JPH07177101A - Quantizer - Google Patents

Abstract

PURPOSE:To attain the quantization while keeping correlation between stereo input signals. CONSTITUTION:A sum output STD1(STD2) obtained by adding a stereo dither signal SDZ1(SDZ2) generated by a stereo dither signal generating circuit 5 to a digitized stereo input signal ST1(ST2) received from an input terminal 1(2) at a 1st dither adder circuit 3 (2nd dither sum circuit 4) is fed to a 1st quantizer 6 (2nd quantizer 7), and the 1st quantizer 6 (2nd quantizer 7) applies quantization and word length limit to the sum output STD1(STD2) and a quantized output Q1(Q2) is outputted from an output terminal 8(9).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a quantizer, and more particularly to a quantizer for quantizing and limiting the word length of a digitized stereo input signal.

[0002]

2. Description of the Related Art Some conventional quantizers are provided with a dither adder circuit in order to improve reproducibility in order to reduce loss of information of a minute signal which occurs when performing quantization and word length limitation. .

This conventional quantizer is disclosed in Japanese Patent Laid-Open No. 05-1.
As disclosed in the specification and drawings of No. 45376, when quantizing digital data, by limiting the word length by rounding or truncation processing, a small signal before quantization having a substantially sine wave shape can be obtained. In order to prevent deterioration of reproducibility such as waveform loss or level shift due to loss of information contained in the minute signal, a dither addition circuit is provided in front of the quantizer. A dither signal is added to the digital data in the circuit. Therefore, even if the added dither signal is quantized and then the predetermined number of lower bits is rounded down or rounded off, the quantized data will have information that the minute signal of the input signal has. It is possible to further reduce the loss of information of a minute signal caused by the length limitation.

[0004]

By the way, considering the digitized stereo signal as the digital signal, the right stereo signal is used as the right quantizer and the left stereo signal is used as the left quantizer. When inputting, if the same dither signal or dither signals uncorrelated with each other are given to the left and right dither addition circuits provided in the preceding stage, the left and right mutual relationships originally possessed by the stereo input signal will be hindered. .

For example, when the same dither signal having a cross-correlation coefficient of "1" is applied to the left and right dither adder circuits, the cross-correlation of the left and right low-correlation components is essentially increased. Specifically, the sound field feeling created by the stereo reverberation component in the music signal does not spread sufficiently to the left and right, and is concentrated on the center side.

Further, for example, when mutually uncorrelated dither signals having a cross-correlation coefficient of "0" are applied to the left and right dither addition circuits, the left-right cross-correlation coefficient is originally "1". Such ingredients are reduced. Specifically, the sound image of the center localized sound in the music signal blurs and spreads left and right.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a quantizer which does not hinder the cross-correlation of stereo signals.

[0008]

A quantizer according to the present invention is a quantizer which performs quantization and word length limitation on a digitized stereo input signal and has at least two systems that are uncorrelated with each other. Stereo dither signal generating means for generating a stereo dither signal by mixing and combining dither signals at an arbitrary ratio, and a first dither signal for adding one of the stereo dither signals to one of the digitized stereo inputs. Addition means and second addition means for adding the other of the stereo dither signals to the other of the digitized stereo input, and quantization and word length limitation on the output signal of the first addition means. The above problem can be solved by having the first quantizing means for performing the quantization and the second quantizing means for subjecting the output signal of the second adding means to the quantization and the word length limitation.

In this case, the stereo dither signal generating means generates first and second dither signal uncorrelated with the first and second dither signal generating means, and the first dither signal is arbitrary. First multiplication means for multiplying the coefficients,
Second multiplication means for multiplying the second dither signal by an arbitrary coefficient, third addition means for adding the multiplication output of the first multiplication means and the second dither signal, and the second It has a fourth adding means for adding the multiplication output of the multiplying means and the first dither signal, and third and fourth quantizing means for quantizing the outputs of the third and fourth adding means, respectively. .

