverse quantization has been performed for the coding sub-band, and obtain the frequency domain coefficients;
• the noise filling unit is configured to perform noise filling on the sub-band to which no bit is allocated in the frequency domain coefficient output values output by the inverse normalization processing unit;
• the inverse modified discrete cosine transform (IMDCT) unit is connected to the noise filling unit and configured to perform IMDCT on the frequency domain coefficient for which the noise filling has been performed to obtain an audio signal.