JP4706575B2 - Network communication apparatus and reception buffer control method - Google Patents

Description

  The present invention relates to a network communication device and a reception buffer control method, and more particularly to a network communication device having a VoIP function for transmitting voice over an IP network and a reception buffer control method.

  In recent years, in the FAX communication (look-in FAX communication) by the procedure of UDP [User Datagram Protocol] / RTP [Real-time Transport Protocol] which is a standard protocol used in the Internet or the like, the transmission side and the reception side are synchronized. Various techniques are disclosed.

For example, a fluctuation absorbing buffer control method and system at a network edge for adjusting the buffer depth by calculating the network delay by the difference between the arrival time calculated in advance in the packet and the time when the packet is actually obtained In addition, there is a recording medium (see, for example, Patent Document 1).
JP 2002-26969 A

  Due to an error between the A / D conversion clock (hereinafter referred to as fT) of the transmission side data and the D / A conversion clock (hereinafter referred to as fR) on the reception side, there is a problem in the reception storage memory on the reception side. Will occur. When fR> fT, an underrun may occur in the reception / storage memory, and when fR <fT, an overflow may occur in the reception / storage memory. In order to prevent such a problem, a redundant memory is used as the reception storage memory.

  However, if the reception storage memory is made too large, it may take time from the time of transmission of the command / status on the transmission side until the reception of the command on the reception side, which may result in timeout.

  Therefore, an object of the present invention is to provide a network communication apparatus and a reception buffer control method capable of preventing data loss without causing data underrun or overflow due to clock error.

In order to achieve the above object, a first aspect of the present invention is a network communication apparatus for performing data communication via a network, a storage means for temporarily storing data from a transmission terminal received via the network, and the storage means. Processing means for sequentially taking out the data from the memory and performing predetermined processing, and when the processing means performs the processing, the operating frequency of the processing means is controlled based on the amount of data temporarily stored in the storage means Frequency control means, and when the amount of data temporarily stored in the storage means exceeds a preset first upper limit value, the frequency control means determines the operating frequency being operated by the processing means. The amount of data temporarily stored in the storage means is set in advance between the first upper limit value and a value at which the storage means is full. When the second upper limit value is exceeded, the operating frequency during the operation of the processing means is made higher than the operating frequency, and the amount of data temporarily stored in the storage means is set to a first lower limit value set in advance. When the operating frequency of the processing means is lower than the operating frequency, the amount of data temporarily stored in the storage means is the first lower limit value and the value at which the storage means is empty. Between the first upper limit value and the first lower limit value, when the operating frequency of the processing means is lower than the operating frequency. The difference is larger than a difference between the first upper limit value and a value at which the storage means becomes full or a difference between the first lower limit value and a value at which the storage means becomes empty .

According to a second aspect of the invention, in the first aspect of the invention, the data is an audio data digital signal, and the processing means performs a process of converting the audio data digital signal into an audio data analog signal. Features.

According to a third aspect of the present invention, in the reception buffer control method for a network communication apparatus that performs data communication via a network, the data from the transmission terminal received via the network is temporarily stored in the storage means. The data is sequentially extracted from the storage means and subjected to predetermined processing, and the frequency control means controls the operating frequency of the processing means based on the amount of data temporarily stored in the storage means. When the amount of data temporarily stored in the storage means exceeds a preset first upper limit value, the operating frequency being operated by the processing means is made higher than the operating frequency, and temporarily stored in the storage means When the data amount exceeds the second upper limit value set in advance between the first upper limit value and the value at which the storage means becomes full, the processing procedure The operating frequency at which the processing means is operating when the operating frequency is further increased from the operating frequency and the amount of data temporarily stored in the storage means falls below a preset first lower limit value. Is lower than the operating frequency, and the amount of data temporarily stored in the storage means falls below a second lower limit value set in advance between the first lower limit value and the value at which the storage means becomes empty. When the processing means is operating, the operating frequency is made lower than the operating frequency, and the difference between the first upper limit value and the first lower limit value is the difference between the first upper limit value and the storage means. It is characterized by being larger than the difference between the full value or the difference between the first lower limit value and the value at which the storage means is empty .

According to a fourth aspect of the invention, in the third aspect of the invention, the data is an audio data digital signal, and the processing means performs a process of converting the audio data digital signal into an audio data analog signal. Features.

  According to the present invention, it is possible to prevent data loss without causing data underrun or overflow due to a clock error.

  Embodiments of a network communication apparatus and a reception buffer control method according to the present invention will be described below in detail with reference to the accompanying drawings.

  FIG. 1 is a diagram showing an example of a system configuration of a FAX communication system 1 to which the present invention is applied.

