JPH10210132A - High quality loudspeaking information communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the sound quality of a loudspeaking system and to reduce the probability of incidence of signing by applying amplitude compression to an input signal to a code circuit of the loudspeaking system using an echo canceller and applying amplitude expansion to an output signal of a decoding circuit. SOLUTION: An amplitude compression 112 is provided between a code circuit 19 and an echo canceller 3 that eliminates an echo component which results from a signal in a reception path and appears at a transmission path via an echo path. Furthermore, an amplitude expansion circuit 113 is provided between the echo canceller 3 and a decoding circuit 110. Since a level of input and output signals at the echo canceller is kept to a same dynamic range at all times, deterioration in the quality of a communication voice due to deterioration in the reverberation cancelling characteristic and clipping noise is prevented, mis-detection caused on the occurrence of a double-talk is avoided and clear full duplex communication is realized. The probability of incidence of singing is considerably reduced by improving the stability of the input and output level and then the loudspeaking information communication system with high quality is realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for a communication line, an indoor sound field control device, and a high-quality audio communication conference device, and an acoustic reverberation in which a signal on a receiving path appears on a transmitting path via an acoustic reverberating path. The present invention relates to a high quality loudspeaker information communication system using an acoustic reverberation removing device for removing components.

[0002]

2. Description of the Related Art Generally, an acoustic echo canceler removes reflection caused by impedance mismatch of a two-wire / four-wire converter in a long-distance telephone line using a communication satellite and a submarine cable, and a loudspeaker such as a video conference system. , Which can be broadly divided into those that remove the reverberation due to the acoustic coupling of the speaker's voice, and are composed of a correction amount calculation circuit, a variable coefficient filter that generates a pseudo acoustic reverberation, and a subtraction circuit. The basic operation of the acoustic reverberation removing device will be described below. FIG.
FIG. 2 is a diagram showing a basic configuration of the acoustic reverberation removing device 3. The signal input terminal 31 is connected to a signal output terminal 32, and an input signal from the signal input terminal 31 is branched and supplied to a variable coefficient filter 33 to generate a pseudo acoustic reverberation. The input signal from the signal input terminal 34 and the pseudo acoustic reverberation output from the variable coefficient filter 33 are input to a subtraction circuit 35, in which the acoustic reverberation component in the signal input from the signal input terminal 34 is removed. The output of 35 is output to a signal output terminal 36. The output of the signal output terminal 36 and the signal input terminal 31
Is input to the correction amount calculation circuit 37, and the filter coefficient of the variable coefficient filter 33 is corrected by the output of the coefficient correction amount calculation circuit 7. In the variable coefficient filter 33, the signal from the signal input terminal 31 is input to the signal input register 38, and the product sum of the signal of the signal input register 38 and the pseudo impulse response of the pseudo impulse response register 39 is calculated by the product sum circuit 310. The output of the product-sum circuit 310 is output as a pseudo acoustic echo. Assuming that the signal propagation characteristic of the acoustic reverberation path is linear and represented by an FIR type digital filter, and using its impulse response h (t) and input received signal x (t), the sample time interval is ^T. , The acoustic reverberation y _{k at} time _k ^T is represented by y _k = h ^T x _k (1). Here, h = [h ₁ , h ₂ ,..., H _n ] ^T (2) x = [x _k−1 ,..., X _kn ] ^{T T} : Vector transposition.

