Audio coding/decoding method and apparatus using excess quantization information

Abstract

There is provided an audio coding device which appropriately sets the quantization bit number by a small calculation amount in each stage when coding an input audio signal by performing multi-stage normalization/quantization. A quantization information calculation section determines total quantization information idwl0, based on normalization information idsf, and allocates the total quantization information idwl0 for quantization information idwl1 and quantization information idwl2. At this time, the quantization information calculation section limits the quantization information idwl1 by a limiter lim1, and allocates the total quantization information idwl0 for quantization information idwl1. If the quantization information idwl1 exceeds the limiter lim1, the excess is allocated for the quantization information idwl2. A first normalization section and a first quantization section normalizes and quantizes a frequency spectrum mdspec1 in the first stage. A second normalization section and a second quantization section normalizes and quantizes a differential frequency spectrum mdspec2 in the second stage.

What is claimed is: 
     
       1. An audio coding device including processing circuitry and programmed to execute a program via the processing circuitry, the program comprising:
 a time frequency transformation unit configured to perform time-frequency transform on an input audio signal to generate a frequency spectrum;   a quantization unit configured to (a) generate total quantization information indicating a quantization bit number on the basis of predetermined normalization information, (b) allocate the total quantization information, by setting a predetermined limit to a first quantization information, allocating, up to the predetermined limit, the total quantization information to the first quantization information, and allocating an excess beyond the predetermined limit to the second quantization information, and (c) in each of a plurality of stages, (i) generate the first quantization information and the second quantization information, each indicating a respective quantization bit number, and (ii) normalize the frequency spectrum for every frequency component by use of a first normalization coefficient corresponding to the normalization information to generate a normalized frequency spectrum, each stage having a predetermined limit to quantization information, and if quantization information allocated for a k-th stage, ‘k’ being an integer greater than zero, exceeds a limit in the k-th stage, an excess for quantization information is allocated to a (k+1)-th stage, the limit being based on a predetermined allowed quantization bit number for each of the respective plurality of stages;   a first quantization unit configured to linearly quantize the normalized frequency spectrum by use of a first quantization coefficient corresponding to the first quantization information, to generate a quantized frequency spectrum;   a subtraction unit configured to subtract from the frequency spectrum, a frequency spectrum obtained by inversely quantizing and inversely normalizing the quantized frequency spectrum, to generate a differential frequency spectrum;   a normalization unit configured to normalize the differential frequency spectrum by use of a second normalization coefficient corresponding to the normalization information and the first quantization information, to generate a differential normalized frequency spectrum;   a second normalization unit configured to linearly quantize the differential normalized frequency spectrum by use of a second quantization coefficient corresponding to the second quantization information, to generate a differential quantized frequency spectrum; and
 a code unit configured to code the normalization information, the first quantization information, the second quantization information, the quantized frequency spectrum, and the differential quantized frequency spectrum, to output a code string. 
   
     
     
       2. The audio coding device of  claim 1 , wherein the program further comprises a non-linear transformation unit configured to:
 perform non-linear transform on the frequency spectrum or the normalized frequency spectrum; and   perform non-linear inverse transform on a normalized frequency spectrum obtained by inversely quantizing the quantized frequency spectrum, or a frequency spectrum obtained by inversely normalizing the normalized frequency spectrum.   
     
     
       3. A method executed by an audio coding device comprising the steps of:
 a time-frequency transform step of performing time-frequency transform on an input audio signal to generate a frequency spectrum;   a quantization information calculation step including the steps of (a) generating total quantization information indicating a quantization bit number on the basis of predetermined normalization information, (b) allocating the total quantization information by setting a predetermined limit to a first quantization information, (c) allocating, up to the predetermined limit, the total quantization information to the first quantization information, (d) allocating an excess beyond the predetermined limit to the second quantization information, and, (e) in each of a plurality of stages, generating the first quantization information and the second quantization information, each indicating a respective quantization bit number;   a first normalization step of normalizing the frequency spectrum for every frequency component by use of a first normalization coefficient corresponding to the normalization information, to generate a normalized frequency spectrum, wherein, a predetermined limit to quantization information is set in each stage, and if quantization information allocated for a k-th stage, ‘k’ being an integer greater than zero, exceeds a limit in the k-th stage, an excess for quantization information is allocated for a (k+1)-th stage, the limit being based on a predetermined allowed quantization bit number for each of the respective plurality of stages;   a first quantization step of linearly quantizing the normalized frequency spectrum by use of a first quantization coefficient corresponding to the first quantization information, to generate a quantized frequency spectrum;   a subtraction step of subtracting, from the frequency spectrum, a frequency spectrum obtained by inversely quantizing and inversely normalizing the quantized frequency spectrum, to generate a differential frequency spectrum;   a second normalization step of normalizing the differential frequency spectrum by use of a second normalization coefficient corresponding to the normalization information and the first quantization information, to generate a differential normalized frequency spectrum;   a second quantization step of linearly quantizing the differential normalized frequency spectrum by use of a second quantization coefficient corresponding to the second quantization information, to generate a differential quantized frequency spectrum; and   a code string coding step of coding the normalization information, the first quantization information, the second quantization information, the quantized frequency spectrum, and the differential quantized frequency spectrum, to output a code string.   
     
