JP2000165300A - Method and system for identifying unknown system using sub band adaptive filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a method and a system for identifying an unknown system where the best adaptive algorithm is adaptively selected and a redundant tap length is used effectively so as to enhance the performance thereby effectively utilizing an arithmetic amount. SOLUTION: An input signal of an unknown system is subject to sub-band split processing to generate a plurality of sub band reference signals, a plurality of the sub band reference signals are given to a plurality of independent sub band adaptive filters 21-23, an output signal of the unknown system is subject to sub band split processing to generate a plurality of sub band object signals, a difference between a plurality of the sub band object signals and output signals of the sub band adaptive filters is outputted as a sub band error signal, which is used to update a filter coefficient of a sub band adaptive filter, and each adaptive algorithm used to update the filter coefficient of the sub band adaptive filter is selected and its tap length is calculated, it is converted into a control signal, which is fed to each sub band adaptive filter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for identifying an unknown system using a subband adaptive filter, and more particularly to an unknown system such as an acoustic echo canceller in a transmission path or space using a subband adaptive filter. And a method and apparatus for identifying an unknown system.

[0002]

2. Description of the Related Art Hitherto, examples of applications for identifying an unknown system using a subband adaptive filter include an acoustic echo canceller, a noise canceller, and an adaptive equalizer. Here, a conventional technique will be described using an acoustic echo canceller as a representative example. 2. Description of the Related Art Conventionally, various people in remote locations share video, audio, and the like. For example, various video and audio communication systems in a wide range of fields such as a TV conference system, a telephone conference system, a loudspeaker system, and a monitoring system have been developed. .

[0003] In these systems, it is common to use a speaker and a microphone instead of using a handset for voice. Therefore, for example, the voice uttered from the far-end speaker output from the near-end speaker,
At the near end, the sound wraps around the near-end microphone as an acoustic echo and is output again from the far-end speaker. At the far-end side, the voice uttered by the far-end speaker toward the microphone is transmitted from the far-end speaker to the far-end speaker. An echo state occurs in which the speaker returns to the ear of the speaker with a delay, and a state occurs in which the call becomes very difficult.

One means for suppressing the acoustic echo is to use an acoustic echo canceller. The acoustic echo from the speaker to the microphone is estimated using an adaptive filter, and a pseudo echo is generated to generate a pseudo echo. It acts to suppress acoustic echo by subtracting the pseudo echo from the received signal.

FIG. 6 shows an example of means for suppressing an acoustic echo using the above-mentioned conventional acoustic echo canceller. FIG. 6 is an explanatory diagram of a conventional acoustic echo canceller using a subband adaptive filter. In this conventional example, an acoustic echo canceller on the near-end speaker side is assumed. 6, 1 is a reception signal input terminal, 2 is a D / A converter, 3 is an amplifier, 4 is a speaker, 5 is an acoustic echo, 6 is a microphone, 7 is an amplifier, 8 is an A / D converter, and 9 is A transmission signal output terminal, 11 is a sub-band division processing unit, 12 is a sub-band division processing unit, 13 is a sub-band synthesis processing unit, 20 is a sub-band adaptive filter group, 21 is a sub-band adaptive filter unit, and 22 is a sub-band adaptation unit. A filter unit, 23 is a subband adaptive filter unit, 31 is an adder, 32 is an adder, and 33 is an adder.

Next, the operation of the acoustic echo canceller using the conventional subband adaptive filter will be described with reference to FIG. First, an audio signal transmitted from the far end is input to a reception signal input terminal 1 of the near-end acoustic echo canceller, converted into an analog signal by the D / A converter 2, and amplified to a predetermined level by the amplifier 3. Output from the speaker 4. The output audio signal goes around the microphone 6 as shown by the acoustic echo 5. The audio signal picked up by the microphone 6 is amplified to a predetermined level by the amplifier 7 and
The digital signal is converted by the D converter 8. The converted digital signal is input to the sub-band division processing unit 12, where sub-band division processing is performed to generate a plurality of sub-band target signals.

[0007] The sub-band division processing section 11 performs sub-band division processing on the audio signal received at the reception signal input terminal 1 to generate a sub-band reference signal. The plurality of generated subband reference signals are input to the subband adaptive filter group 20 and supplied to independent subband adaptive filter units AFi (i = 1 to n) 21 to 23, respectively. From the plurality of subband target signals output from the subband division processing unit 12, the outputs of the corresponding subband adaptive filter units 21 to 23 are respectively added to adders 31 to 33.
, The acoustic echo 5 is canceled and the adders 31 to 33 generate a plurality of sub-band error signals.

The generated plurality of sub-band error signals are supplied to sub-band adaptive filters 21 to 23, respectively, and are used for updating coefficients in a filter coefficient updating algorithm in each of sub-band adaptive filters 21 to 23. As shown in FIG. 7, each of the subband adaptive filter sections 21 to 23 includes an adaptive filter coefficient correction section 41 and an FIR filter 42. Adaptive filter coefficient correction unit 4
1 receives the sub-band reference signal and the sub-band error signal, and updates the adaptive filter coefficient to be transferred to the FIR filter 42 according to the selected adaptive algorithm. On the other hand, the FIR filter 42 receives the subband reference signal and the adaptive filter coefficient, outputs a pseudo echo for canceling the acoustic echo 5, and inputs the pseudo echo to the adders 31 to 33.

A plurality of sub-band error signals output from the adders 31 to 33 are input to a sub-band synthesizing unit 13 and subjected to sub-band synthesizing processing, and then output from a transmission signal output terminal 9. However, in the conventional example of the acoustic echo canceller, functions mounted on the acoustic echo canceller, such as the double talk detection unit and the suppressor unit, are omitted.