  As shown in FIG. 1, a transmission-side FAX apparatus (hereinafter abbreviated as a transmission side) 21 and a reception-side FAX apparatus (hereinafter abbreviated as a reception side) 22 are connected via an IP network 3. . Hereinafter, a process for transmitting FAX data by FAX communication from the transmission side 21 to the reception side 22 will be described.

  The transmission side 21 converts a FAX analog signal 4 generated by a modem or the like into a FAX digital signal 6 by an A / D conversion unit 5. Specifically, the FAX analog signal 4 is temporarily stored in the transmission / storage memory 7, and the A / D converter 5 sequentially extracts the FAX analog signal 4 from the transmission / storage memory 7 and performs A / D conversion processing (A / D conversion). The frequency fT (= f0 + Δ1)) is performed, and the FAX digital signal 6 is transmitted to the receiving side 22 via the IP network 3.

  When the reception side 22 receives the FAX digital signal 6 transmitted from the transmission side 21 via the IP network 3, the reception side 22 converts the received FAX digital signal 6 into a FAX analog signal 4 by the D / A conversion unit 8. Specifically, the FAX digital signal 6 is temporarily stored in the reception / storage memory 9, and the D / A conversion unit 8 sequentially extracts the FAX digital signal 6 from the reception / storage memory 9 and performs D / A conversion processing (D / A conversion). The frequency fR (= f0 + Δ2)) is performed, and the FAX analog signal 4 is output to a modem or the like.

  Here, when the A / D conversion frequency fT and the D / A conversion frequency fT are not synchronized, an underrun or overflow may occur in the reception accumulation memory 9.

  Therefore, in the present invention, the frequency control unit 10 on the receiving side 22 adjusts the D / A conversion frequency fR based on the data amount of the FAX digital signal 6 stored in the reception storage memory 9, thereby performing the D / A conversion processing. The amount of data stored in the reception storage memory 9 is controlled.

  FIG. 2 is a diagram illustrating the control of the D / A conversion frequency fR performed by the frequency control unit 10.

  As shown in FIG. 2, a state in which no data is stored in the reception storage memory 9 is Empty, and a state in which the data is stored to the full capacity of the reception storage memory 9 is Full. Then, accumulation of the FAX digital signal 6 in the reception / storage memory 9 starts, the data amount in the reception / storage memory 9 increases, and when the data amount reaches the D / A conversion start amount, the D / A conversion unit 8 Starts D / A conversion processing of the FAX digital signal 6. This is because if the D / A conversion process is started when the FAX digital signal 6 starts to be stored in the reception storage memory 9, an underrun may occur.

  Then, the accumulation of the FAX digital signal 6 in the reception accumulation memory 9 and the D / A conversion process of the FAX digital signal 6 by the D / A conversion unit 8 are performed in parallel.

  Here, when the data amount of the reception storage memory 9 reaches the Upper Limit, the frequency control unit 10 increases the D / A conversion frequency fR within the upper limit frequency (Δ2> 0) in consideration of the occurrence of overflow. (The frequency range Δ is −100 ppm <Δ <100 ppm). As a result, the speed of the D / A conversion process performed by the D / A converter 8 is increased, the amount of data in the reception storage memory 9 is reduced, and the occurrence of overflow can be prevented.

  Further, when the data amount of the reception accumulation memory 9 reaches the Lower Limit, the frequency control unit 10 considers the occurrence of underrun and lowers the D / A conversion frequency fR within the lower limit frequency (Δ2 <0). (The frequency range Δ is −100 ppm <Δ <100 ppm). As a result, the speed of the D / A conversion process performed by the D / A converter 8 is reduced, the amount of data in the reception storage memory 9 is increased, and the occurrence of underrun can be prevented.

  It is also possible to prepare a plurality of the upper limit and lower limit described above in stages, and to control the D / A conversion frequency fR in stages.

  FIG. 3 is a diagram illustrating the stepwise D / A conversion frequency fR control performed by the frequency control unit 10.

  As shown in FIG. 3A, Up / 2 is set between Upper Limit and Full, and Low / 2 is prepared between Lower Limit and Empty.

  Then, as shown in FIG. 3B, the D / A conversion frequency fR corresponding to the range of “Full> data amount X> Up / 2” is set to “fR_Upper_Limit”, and “Up / 2> X> Upper”. FR corresponding to the range of “Limit” is set to “fR_Upper”, fR corresponding to the range of “Upper Limit> X> Lower Limit” is set to “fR”, and “Low Limit> X> Low / 2” is set. By setting the fR corresponding to the range to “fR_Lower” and setting the fR corresponding to the range of “Low / 2> X> Empty” to “fR_Lower_Limit”, the step-by-step control of the D / A conversion frequency fR is performed. It can be carried out.

  Next, the procedure of the D / A conversion frequency fR control process performed in the network communication apparatus will be described with reference to the flowchart shown in FIG.