[0003] On the other hand, the estimated value of h at the time _k ^T hs
if _k, the estimated value ys _k of y _k is given by ^{_{ys k = hsk T x k (}} 3). In the acoustic reverberation removing device 3, when the signal input terminal 31 has the first input signal and the signal input terminal 34 has no second input signal and only the acoustic reverberation exists, the reverberation removing operation is performed as the adaptive operation state. I do. This adaptive operation algorithm generally includes a learning identification method (Atsuhiko Noda, Jinichi Nagumo: “System Learning Identification Method”, Measurement and Control, 7, 9, p.
p.597-605 (1968)). H by learning identification method
successive correction of s _k is performed by _{hs k + 1 = hs k +} α (x k e k) / x k T x k (4). However, the e _k = y _k -ys _k, is 0 <α ≦ 1 (5) e k is referred to as residual acoustic echo. Such a calculation operation is performed in the coefficient correction amount calculation circuit 37. The contents of the pseudo impulse response register 39 variable coefficient series hs _k is stored. α is a coefficient updating gain for determining the sensitivity of estimation, and the closer the correction gain is to 1.0, the greater the amount of correction can be given, and high-speed acoustic reverberation can be removed. It is necessary to change and set according to the line condition. The actual situation is that the determination of the coefficient update gain α currently depends on empirical rules. The coefficient update gain α may be variably controlled depending on the magnitude of the residual acoustic reverberation, or may be set in accordance with the indoor characteristics (for example, Shoji Makino, Nobuo Koizumi: “Eco-Canceller Adaptive Performance in Indoor Sound Field”). About the improvement ”,
IEICE (A), J71-A, 12, pp. 2212-2214 (1988-12)). The acoustic echo canceller 3 is usually used in the loudspeaker information communication system 4 shown in FIG. The reception signal output terminal 42
Digital to convert digital signal to analog signal
Connected to the speaker 47 via the analog converter 43,
The microphone 48 is connected to the transmission signal input terminal 44 via an analog-digital converter 45 that converts an analog signal into a digital signal. The digital signal output from the transmission output terminal 46 is connected to an encoding circuit 49 for compressing the amount of information, and a decoding circuit 410 for reconstructing the digital signal is connected to the reception signal input terminal 41. The receiving signal input terminal 41 is connected to the signal input terminal 31.
The reception signal output terminal 42 is connected to the signal output terminal 32.
The transmission signal input 44 is connected to the signal input terminal 34, and the transmission output terminal 45 is connected to the signal output terminal 36.

[0004]

A signal such as a sound collected from a microphone is quantized by an analog-digital converter at a specified sampling frequency and a specified number of bits to be converted into a digital signal. Usually, this number of bits is set so as to perform linear quantization with an amplitude of 16 bits at the maximum. However, the maximum number of bits provided in the encoding circuit and the decoding circuit is set to a number smaller than 16 bits due to the internal processing of each circuit. Also, the value differs depending on the encoding / decoding method to be operated. For this reason, when a value larger than the setting of the encoding / decoding circuit is input, it is all clipped and becomes noise, which deteriorates the sound quality. Then, a difference occurs between the gains of the input and output signals to the acoustic reverberation removing device, so that the erasing characteristics are likely to be degraded and the sound is likely to be generated. SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a high-quality loudspeaker information communication system which eliminates the above-mentioned problems, improves the quality of call voice, and improves clarity.

[0005]

According to the present invention, there is provided a receiving signal input terminal, a receiving signal output terminal, a transmitting signal input terminal, a transmitting signal output terminal, and a digital signal. A digital-to-analog converter for converting an analog signal to be output to a reception signal output terminal, an analog-digital converter for converting an analog signal input from the transmission signal input terminal to a digital signal, and the reception signal input A variable coefficient digital filter having a pseudo impulse response register that receives a reception signal of a terminal; and a sound echo component of a reception signal input from the reception signal output terminal to the transmission signal input terminal via an acoustic reverberation path. A coefficient correction amount arithmetic circuit is used to minimize the residual signal obtained by subtracting the pseudo acoustic reverberation generated by the variable coefficient digital filter. An acoustic echo canceller in which a number sequence is sequentially updated, an encoding circuit for encoding a digital signal,
In a loudspeaker information communication system using a decoding circuit for decoding a code and reconstructing a digital signal, an amplitude compression circuit for controlling the amplitude of a digital signal input to the coding circuit, and an amplitude of a digital signal output from the decoding circuit A high-quality loudspeaker information communication system characterized in that a digital signal having a constant amplitude can be supplied to the acoustic reverberation removing device by using an amplitude expanding circuit for controlling the acoustic echo canceller, and a stable erasing characteristic is always realized. When a different method is adopted for the encoding method executed by the encoding circuit and the decoding method executed by the decoding circuit, the amplitude compression circuit and the amplitude expansion circuit are operated independently, whereby A high-quality loudspeaker information communication system characterized by suppressing noise generation due to scaling performed in a code decoding system and improving sound quality.

