Sound signal receiving and decoding method and sound signal decoding method

Abstract

A technique is provided for obtaining a decoded sound signal of high sound quality without significantly increasing the delay time, compared with a structure for obtaining a decoded sound signal of only the minimum sound quality required. In a terminal device connected to a first communication line and a second communication line having a lower priority than the first communication line, a multi-channel sound signal is obtained and output based on a monaural code included in a first code string input from the first communication line and an extension code included in a second code string input from the second communication line whose frame number is closest to the frame number of the monaural code.

Description

Technical Field

[0001] The present invention relates to at least one of a decoding technology for a voice signal in a terminal device connected to at least two communication networks having different information transmission priorities and a corresponding encoding technology for a voice signal. Background Art

[0002] As a prior art for encoding and decoding of audio signals between terminal devices connected to two communication networks with different priorities for information transmission, there is the technology of Patent Document 1. The encoding device of Patent Document 1 performs scalable encoding on the input audio signal for each predetermined time interval, that is, for each frame, to obtain a low frequency code 1 as a base layer code, a low frequency code 2 and a high frequency code as an extension layer code, and includes the low frequency code 1 in a high priority packet and sends it at least to the network B for which the bandwidth is guaranteed, and includes the low frequency code 2 and the high frequency code in a low priority packet and sends it to the network A for which the bandwidth is not guaranteed. The decoding device of Patent Document 1 starts monitoring the elapse of the limit time when receiving a high priority packet, and if the limit time has elapsed, decodes the packet received at that time. That is, since network A usually has a greater delay than network B, the decoding device of patent document 1 essentially performs decoding processing using low-frequency code 2 and high-frequency code after the above-mentioned limit time from the arrival of the base layer code, if low-frequency code 2 and high-frequency code also arrive, to obtain a decoded sound signal with high sound quality. If low-frequency code 2 and high-frequency code do not arrive, decoding processing using only low-frequency code 1 is performed to obtain a decoded sound signal with the minimum required sound quality.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2005-117132 Summary of the invention

[0006] Problems to be solved by the invention

[0007] In the technology of Patent Document 1, in order to obtain decoded sound signals of high sound quality in many frames, it is necessary to set a time much longer than the delay time generated in the structure of obtaining only the decoded sound signals of the required minimum sound quality as the above-mentioned limit time. Therefore, the technology of Patent Document 1 has the following problem, that is, if it is to obtain decoded sound signals of high sound quality in many frames, it is necessary to set the above-mentioned limit time so that the delay time becomes so long that it causes discomfort during two-way communication. In addition, in the technology of Patent Document 1, if the limit time is close to 0 so that there is no discomfort during two-way communication, the proportion of frames in which high-priority packets arrive within the limit time is very small. Therefore, in the technology of Patent Document 1, if the limit time is set so that there is no discomfort during two-way communication, there is a problem that high-quality decoded sound signals cannot be obtained in most frames.

[0008] Therefore, an object of the present invention is to provide a technique for obtaining a decoded audio signal of high sound quality without significantly increasing the delay time, compared with a configuration in which a decoded audio signal of only the minimum required sound quality is obtained.

[0009] Solutions to Solve Problems

[0010] One embodiment of the present invention is a method for receiving and decoding a sound signal performed by a terminal device connected to a first communication line and a second communication line having a lower priority than the first communication line, comprising: a receiving step, for a predetermined frame among multiple frames, outputting a monaural code contained in a first code string input from the first communication line and an extended code whose frame number is closest to the frame number of the monaural code among the extended codes contained in a second code string input from the second communication line; for frames other than the predetermined frame, outputting a monaural code contained in the first code string input from the first communication line and the latest extended code among the extended codes already output; a decoding step, for each frame, obtaining and outputting a decoded digital sound signal of C (C is an integer greater than or equal to 2) channels based on the monaural code output in the receiving step and the extended code output in the receiving step.

[0011] One embodiment of the present invention is a sound signal decoding method performed by a terminal device connected to a first communication line and a second communication line having a lower priority than the first communication line, comprising: a decoding step, for a predetermined frame among multiple frames, based on a monaural code contained in a first code string input from the first communication line and an extended code contained in a second code string input from the second communication line, i.e., an extended code having a frame number closest to the frame number of the monaural code, obtaining and outputting C (C is an integer greater than or equal to 2) channels of decoded digital sound signals; for frames other than the predetermined frame, based on the monaural code contained in the first code string input from the first communication line and the latest extended code used in the predetermined frame, obtaining and outputting C channels of decoded digital sound signals.

[0012] One embodiment of the present invention is a sound signal decoding method performed by a terminal device connected to a first communication line and a second communication line having a lower priority than the first communication line, comprising: a mono decoding step, for each frame, decoding a mono code contained in a first code string input from the first communication line to obtain a mono decoded digital sound signal; and an extended decoding step, for a predetermined frame among a plurality of frames, regarding the mono decoded digital sound signal as a signal of a decoded digital sound signal of C channels (C is an integer greater than or equal to 2) mixed, regarding a characteristic parameter obtained according to the extended code as a difference between channels in the decoded digital sound signal of the C channels. The decoded digital sound signals of C channels are obtained and outputted according to the present invention, wherein the extended code is an extended code included in the second code string input from the second communication line, i.e., an extended code having a frame number closest to the frame number of the mono code included in the first code string input from the first communication line, and for frames other than the predetermined frame, the mono decoded digital sound signal is regarded as a signal mixed with the decoded digital sound signals of C channels, and the latest feature parameter obtained in the predetermined frame is regarded as information representing the characteristics of the difference between the channels in the decoded digital sound signals of C channels, and the decoded digital sound signals of C channels are obtained and outputted.

[0013] Effects of the Invention

[0014] According to the present invention, compared with a configuration in which a decoded audio signal having only the minimum required audio quality is obtained, a decoded audio signal having a high audio quality can be obtained without significantly increasing the delay time. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a block diagram showing an example of a telephone system.

[0016] Figure 2This is a block diagram showing an example of terminal devices corresponding to multiple lines.

[0017] Figure 3 This is a flowchart showing an example of processing by a voice signal transmitting-side device of a plurality of line-compatible terminal devices.

[0018] Figure 4 This is a flowchart showing an example of processing by a voice signal receiving device of a plurality of line-compatible terminal devices.

[0019] Figure 5 This is a diagram schematically showing the temporal relationship between input codes and output signals in a voice signal receiving device of a plurality of line-compatible terminal devices.

[0020] Figure 6 This is a diagram schematically showing the temporal relationship between an input code and an output signal in a sound signal receiving device using the conventional technology.

[0021] Figure 7 This is a block diagram showing an example of a multi-site control device.

[0022] Figure 8 This is a flowchart showing an example of processing of the multi-site control device.

[0023] Fig. 9 This is a block diagram showing an example of a multi-site control device.

[0024] Fig.10 This is a flowchart showing an example of processing of the multi-site control device.

[0025] Fig.11 This is a block diagram showing an example of a telephone line dedicated terminal device.

[0026] Fig.12 This is a flowchart showing an example of processing by the voice signal transmitting-side device of the telephone line dedicated terminal device.

[0027] Fig.13 This is a flowchart showing an example of processing of the voice signal receiving-side device of the telephone line dedicated terminal equipment.

[0028] Fig.14 This is a diagram showing an example of a functional configuration of a computer that implements each device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0029] Telephone System 100

[0030] like Figure 1As shown, the telephone system 100 includes: a plurality of line-compatible terminal devices 200-m (m is an integer greater than or equal to 1 and less than or equal to M, and M is an integer greater than or equal to 2), a first communication network 400, and a second communication network 500. Figure 1 As shown by the dotted line, the telephone system 100 may also include a telephone line dedicated terminal device 300-n (n is an integer greater than 1 and less than N, and N is an integer greater than 1). Each of the plurality of line-compatible terminal devices 200-m can be connected to other terminal devices via each communication line of the first communication network 400, that is, the first communication line 410-m. Furthermore, each of the plurality of line-compatible terminal devices 200-m can be connected to other plurality of line-compatible terminal devices via each communication line of the second communication network 500, that is, the second communication line 510-m. Each of the telephone line dedicated terminal devices 300-n can be connected to other terminal devices via each communication line of the first communication network 400, that is, the first communication line 420-n.

[0031] 《First communication network 400, second communication network 500》

[0032] The first communication network 400 and the second communication network 500 are communication networks with different priorities for information transmission. The first communication network 400 is a communication network with a higher priority for information transmission than the second communication network 500, and is a communication network that can transmit a code string of a specified bit rate from a certain terminal device to another terminal device with a short delay time. The first communication network 400 is, for example, a communication network used in a two-way call between a terminal device such as a conventional portable phone or a smart phone and another terminal device such as a conventional portable phone or a smart phone, and is generally a communication network having a communication line called a telephone line. The second communication network 500 is a communication network with a lower priority for information transmission than the first communication network 400, and is a communication network that can transmit a code string from a certain terminal device to another terminal device without setting a delay time limit. The second communication network 500 is, for example, a communication network used when transmitting data such as an image or a character string from a terminal device such as a smart phone to another terminal device such as a smart phone, and is generally a communication network having a communication line called an Internet line.

[0033] exist Figure 1, the first communication network 400 and the second communication network 500 are recorded separately, but the first communication network 400 and the second communication network 500 do not need to be physically separated, and only need to be logically separated. Similarly, when the terminal device is connected to both the first communication line 410-m and the second communication line 510-m, the first communication line 410-m and the second communication line 510-m do not need to be physically separated, and only need to be logically separated. That is, each terminal device can also be connected to an IP communication network through an IP communication line, and through priority control of packets, the first communication network 400 and the first communication line 410-m as a communication network and communication line with a high priority for information transmission, and the second communication network 500 and the second communication line 510-m as a communication network and communication line with a lower priority for information transmission than the first communication network 400 and the first communication line 410-m. For example, the terminal devices 200-m corresponding to multiple lines may be smartphones corresponding to VoLTE (Voice over LTE, Voice over Long Term Evolution), examples of the first communication network 400 and the first communication line 410-m may be an LTE communication network and a VoLTE communication network and a VoLTE line in the LTE line, and examples of the second communication network 500 and the second communication line 510-m may be an Internet communication network and an Internet line in the LTE communication network and the LTE line.

[0034] In addition, the above-mentioned examples of communication networks, communication lines, and terminal devices are all mobile communication equipment, but there are no restrictions on whether each communication network is a network for fixed communication or a network for mobile communication, whether each communication line is wired or wireless, and whether each terminal device is a fixed telephone or a portable telephone.

[0035] <First embodiment>

[0036] A plurality of line-compatible terminal devices according to the first embodiment will be described.

[0037] 《Multiple lines corresponding to terminal device 200-m》

[0038] The plurality of line-compatible terminal devices 200 - m are, for example, smartphones compatible with VoLTE. Figure 2As shown, the device includes a sound signal transmitting side device 210-m and a sound signal receiving side device 220-m. The sound signal transmitting side device 210-m includes a sound collecting unit 211-m, a coding unit 212-m, and a transmitting unit 213-m. The sound signal receiving side device 220-m includes a receiving unit 221-m, a decoding unit 222-m, and a reproducing unit 223-m. The coding unit 212-m includes a signal analyzing unit 2121-m and a monaural coding unit 2122-m. The decoding unit 222-m includes a monaural decoding unit 2221-m and an extended decoding unit 2222-m. In addition, as shown by the dotted line, the signal analyzing unit 2121-m and the monaural coding unit 2122-m are collectively referred to as a coding unit 2129-m, and the monaural decoding unit 2221-m and the extended decoding unit 2222-m are collectively referred to as a decoding unit 2229-m. In addition, the encoding device 212-m and the decoding device 222-m are sometimes referred to as the sound signal encoding device 212-m and the sound signal decoding device 222-m, respectively. Figure 3 The audio signal receiving side device 220-m of the plurality of line corresponding terminal devices 200-m performs the processing of steps S211 to S213 as shown below. Figure 4 And the processing of steps S221 to S223 illustrated below.

[0039] [Sound signal transmission side device 210-m]

[0040] The sound signal sending side device 210-m obtains a first code string as a code string containing a monaural code corresponding to the digital sound signal of 2 channels for each specified time interval of, for example, 20 ms, that is, for each frame, and outputs it to the first communication line 410-m, and obtains a second code string as a code string containing an extended code corresponding to the digital sound signal of the 2 channels and outputs it to the second communication line 510-m.

[0041] [[Sound pickup unit 211-m]]

[0042] The sound pickup unit 211-m includes two microphones and two AD conversion units. Each microphone is associated with each AD conversion unit one-to-one. The microphone picks up the sound generated in the spatial area around the microphone and converts it into an analog electrical signal, which is output to the AD conversion unit. The AD conversion unit converts the input analog electrical signal into a digital sound signal of a PCM signal with a sampling frequency of 8kHz, for example, and outputs it. That is, the sound pickup unit 211-m outputs the digital sound signals of two channels corresponding to the sound picked up by each of the two microphones, such as the digital sound signals of two-channel stereo of the left channel and the right channel, to the encoding device 212-m (step S211).

[0043] In addition, all or part of the sound pickup unit 211-m may not be provided inside the sound signal transmitting side device 210-m, but may be connected to the sound signal transmitting side device 210-m. For example, the sound pickup unit 211-m of the sound signal transmitting side device 210-m may not have a microphone, but two analog electric signals may be input from the microphone connected to the sound signal transmitting side device 210-m to the AD converter of the sound pickup unit 211-m of the sound signal transmitting side device 210-m. Alternatively, the sound signal transmitting side device 210-m may not have a sound pickup unit 211-m, but two-channel digital sound signals may be input from a sound pickup device such as an AD converter connected to the sound signal transmitting side device 210-m to the encoding device 212-m of the sound signal transmitting side device 210-m.

[0044] [[Encoding device 212-m]]

[0045] The encoding device 212-m receives a two-channel digital audio signal from the sound pickup unit 211-m or a sound pickup device connected to the audio signal transmitting side device 210-m. The encoding device 212-m obtains a monaural code and an extension code corresponding to the input two-channel digital audio signal for each frame, and outputs the monaural code and the extension code to the transmitting unit 213-m (step S212).

[0046] [[[Signal Analysis Unit 2121-m]]]

[0047] The signal analysis unit 2121-m obtains, for each frame, a signal obtained by mixing the two-channel digital sound signals, i.e., a monaural signal, and a spread code representing a characteristic parameter that is a parameter representing a characteristic of a difference between the two-channel digital sound signals and has a small time variation, from the two-channel digital sound signals input. The signal analysis unit 2121-m outputs the obtained monaural signal to the monaural encoding unit 2122-m, and outputs the obtained spread code to the transmitting unit 213-m. The so-called parameter with a small time variation is a parameter with low dependence on time and a parameter with low time resolution.

[0048] [Signal Analysis Unit 2121-m Example 1]

[0049] As a first example, the operation of the signal analysis unit 2121-m in each frame when the information representing the time difference of the digital sound signals of the two channels input is set as a feature parameter is described. The signal analysis unit 2121-m first obtains the feature parameter as the information representing the time difference of the digital sound signals of the two channels input (step S2121-11). The time difference of the digital sound signals of the two channels input can be obtained by any known method. For example, the signal analysis unit 2121-m calculates the correlation value of the sample group of the digital sound signal of one channel (first channel) and the sample group of the digital sound signal of the other channel (second channel) advanced by the candidate sample number for each candidate sample number of the time difference within a predetermined range, and obtains the time difference sample number of the candidate sample number with the largest correlation value as the feature parameter.

[0050] The signal analysis unit 2121-m then obtains any one of the following sequences as a signal obtained by mixing the digital sound signals of the two channels, i.e., a monophonic signal: a sequence based on addition between corresponding samples of a sample group of the digital sound signal of the first channel and a sample group after the time difference represented by the characteristic parameter is assigned to the sample group of the digital sound signal of the second channel; a sequence based on an average value between corresponding samples; and a sequence obtained by deforming these sequences based on addition and average values ​​(step S2121-12). The so-called sample group in which the time difference represented by the characteristic parameter is assigned to the sample group of the digital sound signal of the second channel is, for example, a sample group obtained by advancing the sample group of the digital sound signal of the second channel by the number of samples corresponding to the time difference represented by the characteristic parameter.

[0051] The signal analysis unit 2121-m further obtains an extension code as a code representing the characteristic parameters (step S2121-13). The extension code as a code representing the characteristic parameters can be obtained by a known method. For example, the signal analysis unit 2121-m obtains a code by scalar quantization of the number of time difference samples of the input two-channel digital sound signal, and outputs the obtained code as an extension code. Alternatively, for example, the signal analysis unit 2121-m outputs a binary number representing the number of time difference samples of the input two-channel digital sound signal itself as an extension code.

[0052] [Signal Analysis Unit 2121-m Example 2]

[0053] As a second example, the operation of each frame of the signal analysis unit 2121-m is described when the information representing the degree difference of each frequency band of the input two-channel digital audio signal is set as a feature parameter. In addition, a specific example using complex DFT (Discrete Fourier Transformation) is described below, but a known conversion method to the frequency domain other than complex DFT can also be used.