Further, the stereo dither signal generating means includes first, second and third dither signal generating means for generating first, second and third dither signals which are uncorrelated with each other.
First multiplication means for multiplying the third dither signal by an arbitrary coefficient, and third and fourth addition means for adding the multiplication outputs of the first multiplication means to the first and second dither signals, respectively. Means and third and fourth quantizing means for quantizing the outputs of the third and fourth adding means, respectively.

The stereo dither signal generation means controls the mixing ratio of the at least two systems of uncorrelated dither signals based on the cross correlation of the stereo input signals.

Further, the stereo dither signal generating means includes an analyzing means for analyzing a cross-correlation coefficient of the stereo input signal at predetermined time intervals, and a mutual phase relationship between the stereo input signal obtained by the analyzing means. And a coefficient calculating means for calculating a cross-correlation coefficient of the stereo dither signal based on the number, and a stereo dither signal having the same cross-correlation coefficient as the cross-correlation coefficient of the stereo input signal or an arbitrary multiple cross-correlation coefficient. To generate.

[0013]

At least two systems of stereo dither signal generating means are provided in the first adding means provided in the preceding stage of the first quantizing means and the second adding means provided in the preceding stage of the second quantizing means. Since the dither signals uncorrelated with each other are mixed at an arbitrary ratio and combined to generate the stereo dither signals having an arbitrary cross correlation, the cross correlation of the stereo signals can be maintained.

At that time, the cross-correlation of the stereo input signal is calculated for each arbitrary time section, and the mixing ratio of the dither signals is calculated for each time section so that the stereo dither signal has a cross-correlation proportional to the value. Since the adjustment is performed, the cross-correlation of the stereo signals can be further maintained, and the loss of the left-right cross-correlation information that the stereo input signal originally had can be reduced.

[0015]

EXAMPLES Two examples of the quantizer according to the present invention (hereinafter, referred to as a first example and a second example) will be described below.
A description will be given with reference to the drawings.

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

The first embodiment has a structure as shown in FIG.

That is, one of the digitized stereo input signals ST ₁ supplied through the input terminal ₁ is
It is input to the first dither addition circuit 3. The other digitized stereo input signal ST ₂ supplied through the input terminal 2 is input to the second dither addition circuit 4 as shown in FIG.

Stereo dither signals SDZ ₁ and SDZ ₂ are also input from the stereo dither signal generator 5 to the first dither addition circuit 3 and the second dither addition circuit 4. Therefore, the first dither addition circuit 3 adds the stereo dither signal SDZ ₁ to one ST ₁ of the stereo input signals. Further, the second dither addition circuit 4 adds the stereo dither signal SDZ ₂ to the other ST ₂ of the stereo input signals.

Addition output STD of the first dither addition circuit 3
₁ is supplied to the first quantizer 6. The addition output STD ₂ of the second dither addition circuit 4 is supplied to the second quantizer 7. Here, the first quantizer 6 quantizes the addition output STD ₁ and limits the word length, and supplies the quantized output Q ₁ to the output terminal 8. Further, the second quantizer 7 quantizes the addition output STD ₂ and limits the word length, and supplies the quantized output Q ₂ to the output terminal 9.

In this first embodiment, the stereo input signal is 20 bits and the output signal is 16 bits,
The stereo dither signal is 4 bits. By adding the dither signal to the lower 4 bits of the stereo input signal,
Even after the quantization processing from 20 bits to 16 bits, the information held by the minute signal of the stereo input signal remains.