According to the present invention, the influence of indirect voice and background noise existing in the living room can be extremely reduced by adopting such a configuration, so that it is possible to prevent deterioration of the communication voice sound quality. Also, since the communication voice gain is within a certain range, it is possible to reduce the danger of howling, which makes it impossible to make a call itself, and it is possible to perform very high quality sound control.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram illustrating a basic configuration of a first high-quality loudspeaker information communication system according to the present invention. FIG. 1 shows a conventional signal input terminal 31, a signal output terminal 32, a variable coefficient digital filter 33, a signal input terminal 34, a subtraction circuit 5, a signal output terminal 36, a coefficient correction amount calculation circuit 37, and a signal input as shown in FIG. A device 38 having the same configuration as the acoustic reverberation device 3 employing the adaptive algorithm including the register 38, the pseudo impulse response register 39, and the product-sum operation circuit 310, and a reception signal input terminal 41 as shown in FIG. A reception signal output terminal 42, a digital-analog converter 43, a transmission signal input terminal 44, an analog-digital converter 45, a transmission signal output terminal 46, a speaker 47,
Microphone 48, encoding circuit 49, and decoding circuit 4
An amplitude compression circuit 112 and an amplitude expansion circuit 113 are added to the loudspeaker information communication system 4 composed of 10. A digital signal from the receiving signal input terminal 11, the receiving signal output terminal 12, the transmitting signal input terminal 14, the transmitting signal output terminal 16, and the receiving signal output terminal 12 is converted into an analog signal. A digital-to-analog converter 13 for outputting to a speaker 17, an analog-to-digital converter 15 for converting an analog signal input from a microphone 18 to a digital signal, and inputting the same to a transmission signal input terminal 14, The pseudo impulse response register 3 which receives a reception signal from a reception signal input terminal 11
And a variable coefficient digital filter 33 which is generated from the acoustic reverberation component of the reception signal input to the transmission signal input terminal 14 from the reception signal output terminal 12 via the acoustic reverberation path. The acoustic reverberation removing device 3 in which the coefficient sequence is successively updated by the coefficient correction amount calculating circuit 37 so as to minimize the residual signal obtained by subtracting the pseudo acoustic reverberation obtained, and an encoding circuit for encoding the digital signal 19 and a decoding circuit 110 for decoding a code and reconstructing a digital signal, an amplitude compression circuit 112 for controlling the amplitude of a digital signal input to the coding circuit, By using an amplitude expansion circuit 113 for controlling the amplitude of the digital signal output of the It can be supplied Le signal always high quality public address information communication system, characterized in that to achieve a stable erasing characteristics. FIG. 2 is a block diagram showing a basic configuration of the first high quality loudspeaker information communication system of the present invention. FIG. 2 shows a conventional signal input terminal 31 and signal output terminal 3 as shown in FIG.
2, variable coefficient digital filter 33, signal input terminal 3
4. Acoustic reverberation apparatus 3 employing an adaptive algorithm composed of a subtraction circuit 5, a signal output terminal 36, a coefficient correction amount operation circuit 37, a signal input register 38, a pseudo impulse response register 39, and a product-sum operation circuit 310. And a receiving signal input terminal 4 as shown in FIG.
1. Reception signal output terminal 42, digital-analog converter 43, transmission signal input terminal 44, analog-digital converter 45, transmission signal output terminal 46, speaker 47, microphone 48, encoding circuit 49, and Decoding circuit 41
The configuration is such that an amplitude compression circuit 212 and an amplitude expansion circuit 213 are added to the loudspeaker information communication system 4 composed of 0s. A digital signal from the receiving signal input terminal 21, the receiving signal output terminal 22, the transmitting signal input terminal 24, the transmitting signal output terminal 26, and the receiving signal output terminal 22 is converted into an analog signal. , A digital-analog converter 23 for outputting to a speaker 27, and an analog-to-digital converter for converting an analog signal input from a microphone 28 to a digital signal and inputting it to the transmission signal input terminal 24.
A digital converter 25 and the pseudo impulse response register 39 which receives the reception signal at the reception signal input terminal 21;
And the variable coefficient digital filter 33 which is generated from the acoustic reverberation component of the received signal input from the received signal output terminal 22 to the transmission signal input terminal 24 via the acoustic reverberation path. The acoustic reverberation removing device 3 in which the coefficient sequence is sequentially updated by the coefficient correction amount calculating circuit 37 so as to minimize the residual signal obtained by subtracting the pseudo acoustic reverberation, and a different method for encoding the digital signal. A plurality of encoding circuits 29, a plurality of decoding circuits 210 having different methods of decoding codes and reconstructing digital signals, and a changeover switch 214 capable of arbitrarily selecting the encoding circuit 29 and the decoding circuit 210. In the loudspeaker information communication system 211, the amplitude compression circuit 2 for controlling the amplitude of the digital signal input to the encoding circuit.
12 and the amplitude expansion circuit 213 for controlling the amplitude of the digital signal output from the decoding circuit, the maximum amplitude of which is adapted to each system and changed to generate noise due to scaling performed in each code decoding system. A high-quality loudspeaker information communication system characterized by suppressing sound quality and improving sound quality. As the control value of the amplitude operated by the amplitude compression circuit 212 and the amplitude expansion circuit 213, the value may be stored internally in accordance with a previously adopted encoding method. The coding method described here refers to high-efficiency voice coding such as μ-law and AD-PCM specified by international standards, but other high-performance voice coding. (For example, G.7xx series of ITU-T recommendation). In the second embodiment, a changeover switch is used as an encoding selection method, but it is also possible to perform switching by downloading software at the time of initialization of the apparatus.

