JP2003143042A - Echo canceller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a echo canceller, capable of removing echoes of both of a periodic signal and an audio signal at a low cost. SOLUTION: This echo canceller comprises a first means 6 for computing an attenuation amount of the echo signal by each constant time interval, a second means 9 for tracking and holding the maximum value of the computed attenuation amount, a third means 10 for decreasing at a fixed ratio the maximum value of the attenuation amount output from the second means by each of the constant time intervals, when the value of the maximum value of the attenuation amount held in the second means subtracted by the current value of the attenuation amount of the echo signal exceeds a first threshold and holding the obtained values, and a fourth means 11 for computing the difference between the maximum value of the attenuation amount held in the second means and the values held in the third means by each of the fixed time intervals. When the difference exceeds a second threshold, both the maximum value of the attenuation amount, held in the second means and the values held in the third means, are reset to the current value of the attenuation amount of the echo signal, and filter coefficient updating operation for an adaptive filter is started.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an echo canceller used in a telephone system or the like for removing an echo signal generated by impedance mismatch of a communication line.

[0002]

2. Description of the Related Art When a periodic signal for call control (for example, a ringing signal RBT) is input to an echo canceller, a pseudo echo signal of the periodic signal is generated and an adaptive filter of an adaptive filter is used to cancel the echo of the periodic signal. When the filter coefficient is updated, the echo filter is not immediately removed because the adaptive filter needs to update the filter coefficient again the next time a voice signal is input, which causes a problem that the call quality deteriorates. is there.

In order to deal with this problem, it is determined whether the signal input to the echo canceller is a periodic signal or a voice signal,
For example, for a periodic signal, the coefficient update of the adaptive filter of the echo canceller is stopped, and for a voice signal, the coefficient update of the adaptive filter of the echo canceller is performed.
It is disclosed in Japanese Patent Publication No. 1-024778.

The operation of the echo canceller disclosed in this publication will be briefly described with reference to FIG. Figure 12
An example of using an echo canceller for an Internet telephone (Voip) is shown. Here, the echo canceller 101 on the near-end talker side will be described. When the near-end talker A calls the far-end talker B, first, the call signal RB
T is sent to far-end speaker B.

This call signal RBT is a gateway 103 between the echo canceller 101 on the near-end talker side and the Internet line, or a gateway (not shown) on the far-end talker side or a PBX (not shown) on the far-end talker side. Occurs. This calling signal is also sent to the near-end speaker A, who can hear a ringing sound such as "pururu".

At this time, when the far-end talker B does not answer the telephone due to absence or the like, the near-end talker A gives up the call and hangs down the receiver. At this time, generally, the near-end talker side PBX 10
6 detects this and outputs a busy signal BT. The busy signal BT passes through the echo canceller 101 and is input to the gateway 103. When the gateway 103 detects the busy signal BT, it is considered that the near-end talker A has abandoned the establishment of the line, and the line is released.

[0007]

However, as described above, since the echo canceller 101 stops updating the filter coefficient when the periodic signal is input, it does not have the ability to cancel the echo of the periodic signal. Therefore, the echo of the call signal RBT sent from the gateway 103 to the near-end talker side when the near-end talker A finishes dialing is not removed by the echo canceller 101, and is directly input to the transmission-side input terminal of the gateway 103. enter. After that, when the near-end speaker A gives up the call and puts the handset,
For example, the busy signal BT generated by the PBX 106 enters the transmission side input terminal of the gateway via the hybrid transformer 104 and the echo canceller 101. Therefore, at this point, two types of signals, the echo signal of the calling signal RBT and the busy signal BT, are superimposed and arrive at the transmission side input terminal of the gateway 103.

In many systems, the busy signal BT and the call signal RBT have the same frequency. For example, in Japan,
The busy signal BT and the call signal RBT differ in the intermittent period of the signals, but both are periodic signals of 400 Hz. Also, the maximum amplitudes of the signals are almost equal. In such a case, the gateway 103 cannot find the busy signal BT from the mixed signals, and cannot open the line, which causes a problem that the line cannot be used for new communication.

On the other hand, in order to deal with this problem, if the filter coefficient is updated even when the periodic signal is input, another problem as described below will occur.

That is, in the echo canceller 101, the state of an echo path learned by a periodic signal (transmission path waveform) and the state of an echo path learned by a signal having a certain frequency band such as a voice signal are different. To be observed. When giving priority to learning when exchanging periodic signals in the initial stage of line connection, the echo canceller 101 well learns the echo path component of the frequency component (for example, 400 Hz) of the periodic signal, but it is completely unlearned for other frequency components. Becomes For example, in response to a ringing signal RBT signal, when the far-end speaker picks up the handset, the speech signal starts next, but the speech signal is 3 on the telephone line.
The signal has a frequency spread of about 40 Hz to 4000 Hz. At this time, for the echo canceller 101, the state of the echo path suddenly changes. Especially for the unlearned frequency components of the voice signal, learning time is required until the echo can be sufficiently removed by using any estimation algorithm, and the call quality deteriorates. To do.

This problem is exacerbated because most echo cancellers have a simple double-talk detector implemented. Double talk means a state in which the voice signal of the far-end speaker and the voice signal of the near-end speaker are present at the same time, and in this state, it is usually difficult to distinguish the echo signal from the voice signal to be transmitted. Yes Stop updating adaptive filter coefficients. For example, after the period for canceling the echo of the periodic signal ends, the echo canceller 101 enters the period for canceling the echo of the voice signal of the far-end speaker, but as described above, the echo canceller 101 cancels the voice signal echo. Since the waveform of the correct echo path for learning is not learned, the echo of the voice signal of the far-end speaker cannot be removed.
As a result, the level of the echo signal observed at the output terminal Sout on the transmission side becomes high.
Level of audio signal entering in and output terminal Sout of transmission side
In the case of a normal echo canceller that detects the double talk by comparing the level of the audio signal output from the normal echo canceller, there are many cases in which the adaptive filter coefficient update is stopped due to the erroneous determination of the double talk state. At this time, the echo canceller continuously stops updating the coefficient of the adaptive filter,
The speaker is forced to make a bad call with many echoes.

As described above, in the above-described conventional echo canceller, if the update of the filter coefficient is stopped when the periodic signal is input, when the echo of the calling signal and the busy signal are mixed, Since the medium signal cannot be detected, the line cannot be opened. On the other hand, if echo elimination of the periodic signal is prioritized, there is a problem that an important echo feeling during conversation is left.

In addition to the above, the conventional echo canceller described above requires complicated control of the echo canceller in order to remove the echo when the call control signal (periodic signal) and the voice signal are continuous. Alternatively, the scale of software is large, and a complicated signal detector is required to discriminate a periodic signal from a voice signal, so that there is a problem that the manufacturing cost is high.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an echo canceller capable of removing echoes of both a periodic signal and a voice signal at low cost.

[0015]

[Means for Solving the Problems] In order to solve the above problems,
In order to prevent the echo signal of the received signal from returning to the transmission side, the invention according to claim 1 has an adaptive filter which is added to the echo signal to generate a pseudo echo signal for attenuating the echo signal. In the canceller, first means for calculating the attenuation amount of the echo signal from the power of the received signal and the power of the echo signal to which the pseudo echo signal is added are calculated at fixed time intervals; and the first means. Second means for tracking and holding the maximum value of the attenuation amount, and a value obtained by subtracting the current value of the attenuation amount of the echo signal from the maximum value of the attenuation amount held by the second means exceeds a first threshold value. The maximum value of the attenuation amount output from the second means is decreased at a constant rate at the constant time intervals,
Third means for holding the value and fourth means for calculating a deviation width between the maximum value of the attenuation amount held by the second means and the value held by the third means at the constant time interval. Both the maximum value of the attenuation amount held by the second means and the value held by the third means when the deviation width calculated by the fourth means exceeds a second threshold value. Is reset to the current value of the attenuation amount of the echo signal, and the filter coefficient updating operation of the adaptive filter is started.