[0054] The signal analysis unit 2121-m first performs complex DFT on the input two-channel digital sound signal to obtain a complex DFT coefficient string (step S2121-21). The complex DFT coefficient string can also be obtained by using a known method such as a process of applying a window with overlap between frames and a process that takes into account the symmetry of the complex numbers obtained by the complex DFT. For example, if the frame is composed of 128-point samples, it is sufficient to perform complex DFT on a continuous 256-point digital sound signal sample group including the last 64-point samples of the immediately preceding frame and the first 64-point samples of the immediately succeeding frame, and obtain the first half of the 128 complex sequences of the obtained 256 complex sequences as the complex DFT coefficient string. In the following, f is set to integers greater than 1 and less than 128, each complex DFT coefficient of the complex DFT coefficient string of the first channel is set to V1(f), and each complex DFT coefficient of the complex DFT coefficient string of the second channel is set to V2(f). The signal analysis unit 2121-m then obtains a sequence of values ​​of the radius on the complex plane based on each complex DFT coefficient from the complex DFT coefficient string of the two channels (step S2121-22). The value of the radius on the complex plane of each complex DFT coefficient of each channel is equivalent to the intensity of each frequency interval (bin) of the digital sound signal of each channel. Hereinafter, the value of the radius on the complex plane of the complex DFT coefficient V1(f) of the first channel is set to V1r(f), and the value of the radius on the complex plane of the complex DFT coefficient V2(f) of the second channel is set to V2r(f). The signal analysis unit 2121-m then obtains the average value of the ratio of the value of the radius of one channel to the value of the radius of another channel for each frequency band, and obtains a sequence based on the average value as a feature parameter (step S2121-23). ​​The sequence based on the average value is a feature parameter equivalent to information representing the intensity difference of each frequency band of the digital sound signal of the two channels input. For example, if the case is set to 4 frequency bands, the average values ​​of 32 values ​​Mr(1), Mr(2), Mr(3), and Mr(4) obtained by dividing the value of the radius V1r(f) of the first channel by the value of the radius V2r(f) of the second channel for each of the 4 frequency bands f from 1 to 32, 33 to 64, 65 to 96, and 97 to 128 are obtained, and a sequence {Mr(1), Mr(2), Mr(3), Mr(4)} based on the average values ​​is obtained as a feature parameter.

[0055] In addition, the number of frequency bands can be any value less than the number of frequency intervals. As the number of frequency bands, the same value as the number of frequency intervals can be used, or 1 can be used. In the case where the same value as the number of frequency intervals is used as the number of frequency bands, the signal analysis unit 2121-m obtains the value of the ratio of the value of the radius of one channel to the value of the radius of another channel in each frequency interval, and obtains a sequence of values ​​based on the obtained ratio as a feature parameter. In the case where 1 is used as the number of frequency bands, the signal analysis unit 2121-m obtains the value of the ratio of the value of the radius of one channel to the value of the radius of another channel in each frequency interval, and obtains the average value of the obtained ratio over the entire frequency band as a feature parameter. In addition, when the number of frequency bands is set to multiple, the number of frequency intervals contained in each frequency band is arbitrary. For example, the number of frequency intervals contained in a low-frequency band can be less than the number of frequency intervals contained in a high-frequency band.

[0056] In addition, the signal analysis unit 2121-m may use the difference between the value of the radius of one channel and the value of the radius of the other channel instead of the ratio between the value of the radius of one channel and the value of the radius of the other channel. That is, in the above example, instead of the value obtained by dividing the value V1r(f) of the radius of the first channel by the value V2r(f) of the radius of the second channel, the value obtained by subtracting the value V2r(f) of the radius of the second channel from the value V1r(f) of the radius of the first channel may be used.

[0057] The signal analysis unit 2121-m also obtains any one of the following sequences as a monophonic signal of a signal that is a mixture of digital sound signals of two channels: an addition-based sequence between corresponding samples of a sample group of the digital sound signal of the first channel and a sample group of the digital sound signal of the second channel; an average-based sequence between corresponding samples; a sequence obtained by deforming these addition- or average-based sequences (step S2121-24). In addition, the signal analysis unit 2121-m can also obtain the radius average VMr(f) and angle average VMθ(f) of each complex DFT coefficient V1(f) of the complex DFT coefficient string of the first channel and each complex DFT coefficient V2(f) of the complex DFT coefficient string of the second channel obtained in step S2121-21, and perform an inverse complex discrete Fourier transform on a sequence of complex VM(f) with a radius VMr(f) and an angle VMθ(f) on the complex plane to obtain a signal that is a mixture of digital sound signals of two channels, i.e., a monaural signal (step S2121-24').

[0058] The signal analysis unit 2121-m further obtains an extended code as a code representing the characteristic parameters (step S2121-25). The extended code as a code representing the characteristic parameters can be obtained by a known method. For example, the signal analysis unit 2121-m performs vector quantization on the sequence of values ​​obtained in step S2121-23 to obtain a code, and outputs the obtained code as an extended code. Or, for example, the signal analysis unit 2121-m performs scalar quantization on each of the values ​​contained in the sequence of values ​​obtained in step S2121-23 to obtain a code, and outputs the result of merging the obtained codes as an extended code. In addition, when the signal analysis unit 2121-m obtains a single value in step S2121-23, the code obtained by scalar quantization of the single value can be output as an extended code.

[0059] The time difference of the input two-channel digital audio signals described in the first example of the signal analysis unit 2121-m, or the intensity difference of each frequency band of the input two-channel digital audio signals described in the second example of the signal analysis unit 2121-m depends on the position of the sound source. In the case of a general sound source such as a person or a musical instrument, the position of the sound source rarely changes with time. Even if the position of the sound source changes with time, as long as the sound source does not move suddenly, the time difference of the input two-channel digital audio signals or the intensity difference of each frequency band will not change much.

[0060] Therefore, the signal analysis unit 2121-m can also obtain the average or weighted average of the characteristic parameters obtained from the input two-channel digital sound signals of each frame for a plurality of consecutive frames including the frame to be processed as the characteristic parameter, and output the extension code representing the obtained characteristic parameter. The weight used in the weighted average can be set to the maximum value for the frame to be processed, and the smaller the value for the frame farther away from the frame to be processed. In addition, if the characteristic parameters of the frame in the future than the frame to be processed are used, it is necessary to read in advance, and the delay increases, so the signal analysis unit 2121-m can use a plurality of consecutive frames on the past side including the frame to be processed. In addition, of course, when the characteristic parameter contains multiple elements, such as information representing the intensity difference of each of multiple frequency bands, the average or weighted average of the characteristic parameter is a numerical string in which the average value or weighted average value of each element of the characteristic parameter is set as the element.

[0061] In addition, for example, a sample group based on the difference in waveforms of the digital sound signals of the two channels input, that is, the difference between corresponding samples of the digital sound signals of the two channels input, becomes a sample group completely different from the difference in waveforms of the digital sound signals of the two channels input even if the time of each sample is shifted by only one sample, and therefore is information highly dependent on time, has a high time resolution, and has a large time variation. Similarly, the phase difference of the digital sound signals of the two channels input, for example, the difference in the angle on the complex plane of each complex DFT coefficient V1(f) of the complex DFT coefficient string of the first channel obtained in step S2121-21 and the angle on the complex plane of each complex DFT coefficient V2(f) of the complex DFT coefficient string of the second channel, is information highly dependent on time, has a high time resolution, and has a large time variation.

[0062] That is, the characteristic parameter represented by the extended code obtained by the signal analysis unit 2121-m is not a parameter representing information on the waveform of the sound signal emitted by the sound source in the difference between the two channels of digital sound signals, such as the difference in waveform of the two channels of digital sound signals or the phase difference of the two channels of digital sound signals just exemplified above, but a parameter representing information on the relative spatial position of the sound source and the microphone in the difference between the two channels of digital sound signals, such as the time difference between the two channels of digital sound signals represented in the first example of the signal analysis unit 2121-m or the intensity difference in each frequency band of the two channels of digital sound signals represented in the second example of the signal analysis unit 2121-m. In summary, the characteristic parameter represented by the extended code obtained by the signal analysis unit 2121-m is also called a parameter representing the characteristic of the difference between the two channels of digital sound signals input and a parameter with low time resolution, also called a parameter representing the characteristic of the difference between the two channels of digital sound signals input and a parameter with small time variation, also called a parameter representing the characteristic of the difference between the two channels of digital sound signals input and a parameter with low dependence on time, also called a parameter representing the characteristic of the difference between the channels of the two channels of digital sound signals input and a parameter representing information that depends on the relative positions of the sound source and the microphone in space.

[0063] [[[Monaural encoding unit 2122-m]]]

[0064] The monaural coding unit 2122-m encodes the input monaural signal in a predetermined coding method for each frame to obtain a monaural code, and outputs the code to the transmitting unit 213-m. As the coding method, it is necessary to use a coding method in which the bit rate of the monaural code is less than the communication capacity of the first communication line 410-m, for example, a coding method for telephone band speech for mobile phones such as the 13.2 kbps mode of the 3GPP EVS standard (3GPP TS 26.442) can be used.

[0065] That is, the encoding device 212-m obtains, for each frame, a monaural code representing a signal obtained by mixing the digital audio signals of the two channels inputted, and an extended code representing a characteristic parameter of a parameter having a low time resolution and being a characteristic parameter of the difference between the channels of the digital audio signals of the two channels inputted. In addition, as described later, the monaural code obtained by the encoding device 212-m is a code included in the first code string and outputted to the first communication line, and the extended code obtained by the encoding device 212-m is a code included in the second code string and outputted to the second communication line.

[0066] In addition, the encoding device 212-m may use, as the extension code, a code representing the average or weighted average of feature parameters obtained from digital audio signals of two channels of a current frame as the processing target frame and feature parameters obtained from digital audio signals of two channels of a frame past the current frame as the processing target frame.

[0067] [[Transmitting unit 213-m]]

[0068] The transmitting unit 213-m outputs the first code string including the monaural code input from the encoding device 221-m to the first communication channel 410-m and outputs the second code string including the extension code input from the encoding device 221-m to the second communication channel 510-m for each frame (step S213).

[0069] The sending unit 213-m outputs a mono code in a manner that can determine which frame the first code string contains. For example, the sending unit 213-m includes information that can determine the frame, such as the frame number or the time corresponding to the frame, as auxiliary information in the first code string and outputs it. Similarly, the sending unit 213-m outputs an extended code in a manner that can determine which frame the second code string contains. For example, the sending unit 213-m includes information that can determine the frame, such as the frame number or the time corresponding to the frame, as auxiliary information in the second code string and outputs it. In addition, in the sound signal receiving side device 220-m of the first embodiment and subsequent embodiments and modifications, an example is described in which both the first code string and the second code string contain the frame number as auxiliary information.

[0070] [Sound signal receiving device 220-m]

[0071] The audio signal receiving device 220 - m outputs audio based on the monaural code included in the first code string input from the first communication line 410 - m and the spread code included in the second code string input from the second communication line 510 - m, for example, every 20 ms specified time interval, that is, for each frame.

[0072] [[Receiving unit 221-m]]

[0073] The receiving unit 221-m outputs, for each frame, the monaural code included in the first code string input from the first communication line 410-m and the extended code included in the second code string input from the second communication line 510-m, the extended code closest to the frame number of the monaural code, to the decoding device 222-m (step S221).

[0074] The first communication line 410-m is a high priority communication network used for two-way communication, so the first code string including the monaural code is inputted from the first communication line 410-m in the receiving unit 221-m so that the monaural code outputted in the frame number sequence by the encoding device 212-m' of the voice signal transmitting side device 210-m' of the plurality of line corresponding terminal devices 200-m' (m' is an integer not less than 1 and not more than M different from m) at the other end of the call can be outputted in the frame number sequence at the time interval of the frame length (i.e., for example, at a predetermined time interval of 20 ms). In addition, the telephone system 100 is a system for realizing smooth two-way communication, so the receiving unit 221-m wishes to output the code outputted by the encoding device 212-m' of the voice signal transmitting side device 210-m' at the other end of the call to the decoding device 222-m with as little delay as possible. Therefore, the receiving unit 221-m outputs the monaural code included in the first code string output by the sound signal sending side device 210-m' at the other end of the call to the decoding device 222-m in the order of the frame numbers output by the sound signal sending side device 210-m' at the other end of the call at a time interval of the frame length, regardless of whether the second code string including the extended code having the same frame number as that of each monaural code is input to the receiving unit 221-m.

[0075] The second communication line 510-m is a communication network with a low priority, so usually, the second code string of a certain frame output by the voice signal transmission side device 210-m' of the other party is input from the second communication line 510-m to the receiving unit 221-m after the first code string of the frame is input from the first communication line 410-m. That is, at the time when the receiving unit 221-m outputs a mono code to the decoding device 222-m, usually, the second code string including the extension code with the same frame number as the mono code is not input to the receiving unit 221-m, and the extension code with the same frame number as the mono code cannot be output to the decoding device 222-m. In addition, the second communication line 510-m is a communication network with a low priority, so the second code string of each frame output by the voice signal transmission side device 210-m' of the other party does not need to be input from the second communication line 510-m in the order of the frame number. Of course, depending on the status of the second communication network 500, for example, when the second communication network 500 is idle, at the same time as or before the first code string of the frame is input from the first communication line 410-m, the second code string of a frame output from the voice signal transmitting side device 210-m' of the other party of the call can also be input from the second communication line 510-m to the receiving unit 221-m. In other words, sometimes when the receiving unit 221-m outputs a monaural code to the decoding device 222-m, the second code string including the extended code having the same frame number as the monaural code is input to the receiving unit 221-m, so that the extended code having the same frame number as the monaural code can be output to the decoding device 222-m. Therefore, the receiving unit 221-m replaces the spreading code having the same frame number as the frame number of the monaural code output to the decoding device 222-m among the spreading codes included in the second code string input from the second communication line 510-m, and outputs the spreading code having the closest frame number to the frame number of the monaural code output to the decoding device 222-m to the decoding device 222-m. In other words, the receiving unit 221-m outputs the spreading code included in the second code string input from the second communication line 510-m, having the closest frame number to the frame number of the first code string including the monaural code output to the decoding device 222-m, to the decoding device 222-m for each frame.

[0076] Here, the so-called extended code whose frame number is closest to the frame number of the mono code output to the decoding device 222-m among the extended codes included in the second code string input from the second communication line 510-m is, when the extended code included in the second code string input from the second communication line 510-m includes an extended code whose frame number is the same as the frame number of the mono code output to the decoding device 222-m, the extended code included in the second code string input from the second communication line 510-m includes an extended code whose frame number is the same as the frame number of the mono code output to the decoding device 222-m. , when the second code string input from the second communication line 510-m does not include an extension code with the same frame number as the frame number of the monaural code output to the decoding device 222-m, an extension code with a frame number closest to the frame number of the monaural code output to the decoding device 222-m (that is, among the extension codes included in the second code string input from the second communication line 510-m, although the frame number is different from the frame number of the monaural code output to the decoding device 222-m, the extension code with a frame number closest to the frame number of the monaural code output to the decoding device 222-m). This is also the case in the embodiments or modifications described later.

[0077] That is, the receiving unit 221-m outputs, for each frame, an extended code whose frame number is closest to the frame number of the mono code, from among the extended codes included in the first code string input from the first communication line 410-m and the second code string input from the second communication line 510-m. Of course, the receiving unit 221-m outputs the mono code in the order of frame numbers. More specifically, the receiving unit 221-m receives the input of the first code string from the first communication line 410-m and the input of the second code string from the second communication line 510-m, and for each frame, outputs the mono code (that is, the mono code in the order of frame numbers) included in the first code string input from the first communication line 410-m, and, in the case where the extended code included in the second code string input from the second communication line 510-m includes an extended code whose frame number is the same as the frame number of the mono code, outputs the extended code whose frame number is the same as the frame number of the mono code. The same extension code, when the extension codes included in the second code string input from the second communication line 510-m do not include an extension code with the same frame number as the frame number of the mono code, the extension code included in the second code string input from the second communication line is output with a frame number closest to the frame number of the mono code (that is, among the extension codes included in the second code string input from the second communication line, the extension code with a frame number different from the frame number of the mono code but closest to the frame number of the mono code).

[0078] In addition, although it is a well-known technology and will not be described in detail, the receiving unit 221-m has a storage unit (not shown) that accumulates multiple frames of code strings received asynchronously from each communication line due to communication including fluctuation or retransmission control, etc., and although the code strings from each communication line are not necessarily input to the receiving unit 221-m in a predetermined time interval or frame number sequence, the receiving unit 221-m can output any code included in the code string accumulated in the storage unit. That is, the receiving unit 221-m receives and stores the input of the first code string from the first communication line 410-m, stores the inputted first code string, and outputs any stored first code string. In addition, the receiving unit 221-m receives and stores the input of the second code string from the second communication line 510-m, stores the inputted second code string, and outputs any stored second code string. Therefore, the receiving unit 221 - m can extract the monaural code in the order of frame numbers for each predetermined time interval, that is, each frame, or extract the extension code having a frame number closest to the frame number of the monaural code.

[0079] [[Decoding device 222-m]]

[0080] The monaural code and the extension code outputted by the receiving unit 221-m are inputted to the decoding device 222-m for each frame. The decoding device 222-m obtains a decoded digital audio signal of two channels corresponding to the input monaural code and the extension code for each frame, and outputs it to the reproducing unit 223-m (step S222).

[0081] Input to the decoding device 222-m are the monaural codes in the order of frame numbers contained in the first code string input from the first communication line 410-m in the order of frame numbers, and the extension code contained in the second code string input from the second communication line 510-m, i.e., the extension code with the frame number closest to the frame number of each monaural code. That is, the decoding device 222-m obtains and outputs a decoded digital audio signal of two channels for each frame based on the monaural code contained in the first code string input from the first communication line 410-m and the extension code contained in the second code string input from the second communication line 510-m, i.e., the extension code with the frame number closest to the frame number of the monaural code. The monaural codes used by the decoding device 222-m are of course in the order of frame numbers.

