JPH0863192A - Device for extracting spectrum parameter - Google Patents

Abstract

PURPOSE: To improve the extraction precision of a spectrum parameter and the performance of a signal processor of a frame processing type. CONSTITUTION: This device is constituted of respective circuits such as an analysis window circuit 3 outputting an input signal x(t) as the input signal x(t) (t=tn -tn+1 -1) cut out by an analysis window, an interpolation table circuit 4 storing an interpolation function, a buffer circuit 5 receiving and storing a quantization spectrum parameter kq (n, m), an interpolation analysis circuit 6 using the quantization spectrum parameter kq (n, m), the input signal x(t) (t=tn -tn+1 -1) and the interpolation function and calculating and outputting the newest spectrum parameter k(n, m), a quantization circuit 7 outputting the newest quantization spectrum parameter kq (n, m) obtained by quantizing the output of the interpolation analysis circuit 6 and an interpolation circuit 9 calculating the interpolation spectrum parameter kqi (n, m, t) by using the interpolation function, the quantization spectrum parameter kq (n, m) stored by the buffer circuit 5 and the newest quantization spectrum parameter kq (n, m) obtained by the quantization circuit 7 and outputting it to an output terminal 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spectrum parameter extraction device, and more particularly, it divides an input signal into frames, calculates the spectrum parameters in each frame, and uses the spectrum parameters in subframes obtained by further dividing the frame The present invention relates to a spectrum parameter extraction device used in a frame processing type signal processing device.

[0002]

2. Description of the Related Art As a conventional frame processing type signal processing apparatus using a spectral parameter extraction apparatus, CELP
There are speech coding methods such as (Code Excited Linear Prediction Coding) method and multi-pulse method. As a document describing each coding method, for example, IEE Proc. ICASSP-85, 1985, 93
7-940 (Reference 1) and IEE Proc. ICASSP-86, 1986, 1689-
1692 (Reference 2).

Next, the basic encoding process of these encoding methods will be described with reference to FIG.

FIG. 6A is a waveform diagram showing an example of an input signal. FIG. 6 min. (B) is an explanatory diagram illustrating how to cut out a frame, FIG. 6 min. (C) is an explanatory diagram illustrating how to cut out a subframe, and FIG. 6 min. (D) is a time direction of spectrum parameters. Fig. 6 is an explanatory view for explaining an interpolation function that represents the state of interpolation in Fig. 6, Fig. 6 min. (E) is an explanatory view of the analysis window and the spectrum parameter change model in the conventional analysis method, and Fig. 6 min. 4] is an explanatory view of an analysis window and a variation model of spectrum parameters in the analysis method of the present invention.

First, the input signal shown in FIG. 6 (a) is divided into the frames shown in FIG. 6 (b). Next, Figure 6
Spectral parameters corresponding to each frame are extracted by spectrally analyzing the input signal cut out in the analysis window shown in (e). Further, this spectral parameter is quantized. Next, the spectrum parameter corresponding to each sub-frame shown in FIG. 6 (c) is calculated by interpolation of this quantized spectrum parameter and the spectrum parameter quantized in the previous frame. As the interpolation characteristic, the interpolation function shown in FIG. 6 (d) is used. Finally, the excitation signal of the input signal of each subframe is quantized using the spectral parameter of each subframe.

Next, with reference to FIG. 7, the operation of the conventional spectrum parameter extracting apparatus for extracting the spectrum parameter corresponding to each subframe from the input signal in this encoding method will be described.

First, the input signal input from the input terminal 60 is cut out by the analysis window circuit 61 at the analysis window shown in FIG. Next, the spectrum parameter is calculated by analyzing the extracted signal in the analysis circuit 62. Next, the quantization circuit 63 quantizes the spectrum parameter, and the quantized spectrum parameter obtained is interpolated by the interpolation circuit 64.
And is stored in the buffer circuit 65. Further, the interpolated quantized spectrum parameter corresponding to each subframe obtained by interpolating the quantized spectrum parameter in the interpolation circuit 64 and the quantized spectrum parameter stored in the buffer circuit 65 is output to the output terminal 66.