According to a second aspect of the present invention, in the first aspect of the invention, there is provided a fifth means for detecting whether or not the maximum value of the attenuation amount held by the second means is updated.
When the fifth means outputs that the maximum value of the attenuation amount held by the second means is updated, the filter coefficient updating operation of the adaptive filter is started, and the attenuation held by the second means is started. It is characterized in that the filter coefficient updating operation of the adaptive filter is stopped when the fifth means detects that the maximum value of the quantity has not been updated for a certain period.

The invention according to claim 3 is the invention according to claim 2, further comprising a sixth means for detecting whether or not the double talk state is present, and the double talk state is detected by the sixth means. The filter coefficient updating operation of the adaptive filter is stopped when this occurs, and the filter coefficient updating operation of the adaptive filter is started when the sixth means stops detecting the double-talk state.

According to a fourth aspect of the present invention, in the invention according to the third aspect, the start and stop of the filter coefficient updating operation of the adaptive filter is controlled by the output of the fourth means>
The output of the fifth means> the output of the sixth means is performed in the order of priority.

The invention described in claim 5 is the invention according to claims 1 to 4.
In the invention as described in any one of 1 above, the first means keeps the power of the input signal constant for each of the echo signal to which the received signal and the pseudo echo signal added to the first means are added. A power calculation means for calculating at each time interval, and holding a maximum value of the calculated power, and when the held maximum value is not updated, the held maximum value is kept at a constant ratio for every fixed time interval. Maximum value tracking / leak means for reducing the maximum value tracking /
It is characterized in that the attenuation amount of the echo signal is calculated based on the maximum value output by the leak means.

In order to solve the above-mentioned problems, the invention according to claim 6 is a pseudo-attenuator that adds an echo signal of a received signal to the echo signal and attenuates the echo signal in order to prevent the echo signal from returning to the transmission side. In an echo canceller having an adaptive filter for generating an echo signal, first calculating the attenuation amount of the echo signal from the power of the received signal and the power of the echo signal to which the pseudo echo signal is added
Means for tracking and holding the maximum value of the attenuation amount calculated by the first means, and the second means for holding the maximum value of the attenuation amount, and the maximum value of the attenuation amount held by the second means When the value obtained by subtracting the current value exceeds a predetermined threshold value, the maximum value of the attenuation amount output from the second means is decreased at a constant rate at the constant time interval and the value is held. The third means and the fourth means for measuring the length of time that has elapsed since the maximum value of the attenuation amount held by the second means and the value held by the third means started to deviate from each other. When the time measured by the fourth means reaches a predetermined value, both the maximum value of the attenuation amount held by the second means and the value held by the third means are converted into echo signals. While resetting the current attenuation value, update the filter coefficient of the adaptive filter. Characterized in that it started.

The invention according to claim 7 is the invention according to claim 6, further comprising: fifth means for detecting whether or not the maximum value of the attenuation amount held by the second means is updated.
When the fifth means outputs that the maximum value of the attenuation amount held by the second means is updated, the filter coefficient updating operation of the adaptive filter is started, and the attenuation held by the second means is started. It is characterized in that the filter coefficient updating operation of the adaptive filter is stopped when the fifth means detects that the maximum value of the quantity has not been updated for a certain period.

The invention described in claim 8 is the same as the invention described in claim 7, further comprising a sixth means for detecting whether or not the double talk state is present, and the double talk state is detected by the sixth means. The filter coefficient updating operation of the adaptive filter is stopped when this occurs, and the filter coefficient updating operation of the adaptive filter is started when the sixth means stops detecting the double-talk state.

According to a ninth aspect of the invention, in the eighth aspect of the invention, the control of the start and stop of the filter coefficient updating operation of the adaptive filter is performed by the output of the fourth means>
The output of the fifth means> the output of the sixth means is performed in the order of priority.

According to a tenth aspect of the invention, in the invention according to any one of the sixth to ninth aspects, the first means is a reception signal and a pseudo echo signal input to the first means. Power calculating means for calculating the power of the input signal for each constant time interval for each of the added echo signals of, and holding the maximum value of the calculated power, and when the held maximum value is not updated. , Maximum value tracking / leak means for reducing the held maximum value at a constant rate at the constant time interval,
It is characterized in that the attenuation amount of the echo signal is calculated based on the maximum value output by the leak means.

In order to solve the above-mentioned problems, the invention according to claim 11 is a pseudo signal which is added to an echo signal of a received signal to attenuate the echo signal in order to prevent the echo signal of the received signal from returning to the transmission side. In an echo canceller having an adaptive filter for generating an echo signal, first means for calculating the attenuation amount of the echo signal from the power of the received signal and the power of the echo signal to which the pseudo echo signal is added, at constant time intervals, Second means for tracking and holding the maximum value of the attenuation amount calculated by the first means, and subtracting the present value of the attenuation amount of the echo signal from the maximum value of the attenuation amount held by the second means. Third means for reducing the maximum value of the attenuation amount output from the second means at a constant rate at the constant time interval and holding the value when the value exceeds the first threshold value. And the above The difference between the maximum value of the attenuation amount held by the second means and the value held by the third means is calculated at each of the constant time intervals, and the maximum value of the attenuation amount held by the second means is calculated. And a fourth means for measuring the length of time that has elapsed since the value held by the third means began to deviate, and whether the deviation width calculated by the fourth means exceeds a second threshold value. Alternatively, when the time measured by the fourth means exceeds a predetermined value, both the maximum value of the attenuation amount held by the second means and the value held by the third means are attenuated in the echo signal. It is characterized in that the filter coefficient updating operation of the adaptive filter is started while resetting the current value of the quantity.

According to a twelfth aspect of the present invention, in the eleventh aspect of the present invention, there is provided a fifth means for detecting whether or not the maximum value of the attenuation amount held by the second means is updated. When the fifth means outputs that the maximum value of the attenuation amount held by the second means is updated, the filter coefficient updating operation of the adaptive filter is started, and the attenuation held by the second means is started. It is characterized in that the filter coefficient updating operation of the adaptive filter is stopped when the fifth means detects that the maximum value of the quantity has not been updated for a certain period.

The thirteenth aspect of the present invention is the invention according to the twelfth aspect, further comprising sixth means for detecting whether or not the double talk state is present.
The filter coefficient updating operation of the adaptive filter is stopped when detected by the means, and the filter coefficient updating operation of the adaptive filter is started when the sixth means stops detecting the double talk state. And

According to a fourteenth aspect of the present invention, in the invention according to the thirteenth aspect, the start and stop of the filter coefficient updating operation of the adaptive filter is controlled by the output of the fourth means> the fifth means. Output> the output of the sixth means is performed in the order of priority.

The invention described in claim 15 is the same as the invention described in any one of claims 11 to 14,
Means for calculating the power of the input signal for each of the echo signals to which the received signal and the pseudo echo signal added to the first means are added, at a constant time interval; A maximum value tracking / leak means for holding the maximum value of the power and reducing the held maximum value at a constant rate at the constant time interval when the retained maximum value is not updated; It is characterized in that the attenuation amount of the echo signal is calculated based on the maximum value output from the maximum value tracking / leakage means.