[0082] In other words, what is input to the decoding device 222-m is the monaural code in the frame number sequence output by the encoding device 212-m' of the voice signal transmitting side device 210-m' of the other party's call, and the extension code whose frame number is closest to the frame number of the monaural code. That is, the decoding device 222-m obtains a decoded digital audio signal of two channels for each frame from the monaural code in the frame number sequence output by the encoding device 212-m' of the voice signal transmitting side device 210-m' of the other party's call, and the extension code whose frame number is closest to the frame number of the monaural code, and outputs it to the reproducing unit 223-m.

[0083] Here, in the case where the second code string input from the second communication line 510-m includes a frame whose frame number is the same as the frame number of the monaural code included in the first code string input from the first communication line 410-m, the spread code input to the decoding device 222-m is the spread code included in the second code string input from the second communication line 510-m, that is, the spread code having the same frame number as the frame number of the monaural code of the frame; and in the case where the second code string input from the second communication line 510-m does not include a frame whose frame number is the same as the frame number of the monaural code included in the first code string input from the first communication line 410-m, the spread code input to the decoding device 222-m is the spread code included in the second code string input from the second communication line 510-m, that is, the spread code having the frame number closest to the frame number of the monaural code of the frame (that is, the spread code having a frame number different from the frame number of the monaural code of the frame but the frame number closest to the frame number of the monaural code of the frame). This also applies to the embodiments and modifications described later.

[0084] Therefore, for each frame, when the extended code included in the second code string input from the second communication line 510-m includes an extended code having a frame number identical to the frame number of the monaural code (i.e., the monaural code in the frame number sequence) included in the first code string input from the first communication line 410-m, the decoding device 222-m obtains and outputs a decoded digital sound signal of two channels based on the monaural code (i.e., the monaural code in the frame number sequence) included in the first code string input from the first communication line 410-m and the extended code having a frame number identical to the frame number of the monaural code, and the extended code included in the second code string input from the second communication line 510-m. In the case where the code string does not contain an extension code having the same frame number as the monaural code contained in the first code string input from the first communication line 410-m (i.e., the monaural code in frame number sequence), a decoded digital sound signal of two channels is obtained and output based on the monaural code contained in the first code string input from the first communication line 410-m (i.e., the monaural code in frame number sequence) and the extension code contained in the second code string input from the second communication line 510-m, i.e., the extension code having a frame number closest to the frame number of the monaural code (i.e., the extension code having a frame number that is different from the frame number of the monaural code but is closest to the frame number of the monaural code).

[0085] [[[Monaural decoding unit 2221-m]]]

[0086] The monaural code input to the decoding device 222-m for each frame is input to the monaural decoding unit 2221-m. The monaural decoding unit 2221-m decodes the input monaural code for each frame using a predetermined decoding method to obtain a monaural decoded digital audio signal, and outputs it to the extended decoding unit 2222-m. As the predetermined decoding method, a decoding method corresponding to the encoding method used by the monaural encoding unit 2122-m' of the encoding device 212-m' of the audio signal transmitting side device 210-m' at the other end of the call is used.

[0087] The monaural code in the frame number order output by the coding device 212-m' of the audio signal transmitting side device 210-m' of the other party's call is input to the monaural decoding unit 2221-m. That is, the monaural decoding unit 2221-m obtains the monaural decoded digital audio signal in the frame number order encoded by the coding device 212-m' of the audio signal transmitting side device 210-m' of the other party's call for each frame, and outputs it to the extended decoding unit 2222-m.

[0088] [[[Extended decoding unit 2222-m]]]

[0089] For each frame, the monaural decoded digital audio signal outputted by the monaural decoder 2221-m and the extension code inputted to the decoding device 222-m are inputted to the extension decoder 2222-m. The extension decoder 2222-m obtains a two-channel decoded digital audio signal from the input monaural decoded digital audio signal and the extension code for each frame and outputs the decoded digital audio signal to the reproducing unit 223-m.

[0090] The mono decoded digital audio signal input to the extension decoding unit 2222-m is the frame number sequence encoded by the encoding device 212-m' of the audio signal transmitting side device 210-m' of the other party's call, and the extension code input to the decoding device 222-m is the extension code with the frame number closest to the frame number of the mono decoded digital audio signal. That is, the extension decoding unit 2222-m obtains the two-channel decoded digital audio signal for each frame from the mono decoded digital audio signal in the frame number sequence output by the encoding device 212-m' of the audio signal transmitting side device 210-m' of the other party's call, and the extension code with the frame number closest to the frame number of the mono decoded digital audio signal, and outputs it to the reproducing unit 223-m. In addition, the extension code is a code indicating a characteristic parameter obtained by the encoding device 212-m' of the voice signal transmitting side device 210-m' of the multiple line corresponding terminal device 200-m' at the other end of the call, and indicates a parameter for indicating the characteristic of the difference between the two-channel digital voice signals. That is, the extension decoding unit 2222-m regards the input mono decoded digital voice signal as a signal obtained by mixing the two-channel decoded digital voice signals for each frame, and regards the characteristic parameter obtained from the extension code as information indicating the characteristic of the difference between the two-channel digital voice signals, obtains the two-channel decoded digital voice signals and outputs them to the reproducing unit 223-m.

[0091] [First example of the extended decoding unit 2222-m]

[0092] As a first example, the operation of each frame of the extension decoding unit 2222-m when the characteristic parameter is information indicating the time difference of the digital audio signals of two channels will be described. The extension decoding unit 2222-m first obtains information indicating the time difference as a characteristic parameter indicated by the extension code from the input extension code (step S2222-11). The signal analysis unit 2121-m' of the encoding device 212-m' of the audio signal transmitting side device 210-m' of the other party of the call of the extension decoding unit 2222-m obtains the characteristic parameter from the extension code in a manner corresponding to the manner in which the extension code is obtained from the characteristic parameter. The information indicating the time difference as the characteristic parameter is, for example, the number of time difference samples. For example, the extension decoding unit 2222-m performs scalar decoding on the input extension code and obtains a scalar value corresponding to the input extension code as the number of time difference samples. Alternatively, for example, the extension decoding unit 2222-m assumes that the input extension code is a binary number value and obtains a decimal number corresponding to the binary number as the number of time difference samples.

[0093] The extended decoding unit 2222-m then regards the input mono decoded digital audio signal and the characteristic parameter obtained in step S2222-11 as a signal in which two decoded digital audio signals are mixed, and regards the characteristic parameter as information indicating the time difference between the two decoded digital audio signals, and obtains and outputs two decoded digital audio signals (step S2222-12). More specifically, the extended decoding unit 2222-m obtains any one of the following sequences as the digital audio signal of the first channel: the sample group of the input mono digital audio signal itself, the sequence of values ​​obtained by dividing the values ​​of each sample of the sample group of the input mono digital audio signal by 2, and the sequence obtained by deforming any one of these sample groups (step S2222-121). The extended decoding unit 2222-m further obtains a sample group obtained by delaying the digital audio signal of the first channel by the number of samples of the time difference indicated by the characteristic parameter, and outputs it as the sample group of the digital audio signal of the second channel (step S2222-122).

[0094] [Second example of the extended decoding unit 2222-m]

[0095] As a second example, the operation of each frame of the extension decoding unit 2222-m when the characteristic parameter is information indicating the intensity difference of each frequency band of the digital audio signal of two channels will be described. The extension decoding unit 2222-m first decodes the input extension code to obtain information indicating the intensity difference of each frequency band (step S2222-21). The extension decoding unit 2222-m obtains the characteristic parameter from the extension code in a manner corresponding to the manner in which the signal analysis unit 2121-m' of the encoding device 212-m' of the audio signal transmitting side device 210-m' at the other end of the call obtains the extension code from the information indicating the intensity difference of each frequency band. For example, the extension decoding unit 2222-m performs vector decoding on the input extension code to obtain the value of each element of the vector corresponding to the input extension code as information indicating a plurality of intensity differences indicating each frequency band. Alternatively, for example, the extension decoding unit 2222-m performs scalar decoding on each of the codes included in the input extension code to obtain information indicating the intensity difference of each frequency band. When the number of frequency bands is 1, the extension decoding unit 2222 - m performs scalar decoding on the input extension code to obtain information indicating the intensity difference of one frequency band, that is, all frequency bands.

[0096] The extended decoding unit 2222-m then regards the input mono decoded digital audio signal as a signal obtained by mixing two decoded digital audio signals and the characteristic parameter obtained in step S2222-21, and regards the characteristic parameter as information indicating the difference in intensity of each frequency band of the two decoded digital audio signals, and obtains and outputs two decoded digital audio signals (step S2222-22). If the signal analysis unit 2121-m' of the encoding device 212-m' of the audio signal transmitting side device 210-m' of the other end of the call performs the above-mentioned specific example operation using complex DFT, the extended decoding unit 2222-m performs the following operation.

[0097] The extended decoding unit 2222-m first performs complex DFT on the input mono decoded digital sound signal to obtain a complex DFT coefficient string (step S2222-221). Thereafter, the extended decoding unit 2222-m sets each complex DFT coefficient of the obtained mono complex DFT coefficient string to MQ(f). The extended decoding unit 2222-m then obtains the value of the radius MQr(f) on the complex plane of each complex DFT coefficient and the value of the angle MQθ(f) on the complex plane of each complex DFT coefficient from the mono complex DFT coefficient string (step S2222-222). The extended decoding unit 2222-m then obtains the value of each radius MQr(f) multiplied by the square root of the corresponding value in the characteristic parameter as the value VLQr(f) of each radius of the first channel, and obtains the value of each radius MQr(f) divided by the square root of the corresponding value in the characteristic parameter as the value VRQr(f) of each radius of the second channel (step S2222-223). For the corresponding value in the characteristic parameter of each frequency interval, if it is the example of the above-mentioned four frequency bands, f from 1 to 32 is Mr(1), f from 33 to 64 is Mr(2), f from 65 to 96 is Mr(3), and f from 97 to 128 is Mr(4). In addition, when the signal analysis unit 2121-m' of the encoding device 212-m' of the sound signal sending side device 210-m' on the other end of the call uses the difference between the value of the radius of the first channel and the value of the radius of the second channel instead of the ratio between the value of the radius of the first channel and the value of the radius of the second channel, the extended decoding unit 2222-m may obtain a value obtained by adding a value obtained by dividing the corresponding value in the characteristic parameter by 2 to the value MQr(f) of each radius as the value VLQr(f) of each radius of the first channel, and obtain a value obtained by subtracting a value obtained by dividing the corresponding value in the characteristic parameter by 2 from the value MQr(f) of each radius as the value VRQr(f) of each radius of the second channel. The extended decoding unit 2222-m then performs an inverse complex discrete Fourier transform on a complex sequence based on a radius of VLQr(f) and an angle of MQθ(f) on the complex plane to obtain and output a decoded digital sound signal of the first channel, and performs an inverse complex discrete Fourier transform on a complex sequence based on a radius of VRQr(f) and an angle of MQθ(f) on the complex plane to obtain and output a decoded digital sound signal of the second channel (steps S2222-224).

[0098] [[Regeneration Unit 223-m]]

[0099] The reproduction unit 223 - m outputs audio corresponding to the input two-channel decoded digital audio signal (step S223 ).

[0100] The regeneration unit 223-m includes, for example, two DA converters and two speakers. The DA converter converts the input decoded digital sound signal into an analog electrical signal and outputs it. The speaker generates a sound corresponding to the analog electrical signal input from the DA converter. The speaker may also be a speaker provided in a stereo headset or a stereo earphone. In this case, for example, the regeneration unit 223-m makes the DA converter and the speaker correspond one-to-one, and generates sounds (decoded sound signals) corresponding to the two decoded digital sound signals respectively from the two speakers.

[0101] In addition, all or part of the regeneration unit 223-m may not be provided inside the sound signal receiving side device 220-m, but may be connected to the sound signal receiving side device 220-m. For example, the regeneration unit 223-m of the sound signal receiving side device 220-m may not have a speaker, but may output two analog electrical signals obtained by the DA conversion unit of the regeneration unit 223-m of the sound signal receiving side device 220-m to the speaker connected to the sound signal receiving side device 220-m. Alternatively, the sound signal receiving side device 220-m may not have the regeneration unit 223-m, but the decoding device 222-m of the sound signal receiving side device 220-m may output two-channel decoded digital sound signals to a regeneration device such as a DA converter connected to the sound signal receiving side device 220-m.

[0102] [Operation Example of the Sound Signal Receiving Device 220-m]

[0103] Figure 5 This diagram schematically shows the temporal relationship between a monaural code included in a first code string input from a first communication line 410-m to a sound signal receiving side device 220-m, an extended code included in a second code string input from a second communication line 510-m to a sound signal receiving side device 220-m, and a decoded sound signal output from the sound signal receiving side device 220-m, by removing processing delays that depend on the processing capabilities of the device. Figure 5 The horizontal axis is the time axis. The number i in the brackets is the frame number in the encoding device 212-m' of the sound signal sending side device 210-m' of the multiple line corresponding terminal device 200-m' at the other end of the call. CM(i) is the monaural code included in the first code string input from the first communication line 410-m to the sound signal receiving side device 220-m. CE(i) is the extension code included in the second code string input from the second communication line 510-m to the sound signal receiving side device 220-m. YS'(i) is the decoded sound signal output by the sound signal receiving side device 220-m. Figure 5Yes, in the sound signal receiving side device 220-m, the second code string is input in frame number order from the second communication line 510-m which is a communication network with a low priority, but the second code string is input 5 frames later than the first code string in frame number order from the first communication line 410-m which is a communication network with a high priority.

[0104] When receiving the first code string including the monaural code CM(6) of frame number 6 from the first communication line 410-m, the receiving unit 221-m outputs the monaural code CM(6) included in the first code string input from the first communication line 410-m and the extended code CE(1) included in the second code string having the frame number closest to the frame number of the monaural code CM(6) among the second code strings input from the second communication line 510-m to the decoding unit 222-m. When the monaural code CM(6) and the extended code CE(1) are input, the decoding unit 222-m obtains decoded digital audio signals of two channels corresponding to the input monaural code CM(6) and the extended code CE(1) and outputs the decoded digital audio signals to the reproducing unit 223-m. The regenerator 223-m starts outputting the decoded audio signal YS'(6) of the two channels corresponding to the input two decoded digital audio signals from the moment when the decoded digital audio signals of the two channels corresponding to the monaural code CM(6) and the extension code CE(1) are inputted. Thus, when the receiver 221-m finishes receiving the first code string including the monaural code CM(6) of the frame number 6 from the first communication line 410-m, the audio signal receiving side device 220-m can obtain the decoded audio signal YS'(6) of the two channels based on the monaural code CM(6) of the frame number 6 and the extension code CE(1) included in the second code string having the closest frame number, and start outputting it.

[0105] Similarly, when the receiving unit 221-m finishes receiving the first code string including the monaural code CM(7) of frame number 7 from the first communication line 410-m, the sound signal receiving side device 220-m obtains the decoded sound signal YS'(7) of the two channels based on the monaural code CM(7) of frame number 7 and the extension code CE(2) included in the second code string closest to the frame number, and starts outputting it. When the receiving unit 221-m finishes receiving the first code string including the monaural code CM(8) of frame number 8 from the first communication line 410-m, the sound signal receiving side device 220-m obtains the decoded sound signal YS'(8) of the two channels based on the monaural code CM(8) of frame number 8 and the extension code CE(3) included in the second code string closest to the frame number, and starts outputting it, and so on.

[0106] Figure 6This diagram schematically shows the temporal relationship between a monaural code included in a first code string input from a first communication line 410-m to a sound signal receiving side device, an extended code included in a second code string input from a second communication line 510-m to a sound signal receiving side device 220-m, and a decoded sound signal output by the sound signal receiving side device when the technology of Patent Document 1 is used, by removing processing delays that depend on the processing capabilities of the device. Figure 6 The horizontal axis, the number i in the brackets, CM(i), CE(i) and Figure 5 YS(i) is a decoded audio signal output by the audio signal receiving device using the technology of Patent Document 1. Figure 6 also with Figure 5 Similarly, in the sound signal receiving side device, a second code string is input in frame number order from the second communication line 510-m, which is a communication network with a low priority, but the second code string is input 5 frames later than the first code string in frame number order from the first communication line 410-m, which is a communication network with a high priority. Figure 6 This is an example in which the audio signal receiving device using the technology of Patent Document 1 conveys that the above-mentioned limit time is a time equivalent to five frames.

[0107] The sound signal receiving side device using the technology of patent document 1 obtains the decoded sound signal YS(6) of two channels corresponding to the monaural code CM(6) input from the first communication line 410-m and the extended code CE(6) input from the second communication line 510-m at the time limit of exactly 5 frames from the input of the monaural code CM(6), and starts to output it. Similarly, the sound signal receiving side device using the technology of patent document 1 obtains a decoded sound signal YS(7) of two channels based on the monaural code CM(7) of frame number 7 and the extended code CE(7) of frame number 7 input from the second communication line 510-m at the moment when five frames have passed since the end of receiving the monaural code CM(7) from the first communication line 410-m, and starts outputting it; obtains a decoded sound signal YS(8) of two channels based on the monaural code CM(8) of frame number 8 and the extended code CE(8) of frame number 8 input from the second communication line 510-m at the moment when five frames have passed since the end of receiving the monaural code CM(8) from the first communication line 410-m, and starts outputting it, and so on.

[0108] 〔Effect〕

[0109] from Figure 6 and Figure 5It can be seen that in the technology of patent document 1, in order to obtain a decoded sound signal with high sound quality, a delay of 5 frames is caused compared with the case of obtaining a decoded sound signal with minimum sound quality. However, in the technology of the first embodiment, the delay time is not significantly increased compared with the case of obtaining a decoded sound signal with minimum sound quality. That is, a decoded sound signal with high sound quality can be obtained with a delay time that does not cause discomfort during two-way conversation.