Here, as the spectrum analysis of the analysis circuit 62, there are Burg analysis, linear prediction analysis and the like.
For example, the process of Burg analysis is shown in the flow chart of FIG.

In FIG. 8, x (t) (t = t _{n to} t _{n + 1} -1) is the input signal in the analysis window, M is the analysis order, n is the analysis window number, and e (m, t) is Forward prediction error, r (m, t) is backward prediction error, k (n, m) is one of the spectral parameters, k parameter, n is the frame number, t _n is the start time of the nth frame. Represent each. The equation for the process M in FIG. 8 is the normative function of equation (1).
It is obtained by defining the k parameter k (n, m) such that D (m) is minimized, that is, dD (m) / dk (n, m) = 0.

[0010]

Further, there has been proposed an improved Burg analysis in which the k parameter is modeled by a plurality of specified functions in the Burg method and the analysis is performed in consideration of the change of the k parameter. As a document describing the improved Burg method, Imaizumi et al. “Time dependence assuming parameter fluctuations”
Burg method ”IEICE Transactions, Volume J68-A, Vol. 3
No., pp. 352-353, 1985 (reference 3). In the modified Burg analysis, the time-varying model of k parameter k _i (n, m, t) is expressed by equation (4). Here, q (i, m) is a standard function, and u (i, t) is a weighting function representing the time change of each standard function. K _i (n, m, t) is the k parameter at time t.

[0012]

Also in the equation for calculating the k parameter in the improved Burg analysis, the equation (4) is substituted into the equation (1) together with the equations (2) and (3), and the reference function Dm of the equation (1) is minimized. I.e. dD (m) / dq
It is obtained by defining q (i, m) so that (i, m) = 0. g is the number of standard functions.

In the conventional Burg analysis described above,
Since the k parameter is constant within the analysis window, the time-varying model becomes Eq. (5) when described in the same way as Eq. (4). k _i (n, m, t) = k (n, m) (5) Further, in the interpolation circuit 64, the past quantized spectrum parameter k _q (i, m) (i = 0, ..., n- 1) and the quantized spectral parameter k _q (n, m) for the current analysis window n are interpolated by Eq. (6) to interpolate the quantized spectral parameter k _qi (n, m, t).
Is calculated. w (i, t) is an interpolation coefficient representing the time interpolation characteristic.

[0015]

[0016]

The above-mentioned conventional spectral parameter extraction device is based on the equation in spectral analysis.
Since the time variation model of the spectrum parameter of (5) and the interpolation characteristic of the equation (6) for calculating the spectrum parameter at each time are different, the spectrum parameter is changed especially when the spectrum characteristic of the input signal greatly changes within the analysis window. There is a problem that the extraction accuracy is reduced.

An object of the present invention is to improve the extraction accuracy of spectrum parameters and improve the performance of a frame processing type signal processing apparatus even when the spectral characteristics of an input signal greatly change within the analysis window. An object is to provide a spectral parameter extraction device capable of performing the same.

[0018]

A spectrum parameter extracting apparatus of the present invention comprises an analysis window circuit for cutting out an input signal input from an input terminal with an analysis window, an interpolation table circuit accumulating an interpolation function, and a spectrum parameter. A buffer circuit for receiving and storing a quantized quantized spectrum parameter, a quantized spectrum parameter stored by the buffer circuit, an input signal cut out by the analysis window circuit, and an interpolation stored by the interpolation table circuit. An interpolation analysis circuit that calculates and outputs the latest spectrum parameter using a function, and a quantization circuit that outputs the latest quantized spectrum parameter obtained by quantizing the spectrum parameter calculated by the interpolation analysis circuit to the buffer circuit And the interpolation function stored in the interpolation table circuit and the buffer circuit That the quantized spectral parameters and the quantization circuit is configured to have an interpolation circuit that outputs the calculated output interpolated spectrum parameters by using the most recent quantized spectral parameters obtained by quantizing.