In order to solve the above-mentioned problems, the invention as set forth in claim 16 is a pseudo signal which is added to an echo signal of a received signal to eliminate the echo signal in order to prevent the echo signal of the received signal from returning to the transmission side. In an echo canceller having an adaptive filter for generating an echo signal, a first means for calculating the amount of cancellation of the echo signal at constant time intervals from the power of the echo signal and the power of the echo signal to which the pseudo echo signal is added, A second means for tracking and holding the maximum value of the erasing amount calculated by the first means, and a current value of the erasing amount of the echo signal from the maximum value of the erasing amount held by the second means. When the subtracted value exceeds the first threshold value, the maximum value of the erase amount output from the second means is reduced at a constant rate at the constant time intervals, and the value is held. And the means of The fourth means calculates the deviation width between the maximum value of the erase amount held by the second means and the value held by the third means at the constant time interval, and the fourth means calculates When the deviation width exceeds the second threshold value, both the maximum value of the erasing amount output from the second means and the value held by the third means are reset to the current value of the erasing amount of the echo signal. At the same time, the filter coefficient updating operation of the adaptive filter is started.

The invention according to claim 17 is the invention according to claim 16, further comprising a fifth means for detecting whether or not the maximum value of the erase amount held by the second means is updated. When the fifth means outputs that the maximum value of the erasure amount held by the second means is updated, the filter coefficient updating operation of the adaptive filter is started, and the erasure held by the second means is started. It is characterized in that the filter coefficient updating operation of the adaptive filter is stopped when the fifth means detects that the maximum value of the quantity has not been updated for a certain period.

The invention according to claim 18 is the invention according to claim 17, further comprising a sixth means for detecting whether or not the state is the double talk state, and the double talk state is the sixth state.
The filter coefficient updating operation of the adaptive filter is stopped when detected by the means, and the filter coefficient updating operation of the adaptive filter is started when the sixth means stops detecting the double talk state. And

According to a nineteenth aspect of the present invention, in the invention according to the eighteenth aspect, the start and stop of the filter coefficient updating operation of the adaptive filter is controlled by the output of the fourth means> the fifth means. Output> the output of the sixth means is performed in the order of priority.

In order to solve the above-mentioned problems, the invention as set forth in claim 20, in order to prevent the echo signal of the received signal from returning to the transmission side, it is added to the echo signal to eliminate the echo signal. In an echo canceller having an adaptive filter for generating an echo signal, a first means for calculating the amount of cancellation of the echo signal at constant time intervals from the power of the echo signal and the power of the echo signal to which the pseudo echo signal is added, A second means for tracking and holding the maximum value of the erasing amount calculated by the first means, and a current value of the erasing amount of the echo signal from the maximum value of the erasing amount held by the second means. When the subtracted value exceeds a predetermined threshold value, the maximum value of the erase amount output from the second means is decreased at a constant rate at the constant time intervals, and the third value is held. Means and And a fourth means for measuring the length of time elapsed from the serial and the value held in the maximum value and the third means of cancellation amount held by the second means starting to divergence,
When the time measured by the fourth means reaches a predetermined value, both the maximum value of the erase amount held by the second means and the value held by the third means are set as the erase amount of the echo signal. Is reset to the present value, and the filter coefficient updating operation of the adaptive filter is started.

According to a twenty-first aspect of the invention, in the twenty-first aspect of the invention, there is provided a fifth means for detecting whether or not the maximum value of the erase amount held by the second means has been updated. When the fifth means outputs that the maximum value of the erasure amount held by the second means is updated, the filter coefficient updating operation of the adaptive filter is started, and the erasure held by the second means is started. It is characterized in that the filter coefficient updating operation of the adaptive filter is stopped when the fifth means detects that the maximum value of the quantity has not been updated for a certain period.

The invention according to claim 22 is the invention according to claim 20, further comprising a sixth means for detecting whether or not the state is the double talk state, and the double talk state is the sixth state.
The filter coefficient updating operation of the adaptive filter is stopped when detected by the means, and the filter coefficient updating operation of the adaptive filter is started when the sixth means stops detecting the double talk state. And

According to a twenty-third aspect of the invention, in the twenty-third aspect of the invention, the control of the start and stop of the filter coefficient updating operation of the adaptive filter is performed by the output of the fourth means> the fifth means. Output> the output of the sixth means is performed in the order of priority.

In order to solve the above-mentioned problems, the invention as set forth in claim 24, in order to prevent the echo signal of the received signal from returning to the transmitting side, is added to the echo signal and erases the echo signal. In an echo canceller having an adaptive filter for generating an echo signal, a first means for calculating the amount of cancellation of the echo signal at constant time intervals from the power of the echo signal and the power of the echo signal added with the pseudo echo signal, Second means for tracking and holding the maximum value of the erasing amount calculated by the first means, and subtracting the current value of the erasing amount of the echo signal from the maximum value of the erasing amount held by the second means. When the value exceeds the first threshold, the second
The maximum value of the erasing amount output from the means is reduced by a constant ratio at the constant time interval, and the third means holds the value, and the maximum value of the erasing amount held by the second means. The deviation width of the value held by the third means is calculated for each of the constant time intervals, and the maximum value of the erase amount held by the second means and the value held by the third means are deviated. A fourth means for measuring the length of time that has elapsed since the start of the operation, and the deviation width calculated by the fourth means exceeds a second threshold value or the time measured by the fourth means is predetermined. Is exceeded, both the maximum value of the amount of cancellation held by the second means and the value held by the third means are reset to the current value of the attenuation amount of the echo signal, and the adaptive filter The filter coefficient updating operation is started.

A twenty-fifth aspect of the invention is the invention according to the twenty-fourth aspect, further comprising fifth means for detecting whether or not the maximum value of the erase amount held by the second means is updated. When the fifth means outputs that the maximum value of the erasure amount held by the second means is updated, the filter coefficient updating operation of the adaptive filter is started, and the erasure held by the second means is started. It is characterized in that the filter coefficient updating operation of the adaptive filter is stopped when the fifth means detects that the maximum value of the quantity has not been updated for a certain period.

According to a twenty-sixth aspect of the present invention, in the twenty-fifth aspect of the present invention, there is provided a sixth means for detecting whether or not the double-talk state is present.
The filter coefficient updating operation of the adaptive filter is stopped when detected by the means, and the filter coefficient updating operation of the adaptive filter is started when the sixth means stops detecting the double talk state. And

According to a twenty-seventh aspect of the present invention, in the invention according to the twenty-sixth aspect, the start and stop of the filter coefficient updating operation of the adaptive filter is controlled by the output of the fourth means> the fifth means. Output> the output of the sixth means is performed in the order of priority.

[0042]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment FIG. 1 is a block diagram showing a configuration of an echo canceller according to a first embodiment of the present invention, in which Rin is a receiving side input terminal (hereinafter, referred to as Rin terminal). , Rout is a receiving side output terminal (hereinafter, referred to as Rout terminal), Sin is a transmitting side input terminal (hereinafter, referred to as Sin terminal), Sout
Is a transmission-side output terminal (hereinafter referred to as Sout terminal), 5 and 7 are power calculators, 6 is an echo attenuation calculator, 9 is a maximum value tracker, 8 is a maximum value update determination device, 10 is a maximum value leak calculator, Reference numeral 11 is a deviation width determiner, 12 is a double talk detector, and 13 is an adaptive filter coefficient update control circuit. The operation of this echo canceller will be described below. here,
First, it is assumed that a call signal RBT (hereinafter, referred to as an RBT signal) which is a periodic signal is input to the reception side input terminal Rin.

R entering the echo canceller from the Rin terminal
The BT signal is input to the power calculators 5 and 7, the double talk detector 12, and the adaptive filter 15. At this time, no signal is input to the Sin terminal. The power calculator 7 calculates the level of the signal input from the Rin terminal, and outputs the calculation result to the echo attenuation amount calculator 6. The signal input from the Rin terminal is also input to the double talk detector 12,
Since there is no signal input to the Sin terminal, the double talk detector 12 does not output any signal.