[0110] <Second embodiment>

[0111] In the first embodiment, a spreading code is obtained and output for each frame, but a spreading code may be obtained and output only once in a plurality of frames. This method will be described as a second embodiment.

[0112] The second embodiment differs from the first embodiment in the operations of the signal analysis unit 2121 - m and the transmission unit 213 - m of the encoding device 212 - m of the audio signal transmission side device 210 - m. The differences between the second embodiment and the first embodiment will be described below.

[0113] [[[Signal Analysis Unit 2121-m]]]

[0114] Similar to the signal analysis unit 2121-m of the first embodiment, the signal analysis unit 2121-m obtains and outputs, for each frame, a signal obtained by mixing the two-channel digital sound signals inputted, i.e., a monaural signal, from the two-channel digital sound signals inputted. However, unlike the signal analysis unit 2121-m of the first embodiment, the signal analysis unit 2121-m obtains and outputs an extended code representing a characteristic parameter only for a predetermined frame among a plurality of frames, wherein the characteristic parameter is a parameter representing a characteristic of the difference between the two-channel digital sound signals inputted and has a small time variation.

[0115] For example, the signal analysis unit 2121-m obtains characteristic parameters from the input two-channel digital sound signal for a frame with an odd frame number, obtains and outputs an extension code representing the characteristic parameters, but does not obtain characteristic parameters for a frame with an even frame number, and does not obtain or output an extension code representing the characteristic parameters. In addition, when the signal analysis unit 2121-m adopts a structure that uses characteristic parameters when obtaining a monaural signal, the signal analysis unit 2121-m obtains a monaural signal for a frame for which no characteristic parameters are obtained, using the input two-channel digital sound signal of the frame and the characteristic parameters corresponding to the latest extension code among the extension codes that have been output.

[0116] Alternatively, for example, the signal analysis unit 2121-m obtains characteristic parameters from the input two-channel digital sound signals for frames with odd frame numbers, but does not obtain and output an extension code representing the characteristic parameters, and obtains and outputs characteristic parameters from the input two-channel digital sound signals for frames with even frame numbers, and obtains and outputs an extension code representing the average or weighted average of the characteristic parameters of the immediately preceding frame that was not output without obtaining the extension code representing the characteristic parameters and the characteristic parameters of the frame. The weight used in the weighted average may be a value in which the weight of the frame is greater than the weight of the immediately preceding frame.

[0117] The above two examples are structures for obtaining and outputting a spreading code once in two frames, but a spreading code may be obtained and output once in three or more frames, or a spreading code may be obtained and output for a predetermined frame among a plurality of frames.

[0118] That is, the encoding device 212-m of the second embodiment obtains, for each frame, a monaural code representing a signal obtained by mixing the digital sound signals of the two channels to be input, and, for a predetermined frame among a plurality of frames, obtains an extended code representing a characteristic parameter which is a parameter representing a characteristic difference between the channels of the digital sound signals of the two channels to be input and which is a parameter having a low time resolution.

[0119] Alternatively, the encoding device 212-m of the second embodiment obtains, for each frame, a monaural code representing a signal obtained by mixing the input two-channel digital sound signals, obtains, for each frame, a characteristic parameter which is a parameter representing the characteristic difference between the channels of the input two-channel digital sound signals and is a parameter with low time resolution, and obtains, for a predetermined frame among a plurality of frames, a spread code representing the average or weighted average of the characteristic parameters obtained in each frame after the immediately preceding predetermined frame. The weight used in the weighted average is set to the maximum value for the frame, and the smaller the value is for the frame farther from the frame.

[0120] As described later, the monaural code obtained by the encoding device 212 - m is a code included in the first code string and outputted on the first communication channel, and the spread code obtained by the encoding device 212 - m is a code included in the second code string and outputted on the second communication channel.

[0121] [[Transmitting unit 213-m]]

[0122] The sending unit 213-m is similar to the sending unit 213-m of the first embodiment. For each frame, the code string including the input monaural code, i.e., the first code string, is output on the first communication line 410-m. However, unlike the sending unit 213 of the first embodiment, the code string including the input extended code, i.e., the second code string, is output on the second communication line 510-m only for the frame to which the extended code is input, i.e., only for the predetermined frame among the multiple frames.

[0123] 〔Effect〕

[0124] As described in the first embodiment, the spreading code used in the sound signal receiving side device 220-m is the spreading code whose frame number is closest to the frame number of the monaural code, so it is not necessary for the spreading code whose frame number is the same as the frame number of the monaural code to be input to the sound signal receiving side device 220-m. In addition, the original characteristic parameter is a parameter with a small change in time. Therefore, according to this embodiment, by adopting a structure in which the spreading code is obtained and output only once for multiple frames, the amount of calculation processing of the signal analysis unit 2121-m can be reduced compared with the first embodiment without significantly deteriorating the quality of the decoded sound signal, and the amount of code used to transmit the characteristic parameter can be reduced compared with the first embodiment.

[0125] <Third embodiment>

[0126] In the first embodiment, the audio signal receiving device 220 - m obtains the spreading code for decoding in each frame, but the audio signal receiving device 220 - m may obtain the spreading code for decoding only once in a plurality of frames. This mode will be described as a third embodiment.

[0127] The audio signal receiving device 220 - m of the third embodiment differs from the audio signal receiving device 220 - m of the first embodiment in the operations of the receiving unit 221 - m and the extension decoding unit 2222 - m of the decoding device 222 - m. The differences between the third embodiment and the first embodiment will be described below.

[0128] [[Receiving unit 221-m]]

[0129] The receiving unit 221-m outputs the monaural code included in the first code string input from the first communication line 410-m to the decoding device 222-m for each frame, similarly to the receiving unit 221-m of the first embodiment. However, unlike the receiving unit 221-m of the first embodiment, the receiving unit 221-m obtains and outputs the extension code whose frame number is closest to the frame number of the monaural code in the extension code included in the input second code string only for a predetermined frame among the plurality of frames. That is, more specifically, the receiving unit 221-m obtains and outputs the extension code whose frame number is closest to the frame number of the monaural code in the extension code included in the input second code string only for a predetermined frame among the plurality of frames.

[0130] [[[Extended decoding unit 2222-m]]]

[0131] Similar to the extension decoding unit 2222-m of the first embodiment, the monaural decoded digital audio signal outputted from the monaural decoding unit 2221-m is inputted to the extension decoding unit 2222-m for each frame, but unlike the extension decoding unit 2222-m of the first embodiment, the extension code is inputted only for a predetermined frame among the plurality of frames. Similar to the extension decoding unit 2222-m of the first embodiment, the extension decoding unit 2222-m obtains and outputs a two-channel decoded digital audio signal based on the input monaural decoded digital audio signal and the extension code for the predetermined frame among the plurality of frames, i.e., the frame to which the extension code is also inputted, and, unlike the extension decoding unit 2222-m of the first embodiment, obtains and outputs a two-channel decoded digital audio signal based on the input monaural decoded digital audio signal and the latest extension code among the input extension codes for the frames other than the predetermined frame among the plurality of frames, i.e., the frames to which the extension code is not inputted.

[0132] That is, the decoding device 222-m obtains and outputs a decoded digital sound signal of two channels for a predetermined frame among multiple frames based on the monaural code included in the first code string input from the first communication line 410-m and the extended code whose frame number is closest to the frame number of the monaural code included in the second code string input from the second communication line 510-m, and obtains and outputs a decoded digital sound signal of two channels for frames other than the predetermined frame based on the monaural code included in the first code string input from the first communication line 410-m and the latest extended code used in the predetermined frame. Specifically, the decoding device 222-m obtains and outputs a decoded digital sound signal of two channels based on the monaural code (i.e., the monaural code in the sequence of frame numbers) contained in the first code string input from the first communication line 410-m and the extended code with the same frame number as the frame number of the monaural code, when the extended code contained in the second code string input from the second communication line 510-m includes an extended code having the same frame number as the monaural code (i.e., the monaural code in the sequence of frame numbers) contained in the first code string input from the first communication line 410-m, and when the extended code contained in the second code string input from the second communication line 510-m does not include an extended code having the same frame number as the monaural code (i.e., the monaural code in the sequence of frame numbers) contained in the first code string input from the first communication line 410-m. In the case of a spreading code with the same frame number as the mono channel code (i.e., the mono code in the order of frame numbers) contained in the first code string input from the first communication line 410-m, a decoding digital sound signal of two channels is obtained and output based on the monaural code contained in the first code string input from the first communication line 410-m (i.e., the monaural code in the order of frame numbers) and the spreading code whose frame number is closest to the frame number of the monaural code as the spreading code contained in the second code string input from the second communication line 510-m (i.e., the spreading code whose frame number is different from the frame number of the monaural code but is closest to the frame number of the monaural code), and for frames other than the predetermined frames, a decoding digital sound signal of two channels is obtained and output based on the monaural code contained in the first code string input from the first communication line 410-m (i.e., the monaural code in the order of frame numbers) and the latest spreading code used in the predetermined frame.

[0133] More specifically, the monaural decoding unit 2221-m of the decoding device 222-m decodes the monaural code included in the first code string input from the first communication line 410-m for each frame to obtain a monaural decoded digital audio signal, and the extended decoding unit 2222-m of the decoding device 222-m regards the monaural decoded digital audio signal as a signal in which the two-channel decoded digital audio signals are mixed for a predetermined frame among the plurality of frames, and regards the feature parameter obtained based on the extended code, which is the extended code included in the second code string input from the second communication line 510-m and has a frame number closest to the frame number of the monaural code included in the first code string input from the first communication line 410-m, as information indicating the feature of the difference between the channels in the two-channel decoded digital audio signal, and obtains and outputs the two-channel decoded digital audio signal. In addition, the extended decoding unit 2222-m uses the feature parameter obtained based on the extended code in the predetermined frame, so that the feature parameter can be stored and used in frames other than the predetermined frame. That is, in frames other than predetermined frames, the extended decoding unit 2222-m regards the decoded digital sound signal of a mono channel as a signal obtained by mixing the decoded digital sound signals of two channels, regards the latest feature parameters obtained in the predetermined frame as information representing the features of the difference between the channels in the decoded digital sound signal of the two channels, and obtains and outputs the decoded digital sound signal of the two channels.

[0134] That is, the mono decoding unit 2221-m of the decoding device 222-m decodes the mono code (i.e., the mono code in the order of frame numbers) contained in the first code string input from the first communication line 410-m for each frame to obtain a mono decoded digital sound signal, and the extended decoding unit 2222-m of the decoding device 222-m regards a predetermined frame among the plurality of frames as a mono code contained in the extended code contained in the second code string input from the second communication line 510-m and the mono code contained in the first code string input from the first communication line 410-m. In the case of an extended code having the same frame number as the frame number of the channel code (i.e., a mono code in the order of frame numbers), the mono decoded digital sound signal is a signal in which the decoded digital sound signals of the two channels are mixed, and the characteristic parameter obtained based on the extended code having the same frame number as the frame number of the mono code is regarded as information indicating the characteristics of the difference between the channels in the decoded digital sound signals of the two channels, and the decoded digital sound signals of the two channels are obtained and output, and the extended code included in the second code string input from the second communication line 510-m does not include the frame number and the frame number from the first communication line 41 In the case where the frame number of the mono code (i.e., the mono code in the frame number order) included in the first code string input from 0-m is the same as the extended code, the mono decoded digital sound signal is regarded as a signal in which the two-channel decoded digital sound signals are mixed, and is regarded as an extended code according to the frame number of the extended code included in the second code string input from the second communication line 510-m and the frame number of the mono code included in the first code string input from the first communication line 410-m being closest (i.e., the frame number is different from the frame number of the mono code, but the frame number is the same as the frame number of the mono code). The characteristic parameter obtained by using the extended code (the frame number closest to the channel code) is information representing the characteristics of the difference between the channels in the decoded digital sound signal of the two channels, the decoded digital sound signal of the two channels is obtained and output, and it is regarded that in the frame other than the predetermined frame, the mono decoded digital sound signal is a signal mixed with the decoded digital sound signals of the two channels, and the latest characteristic parameter obtained in the predetermined frame is information representing the characteristics of the difference between the channels in the decoded digital sound signal of the two channels, and the decoded digital sound signal of the two channels is obtained and output.

[0135] <Modification of the Third Embodiment>

[0136] In addition, the third embodiment may be replaced, and the extended decoding unit 2222-m performs the same operation as the first embodiment, and the receiving unit 221-m outputs, for a predetermined frame among multiple frames, the mono code contained in the first code string input from the first communication line 410-m and the extended code contained in the second code string input from the second communication line 510-m, the frame number of which is closest to the frame number of the mono code, and for frames other than the predetermined frame among the multiple frames, the mono code contained in the first code string input from the first communication line 410-m and the latest extended code among the extended codes that have been output are output.

[0137] More specifically, the receiving unit 221-m outputs, for a predetermined frame among a plurality of frames, the monaural code and the monaural code having the same frame number as the monaural code contained in the first code string input from the first communication line 410-m, when the extended code contained in the second code string input from the second communication line 510-m includes an extended code having the same frame number as the monaural code contained in the first code string input from the first communication line 410-m (i.e., the monaural code in the frame number sequence), and outputs, when the extended code contained in the second code string input from the second communication line 510-m does not include an extended code having the same frame number as the monaural code contained in the first code string input from the first communication line 410-m (i.e., the monaural code in the frame number sequence), the monaural code contained in the first code string input from the first communication line 410-m. The mono code contained in the first code string input from the communication line 410-m (i.e., the mono code in the order of frame numbers) and the extended code whose frame number is closest to the frame number of the mono code among the extended codes contained in the second code string input from the second communication line 510-m (i.e., the extended code whose frame number is different from the frame number of the mono code but is closest to the frame number of the mono code among the extended codes contained in the second code string input from the second communication line 510-m), for frames other than predetermined frames among the multiple frames, the mono code contained in the first code string input from the first communication line 410-m (the mono code in the order of frame numbers) and the latest extended code among the extended codes that have been output are output.

[0138] 〔Effect〕

[0139] As described in the first embodiment, the extension code used in the sound signal receiving side device 220-m is the extension code whose frame number is closest to the frame number of the monaural code, so it is not necessary for the extension code whose frame number is the same as the frame number of the monaural code to be input to the extension decoding unit 2222-m. In addition, the original characteristic parameter is a parameter with a small change in time. Therefore, according to this embodiment and its modified example, by adopting a structure in which the extension code is obtained only once in multiple frames, the amount of calculation processing of the receiving unit 221-m or the amount of information output can be reduced compared with the first embodiment without significantly deteriorating the quality of the decoded sound signal.

[0140] <Fourth embodiment>

[0141] The characteristic parameters used by the sound signal receiving device 220-m in the first embodiment when obtaining two decoded digital sound signals may be characteristic parameters represented by the spreading code input in the processing target frame or an average or weighted average of characteristic parameters of past frames. This method will be described as a fourth embodiment.

[0142] The fourth embodiment differs from the first embodiment in the operation of the extended decoding unit 2222-m of the decoding device 222-m of the sound signal receiving side device 220-m. The difference between the fourth embodiment and the first embodiment is described below. In the following, the extended decoding unit 2222-m that processes each frame refers to the frame that is the processing object at that moment as the current frame, and the frame that is more than the past as the past frame.

[0143] [[[Extended decoding unit 2222-m]]]

[0144] Similar to the extended decoding unit 2222-m of the first embodiment, for each frame, the mono decoded digital audio signal output by the mono decoding unit 2221-m and the extended code input to the decoding device 222-m are input to the extended decoding unit 2222-m. The extended decoding unit 2222-m has a storage unit (not shown). The storage unit stores the feature parameters obtained by the extended decoding unit 2222-m in the past frame. For each frame, the extended decoding unit 2222-m obtains a two-channel decoded digital audio signal from the input mono decoded digital audio signal, the input extended code, and the feature parameters of the past frame stored in the storage unit, and outputs it to the reproducing unit 223-m. Specifically, the extended decoding unit 2222-m performs the following steps S2222-31 to S2222-35 for each frame.

[0145] The extended decoding unit 2222-m first obtains the characteristic parameters represented by the input extended code from the extended code (step S2222-31), and stores the obtained characteristic parameters in the storage unit (step S2222-32). The extended decoding unit 2222-m then reads out K (K is an integer greater than 1) of the characteristic parameters of the past frames stored in the storage unit (step S2222-33). For example, the characteristic parameters of the past K frames continuous with the current frame are read out. The extended decoding unit 2222-m then obtains the average or weighted average of the characteristic parameters of the K past frames read from the storage unit and the characteristic parameters of the current frame (step S2222-34). The weight used in the weighted average is set to the maximum value for the characteristic parameter of the current frame, and the smaller value is set for the frame farther away from the current frame. The extended decoding unit 2222-m then regards the input mono decoded digital audio signal and the average or weighted average of the feature parameters obtained in step S2222-34 as a signal in which two decoded digital audio signals are mixed, and regards the average or weighted average of the feature parameters obtained in step S2222-34 as information indicating the characteristics of the difference between the two decoded digital audio signals, obtains two decoded digital audio signals, and outputs them to the reproducing unit 223-m (step S2222-35). In addition, the extended decoding unit 2222-m may store the average or weighted average obtained in step S2222-34 as the feature parameter of the current frame in the storage unit instead of the step S2222-32 in which the feature parameter represented by the extended code is stored in the storage unit. In addition, in the storage unit of the extended decoding unit 2222-m, only K feature parameters of the past frames need to be stored, so in the processing of the next frame of the current frame, the feature parameters of the past frames that have passed by K+1 or more may be deleted from the storage unit.

