WO2002052744A1

WO2002052744A1 - Speech transmitting device and method, speech receiving device and method, speech transmitting/receiving system and method, and recorded medium

Info

Publication number: WO2002052744A1
Application number: PCT/JP2000/009262
Authority: WO
Inventors: Mikio Maruyama; Shinichiro Tanaka
Original assignee: Mikio Maruyama; Shinichiro Tanaka
Priority date: 2000-12-26
Filing date: 2000-12-26
Publication date: 2002-07-04

Abstract

Communication quality accruing means (132) acquires quality information representing the communication quality of a telephone network (90) at predetermined intervals according to the amount of communication data TD outputted from output means (108) to the telephone network (90). Specific information acquiring means (130) determines specific information J1 on the basis of the acquired quality information and inputs the specific information J1 to frequency characteristic changing means (120). The frequency characteristic changing means (120) changes the cutoff frequency of a frequency filter (122) so that the cutoff frequency in the high frequency band lowers when the communication quality is bad according to the specific information J1. Speech signal encoding means (140) performs compression-encoding in which the amount of codes varies with the frequency characteristics according to the specific information J1.

Description

Description Voice transmitting apparatus and method, voice receiving apparatus and method, voice transmitting / receiving system and method, and recording medium

The present invention relates to a voice transmitting device and method, a voice receiving device and method, a voice transmitting and receiving system and method, and a recording medium. In particular, the present invention relates to each of the above-described devices that transmits or receives a communication voice signal via a communication network whose communication quality changes during communication. Background art

Techniques for transmitting digital voice data (voice signals) via a communication network such as an ISDN line, a digital satellite line, or the Internet have been put to practical use. On the other hand, since the communication quality of the communication network is not always constant, the quality of reproduced sound may be degraded. For example, in an Internet telephone that transmits voice data using the Internet, if the network and servers are congested due to a sudden increase in traffic and a sufficient data transmission amount cannot be secured, a reproduced signal cannot be obtained in real time. In this case, the quality of the reproduced sound is degraded, for example, the sound is interrupted.

Therefore, an object of the present invention is to provide a voice transmitting device and method, a voice receiving device and method, a voice transmitting / receiving system and method, and a recording medium that can solve the above-mentioned problems. This object is achieved by a combination of features described in independent claims in the claims. The dependent claims define further advantageous embodiments of the present invention. Disclosure of the invention

That is, according to the first embodiment of the present invention, there is provided a voice transmitting apparatus for transmitting a communication voice signal via a communication network whose communication quality changes during communication, and wherein an input input related to the communication quality of the communication network is provided. Specification to obtain specification information for changing frequency characteristics of audio signal Information acquiring means, frequency characteristic changing means for changing the frequency characteristic of the input audio signal based on the designation information acquired by the designation information acquiring means, and input sound whose frequency characteristics have been changed by the frequency characteristic changing means Audio signal encoding means for encoding a signal to generate an encoded audio signal; and output means for outputting the encoded audio signal encoded by the audio signal encoding means to a communication network as a communication audio signal. Is provided.

The designation information acquisition means may acquire information indicating the designation information input via the communication network. Alternatively, the designated information acquiring means may acquire designated information based on information indicating communication quality input via the communication network.

It is preferable that the designated information acquisition means sequentially updates the designated information at predetermined time intervals. In this case, it is preferable that the frequency characteristic changing means sequentially updates the frequency characteristic based on the sequentially updated designation information.

The designated information obtaining means may include a communication quality obtaining means for obtaining information indicating communication quality of the communication network. In this case, it is preferable that the designated information acquisition unit acquires the information based on the information indicating the communication quality acquired by the communication quality acquisition unit.

Further, in this case, the communication quality acquiring means may acquire information indicating the communication quality based on the amount of the encoded audio signal output to the communication network by the output means.

The output means may output an image signal representing an image related to the audio signal to the communication network in association with the audio signal. In this case, it is preferable that the communication quality obtaining means obtains information indicating the communication quality of the communication network based on the amount of image information output from the output means to the communication network.

In addition, it is preferable that the communication quality acquiring means acquires information indicating communication quality at predetermined time intervals. In this case, it is preferable that the designated information acquiring means sequentially updates the designated information at a predetermined time interval, and the frequency characteristic changing means sequentially updates the frequency characteristic based on the sequentially updated designated information.

It is preferable that the frequency characteristic changing unit switches the sound pressure level of the input audio signal based on the designated information acquired by the designated information acquiring unit.

The frequency characteristic changing means preferably has a frequency filter for filtering a frequency band of the input audio signal. In this case, the frequency characteristic changing means switches the cut-off frequency of the frequency filter based on the specified information obtained by the specified information obtaining means. Is preferably obtained.

Further, it is preferable that the frequency characteristic changing unit switches the cutoff frequency of the frequency filter and the sound pressure level of the input audio signal based on the designation information acquired by the designation information acquiring unit.

When switching the cutoff frequency, if the communication quality is poor, the frequency characteristic changing means may switch the cutoff frequency in a direction in which the cutoff frequency in the high frequency range of the input audio signal decreases.

Preferably, the designation information includes information for changing the encoding method of the encoded audio signal. In this case, it is preferable that the audio signal encoding unit switches the encoding method based on the specified information including information for changing the encoding method. In this case, it is preferable that the audio signal encoding means performs compression encoding in which the code amount changes according to the frequency characteristics of the audio signal whose frequency characteristics have been changed by the frequency characteristic changing means.

According to a second aspect of the present invention, there is provided a voice receiving apparatus for receiving a communication voice signal output from a voice transmitting apparatus via a communication network whose communication quality changes during communication, the voice receiving apparatus being related to the communication quality of the communication network. A designation information output means for acquiring designation information for changing a frequency characteristic of an audio signal, and outputting the acquired designation information to a communication network.

The designated information output means may output the acquired designated information to a voice transmitting device via a communication network. Alternatively, the designated information output means may output the acquired designated information to the voice transmitting device without passing through the communication network.

The designated information output means may include communication quality acquisition means for acquiring information indicating communication quality of the communication network. In this case, it is preferable that the designated information output unit acquires the designated information based on the quality information acquired by the communication quality acquiring unit.

It is preferable that the communication quality obtaining means obtains the quality information at predetermined time intervals. In this case, it is preferable that the designated information output means sequentially updates the designated information at predetermined time intervals and sequentially outputs the designated information to the communication network.