The adaptive filter 15 uses a well-known algorithm such as the "learning identification method" to generate an opposite signal (pseudo echo) y'of the echo y which will eventually arrive at the Sin terminal. The echo y arriving at the Sin terminal is added to the pseudo echo y ′ by the adder 14 and cancelled. The signal output from the adder 14 (referred to as the Res signal) is the double-talk detector 12,
It is output to the adaptive filter 15 and the power calculator 5.

The double talk detector 12 compares the level of the signal input from the Rin terminal (hereinafter referred to as the Rin signal) with the level of the Res signal output from the adder 14, and, for example, Res signal level × 2> If it is at the Rin signal level, it is determined to be in the double talk state. When the double talk detector 12 detects the double talk state, the adaptive filter coefficient update control circuit 13 stops the coefficient update of the adaptive filter 15. To detect the double-talk state of the double-talk detector 12, any known method other than the above-mentioned signal level comparison can be used.

On the other hand, the power calculator 5 calculates the level of the Res signal and outputs it to the echo attenuation amount calculator 6. Also,
The power calculator 7 calculates the level of the Rin signal and outputs it to the echo attenuation amount calculator 6. Each of the power calculators 5 and 7 calculates the level x of the input signal from the following formula, for example.

X (k) = x (k−1) × (1−δ) + | x (k) | × δ1 (1) where k is sample number 1, 2, 3, ..., N, x (0) is 0. δ1 is a smoothing constant (0 <δ1 <1), and in this embodiment, δ1 = 2 ⁻⁷ . When the value of δ1 is increased, the rough change of the signal can be well represented, while when it is decreased, the change of the signal level becomes sensitive.

The echo attenuation amount calculator 6 is a power calculator 5,
Echo attenuation is calculated from the levels of the two signals from 7. Specifically, the level of the Rin signal is L_rin (k), Res
When the signal level is L_res (k), the echo attenuation amount iaco
Calculate m (k) according to the following formula.

Iacom (k) = 20 × LOG ₁₀ (L_rin (k)) / L_res (k)) (2) The calculation of the equation (2) is executed when a signal is input to the Rin terminal. Whether or not a signal is input to the Rin terminal can be determined by using a known means such as a level measuring circuit.

The echo attenuation amount iacom (k) is input to the maximum value tracer 9, and the maximum value tracer 9 outputs the maximum value if iacom (k) is the maximum among the echo attenuation amounts calculated up to that point. The value tracking variable imax_iacom (k) is set to imax_iacom (k) = iacom (k)… (3), otherwise imax_iacom (k) = imax_iacom (k-1)… (4) and the previous value is retained. . However, iacom (0) = 0.

The maximum value tracker 9 is a maximum value tracking variable imax_iac.
om (k) maximum value update judgment device 8 and maximum value leak calculator 10
And output to. The operation of the maximum value leak calculator 10 will be described later. The maximum value update determiner 8 is imax_iacom (k-1)
When imax_iacom (k) is compared with imax_iacom (k) and imax_iacom (k-1) <imax_iacom (k) (5), the coefficient update signal adp (k) is output to the adaptive filter coefficient update control circuit 13 to perform the coefficient update operation. Let it run. On the other hand, when imax_iacom (k-1) ≥ imax_iacom (k) (6), the maximum value update determination unit 8 determines that the maximum value has not risen, and the maximum value non-increasing counter imax_iacom_
Increase the counter value of sgc_comp_counter by 1. Then, while imax_iacom_sgc_comp_counter <K (7), the coefficient update signal adp (k) is output to the adaptive filter coefficient update control circuit 13 to execute the coefficient update operation. When imax_iacom_sgc_comp_counter ≧ K (8), the coefficient update signal not_adp (k) is output to the adaptive filter coefficient update control circuit 13 to stop the coefficient update operation. In this embodiment, K = 8000, but the present invention is not limited to this.

Next, the operation of the maximum leak calculator 10 will be described. The maximum leak calculator 10 calculates the maximum leak variable imax_iacom_sgc_save (k) according to the following formula when iacom (k) <imax_iacom (k) -α ... (9). Here, α is a constant, which is 10 dB in the present embodiment, but is not limited to this.

Imax_iacom_sgc_save (k) = imax_iacom_sgc_save (k-1) × δ2 (10) However, imax_iacom_sgc_save (0) = 0, and (9)
If the expression is not satisfied, the operation of the expression (10) is not executed. (That is, hold imax_iacom_sgc_save (k) at the previous value). In the present embodiment, Δ2 = 0.99, but the present invention is not limited to this.

The divergence width determiner 11 includes a maximum value tracking variable im
The ax_iacom (k) is supplied from the maximum value tracker 9, and the maximum value leak variable imax_iacom_sgc_save (k) is supplied from the maximum value leak calculator 10. When the difference width imax_iacom_sgc_save (k) × δ3 <imax_iacom (k), the deviation width determiner 11 outputs the coefficient update signal adp to the adaptive filter coefficient update control circuit 13 to start updating the coefficient of the adaptive filter 15. In this embodiment, δ3 = 2.0 times (6d in dB display
B), but is not limited to this. still,
A2 (dB) = 20 × LOG _1O A1 between the magnification A1 and dB display A2
There is a (double) relationship.

At this time, the maximum value tracking device 9 has a maximum value tracking variable imax_iacom (k) and a maximum value leak variable imax_iaco.
m_sgc_save (k) is reset to the echo attenuation amount iacom (k) at that time according to the following formula.

Imax_iacom_sgc-save (k) = imax_iacom (k) = iacom (k) (11) A coefficient update signal is input from any of the maximum value update determiner 8, the double talk detector 12, and the deviation width determiner 11. Then, the adaptive filter coefficient update control circuit 13 causes the adaptive filter 15
The coefficient update is started or stopped, but the priority is in the order of deviation width determiner 11> maximum value update determiner 8> double talk detector 12. That is, the instruction to start or stop the coefficient update from the deviation width determiner 11 has the highest priority, and then the instruction to start or stop the coefficient update from the maximum value update determiner 8 has the highest priority.

Next, in the echo canceller having the above configuration, the echo attenuation amount iacom (k) and the maximum value tracking variable imax_iacom
(k), an example of a temporal change of the maximum leak variable imax_iacom_sgc_save (k) will be described with reference to FIG. In FIG. 2, the RBT signal is first input to the Rin terminal, and then the echo attenuation amount iacom (k), the maximum value tracking variable imax_iacom (k), the coefficient update signal adp, and the maximum value leak when the voice signal is input. Variable im
It shows how ax_iacom_sgc_save (k) and δ3 (deviation degree) change.

At time T1, imax_iacom_sgc_comp_c
When ounter = 8000 is established, coefficient update is completely stopped. After that, when the signal input to the echo canceller changes from the RBT signal to the voice signal at time T2, the echo attenuation amount iacom (k) sharply decreases. This is because the echo canceller has not learned the echo path in the voice band. Therefore, at this time, the echo attenuation ia
The difference between com (k) and the maximum tracking variable imax_iacom (k) is the threshold α
The maximum value leak variable due to the operation of the above equation (10)
imax_iacom_sgc_save (k) also gradually decreases. Maximum value tracking variable imax_iacom (k) and maximum value leak variable imax_iacom_
When the deviation of sgc_save (k) reaches δ3, the coefficient update signal ad
p is output from the deviation width determiner 11 to the adaptive filter coefficient update control circuit 13, and the maximum value tracking variable imax_iaco
m (k) and the maximum leak variable imax_iacom_sgc_save (k) are reset to the echo attenuation amount iacom (k) at that time. After that, the filter coefficient is updated while the maximum value tracking variable is being updated.

As described above, in the echo canceller of the present invention, when the signal input to the echo canceller changes from the periodic signal to the voice signal without using a special detector for discriminating the periodic signal and the voice signal. Re-learning can be started automatically.