Here, the subband adaptive filter units 21 to
23 will be described. Subband adaptive filter section 21
Representative examples of the adaptive algorithm for updating the coefficients used in .about.23 include an LMS algorithm, a learning identification method, a high-speed RLS algorithm, and the like.
The LMS algorithm, the learning identification method, and the like require a small amount of calculation for updating the coefficient, but the convergence speed is slow and the echo canceling performance is degraded for a color signal such as an audio signal.

On the other hand, the high-speed RLS algorithm requires a large amount of computation. However, even for a signal having a color, the echo elimination performance and the convergence speed are extremely superior to those of the LMS algorithm and the learning identification method. have. Conventionally, LMS or a learning identification method, which requires a small amount of calculation, is generally used in order to keep the amount of calculation limited by hardware.

[0012]

However, in the above-described method for identifying an unknown system using the conventional subband adaptive filter, for example, the learning identification method is entirely employed in the adaptive filter coefficient updating algorithm for the subband.
The tap length of the adaptive filter unit is determined in consideration of the limitation of the amount of calculation on hardware. Taking an acoustic echo canceller as an example, if the echo canceling time of the acoustic echo canceller device is, for example, 200 ms, that is, if the acoustic echo canceller device has a filter tap length equivalent to 200 ms, it is necessary for actual acoustic echo canceling. Assuming that the required time is 150 ms, the remaining 5
There is a problem that the amount of calculation required for updating the filter coefficient having a tap length corresponding to 0 ms is not effectively used.

The present invention has been made to solve the above-mentioned conventional problem, and conventionally employs, for example, a learning identification method in order to effectively use a calculation amount necessary for updating a coefficient of a redundant tap length. The adaptive algorithm of the adaptive filter unit of the subband is changed to, for example, a high-speed RLS algorithm having excellent echo canceling performance and convergence speed for some subbands, and in particular, while improving echo canceling performance and convergence speed for a colored signal, Change the algorithm by registering the number of subbands and tap length in advance as a set pattern and calling it.Also, by controlling the number of subbands and tap length adaptively to improve performance, the amount of computation can be effectively used Method and apparatus for identifying unknown systems using available superior subband adaptive filters An object of the present invention is to provide a.

[0014]

According to the present invention, in order to solve the above-mentioned problems, an input signal of an unknown system is subjected to sub-band division processing to generate a plurality of sub-band reference signals, and a plurality of sub-band reference signals are generated. Input to a plurality of independent subband adaptive filters, subband split the output signal of the unknown system to generate a plurality of subband target signals, and output the plurality of subband target signals and the output signal of the subband adaptive filter. And outputs the difference as a sub-band error signal, updates the filter coefficients of the sub-band adaptive filter using the sub-band error signal, and further selects various adaptive algorithms used for updating the filter coefficients of the sub-band adaptive filter, It also calculates the tap length, converts it to a control signal, and supplies it to each subband adaptive filter. That.

According to the present invention, the adaptive algorithm of the adaptive filter unit of the sub-band, which has conventionally adopted, for example, a learning identification method, is partially used in order to effectively use the operation amount required for updating the coefficient of the redundant tap length. Another adaptive algorithm having excellent echo cancellation performance and convergence speed for a subband, for example, a high-speed RLS algorithm is used to improve the performance and use an excellent subband adaptive filter that can effectively use the amount of calculation. A system identification method and apparatus is provided.

According to the present invention, in order to solve the above problem, an input signal of an unknown system is subjected to subband division processing to generate a plurality of subband reference signals, and the plurality of subband reference signals are converted to a plurality of independent subbands. Input to the adaptive filter,
Sub-band division processing of the output signal of the unknown system to generate a plurality of sub-band target signals, and outputs a difference between the plurality of sub-band target signals and the output signal of the sub-band adaptive filter as a sub-band error signal, The filter coefficient of the sub-band adaptive filter is updated using the sub-band error signal, and the plurality of sub-band target signals, sub-band reference signals or sub-band error signals are evaluated. Various adaptive algorithms to be used for updating the filter coefficients of the band adaptive filter are selected, the tap length is calculated, and the calculated tap length is converted into a control signal to be supplied to each subband adaptive filter.

According to the present invention, the adaptive algorithm of the adaptive filter unit of the sub-band, which conventionally employs, for example, a learning identification method, is partially used in order to effectively use the operation amount necessary for updating the coefficient of the redundant tap length. Evaluate the sub-band target signal, sub-band reference signal or sub-band error signal when changing to another adaptive algorithm with excellent echo cancellation performance and convergence speed for the sub-band, for example, changing to the fast RLS algorithm to improve the performance. By changing the adaptive algorithm based on the result of the evaluation, an unknown system identification method and apparatus using an excellent subband adaptive filter that can effectively use the computation amount can be obtained.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the first aspect of the present invention, a plurality of sub-band reference signals are generated by subjecting an input signal of an unknown system to sub-band division processing, and the plurality of sub-band reference signals are divided into a plurality of sub-band reference signals. Input to the independent subband adaptive filter, and output signals of the unknown system are subjected to subband division processing to generate a plurality of subband target signals, and the plurality of subband target signals and the output signal of the subband adaptive filter. And outputting the difference from the sub-band adaptive filter as a sub-band error signal, and using the sub-band error signal to update the filter coefficient of the sub-band adaptive filter, the identification method of an unknown system, Various adaptive algorithms used for updating the filter coefficient are selected for each subband, and the tap length of each subband is calculated, The result of the selection of the adaptive algorithm and the result of the tap length calculation are converted into a control signal for a subband adaptive filter group and supplied to each subband adaptive filter. By changing the adaptive algorithm of the band adaptive filter unit to, for example, a high-speed RLS algorithm having excellent echo canceling performance and convergence speed for some subbands, the amount of computation required for updating filter coefficients with redundant tap lengths can be effectively reduced. It has the effect that it can be used to improve the identification performance of unknown systems.