The communication quality acquiring means may acquire the quality information based on the amount of the received communication voice signal.

Alternatively, the communication quality obtaining means may be configured to: The quality information may be obtained based on the amount of the communication image signal representing the image related to the voice signal.

The communication quality obtaining means can also obtain the quality information based on the decoded audio signal obtained by decoding the communication audio signal. Alternatively, the communication quality obtaining means can obtain the quality information based on the quality of the image signal obtained by reproducing the communication image signal corresponding to the communication audio signal.

The designation information preferably includes information for changing the encoding method of the encoded audio signal. In this case, it is preferable that the designated information output means outputs the designated information including information for changing the encoding method.

According to a third aspect of the present invention, there is provided a voice transmitting / receiving system including a voice transmitting device and a voice receiving device connected via a communication network in which communication quality changes during communication, wherein the voice receiving device includes: A designation information output unit for acquiring designation information for changing a frequency characteristic of an audio signal relating to communication quality of a communication network, and outputting the acquired designation information; Frequency characteristic changing means for changing the frequency characteristics of the input audio signal input based on the specified information output from the CPU, and the input audio signal whose frequency characteristics have been changed by the frequency characteristic changing means are coded and coded. An audio signal encoding unit for generating an audio signal, and an output unit for outputting an encoded audio signal encoded by the audio signal encoding unit to a communication network as a communication audio signal.

It is preferable that the designated information output means obtains the designated information based on a communication voice signal input to the voice receiving device via the communication network or a decoded voice signal decoded in the voice receiving device.

The designated information output means may output the acquired designated information to a communication network. In this case, it is preferable that the voice transmitting device includes designation information acquisition means for acquiring the designation information output to the communication network by the designation information output means and inputting the acquired designation information to the frequency characteristic changing means.

The designated information output means can also input the acquired designated information to the frequency characteristic changing means without passing through a communication network.

It is preferable that the designation information output means sequentially updates the designation information at predetermined time intervals. In this case, the frequency characteristic changing means performs the frequency characteristic change based on the sequentially updated designation information. Is preferably updated successively.

According to a fourth aspect of the present invention, there is provided an audio transmission method for transmitting a communication audio signal via a communication network in which communication quality changes during communication, and the method for transmitting an input audio signal based on the communication quality of the communication network. A frequency characteristic is changed, an input audio signal whose frequency characteristic is changed is encoded to generate an encoded audio signal, and the encoded audio signal is output to a communication network as a communication audio signal. I do.

A voice transmission method according to a fourth aspect of the present invention is a method for obtaining designation information related to communication quality of a communication network for changing a frequency characteristic of an inputted input audio signal, and based on the acquired designation information. The frequency characteristics of the input audio signal can be changed.

In the voice transmission method according to the fourth aspect of the present invention, it is preferable that the designated information is sequentially updated at predetermined time intervals.

According to a fifth aspect of the present invention, there is provided a voice receiving method for receiving a communication voice signal transmitted from a voice transmitting device via a communication network whose communication quality changes during communication, the method being related to the communication quality of the communication network. Acquiring specified information for changing the frequency characteristics of the audio signal, and outputting the obtained specified information to the audio transmitting device via a communication network.

In the voice receiving method according to the fifth aspect of the present invention, it is preferable that the designated information is sequentially updated at predetermined time intervals.

According to a sixth aspect of the present invention, there is provided a voice transmitting / receiving method for transmitting a communication voice signal via a communication network whose communication quality changes during communication, wherein the frequency characteristic of the voice signal relates to the communication quality of the communication network. Acquiring the designated information for changing the frequency, changing the frequency characteristic of the input audio signal based on the acquired designated information, and encoding and encoding the input audio signal with the altered frequency characteristic And outputs the encoded audio signal to the communication network as a communication audio signal.

The voice transmitting / receiving method according to the sixth aspect of the present invention is a method for transmitting / receiving a communication voice signal input to a voice receiving device via a communication network or a decoded voice signal obtained by decoding a communication voice signal in the voice receiving device. It is preferable to obtain the designated information based on the specified information.

A voice transmitting and receiving method according to a sixth aspect of the present invention includes: outputting the specified information to a communication network; receiving the specified information output to the communication network; and changing a frequency characteristic based on the received specified information. Can be. The voice transmitting / receiving method according to the sixth aspect of the present invention can also receive the specified information without passing through a communication network, and change the frequency characteristics based on the received specified information.

In the voice transmitting / receiving method according to the sixth aspect of the present invention, it is preferable that the designated information is sequentially updated at predetermined time intervals.

According to the seventh aspect of the present invention, a computer-readable recording medium storing a program for causing a computer to execute an audio transmission method for transmitting a communication audio signal via a communication network in which communication quality changes during communication is stored. The program includes a procedure for acquiring designated information for changing the frequency characteristics of the input input audio signal, which relates to the communication quality of the communication network; and a program for acquiring the input audio signal based on the acquired designated information. Changing the frequency characteristic, encoding the input audio signal with the changed frequency characteristic to generate an encoded audio signal, and using the encoded audio signal as a communication audio signal. Outputting to a communication network.

According to the eighth aspect of the present invention, a program for causing a computer to execute a voice receiving method for receiving a communication voice signal output from a voice transmitting device via a communication network whose communication quality changes during communication is stored. A recording medium readable by a computer, the program comprising: a procedure for acquiring designation information for changing the frequency characteristic of an audio signal related to the communication quality of the communication network; and transmitting the acquired designation information to the communication network. And outputting to the voice transmitting device via an external device.

According to the ninth aspect of the present invention, a computer-readable recording medium storing a program for causing a computer to execute a voice transmission / reception method for transmitting a communication voice signal via a communication network in which communication quality changes during communication is stored. The program includes a procedure for acquiring designated information for changing the frequency characteristics of the audio signal, which relates to the communication quality of the communication network, and a process for acquiring the input audio signal based on the acquired designated information. Changing the frequency characteristic, encoding the input audio signal with the changed frequency characteristic to generate an encoded audio signal, and passing the encoded audio signal as a communication audio signal. Output to a communication network.

The procedure for acquiring the designated information in the ninth aspect of the present invention includes the step of decoding the communication voice signal input to the voice reception device via the communication network or the communication voice signal in the voice reception device. Preferably, the method preferably includes a procedure for acquiring designated information based on the decoded audio signal obtained by performing the decoding.