Further, the echo canceller of the present invention can detect the busy signal BT even when the echoes of the busy signal BT and the call signal RBT are simultaneously input to the echo canceller, and the busy signal BT is used as in the conventional case. The problem that the signal BT cannot be detected and the line is not released does not occur.
The reason will be described below.

As described above, the far-end talker does not answer the telephone,
When the near-end speaker hangs up while listening to the ringing tone (RBT signal), a BT signal (busy signal) is generated and input to the echo canceller. In this case, the RBT signal is input to the Rin terminal of the echo canceller several times, and then the BT signal is input to the Sin terminal. As described with reference to FIG. 2, time T during reception of the RBT signal
At 1, the coefficient update of the echo canceller is stopped, and the learning of the echo path for the RBT signal is completely completed at that point, so that after time T1, the echo of the RBT signal is almost completely removed. Therefore, even if the BT signal (busy signal) is input from the Sin terminal after time T1, RB
Since only the echo of the T signal is almost completely removed, BT
The signal is output from the Sout terminal without being canceled. This is because at time T1, the learning operation of the echo canceller has stopped and the echo canceller is no longer in the RB.
This is because no signal other than the signal for canceling the echo of the T signal is generated.

As described above, in the first embodiment of the present invention, the power calculators 5 and 7 for calculating the power of the signal input from the Rin terminal and the Sin terminal are provided, and the echo attenuation amount is calculated from the calculated power. Is provided with the echo attenuation amount calculator 6 and the maximum value tracker 9 for tracking the maximum value of the output of the echo attenuation amount computer 6 is provided, and the maximum value for determining whether or not the maximum value is updated to a new maximum value An update determining unit 8 is provided, and a maximum value leak calculator 10 that leaks the maximum value held and gradually decreases when the maximum value is not updated is provided, and the output of the maximum value leak calculator 10 and the maximum value tracker 9 are provided.
The deviation width determiner 11 that calculates the deviation from the output of the adaptive filter 15 is provided, and the adaptive filter 15 coefficient control circuit 13 that controls the start and stop of the coefficient update of the adaptive filter 15 is provided. When the maximum value is not updated for the number of times
The BT echo signal is surely removed so that the BT signal can be transmitted without being canceled, and even after the maximum value update determination unit 8 stops updating the coefficient of the adaptive filter 15, the determination result of the deviation width determination unit 11 determines the input. When the signal changes from the RBT signal to the voice signal, the echo canceller can restart the learning automatically, which solves the conventional problem that the line cannot be opened and distinguishes the periodic signal from the voice signal. Echoes of both the periodic signal and the voice signal can be removed without using a complicated device for doing so.

Second Embodiment FIG. 3 is a block diagram showing the configuration of an echo canceller according to the second embodiment of the present invention. The second embodiment is different from the first embodiment in that the deviation time determiner 20 is used in place of the deviation width determiner 11, and the other configurations are the same. Therefore, the operations of the deviation time determination unit 20 and the adaptive filter coefficient update control circuit 13 will be described below, and the description of the others will be omitted.

After stopping the maximum value update in the maximum value tracker 9,
Echo attenuation iacom (k) and maximum tracking variable imax_iacom (k)
When the difference between and exceeds the threshold value α, the maximum leak calculator 1
Maximum value leak variable imax_iacom_sgc_save (k) output by 0
Is gradually reduced as in the first embodiment. As shown in FIG. 4, the divergence time determination unit 20 is the maximum value tracking unit 9
When the state where the output of ∘ is deviated from the output of the maximum leak calculator 10 continues for time t1, the coefficient update signal adp is output to the adaptive filter coefficient update control circuit 13. The adaptive filter coefficient update control circuit 13 responds to the coefficient update signal adp, restarts the coefficient update of the adaptive filter 15 and starts the re-learning of the echo path, as in the first embodiment.

The second embodiment makes it possible to control the relearning start timing of the echo path by time without waiting for the echo attenuation amount to decrease to a certain value.
In the second embodiment, when the output of the maximum value tracking unit 9 is separated from the output of the maximum value leak calculator 10 for a time t1, the deviation time determination unit 20 determines that the coefficient update signal ad
Although p is output to the adaptive filter coefficient update control circuit 13, the two are not necessarily completely in agreement and the coefficient update is performed when the difference between the two does not fall within a predetermined threshold for a time t1. The signal adp may be output to the adaptive filter coefficient update control circuit 13.

As described above, in the second embodiment, the deviation time determining unit 20 is provided, and the state in which the output of the maximum value tracking unit 9 deviates from the output of the maximum value leak computer 10 is time t1.
Since it is configured to output the coefficient update signal adp to the adaptive filter coefficient update control circuit 13 when it continues over, the echo canceller having the same effect as that of the first embodiment,
The re-learning start timing of the echo path can be controlled not by deterioration of the echo attenuation amount but by time.

Third Embodiment FIG. 5 is a block diagram showing the configuration of an echo canceller according to a third embodiment of the present invention. The third embodiment is different from the second embodiment in that a deviation width / deviation time determiner 30 is used instead of the deviation time determiner 20, and the other configurations are the same. Therefore, in the following, the deviation width / deviation time determination device 30
Only the operation of will be described.

As in the first embodiment, the deviation width / deviation time determination unit 30 determines the maximum value leak variable imax_iacom_sgc_save.
When the deviation width between (k) and the maximum value tracking variable imax_iacom (k) reaches δ3, or as in the second embodiment, the maximum value leak variable imax_iacom_sgc_save (k) is set to the maximum value tracking variable imax.
When at least one of the cases where the state deviating from _iacom (k) continues for a certain time t1 is satisfied, the coefficient update signal adp is output to the adaptive filter coefficient update control circuit 13,
The coefficient update of the adaptive filter 15 is restarted.

According to the third embodiment, the coefficient update timing of the adaptive filter 15 can be controlled more precisely than in the first and second embodiments. This is because even if the echo removal amount rapidly deteriorates, relearning of the echo path will automatically start after a certain period of time.
This makes it possible to prevent the call quality from deteriorating.

Fourth Embodiment FIG. 6 is a block diagram showing the configuration of an echo canceller according to a fourth embodiment of the present invention. In the fourth embodiment, maximum value detection / detection is performed between the echo attenuation amount calculator 6 and the power calculator 5 and between the echo attenuation amount calculator 6 and the power calculator 7.
This is different from the first embodiment in that leak calculators 40 and 42 are provided respectively. The reason why the maximum value detection / leakage calculators 40 and 42 are provided in this embodiment will be described below.

In the first embodiment, the smoothing constant for a relatively long time must be used to calculate the echo attenuation amount. This is because the echo path generally includes an initial delay, and this initial delay causes the echo signal to enter the echo canceller and the reference signal (the signal that causes the echo) to enter the echo canceller. This is because there is a gap in For example, assume that the echo path has the following characteristics. That is, the delay time is 10
Consider an echo path with 0 samples and 6 dB of attenuation (corresponding to 0.5 times the amplitude). When a signal with a constant level like a tone signal and a constant period is always input to the echo canceller, the echo is always observed after a delay of 100 samples and its amplitude becomes 0.5 times, so the observed echo is It is easy to find out which part of the reference signal is the echo and to correctly time the echo signal and the beginning part of the reference signal.

However, when the reference signal is switched from the tone signal to the voice signal, difficulty occurs. Because
Since the amplitude of the audio signal changes randomly, when observing the echo, it is not possible to know which part of the reference signal is the echo, and it is not possible to correctly time the echo signal and the beginning of the reference signal. . It is not possible to determine how much the amplitude of the reference signal has decreased unless the echo signal and the beginning of the reference signal are properly timed. That is, the echo attenuation amount cannot be accurately obtained.