According to a second aspect of the present invention, an input signal of an unknown system is subjected to subband division processing to generate a plurality of subband reference signals, and the plurality of subband reference signals are converted to a plurality of independent subbands. Input to the band adaptive filter,
The output signal of the unknown system is subjected to subband division processing to generate a plurality of subband target signals, and a difference between the plurality of subband target signals and the output signal of the subband adaptive filter is output as a subband error signal. An identification method of an unknown system comprising the steps of updating a filter coefficient of the sub-band adaptive filter using the sub-band error signal, wherein an adaptive algorithm and a tap length of a plurality of patterns are registered in advance, and the registered A plurality of adaptive algorithms used for updating the filter coefficients of the sub-band adaptive filter for each sub-band from a plurality of patterns of adaptive algorithms and tap lengths, and calculating a tap length; and selecting the adaptive algorithm and the tap. The result of length calculation is used as a control signal for the subband adaptive filter group. In other words, a plurality of patterns of adaptive algorithms and tap lengths are registered in advance, and the adaptive algorithm and tap length patterns are called and selected therefrom. This has the effect of effectively utilizing the limited amount of calculation and improving the identification performance of the unknown system with an easy operation method.

According to a third aspect of the present invention, an input signal of an unknown system is subjected to subband division processing to generate a plurality of subband reference signals, and the plurality of subband reference signals are divided into a plurality of independent subbands. Input to the band adaptive filter,
The output signal of the unknown system is subjected to subband division processing to generate a plurality of subband target signals, and a difference between the plurality of subband target signals and the output signal of the subband adaptive filter is output as a subband error signal. An identification method of an unknown system including a step of updating a filter coefficient of the sub-band adaptive filter using the sub-band error signal, wherein the plurality of sub-band target signals are evaluated, and a result of the evaluation is also obtained. And selecting various adaptive algorithms used for updating the filter coefficients of the sub-band adaptive filter for each sub-band, calculating the tap length of each sub-band, selecting the adaptive algorithm and selecting the tap length calculation. The result is converted to a control signal for the subband adaptive filter group and supplied to each subband adaptive filter. Evaluates multiple subband target signals, and adaptively selects an adaptive algorithm and calculates tap length based on the evaluation result, effectively using the limited amount of computation. This has the effect that the identification performance of the unknown system can be easily improved.

The invention according to claim 4 of the present invention includes a step of evaluating a plurality of sub-band reference signals instead of the step of evaluating a plurality of sub-band target signals according to claim 3, and Various adaptive algorithms used for updating the filter coefficients of the sub-band adaptive filter are selected for each sub-band based on the result, the tap length of each sub-band is calculated, the selection result of the adaptive algorithm and the tap The result of the length calculation is converted into a control signal for the sub-band adaptive filter group and supplied to each sub-band adaptive filter, and a plurality of sub-band reference signals are evaluated. By selecting the adaptive algorithm and calculating the tap length, the limited amount of computation can be used effectively to easily identify unknown systems. An effect that can be improved.

The invention according to claim 5 of the present invention includes a step of evaluating a plurality of sub-band error signals instead of the step of evaluating the plurality of sub-band target signals according to claim 3, and Various adaptive algorithms used for updating the filter coefficients of the sub-band adaptive filter are selected for each sub-band based on the result, the tap length of each sub-band is calculated, the selection result of the adaptive algorithm and the tap It consists of each step of converting the result of length calculation into a control signal for a subband adaptive filter group and supplying the control signal to each subband adaptive filter, and evaluates a plurality of subband error signals, and evaluates the evaluation result. The adaptive algorithm selection and the tap length calculation are adaptively performed by using the An effect that it is possible to improve the Temu identification performance.

According to a sixth aspect of the present invention, there is provided a sub-band division processing section for performing sub-band division processing on an input signal of an unknown system to generate a plurality of sub-band reference signals; A plurality of independent subband adaptive filters for inputting and processing band reference signals, and a plurality of second subband division processing units for performing subband division processing on the output signal of the unknown system to generate a plurality of subband target signals And an adding unit that outputs a difference between the plurality of sub-band target signals and the output signal of the sub-band adaptive filter as a sub-band error signal. Selecting means for selecting various adaptive algorithms used for updating the filter coefficients for each subband, and a tap length of each subband. A tap length calculating means for outputting the selected result of the adaptive algorithm and a result of the tap length calculation into a control signal for a subband adaptive filter group and supplying the control signal to each subband adaptive filter. The selection of the adaptive algorithm used for updating the filter coefficient of the band adaptive filter and the calculation of the tap length are performed for each subband, so that the redundant tap length is reduced and the adaptation of the subband adaptive filter unit is performed. By changing the algorithm to, for example, a high-speed RLS algorithm having excellent echo cancellation performance and convergence speed for some subbands, the amount of computation required for updating the filter coefficients of redundant tap lengths can be effectively used, and an unknown system can be used. Has the effect of improving the identification performance of

According to a seventh aspect of the present invention, there is provided a selection calculation pattern accumulator for registering adaptive algorithms and tap lengths of a plurality of patterns in advance, wherein the adaptive algorithm selecting means and the tap length calculating means store the selected algorithms. A plurality of patterns of adaptive algorithms and tap lengths are called, and various adaptive algorithms used for updating the filter coefficients of the sub-band adaptive filter are selected for each sub-band and the tap length is calculated. By registering the pattern adaptation algorithm and tap length in advance and calling and selecting the registered pattern, the limited computational amount can be used effectively, and the identification performance of unknown systems can be easily performed by an easy operation method. Can be improved.