The spectrum parameter extracting apparatus of the present invention comprises an analysis window circuit for cutting out an input signal inputted from an input terminal at an analysis window, an interpolation table circuit for accumulating an interpolation function, and a buffer for receiving and accumulating a spectrum parameter. Circuit, the spectrum parameter stored in the buffer circuit, the input signal cut out by the analysis window circuit, and the interpolation function stored in the interpolation table circuit are used to calculate the latest spectrum parameter in the buffer circuit. Interpolation spectrum using the output interpolation analysis circuit, the interpolation function stored in the interpolation table circuit, the spectrum parameter stored in the buffer circuit, and the latest spectrum parameter calculated by the interpolation analysis circuit. And a interpolation circuit for calculating parameters and outputting the parameters to an output terminal.

The spectrum parameter extracting apparatus of the present invention is an analysis window circuit for cutting out an input signal input from an input terminal with an analysis window, an interpolation table circuit for accumulating an interpolation function, and a quantization for quantizing spectrum parameters. A buffer circuit that receives and stores the spectrum parameter, a quantized spectrum parameter stored by the buffer circuit, an input signal cut out by the analysis window circuit, and an interpolation function stored by the interpolation table circuit are used. And an quantization circuit for outputting the latest quantized spectrum parameter obtained by quantizing the spectrum parameter calculated by the interpolation analysis circuit to the buffer circuit and the output terminal. It is a composition.

The spectrum parameter extraction apparatus of the present invention comprises an analysis window circuit for cutting out an input signal input from an input terminal at an analysis window, an interpolation table circuit for accumulating an interpolation function, and a buffer for receiving and accumulating a spectrum parameter. Circuit, the spectrum parameter accumulated by the buffer circuit, the input signal cut out by the analysis window circuit, and the interpolation function accumulated by the interpolation table circuit are used to calculate the latest spectrum parameter, and the buffer circuit and And an interpolation analysis circuit for outputting to an output terminal.

[0022]

In the present invention, the equation (5) is used instead of equation (5) as the time variation model of the spectral parameter in the Burg analysis.
Use (6). Accordingly, the time change model of the spectrum parameter in the spectrum analysis can be approximated to the interpolation function in the interpolation, so that the spectrum parameter extraction accuracy can be improved.

In the example of FIG. 6, FIG. 6 (e) and FIG. 6
(f) is an analysis window function in the conventional and inventive spectral parameter extracting apparatus, respectively. In the analysis in the nth frame, it can be seen that the analysis window function in the present invention can be the same as the interpolation function in FIG. 6D in the nth frame.

K used in the Burg analysis of the present invention
The parameter calculation formula is also calculated by combining formula (6) with formulas (2) and (3).
Substituting into (1) and minimizing the reference function D (m) in equation (1), i.e., defining q (i, m) so that dD (m) / dq (i, m) = 0. Obtained by

[0025]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a block diagram of the first embodiment of the present invention.

The spectral parameter extracting apparatus 1 according to the first embodiment of the present invention uses the input signal x input from the input terminal 2.
Input signal x (t) (t = t _{n to} t _{n + 1} -1) obtained by cutting (t) with the analysis window
Output analysis window circuit 3, interpolation table circuit 4 accumulating interpolation functions, and spectrum parameter k (n, m)
The quantized quantized spectral parameter k _q (n, m) and a buffer circuit 5 which receives the accumulated, quantized spectral parameter k _q (n, m) of the buffer circuit 5 is stored with the analysis window circuit 3 is The latest spectrum parameter k (n, m) is calculated using the cut-out input signal x (t) (t = t _{n to} t _{n + 1} -1) and the interpolation function stored in the interpolation table circuit 4. The interpolation analysis circuit 6 to output and the latest quantized spectrum parameter k _q (n, m) obtained by quantizing the spectrum parameter k (n, m) calculated by the interpolation analysis circuit 6 are output to the buffer circuit 5. The quantization circuit 7, the interpolation function stored in the interpolation table circuit 4, the quantized spectrum parameter k _q (n, m) stored in the buffer circuit 5, and the latest quantum obtained by the quantization circuit 7 of spectral parameter k _q (n, m) interpolation spectral parameter k _qi by using the (n, m, t) of the total It was made from the interpolation circuit 9 for outputting to the output terminal 8.