     
       4. An audio coding device including processing circuitry and programmed to execute a program via the processing circuitry, the program comprising:
 a time frequency transformation unit configured to perform time-frequency transform on an input audio signal, to generate a frequency spectrum;   a quantization unit configured to (a) generate total quantization information indicating a quantization bit number on the basis of predetermined normalization information, (b) allocate the total quantization information, by setting a predetermined limit to a first quantization information, allocating, up to the predetermined limit, the total quantization information to the first quantization information, and allocating an excess beyond the predetermined limit to the second quantization information and (c) in each of a plurality of stages, (i) generate the first quantization information and the second quantization information, each indicating a respective quantization bit number, and (ii) normalize the frequency spectrum for every frequency component by use of a first normalization coefficient corresponding to the normalization information to generate a normalized frequency spectrum, each stage having a predetermined limit to quantization information, and if quantization information allocated for a k-th stage, ‘k’ being an integer greater than zero, exceeds a limit in the k-th stage, an excess for quantization information is allocated to a (k+1)-th stage, the limit being based on a predetermined allowed quantization bit number for each of the respective plurality of stages;   a first quantization unit configured to linearly quantize the normalized frequency spectrum by use of a first quantization coefficient corresponding to the first quantization information, to generate a quantized frequency spectrum;   subtraction unit configured to subtract from the frequency spectrum, a frequency spectrum obtained by inversely quantizing and inversely normalizing the quantized frequency spectrum, to generate a differential frequency spectrum;   a normalization unit configured to normalize the differential frequency spectrum by use of a second normalization coefficient corresponding to the normalization information and the first quantization information, to generate a differential normalized frequency spectrum;   a second quantization unit configured to linearly quantize the differential normalized frequency spectrum by use of a second quantization coefficient corresponding to the second quantization information, to generate a differential quantized frequency spectrum; and   a code unit configured to code string the normalization information, the quantized frequency spectrum, and the differential quantized frequency spectrum, to output a code string.   
     
     
       5. The device according to  claim 4 , wherein:
 a maximum quantization error, corresponding to the first quantization information, is uniquely determined and   the second normalization coefficient is determined by the product of the first normalization coefficient and the reciprocal of the maximum quantization error.   
     
     
       6. The device according to  claim 4 , wherein the quantization bit number indicated by the total quantization information increases or decreases one by one as the normalization information is increased or decreased one by one. 
     
     
       7. The device according to  claim 4 , wherein the audio coding device is further configured to:
 perform non-linear transform on the frequency spectrum or the normalized frequency spectrum; and   perform non-linear inverse transform on a normalized frequency spectrum obtained by inversely quantizing the quantized frequency spectrum, or a frequency spectrum obtained by inversely normalizing the normalized frequency spectrum.   
     