According to an eighth aspect of the present invention, there is provided a sub-band division processing section for performing sub-band division processing on an input signal of an unknown system to generate a plurality of sub-band reference signals; A plurality of independent subband adaptive filters for inputting and processing band reference signals, and a plurality of second subband division processing units for performing subband division processing on the output signal of the unknown system to generate a plurality of subband target signals And an adding means for outputting a difference between the plurality of sub-band target signals and an output signal of the sub-band adaptive filter as a sub-band error signal. Sub-band target signal evaluation means for evaluating a signal, and updating of a filter coefficient of the sub-band adaptive filter based on a result of the evaluation Selecting means for selecting a kind adaptive algorithm for each sub-band, tap length calculating means for calculating the tap length of each sub-band, and selecting the adaptive algorithm selection result and the tap length calculating result as a sub-band adaptive filter. Control means for converting the control signal into a control signal for the group and supplying the control signal to each subband adaptive filter, and adaptively selecting an adaptive algorithm used for updating the filter coefficient of the subband adaptive filter and calculating the tap length for each subband. Limited evaluation by evaluating a plurality of subband target signals and adaptively selecting an adaptive algorithm and calculating a tap length based on the evaluation result. This has the effect that the quantity can be used effectively and the identification performance of the unknown system can be easily improved.

According to a ninth aspect of the present invention, in place of the subband target signal evaluation means for evaluating a plurality of subband target signals according to the eighth aspect, a subband for evaluating a plurality of subband reference signals is provided. A reference signal evaluation unit is selected, and various adaptive algorithms used for updating the filter coefficients of the subband adaptive filter are selected for each subband based on a result of the evaluation, and a tap length of each subband is calculated. By evaluating a plurality of subband reference signals and adaptively selecting an adaptive algorithm and calculating a tap length based on the evaluation result, a limited amount of computation is effective. The present invention has an effect that the identification performance of an unknown system can be easily improved by using it.

According to a tenth aspect of the present invention, a sub-band target signal evaluation means for evaluating a plurality of sub-band target signals is replaced with a sub-band target signal evaluation means for evaluating a plurality of sub-band error signals. An error signal evaluation unit is selected, and based on the evaluation result, various adaptive algorithms used for updating the filter coefficients of the subband adaptive filter are selected for each subband, and the tap length of each subband is calculated. By evaluating a plurality of sub-band error signals and adaptively selecting an adaptive algorithm and calculating a tap length based on the evaluation result, a limited amount of computation is effective. The present invention has an effect that the identification performance of an unknown system can be easily improved by using it.

According to an eleventh aspect of the present invention, in each of the evaluation steps, the evaluation is performed by using a square value of the input signal. By using the power value to evaluate and adaptively select the adaptive algorithm and calculate the tap length,
This has the effect that the limited calculation amount can be effectively used and the identification performance of the unknown system can be easily improved.

According to a twelfth aspect of the present invention, each of the evaluation steps is evaluated using an absolute value of an input signal, and each evaluation step is performed based on an absolute value of the input signal. By evaluating using and adaptively selecting the adaptive algorithm and calculating the tap length,
This has the effect that the limited calculation amount can be effectively used and the identification performance of the unknown system can be easily improved.

According to a thirteenth aspect of the present invention, the evaluation is performed using the square value of the signal input by each of the evaluation means, and each evaluation means performs the square value of the input signal. , And adaptively select an adaptive algorithm and calculate the tap length, so that the limited computation amount can be effectively used and the identification performance of the unknown system can be easily improved. It has the action of:

According to a fourteenth aspect of the present invention, the evaluation is performed using the absolute value of the signal input by each of the evaluation means, and each evaluation means uses the absolute value of the input signal. And adaptively select an adaptive algorithm and calculate the tap length, thereby effectively using the limited amount of computation and easily improving the identification performance of unknown systems. Having.

According to a fifteenth aspect of the present invention, an adaptive algorithm for updating the filter coefficient of the subband adaptive filter is selected from a learning identification method and a fast RLS algorithm. Since the selection of the adaptive algorithm and the calculation of the tap length can be performed from two types of the identification method and the high-speed RLS algorithm,
This has the effect that the limited calculation amount can be effectively used and the identification performance of the unknown system can be easily improved.

[0033] According to a sixteenth aspect of the present invention, an adaptive algorithm for updating the filter coefficient of the subband adaptive filter is selected from a learning identification method and a fast RLS algorithm. Since the selection of the adaptive algorithm and the calculation of the tap length can be performed from two types of the identification method and the high-speed RLS algorithm,
This has the effect that the limited calculation amount can be effectively used and the identification performance of the unknown system can be easily improved.

Hereinafter, based on the attached drawings and FIGS. 1 to 5,
An embodiment of the present invention will be described in detail. (Embodiment 1) First, an unknown system identification method and apparatus using a subband adaptive filter according to Embodiment 1 of the present invention will be described with reference to FIG. FIG. 1 is a diagram illustrating an unknown system identification method and apparatus using a subband adaptive filter according to Embodiment 1 of the present invention. In the first embodiment, an acoustic echo canceller is mentioned as a typical example of unknown system identification. That is, the acoustic echo 5 corresponds to an unknown system, and an acoustic echo canceller will be described below as an example of the unknown system identification device.