FIG. 2 is a block diagram of the second embodiment of the present invention. The same names and reference numerals are given to parts having the same functions as those in the first embodiment.

The spectral parameter extracting apparatus 10 according to the second embodiment of the present invention uses the input signal input from the input terminal 2.
Input signal x (t) (t = t _{n to} t _{n + 1} -1) obtained by cutting x (t) in the analysis window
Output analysis window circuit 3, interpolation table circuit 4 accumulating interpolation functions, and spectrum parameter k (n, m)
Buffer circuit 5 for receiving and storing the spectrum parameter k (n, m) stored in the buffer circuit 5 and the input signal x (t) cut out by the analysis window circuit 3 (t = t _{n to} t _{n + 1} -1) and the interpolation function stored in the interpolation table circuit 4 are used to calculate the latest spectrum parameter k (n, m) and output to the buffer circuit 5, and the interpolation table circuit 4 is stored. Interpolation spectrum parameter using the interpolation function and the spectrum parameter k (n, m) accumulated in the buffer circuit 5 and the latest spectrum parameter k (n, m) calculated by the interpolation analysis circuit 6 and an interpolation circuit 9 for calculating k _i (n, m, t) and outputting it to the output terminal 8.

FIG. 3 is a block diagram of the third embodiment of the present invention. The same names and reference numerals are given to parts having the same functions as those in the first embodiment.

The spectral parameter extracting device 11 of the third embodiment of the present invention is designed to input the input signal from the input terminal 2.
Input signal x (t) (t = t _{n to} t _{n + 1} -1) obtained by cutting x (t) in the analysis window
Output analysis window circuit 3, interpolation table circuit 4 accumulating interpolation functions, and spectrum parameter k (n, m)
The quantized quantized spectral parameter k _q (n, m) and a buffer circuit 5 which receives the accumulated, quantized spectral parameter k _q (n, m) of the buffer circuit 5 is stored with the analysis window circuit 3 is The latest spectrum parameter k (n, m) is calculated using the cut-out input signal x (t) (t = t _{n to} t _{n + 1} -1) and the interpolation function stored in the interpolation table circuit 4. The interpolation analysis circuit 6 for outputting and the latest quantized spectrum parameter k _q (n, m) obtained by quantizing the spectrum parameter k (n, m) calculated by the interpolation analysis circuit 6 are output to the buffer circuit 5 and the output terminal 8.
And the quantizing circuit 7 for outputting to.

FIG. 4 is a block diagram of the fourth embodiment of the present invention. The same names and reference numerals are given to parts having the same functions as those in the first embodiment.

The spectral parameter extracting device 12 of the fourth embodiment of the present invention is the same as the input signal input from the input terminal 2.
Input signal x (t) (t = t _{n to} t _{n + 1} -1) obtained by cutting x (t) in the analysis window
Output analysis window circuit 3, interpolation table circuit 4 accumulating interpolation functions, and spectrum parameter k (n, m)
Buffer circuit 5 for receiving and storing the spectrum parameter k (n, m) stored in the buffer circuit 5 and the input signal x (t) cut out by the analysis window circuit 3 (t = t _{n to} t _{n + 1} -1) and the interpolation function stored in the interpolation table circuit 4 are used to calculate the latest spectrum parameter k (n, m) and output to the buffer circuit 5 and the output terminal 8.

FIG. 5 is a flow chart for explaining the calculation procedure of the spectrum parameter of the interpolation analysis circuit shown in FIGS.

Next, the operation will be described.

First, the first embodiment will be described with reference to FIGS. 1 and 5.