Here, the stereo dither signal generator 5 is
As shown in FIG. 2, three dither signal generators 11, 12 and 13 for generating _three uncorrelated dither signals DZ ₁ , DZ ₂ and DZ ₃ and these three dither signal generators 11, 12 are shown. And dither signals DZ ₁ , DZ _{2 from}
And DZ ₃ using multiplier coefficients K _A , K _B, and K _C , and multipliers 15, 15 and 16 and these multipliers 14, 15
And 16 of the multiplication outputs MDZ ₁ , MDZ ₂ and MDZ ₃ , an adder 17 for adding the multiplication output MDZ ₂ and the multiplication output MDZ ₁ , and an adder 18 for adding the multiplication output MDZ ₂ and the multiplication output MDZ ₃ . The adders 17 and 18 are composed of quantizers 19 and 20 for quantizing and summing the addition outputs AD ₁ and AD ₂ , respectively.
Output stereo dither signals SDZ ₁ and SDZ ₂ from the output terminals 21 and 22 and supply them to the first dither addition circuit 3 and the second dither addition circuit 4 shown in FIG.

Here, the dither signal generator 11 generates a dither signal dedicated to the stereo left side, and the dither signal generator 1
3 generates a dither signal dedicated to the right side of the stereo, and the dither signal generator 12 generates a dither signal for both left and right.

Therefore, in the stereo dither signal generation circuit 5, the left side-only dither signal DZ ₁ generated by the dither signal generator 11 is multiplied by the multiplication coefficient K _A to obtain the multiplication result MDZ _1.
And the multiplication result MDZ ₃ obtained by multiplying the right-side dedicated dither signal DZ ₃ generated by the dither signal generator 13 by the multiplication coefficient K _C , and the left and right dither signal DZ ₂ generated by the dither signal generator 12 by the multiplication coefficient. The multiplication results MDZ ₂ multiplied by K _B are respectively added, and the addition results AD ₁ and AD ₂ are quantized and word length converted to generate stereo dither signals SDZ ₁ and SDZ ₂ having arbitrary cross-correlation coefficients. ing.

Here, the stereo dither signals SDZ ₁ and S
The cross-correlation coefficient of DZ ₂ , that is, the stereo dither cross-correlation coefficient will be described with reference to FIGS. 3 and 4.

FIGS. 3 and 4 are characteristic diagrams showing the relationship between the mixing ratio of the dither signals and the cross-correlation coefficient of the generated stereo dither signals. Both multiplication coefficients K _A and K _C are “1”. Is a graph in which the cross-correlation coefficient of the stereo dither signals SDZ ₁ and SDZ ₂ when the multiplication coefficient K _B is increased from “0” is plotted on the vertical axis. In particular, FIG. 3 shows a case where the value of the multiplication coefficient K _{B on} the horizontal axis is increased from “0” to “3”.
Indicates the case where the value of the multiplication coefficient K _{B on} the horizontal axis is increased from “0” to “20”.

In any case, when the multiplication coefficient K _B is “0”, the cross correlation coefficient is “0”, and when the multiplication coefficient K _B is “1”, the cross correlation coefficient is “0. 5 ”.
Further, as the multiplication coefficient K _B is increased, the cross correlation coefficient approaches “1”.

Therefore, the cross-correlation coefficient can be changed by changing the multiplication coefficient K _B , and a stereo dither signal having an arbitrary cross-correlation coefficient can be generated.

Further, when the multiplication output MDZ ₂ obtained by changing the multiplication coefficient K _B is supplied to the adder 17 and the adder 18, the multiplication output MDZ ₂ supplied to either one of them is made negative so that the stereo It is possible to obtain a negative cross-correlation coefficient by making the left side and the right side of the phase opposite to each other. This negative cross-correlation coefficient is used, for example, when creating a special effect in which sound can be heard from outside the speaker.

As described above, the quantizer according to the first embodiment is provided in the first stage of the first quantizer 6 and the first dither adder circuit 3 and the second quantizer 7. The stereo dither signal generation circuit 5 to the second dither addition circuit 4
Supplies stereo dither signals STD ₁ and STD ₂ with arbitrary cross-correlation generated by mixing three uncorrelated dither signals at an arbitrary ratio and synthesizing them. You can keep a relationship.

