JPH09233130A - Data transmission system and data transmission control method applied to the system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve transmission processing efficiency at a transmitter side by realizing a high transfer speed of a stream at the transmitter side without interrupting the transmission of the stream in the system sending the stream from the transmitter side to a receiver side. SOLUTION: This transmission system is provided with a relay node 1 having a function of selecting either of streams SA, SB transferred from a transmission node 2 via plural transmission systems and transferring the selected stream to a reception node 3. The relay node 1 applies buffer processing to the stream SB transferred relatively at a high speed and sends one stream SA to the reception node 3, and compares phases of the frames of the streams SA, SB and switches to the stream SB from the stream SA when the phases are in matching with each other and sends the frame to the reception node 3 when they are in matching with each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data transmission system for transmitting a stream such as video data from a transmitting node to a receiving node, especially on a network.

[0002]

2. Description of the Related Art In recent years, with the development of computer network technology and communication technology for digital information, for example, video on denmand (video on demand).
Systems have been developed to realize d). In such a system, a requested video signal such as a movie is converted into digital information and transmitted from a transmission source (video server or the like) to a reception source (user terminal device or client) via a communication line on a network. Data transmission processing is required.

Digital information such as a video signal is a series of data strings (hereinafter referred to as a stream) formed in time series by a large number of data elements (data frames) called frames being sequentially generated. Such a stream is transferred from the transmission node, which is the transmission source, to the reception node, which is the reception source, at a predetermined transfer rate via the communication line on the network. At this time, the transfer rate of the stream is determined depending on the reception processing speed on the receiving node side.

Therefore, in continuous data transmission such as a stream, the transmitting node side continuously transmits the requested stream at a high transfer rate and shifts to a stream transmission process according to the next request. It cannot be processed.
That is, the transmitting node side is not released until the transmission processing of a series of streams is completed.

As a method for solving such a problem,
A method is conceivable in which a relay node is provided on the stream transmission system and the relay node temporarily buffers the stream transmitted from the transmission node in a buffer memory.
With such a system, the transmitting node can transmit the stream at a high transfer rate regardless of the reception processing speed of the receiving node. The relay node, after buffering the stream transferred from the sending node,
The data is transmitted at a transfer speed according to the reception processing speed on the receiving node side.

[0006]

As described above, for example, in a system that realizes video-on-demand,
It is necessary to construct a transmission system that transmits a stream of a series of video data strings via a communication line on a network. At this time, in order to improve the transmission efficiency of the stream and efficiently distribute the stream to a large number of receiving nodes, the transfer speed of the transmitting node side that transmits the stream should be increased so that the transmitting node side is as fast as possible. It needs to be released.

As a method of realizing this, a method in which a relay node is provided on the network and the relay node temporarily buffers the stream from the transmission node can be considered. However, in this method, the relay node sends the stream from the transmitting node to the receiving node after buffering the stream, so that the arrival of stream transmission at the receiving node is delayed. When transmitting a video stream of a movie or the like to the user side, it is necessary to continuously transmit the video stream without interruption, until the end. Therefore, in the method of simply arranging the relay node having the buffer function,
For example, it cannot be applied to a system that realizes video-on-demand.

An object of the present invention is, in a system for transmitting a stream from a transmitting side to a receiving side, realizes a high transfer rate of the stream on the transmitting side without interrupting the transmission of the stream, and a transmission on the transmitting side. It is to improve processing efficiency.

[0009]

The present invention relates to a data transmission system for transmitting a stream, which is a series of continuous data strings, from a transmitting node to a receiving node by utilizing a communication line on a network. The node is a system having a plurality of transmission systems, and a relay node having a function of selecting one of the streams transferred from the plurality of transmission systems and transferring the selected stream to the reception node.

When the transmitting node transmits the first stream and the second stream having the same content to the relay node, the transmitting node transfers the second stream at a relatively high speed. The relay node sends the first stream received from the transmitting node to the receiving node and buffers the second stream in the buffer means. Furthermore, the relay node compares the phase (time difference from the beginning of the stream) of each frame of the first stream and the second stream, and when the phases match, switches from the first stream to the second stream. , The frame at the time of the coincidence is sent to the receiving node.

With the system of such a system, the transmission node transmits the first stream and the second stream to the relay node at a high transfer rate. The relay node includes a large capacity buffer memory for buffering the second stream from the transmitting node and the first node.
The transmission process from the stream of 1 to the second stream is switched to the receiving node. Therefore, for the receiving node, the transmission of the stream is processed at a predetermined transfer rate without interruption from the start of the transmission of the stream.

On the other hand, the transmitting node transmits the first stream and the second stream to the relay node by high-speed transfer. Since the second stream is buffered by the buffer means of the relay node, the transmitting node unilaterally transmits and stops the transmission of the second stream when the transmission is completed. At this time, the relay node is the second node.
The buffer is used to buffer the stream and the transmission processing is switched from the first stream to the second stream when the phases of the frames match. That is, the relay node reads out the second stream from the buffer means and transmits it while the first stream is being transmitted. Therefore, the sending node is the second
The stream will be released from the transmission process when the stream has been transmitted at the high transfer rate and ended. As a result, the transmitting node starts the process of transmitting the stream to another receiving node, for example.