Next, the configuration of an acoustic echo canceller as an unknown system identification device using a subband adaptive filter according to the first embodiment will be described with reference to FIG. In FIG. 1, 1 is a reception signal input terminal, 2 is D / A
Converter, 3 is an amplifier, 4 is a speaker, 5 is an acoustic echo,
6 is a microphone, 7 is an amplifier, 8 is an A / D converter, 9
Is a transmission signal output terminal, 11 is a subband division processing unit, 1
2 is a subband division processing unit as a second subband division processing unit, 13 is a subband synthesis processing unit, 20 is a subband adaptive filter group, 21 is a subband adaptive filter unit, 22 is a subband adaptive filter unit, 23 is a sub-band adaptive filter unit, 31, 32 and 33 are adders as adding means, 51 is a control unit, and 52 is an adaptive algorithm selecting means and a tap length calculating means.

Next, the operation of the acoustic echo canceller using the subband adaptive filter according to the first embodiment configured as described above will be described with reference to FIG. First, an audio signal transmitted from the far end is input to a reception signal input terminal 1 of the near-end acoustic echo canceller, converted into an analog signal by the D / A converter 2, and amplified to a predetermined level by the amplifier 3. Output from the speaker 4. The output sound signal is output from the microphone 6 as shown in the acoustic echo 5.
Wrap around.

The audio signal picked up by the microphone 6 is amplified to a predetermined level by an amplifier 7 and converted to a digital signal by an A / D converter 8. The converted digital signal is input to the sub-band division processing unit 12, and performs sub-band division processing to generate a plurality of sub-band target signals. Also,
The sub-band division processing unit 11 performs sub-band division processing on the audio signal received from the input terminal 1 to generate a sub-band reference signal. These generated subband reference signals are:
Subband adaptive filter units AFi (i = 1 to n) which are input to the subband adaptive filter group 20 and are independent of each other.
21 to 23.

Each of the adders 31 to 33 subtracts the output of each of the sub-band adaptive filters 21 to 23 from each of the plurality of sub-band target signals output from the sub-band division processing unit 12, thereby obtaining the input acoustic echo 5 And a plurality of sub-band error signals are generated.
Thereafter, the generated plurality of sub-band error signals are re-supplied to the sub-band adaptive filters 21 to 23, respectively, and are used for updating the coefficients of the filter coefficient updating algorithm in each of the sub-band adaptive filters 21 to 23.
The plurality of sub-band error signals output from the adders 31 to 33 are input to the sub-band synthesis processing unit 13 and subjected to sub-band synthesis processing, and then output from the transmission signal output terminal 9. However, in this example of the acoustic echo canceller, description of functions mounted on the acoustic echo canceller, such as the double talk detection unit and the suppressor unit, is omitted for simplification.

Next, a control method of the subband adaptive filter units 21 to 23 constituting the subband adaptive filter group 20 will be described. Conventionally, the adaptive algorithm selecting means and the tap length calculating means 52 use, for example, learning so that the characteristics of the acoustic echo canceller, that is, the echo canceling characteristics and the convergence speed, are in the most excellent state in utilizing the limited amount of calculation. For one or more subbands employing the identification method, for example, a fast RL with excellent characteristics
The tap length to be reduced in each subband is calculated in order to select and use S and reduce the amount of computation that increases accordingly.

The result of the selection of the adaptive algorithm and the calculation of the tap length are transferred to the control unit 51. The control unit 51 selects the adaptive algorithm and calculates the tap length for the subband adaptive filters 21 to 23 constituting the subband adaptive filter group 20. Set the result of Here, two types of adaptation algorithms, the learning identification method and the high-speed RLS algorithm, have been presented, but many other algorithms than those used as examples can also be adapted.
It is also possible to select from more than one type of algorithm.

As described above, according to the first embodiment, the conventional learning identification method is used in order to effectively use the calculation amount required for updating the redundant tap length coefficient for identifying an unknown system (acoustic echo cancellation). The adaptive algorithm of the adaptive filter unit of the sub-band adopting the algorithm is improved to improve the performance by changing, for example, a high-speed RLS algorithm or the like which is excellent in echo cancellation performance and convergence speed for some sub-bands. By controlling the number of sub-bands and the tap length to change the amount of calculation, the amount of calculation can be effectively used, and as a result, the performance of the acoustic echo canceller can be improved.

(Embodiment 2) Next, referring to FIG.
A configuration of an acoustic echo canceller as an unknown system identification device using a subband adaptive filter according to Embodiment 2 will be described. FIG. 2 is an explanatory diagram showing an unknown system identification method and apparatus using a subband adaptive filter according to Embodiment 2 of the present invention. In FIG. 2, 61
Is a selection calculation pattern storage unit. FIG. 2 shows a configuration in which a selection calculation pattern storage unit 61 is added to FIG.
Other components are the same as those shown in FIG. 1, and thus detailed description is omitted.

Next, the operation of the acoustic echo canceller using the subband adaptive filter according to the second embodiment configured as described above will be described with reference to FIG. First, the selection calculation pattern storage unit 61 can register a representative pattern set by the adaptive algorithm selection unit and the tap length calculation unit 52, and can call the representative pattern by the adaptive algorithm selection unit and the tap length calculation unit 52. . For example, depending on the capacity of the space with respect to the acoustic space that generates the acoustic echo 5 and the material of the wall, floor, and ceiling,
The selection of the adaptive algorithm and the calculation result of the tap length calculated according to the selection are registered as some patterns. In an actual use environment, some registered patterns are called to set an optimum pattern for the subband adaptive filter group 20 through the control unit 51, and an adaptive algorithm selecting unit and a tap length calculating unit 52
, The user can set and register an optimal pattern. Added selection calculation pattern storage unit 61
Configurations and operations other than the above are the same as those described in the first embodiment, and thus description thereof will be omitted.