Next, FIG. 3 shows a simplified configuration of the stereo dither signal generator 5. The stereo dither signal generator 5 shown in FIG. 3 includes dither signals DZ ₁ ,
Two dither signal generators 11 and 13 for generating DZ _3.
And multipliers 15a and 15b for arbitrarily multiplying the dither signals DZ ₁ and DZ ₃ from these two dither signal generators 11 and 13, respectively, using a multiplication coefficient K _B , and the two dither signal generators 11 and 13 described above. _A multiplier 14 that arbitrarily multiplies the dither signals DZ ₁ and DZ ₃ from R ₁ by using multiplication coefficients K _A and K _C , respectively.
16, an adder 17 for adding the output MDZ ₂ 'of the multiplier 15b and the output MDZ ₁ of the multiplier 14, and a multiplier 15a
Of the output MDZ ₂ ″ of the multiplier 16 and the output MDZ ₃ of the multiplier 16 and a quantizer 19 for quantizing and summing the addition outputs AD ₁ and AD ₂ from the adders 17 and 18, respectively. , 20 to output stereo dither signals SDZ ₁ and SDZ ₂ from these quantizers 19 and 20, and output the first dither addition circuit 3 and the second dither addition circuit 3 shown in FIG. Supply to 4.

In this way, the stereo dither signal generator 5
In the case where the two dither signal generators 11 and 13 are provided, the cross-correlation coefficient of the stereo dither signal cannot be completely set to "0" or "1", and the intermediate value thereof can be arbitrarily set. It can only be set, but it can have a very simple configuration.

Next, a second embodiment will be described with reference to FIGS. 6 and 7.

The second embodiment has a structure as shown in FIG.

That is, one ST of the digitized stereo input signal supplied through the input terminal 31
₁ is input to the first dither addition circuit 33, and
It is also input to the stereo dither signal generator 35. Also,
The other digitized stereo input signal ST ₂ supplied through the input terminal 32 is input to the second dither addition circuit 34, and the stereo dither signal generator 3
It is also input to 5.

The first dither addition circuit 33 and the second dither addition circuit 33
The stereo dither signal generators 35 also input the stereo dither signals SDZ ₁ and SDZ _{2 to} the dither addition circuit 34. Therefore, the first dither addition circuit 33 applies the stereo dither signal SD to _one of the stereo input signals ST _1.
Add Z ₁ . Further, the second dither addition circuit 34
On the other side of the stereo input signal ST ₂ , the stereo dither signal S
Add DZ ₂ .

Addition output ST of the first dither addition circuit 33
D ₁ is supplied to the first quantizer 36. Also, the second
The addition output STD ₂ of the dither addition circuit 34 is supplied to the second quantizer 37. Here, the first quantizer 36
Quantizes the addition output STD ₁ and limits the word length, and supplies the quantized output Q ₁ to the output terminal 38. Further, the second quantizer 37 quantizes the addition output STD ₂ and limits the word length, and supplies the quantized output Q ₂ to the output terminal 39.

Also in this second embodiment, the stereo input signal is 20 bits and the output signal is 16 bits,
The stereo dither signal is 4 bits. By adding the dither signal to the lower 4 bits of the stereo input signal,
Even after the quantization processing from 20 bits to 16 bits, the information held by the minute signal of the stereo input signal remains.

The second embodiment differs from the first embodiment in that the stereo dither signal generation circuit 35 takes in a stereo input signal and analyzes the cross-correlation coefficient of the stereo input signal at every arbitrary time interval. , A stereo dither signal having a cross-correlation coefficient equal to or arbitrary times the cross-correlation coefficient of this stereo input signal is generated.