The program according to the ninth aspect of the present invention may further include a procedure of outputting the obtained designated information to a communication network, and a procedure of receiving the designated information outputted to the communication network. Alternatively, the program according to the ninth aspect of the present invention may further include a procedure for receiving the obtained designated information without passing through a communication network.

It is preferable that the program according to each of the seventh to ninth aspects of the present invention has a procedure for sequentially updating the designated information at predetermined time intervals.

The above summary of the invention does not list all of the necessary features of the present invention, and sub-combinations of these features may also be inventions. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a diagram showing three examples (A, B, C) of an embodiment of the voice transmitting / receiving system of the present invention.

FIG. 2 is a block diagram showing an internal configuration of the television phone used in the audio transmitting / receiving system shown in FIG. 1 (B).

FIG. 3 is a block diagram showing the voice transmission / reception system of the first embodiment.

FIG. 4 is a flowchart showing an example of processing at the time of communication in the voice transmitting / receiving system of the first embodiment.

FIG. 5 is a block diagram illustrating a voice transmission / reception system according to the second embodiment.

FIG. 6 is a flowchart illustrating an example of processing at the time of communication in the voice transmitting / receiving system of the second embodiment.

FIG. 7 is a block diagram showing a voice transmission / reception system according to the third embodiment.

FIG. 8 is a flowchart illustrating an example of a process at the time of communication in the voice transmitting / receiving system of the third embodiment.

FIG. 9 is a block diagram illustrating a voice transmission / reception system according to the fourth embodiment.

FIG. 10 is a flowchart illustrating an example of processing at the time of communication in the voice transmitting / receiving system of the fourth embodiment.

FIG. 11 is a block diagram showing a voice transmission / reception system according to the fifth embodiment. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described through embodiments of the present invention. However, the following embodiments do not limit the claimed invention, and all combinations of the features described in the embodiments are not limited to the claims. It is not always necessary for the solution.

FIG. 1 shows three examples (A, B, C) of the embodiment of the voice transmitting / receiving system of the present invention. The transmitting end and the receiving end are connected by a communication network. The transmitting end and the receiving end are provided with a transmitting / receiving terminal that integrally forms a transmitting device and a receiving device.

In the voice transmission / reception system 10 shown in FIG. 1 (A), a telephone 12 T or a mobile phone 14 T as an example of a transmission / reception terminal is arranged at a transmission end, and a telephone 12 R or a mobile phone as an example of a transmission / reception terminal. Telephone 14 R is located at the receiving end. A transmitting end and a receiving end are connected via a digital telephone network (for example, an ISDN line) 90 as an example of a communication network. In the voice transmission / reception system 20 shown in FIG. 1 (B), a video telephone 22 T as an example of a transmission / reception terminal is arranged at a transmission end, and a video telephone 22 R as an example of a transmission / reception terminal is arranged at a reception end. ing. The transmitting end and the receiving end are connected via the digital telephone network 90. In the voice transmitting / receiving system 30 shown in FIG. 1 (C), a personal computer 32 T as an example of a transmitting / receiving terminal is arranged at a transmitting end, and a personal computer 32 R as an example of a transmitting / receiving terminal is arranged at a receiving end. ing. The voice transmission / reception system 30 shown in FIG. 1 (C) is an Internet telephone system for performing voice communication between personal computers 32 T and 32 R via the Internet 92 which is an example of a communication network. If a server 96 managed by a provider or the like is connected to the Internet 92, a system for downloading audio data can be provided.

The digital telephone network 90 and the Internet 92 in FIGS. 1A to 1C are communication networks whose communication quality changes during communication.

FIG. 2 is a block diagram showing an internal configuration of the television telephones 22 T and 22 R used in the voice transmitting / receiving system 20 shown in FIG. Each of the videophones 2 2 Τ and 2 2R includes a videophone transmission device 100 and a videophone reception device 200. The videophone transmitting apparatus 100 includes a transmission audio section 102 for performing audio signal processing for transmission, a transmission image section 106 for performing image signal processing for transmission, and a communication data TD. Output means 108 for sending to the speech network 90. The output unit 108 associates the encoded audio data AD1 output from the transmission audio unit 102 with the image data VD1 output from the transmission image unit 106 to generate communication data TD. The videophone receiver 200 communicates via a digital telephone network 90 with a reception audio unit 202 that performs audio signal processing for reception, a reception image unit 206 that performs image signal processing for reception, and Receiving means 208 for receiving the data TD. The receiving means 208 inputs the audio data AD2 of the received communication data TD to the reception audio section 202. Also, the receiving means 208 inputs the image data VD2 of the communication data TD to the received image part 206.

FIG. 3 is a block diagram showing a specific embodiment of the voice transmitting / receiving system 20 shown in FIG. 1 (B). The transmitting end shows only the videophone transmitting device 100 of the videophone 22T, and the receiving end shows only the videophone receiving device 200 of the videophone 22R. Hereinafter, this embodiment is referred to as a first embodiment.

The transmitting voice section 102 of the videophone transmitting apparatus 100 has a receiver 110 for converting conversational sound into an input voice signal AS 1, and a frequency characteristic of an input voice signal AS 1 input from the receiver 110. Designated information acquiring means 130 for acquiring designated information J1 for changing the information. Further, the transmission audio unit 102 changes the frequency characteristic of the input audio signal AS 1 based on the specified information J 1 obtained by the specified information obtaining unit 130 and outputs digital input audio data AD 0. Speech signal coding for generating frequency-changed audio signal AD1 by coding frequency characteristic changing means 120 and input voice data AD0 whose frequency characteristics have been changed by frequency characteristic changing means 120. Means 140. The generated encoded audio signal A D 1 is input to output means 108.

The designated information acquiring means 130 acquires communication quality for acquiring quality information indicating the communication quality of the digital telephone network 90 based on the communication data TD output from the output means 108 to the digital telephone network 90. Means 1 32 are provided. The designated information obtaining means 130 obtains (determines) the specified information J 1 based on the quality information obtained by the communication quality obtaining means 13 2, and then changes the specified information J 1 to the frequency characteristic changing means 1 2 Enter 0. Note that the designation information J 1 may include information for changing the encoding method in the audio signal encoding means 140.