[0146] <Modification of the Fourth Embodiment>

[0147] Similar to the sound signal receiving side device 220-m of the first embodiment, in the sound signal receiving side device 220-m of the third embodiment, as the feature parameter used when obtaining two decoded digital sound signals, the feature parameter represented by the extension code input in the frame to be processed and the average or weighted average of the feature parameters of the past frames may be used. That is, in the extension decoding unit 2222-m of the decoding device 222-m of the sound signal receiving side device 220-m of the third embodiment, for a predetermined frame among a plurality of frames, as the feature parameter used when obtaining two decoded digital sound signals, the feature parameter represented by the extension code input in the frame to be processed and the average or weighted average of the feature parameters of the past frames may be used. A modified example of this method as the fourth embodiment is described.

[0148] The difference between the modified example of the fourth embodiment and the third embodiment lies in the operation of the extended decoding unit 2222-m of the decoding device 222-m of the sound signal receiving side device 220-m. The difference between the modified example of the fourth embodiment and the third embodiment is described below. In the following, the extended decoding unit 2222-m that processes each frame refers to the frame that is the processing object at that moment as the current frame, and the frame that is past the current frame as the past frame.

[0149] [[[Extended decoding unit 2222-m]]]

[0150] In the extension decoding unit 2222-m, similarly to the extension decoding unit 2222-m of the third embodiment, the mono decoded digital sound signal output by the mono decoding unit 2221-m is input for each frame, and the extension code is input only for a predetermined frame among a plurality of frames. The extension decoding unit 2222-m has a storage unit (not shown). The storage unit stores at least the average or weighted average of the feature parameters obtained by the extension decoding unit 2222-m in the past frames, and sometimes also stores the feature parameters represented by the extension code of the past frames.

[0151] The extension decoding unit 2222 - m performs the following steps S2222 - 41 to S2222 - 46 on a predetermined frame among a plurality of frames, that is, a frame to which the extension code is also input.

[0152] The extension decoding unit 2222-m first obtains the feature parameters represented by the input extension code from the extension code (step S2222-41), and stores the obtained feature parameters in the storage unit (step S2222-42). The extension decoding unit 2222-m then reads out K (K is an integer greater than 1) of the feature parameters of the past frames stored in the storage unit (step S2222-43). For example, the feature parameters of the past K past frames closest to the current frame are read out. The feature parameters stored in the storage unit are only the frames to which the extension code is also input, so the feature parameters read out are the feature parameters of the K frames continuous with the current frame among the frames to which the extension code is also input. The extension decoding unit 2222-m then obtains the average or weighted average of the feature parameters of the K past frames read out from the storage unit and the feature parameters of the current frame (step S2222-44), and stores the average or weighted average of the obtained feature parameters in the storage unit (step S2222-45). The weight used in the weighted average is set to the maximum value for the feature parameter of the current frame, and the smaller value for the frame farther from the current frame. The extended decoding unit 2222-m then regards the input mono decoded digital sound signal and the average or weighted average of the feature parameters obtained in step S2222-44 as a signal mixed with two decoded digital sound signals, and regards the average or weighted average of the feature parameters obtained in step S2222-44 as information indicating the difference between the two decoded digital sound signals, obtains two decoded digital sound signals and outputs them to the regeneration unit 223-m (step S2222-46). In addition, the extended decoding unit 2222-m may not perform step S2222-42 of storing the feature parameters represented by the extended code in the storage unit, but may read the average or weighted average stored in the storage unit in step S2222-45 as the feature parameters of the past frame in step S2222-43. In addition, in the storage unit of the extended decoding unit 2222-m, only the feature parameters of K past frames are stored, so in the processing of the next frame of the current frame, the feature parameters of K+1 or more past frames that have passed can be deleted from the storage unit. In addition, in the storage unit of the extended decoding unit 2222-m, only the latest result of the average or weighted average of the feature parameters obtained in step S2222-44 is stored, so at the moment of performing step S2222-45, the average or weighted average of the feature parameters stored in the storage unit can be deleted from the storage unit.

[0153] The extension decoding unit 2222 - m according to the modification of the fourth embodiment performs the following steps S2222 - 47 to S2222 - 48 on frames other than predetermined frames among a plurality of frames, that is, frames to which the extension code is not input.

[0154] The extended decoding unit 2222-m first reads out the average or weighted average of the latest feature parameters stored in the storage unit from the storage unit (step S2222-47). The extended decoding unit 2222-m then regards the input mono decoded digital sound signal and the average or weighted average of the feature parameters obtained in step S2222-47 as a signal mixed with two decoded digital sound signals, and regards the average or weighted average of the feature parameters obtained in step S2222-47 as information indicating the difference between the two decoded digital sound signals, obtains two decoded digital sound signals and outputs them to the regeneration unit 223-m (step S2222-48).

[0155] 〔Effect〕

[0156] Although the characteristic parameter is a parameter with a small change in time from a statistical point of view, since it reflects the characteristics of the sound signal of each frame, it is rare that the value is exactly the same across multiple frames, and sometimes the value is greatly different between frames. Therefore, in the sound signal receiving side device 220-m, compared with using a characteristic parameter represented by a certain spreading code different from the original spreading code of the frame, by using the average or weighted average of the characteristic parameters represented by multiple spreading codes close in time as in the fourth embodiment and the modified example, it is possible to suppress the rapid change between the channels of the decoded sound signal or the occurrence of abnormal sounds.

[0157] <Fifth embodiment>

[0158] In the first embodiment, the sound signal receiving side device 220-m obtains a decoded digital sound signal of two channels using a monaural code and an extension code with the closest frame number for each frame, but for a frame without a monaural code and an extension code within a predetermined time limit, a decoded digital sound signal obtained by decoding the monaural code may be set as a decoded digital sound signal of two channels. This method is described in the fifth embodiment.

[0159] The fifth embodiment differs from the first embodiment in the operation of the receiving unit 221-m and the decoding unit 222-m of the sound signal receiving side device 220-m. In addition, in the decoding unit 222-m, the operation performed in the fifth embodiment that is different from that in the first embodiment is the extension decoding unit 2222-m. The differences between the fifth embodiment and the first embodiment are described below.

[0160] [[Receiving unit 221-m]]

[0161] The receiving unit 221-m outputs the monaural code included in the first code string input from the first communication line 410-m and the extended code whose frame number is closest to the frame number of the monaural code among the extended codes included in the second code string input from the second communication line 510-m, for a frame in which the difference between the frame number of the monaural code included in the first code string input from the first communication line 410-m and the extended code whose frame number is closest to the frame number of the monaural code among the extended codes included in the second code string input from the second communication line 510-m is less than a predetermined value, and outputs the monaural code included in the first code string input from the first communication line 410-m for a frame in which the difference between the frame numbers is less than a predetermined value. Specifically, the receiving unit 221-m performs the following steps S221-11 to S221-15 for each frame.

[0162] The receiving unit 221-m outputs the monaural code included in the first code string input from the first communication line 410-m to the decoding device 222-m (step S221-11). The receiving unit 221-m then obtains the frame number of the monaural code output in step S221-11 (step S221-12). The receiving unit 221-m then obtains the extension code included in the second code string having a frame number closest to the frame number of the monaural code obtained in step S221-12, and the frame number of the extension code in the second code string input from the second communication line 510-m (step S221-13). The receiving unit 221-m then determines whether the difference between the frame number of the monaural code obtained in step S221-12 and the frame number of the extension code obtained in step S221-13 is less than a predetermined value (step S221-14). Next, when the difference between the frame number of the monaural code and the frame number of the extended code is smaller than a predetermined value in step S221-14, the receiving unit 221-m outputs the extended code to the decoding device 222-m (step S221-15). When the difference between the frame number of the monaural code and the frame number of the extended code becomes smaller than a predetermined value in step S221-14, the receiving unit 221-m does not output the extended code. That is, when the difference between the frame number of the monaural code and the frame number of the extended code becomes smaller than a predetermined value in step S221-14, the receiving unit 221-m only outputs the monaural code.

[0163] Here, the predetermined value is a value greater than or equal to 2. That is, the receiving unit 221-m outputs the mono code (i.e., the mono code in the order of frame numbers) contained in the first code string input from the first communication line 410-m and the frame number of the extended code whose frame number is closest to the frame number of the mono code contained in the second code string input from the second communication line 510-m, and the mono code (i.e., the mono code in the order of frame numbers) contained in the first code string input from the first communication line 410-m, and the frame number of the extended code contained in the second code string input from the second communication line 510-m The frame number is 0. For frames where the difference in frame numbers is greater than 0 and less than a predetermined value, the mono code contained in the first code string input from the first communication line 410-m (i.e., the mono code in frame number order) and the extended code whose frame number is closest to the frame number of the mono code among the extended codes contained in the second code string input from the second communication line 510-m (i.e., the extended code whose frame number is different from the frame number of the mono code but is closest to the frame number of the mono code among the extended codes contained in the second code string input from the second communication line 510-m) are output; for frames where the difference in frame numbers is less than a predetermined value, only the mono code contained in the first code string input from the first communication line 410-m (i.e., the mono code in frame number order) is output.

[0164] [[Decoding device 222-m]]

[0165] In the decoding device 222-m, the monaural code outputted from the receiving unit 221-m is always inputted for each frame, and the extended code outputted from the receiving unit 221-m is sometimes inputted. The decoding device 222-m obtains a decoded digital audio signal of two channels corresponding to the inputted monaural code and extended code, or the inputted monaural code, for each frame, and outputs it to the reproducing unit 223-m. Specifically, the decoding device 222-m obtains and outputs a decoded digital audio signal of two channels based on the monaural code outputted from the receiving unit 221-m and the extended code outputted from the receiving unit 221-m for the frame whose frame number difference is less than a predetermined value, and outputs the monaural digital signal based on the monaural code outputted from the receiving unit 221-m as a decoded digital audio signal of two channels as it is for the frame whose frame number difference is not less than a predetermined value.

[0166] [[[Extended decoding unit 2222-m]]]

[0167] In the extended decoding unit 2222-m, the decoded digital audio signal of the monaural channel outputted from the monaural decoding unit 2221-m is always inputted for each frame, and the extension code inputted to the decoding device 222-m is sometimes inputted. For the frame to which the decoded digital audio signal of the monaural channel and the extension code are inputted, the extended decoding unit 2222-m obtains a decoded digital audio signal of two channels from the inputted decoded digital audio signal of the monaural channel and the extension code by the same operation as the extended decoding unit 2222-m of the first embodiment, and outputs it to the reproducing unit 223-m. For the frame to which only the decoded digital audio signal of the monaural channel is inputted, the extended decoding unit 2222-m obtains the decoded digital audio signal of the monaural channel as it is as a decoded digital audio signal of two channels, and outputs it to the reproducing unit 223-m.

[0168] That is, the decoding device 222-m obtains and outputs a decoded digital sound signal of two channels based on the monaural code and the extended code with a frame number closest to the frame number of the monaural code for a frame in which the difference between the frame number of the monaural code included in the first code string input from the first communication line 410-m and the extended code included in the second code string input from the second communication line 510-m and the frame number of the extended code is less than a predetermined value, and outputs the decoded digital sound signal based on the monaural code included in the first code string input from the first communication line 410-m as a decoded digital sound signal of two channels as is, and for a frame in which the difference between the frame numbers is not less than a predetermined value.

[0169] More specifically, the decoding device 222-m obtains and outputs a decoded digital sound signal of two channels based on the monaural code and the extended code having the same frame number as the frame number of the monaural code, for a frame whose frame number difference is 0 between the monaural code contained in the first code string input from the first communication line 410-m (i.e., the monaural code in the order of frame numbers) and the extended code whose frame number is closest to the frame number of the monaural code as the extended code contained in the second code string input from the second communication line 510-m (i.e., the frame containing the extended code in the second code string input from the second communication line 510-m having the same frame number as the frame number of the monaural code contained in the first code string input from the first communication line 410-m). For a frame whose frame number difference is greater than 0 and less than a predetermined frame number, the decoding device 222-m obtains and outputs a decoded digital sound signal of two channels based on the monaural code and the extended code having the same frame number as the frame number of the monaural code, and outputs a decoded digital sound signal of two channels based on the monaural code and the extended code having the same frame number as the frame number of the monaural code. A decoded digital sound signal for two channels is obtained and outputted based on a frame with a predetermined value, based on a monaural code contained in a first code string input from the first communication line 410-m (i.e., a monaural code in frame number sequence) and an extended code having a frame number closest to the frame number of the monaural code (i.e., an extended code having a frame number that is different from the frame number of the monaural code but closest to the frame number of the monaural code in the extended code contained in a second code string input from the second communication line 510-m), and for a frame with a frame number difference that is not less than a predetermined value, a decoded digital sound signal based on the monaural code contained in the first code string input from the first communication line 410-m (i.e., a monaural code in frame number sequence) is outputted as a decoded digital sound signal for two channels.

[0170] <Modification of the Fifth Embodiment>

[0171] The above description is about the sound signal receiving side device 220-m and its operation of the fifth embodiment based on the structure of the sound signal receiving side device 220-m of the first embodiment, but the sound signal receiving side device 220-m of the fifth embodiment based on the sound signal receiving side device 220-m of any one of the third embodiment and the fourth embodiment and their modified examples may be configured and operated.

[0172] 〔Effect〕

[0173] The encoding device 212-m' of the voice signal transmitting side device 210-m' of the multiple line corresponding terminal device 200-m' at the other end of the call encodes each frame in a predetermined time interval, so the difference between the frame number of the monaural code and the frame number of the extended code corresponds to the time difference of the digital voice signal encoded by the encoding device 212-m' of the voice signal transmitting side device 210-m' of the multiple line corresponding terminal device 200-m' at the other end of the call. For example, if the frame length is 20ms and the difference in the frame number is 150, there is a time difference of 3 seconds between the digital voice signal obtained by the monaural code and the digital voice signal obtained by the extended code. Even if the parameter changes slightly in time, there is a possibility that the value changes greatly if the time is greatly different. Therefore, when the characteristic parameter represented by the extended code has a greatly different time difference, there is a possibility that a large error occurs in the division of the signal between the channels in the decoded voice signal of the two channels reflecting the difference characteristics of the two channels. According to the fifth embodiment, by preventing a difference from occurring in the decoded audio signals of the two channels for a frame having a large difference between the frame number of the monaural code included in the first code string received from the first communication line and the frame number of the extended code included in the second code string received from the second communication line and the frame number of the monaural code, it is possible to suppress a large error in the division of the signal between the channels of the decoded audio signal. For example, it is assumed that if the time difference becomes 400 ms or more, the characteristic parameter will be greatly different. If the frame length is 20 ms, the characteristic parameter will be greatly different when the frame number difference becomes 20 or more. Therefore, the above-mentioned predetermined value may be set to 20, for example.

[0174] <Sixth embodiment>

[0175] The sound signal receiving side device 220-m can set the decoded digital sound signal obtained by decoding the monaural code as a decoded digital sound signal of two channels based on the average value of the time difference between the first code string input from the first communication line 410-m and the second code string having the same frame number as the first code string input from the second communication line 510-m measured within a predetermined time range, when the average value of the time difference is not within a predetermined limit time. This mode is described as a sixth embodiment.

[0176] The sixth embodiment differs from the first embodiment in the operations of the receiving unit 221-m and the decoding unit 222-m of the sound signal receiving side device 220-m. In addition, the extended decoding unit 2222-m performs the operations that are different between the sixth embodiment and the first embodiment in the decoding unit 222-m. The differences between the sixth embodiment and the first embodiment are described below.

[0177] [[Receiving unit 221-m]]

[0178] In the receiving unit 221-m, the first code string outputted by the voice signal transmitting side device 210-m' at the other end of the call is inputted from the first communication line 410-m, and the second code string outputted by the voice signal transmitting side device 210-m' at the other end of the call is inputted from the second communication line 510-m. The second communication line is a communication network with a low priority, so the second code string of a certain frame outputted by the voice signal transmitting side device 210-m' at the other end of the call is usually inputted into the receiving unit 221-m from the second communication line 510-m after the first code string of the frame is inputted from the first communication line 410-m.

[0179] The receiving unit 221-m first determines whether an average value of the difference between the time when the first code string is received and the time when the second code string is received for a group of a first code string received from the first communication line 410-m and a second code string received from the second communication line 510-m corresponding to the first code string is less than a predetermined time limit Tmax. The time limit Tmax is, for example, 400 ms.

[0180] For example, the receiving unit 221-m performs the following steps S221-21 to S221-24. The receiving unit 221-m reads the frame number for the first code string of a predetermined number from the start of receiving the first code string, measures the time of reception, associates the frame number with the time when the first code string is received, and stores it in a storage unit (not shown) within the receiving unit 221-m (step S221-21). The receiving unit 221-m also reads the frame number for the received second code string, and when the read frame number matches any of the frame numbers stored in the storage unit, measures the time of reception, associates the frame number stored in the storage unit with the time when the first code string is received, and stores it in the storage unit (step S221-22). The receiving unit 221-m then uses the frame number, the time when the first code string is received, and the time when the second code string is received that are associated and stored in the storage unit to obtain an average value of the value obtained by subtracting the time when the first code string is received from the time when the second code string is received for each frame number for the above-mentioned predetermined number (step S221-23). ​​The receiving unit 221-m then determines whether the average value obtained in step S221-23 is less than the predetermined limit time Tmax (step S221-24).