As described above, at the time of switching from the periodic signal to the voice signal, since the echo path has not been learned, it is not possible to accurately match the timings of the beginning portions of the echo signal and the reference signal. Therefore, in the first embodiment, the echo attenuation amount is obtained from the global change of the echo signal, and therefore the power is calculated with a relatively large smoothing constant in the above equation (1). However, increasing the smoothing constant inevitably slows down the operation of the echo canceller and lowers the response speed. In the fourth embodiment, the response speed is increased by providing the maximum value detection / leakage calculators 40 and 42.

The power calculators 5 and 7 and the maximum value detection / leakage calculator 4 of the echo canceller of the fourth embodiment will be described below.
The operation of 0, 42 will be described. The operation of the other elements is the same as that of the first embodiment, and therefore its explanation is omitted.

The power calculators 5 and 7 calculate power in the same manner as in the first embodiment, but in the fourth embodiment, the smoothing constant is reduced to δ 1 = 2 ^-3 to improve the responsiveness to changes. There is.

For example, in the power calculator 7, the level L_rin (k) of the Rin signal is L_irin (k) = L_irin (k-1) x (1-δ1) + | L_irin (k) | x δ1 (12) Calculate as.

The signal levels calculated by the power calculators 5 and 7 are input to maximum value detection / leakage calculators 40 and 42, respectively. For example, the maximum value detection / leakage calculator 42 on the Rin terminal side determines the maximum value imax_irin of the power of the Rin signal.
Is calculated according to the following equation (13) and the maximum value is traced.

If L_rin (k) is the maximum among the powers calculated up to that point, imax_irin (k) = L_irin (k) (13) If not, imax_irin (k) = imax_irin (k -1) (14) However, imax_irin (0) = 0.

Similarly to the above, the output signal Res of the adder 14
Also regarding the maximum value detection / leakage calculator 40, imax_ires
Calculate (k) and track its maximum. In this embodiment,
When the tracked maximum value is not updated, it is leaked and gradually decreased.

The echo attenuation amount calculator 6 detects the maximum value /
Maximum value imax_iri output from the leak calculator 40, 42
Let n (k) and imax_ires (k) be Rin in the first embodiment.
The signal level L_rin (k) and the Res signal level L_res (k) are treated in the same manner, and the echo attenuation amount is calculated. The subsequent operation is the first
Since it is the same as the embodiment described above, it will not be described here.

The present embodiment utilizes the property that the echo usually becomes maximum when the reference signal becomes maximum, and as long as this property is used, it is not necessary to perform time-axis alignment of the signal. As described above, according to the fourth embodiment of the present invention, parameters that can be detected instantaneously without being compared with smoothed parameters and that are less susceptible to delay, that is, a transmission signal (reference signal) and "Maximum amplitude part" of each received signal (echo signal)
Since the echo attenuation amount is calculated using the power of as a parameter, an echo canceller with a fast response speed can be obtained.

Fifth Embodiment FIG. 7 is a block diagram showing the configuration of an echo canceller according to the fifth embodiment of the present invention. The fifth embodiment is a combination of the configuration of the fourth embodiment and the configuration of the second embodiment, and is implemented in that a deviation time determining unit 20 is used instead of the deviation width determining unit 11. Different from the form 4. The operation of the deviation time determination unit 20 has already been described, and will not be described here. According to the fifth embodiment, the fourth
It becomes possible to control the re-learning timing of the adaptive filter 15 of the embodiment of the present invention not by deterioration of the echo attenuation amount but by time.

Sixth Embodiment FIG. 8 is a block diagram showing the structure of an echo canceller according to a sixth embodiment of the present invention. The sixth embodiment is a combination of the fourth embodiment and the third embodiment, and the fourth embodiment is that the deviation width / deviation time judgment device 30 is used instead of the deviation width judgment device 11. Different from the form. The operation of the deviation width / deviation time determination unit 30 has already been described, and will not be described here.

According to the sixth embodiment, in addition to the advantages of the fourth embodiment, the echo canceller has the advantage of the third embodiment, that is, the advantage that the re-learning timing of the echo canceller can be controlled more precisely. Is obtained.

Seventh Embodiment FIG. 9 is a block diagram showing the configuration of an echo canceller according to the seventh embodiment of the present invention. In the seventh embodiment, Rin
It differs from the first embodiment in that a power calculator 70 connected to the Sin terminal is used in place of the power calculator 7 connected to the terminal, and an echo cancellation amount calculator 71 is used in place of the echo attenuation amount calculator 6. Below, power calculator 7
The operation of 0 and the echo cancellation amount calculator 71 will be described. The operation of the other elements is the same as that of the first embodiment, and therefore its explanation is omitted.

The power calculator 70 calculates the power L_Sin (k) of the signal input from the Sin terminal to the adder 14 according to the equation (15), and the power calculator 5 calculates the power L_Res (k of the signal output from the adder 14. ) Is calculated according to equation (16).

L_Sin (k) = L_Sin (k-1) × (1-δ) + ｜ Sin (k) ｜ × δ4 (15) L_Res (k) = L_Res (k-1) × (1-δ) + | a × δ4 ... (16) where ^{δ4 = 2 -3 | Res (k} ). δ4 may be set to a larger value (faster response) than that in the first embodiment. The calculated powers L_Sin (k) and L_Res (k) are output to the echo cancellation amount calculator 71. The echo cancellation amount calculator 71 calculates the echo cancellation amount iacanc (k) according to the equation (17).

Iacanc (k) = 20 × LOG _1O (L_Sin (k) / L_Res (k)) (17) The echo cancellation amount calculator 71 uses iacanc (k) as the maximum value tracker 9
Output to. The maximum value tracker 9 uses this echo cancellation amount iacanc
The maximum value is tracked by treating (k) in the same manner as the echo attenuation amount iacom (k). The operation of the elements after the maximum value tracker 9 is similar to that of the first embodiment, and will not be described here.

In the seventh embodiment, since the power calculator 70 and the power calculator 5 are provided on the input side and the output side of the adder 14, the calculation of the echo cancellation amount is not affected by the delay of the echo path at all. Therefore, by using a small smoothing constant, the response speed can be improved without detecting the maximum value of the signal entering the Sin terminal and the maximum value of the Res signal. Furthermore, the maximum value detection mechanism is unnecessary,
The scale of software and hardware can be reduced.

Eighth Embodiment FIG. 10 is a block diagram showing the configuration of an echo canceller according to the eighth embodiment of the present invention. The eighth embodiment differs from the seventh embodiment in that the deviation time determiner 20 is used instead of the deviation width determiner 11. The difference in operation between the deviation time determiner 20 and the deviation width determiner 11 is as described in the second embodiment, and will not be described here.

According to the eighth embodiment, in addition to the advantages of the seventh embodiment, it is possible to obtain an echo canceller having the advantage that the re-learning timing of the echo path can be controlled temporally instead of the echo attenuation amount.

Ninth Embodiment FIG. 11 is a block diagram showing the arrangement of an echo canceller according to the ninth embodiment of the present invention. The ninth embodiment is different from the seventh embodiment in that the deviation width / deviation time judgment device 30 is used instead of the deviation width judgment device 11. The difference in operation between the deviation width / deviation time determiner 30 and the deviation width determiner 11 is as described in the third embodiment, and will not be described here.

According to the ninth embodiment, in addition to the advantages of the seventh embodiment, the re-learning timing of the echo path is set to the time,
And an echo canceller having the advantage of being controllable by both deterioration of the echo attenuation amount.

Although the example in which the echo canceller of the present invention is used for the Internet telephone has been described above, the application of the echo canceller of the present invention is not limited to this, and general telephone lines, mobile telephones, car telephones, It can be applied to any device and system that needs to remove echo, such as a video conference device.

[0095]

According to the present invention, it is possible to provide an echo canceller capable of removing echoes of both a periodic signal and a voice signal at low cost.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an echo canceller according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an example of changes over time in an echo attenuation amount, a maximum value tracking variable, and a maximum value leak variable in the echo canceller of the first embodiment.