The communication quality obtaining means 1 3 2 is, for example, related to the traffic of the digital telephone network 90. Using the evaluation scale (traffic parameter), quality information indicating the communication quality of the digital telephone network 90 is obtained. For example, the communication quality obtaining means 13 2 may output the amount (transmission amount) of the encoded audio data AD 1 and / or the encoded audio data AD 1 output from the output means 108 to the digital telephone network 90. And quality information based on the amount of image data VD1 (transmission amount) corresponding to. For example, the difference between the maximum possible traffic volume of the digital telephone network 90 and the actual traffic volume of other communications is determined. If the obtained difference is smaller than the amount of the encoded voice data AD1 that the output means 108 intends to output to the digital telephone network 90, it can be determined that the communication quality is poor. In this case, the obtained difference or the result of the above determination may be used as the quality information.

The frequency characteristic changing means 120 is a digital frequency filter for filtering the frequency band of the input audio data after obtaining the digital input audio data by A / D converting the analog input audio signal AS1. With 2. The frequency filter 122 has a switching tap for switching the cutoff frequency in accordance with each cutoff frequency. The frequency characteristic changing means 120 switches the frequency band of the input audio data by changing the switching tap based on the designated information J1 inputted from the designated information acquiring means 130. Note that the frequency characteristic changing means 120 may have a large number of frequency filters with different cutoff frequencies. In this case, the frequency characteristic changing means 120 switches the frequency band of the input voice data by properly using a frequency filter based on the designated information J1. Note that the frequency filter 122 may be an analog filter.

The audio signal encoding means 140 performs compression encoding in which the code amount changes in accordance with the frequency characteristics of the input audio data AD0 whose frequency characteristics have been changed. If the information for changing the encoding method is included in the designated information J1, the audio signal encoding means 140 switches the encoding method based on the designated information J1.

Switching the encoding method means, for example, switching the compression ratio of the compression encoding, switching the compression encoding method, and the like. For example, when communication quality is good, compression coding is not so high (for example, about 64 kbps). In this case, the reproduced sound quality (the sound quality of the reproduced sound) is good. On the other hand, when the line is congested and the communication quality deteriorates, the compression rate is higher (for example, about 32 kbps or less). It will be compression-coded. In this case, the reproduced sound quality is reduced, but the possibility that the reproduced sound is interrupted is reduced.

When switching the compression encoding method, it is preferable to transmit information indicating the encoding method as supplementary information of the audio data. When this additional information is not transmitted to the receiving apparatus, the receiving apparatus may decode the received audio data to determine the encoding method. The transmission image section 106 of the videophone transmitting apparatus 100 has a CCD camera 160 for acquiring an image signal VS 1 representing an image during a conversation, and an image signal VS input from the CCD camera 160. 1 and an image processing means 170 for inputting the processed image data VD 1 to the output means 108.

The receiving audio section 202 of the videophone receiver 200 decodes the audio signal AS2 such as conversation sound based on the audio data AD2 input from the receiving means 208, and It has audio signal decoding means 240 for inputting the AS 2 to a sounding body 210 such as a speaker. The received image section 206 of the videophone receiver 200 reproduces an image signal VS2 representing an image during conversation based on the image data VD2 input from the receiving means 208, and An image reproducing means 270 is provided for inputting the signal VS2 to a display means 280 such as an LCD panel.

FIG. 4 is a flowchart illustrating an example of a process at the time of communication in the voice transmitting / receiving system 20 of the first embodiment. At the start of communication, first, a call is set between the videophone transmitting apparatus 100 at the transmitting end and the videophone receiving apparatus 200 at the receiving end (S110). When the call setting is completed, a call starts between the transmitting end and the receiving end (S112). When the call starts, the communication quality obtaining means 13 2 outputs quality information indicating the communication quality of the digital telephone network 90 based on the amount of communication data TD output from the output means 108 to the digital telephone network 90. Get (S1 1 4). At this time, the communication quality acquiring means 132 acquires quality information at predetermined time intervals. In the communication data TD, the encoded coded audio data AD1 output from the transmission audio unit 102 and the image data VD1 output from the transmission image unit 106 are associated with each other. Therefore, the communication quality obtaining means 132 obtains the quality information based on the transmission amount of the encoded audio data AD1 and the transmission amount of the image data VD1.

The designated information acquisition means 130 is the quality information acquired by the communication quality acquisition means 132. The designated information J1 for changing the frequency characteristic is obtained (determined) based on the information (S116). Also, the designated information obtaining means 130 determines information for changing the encoding method based on the quality information, and includes this information in the designated information J1. Since the communication quality acquiring means 132 acquires the quality information at predetermined time intervals, the designated information acquiring means 130 sequentially updates the designated information J1 at predetermined time intervals based on the quality information. Thereafter, the designated information obtaining means 130 inputs the designated information J1 to the frequency characteristic changing means 120 and the voice signal encoding means 140 (S118).

The frequency characteristic changing means 120 is based on the input designated information J 1, for example, in the range of several KHz or more, such as 2 to 4, and when the communication quality is poor, the cutoff frequency of the high frequency range of the input audio data AD 0 when the communication quality is poor. The cut-off frequency of the frequency filter 122 is switched in the direction of decreasing (S122). Since the designated information obtaining means 130 updates the designated information J1 sequentially at a predetermined time interval, the frequency characteristic changing means 120 obtains the frequency characteristic based on the sequentially updated designated information J1. Update sequentially. The frequency characteristic changing means 120 may switch the sound pressure level in a direction in which the sound pressure level of the input audio data AD0 decreases when the communication quality is poor, based on the input specification information J1. . Further, the frequency characteristic changing means 120 may switch the cutoff frequency as described above, and may switch the sound pressure level of the input audio data ASO as described above. Further, the frequency characteristic changing means 120 may switch only the sound pressure level without switching the cutoff frequency. Here, if the encoding method is, for example, variable-length encoding in which the data amount of a signal component having a low sound pressure level is reduced, if the cutoff frequency in the high frequency range is switched to a lower direction, the encoded audio data AD The data amount of 1 becomes smaller. Similarly, when the sound pressure level is switched in the direction of decreasing, the data amount of the encoded audio data A D1 decreases. Since the cutoff frequency of the high-frequency range is lowered, the important components of the audio signal, from several 100 Hz to several KHz, can be saved, and there is little possibility that listening will be disturbed during playback. ·

Next, the audio signal encoding unit 140 switches the encoding method based on the specification information J1 input from the specification information obtaining unit 120 (S122). For example, the audio signal encoding unit 140 switches the compression rate of the compression encoding or switches the compression encoding method. At this time, the audio signal encoding means 140 outputs the input whose frequency characteristics have been changed. A compression encoding is performed in which the code amount changes according to the frequency characteristics of the audio data AD0. In addition, since the designated information acquiring means 130 updates the designated information J1 sequentially at predetermined time intervals, the audio signal coding means 140 performs the frequency characteristic based on the sequentially updated designated information. Update the gender sequentially. Here, when the compression ratio is increased, the data amount of the encoded audio data AD1 decreases.