     
       8. A method executed by an audio coding device comprising the steps of:
 a time-frequency transform step of performing time-frequency transform on an input audio signal to generate a frequency spectrum;   a quantization information calculation step including the steps of (a) generating total quantization information indicating a quantization bit number on the basis of predetermined normalization information, (b) allocating the total quantization information by setting a predetermined limit to a first quantization information, (c) allocating, up to the predetermined limit, the total quantization information to the first quantization information, and (d) in each of a plurality of stages, allocating an excess beyond the predetermined limit to the second quantization information to generate, the first quantization information and the second quantization information each indicating a respective quantization bit number;   a first normalization step of normalizing the frequency spectrum for every frequency component by use of a first normalization coefficient corresponding to the normalization information, to generate a normalized frequency spectrum, wherein, a predetermined limit to quantization information is set in each stage, and if quantization information allocated for a k-th stage, ‘k’ being an integer greater than zero, exceeds a limit in the k-th stage, an excess for quantization information is allocated for a (k+1)-th stage, the limit being based on a predetermined allowed quantization bit number for each of the respective plurality of stages;   a first quantization step of linearly quantizing the normalized frequency spectrum by use of a first quantization coefficient corresponding to the first quantization information, to generate a quantized frequency spectrum;   a subtraction step of subtracting, from the frequency spectrum, a frequency spectrum obtained by inversely quantizing and inversely normalizing the quantized frequency spectrum, to generate a differential frequency spectrum;   a second normalization step of normalizing the differential frequency spectrum by use of a second normalization coefficient corresponding to the normalization information and the first quantization information, to generate a differential normalized frequency spectrum;   a second quantization step of linearly quantizing the differential normalized frequency spectrum by use of a second quantization coefficient corresponding to the second quantization information, to generate a differential quantized frequency spectrum; and   a code string coding step of coding the normalization information, the quantized frequency spectrum, and the differential quantized frequency spectrum, to output a code string.   
     
     
       9. An apparatus including an audio coding device with processing circuitry and programmed to execute a program via the processing circuitry, the program comprising:
 a time frequency transformation unit configured to perform time-frequency transform on an input audio signal to generate a frequency spectrum;   a quantization unit configured to (a) generate total quantization information indicating a quantization bit number on the basis of predetermined normalization information (b) allocate the total quantization information, by setting a predetermined limit to a first quantization information, allocating, up to the predetermined limit, the total quantization information to the first quantization information, and allocating an excess beyond the predetermined limit to the second quantization information (c) in each of a plurality of stages, (i) generate the first quantization information and the second quantization information, each indicating a respective quantization bit number, and (ii) normalize the frequency spectrum for every frequency component by use of a first normalization coefficient corresponding to the normalization information, to generate a normalized frequency spectrum each stage having a predetermined limit to quantization information , and if quantization information allocated for a k-th stage, ‘k’ being an integer greater than zero, exceeds a limit in the k-th stage, an excess for quantization information is allocated to a (k+1)-th stage, the limit being based on a predetermined allowed quantization bit number for each of the respective plurality of stages;   a first quantization unit configured to linearly quantize the normalized frequency spectrum by use of a first quantization coefficient corresponding to the first quantization information, to generate a quantized frequency spectrum;   a subtraction unit configured to subtract from the normalized frequency spectrum, a normalized frequency spectrum obtained by inversely quantizing the quantized frequency spectrum, to generate a differential normalized frequency spectrum;   a normalization unit configured to normalize the differential normalized frequency spectrum by use of a second normalization coefficient corresponding to the first quantization information, to generate a differential renormalized frequency spectrum;   a second quantization unit configured to linearly quantize the differential renormalized frequency spectrum by use of a second quantization coefficient corresponding to the second quantization information, to generate a differential quantized frequency spectrum; and   a code unit configured to code the normalization information, the first quantization information, the second quantization information, the quantized frequency spectrum, and the differential quantized frequency spectrum, to output a code string.   
     
     
       10. The apparatus according to  claim 9 , wherein the audio coding device is further configured to:
 perform non-linear transform on the frequency spectrum or the normalized frequency spectrum; and   perform non-linear inverse transform on a normalized frequency spectrum obtained by inversely quantizing the quantized frequency spectrum, or a frequency spectrum obtained by inversely normalizing the normalized frequency spectrum.   
     
     
       11. A method executed by an audio coding device comprising the steps of:
 a time-frequency transform step of performing time-frequency transform on an input audio signal to generate a frequency spectrum;   a quantization information calculation step including the steps of (a) generating total quantization information indicating a quantization bit number on the basis of predetermined normalization information, (b) allocating the total quantization information by setting a predetermined limit to a first quantization information, (c) allocating, up to the predetermined limit, the total quantization information to the first quantization information, and (d) in each of a plurality of stages, allocating an excess beyond the predetermined limit to the second quantization information, and generating the first quantization information and the second quantization information, each indicating a respective quantization bit number;   a first normalization step of normalizing the frequency spectrum for every frequency component by use of a first normalization coefficient corresponding to the normalization information, to generate a normalized frequency spectrum, wherein, a predetermined limit to quantization information is set in each stage, and if quantization information allocated for a k-th stage, ‘k’ being an integer greater than zero, exceeds a limit in the k-th stage, an excess for quantization information is allocated for a (k+1)-th stage, the limit being based on a predetermined allowed quantization bit number for each of the respective plurality of stages;   a first quantization step of linearly quantizing the normalized frequency spectrum by use of a first quantization coefficient corresponding to the first quantization information, to generate a quantized frequency spectrum;   a subtraction step of subtracting, from the normalized frequency spectrum, a normalized frequency spectrum obtained by inversely quantizing the quantized frequency spectrum, to generate a differential normalized frequency spectrum;   a second normalization step of normalizing the differential normalized frequency spectrum by use of a second normalization coefficient corresponding to the first quantization information, to generate a differential renormalized frequency spectrum;   a second quantization step of linearly quantizing the differential renormalized frequency spectrum by use of a second quantization coefficient corresponding to the second quantization information, to generate a differential quantized frequency spectrum; and   a code string coding step of coding the normalization information, the first quantization information, the second quantization information, the quantized frequency spectrum, and the differential quantized frequency spectrum, to output a code string.   
     