First, the input signal x (t) is input from the input terminal 2. Next, in the analysis window circuit 3, the input signal x (t) is cut out in a predetermined analysis window (generally about 20 msec in the case of a voice signal), and the input signal x (t) (t = t _{n to} t _{n + 1-} Output as 1). Next, in the interpolation analysis circuit 6, the cut-out signal, the interpolation coefficient w (i, t) passed from the interpolation table circuit 4 accumulating the interpolation characteristics of the equation (6), and the quantum passed from the buffer circuit 5. The past quantized spectrum parameter k _q quantized by the quantization circuit 7.
Using (n, m) and, the spectral parameter k (n, m) is calculated according to the flowchart of FIG. However, in FIG. 5, Equation (7) is used as the time change model of Equation (6) to show a simple example. k _i (n, m, t) = α (t) k (n-1, m) + β (t) k (n, m) (7) where α (t) and β (t) are times is a weighting function for the interpolation of t. Next, the quantization circuit 7 quantizes the spectrum parameter k (n, m) to obtain a quantized spectrum parameter k _q
(n, m) is passed to the buffer circuit 5 and the interpolation circuit 9.

Here, various methods other than the above-mentioned method have been proposed as a method of spectral parameter quantization,
For example, IEICE Transactions, Vol. J67-A, Vol.
No. 974-981, 1984 (Reference 4), Vector Scalar Quantization Method, IEEE Proc. ICASSP-91, 1991, 66
There is a division vector quantization method described in pages 1 to 664 (reference 5).

Next, the buffer circuit 5 stores the quantized spectrum parameter k _q (n, m) and passes it to the interpolation analysis circuit 6.
Finally interpolation circuit 9, by using the past quantized spectral parameter k _q (n, m) and the quantization circuit 7 passes the quantized spectral parameter k _q (n, m) of the buffer circuit 5 passes, wherein
(6) The interpolation quantized spectrum parameter k _qi (n, m, t) obtained by performing the interpolation using the equation (7 in the example of FIG. 5) is output from the output terminal 8.

Next, a second embodiment will be described with reference to FIG.

The second embodiment differs from the first embodiment only in that the quantizing circuit 7 is not provided, as is apparent from comparison between FIGS. 1 and 2. This is an embodiment in the case where the spectrum parameter extraction device does not require quantization, and is useful, for example, in the extraction method of the spectrum parameter used for the perceptual weighting of the excitation signal quantization of the voice coding method. .

Next, a third embodiment will be described with reference to FIG.

The difference between the third embodiment and the first embodiment is that the interpolator 9 is clear as can be seen by comparing FIGS.
There is no. This is an embodiment in the case where the spectral parameter extraction device does not require the interpolated spectral parameter. For example, the quantized spectral parameter k _q (n, m) of the quantization circuit 7 is set to a spectral parameter other than the k parameter. It is useful when used in the case where interpolation is performed by a circuit different from the present invention after conversion into.

Finally, a fourth embodiment will be described with reference to FIG.

The third embodiment is different from the first embodiment in that the quantizing circuit 7 and the interpolating circuit 9 are not provided, as is apparent from comparison between FIGS. This is an embodiment in the case where the spectral parameter extraction device does not require quantization and does not require interpolated spectral parameters. For example, the spectral parameter k (n, m) of the interpolation analysis circuit 6 is This is useful when interpolation is performed by a circuit different from the present invention after conversion into a spectrum parameter other than the k parameter.

[0046]

As described above, according to the present invention, the analysis window circuit for cutting out the input signal input from the input terminal with the analysis window, the interpolation table circuit for accumulating the interpolation function, and the quantization of the spectrum parameter. Using a buffer circuit for receiving and storing the quantized spectral parameters, the quantized spectral parameters accumulated by the buffer circuit, the input signal cut out by the analysis window circuit, and the interpolation function accumulated by the interpolation table circuit. The interpolation analysis circuit that calculates and outputs the spectrum parameter of, the quantization circuit that outputs the latest quantized spectrum parameter obtained by quantizing the spectrum parameter calculated by the interpolation analysis circuit to the buffer circuit, and the interpolation table circuit are stored. Quantization spectrum parameter that is accumulated in the interpolation function and buffer circuit and quantization circuit is quantized By including an interpolation circuit that calculates an interpolation spectrum parameter using the obtained latest quantized spectrum parameter and outputs the result to the output terminal, the spectrum can be changed even when the spectrum characteristic of the input signal significantly changes within the analysis window. Improves parameter extraction accuracy,
There is an effect that the performance of the frame processing type signal processing device can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention.