As described above, according to the second embodiment, the selection calculation pattern accumulating section 61 selects an adaptive algorithm according to the surrounding environment to be applied and calculates the tap length calculated accordingly. Since the results can be registered as several patterns and can be called and supplied, the limited amount of computation can be used effectively to improve the performance of the acoustic echo canceller by an easy operation method. Becomes possible.

(Embodiment 3) Next, referring to FIG.
The configuration of an acoustic echo canceller as an unknown system identification device using a subband adaptive filter according to the third embodiment will be described. FIG. 3 is an explanatory diagram showing an unknown system identification method and apparatus using a subband adaptive filter according to Embodiment 3 of the present invention. In FIG.
Is a sub-band target signal evaluation means. FIG. 3 shows a configuration in which a sub-band target signal evaluation means 71 is added to FIG. 1, and the other components are the same as those shown in FIG.

Next, the operation of the acoustic echo canceller using the subband adaptive filter according to the third embodiment configured as described above will be described with reference to FIG. First, the sub-band target signal evaluation means 71 evaluates each sub-band based on the sub-band target signals for all sub-bands obtained from the sub-band adaptive filter group 20.
Based on the evaluation result, the adaptive filter algorithm selecting means and the tap length calculating means 52 select an algorithm to be used in each subband and calculate the tap length, and transmit the tap length to the subband adaptive filter group through the control unit 51. Set for 20.

The evaluation method used here includes a method using the square value of the sub-band target signal and a method using the absolute value of the sub-band target signal. In addition, the above-described operation is adaptively repeated for evaluation, selection, calculation, and setting each time it is determined that the adaptive filter coefficient of the subband employing the high-speed RLS algorithm has converged, thereby adapting to a changing situation. Optimum settings can be made, and as a result, the performance of the acoustic echo canceller can be improved by effectively using the limited amount of calculation.

As described above, according to the third embodiment, by using the sub-band target signal evaluation means 71, it is possible to adaptively select an adaptive algorithm and calculate and set a tap length. Therefore, the performance of the acoustic echo canceller can be easily improved by effectively using the limited amount of calculation.

(Embodiment 4) Next, referring to FIG.
A configuration of an acoustic echo canceller as an unknown system identification device using a subband adaptive filter according to the fourth embodiment will be described. FIG. 4 is an explanatory diagram showing an unknown system identification method and apparatus using a subband adaptive filter according to Embodiment 4 of the present invention. In FIG. 4, 81
Is a sub-band reference signal evaluation means. FIG. 4 shows a configuration in which a sub-band reference signal evaluation unit 81 is added to FIG. 1, and the other components are the same as those shown in FIG.

Next, the operation of the acoustic echo canceller using the subband adaptive filter according to the fourth embodiment configured as described above will be described with reference to FIG. First, the subband reference signal evaluation means 81 performs evaluation based on the subband reference signals for all the subbands obtained from the subband adaptive filter group 20. Based on the evaluation result, the adaptive filter algorithm selecting means and the tap length calculating means 52 select an algorithm to be used for each subband, calculate the tap length, and transmit them to the subband adaptive filter group through the control unit 51. 20
Set for.

The evaluation method used here includes a method using the square value of the subband reference signal and a method using the absolute value of the subband reference signal. In addition, the above-described operation is adaptively repeated for evaluation, selection, calculation, and setting each time it is determined that the adaptive filter coefficient of the subband employing the high-speed RLS algorithm has converged, thereby adapting to a changing situation. Optimum settings can be made, and as a result, the performance of the acoustic echo canceller can be improved by effectively using the limited amount of calculation.

As described above, according to the fourth embodiment, the selection of the adaptive algorithm and the calculation of the tap length are performed adaptively by using the sub-band reference signal evaluation means 81, and they are set. Therefore, the performance of the acoustic echo canceller can be easily improved by effectively using the limited amount of calculation.

(Embodiment 5) Next, referring to FIG.
A configuration of an acoustic echo canceller as an unknown system identification device using a subband adaptive filter according to the fifth embodiment will be described. FIG. 5 is an explanatory diagram showing an unknown system identification method and apparatus using a subband adaptive filter according to Embodiment 5 of the present invention. In FIG. 5, 91
Is a sub-band error signal evaluation means. FIG. 5 shows a configuration in which a sub-band error signal evaluation means 91 is added to FIG. 1, and the other components are the same as those shown in FIG.

Next, the operation of the acoustic echo canceller using the subband adaptive filter according to the fifth embodiment configured as described above will be described with reference to FIG. First, the sub-band error signal evaluation means 91 performs an evaluation based on the sub-band error signals for all the sub-bands obtained from the sub-band adaptive filter group 20. Based on the evaluation result, the adaptive filter algorithm selecting means and the tap length calculating means 52 select an algorithm to be used for each subband, calculate the tap length, and transmit the tap length to the subband adaptive filter group 20 through the control unit 51. Make these settings.