FIG. 3 is a block diagram showing a configuration of an echo canceller according to a second embodiment of the present invention.

FIG. 4 is a diagram showing an example of temporal changes of an echo attenuation amount, a maximum value tracking variable, and a maximum value leak variable in the echo canceller of the second embodiment.

FIG. 5 is a block diagram showing a configuration of an echo canceller according to a third embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration of an echo canceller according to a fourth embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of an echo canceller according to a fifth embodiment of the present invention.

FIG. 8 is a block diagram showing a configuration of an echo canceller according to a sixth embodiment of the present invention.

FIG. 9 is a block diagram showing a configuration of an echo canceller according to a seventh embodiment of the present invention.

FIG. 10 is a block diagram showing a configuration of an echo canceller according to an eighth embodiment of the present invention.

FIG. 11 is a block diagram showing a configuration of an echo canceller according to a ninth embodiment of the present invention.

FIG. 12 is a diagram illustrating the operation of a conventional echo canceller.

[Explanation of symbols]

101 echo canceller, 102 echo canceller, 103 gateway, 104 hybrid transformer, 105 hybrid transformer, 106
PBX, 5 power calculator, 6 echo attenuation calculator, 7 power calculator, 8 maximum value update judging device,
9 Maximum Tracker, 10 Maximum Leakage Calculator, 1
1 Deviation width determiner, 12 Double talk detector, 1
3 adaptive filter coefficient update control circuit, 14 adder,
15 Adaptive filter, 20 Deviation time determination device, 30
Deviation width / deviation time determination device, 40 maximum value detection / leak circuit, 42 maximum value detection / leak circuit, 70 power calculator, 71 echo consumption calculator.

Claims (27)