     
       12. An apparatus comprising an audio decoding device including processing circuitry and programmed to execute a program via the processing circuitry, the program comprising:
 a time frequency transformation unit configured to decode an input code string, to generate normalization information, a quantized frequency spectrum, and a differential quantized frequency spectrum;   a quantization unit configured to (a) generate total quantization information indicating a quantization bit number on the basis of the normalization information (b) allocate the total quantization information, by setting a predetermined limit to a first quantization information, allocating, up to the predetermined limit, the total quantization information to the first quantization information, and allocating an excess beyond the predetermined limit to the second quantization information, and (c) in each of a plurality of stages, (i) generate the first quantization information and the second quantization information, each indicating a respective quantization bit number and linearly inversely quantize the quantized frequency spectrum by use of a first inverse quantization coefficient corresponding to the first quantization information and (ii) generate a normalized frequency spectrum, each stage having a predetermined limit to quantization information, and if quantization information allocated for a k-th stage, ‘k’ being an integer greater than zero, exceeds a limit in the k-th stage, an excess for quantization information is allocated to a (k+1)-th stage, the limit being based on a predetermined allowed quantization bit number for each of the respective plurality of stages;   a first normalization unit configured to inversely normalize the normalized frequency spectrum by use of a first inverse normalization coefficient corresponding to the normalization information, to generate a frequency spectrum;   a subtraction unit configured to linearly inversely quantize the differential quantized frequency spectrum by use of a second inverse quantization coefficient corresponding to the second quantization information, to generate a differential normalized frequency spectrum;   a second normalization unit configured to inversely normalize the differential normalized frequency spectrum by use of a second inverse normalization coefficient corresponding to the normalization information and the first quantization information, to generate a differential frequency spectrum;   an addition unit configured to add the frequency spectrum and the differential frequency spectrum; and   a second time transformation unit configured to perform frequency-time transform on a frequency spectrum obtained by the addition means, to generate an output audio signal.   
     
     
       13. A method executed by an audio coding device comprising the steps of:
 a code string decoding step of decoding an input code string, to generate normalization information, a quantized frequency spectrum, and a differential quantized frequency spectrum;   a quantization information calculation step including the steps of (a) generating total quantization information indicating a quantization bit number on the basis of the normalization information, (b) allocating the total quantization information, by setting a predetermined limit to a first quantization information, (c) allocating, up to the predetermined limit, the total quantization information to the first quantization information, and allocating an excess beyond the predetermined limit to the second quantization information (d) in each of a plurality of stages, generate the first quantization information and second quantization information each indicating a quantization bit number;   a first inverse quantization step of linearly inversely quantizing the quantized frequency spectrum by use of a first inverse quantization coefficient corresponding to the first quantization information, to generate a normalized frequency spectrum, wherein, a predetermined limit to quantization information is set in each stage, and if quantization information allocated for a k-th stage, ‘k’ being an integer greater than zero, exceeds a limit in the k-th stage, an excess for quantization information is allocated for a (k+1)-th stage, the limit being based on a predetermined allowed quantization bit number for each of the respective plurality of stages;   a first inverse normalization step of inversely normalizing the normalized frequency spectrum by use of a first inverse normalization coefficient corresponding to the normalization information, to generate a frequency spectrum;   a second inverse quantization step of linearly inversely quantizing the differential quantized frequency spectrum by use of a second inverse quantization coefficient corresponding to the second quantization information, to generate a differential normalized frequency spectrum;   a second inverse normalization step of inversely normalizing the differential normalized frequency spectrum by use of a second inverse normalization coefficient corresponding to the normalization information and the first quantization information, to generate a differential frequency spectrum;   an addition step of adding the frequency spectrum and the differential frequency spectrum; and   a frequency-time transform step of performing frequency-time transform on a frequency spectrum obtained by the addition step, to generate an output audio signal.   
     