The output unit 108 associates the encoded audio data AD 1 output from the transmission audio unit 102 with the image data VD 1 output from the transmission image unit 106 to generate communication data TD. (S124). Thereafter, the output means 108 transmits the communication data TD to the videophone receiver 200 at the receiving end (S126).

Thereafter, during a call, the videophone device 100 and the videophone receiving device 200 repeat the processing from step S114 to step S126.

Here, for example, if the transfer rate of the communication data TD transmitted from the output means 108 to the digital telephone network 90 is maintained at 64 kbps, when the line is congested, the transmission end Since it is not possible to secure a sufficient transmission amount, there is a possibility that sound quality may be degraded such as an increase in noise or interruption of sound. However, according to the voice transmission / reception system of the first embodiment, since the communication quality obtaining means 13 2 obtains (examines) the quality information at predetermined time intervals, when the line is congested, for example, The frequency characteristic changing means 120 can lower the power cutoff frequency in the high frequency range, and the audio signal encoding means 140 can increase the compression ratio. That is, it is possible to synergistically reduce the amount of data required for transmitting the encoded audio data AD1. As a result, when the line is congested, the transmission rate of the communication data TD transmitted from the output means 108 to the digital telephone network 90 is reduced from the normal 64 kbps to, for example, 32 kbps, so that the sound is interrupted. The sound quality deterioration such as noise can be suppressed low.

When the amount of the image data VD1 corresponding to the encoded audio data AD1 is large, the transferable amount of the audio data is reduced by the transfer amount of the image data VD1. In other words, the transmitted audio data is affected by the data transfer amount of the image data VD1, so that the audio may be interrupted during reproduction. However, according to the audio transmission / reception system of the first embodiment, the cutoff frequency in the high frequency range can be reduced or the compression ratio can be increased according to the variable amount of transfer of the image data VD1. This Accordingly, the audio transmission / reception system of the first embodiment is not affected by the transfer amount of the image data VD1, and can avoid a possibility that audio is interrupted.

In the first embodiment, the quality information indicating the communication quality is acquired at predetermined time intervals. However, the invention is not limited to this. During the same conversation after the call setup, the quality information acquired at the start of the communication is obtained. , The cutoff frequency and the like may be switched in the same manner as described above.

FIG. 5 is a block diagram showing a voice transmission / reception system 20 according to the second embodiment. The designated information acquiring means 130 of the second embodiment receives the designated information J1 acquired by the videophone receiving device 200 via the digital telephone network 90, and changes the designated information J1 in the frequency characteristic. It differs from the first embodiment in that it is input to the means 120 and the audio signal encoding means 140.

For this purpose, the designated information obtaining means 130 includes an interface means 134 for receiving the designated information J1 inputted via the digital telephone network 90. The receiving voice section 202 of the videophone receiving apparatus 200 includes a designated information output section 230 including communication quality acquiring means 232.

FIG. 6 is a flowchart illustrating an example of a process at the time of communication in the voice transmitting / receiving system 20 of the third embodiment. The processing at the start of communication is the same as in the first embodiment (S110, S112).

When the call is started, the communication quality acquisition means 2 32 at the receiving end decodes the amount of communication data TD or voice signal transmitted from the videophone transmitting apparatus 100 via the digital telephone network 90. The quality information indicating the communication quality of the digital telephone network 90 is acquired based on the voice data AS2 decoded by the means 240 (S214). At this time, the communication quality acquiring means 232 acquires the quality information at predetermined time intervals. In the received communication data TD, encoded encoded audio data AD1 and image data VD1 are associated with each other. Therefore, the communication quality obtaining means 2 32 can obtain the quality information based on the transmission amount of the encoded audio data AD 1 and the transmission amount of the image data VD 1. Also, since the quality of the audio signal AS2 decoded by the audio signal decoding means 240 changes according to the communication quality, the communication quality acquisition means 232 outputs a digital signal based on the audio signal AS2. It is also possible to obtain quality information of the telephone network 90. Further, since the quality of the image signal VS2 reproduced by the image reproducing means 270 changes according to the communication quality, the quality of the image signal VS2 is based on the image signal VS2. Accordingly, the quality information of the digital telephone network 90 can be obtained.

The designated information output unit 230 acquires (determines) designated information J1 for changing the frequency characteristic based on the quality information acquired by the communication quality acquiring means 232. Also, the designated information output unit 230 determines information for changing the encoding method based on the quality information, and includes this information in the designated information J1. Since the communication quality obtaining means 232 obtains the quality information at predetermined time intervals, the specified information output unit 230 sequentially outputs the specified information J1 at predetermined time intervals based on the quality information. Update. Thereafter, the designated information output section 230 outputs the designated information J1 to the digital telephone network 90 (S2166). The interface means 134 of the videophone transmitting apparatus 100 receives the designated information J1 via the digital telephone network 90 (S218). Thereafter, the interface means 134 inputs the designated information J1 to the frequency characteristic changing means 120 and the audio signal coding means 140 (S118). Thereafter, the same processing as in the first embodiment is performed (S120 to S126).

According to the voice transmission / reception system of the second embodiment, as in the first embodiment, it is possible to switch the cutoff frequency and the compression ratio in the high frequency range according to the communication quality of the digital telephone network 90. Therefore, even when the communication quality is degraded, such as when the line is congested, it is possible to suppress the degradation of the sound quality such as interruption of the voice to a low level.

FIG. 7 is a block diagram showing a voice transmitting / receiving system 20 according to the third embodiment. In the third embodiment, the quality information J2 is acquired by the videophone receiving apparatus 200, and then transferred to the videophone transmitting apparatus 100 via the digital telephone network 90. 0 is different from the second embodiment in that the designated information J1 is obtained based on the transferred quality information J2. For this reason, the designated information obtaining means 130 includes an interface means 1336 for receiving the quality information J2 input via the digital telephone network 90. The receiving audio section 202 of the videophone receiving apparatus 200 includes a communication quality acquiring unit 232 for acquiring the quality information J2 as in the second embodiment.

