Coded data generation or conversion – Quantizer
Reexamination Certificate
2002-04-29
2003-07-15
JeanGlaude, Jean Bruner (Department: 2819)
Coded data generation or conversion
Quantizer
C704S229000, C704S230000
Reexamination Certificate
active
06593872
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a signal processing apparatus and method for performing signal processing associated with quantization, on an input parameter, and to a signal coding apparatus and method in which the signal processing apparatus is used. Also, the present invention relates to a signal processing apparatus and method for inputting an index of a quantized output from quantization means and for performing signal processing associated with dequantization, and to a signal decoding apparatus and method in which the signal processing apparatus is used.
2. Description of the Related Art
Hitherto, various coding methods for performing signal compression by using statistical properties in a time domain and a frequency domain of audio signals (including voice signals and musical signals) and auditory characteristics of a human being are known. Broadly speaking, examples of these coding methods include coding in a time domain, coding in a frequency domain, and analysis-synthesis coding.
In transform coding in which coding is performed by performing an orthogonal transform on an input signal on a time axis into a signal on a frequency axis, the following has been proposed that, with a view to achieving a lower bit rate, dynamic bit allocation corresponding to an input signal is performed and quantization of coefficient data on a frequency axis is performed. However, the calculation of this bit allocation is complex, and in particular, when coefficient data on a frequency axis is divided in units of several pieces and vector quantization is performed by using the divided data as subvectors, if the bit allocation for each coefficient is changed, the calculation of bit allocation for quantization is complicated.
Furthermore, when bit allocation changes dramatically for each frame, which is a transform unit for the orthogonal transform, there is a drawback in that reproduced sound is likely to become unstable.
For this reason, the applicant of the present invention previously proposed in Japanese Unexamined Patent Application Publication No. 12-132194 (hereinafter referred to as “the conventional art”), a signal coding apparatus and method, and a signal decoding apparatus and method, in which the calculations of bit allocation can be easily performed while dynamic bit allocation corresponding to an input signal is performed during the coding associated with the orthogonal transform, and in which reproduced sound does not become unstable even if bit allocation dramatically changes between frames.
In this conventional art, when coding is performed on an input signal on a time axis by using the orthogonal transform, a weight is computed according to the input signal, coefficient data obtained by being orthogonally transformed is assigned an order according to the order of this weight, and quantization with high accuracy is performed in accordance with this order. Therefore, even if bit allocation is performed dynamically according to the input signal, the calculation of the number of bits, which is assigned to each coefficient, can be performed simply.
Furthermore, by specifying parameters for calculating bit allocation in advance and by sending these parameters to a decoder side, it becomes unnecessary to send information of bit allocation to the decoder side, and thus the amount of additional information can be reduced, and a lower bit rate can be realized.
In the above-described conventional art, since there is a need that the results of a calculation of band-by-band bit allocation be completely the same between the coder and the decoder, the computation accuracy for this calculation needs to precisely agree between them.
However, for example, in a case where a signal coded by a coder which is implemented in a DSP (Digital Signal Processor) which performs fixed-point calculations is to be decoded by a decoder which is implemented in a personal computer, etc., if the decoder uses floating-point calculations, in spite of the fact that completely the same LSP (Line Spectrum Pair) codebook is referred to and the same codeword is input, a discrepancy in band-by-band bit allocation, resulting from computation errors, occurs between the coder and the decoder. Therefore, in this case, fixed-point calculations similar to those of a DSP need to be realized on a personal computer so that accuracy agrees to eliminate errors.
However, when computations to be performed by a fixed-point DSP having a general 40-bit accumulator is realized by a personal computer having a conventional 32-bit processor installed therein, a problem arises in that the number of computations becomes dramatically larger than when the same calculation is performed by floating-point calculation due to a limitation on the bit width of the processor.
SUMMARY OF THE INVENTION
The present invention has been proposed in view of the conventional situation. An object of the present invention is to provide a signal processing apparatus and method in which calculation results of band-by-band bit allocation are completely the same between a coder and a decoder, to provide a signal coding apparatus and method, and a signal decoding apparatus and method, in which the signal processing apparatus is used.
To achieve the above-mentioned object, in one aspect, the present invention provides a signal processing apparatus for performing signal processing associated with quantization on a first input parameter, the signal processing apparatus comprising: quantization means for quantizing the first parameter; and table referring means for preparing a table in which a result of a conversion of each representative value of a codebook is prestored and for determining a second parameter by referring to the table by using an index of a quantized output from the quantization means when the second parameter is to be determined on the basis of the first parameter quantized by the quantization means.
Such a signal processing apparatus prepares a table in which results of a conversion of each representative value of a codebook are prestored, and determines the second parameter by referring to the table using the index of the quantized output from the quantization means when a second parameter is determined on the basis of the first parameter quantized by the quantization means. Therefore, computations for parameter conversion do not need to be performed. Furthermore, since parameter conversion is also performed on the encoder side in a similar manner, a computation error between the encoder side and the decoder side can be prevented.
To achieve the above-mentioned object, in another aspect, the present invention provides a signal processing method for performing signal processing associated with quantization, on a first input parameter, the signal processing method comprising: a quantization step of quantizing the first parameter; and a table referring step of preparing a table in which a result of a conversion of each representative value of a codebook is prestored and determining a second parameter by referring to the table by using an index of a quantized output in the quantization step when the second parameter is to be determined on the basis of the first parameter quantized in the quantization step.
Such a signal processing method prepares a table in which a result of a conversion of each representative value of a codebook is prestored and determines a second parameter by referring to the table by using an index of a quantized output in the quantization step when the second parameter is to be determined on the basis of the first parameter quantized in the quantization step. Therefore, computations for parameter conversion do not need to be performed. Furthermore, since parameter conversion is also performed on the encoder side in a similar manner, a computation error between the encoder side and the decoder side can be prevented.
To achieve the above-mentioned object, in another aspect, the present invention provides a signal coding apparatus for performing coding by performing an orthogo
Makino Kenichi
Matsumoto Jun
JeanGlaude Jean Bruner
Maioli Jay H.
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