[0181] The receiving unit 221-m then outputs the monaural code included in the first code string input from the first communication line 410-m and the extended code included in the second code string input from the second communication line 510-m, whose frame number is closest to the frame number of the monaural code, to the decoding device 222-m for subsequent frames when the average value is less than the limit time Tmax in the above judgment. When the average value is not less than the limit time Tmax in the above judgment, the monaural code included in the first code string input from the first communication line 410-m is output to the decoding device 222-m for subsequent frames. When the average value is not less than the limit time Tmax in the above judgment, the receiving unit 221-m does not output the extended code for subsequent frames. That is, when the average value is not less than the limit time Tmax in the above judgment, the receiving unit 221-m only outputs the monaural code.

[0182] That is, when the average value of the difference between the time when the first code string and the second code string are received for a group of a first code string received from the first communication line 410-m and a second code string received from the second communication line 510-m corresponding to the first code string is less than a predetermined limit time Tmax for multiple groups, the receiving unit 221-m outputs the monaural code and the monaural code with the same frame number to the decoding device 222-m for subsequent frames when the extended code included in the second code string input from the second communication line 510-m includes an extended code with the same frame number as the monaural code (i.e., the monaural code in the order of frame numbers) included in the first code string input from the first communication line 410-m, and does not include the extended code included in the second code string input from the second communication line 510-m with the same frame number as the monaural code (i.e., the monaural code in the order of frame numbers). In the case of an extended code having the same frame number as the mono code included in the first code string (i.e., the mono code in frame number sequence), the mono code included in the first code string input from the first communication line 410-m (i.e., the mono code in frame number sequence) and the extended code whose frame number is closest to the frame number of the mono code among the extended codes included in the second code string input from the second communication line 510-m (i.e., the extended code whose frame number is different from the frame number of the mono code but is closest to the frame number of the mono code among the extended codes included in the second code string input from the second communication line 510-m) are output to the decoding device 222-m, and in the case where the above-mentioned average value is not less than the limit time Tmax, for subsequent frames, only the mono code included in the first code string input from the first communication line 410-m (i.e., the mono code in frame number sequence) is output to the decoding device 222-m.

[0183] In addition, the receiving unit 221-m may output nothing before the above-mentioned judgment is completed, or may output the monaural code and the extended code to the decoding device 222-m in the same manner as the first embodiment, or may output the monaural code to the decoding device 222-m without outputting the extended code, or may output the monaural code to the decoding device 222-m without fail in the same manner as the fifth embodiment, and output the extended code to the decoding device 222-m only when the difference in frame number between the monaural code and the extended code is small.

[0184] [[Decoding device 222-m]]

[0185] When the average value is less than the predetermined time limit Tmax in the above determination by the receiving unit 221-m, the monaural code and the extended code are input to the decoding unit 222-m for each frame, as in the decoding unit 222-m of the first embodiment. On the other hand, when the average value is not less than the predetermined time limit Tmax in the above determination by the receiving unit 221-m, the monaural code output by the receiving unit 221-m is input to the decoding unit 222-m for each frame, and the extended code is not input.

[0186] Before the above determination by the receiving unit 221-m is completed, nothing is input to the decoding device 222-m, or a monaural code is input instead of an extension code, or a monaural code and an extension code are input. The decoding device 222-m obtains a decoded digital audio signal of two channels corresponding to the input monaural code and extension code, or the input monaural code, for each frame, and outputs it to the reproducing unit 223-m.

[0187] [[[Extended decoding unit 2222-m]]]

[0188] When a decoded digital audio signal of a monaural channel and a spread code are input, that is, when the average value is less than the predetermined limit time Tmax in the above judgment, the extension decoding unit 2222-m obtains a decoded digital audio signal of two channels for each frame from the decoded digital audio signal of a monaural channel and the spread code through the same operation as the extension decoding unit 2222-m of the first embodiment, and outputs the decoded digital audio signal to the reproducing unit 223-m. When a decoded digital audio signal of a monaural channel is input, that is, when the average value is not less than the predetermined limit time Tmax in the above judgment, the extension decoding unit 2222-m obtains the decoded digital audio signal of a monaural channel as it is, and outputs the decoded digital audio signal of two channels to the reproducing unit 223-m.

[0189] That is, when the average value of the difference between the time when the first code string and the second code string are received for a group of a first code string received from the first communication line 410-m and a second code string received from the second communication line 510-m corresponding to the first code string is less than a predetermined limit time Tmax for multiple groups, the decoding device 222-m obtains and outputs a decoded digital sound signal of two channels based on the monaural code contained in the first code string input from the first communication line 410-m and the extended code contained in the second code string input from the second communication line 510-m, i.e., the extended code having a frame number closest to the monaural code, and when the above-mentioned average value is not less than the limit time Tmax, the decoded digital sound signal of the mono channel based on the monaural code contained in the first code string input from the first communication line 410-m is output as a decoded digital sound signal of two channels as it is.

[0190] More specifically, the decoding device 222-m estimates the monaural code and the monaural code having the same frame number as the monaural code (i.e., the monaural code in the order of frame numbers) contained in the extended code included in the second code string input from the first communication line 410-m, and obtains and outputs a decoded digital sound signal of two channels, and estimates the monaural code and the extended code having the same frame number as the monaural code (i.e., the monaural code in the order of frame numbers) contained in the extended code included in the second code string input from the first communication line 410-m, for a frame in which the extended code included in the second code string input from the second communication line 510-m does not contain the same frame number as the monaural code (i.e., the monaural code in the order of frame numbers) contained in the first code string input from the first communication line 410-m, and outputs a decoded digital sound signal of two channels. The mono code (i.e., the mono code in frame number sequence) contained in the first code string input from the first communication line 410-m is estimated, and the mono code (i.e., the mono code in frame number sequence) contained in the second code string input from the second communication line 510-m and the extended code whose frame number is closest to the frame number of the mono code (i.e., the extended code contained in the second code string input from the second communication line 510-m, although the frame number is different from the frame number of the mono code, the frame number is closest to the frame number of the mono code), and the decoded digital sound signal of the two channels is obtained and output, and when the above-mentioned average value is not less than the limit time Tmax, the decoded digital sound signal of the mono channel based on the mono code (i.e., the mono code in frame number sequence) contained in the first code string input from the first communication line 410-m is output as the decoded digital sound signal of the two channels as it is.

[0191] In addition, before the above-mentioned determination by the receiving unit 221-m is completed, the extended decoding unit 2222-m obtains a two-channel decoded digital sound signal from the input mono decoded digital sound signal and the extended code for the frame to which the mono decoded digital sound signal and the extended code are input, and outputs it to the regeneration unit 223-m, or obtains the input mono decoded digital sound signal as it is as a two-channel decoded digital sound signal and outputs it to the regeneration unit 223-m, or outputs nothing.

[0192] <Modification of Sixth Embodiment>

[0193] The above description is about the sound signal receiving side device 220-m and its operation of the sixth embodiment based on the structure of the sound signal receiving side device 220-m of the first embodiment. The sound signal receiving side device 220-m of the sixth embodiment can also be configured based on the sound signal receiving side device 220-m of any one of the third embodiment to the fifth embodiment and their modified examples to operate. In addition, in the above example, the time from the start of receiving the first code string to the reception of a predetermined number of first code strings is used as the prescribed time range, but the prescribed time range can be set at any time as the starting point. For example, the interval starting from a certain time after the start of receiving the first code string can be used as the prescribed time range, and the interval starting from each of multiple times after the start of receiving the first code string can be set as the prescribed time range.

[0194] 〔Effect〕

[0195] As described in the fifth embodiment, even if the characteristic parameter has a small change in time, there is a possibility that the value will change greatly if the time is greatly different. Therefore, in the case where it is determined that there is a time difference between the characteristic parameter represented by the spread code between the first communication line and the second communication line that is greatly different, there is a possibility that a large error will occur in the division of the signal between the channels in the decoded sound signal of the two channels that reflects the difference characteristics of the two channels. According to this sixth embodiment, in the case where the difference between the time when the first code string is received from the first communication line and the time when the second code string is received from the second communication line for the same frame is large, by preventing the difference from occurring in the decoded sound signal of the two channels, a large error in the division of the signal between the channels of the decoded sound signal can be suppressed.

[0196] <Seventh embodiment>

[0197] The sound signal receiving side device 220-m may use a monaural code and an extension code having the same frame number as the monaural code to decode a two-channel digital sound signal based on the average value of the time difference between the first code string input from the first communication line 410-m and the second code string input from the second communication line 510-m having the same frame number as the first code string, measured within a predetermined time range, and when the average value of the time difference is within a predetermined time limit. This method will be described as the seventh embodiment.

[0198] The seventh embodiment is different from the first embodiment in the operation of the receiving unit 221 - m of the audio signal receiving-side device 220 - m. The differences between the seventh embodiment and the first embodiment will be described below.

[0199] [[Receiving unit 221-m]]

[0200] In the receiving unit 221-m, the first code string outputted by the voice signal transmitting side device 210-m' at the other end of the call is inputted from the first communication line 410-m, and the second code string outputted by the voice signal transmitting side device 210-m' at the other end of the call is inputted from the second communication line 510-m2. The second communication line is a communication network with a low priority, so the second code string of a certain frame outputted by the voice signal transmitting side device 210-m' at the other end of the call is usually inputted to the receiving unit 221-m from the second communication line 510-m after the first code string of the frame is inputted from the first communication line 410-m.

[0201] The receiving unit 221-m first determines whether the average value of the difference between the time when the first code string and the second code string are received for a group of the first code string received from the first communication line 410-m and the second code string received from the second communication line 510-m corresponding to the first code string is less than a predetermined limit time Tmin. In addition, the limit time Tmin is, for example, a value twice the frame length. That is, if the frame length is 20ms, the limit time Tmin is, for example, 40ms.

[0202] For example, the receiving unit 221-m performs the following steps S221-31 to S221-34. The receiving unit 221-m reads the frame number for the first code string of a predetermined number from the start of receiving the first code string, measures the time of reception, and stores the frame number in a storage unit (not shown) in the receiving unit 221-m in association with the time of reception of the first code string (step S221-31). In addition, the receiving unit 221-m reads the frame number for the received second code string, and when the read frame number matches any of the frame numbers stored in the storage unit, measures the time of reception, and stores the frame number stored in the storage unit and the time of reception of the first code string in association with the time of reception of the second code string in the storage unit (step S221-32). The receiving unit 221-m then uses the frame number, the time when the first code string is received, and the time when the second code string is received that are stored in association in the storage unit to obtain an average value of the value obtained by subtracting the time when the first code string is received from the time when the second code string is received for each frame number for the predetermined number of values ​​(step S221-33). The receiving unit 221-m then determines whether the average value obtained in step S221-33 is less than the predetermined limit time Tmin (step S221-34).

[0203] The receiving unit 221-m then outputs the monaural code contained in the first code string input from the first communication line 410-m and the extended code contained in the second code string input from the second communication line 510-m, whose frame number is the same as the frame number of the monaural code, to the decoding device 222-m for subsequent frames if the average value is less than the limit time Tmin in the above judgment. If the average value is not less than the limit time Tmin in the above judgment, the monaural code contained in the first code string input from the first communication line 410-m and the extended code contained in the second code string input from the second communication line 510-m, whose frame number is closest to the frame number of the monaural code, to the decoding device 222-m for subsequent frames. However, since it is assumed that the time required for averaging from the time the first code string is received on the first communication line 410-m to the time the second code string is received on the second communication line 510-m of the frame is equal to the average value obtained in step S221-33, the receiving unit 221-m needs to operate in such a way that the time from the time the first code string is received on the first communication line 410-m to the time the first code string is output to the decoding device 222-m becomes the average value obtained in step S221-33 or a value greater than the average value.

[0204] That is, when the average value of the difference between the time when the first code string and the second code string are received for a group of a first code string received from the first communication line 410-m and a second code string received from the second communication line 510-m corresponding to the first code string is less than a predetermined limit time Tmin for a plurality of groups, the receiving unit 221-m outputs, for subsequent frames, a monaural code (i.e., a monaural code in the order of frame numbers) contained in the first code string input from the first communication line 410-m and an extended code having a frame number identical to that of the monaural code in an extended code contained in the second code string input from the second communication line 510-m to the decoding device 222-m, and when the above-mentioned average value is less than the limit time Tmin, for subsequent frames, an extended code having a frame number identical to that of the monaural code contained in the extended code contained in the second code string input from the second communication line 510-m In the case of an extended code having the same frame number as the mono code (i.e., a mono code in frame number sequence), the mono code and the extended code having the same frame number as the frame number of the mono code are output to the decoding device 222-m. In the case of an extended code included in the second code string input from the second communication line 510-m not including an extended code having the same frame number as the mono code included in the first code string input from the first communication line 410-m (i.e., a mono code in frame number sequence), the mono code included in the first code string (i.e., a mono code in frame number sequence) and an extended code having a frame number closest to the frame number of the mono code among the extended codes included in the second code string input from the second communication line 510-m (i.e., an extended code having a frame number that is different from the frame number of the mono code but is closest to the frame number of the mono code among the extended codes included in the second code string input from the second communication line 510-m) are output to the decoding device 222-m.

[0205] The operation of the decoding device 222-m of the sound signal receiving side device 220-m of the seventh embodiment is the same as the operation of the decoding device 222-m of the sound signal receiving side device 220-m of the first embodiment. The decoding device 222-m obtains and outputs a decoded digital sound signal of two channels based on the monaural code output by the receiving unit 221-m and the extension code output by the receiving unit 221-m. However, the extension code output by the receiving unit 221-m of the seventh embodiment is different from the extension code output by the receiving unit 221-m of the first embodiment depending on the situation, so the decoding device 222-m specifically performs the following operation.

[0206] That is, the decoding device 222-m obtains and outputs a decoded digital sound signal of two channels based on the monaural code included in the first code string input from the first communication line 410-m and the extended code which is an extended code included in the second code string input from the second communication line 510-m and has the same frame number as the monaural code, when the average value of the difference between the times when the first code string and the second code string are received for a group of a first code string received from the first communication line 410-m and a second code string received from the second communication line 510-m corresponding to the first code string is less than a predetermined limit time Tmin, and obtains and outputs a decoded digital sound signal of two channels based on the monaural code included in the first code string input from the first communication line 410-m and the extended code which is an extended code included in the second code string input from the second communication line 510-m and has a frame number closest to the frame number of the monaural code, when the above-mentioned average value is not less than the limit time Tmin.

[0207] More specifically, the decoding device 222-m obtains and outputs a decoded digital sound signal of two channels based on the monaural code (i.e., the monaural code in frame number sequence) contained in the first code string input from the first communication line 410-m and the extended code (i.e., the extended code having the same frame number as the monaural code) contained in the second code string input from the second communication line 510-m, when the average value of the difference between the time when the first code string and the second code string are received for a plurality of groups of the first code string received from the first communication line 410-m and the second code string corresponding to the first code string received from the second communication line 510-m is less than a predetermined limit time Tmin, and when the above-mentioned average value is not less than the limit time Tmin, for the monaural code (i.e., the monaural code in frame number sequence) contained in the extended code contained in the second code string input from the second communication line 510-m The decoded digital sound signals of two channels are obtained and outputted according to the monaural code and the extended code having the same frame number as the frame number of the monaural code, and the extended code contained in the second code string input from the second communication line 510-m does not contain a frame having the same frame number as the monaural code (i.e., the monaural code in the frame number sequence) contained in the first code string input from the first communication line 410-m, according to the first generation input from the first communication line 410-m. The mono code contained in the code string (i.e., the mono code in frame number order) and the extended code whose frame number is closest to the frame number of the mono code as the extended code contained in the second code string input from the second communication line 510-m (i.e., among the extended codes contained in the second code string input from the second communication line 510-m, the extended code whose frame number is different from the frame number of the mono code but is closest to the frame number of the mono code) are obtained and output as decoded digital sound signals of 2 channels.

[0208] In addition, before the above-mentioned judgment performed by the receiving unit 221-m is completed, for example, the receiving unit 221-m can output the monaural code and the extended code to the decoding device 222-m in the same way as the first embodiment, and the decoding device 222-m can use the monaural code and the extended code in the same way as the first embodiment to obtain a decoded digital sound signal of 2 channels and output it to the regeneration unit 223-m.

[0209] <Modification of Seventh Embodiment>

[0210] The above description is about the sound signal receiving side device 220-m and its operation of the seventh embodiment based on the structure of the sound signal receiving side device 220-m of the first embodiment, but the sound signal receiving side device 220-m of the seventh embodiment based on the sound signal receiving side device 220-m of any one of the third embodiment to the fifth embodiment and their modified examples can also be configured to operate. In addition, in the above example, the time from the start of receiving the first code string to the reception of a predetermined number of first code strings is used as the prescribed time range, but the prescribed time range can be set at any time as the starting point, for example, the interval starting from a certain time after the start of receiving the first code string can be used as the prescribed time range, and the interval starting from each of multiple times after the start of receiving the first code string can also be set as the prescribed time range.

[0211] 〔Effect〕

[0212] Even for feature parameters with small time variations, there is a possibility that the values ​​are slightly different if the time is different. Therefore, if it is possible to decode using the feature parameters of the same frame by only slightly increasing the delay, it is possible to obtain a decoded sound signal with high sound quality. Therefore, in the seventh embodiment, for the average value of the specified time range of the difference between the moment when the first code string of the same frame is received from the first communication line and the moment when the second code string is received from the second communication line, a limit time is set as a predetermined value. When it is less than the limit time, a decoded digital sound signal with a 2-channel sound is obtained by using a monaural code and an extension code of the same frame as the monaural code after slightly increasing the delay, thereby obtaining a decoded sound signal with high sound quality.