[0008]

As described above, according to the present invention,
The following excellent effects are expected.

(1) Since a signal of an appropriate input level is supplied to the acoustic reverberation removing apparatus and the encoding / decoding circuit, deterioration of reverberation elimination characteristics and deterioration of communication voice quality due to clipping noise can be prevented. A large public information communication system can be realized.

(2) Since the input and output signals of the acoustic reverberation device are always kept in the same dynamic range, erroneous detection during double talk is eliminated, and clear full-duplex communication can be realized.

(3) Since the stability of the input / output level can be improved, it is possible to suppress the generation of sound.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration example of a first high-quality loudspeaker information communication system according to the present invention.

FIG. 2 is a block diagram illustrating a configuration example of a second high-quality loudspeaker information communication system according to the present invention.

FIG. 3 is a block diagram illustrating a basic configuration example of an acoustic reverberation removing apparatus according to a conventional technique.

FIG. 4 is a block diagram showing a basic configuration example of a conventional loudspeaker information communication system.

[Explanation of symbols]

11, 21, 41 Reception signal input terminal 12, 22, 42 Reception signal output terminal 13, 23, 43 Digital-analog converter 14, 24, 44 Transmission signal input terminal 15, 25, 45 Analog-digital converter 16, 26, 46 Transmission signal output terminal 17, 27, 47 Speaker 18, 28, 48 Microphone 19, 29, 49 Encoding circuit 110, 210, 410 Decoding circuit 111, 211, 4 Broadcast information communication system 112, 212 Amplitude compression Circuits 113, 213 Amplitude expansion circuit 214 Changeover switch 3 Acoustic echo canceller 31, 34 Signal input terminal 32, 36 Signal output terminal 33 Variable coefficient filter 35 Subtraction circuit 37 Correction amount operation circuit 38 Signal input register 39 Pseudo impulse response register 310 Product Sum operation circuit

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Claims (2)

[Claims] 1. A receiving signal input terminal, a receiving signal output terminal, a transmitting signal input terminal, a transmitting signal output terminal, and converting a digital signal from the receiving signal output terminal into an analog signal, A digital-to-analog converter, an analog-to-digital converter that converts an analog signal input from a microphone into a digital signal, and inputs the signal to the transmission signal input terminal, and a reception signal from the reception signal input terminal. A variable coefficient digital filter having a pseudo impulse response register, and a variable coefficient digital filter generated from an acoustic reverberation component of a reception signal input from the reception signal output terminal to the transmission signal input terminal via an acoustic reverberation path. The coefficient sequence is calculated by a coefficient correction amount operation circuit so as to minimize the residual signal obtained by subtracting the obtained pseudo acoustic echo. In a loudspeaker information communication system using an acoustic reverberation removing apparatus in which is sequentially updated, a coding circuit for coding a digital signal, and a decoding circuit for decoding a code and reconstructing a digital signal, a digital signal to the coding circuit It comprises an amplitude compression circuit for controlling the amplitude of the input, and an amplitude expansion circuit for controlling the amplitude of the digital signal output from the decoding circuit. The digital signal within a constant amplitude can be supplied to the acoustic reverberation apparatus, and is always stable. A high quality loudspeaker information communication system characterized by realizing improved erasure characteristics. 2. An encoding system executed by the encoding circuit,
Unlike the decoding method executed by the decoding circuit, the amplitude compression circuit and the amplitude expansion circuit operate independently, thereby suppressing generation of noise due to scaling performed in each code decoding method and improving sound quality. The high-quality loudspeaker information communication system according to claim 1, wherein the communication system is improved.