  The FAX data is received from the transmission side (step S401), the received FAX data is stored in the reception storage memory (step S402), and the data amount of the reception storage memory reaches the D / A conversion start amount. Then (YES in step S403), the D / A conversion unit considers and executes D / A conversion processing of FAX data (step S404).

  If the data amount in the reception storage memory exceeds the upper limit during the D / A conversion process (YES in step S405), the frequency control unit increases the D / A conversion frequency fR (step S406), and the process returns to step S404. The D / A conversion frequency fR can be controlled according to the data amount.

  In addition, when the data amount of the reception storage memory does not exceed the Upper Limit during the D / A conversion process (NO in Step S405) and falls below the Lower Limit (YES in Step S407), the frequency control unit performs the D / A conversion frequency. fR is lowered (step S408), and the process returns to step S404. The D / A conversion frequency fR can be controlled according to the data amount.

  Then, if the amount of data in the reception / storage memory does not fall below the Lower Limit during the D / A conversion process (NO in step S407) and the reception of the FAX data is completed (YES in step S409), the control processing procedure is performed. finish.

  The present invention is not limited to the embodiments described above and shown in the drawings, and can be implemented with appropriate modifications within a range not changing the gist thereof.

It is a figure which shows an example of the system configuration | structure of the FAX communication system to which this invention is applied. It is a figure explaining control of D / A conversion frequency fR which a frequency control part performs. It is a figure explaining control of the stepwise D / A conversion frequency fR which a frequency control part performs. It is a flowchart which shows the procedure of the control processing of D / A conversion frequency fR performed with a network communication apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 FAX communication system 21 FAX apparatus of transmission side 22 FAX apparatus of reception side 3 IP network 4 FAX analog signal 5 A / D conversion part 6 FAX digital signal 7 Transmission accumulation memory 8 D / A conversion part 9 Reception accumulation memory 10 Frequency control Part

Claims (4)

In a network communication device that performs data communication via a network,
Storage means for temporarily storing data from a transmission terminal received via the network;
Processing means for sequentially extracting the data from the storage means and performing predetermined processing;
A frequency control means for controlling the operating frequency of the processing means based on the amount of data temporarily stored in the storage means when the processing means performs the processing ;
The frequency control means includes
When the amount of data temporarily stored in the storage means exceeds a preset first upper limit value, the operating frequency being operated by the processing means is made higher than the operating frequency, and temporarily stored in the storage means When the data amount exceeds the second upper limit value set in advance between the first upper limit value and the value at which the storage means is full, the operating frequency at which the processing means is operating is Higher than the frequency,
When the amount of data temporarily stored in the storage means falls below a first lower limit value set in advance, the operating frequency being operated by the processing means is made lower than the operating frequency and temporarily stored in the storage means. When the data amount falls below a second lower limit value set in advance between the first lower limit value and the value at which the storage means becomes empty, the operating frequency at which the processing means is operating is Lower than the frequency,
The difference between the first upper limit value and the first lower limit value is the difference between the first upper limit value and a value at which the storage means is full, or the first lower limit value and the storage means are empty. A network communication device characterized by being larger than a difference from The data is
Audio data digital signal,
The processing means includes
The network communication apparatus according to claim 1, wherein a process of converting the audio data digital signal into an audio data analog signal is performed. In a reception buffer control method for a network communication device that performs data communication via a network,
Temporarily storing data from the transmission terminal received via the network in the storage means;
Processing means sequentially takes out the data from the storage means and performs predetermined processing,
The frequency control means controls the operating frequency of the processing means based on the amount of data temporarily stored in the storage means ,
The frequency control means includes
When the amount of data temporarily stored in the storage means exceeds a preset first upper limit value, the operating frequency being operated by the processing means is made higher than the operating frequency, and temporarily stored in the storage means When the data amount exceeds the second upper limit value set in advance between the first upper limit value and the value at which the storage means is full, the operating frequency at which the processing means is operating is Higher than the frequency,
When the amount of data temporarily stored in the storage means falls below a first lower limit value set in advance, the operating frequency being operated by the processing means is made lower than the operating frequency and temporarily stored in the storage means. When the data amount falls below a second lower limit value set in advance between the first lower limit value and the value at which the storage means becomes empty, the operating frequency at which the processing means is operating is Lower than the frequency,
The difference between the first upper limit value and the first lower limit value is the difference between the first upper limit value and a value at which the storage means is full, or the first lower limit value and the storage means are empty. A reception buffer control method for a network communication apparatus, wherein the difference is greater than The data is
Audio data digital signal,
The processing means includes
The reception buffer control method for a network communication device according to claim 3, wherein processing for converting the audio data digital signal into an audio data analog signal is performed.

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