FIG. 8 is a flowchart illustrating an example of a process at the time of communication in the voice transmitting / receiving system 20 of the third embodiment. The processing from the start of communication to the acquisition of the quality information J2 by the communication quality acquisition means 2 32 is the same as that of the second embodiment (S110, S112, S214).

Communication quality acquisition means 2 3 2 outputs quality information J 2 acquired to digital telephone network 90 Yes (S 2 1 4). The interface means 1336 of the videophone transmitting apparatus 100 receives the quality information J2 via the digital telephone network 90 (S218). Thereafter, the designated information obtaining means 130 obtains (determines) the specified information J1 based on the received quality information J2 (S116). Hereinafter, the same processing is performed as in the first and second embodiments (S118 to S126). The effects of the third embodiment are the same as those of the first and second embodiments.

FIG. 9 is a block diagram showing a voice transmission / reception system 20 of the fourth embodiment. In the audio transmission / reception system 200 of the fourth embodiment, a videophone transmission device 100 and a videophone reception device 200 are connected without using a communication network. That is, FIG. 9 shows the entirety of the videophones 22 T and 22 R as an example of the transmitting and receiving terminals. The difference from the above-described embodiments is that the specified information acquisition means 130 is not provided in the transmission audio section 102 of the videophone transmission apparatus 100.

FIG. 10 is a flowchart illustrating an example of processing at the time of communication in the voice transmitting / receiving system 20 of the fourth embodiment. The processing from the start of communication to the acquisition of the designated information J1 by the designated information output unit 230 is the same as that of the second embodiment (S110, S112, S214, S 2 1 6).

The frequency characteristic changing means 120 of the transmitting voice part 102 and the voice signal coding means 140 transmit the designated information J 1 output from the designated information output part 230 via the digital telephone network 90. Receive without receiving (S2 2 2). Note that, similarly to the above embodiments, the designated information acquiring means 130 may be provided in the transmission audio section 102. In this case, after receiving the designated information J1 output from the designated information output unit 230, the designated information obtaining means 130 converts the designated information J1 into the frequency characteristic changing means 120 and the audio signal encoding. Input to means 140. Thereafter, the same processing as in the first embodiment is performed (S120 to S126). The effects of the fourth embodiment are the same as those of the above embodiments.

FIG. 11 is a hardware configuration diagram of the voice transmission / reception system of the fifth embodiment. This embodiment is different from the first to fourth embodiments in that an electronic computer such as a personal computer or a workstation is used.

The voice transmission and reception system consists of a CPU (central processing unit) 902, ROM (read only memory) 904, RAM (random access memory) 906, communication IZF (internal Interface) 908, speakers 909, display 910, input device 912, hard disk 914, floppy disk (FD) drive 916, and CD-ROM (compact disk ROM) drive 918.

The voice transmission / reception system 20 of the present embodiment can be the same as the basic configuration and operation of each of the embodiments shown in FIGS. For example, the CPU 902 performs the same processing as the above embodiments based on programs stored in the ROM 904 and the RAM 906, which are examples of a recording medium. Communication I / F 908 mediates the transfer of communication data TD to and from a communication network such as the Internet. The speaker 909 reproduces the communication data TD transmitted from the transmission device and outputs a conversation sound. The display 910 reproduces the communication data TD and displays images and various information corresponding to the conversation sound. The user uses the input device 912 to input a telephone number or the like. The FD drive 916 reads data or a program from the floppy disk 920 and passes it to the CPU 902. The CD-ROM drive 918 reads data or a program from the CD-ROM 922 and passes it to the CPU 902. The hard disk 914 stores data or programs read by the FD drive 916 or the CD-ROM drive 918, and data created by the CPU 902 executing the programs, and stores the stored data or programs. Is read and passed to the CPU 902.

In the present embodiment, a program is read from the CD-ROM 922 having a program for configuring each functional unit of the above-described voice transmitting / receiving system and installed on the hard disk 914, and the program is read from the hard disk 914 to read the program from the CPU 902. The above function can be realized by executing.

The program may be stored on a floppy disk 920 instead of the CD-ROM 922. Further, an MO drive may be provided in the system 20, and the program may be stored in the MO, or the program may be stored in another recording medium such as a nonvolatile semiconductor memory card. Further, the system 20 may obtain and update the program by downloading the program from another server or the like via the Internet or the like.

The above program, that is, software installed on the hard disk 914 or the like The software includes, as software, each functional unit such as a transmission audio unit, similarly to each audio transmission / reception system 20 shown in FIG. 3, FIG. 5, FIG. 7, or FIG. For example, corresponding to FIG. 9, the program includes a videophone transmitting device having a transmission audio unit, a transmission image unit, and an output unit, and a videophone receiving device having a reception audio unit, a reception image unit, and a receiving unit. Is provided as software.

The recording medium storing the program is used only for manufacturing the audio transmission / reception system 20, and the manufacture and sale of such a recording medium as a business infringes the patent right based on the application. It is clear to configure.

As described above, the present invention has been described using the embodiment, but the technical scope of the present invention is not limited to the scope described in the above embodiment. It is apparent to those skilled in the art that various changes or improvements can be made to the above embodiment. It is apparent from the description of the claims that embodiments with such changes or improvements can be included in the technical scope of the present invention.

For example, each of the above embodiments is an embodiment of the voice transmission / reception system 20 shown in FIG. 1 (B). However, the present invention is not limited to this. For example, FIG. 1 (A) and FIG. Each of the above embodiments can be applied to the voice transmitting / receiving system shown. Specifically, when applied to the voice transmission / reception system 10 shown in FIG. 1 (A), a telephone transmission device with the transmission image section 106 removed is used, and a telephone reception apparatus with the reception image section 206 removed. And it is sufficient. When applied to the voice transmission / reception system 30 shown in Fig. 1 (C), the PC 32 T at the transmitting end has the function of a telephone transmitting device, and the PC 32 R at the receiving end has the function of a telephone receiving device. By doing so, it is possible to provide an Internet telephone that performs voice communication between the PCs 32T and 32R. In this case, the encoded audio data AD1 may be in, for example, MP3 (MPEG-1 AUDIO RAYER III) format. Here, in MP3, the bit rate of the audio data is set to one of 128, 192, 256, and 384 kbps. Therefore, when the compression ratio is switched according to the communication quality of the communication network in the audio signal encoding means 140 as in each of the above embodiments, 128, 192, 255, 380 From 4 kbps, the numerical value should be reduced as the communication quality decreases. Further, the frequency characteristic changing means 120 may switch the frequency filter so that the higher frequency range is cut as the communication quality decreases. In addition, an Internet videophone that performs image communication between the personal computers 32 T and 32 R in addition to voice communication may be used. A system for downloading audio data and image data from a server 96 connected to the Internet 92 may be used.