The stereo dither signal generation circuit 35 is
As shown in FIG. 7, three dither signal generators 41, 42 and 43 for generating _three uncorrelated dither signals DZ ₁ , DZ ₂ and DZ ₃ , and an input terminal 53 and an input terminal 53 for each arbitrary time interval. Stereo input signals ST ₁ and S via 54
An analyzer 55 for analyzing the cross-correlation coefficient of T _{2 and} a cross-correlation coefficient of the stereo dither signal based on the cross-correlation coefficient of the stereo input signals ST ₁ and ST ₂ obtained by the analysis by the analyzer 55. And a dither signal DZ from the above three dither signal generators 41, 42 and 43.
_A multiplier 44 that arbitrarily multiplies ₁ , DZ ₂ and DZ ₃ using the multiplication coefficients K _A , K _B and K _C supplied from the coefficient calculator 56,
45 and 46, and the multiplication output M of the multiplication outputs MDZ ₁ , MDZ ₂ and MDZ ₃ of the multipliers 44, 45 and 46.
An adder 47 for adding DZ ₂ and the multiplication output MDZ ₁ , and an adder 48 for adding the multiplication output MDZ ₂ and the multiplication output MDZ _3.
And quantizers 49 and 50 for quantizing and summing the addition outputs AD ₁ and AD ₂ from the adders 47 and 48. From these quantizers 49 and 50, stereo dither signals SDZ ₁ and SDZ are provided. ₂ and outputs from the output terminals 51 and 52 the first dither addition circuit 3 shown in FIG.
3 and the second dither addition circuit 34.

Here, the dither signal generator 41, the dither signal generator 42, and the dither signal generator 43 convert the dither signal dedicated to the left side of the stereo to the dither signal dedicated to the right side of the stereo, as in the first embodiment. And dither signals for both left and right are generated.

Therefore, in the stereo dither signal generation circuit 35, the left-side dedicated dither signal DZ ₁ generated by the dither signal generator 41 is multiplied by the multiplication coefficient K _A obtained through the analyzer 55 and the coefficient calculator 56. The multiplication result MDZ ₁ and
The dither signal generator 42 produces a multiplication result MDZ ₃ obtained by multiplying the right-side dedicated dither signal DZ ₃ produced by the dither signal generator 43 by the multiplication coefficient K _C obtained through the analyzer 55 and the coefficient calculator 56. Generated dither signal for left and right DZ ₂
Is added to the multiplication result MDZ ₂ obtained by multiplying the multiplication coefficient K _B obtained through the analyzer 55 and the coefficient calculator 56, and the addition results AD ₁ and AD ₂ are quantized and word length converted to an arbitrary value. Stereo dither signals SDZ ₁ and SDZ ₂ having a cross-correlation coefficient are generated.

Also in the second embodiment, the cross-correlation coefficient of the stereo dither signals SDZ ₁ and SDZ ₂ , that is, the stereo dither cross-correlation coefficient can be explained with reference to FIGS. 3 and 4 above. .

Also in the second embodiment, a negative cross-correlation coefficient can be obtained as in the first embodiment.

Further, also in the second embodiment, the stereo dither signal generator can be constructed by including two dither signal generators.

As described above, the quantizing device of the second embodiment calculates the cross-correlation of the stereo input signal for each arbitrary time interval and dithers the stereo dither signal so as to have the cross-correlation proportional to the value. Since the mixing ratio of the signals is adjusted for each time section, the cross-correlation relationship of the stereo signals can be further maintained, and the loss of the left-right cross-correlation information that the stereo input signal originally has can be reduced.

The quantizer according to the present invention is not limited to the first and second embodiments, and can be applied to, for example, a stereo panpot used in a digital mixer. is there.

[0048]

The quantizer according to the present invention is a quantizer which performs quantization and word length limitation on a digitized stereo input signal, and at least two systems of uncorrelated dither signals are arbitrarily selected. Stereo dither signal generation means for mixing and synthesizing at a ratio of 1 to generate a stereo dither signal, and first addition means for adding one of the stereo dither signals to one of the digitized stereo inputs, Second addition means for adding the other of the stereo dither signals to the other of the digitized stereo input, and first output means for quantizing and limiting the word length of the output signal of the first adding means. Quantizing means, and the second
Second quantizing and limiting the word length of the output signal of the adding means
Quantization means can be used to perform quantization while maintaining the left-right cross-correlation originally possessed by the stereo input signal.