FIG. 2 is a block diagram of a second embodiment of the present invention.

FIG. 3 is a block diagram of a third embodiment of the present invention.

FIG. 4 is a block diagram of a fourth embodiment of the present invention.

FIG. 5 is a flowchart for explaining a calculation procedure of spectrum parameters of the interpolation analysis circuit described in FIGS.

FIG. 6 is an explanatory diagram illustrating a basic encoding process of an encoding method.

FIG. 7 is an explanatory diagram illustrating an operation of a conventional spectrum parameter extraction device.

FIG. 8 is a flowchart showing a process of Burg analysis.

[Explanation of symbols]

1, 10, 11, 12 Spectral Parameter Extractor 2 Input Terminal 3 Analysis Window Circuit 4 Interpolation Table Circuit 5 Buffer Circuit 6 Interpolation Analysis Circuit 7 Quantization Circuit 8 Output Terminal 9 Interpolation Circuit

Claims (4)

[Claims] 1. An analysis window circuit for cutting out an input signal inputted from an input terminal with an analysis window, an interpolation table circuit for accumulating an interpolation function, and a quantized spectrum parameter obtained by quantizing a spectrum parameter for storage. The latest spectrum parameter is calculated and output using the buffer circuit, the quantized spectrum parameter stored in the buffer circuit, the input signal cut out by the analysis window circuit, and the interpolation function stored in the interpolation table circuit. Interpolation analysis circuit, a quantization circuit for outputting the latest quantized spectrum parameter obtained by quantizing the spectrum parameter calculated by the interpolation analysis circuit to the buffer circuit, and an interpolation function accumulated by the interpolation table circuit And the quantized spectrum parameter stored in the buffer circuit and quantized by the quantization circuit A spectrum parameter extracting device, comprising: an interpolating circuit that calculates an interpolating spectrum parameter using the latest quantized spectrum parameter obtained as above and outputs the interpolating spectrum parameter to an output terminal. 2. An analysis window circuit for cutting out an input signal inputted from an input terminal with an analysis window, an interpolation table circuit for accumulating an interpolation function, a buffer circuit for receiving and accumulating a spectrum parameter, and the buffer circuit. An interpolation analysis circuit that calculates the latest spectrum parameter using the stored spectrum parameter, the input signal cut out by the analysis window circuit, and the interpolation function stored by the interpolation table circuit, and outputs the calculated spectrum parameter to the buffer circuit, The interpolation spectrum parameter is calculated by using the interpolation function accumulated by the interpolation table circuit, the spectrum parameter accumulated by the buffer circuit, and the latest spectrum parameter obtained by calculation by the interpolation analysis circuit, and is output to the output terminal. A spectrum parameter extraction device, comprising: an interpolation circuit for outputting. 3. An analysis window circuit for cutting out an input signal input from an input terminal with an analysis window, an interpolation table circuit for accumulating an interpolation function, and a quantized spectrum parameter obtained by quantizing a spectrum parameter for storage. The latest spectrum parameter is calculated and output using the buffer circuit, the quantized spectrum parameter stored in the buffer circuit, the input signal cut out by the analysis window circuit, and the interpolation function stored in the interpolation table circuit. And a quantization circuit for outputting the latest quantized spectrum parameter obtained by quantizing the spectrum parameter calculated by the interpolation analysis circuit to the buffer circuit and the output terminal. Extractor. 4. An analysis window circuit for cutting out an input signal input from an input terminal at an analysis window, an interpolation table circuit for accumulating an interpolation function, a buffer circuit for receiving and accumulating a spectrum parameter, and the buffer circuit. Interpolation analysis for calculating the latest spectrum parameter using the accumulated spectrum parameter, the input signal cut out by the analysis window circuit, and the interpolation function accumulated by the interpolation table circuit, and outputting it to the output terminal and the buffer circuit. A spectral parameter extracting apparatus comprising: a circuit.