The evaluation method used here includes a method using the square value of the sub-band error signal and a method using the absolute value of the sub-band error signal. In addition, the above-described operation is adaptively repeated for evaluation, selection, calculation, and setting each time it is determined that the adaptive filter coefficient of the subband employing the high-speed RLS algorithm has converged, thereby adapting to a changing situation. Optimum settings can be made, and as a result, the performance of the acoustic echo canceller can be improved by effectively using the limited amount of calculation.

As described above, according to the fifth embodiment, by using the sub-band error signal evaluation means 91, an adaptive algorithm is selected and a tap length is calculated adaptively, and these are set. Therefore, the performance of the acoustic echo canceller can be easily improved by effectively using the limited amount of calculation.

As described above, taking an acoustic echo canceller as an example,
Although the method and apparatus for identifying an unknown system using a subband adaptive filter according to the first to fifth embodiments of the present invention have been described, an acoustic echo canceller, a howling canceler, And an apparatus represented by an adaptive equalizer or the like.

[0058]

The present invention is configured as described above, and in particular, selects various adaptive algorithms for updating the filter coefficients of the subband adaptive filter for each subband.
By calculating the tap length and supplying it to each sub-band, the limited computation amount can be effectively used, and the identification performance of an unknown system such as an acoustic echo canceller can be easily improved. .

The present invention is configured as described above, and particularly evaluates a plurality of sub-band target signals, sub-band reference signals or sub-band error signals, and based on the evaluation result, determines the filter coefficients of the sub-band adaptive filter. Various adaptive algorithms to be used for updating of the data are selected, the tap length is calculated and supplied to each subband, so that a limited amount of computation is effectively used, and an unknown system such as an acoustic echo canceller is used. Can be easily improved.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a method and apparatus for identifying an unknown system using a subband adaptive filter according to Embodiment 1 of the present invention;

FIG. 2 is an explanatory diagram showing a method and apparatus for identifying an unknown system using a subband adaptive filter according to Embodiment 2 of the present invention;

FIG. 3 is an explanatory diagram showing a method and an apparatus for identifying an unknown system using a subband adaptive filter according to Embodiment 3 of the present invention;

FIG. 4 is an explanatory diagram showing a method and an apparatus for identifying an unknown system using a subband adaptive filter according to Embodiment 4 of the present invention;

FIG. 5 is an explanatory diagram showing a method and an apparatus for identifying an unknown system using a subband adaptive filter according to Embodiment 5 of the present invention;

FIG. 6 is an explanatory diagram of an acoustic echo canceller using a conventional subband adaptive filter,

FIG. 7 is a block diagram showing a configuration of a subband adaptive filter unit.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 reception signal input terminal 2 D / A converter 3, 7 amplifier 4 speaker 5 acoustic echo 6 microphone 8 A / D converter 9 transmission signal output terminal 11, 12 subband division processing unit 13 subband synthesis processing unit 20 subband Adaptive filter group 21, 22, 23 Sub-band adaptive filter unit 31, 32, 33 Adder 51 Control unit 52 Adaptive algorithm selection unit and tap length calculation unit 61 Selection calculation pattern storage unit 71 Sub-band target signal evaluation unit 81 Sub-band reference Signal evaluation means 91 Subband error signal evaluation means

Claims (16)