Further, the stereo dither signal generating means includes an analyzing means for analyzing a cross-correlation coefficient of the stereo input signal for each predetermined time interval, and a mutual phase relationship between the stereo input signal obtained by the analyzing means. And a coefficient calculating means for calculating a cross-correlation coefficient of the stereo dither signal based on the number, and a stereo dither signal having the same cross-correlation coefficient as the cross-correlation coefficient of the stereo input signal or an arbitrary multiple cross-correlation coefficient. Is generated, the quantization can be performed in a state where the cross-correlation of the stereo signals is further maintained, and the loss of the left-right cross-correlation information originally possessed by the stereo input signal can be reduced.

[Brief description of drawings]

FIG. 1 is a block circuit diagram showing a configuration of a first embodiment of a quantization device according to the present invention.

FIG. 2 is a block circuit diagram showing a configuration of a stereo dither signal generation circuit of the first embodiment.

FIG. 3 is a characteristic diagram for explaining a cross-correlation coefficient of a stereo dither signal.

FIG. 4 is a characteristic diagram for explaining a cross-correlation coefficient of a stereo dither signal.

FIG. 5 is a block diagram showing another configuration of the stereo dither signal generation circuit of the first embodiment.

FIG. 6 is a block circuit diagram showing a configuration of a second embodiment of a quantization device according to the present invention.

FIG. 7 is a block circuit diagram showing a configuration of a stereo dither signal generation circuit of the second embodiment.

[Explanation of symbols]

 3, 33 ... First dither addition circuit 4, 34 ... Second dither addition circuit 5, 35 ... Stereo dither signal generation circuit 6, 36 ... First quantization Unit 7, 37 ... Second quantizer

Claims (5)

[Claims] 1. A quantizer for quantizing and limiting a word length of a digitized stereo input signal, wherein at least two systems of uncorrelated dither signals are mixed at an arbitrary ratio and combined to form a stereo. Stereo dither signal generation means for generating a dither signal, and one of the digitized stereo input,
First adding means for adding one of the stereo dither signals, and the other of the digitized stereo inputs,
Second adding means for adding the other of the stereo dither signals, first quantizing means for quantizing and limiting the word length of the output signal of the first adding means, and output of the second adding means A second quantizing means for quantizing and limiting the word length of the signal. 2. The stereo dither signal generation means includes first and second dither signal generation means for generating first and second dither signals that are uncorrelated with each other, and an arbitrary coefficient for the first dither signal. A first multiplication means for multiplying the second dither signal, a second multiplication means for multiplying the second dither signal by an arbitrary coefficient, a second multiplication means for adding the multiplication output of the first multiplication means and the second dither signal Third adding means, fourth multiplying means for adding the multiplication output of the second multiplying means and the first dither signal, and third quantizing the outputs of the third and fourth adding means, respectively. And a fourth quantizing means. 4. The quantizing apparatus according to claim 1, further comprising: 3. The stereo dither signal generating means includes first, second and third dither signal generating means for generating first, second and third dither signals which are uncorrelated with each other, and the third dither signal generating means. First multiplication means for multiplying the dither signal by an arbitrary coefficient, third and fourth addition means for adding the multiplication outputs of the first multiplication means to the first and second dither signals, respectively, The quantizing device according to claim 1, further comprising third and fourth quantizing means for quantizing the outputs of the third and fourth adding means, respectively. 4. The stereo dither signal generation means controls the mixing ratio of the at least two systems of uncorrelated dither signals based on the cross correlation of the stereo input signals. Quantizer. 5. The stereo dither signal generating means includes an analyzing means for analyzing a cross-correlation coefficient of the stereo input signal at predetermined time intervals, and a mutual phase relationship between the stereo input signals obtained by the analyzing means. And a coefficient calculating means for calculating the cross-correlation coefficient of the stereo dither signal on the basis of the number, and a stereo dither signal having the same cross-correlation coefficient as the cross-correlation coefficient of the stereo input signal or an arbitrary multiple cross-correlation coefficient. The quantizing device according to claim 4, wherein