Further, in each of the above-described embodiments, after obtaining the designated information using the predetermined means, the frequency characteristics of the input audio signal are changed or the encoding method is switched based on the designated information. However, the present invention is not limited to this, and the user may manually change the frequency characteristics and the like of the input audio signal based on the communication quality of the communication network. For example, it may be judged that the communication quality of the communication network has deteriorated when the noise increases or when a break occurs while checking the reproduced sound at the receiving end. Further, in this case, the user may manually switch the frequency characteristic changing means or the like to switch the frequency characteristic or the like in a direction in which noise / interruption is reduced. Industrial applicability

As is apparent from the above description, according to the present invention, even when the communication quality is deteriorated due to line congestion or the like, sound quality deterioration such as interrupted voice can be suppressed to a low level.

Claims

The scope of the claims

1. An audio transmission device for transmitting a communication audio signal via a communication network whose communication quality changes during communication,

Designation information acquisition means for acquiring designation information for changing frequency characteristics of an input audio signal input, which relates to communication quality of the communication network;

Frequency characteristic changing means for changing a frequency characteristic of the input audio signal based on the specification information obtained by the specification information obtaining means;

Audio signal encoding means for encoding the input audio signal whose frequency characteristic has been changed by the frequency characteristic changing means to generate an encoded audio signal;

Output means for outputting the encoded audio signal encoded by the audio signal encoding means to the communication network as the communication audio signal;

A voice transmitting device comprising:

2. The designated information acquisition means acquires the designated information input via the communication network.

The voice transmitting device according to claim 1, wherein: ■

3. The specified information obtaining means obtains the specified information based on the information indicating the communication quality input via the communication network.

The voice transmitting device according to claim 1, wherein:

4. The specified information obtaining means sequentially updates the specified information at predetermined time intervals, and the frequency characteristic changing means sequentially updates the frequency characteristic based on the sequentially updated specified information. Voice transmission according to any one of claims 1 to 3

5. The designated information acquiring means has a communication quality acquiring means for acquiring information indicating communication quality of the communication network,

Acquiring the specified information based on the information indicating the communication quality acquired by the communication quality acquiring unit

The voice transmitting device according to claim 1, wherein:

6. The communication quality obtaining means, wherein the output means outputs the encoded data to the communication network. Information indicating the communication quality is obtained based on the amount of the processed audio signal.

6. The voice transmitting device according to claim 5, wherein:

7. The output means outputs an image signal representing an image related to the audio signal to the communication network in association with the audio signal,

The communication quality obtaining unit obtains information indicating communication quality of the communication network based on an amount of image information output from the output unit to the communication network.

7. The voice transmitting device according to claim 5, wherein:

8. The communication quality obtaining means obtains information indicating the communication quality at predetermined time intervals,

The specification information obtaining means sequentially updates the specification information at the predetermined time interval, and the frequency characteristic changing means sequentially updates the frequency characteristic based on the sequentially updated specification information. Voice transmission according to any one of claims 5 to 7

9. The frequency characteristic changing unit switches a sound pressure level of the input audio signal based on the designation information acquired by the designation information acquiring unit.

The voice transmitting device according to any one of claims 1 to 8, characterized in that:

10. The frequency characteristic changing means has a frequency filter that filters a frequency band of the input audio signal.

9. The voice transmitting device according to claim 1, wherein

11. The frequency characteristic changing unit switches a cut-off frequency of the frequency filter based on the designation information acquired by the designation information acquiring unit.

10. The voice transmitting device according to claim 10, wherein:

12. The frequency characteristic changing means switches a cutoff frequency of the frequency filter and a sound pressure level of the input audio signal based on the designation information acquired by the designation information acquiring means.

10. The voice transmitting device according to claim 10, wherein:

13. The voice transmitting apparatus according to claim 11, wherein the frequency characteristic changing unit switches to a direction in which a cutoff frequency in a high frequency range of the input voice signal decreases when the communication quality is poor. .

14. The designation information includes information for changing an encoding method of the encoded audio signal,

The audio signal encoding means switches the code encoding method based on the designation information including information for changing the encoding method.

The voice transmitting device according to any one of claims 1 to 13, wherein:

15. The audio signal encoding unit performs compression encoding in which the code amount changes according to the frequency characteristics of the audio signal whose frequency characteristics have been changed by the frequency characteristics changing unit.

15. The voice transmitting device according to claim 14, wherein:

1 6. An audio receiving apparatus for receiving a communication audio signal output from an audio transmitting apparatus via a communication network whose communication quality changes during communication,

Designation information output means for acquiring designation information for changing a frequency characteristic of an audio signal relating to communication quality of the communication network, and outputting the acquired designation information

A voice receiving device comprising:

17. The voice receiving device according to claim 16, wherein the specified information output means outputs the obtained specified information to the voice transmitting device via the communication network.

18. The voice receiving device according to claim 16, wherein the specified information output means outputs the obtained specified information to the voice transmitting device without passing through the communication network.

1 9. The designated information output means has communication quality acquisition means for acquiring information indicating communication quality of the communication network,

Acquiring the designated information based on the quality information acquired by the communication quality acquiring means;

The voice receiving device according to any one of claims 16 to 18, wherein:

20. The communication quality acquiring unit acquires the quality information at a predetermined time interval, and the designated information output unit sequentially updates the designated information at the predetermined time interval and sequentially outputs the designated information to the communication network. Do

10. The voice receiving device according to claim 19, wherein:

21. The communication quality acquiring means, based on the amount of the received communication voice signal, 21. The voice receiving device according to claim 19, wherein quality information is obtained.

22. The communication quality acquiring means acquires the quality information based on an amount of a communication image signal representing an image related to the communication audio signal, which is received in association with the communication audio signal. The audio receiving device according to any one of claims 19 to 21.