[Claims] 1. An unknown system input signal is subjected to sub-band division processing to generate a plurality of sub-band reference signals, and the plurality of sub-band reference signals are input to a plurality of independent sub-band adaptive filters. Sub-band division processing to generate a plurality of sub-band target signals, and output a difference between the plurality of sub-band target signals and an output signal of the sub-band adaptive filter as a sub-band error signal; An identification method of an unknown system including a step of updating a filter coefficient of the subband adaptive filter using a band error signal, wherein various adaptive algorithms used for updating a filter coefficient of the subband adaptive filter are applied to each subband. The tap length of each sub-band is calculated, and the selection result of the adaptive algorithm and the Method of identifying an unknown system using sub-band adaptive filter, characterized in that by converting the results of up length calculating a control signal for the sub-band adaptive filter group consisting of the step of supplying to the respective sub-band adaptive filters. 2. An unknown system, wherein a plurality of subband reference signals are generated by subjecting an input signal of an unknown system to subband division processing, and the plurality of subband reference signals are input to a plurality of independent subband adaptive filters. Sub-band division processing to generate a plurality of sub-band target signals, and output a difference between the plurality of sub-band target signals and an output signal of the sub-band adaptive filter as a sub-band error signal; An identification method for an unknown system including a step of updating a filter coefficient of the sub-band adaptive filter using a band error signal, wherein an adaptive algorithm and a tap length of a plurality of patterns are registered in advance,
Selecting the various adaptive algorithms used for updating the filter coefficients of the subband adaptive filter for each subband from the registered adaptive algorithms and tap lengths of the plurality of patterns, calculating the tap length, and selecting the adaptive algorithm A step of converting a result and a result of the tap length calculation into a control signal for a subband adaptive filter group and supplying the control signal to each subband adaptive filter. . 3. An unknown system, wherein a plurality of subband reference signals are generated by subjecting an input signal of an unknown system to subband division processing, and the plurality of subband reference signals are input to a plurality of independent subband adaptive filters. Sub-band division processing to generate a plurality of sub-band target signals, and output a difference between the plurality of sub-band target signals and an output signal of the sub-band adaptive filter as a sub-band error signal; An identification method of an unknown system including a step of updating a filter coefficient of the sub-band adaptive filter using a band error signal, wherein the plurality of sub-band target signals are evaluated, and based on a result of the evaluation, Various adaptive algorithms used for updating the filter coefficients of the sub-band adaptive filter are selected for each sub-band, A step of calculating a tap length, converting the selection result of the adaptive algorithm and the result of the tap length calculation into a control signal for a subband adaptive filter group, and supplying the control signal to each subband adaptive filter. Identification method of unknown system using band adaptive filter. 4. The method according to claim 3, further comprising the step of evaluating a plurality of subband reference signals, wherein said subband adaptive filter is based on a result of said evaluation. Select various adaptive algorithms used for updating the filter coefficient of each subband, calculate the tap length of each subband, and select the adaptive algorithm selection result and the tap length calculation result as a subband adaptive filter group. 4. The method for identifying an unknown system using a sub-band adaptive filter according to claim 3, comprising the steps of: 5. The method according to claim 3, further comprising the step of evaluating a plurality of sub-band error signals, wherein the step of evaluating the plurality of sub-band error signals comprises the step of evaluating the plurality of sub-band error signals. Select various adaptive algorithms used for updating the filter coefficient of each subband, calculate the tap length of each subband, and select the adaptive algorithm selection result and the tap length calculation result as a subband adaptive filter group. 4. The method for identifying an unknown system using a sub-band adaptive filter according to claim 3, comprising the steps of: 6. A sub-band division processing unit for sub-band dividing an input signal of an unknown system to generate a plurality of sub-band reference signals, and a plurality of sub-bands for inputting and processing the generated plurality of sub-band reference signals. An independent subband adaptive filter, a plurality of second subband division processing units for performing subband division processing on the output signal of the unknown system to generate a plurality of subband target signals, and the plurality of subband target signals. And an adding unit that outputs a difference between the output signal of the sub-band adaptive filter and the output signal as a sub-band error signal. Selecting means for selecting for each sub-band, tap length calculating means for calculating the tap length of each sub-band, Control means for converting a selection result of the adaptive algorithm and a result of the tap length calculation into a control signal for a subband adaptive filter group and supplying the control signal to each subband adaptive filter, and updating the filter coefficient of the subband adaptive filter. An apparatus for identifying an unknown system using a subband adaptive filter, wherein selection of an adaptive algorithm to be used and calculation of a tap length are performed for each subband. 7. An adaptive algorithm and tap length of a plurality of patterns registered by an adaptive algorithm selecting means and a tap length calculating means, comprising a selection calculation pattern accumulator for pre-registering a plurality of adaptive algorithms and tap lengths. 7. The sub-band adaptive filter according to claim 6, wherein various adaptive algorithms used for updating the filter coefficients of the sub-band adaptive filter are selected for each sub-band and a tap length is calculated. An unknown system identification device used. 8. A sub-band division processing section for sub-band dividing an input signal of an unknown system to generate a plurality of sub-band reference signals, and a plurality of sub-bands for inputting and processing the generated plurality of sub-band reference signals. An independent subband adaptive filter, a plurality of second subband division processing units for performing subband division processing on the output signal of the unknown system to generate a plurality of subband target signals, and the plurality of subband target signals. An adder for outputting a difference from an output signal of the sub-band adaptive filter as a sub-band error signal, the apparatus for identifying an unknown system, comprising: a sub-band target signal evaluator for evaluating the plurality of sub-band target signals. And various adaptive algorithms used for updating the filter coefficients of the subband adaptive filter based on the results of the evaluation. Selection means for selecting the tap length, tap length calculation means for calculating the tap length of each subband, and converting the selection result of the adaptive algorithm and the result of the tap length calculation into a control signal for a subband adaptive filter group. Control means for supplying to each sub-band adaptive filter, and adaptively selecting an adaptive algorithm and calculating a tap length used for updating the filter coefficient of the sub-band adaptive filter for each sub-band. An apparatus for identifying an unknown system using a subband adaptive filter. 9. A subband reference signal estimating means for evaluating a plurality of subband reference signals, instead of the subband target signal estimating means for evaluating a plurality of subband target signals according to claim 8, The method according to claim 1, wherein various adaptive algorithms used for updating the filter coefficients of the subband adaptive filter are selected for each subband based on a result, and a tap length of each subband is calculated. 9. An apparatus for identifying an unknown system using the subband adaptive filter according to 8. 10. A subband error signal evaluation means for evaluating a plurality of subband error signals, instead of the subband target signal evaluation means for evaluating a plurality of subband target signals according to claim 8, The method according to claim 1, wherein various adaptive algorithms used for updating the filter coefficients of the subband adaptive filter are selected for each subband based on a result, and a tap length of each subband is calculated. 9. An apparatus for identifying an unknown system using the subband adaptive filter according to 8. 11. The method according to claim 1, wherein each of the evaluating steps is performed based on two of the input signals.
6. The method for identifying an unknown system using a subband adaptive filter according to claim 3, wherein the evaluation is performed using a power value. 12. The identification of an unknown system using a sub-band adaptive filter according to claim 3, wherein each of said evaluating steps is evaluated using an absolute value of an input signal. Method. 13. The identification of an unknown system using a sub-band adaptive filter according to claim 8, wherein each of said evaluation means is evaluated using a square value of an input signal. apparatus. 14. An apparatus for identifying an unknown system using a sub-band adaptive filter according to claim 8, wherein each of said evaluation means evaluates using an absolute value of an input signal. . 15. An apparatus according to claim 1, wherein an adaptive algorithm for updating a filter coefficient of said subband adaptive filter is selected from a learning identification method and a fast RLS algorithm. Identification method of unknown system using subband adaptive filter. 16. The method according to claim 6, wherein an adaptive algorithm for updating the filter coefficient of said subband adaptive filter is selected from a learning identification method and a fast RLS algorithm. An unknown system identification device using a subband adaptive filter.