[Claims] 1. An echo canceller having an adaptive filter for generating a pseudo echo signal that is added to the echo signal to attenuate the echo signal in order to prevent the echo signal of the received signal from returning to the transmission side. First means for calculating the attenuation amount of the echo signal at fixed time intervals from the power of the signal and the power of the echo signal to which the pseudo echo signal is added; and the maximum attenuation amount calculated by the first means. Second means for tracking and holding the value, and a value obtained by subtracting the current value of the attenuation amount of the echo signal from the maximum value of the attenuation amount held by the second means exceeds a first threshold value, A third means for reducing the maximum value of the attenuation amount output from the second means at a constant rate for each of the constant time intervals and holding the value, and an attenuation amount retained by the second means. And the maximum of Means for calculating the deviation width of the value held by the means at the constant time interval, and when the deviation width calculated by the fourth means exceeds a second threshold value, the second means Both the maximum value of the attenuation amount held by the means and the value held by the third means are reset to the current value of the attenuation amount of the echo signal, and the filter coefficient updating operation of the adaptive filter is started. Echo canceller. 2. A fifth means for detecting whether or not the maximum value of the attenuation amount held by the second means is updated, and the maximum value of the attenuation amount held by the second means is updated. That is, when the fifth means outputs, the filter coefficient updating operation of the adaptive filter is started, and the maximum value of the attenuation amount held by the second means is not updated for a certain period. The echo canceller according to claim 1, wherein the filter coefficient updating operation of the adaptive filter is stopped when the fifth means detects it. 3. A sixth means for detecting whether or not there is a double-talk state, wherein when the double-talk state is detected by the sixth means, the filter coefficient updating operation of the adaptive filter is stopped. 3. The echo canceller according to claim 2, wherein the filter coefficient updating operation of the adaptive filter is started when the sixth means stops detecting the double talk state. 4. The control for starting and stopping the filter coefficient updating operation of the adaptive filter is performed in the order of priority of output of the fourth means> output of the fifth means> output of the sixth means. The echo canceller according to claim 3, which is performed. 5. The first means calculates the power of the input signal for each constant time interval for each of the echo signals added to the reception signal and the pseudo echo signal input to the first means. A power calculation means for holding the maximum value of the calculated power and, when the held maximum value is not updated, for reducing the held maximum value at a constant rate at the constant time interval; 5. The echo canceller according to any one of claims 1 to 4, further comprising: / leak means for calculating the attenuation amount of the echo signal based on the maximum value output from the maximum value tracking / leak means. . 6. An echo canceller having an adaptive filter for generating a pseudo echo signal that is added to the echo signal and attenuates the echo signal in order to prevent the echo signal of the received signal from returning to the transmission side. First means for calculating the attenuation amount of the echo signal at fixed time intervals from the power of the signal and the power of the echo signal to which the pseudo echo signal is added; and the maximum attenuation amount calculated by the first means. Second means for tracking and holding a value; and a value obtained by subtracting the current value of the attenuation amount of the echo signal from the maximum value of the attenuation amount held by the second means exceeds a predetermined threshold value. A third means for reducing the maximum value of the attenuation amount output from the second means at a constant rate for each of the constant time intervals and holding the value, and an attenuation amount held by the second means. Maximum and above And a fourth means for measuring the length of time that has elapsed since the value held by the third means starts to deviate, and when the time measured by the fourth means reaches a predetermined value, Resetting both the maximum value of the attenuation amount held by the second means and the current value of the attenuation amount of the echo signal, and starting the filter coefficient updating operation of the adaptive filter. Echo canceller featuring. 7. A fifth means for detecting whether or not the maximum value of the attenuation amount held by the second means has been updated, and the maximum value of the attenuation amount held by the second means is updated. That is, when the fifth means outputs, the filter coefficient updating operation of the adaptive filter is started, and the maximum value of the attenuation amount held by the second means is not updated for a certain period. The echo canceller according to claim 6, wherein the filter coefficient updating operation of the adaptive filter is stopped when the fifth means detects it. 8. A sixth means for detecting whether or not a double talk state is present, wherein the filter coefficient updating operation of the adaptive filter is stopped when the double talk state is detected by the sixth means, 8. The echo canceller according to claim 7, wherein when the sixth means stops detecting the double talk state, the filter coefficient updating operation of the adaptive filter is started. 9. The control of the start and stop of the filter coefficient updating operation of the adaptive filter is performed in the order of priority of output of the fourth means> output of the fifth means> output of the sixth means. The echo canceller according to claim 8, which is performed. 10. The first means calculates the power of the input signal for each constant time interval for each of the echo signals to which the reception signal and the pseudo echo signal added to the first means are added. A power calculation means for holding the maximum value of the calculated power and, when the held maximum value is not updated, for reducing the held maximum value at a constant rate at the constant time interval; 10. The echo canceller according to any one of claims 6 to 9, further comprising: / leak means for calculating the attenuation amount of the echo signal based on the maximum value output from the maximum value tracking / leak means. . 11. An echo canceller having an adaptive filter for generating a pseudo echo signal that is added to the echo signal and attenuates the echo signal in order to prevent the echo signal of the received signal from returning to the transmission side. First means for calculating the attenuation amount of the echo signal from the power of the signal and the power of the echo signal to which the pseudo echo signal has been added at constant time intervals, and the maximum value of the attenuation amount calculated by the first means And a second means for tracking and holding, and a value obtained by subtracting the current value of the attenuation amount of the echo signal from the maximum value of the attenuation amount held by the second means exceeds a first threshold value. A third means for reducing the maximum value of the attenuation amount output from the second means at a constant rate at the constant time interval and holding the value, and a maximum attenuation value held by the second means. Value and above The deviation width of the value held by the means is calculated for each of the constant time intervals, and after the maximum value of the attenuation amount held by the second means and the value held by the third means start to deviate. A fourth means for measuring the length of the elapsed time, wherein the deviation width calculated by the fourth means exceeds a second threshold value, or the time measured by the fourth means has a predetermined value. When it exceeds, both the maximum value of the attenuation amount held by the second means and the value held by the third means are reset to the current value of the attenuation amount of the echo signal, and the filter coefficient of the adaptive filter is set. An echo canceller characterized by starting an update operation. 12. A fifth means for detecting whether or not the maximum value of the attenuation amount held by the second means has been updated,
When the fifth means outputs that the maximum value of the attenuation amount held by the second means is updated, the filter coefficient updating operation of the adaptive filter is started, and the attenuation held by the second means is started. 12. The echo canceller according to claim 11, wherein the filter coefficient updating operation of the adaptive filter is stopped when the fifth means detects that the maximum value of the quantity has not been updated for a certain period. . 13. A sixth means for detecting whether or not a double talk state is present, wherein the filter coefficient updating operation of the adaptive filter is stopped when the double talk state is detected by the sixth means, 13. The filter coefficient updating operation of the adaptive filter is started when the sixth means stops detecting a double talk state.
Echo canceller described in. 14. The control of the start and stop of the filter coefficient updating operation of the adaptive filter is performed by the output of the fourth means>
14. The echo canceller according to claim 13, wherein the output of the fifth means> the output of the sixth means is performed in the order of priority. 15. The first means calculates the power of an input signal for each of the echo signals to which the received signal and the pseudo echo signal added to the first means are added, at regular time intervals. A power calculation means for holding the maximum value of the calculated power and, when the held maximum value is not updated, for reducing the held maximum value at a constant rate at the constant time interval; 15. The echo canceller according to any one of claims 11 to 14, further comprising: / leak means for calculating the attenuation amount of the echo signal based on the maximum value output by the maximum value tracking / leak means. . 16. An echo canceller having an adaptive filter for generating a pseudo echo signal which is added to the echo signal and which cancels the echo signal in order to prevent the echo signal of the received signal from returning to the transmission side. First means for calculating an erasing amount of the echo signal at fixed time intervals from the power of the signal and the power of the echo signal to which the pseudo echo signal is added; and the maximum erasing amount calculated by the first means. Second means for tracking and holding the value, and a value obtained by subtracting the current value of the erasing amount of the echo signal from the maximum erasing amount held by the second means exceeds a first threshold value, A third means for reducing the maximum value of the erase amount output from the second means at a constant rate at the constant time intervals and holding the value, and an erase amount held by the second means. And the maximum value of Third means for calculating the deviation width of the value held by the third means at the constant time interval, and when the deviation width calculated by the fourth means exceeds a second threshold value, Resetting both the maximum value of the cancellation amount output from the second means and the value held by the third means to the current value of the cancellation amount of the echo signal, and starting the filter coefficient updating operation of the adaptive filter. Echo canceller featuring. 17. A fifth means for detecting whether or not the maximum value of the erase amount held by the second means is updated,
When the fifth means outputs that the maximum value of the erasure amount held by the second means is updated, the filter coefficient updating operation of the adaptive filter is started, and the erasure held by the second means is started. 17. The echo canceller according to claim 16, wherein when the fifth means detects that the maximum value of the quantity has not been updated for a certain period of time, the filter coefficient updating operation of the adaptive filter is stopped. . 18. A sixth means for detecting whether or not a double talk state is present, wherein when the double talk state is detected by the sixth means, the filter coefficient updating operation of the adaptive filter is stopped. 18. The filter coefficient updating operation of the adaptive filter is started when the sixth means stops detecting a double talk state.
Echo canceller described in. 19. The control of the start and stop of the filter coefficient updating operation of the adaptive filter is performed by the output of the fourth means>
19. The echo canceller according to claim 18, wherein the output of the fifth means> the output of the sixth means is performed in order of priority. 20. An echo canceller having an adaptive filter for generating a pseudo echo signal which is added to the echo signal and which cancels the echo signal, in order to prevent the echo signal of the received signal from returning to the transmission side. First means for calculating an erasing amount of the echo signal at fixed time intervals from the power of the signal and the power of the echo signal to which the pseudo echo signal is added; and the maximum erasing amount calculated by the first means. Second means for tracking and holding a value; and a value obtained by subtracting the current value of the erasing amount of the echo signal from the maximum erasing amount held by the second means exceeds a predetermined threshold value. A third means for reducing the maximum value of the erase amount output from the second means at a constant rate for each of the constant time intervals and holding the value, and an erase amount of the erase amount held by the second means. Maximum and before A fourth means for measuring the length of time that has elapsed since the value held by the third means began to deviate, and when the time measured by the fourth means reaches a predetermined value, Both the maximum value of the cancellation amount held by the second means and the value held by the third means are reset to the current value of the cancellation amount of the echo signal, and the filter coefficient updating operation of the adaptive filter is started. An echo canceller that is characterized. 21. A fifth means for detecting whether or not the maximum value of the erase amount held by the second means is updated,
When the fifth means outputs that the maximum value of the erasure amount held by the second means is updated, the filter coefficient updating operation of the adaptive filter is started, and the erasure held by the second means is started. 21. The echo canceller according to claim 20, wherein when the fifth means detects that the maximum value of the quantity has not been updated for a certain period of time, the filter coefficient updating operation of the adaptive filter is stopped. . 22. A sixth means for detecting whether or not there is a double talk state is provided, and when the double talk state is detected by the sixth means, the filter coefficient updating operation of the adaptive filter is stopped, 22. The filter coefficient updating operation of the adaptive filter is started when the sixth means stops detecting a double talk state.
Echo canceller described in. 23. The output of the fourth means controls the start and stop of the filter coefficient updating operation of the adaptive filter.
23. The echo canceller according to claim 22, wherein the output of the fifth means> the output of the sixth means is performed in order of priority. 24. An echo canceller having an adaptive filter for generating a pseudo echo signal which is added to the echo signal to cancel the echo signal in order to prevent the echo signal of the received signal from returning to the transmission side. First means for calculating an erasing amount of the echo signal from the power of the signal and the power of the echo signal to which the pseudo echo signal is added at constant time intervals, and the maximum value of the erasing amount calculated by the first means A second means for tracking and holding the value, and a value obtained by subtracting the current value of the cancellation amount of the echo signal from the maximum value of the cancellation amount held by the second means exceeds a first threshold, A third means for reducing the maximum value of the erase amount output from the second means at a constant rate at the constant time interval and holding the value, and a maximum erase amount held by the second means. Value and the third The deviation width of the value held by the step is calculated at each of the constant time intervals, and it has elapsed since the deviation of the maximum value of the erase amount held by the second means and the value held by the third means has started. And a fourth means for measuring the length of time, the deviation width calculated by the fourth means exceeds a second threshold value, or the time measured by the fourth means exceeds a predetermined value. At this time, both the maximum value of the cancellation amount held by the second means and the value held by the third means are reset to the current value of the attenuation amount of the echo signal, and the filter coefficient of the adaptive filter is updated. An echo canceller characterized by starting operation. 25. A fifth means for detecting whether or not the maximum value of the erase amount held by the second means is updated,
When the fifth means outputs that the maximum value of the erasure amount held by the second means is updated, the filter coefficient updating operation of the adaptive filter is started, and the erasure held by the second means is started. 25. The echo canceller according to claim 24, wherein the filter coefficient updating operation of the adaptive filter is stopped when the fifth means detects that the maximum value of the quantity has not been updated for a certain period. . 26. A sixth means for detecting whether or not in a double talk state is provided, and when the double talk state is detected by the sixth means, the filter coefficient updating operation of the adaptive filter is stopped, 26. The filter coefficient updating operation of the adaptive filter is started when the sixth means stops detecting a double talk state.
Echo canceller described in. 27. The start and stop of the filter coefficient updating operation of the adaptive filter is controlled by the output of the fourth means>
27. The echo canceller according to claim 26, wherein the output of the fifth means> the output of the sixth means is performed in order of priority.