23. The communication quality acquisition unit according to claim 19, wherein the communication quality acquisition unit acquires the quality information based on a decoded audio signal obtained by decoding a communication audio signal. Audio receiving device.

24. The communication quality acquiring unit acquires the quality information based on the quality of a reproduced image signal obtained by reproducing a communication image signal corresponding to the communication audio signal. 9. The audio receiving device according to any one of 9 to 23.

25. The designation information includes information for changing an encoding method of the encoded audio signal,

25. The audio receiving apparatus according to claim 16, wherein the designation information output unit outputs the designation information including information for changing the encoding method.

26. A voice transmission / reception system including a voice transmission device and a voice reception device connected via a communication network in which communication quality changes during communication,

The voice receiving device includes: a specification information output unit that obtains specification information for changing a frequency characteristic of a voice signal related to communication quality of the communication network, and outputs the obtained specification information;

The audio transmitting device,

Frequency characteristic changing means for changing the frequency characteristic of the input audio signal based on the specification information output from the specification information output means,

Output means for outputting the encoded audio signal encoded by the audio signal encoding means to the communication network as the communication audio signal.

A voice transmitting / receiving system characterized by the above-mentioned.

27. The designated information output means, which is input to the voice receiving device via the communication network. Acquiring the specified information based on the communication voice signal decoded or the decoded voice signal decoded by the voice receiving device.

27. The voice transmitting / receiving system according to claim 26, wherein:

28. The designated information output means outputs the acquired designated information to the communication network, and the voice transmitting device acquires the designated information output to the communication network by the designated information output means. A designation information acquisition unit for inputting the acquired designation information to the frequency characteristic changing unit

28. The voice transmitting / receiving system according to claim 26, wherein the voice transmitting / receiving system is characterized in that:

29. The designation information output means inputs the acquired designation information to the frequency characteristic changing means without passing through the communication network.

30. The designation information output means sequentially updates the designation information at predetermined time intervals, and the frequency characteristic changing means sequentially updates the frequency characteristic based on the sequentially updated designation information. The voice transmitting and receiving system according to any one of claims 26 to 29.

31. A voice transmission method for transmitting a communication voice signal through a communication network whose communication quality changes during communication,

Changing a frequency characteristic of the input audio signal based on a communication quality of the communication network, encoding the input audio signal having the changed frequency characteristic to generate an encoded audio signal,

Outputting the encoded audio signal as the communication audio signal to the communication network;

A voice transmission method characterized by the above-mentioned.

3 2. Obtain designation information for changing the frequency characteristics of the input audio signal, which is related to the communication quality of the communication network,

Changing a frequency characteristic of the input audio signal based on the acquired designation information.

31. The voice transmission method according to claim 31, wherein:

3. The method according to claim 3, wherein the specification information is sequentially updated at predetermined time intervals. The voice transmission method described in 2.

34. A voice receiving method for receiving a communication voice signal transmitted from a voice transmission device via a communication network whose communication quality changes during communication,

Acquisition of designation information for changing the frequency characteristics of an audio signal, related to communication quality of the communication network,

Outputting the obtained designation information to the voice transmitting device via the communication network.

35. The voice receiving method according to claim 34, wherein the designation information is sequentially updated at predetermined time intervals.

36. A voice transmitting / receiving method for transmitting a communication voice signal through a communication network in which communication quality changes during communication,

Acquisition of designation information for changing the frequency characteristics of an audio signal, related to the communication quality of the communication network,

Changing the frequency characteristics of the input input audio signal based on the obtained designation information, encoding the input audio signal with the changed frequency characteristics to generate an encoded audio signal;

A voice transmission and reception method that specializes in this.

37. Obtain the specified information based on the communication voice signal input to the voice receiving device via the communication network or on a decrypted voice signal obtained by decrypting the communication voice signal in the voice receiving device. The voice transmitting / receiving method according to claim 36, wherein the voice transmitting / receiving method is performed.

38. The obtained designation information is output to the communication network, the designation information output to the communication network is received, and the frequency characteristic is changed based on the received designation information. The voice transmission / reception method described in item 36 or 37.

39. The voice transmitting / receiving method according to claim 36, wherein the specified information obtained is received without passing through the communication network, and the frequency characteristic is changed based on the received specified information. .

40. The specification information is sequentially updated at predetermined time intervals. The voice transmission and reception method described in item 1 or 6 or 39.

41. A computer-readable recording medium storing a program for causing a computer to execute an audio transmission method for transmitting a communication audio signal via a communication network whose communication quality changes during communication, wherein the program is ,

A method for acquiring designation information for changing the frequency characteristics of the input audio signal input, which relates to the communication quality of the communication network;

Based on the acquired designated information, changing the frequency characteristics of the input audio signal II;

Encoding the input audio signal whose frequency characteristics have been changed to generate an encoded audio signal;

Outputting the encoded audio signal to the communication network as the communication audio signal.

A recording medium comprising:

4 2. A computer-readable recording medium storing a program for causing a computer to execute a voice receiving method for receiving a communication voice signal output from a voice transmission device via a communication network whose communication quality changes during communication. A program for acquiring designation information for changing a frequency characteristic of an audio signal, which relates to communication quality of the communication network;

4 3. A computer-readable recording medium storing a program for causing a computer to execute an audio transmission / reception method for transmitting a communication audio signal through a communication network in which communication quality changes during communication, wherein the program is:

A procedure for obtaining designation information for changing a frequency characteristic of an audio signal, related to communication quality of the communication network;

Changing the frequency characteristics of the input audio signal based on the acquired specified information;

Encoding the input audio signal whose frequency characteristics have been changed to generate an encoded audio signal; Outputting the encoded audio signal to the communication network as the communication audio signal.

A recording medium comprising:

44. The step of acquiring the designation information is performed by decoding the communication voice signal input to the voice receiving device via the communication network or the decoded voice signal obtained by decoding the communication voice signal in the voice receiving device. Including a step of acquiring the designation information based on a signal

44. The recording medium according to claim 43, wherein:

4 5. The program is

Outputting the obtained designation information to the communication network;

Receiving the specified information output to the communication network;

The recording medium according to claim 43, further comprising:

46. The recording medium according to claim 43, wherein the program further comprises a step of receiving the acquired designated information without passing through the communication network.

47. The recording medium according to any one of claims 41 to 46, wherein the program has a procedure for sequentially updating the designated information at predetermined time intervals.