     
       14. An apparatus comprising an audio decoding device including processing circuitry and programmed to execute a program via the processing circuitry, the program comprising:
 a code string decoding unit configured to decode an input code string, to generate normalization information, a quantized frequency spectrum, and a differential quantized frequency spectrum;   a quantization information calculation unit configured to (a) generate total quantization information indicating a quantization bit number on the basis of the normalization information, (b) for a plurality of stages, allocate the total quantization information, each stage having a predetermined limit to quantization information, and if quantization information allocated to a k-th stage (“k’ being an integer greater than zero) exceeds the predetermined limit of the k-th stage, an excess of the quantization information is allocated to a (k+1)-th stage, the limit being based on predetermined allowed quantization bit number for each stage of the respective plurality of stages, wherein the allocating includes allocating, up to the predetermined limit, the total quantization information to a first quantization information, and allocating an excess beyond the predetermined limit to a second quantization information, and generating the first quantization information and the second quantization information, each of the first quantization information and the second quantization information indicating a respective quantization bit number;   a first inverse quantization unit configured to linearly inversely quantize the quantized frequency spectrum by use of a first inverse quantization coefficient corresponding to the first quantization information, and generate a normalized frequency spectrum;   a first inverse normalization unit configured to inversely normalize the normalized frequency spectrum by use of a first inverse normalization coefficient corresponding to the normalization information, to generate a frequency spectrum;   a second inverse quantization unit configured to linearly inversely quantize the differential quantized frequency spectrum by use of a second inverse quantization coefficient corresponding to the second quantization information, to generate a differential normalized frequency spectrum;   a second normalization unit configured to inversely normalize the differential normalized frequency spectrum by use of a second inverse normalization coefficient corresponding to the normalization information and the first quantization information, to generate a differential frequency spectrum;   an addition unit configured to add the frequency spectrum and the differential frequency spectrum in a frequency domain and generate a resultant frequency spectrum; and   a frequency to time transformation unit configured to perform a frequency-time transform on the resultant frequency spectrum, to generate an output audio signal.   
     
     
       15. A method executed by an audio coding device comprising:
 a transform step of transforming an input audio signal and generating a normalization information and a first frequency spectrum;   a quantization information calculation step of (a) generating total quantization information indicating a quantization bit number on the basis of the normalization information, and (b) for a plurality of stages, allocating the total quantization information among the plurality of stages, each stage having a predetermined limit to quantization information, such that quantization information is first allocated to a k-th stage (“k’ being an integer greater than zero) and quantization information for a (k+1)-th stage being set to the predetermined limit of the (k+1)-th stage or the excess of the quantization information not allocated to the k-th stage, the limit being based on predetermined allowed quantization bit number for each stage of the respective plurality of stages, wherein the allocating includes allocating up to the predetermined limit, the total quantization information to a first quantization information, and allocating an excess beyond the predetermined limit or a predetermined limit to a second quantization information, and generating the first quantization information and the second quantization information, each of the first quantization information and the second quantization information indicating a respective quantization bit number;   a first normalization step of normalizing the first frequency spectrum by use of a first normalization coefficient corresponding to the normalization information and generating a first normalized frequency spectrum;   a first quantization step of linearly quantizing the first normalized frequency spectrum by use of a first quantization coefficient corresponding to the first quantization information and generating a first quantized frequency spectrum;   an inverse quantization step of linearly inversely quantizing the first quantized frequency spectrum by use of an inverse quantization coefficient corresponding to the first quantization information and generating a second normalized frequency spectrum;   an inverse normalization step of inversely normalizing the second normalized frequency spectrum by use of an inverse normalization coefficient corresponding to the normalization information and generating a second frequency spectrum;   an subtraction step of subtracting the second frequency spectrum from the first frequency spectrum in a frequency domain and generating a differential frequency spectrum;   a second normalization step of normalizing the differential frequency spectrum by use of a second normalization coefficient corresponding to the normalization information and the first quantization information and generating a differential normalized frequency spectrum;   a second quantization step of linearly quantizing the differential normalized frequency spectrum by use of a second quantization coefficient corresponding to the second quantization information and generating a differential quantized frequency spectrum; and   a code string coding step of coding the normalization information, the first quantization information, the second quantization information, and the differential quantized frequency spectrum and generating an output code string.