[0213] <Eighth Embodiment>

[0214] The sound signal receiving side device 220-m obtains a decoded digital sound signal of two channels by using a monaural code and an extension code having the same frame number as the monaural code, based on the average value of the time difference between the first code string input from the first communication line 410-m and the second code string input from the second communication line 510-m measured within a prescribed time range, when the average value of the time difference is less than the first limit time, and when the average value of the time difference is greater than a predetermined second limit time greater than the first limit time, the decoded digital sound signal obtained by decoding the monaural code is set as a decoded digital sound signal of two channels, and when the average value of the time difference is greater than or equal to the first limit time and less than the second limit time, the decoded digital sound signal of two channels is obtained by using a monaural code and an extension code having the closest frame number to the monaural code. In short, the sixth embodiment and the seventh embodiment can be implemented in combination. This mode is described as the eighth embodiment.

[0215] The eighth embodiment differs from the first embodiment in the operation of the receiving unit 221-m and the decoding unit 222-m of the sound signal receiving side device 220-m. However, the operation of the decoding unit 222-m of the sound signal receiving side device 220-m is the same as the operation of the decoding unit 222-m of the sixth embodiment. The operation of the receiving unit 221-m of the eighth embodiment, which is different from the first embodiment and also from the sixth embodiment, is described below.

[0216] [[Receiving unit 221-m]]

[0217] In the receiving unit 221-m, the first code string outputted by the voice signal transmitting side device 210-m' at the other end of the call is inputted from the first communication line 410-m, and the second code string outputted by the voice signal transmitting side device 210-m' at the other end of the call is inputted from the second communication line 510-m. The second communication line is a communication network with a low priority, so the second code string of a certain frame outputted by the voice signal transmitting side device 210-m' at the other end of the call is usually inputted to the receiving unit 221-m from the second communication line 510-m after the first code string of the frame is inputted from the first communication line 410-m.

[0218] The receiving unit 221-m first determines whether the average value of the difference between the time when the first code string and the second code string are received for a group of the first code string received from the first communication line 410-m and the second code string received from the second communication line 510-m corresponding to the first code string is less than the predetermined first limit time Tmin, or is greater than or equal to the predetermined second limit time Tmax greater than the first limit time Tmin, or is greater than or equal to the first limit time Tmin and less than the second limit time Tmax. In addition, the first limit time Tmin is, for example, a value twice the frame length. That is, if the frame length is 20ms, the first limit time Tmin is, for example, 40ms. In addition, the second limit time Tmax is, for example, 400ms.

[0219] For example, the receiving unit 221-m performs the following steps S221-41 to S221-44. The receiving unit 221-m reads the frame number for the first code string of a predetermined number from the start of receiving the first code string, measures the time of reception, and stores the frame number in a storage unit (not shown) in the receiving unit 221-m in association with the time of reception of the first code string (step S221-41). In addition, the receiving unit 221-m reads the frame number for the received second code string, and when the read frame number matches any of the frame numbers stored in the storage unit, measures the time of reception, and stores the frame number stored in the storage unit and the time of reception of the first code string in association with the time of reception of the second code string in the storage unit (step S221-42). Next, the receiving unit 221-m uses the frame number, the time when the first code string is received, and the time when the second code string is received that are associated and stored in the storage unit to obtain the average value of the value obtained by subtracting the time when the first code string is received from the time when the second code string is received for each frame number for the above-mentioned predetermined number (step S221-43). Next, the receiving unit 221-m determines whether the average value obtained in step S221-43 is less than the predetermined first limit time Tmin, or greater than or equal to the predetermined second limit time Tmax that is greater than the first limit time Tmin, or greater than or equal to the first limit time Tmin and less than the second limit time Tmax (step S221-44).

[0220] Next, when the average value is less than the first limit time Tmin in the above judgment, the receiving unit 221-m outputs the monaural code included in the first code string input from the first communication line 410-m and the extended code whose frame number is the same as the frame number of the monaural code among the extended codes included in the second code string input from the second communication line 510-m to the decoding device 222-m for subsequent frames. When the average value is greater than or equal to the first limit time Tmin and less than the second limit time Tmax in the above judgment, the monaural code included in the first code string input from the first communication line 410-m and the extended code whose frame number is closest to the frame number of the monaural code among the extended codes included in the second code string input from the second communication line 510-m are output to the decoding device 222-m for subsequent frames. When the average value is less than the second limit time Tmax in the above judgment, the monaural code included in the first code string input from the first communication line 410-m is output to the decoding device 222-m for subsequent frames. When the average value is less than the second limit time Tmax in the above judgment, the receiving unit 221-m does not output the extension code for the subsequent frames. That is, when the average value is less than the second limit time Tmax in the above judgment, the receiving unit 221-m only outputs the monaural code. However, from the time when the first code string is received on the first communication line to the time when the second code string is received on the second communication line of the frame, it is assumed that the time required to obtain the average value in step S221-43 is required if the average is performed. Therefore, the receiving unit 221-m needs to operate in such a way that the time from the time when the first code string is received on the first communication line to the time when it is output to the decoding device 222-m is the average value obtained in step S221-43 or a value greater than it.

[0221] That is, when the average value of the difference between the time when the first code string and the second code string are received for a group of a first code string received from the first communication line 410-m and a second code string received from the second communication line 510-m corresponding to the first code string is less than a predetermined limit time Tmin for a plurality of groups, the receiving unit 221-m transmits the monaural code (i.e., the monaural code in the order of the frame number) contained in the first code string input from the first communication line 410-m and the monaural code (i.e., the monaural code in the order of the frame number) in the second code string input from the second communication line 510-m for subsequent frames. The extended code whose frame number is the same as the frame number of the mono code in the extended code contained in the second code string input from the second communication line 510-m is output to the decoding device 222-m. When the above-mentioned average value is greater than or equal to the first limit time Tmin and less than the second limit time Tmax, for the subsequent frames, when the extended code contained in the second code string input from the second communication line 510-m contains an extended code whose frame number is the same as the frame number of the mono code (that is, the mono code in the frame number sequence) contained in the first code string input from the first communication line 410-m, the mono code and the mono code with the frame number identical to the frame number of the mono code are output to the decoding device 222-m. The second code string input from the second communication line 510-m outputs an extended code having the same frame number as the mono code (i.e., the mono code in the frame number sequence) contained in the first code string input from the first communication line 410-m, and outputs an extended code having the same frame number as the mono code (i.e., the mono code in the frame number sequence) contained in the first code string input from the first communication line 410-m to the decoding device 222-m. In the case where the extended code contained in the second code string input from the second communication line 510-m does not contain an extended code having the same frame number as the mono code (i.e., the mono code in the frame number sequence) contained in the first code string input from the first communication line 410-m, and the extended code contained in the second code string input from the second communication line 510-m are outputted to the decoding device 222-m. The extended code whose frame number is closest to the frame number of the mono code (that is, among the extended codes included in the second code string input from the second communication line 510-m, although the frame number is different from the frame number of the mono code, the extended code whose frame number is closest to the frame number of the mono code) is output to the decoding device 222-m, and when the above-mentioned average value is not less than the second limit time Tmax, for the subsequent frames, only the mono code contained in the first code string input from the first communication line 410-m (that is, the mono code in frame number order) is output to the decoding device 222-m.

[0222] In addition, before the above-mentioned judgment is completed, the receiving unit 221-m may output nothing, or may output the monaural code and the extended code to the decoding device 222-m as in the first embodiment, or may output the monaural code to the decoding device 222-m without outputting the extended code, or may output the monaural code to the decoding device 222-m without fail as in the fifth embodiment, and may output the extended code to the decoding device 222-m only when the difference between the frame numbers of the monaural code and the extended code is small.

[0223] The operation of the decoding device 222-m of the sound signal receiving side device 220-m of the eighth embodiment is the same as the operation of the decoding device 222-m of the sound signal receiving side device 220-m of the sixth embodiment. However, the spreading code output by the receiving unit 221-m of the eighth embodiment is different from the spreading code output by the receiving unit 221-m of the sixth embodiment in some cases, so the decoding device 222-m specifically performs the following operation.

[0224] That is, when the average value in the above judgment is less than the first limit time Tmin, and when the average value in the above judgment is greater than or equal to the first limit time Tmin and less than the second limit time Tmax, the decoding device 222-m obtains and outputs a decoded digital sound signal of two channels based on the monaural code output by the receiving unit 221-m and the extended code output by the receiving unit 221-m for subsequent frames, and when the average value in the above judgment is greater than or equal to the second limit time Tmax, for subsequent frames, the decoded monophonic digital sound signal based on the monaural code output by the receiving unit 221-m is output as a decoded digital sound signal of two channels as it is.

[0225] More specifically, the decoding device 222-m obtains and outputs a decoded digital sound signal of two channels based on the monaural code included in the first code string input from the first communication line 410-m and the extended code included in the second code string input from the second communication line 510-m and having the same frame number as the monaural code, when the average value of the difference between the time when the first code string and the second code string are received for a plurality of groups of the first code string received from the first communication line 410-m and the second code string corresponding to the first code string received from the second communication line 510-m is less than or equal to a predetermined first limit time Tmin, and the decoded digital sound signal of two channels is obtained and outputted when the average value is greater than or equal to a predetermined second limit time Tmin which is greater than the first limit time Tmin. max, the decoded digital sound signal of the mono channel based on the mono code contained in the first code string input from the first communication line 410-m is output as is as the decoded digital sound signal of the two channels, and when the above-mentioned average value is greater than or equal to the first limit time Tmin and less than the second limit time Tmax, the decoded digital sound signals of the two channels are obtained and output based on the mono code contained in the first code string input from the first communication line 410-m and the extended code which is included in the second code string input from the second communication line 510-m and has a frame number closest to the frame number of the mono code.

[0226] More specifically, the decoding device 222-m decodes the first code string received from the first communication line 410-m and the second code string received from the second communication line 510-m corresponding to the first code string, based on the monaural code (i.e., the monaural code in the order of the frame number) included in the first code string input from the first communication line 410-m and the extended code included in the second code string input from the second communication line 510-m and the frame number is less than the predetermined first limit time Tmin. The decoded digital sound signals of the two channels are obtained and outputted by using an extended code having a frame number which is the same as the frame number of the monaural code. When the above-mentioned average value is greater than or equal to a predetermined second limit time Tmax which is greater than the first limit time Tmin, the decoded digital sound signal of the monaural code (i.e., the monaural code in the order of the frame number) included in the first code string input from the first communication line 410-m is outputted as is as the decoded digital sound signals of the two channels. When the above-mentioned average value is greater than or equal to the first limit time Tmin and less than the second limit time Tmax, the decoded digital sound signal of the monaural code included in the first code string input from the second communication line 410-m is outputted as is. For a frame in which the extended code included in the second code string input from the second communication line 510-m includes an extended code having the same frame number as the monaural code (i.e., the monaural code in the frame number sequence) included in the first code string input from the first communication line 410-m, a decoded digital sound signal of two channels is obtained and output based on the monaural code and the extended code having the same frame number as the frame number of the monaural code, and for a frame in which the extended code included in the second code string input from the second communication line 510-m does not include the same frame number as the monaural code (i.e., the monaural code in the frame number sequence) included in the first code string input from the first communication line 410-m A decoded digital sound signal of two channels is obtained and outputted based on the monaural code contained in the first code string input from the first communication line 410-m (i.e., the monaural code in frame number order) and the extended code contained in the second code string input from the second communication line 510-m, i.e., the extended code having a frame number closest to the frame number of the monaural code (i.e., among the extended codes contained in the second code string input from the second communication line 510-m, the extended code having a frame number that is different from the frame number of the monaural code but is closest to the frame number of the monaural code).

[0227] In addition, before the above-mentioned determination by the receiving unit 221-m is completed, nothing is input to the decoding device 222-m, or the monaural code is input instead of the extension code, or the monaural code and the extension code are input. The decoding device 222-m obtains a decoded digital audio signal of two channels corresponding to the input monaural code and the extension code, or the input monaural code, for each frame, and outputs it to the reproducing unit 223-m.

[0228] <Modification of Eighth Embodiment>

[0229] The above description is about the sound signal receiving side device 220-m and its operation of the eighth embodiment based on the structure of the sound signal receiving side device 220-m of the first embodiment, but the sound signal receiving side device 220-m of the eighth embodiment based on any of the sound signal receiving side devices 220-m from the third embodiment to the fifth embodiment and their modified examples can also be configured to operate. In addition, in the above example, the time from the start of receiving the first code string to the reception of a predetermined number of first code strings is used as the prescribed time range, but the prescribed time range can be set at any time. For example, the interval starting from a certain time after the start of receiving the first code string can be used as the prescribed time range, and the interval starting from each of multiple times after the start of receiving the first code string can be set as the prescribed time range.

[0230] 〔Effect〕

[0231] According to the eighth embodiment, a large error in the signal segmentation between channels of the decoded sound signal is suppressed when the difference between the time when the first code string of the same frame is received from the first communication line and the time when the second code string is received from the second communication line is large, and a high-quality decoded sound signal is obtained when the above-mentioned difference is small.

[0232] <Ninth embodiment>

[0233] In a multi-site control unit (MCU) for conducting a telephone conference at multiple sites, the digital audio signal corresponding to each of the audio signals at two different sites can be used as a two-channel digital audio signal to perform the same operation as the audio signal transmitting side device 210-m of each of the above-mentioned embodiments. This method is described as a ninth embodiment.

[0234] 《Multi-location control device 600》

[0235] like Figure 7As shown, the multi-location control device 600 includes: a receiving unit 610, a mono decoding unit 620, a location selection unit 630, a signal analysis unit 640, a mono encoding unit 650 and a transmitting unit 660. In the following, a terminal device at P locations (P is an integer greater than 3) is connected to the multi-location control device 600, and a signal from location m2 to location m is transmitted on a plurality of line corresponding terminal devices 200-m1. P The multi-location control device 600 performs the following operation for each frame of a predetermined time interval of, for example, 20 ms. Figure 8 And the processing of steps S610 to S660 illustrated below.

[0236] [Receiving unit 610]

[0237] The receiving unit 610 receives the input of the plurality of line-compatible terminal devices 200 - m. else (else is an integer greater than or equal to 2 and less than or equal to P) P-1 first code strings output via the first communication line. The receiving unit 610 outputs the monaural code included in each of the input P-1 first code strings to the monaural decoding unit 620 (step S610).

[0238] [Monaural decoding unit 620]

[0239] The monaural decoding unit 620 decodes the P-1 monaural codes input from the receiving unit 610 using a predetermined decoding method to obtain a decoded monaural signal as a decoded digital audio signal of a monaural channel, and outputs the decoded monaural signal to the location selection unit 630 (step S620). The predetermined decoding method is as described in the first embodiment.

[0240] [Site selection unit 630]

[0241] The location selection unit 630 selects two decoded mono signals from the P-1 decoded mono signals input from the mono decoding unit 620 according to a predetermined selection criterion, and outputs them to the signal analysis unit 640 (step S630). As the predetermined selection criterion, a criterion for selecting a decoded mono signal of a location with a high degree of importance is predetermined so that the location selection unit 630 can perform the selection. For example, if the power of the sound signal is used as the selection criterion, the location selection unit 630 outputs the decoded mono signal with the largest power and the decoded mono signal with the second largest power from the input P-1 decoded mono signals to the signal analysis unit 640 for each frame.

[0242] [Signal Analysis Unit 640]

[0243] The signal analysis unit 640 obtains a monaural signal of a signal obtained by mixing the two inputted decoded monaural signals from the two inputted decoded monaural signals and outputs it to the monaural coding unit 650, and obtains a spreading code indicating a characteristic parameter, which is a parameter indicating a characteristic of a difference between the two inputted decoded monaural signals and a parameter indicating a small time variation, and outputs it to the transmitting unit 660 (step S640). The signal analysis unit 640 only needs to perform the same operation as the signal analysis unit 2121-m of the coding device 212-m of the audio signal transmitting side device 210-m of the multiple line corresponding terminal device 200-m in the first embodiment. However, in the case of the present ninth embodiment, the two inputted decoded monaural signals correspond to audio signals emitted at different locations, so as a characteristic parameter, it is better to use the information indicating the intensity difference of each frequency band shown in the second example rather than the information indicating the time difference shown in the first example of the signal analysis unit 2121-m. Alternatively, information indicating the ratio or difference between the powers of two input decoded monaural signals may be used as a feature parameter.

[0244] [Monaural encoding unit 650]

[0245] The monaural encoding unit 650 encodes the input monaural signal using a predetermined encoding method to obtain a monaural code, and outputs the code to the transmitting unit 660 (step S650). The predetermined encoding method is as described in the first embodiment.

[0246] [Transmitting unit 660]

[0247] The sending unit 660 outputs, for each frame, a first code string as a code string including a monaural code input from the monaural encoding unit 650 to a plurality of line-corresponding terminal devices 200-m1 via a first communication line, and outputs a second code string as a code string including an extended code input from the signal analysis unit 640 to a plurality of line-corresponding terminal devices 200-m1 via a second communication line (step S660).

[0248] 〔Effect〕

[0249] By making the multi-point control device 600 perform the operation of the ninth embodiment, the voice signals of two points can be reproduced in the plurality of line-compatible terminal devices 200-m1 by analogy dividing them into left and right, and it can be clearly determined whether the speech is made at any one point or at different points.

[0250] <Modification of Ninth Embodiment>

[0251] In the site selection unit 630 of the multi-site control device 600 of the ninth embodiment, two decoded monaural signals are selected using power, so that the spread code can be obtained in the site selection unit 630 instead of in the signal analysis unit 640. This method is described as a modified example of the ninth embodiment, and the differences from the ninth embodiment are described.

[0252] 《Multi-location control device 600》

[0253] like Fig. 9 As shown in FIG. 1 , the multi-site control device 600 of the modified example of the ninth embodiment includes a signal mixing unit 670 instead of the signal analyzing unit 640 included in the multi-site control device 600 of the ninth embodiment. The multi-site control device 600 performs the signal mixing unit 670 for each frame. Fig.10 6. The processing of steps S610 to S630, step S670, and step S650 to S660 illustrated in the figure. Among these, the processing substantially differs from the ninth embodiment in that step S630 is performed by the location selection unit 630 and step S670 is performed by the signal mixing unit 670. Step S660 performed by the transmission unit 660 is the same as the ninth embodiment except that the spreading code is input from the location selection unit 630 instead of the signal analysis unit 640.

[0254] [Site selection unit 630]

[0255] The location selection unit 630 selects the decoded mono signal with the largest power and the decoded mono signal with the second largest power from the P-1 decoded mono signals input from the mono decoding unit 620, and outputs them to the signal analysis unit 640. Furthermore, the ratio or difference between the powers of the two selected decoded mono signals is obtained as a characteristic parameter, and an extended code as an encoding representing the obtained characteristic parameter is obtained, which is output to the sending unit 660 (step S630).

[0256] [Signal mixing unit 670]

[0257] The signal mixing unit 670 obtains a monaural signal obtained by mixing the two input decoded monaural signals from the two input decoded monaural signals, and outputs the signal to the monaural encoding unit 650 (step S670).

[0258] In order to emphasize the analog left and right distribution of the audio signal to the two locations in the multiple line corresponding terminal device 200-m1, the location selection unit 630 may obtain information for determining the location with the larger power of the selected two decoded monaural signals as a characteristic parameter, obtain an extension code as a code representing the obtained characteristic parameter, and output it to the transmission unit 660. In this case, the extension decoding unit 2222-m1 of the decoding device 222-m1 of the audio signal receiving side device 220-m1 of the multiple line corresponding terminal device 200-m1 can obtain the decoded digital audio signal of the two channels in such a manner that the audio signal is localized at the predetermined left and right positions for each location. In this case, the signal mixing unit 670 may select the larger power of the two input decoded monaural signals and output it to the monaural encoding unit 650, or the signal mixing unit 670 may not be provided, and the location selection unit 630 may select and output only the decoded monaural signal with the largest power.

[0259] <Tenth embodiment>

[0260] In the above-mentioned embodiments and variations, for the sake of simplicity, the processing of two-channel audio signals of a plurality of line-corresponding terminal devices 200-m is described as an example. However, the number of channels is not limited thereto, and may be greater than or equal to 2. If the number of channels is set to C (C is an integer greater than or equal to 2), the above-mentioned embodiments and variations may be implemented by replacing two channels with C channels (C is an integer greater than or equal to 2).

[0261] For example, the sound pickup unit 211-m of the sound signal transmitting side device 210-m of the multiple line corresponding terminal device 200-m may include C microphones and C AD conversion units, and the encoding device 212-m of the sound signal transmitting side device 210-m of the multiple line corresponding terminal device 200-m may obtain a monaural code and an extension code from the input C-channel digital sound signals. Specifically, the encoding device 212-m may obtain a monaural code by encoding a signal obtained by mixing the input C-channel digital sound signals in a predetermined first encoding method, and obtain an extension code including a code indicating information on the difference between channels in the input C-channel digital sound signals. The information on the difference between channels in the digital sound signals corresponding to the C-channels is, for example, information on the difference between the digital sound signal corresponding to each of the C-1 channels other than the reference channel and the digital sound signal of the reference channel.

[0262] In addition, the decoding device 222-m of the sound signal receiving side device 220-m of the plurality of line corresponding devices 200-m may obtain and output the decoded digital sound signal of C channels based on the input monaural code and the extension code. Specifically, the monaural decoding unit 2221-m of the decoding device 222-m decodes the input monaural code to obtain the decoded digital sound signal of the monaural channel, and the extension decoding unit 2222-m of the decoding device 222-m regards the decoded digital sound signal of the monaural channel as a signal mixed with the decoded digital sound signals of C channels, and regards the characteristic parameter obtained based on the input extension code as information indicating the characteristics of the difference between the channels in the decoded digital sound signals of the C channels, and obtains and outputs the decoded digital sound signal of the C channels. In addition, in this case, the reproducing unit 223-m of the sound signal receiving side device 220-m of the plurality of line terminal devices 200-m may also include a maximum of C DA converters and a maximum of C speakers.

[0263] <Other embodiments>

[0264] <>

[0265] When the telephone system 100 further includes the telephone line dedicated terminal device 300 - n , the telephone line dedicated terminal device 300 - n performs a known operation as follows.

[0266] 《Telephone line dedicated terminal device 300-n》

[0267] like Fig.11 As shown, the dedicated telephone line terminal device 300-n is, for example, a conventional portable phone or a conventional smart phone, and includes a voice signal sending side device 310-n and a voice signal receiving side device 320-n. The voice signal sending side device 310-n includes a sound pickup unit 311-n, an encoding unit 312-n, and a sending unit 313-n. The voice signal receiving side device 320-n includes a receiving unit 321-n, a decoding unit 322-n, and a regeneration unit 323-n. The voice signal sending side device 310-n of the dedicated telephone line terminal device 300-n performs Fig.12 The voice signal receiving side device 320-n of the telephone line dedicated terminal device 300-n performs the processing of steps S311 to S313 as shown below. Fig.13 And the processing of steps S321 to S323 illustrated below.

[0268] [Sound signal transmission side device 310-n]

[0269] The audio signal transmitting device 310 - n obtains a first code string including a monaural code corresponding to a digital audio signal of one channel for each predetermined time interval of, for example, 20 ms, that is, for each frame, and outputs it to the first communication line 420 - n .

[0270] [[Sound Pickup Unit 311-n]]

[0271] The sound pickup unit 311-n includes a microphone and an AD conversion unit. The microphone picks up the sound generated in the spatial area around the microphone and converts it into an analog electrical signal, which is then output to the AD conversion unit. The AD conversion unit converts the input analog electrical signal into a digital sound signal such as a PCM signal with a sampling frequency of 8kHz and then outputs it. That is, the sound pickup unit 311-n outputs a digital sound signal of one channel corresponding to the sound picked up by one microphone to the encoding device 312-n (step S311).

[0272] [[Encoding device 312-n]]

[0273] The encoding device 312 - n encodes the digital audio signal of one channel input from the sound collecting unit 311 - n for each frame using the above-mentioned predetermined encoding method to obtain a monaural code, and outputs the code to the transmitting unit 313 - n (step S312 ).

[0274] [[Transmitting unit 313-n]]

[0275] The transmission unit 313 - n outputs the first code string, which is a code string including the monaural code input from the encoding device 312 - n , to the first communication channel 420 - n for each frame (step S313 ).

[0276] [Sound signal receiving device 320-n]

[0277] The audio signal receiving device 320 - n outputs audio based on the monaural code included in the first code string input from the first communication line 420 - n for each predetermined time interval of, for example, 20 ms, that is, for each frame.

[0278] [[Receiving unit 321-n]]

[0279] The receiving unit 321 - n outputs the monaural code included in the first code string input from the first communication line 420 - n to the decoding device 322 - n for each frame (step S321 ).

[0280] [[Decoding device 322-n]]

[0281] The monaural code outputted by the receiving unit 321-n is inputted to the decoding device 322-n for each frame. The decoding device 322-n decodes the inputted monaural code for each frame using the above-mentioned predetermined decoding method to obtain one decoded digital audio signal, and outputs it to the reproducing unit 323-n (step S322).

[0282] [[Regeneration Unit 323-n]]

[0283] The reproduction unit 323 - n outputs a sound corresponding to the input one decoded digital sound signal (step S323 ).

[0284] The regeneration unit 323-n includes, for example, one DA conversion unit and one speaker. The DA conversion unit converts the input decoded digital sound signal into an analog electrical signal and outputs it. The speaker generates a sound corresponding to the analog electrical signal input from the DA conversion unit. The speaker may also be a speaker provided in a stereo headset or stereo earphones. When using the speakers provided in the stereo headset or stereo earphones, that is, when using two speakers, for example, the regeneration unit 323-n inputs the electrical signal output from the DA conversion unit to the two speakers, and generates a sound (decoded sound signal) corresponding to one decoded digital sound signal from the two speakers.

[0285] 〔Effect〕

[0286] Since the same encoding method and decoding method as those of the plurality of line corresponding terminal devices 200-m are used in the telephone line dedicated terminal device 300-n, it is possible to obtain a decoded voice signal of minimum sound quality in the telephone line dedicated terminal device 300-n while ensuring compatibility, and obtain a decoded voice signal of high sound quality in the plurality of line corresponding terminal devices 200-m with a delay time that is substantially the same as that in the case of obtaining a decoded voice signal of minimum sound quality, that is, with a delay time that does not cause discomfort during two-way communication.

[0287] <<There is also a code method that is neither mono code nor extended code>>

[0288] The audio signal transmitting side device 210-m of the multiple line corresponding terminal devices 200-m can also obtain and output a code (additional code) that is neither the above-mentioned monaural code nor the above-mentioned extended code. Specifically, the encoding device 212-m also obtains the additional code and outputs it to the transmitting unit 213-m, and the transmitting unit 213-m can also output the additional code input from the encoding device 212-m to any one of the first communication line 410-m and the second communication line 510-m. The additional code is, for example, a code that represents the characteristics of the high-frequency band component of the signal after mixing the digital audio signals of the input C channels (C is an integer greater than or equal to 2).

[0289] Similarly, a code (additional code) which is neither the monaural code nor the extended code may be input to the audio signal receiving side device 220-m of the multiple line corresponding terminal devices 200-m, and the audio signal receiving side device 220-m of the multiple line corresponding terminal devices 200-m may obtain and output a decoded audio signal using the additional code. Specifically, the receiving unit 221-m may output the additional code input from any one of the first communication line 410-m and the second communication line 510-m to the decoding device 222-m, and the decoding device 222-m may obtain a decoded audio signal using the additional code input from the receiving unit 221-m.

[0290] <Program and recording medium>

[0291] The processing of each part of the multiple line corresponding terminal device 200-m can also be realized by a computer. In other words, the processing of each step of each of the encoding method in the multiple line corresponding terminal device 200-m and the decoding method in the multiple line corresponding terminal device 200-m can also be executed by a computer. In this case, the processing of each step is described by a program. Then, by executing the program on the computer, the processing of each step is realized on the computer. Fig.14 2010, input unit 2030, output unit 2040, etc. to implement the processing.

[0292] Each of the programs describing the processing contents may be recorded in a computer-readable recording medium, which may be any medium such as a magnetic recording device, an optical disk, a magneto-optical recording medium, or a semiconductor memory.

[0293] Furthermore, the processing of each part may be configured by executing a predetermined program on a computer, or at least a part of the processing may be realized by hardware.

[0294] In addition, it is needless to say that appropriate changes can be made without departing from the spirit and scope of the present invention.

Claims

1. A method for receiving and decoding a sound signal, which is a method for receiving and decoding a sound signal performed by a terminal device connected to a first communication line and a second communication line having a lower priority than the first communication line, comprising: A receiving step, for a predetermined frame among a plurality of frames, outputting a monaural code included in a first code string input from the first communication channel and an extended code whose frame number is closest to the frame number of the monaural code among extended codes included in a second code string input from the second communication channel, and for a frame other than the predetermined frame, outputting the monaural code included in the first code string input from the first communication channel and the latest extended code among the extended codes that have been output; as well as The decoding step obtains and outputs C channels of decoded digital sound signals for each frame according to the mono code output in the receiving step and the extended code output in the receiving step, wherein C is an integer greater than or equal to 2.

2. The sound signal receiving and decoding method according to claim 1, characterized in that: The decoding step comprises: a mono decoding step of decoding the mono code outputted in the receiving step and obtaining a mono decoded digital sound signal; and In the extended decoding step, the mono decoded digital sound signal is regarded as a signal mixed with the decoded digital sound signals of C channels, and the characteristic parameters obtained based on the extended code output in the receiving step are regarded as information representing the characteristics of the difference between channels in the decoded digital sound signals of C channels, and the decoded digital sound signals of C channels are obtained and output.

3. A method for decoding a sound signal, which is a method for decoding a sound signal performed by a terminal device connected to a first communication line and a second communication line having a lower priority than the first communication line, comprising: A decoding step, for a predetermined frame among the plurality of frames, obtaining and outputting C channels of decoded digital sound signals based on a monaural code included in a first code string input from the first communication line and an extended code included in a second code string input from the second communication line, i.e., an extended code having a frame number closest to a frame number of the monaural code, wherein C is an integer greater than or equal to 2, For frames other than the predetermined frame, decoded digital audio signals of C channels are obtained and output based on the monaural code included in the first code string input from the first communication channel and the latest extension code used in the predetermined frame.

4. A method for decoding a sound signal, which is a method for decoding a sound signal performed by a terminal device connected to a first communication line and a second communication line having a lower priority than the first communication line, comprising: A mono decoding step, for each frame, decoding the mono code contained in the first code string input from the first communication line to obtain a mono decoded digital sound signal; as well as An extended decoding step, for a predetermined frame among a plurality of frames, the mono decoded digital sound signal is regarded as a signal mixed with C channels of decoded digital sound signals, wherein C is an integer greater than or equal to 2, and a characteristic parameter obtained according to an extended code is regarded as information indicating a characteristic of a difference between channels in the C channels of the decoded digital sound signals, and the C channels of the decoded digital sound signals are obtained and output, wherein the extended code is an extended code included in a second code string input from the second communication line, i.e., an extended code with a frame number closest to a frame number of a mono code included in a first code string input from the first communication line, For frames other than the predetermined frame, the mono decoded digital sound signal is regarded as a signal mixed with the decoded digital sound signals of C channels, and the latest feature parameters obtained in the predetermined frame are regarded as information representing the characteristics of the difference between channels in the decoded digital sound signals of the C channels, and the decoded digital sound signals of the C channels are obtained and output.

5. The sound signal decoding method according to claim 4, characterized in that: The characteristic parameter in the predetermined frame is an average or a weighted average of the characteristic parameter represented by the spreading code and the characteristic parameter of the past frame.

6. A sound signal receiving side device, which is a sound signal receiving side device included in a terminal device connected to a first communication line and a second communication line having a lower priority than the first communication line, comprising: A receiving unit that outputs, for a predetermined frame among a plurality of frames, a monaural code included in a first code string input from the first communication channel and an extended code whose frame number is closest to the frame number of the monaural code in an extended code included in a second code string input from the second communication channel, and outputs, for a frame other than the predetermined frame, the monaural code included in the first code string input from the first communication channel and a latest extended code among the extended codes that have been output; as well as The decoding device obtains and outputs C channels of decoded digital sound signals for each frame based on the monaural code output by the receiving unit and the extended code output by the receiving unit, wherein C is an integer greater than or equal to 2.

7. The sound signal receiving device according to claim 6, characterized in that: The decoding device comprises: a mono decoding unit, which decodes the mono code to obtain a mono decoded digital sound signal; and The extended decoding unit regards the mono decoded digital sound signal as a signal mixed with the decoded digital sound signals of C channels, regards the characteristic parameters obtained according to the extended code as information representing the characteristics of the differences between channels in the decoded digital sound signals of the C channels, and obtains and outputs the decoded digital sound signals of the C channels.

8. A decoding device, which is a decoding device included in a terminal device connected to a first communication line and a second communication line having a lower priority than the first communication line, comprising: A decoding unit obtains and outputs C channels of decoded digital sound signals for a predetermined frame among a plurality of frames based on a monaural code included in a first code string input from the first communication line and an extended code included in a second code string input from the second communication line, i.e., an extended code having a frame number closest to the frame number of the monaural code, wherein C is an integer greater than or equal to 2, and obtains and outputs C channels of decoded digital sound signals for frames other than the predetermined frame based on a monaural code included in a first code string input from the first communication line and a latest extended code used in the predetermined frame.

9. A decoding device, which is a decoding device included in a terminal device connected to a first communication line and a second communication line having a lower priority than the first communication line, comprising: a monaural decoding unit that decodes the monaural code included in the first code string input from the first communication line for each frame and obtains a monaural decoded digital sound signal; as well as an extended decoding unit that regards, for a predetermined frame among a plurality of frames, the mono decoded digital sound signal as a signal in which C channels of decoded digital sound signals are mixed, wherein C is an integer greater than or equal to 2, regards a feature parameter obtained based on an extended code as information indicating a feature of a difference between channels in the decoded digital sound signals of the C channels, obtains and outputs the decoded digital sound signals of the C channels, wherein the extended code is an extended code included in a second code string input from the second communication line, i.e., an extended code having a frame number closest to a frame number of a mono code included in a first code string input from the first communication line, For frames other than the predetermined frame, the mono decoded digital sound signal is regarded as a signal mixed with the decoded digital sound signals of C channels, and the latest feature parameters obtained in the predetermined frame are regarded as information representing the characteristics of the difference between channels in the decoded digital sound signals of the C channels, and the decoded digital sound signals of the C channels are obtained and output.

10. The decoding device according to claim 9, characterized in that The characteristic parameter in the predetermined frame is an average or a weighted average of the characteristic parameter represented by the spreading code and the characteristic parameter of the past frame.

11. A computer-readable recording medium recording a program for causing a computer to execute the sound signal reception and decoding method according to claim 1 or 2.

12. A computer-readable recording medium recording a program for causing a computer to execute the sound signal decoding method according to any one of claims 3 to 5.

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