In short, according to the present invention, the transmitting node transmits the stream at a high transfer rate that does not depend on the receiving processing speed of the receiving node and then transmits the stream without interrupting the transmission of the stream to the receiving node. It will be released from processing. Therefore, it becomes possible to efficiently distribute the stream to a large number of receiving nodes.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a system configuration related to this embodiment, and FIG. 2 is a block diagram showing a configuration of a relay node related to this embodiment. (System Configuration) As shown in FIG. 1, the system of this embodiment includes a transmission node 2 arranged on a network,
The relay node 1 and the receiving node 3 have communication lines 20A, 2
Assume a stream transmission system connected via 0B. The transmission node 2 corresponds to a video server that transmits a video signal such as a movie as a video stream converted into digital information in a system that realizes video-on-demand, for example. Also, the receiving node 3
It corresponds to a user terminal device or client on the user side that consumes the received stream.

The transmitting node 2 roughly exchanges stream control information and communication control information with a stream transmission section 10 for transmitting a stream, a speed control section 11 for controlling a transfer rate of the stream. The control communication unit 12 of FIG. On the other hand, the receiving node 3 roughly divides the stream receiving unit 13 for receiving and processing the stream.
And a stream decoding display unit 14. The stream decoding display unit 14 is a component for restoring the received stream to the original video signal and reproducing it on the display screen of the display. The receiving node 3 is specifically a personal computer having a communication function and a color display.

The relay node 1 is roughly divided into a buffer unit 5 consisting of a buffer memory, a stream receiving unit 6, a stream sending unit 7, a control communication unit 8 and a stream speed control unit 9. The buffer unit 5 buffers each of the first stream SA and the second stream SB transmitted from the plurality of transmission systems of the transmission node 2 as described later (see FIG. 2). Stream receiver 6
Is the first stream SA transmitted from the transmitting node 2.
Is an element for receiving and processing each of the second stream SB and the second stream SB.

The stream sending section 7 will be described later.
It has a selection function (selector) that selects one of the first stream SA and the second stream SB and sends it to the receiving node 3. The stream sending unit 7 sends the stream selected under the control of the stream speed control unit 9 at a predetermined transfer speed. The control communication unit 8 includes the transmitting node 2
Is a component for exchanging stream control information and communication information with the receiving node 3.

Further, a control node 4 is usually provided, and the transmission node 2 and the relay node 1 are controlled by the control node 4 to execute the stream transmission processing.
The control node 4 has a transfer control unit 15 and a control communication unit 16 necessary for controlling stream transmission processing. Also, the control node 4 receives commands (forward playback command, backward playback command, etc., which will be described later) relating to stream transmission processing with the receiving node 3, and sends various guidance messages and the like. The control node 4 is not an independent element,
It may be assumed as a control element included in the relay node 1. (Configuration of Relay Node) As shown in FIG. 2, the relay node 1 of the present embodiment corresponds to a plurality of transmission systems of the transmission node 2 and a stream reception unit 6A that receives the first stream SA and its control. It has a communication unit 8A, and also has a stream receiving unit 6B for receiving the second stream SB and its control communication unit 8B. In addition, the buffer unit 5 uses the stream S
It comprises a buffer 5A for storing A and a buffer 5B for storing the stream SB. The buffer 5B is a larger capacity buffer memory than the buffer 5A,
For example, the stream SB for one movie is accumulated.

Further, the relay node 1 has a buffer 5A,
Stream reading units 21A and 21B for reading the frames SA and SB from 5B, reading position control units 22A and 22B, a selector 23, a stream transmitting unit 24, a selector control unit 25, and a stream phase measuring unit 2
It has 6A, 26B and a phase comparison unit 27. The read position control units 22A and 22B give pointers for reading frames from the buffers 5A and 5B to the stream read units 21A and 21B. In the present embodiment, the read position control unit 22B points the pointer pointed at that time according to the phase coincidence signal PE from the phase comparison unit 27, as described later.

The selector 23 responds to the selection signal from the selector control unit 25, and the stream reading units 21A and 21B.
One of the stream SA and the stream SB output from is output to the stream transmission unit 24. Under the control of the stream speed controller 9, the stream transmitter 24 sends the stream ST selected by the selector 23 to the receiving node 3 at a predetermined transfer speed. (Stream Data Structure and Phase) As described above, the relay node 1 of the present embodiment measures the phases of the streams SA and SB by the stream phase measurement units 26A and 26B, and compares the phases by the phase comparison unit 27. It has a function to do. Here, the phase means the start (head) of the stream.
Means the time difference from.

As shown in FIG. 3, the stream is composed of a large number of frames (for example, data elements which are units of image information). Each frame is composed of a frame boundary portion at the beginning, a time stamp, and a data body (BODY).
The time stamp is time information indicating a time difference from the beginning of the stream.

The stream phase measuring units 26A and 26B are
Each phase is measured based on the time stamp recorded in each frame of the streams SA and SB.
The phase comparison unit 27 includes the stream phase measurement units 26A and 26A.
The phases from B are compared, and when they match, a phase matching signal PE is output. When the phases are different, the phase comparison unit 27 outputs an instruction signal for selecting the stream SA to the selector control unit 25. (Operation of this Embodiment) Hereinafter, particularly, FIG. 2, FIG. 4, and FIG.
The operation of this embodiment will be described with reference to the flowchart of FIG.

First, the control node 4 instructs the transmission node 2 to transmit a designated stream in response to a stream transfer request from the reception node 3. In the video-on-demand system, in response to a request from the receiving node 3, the transmitting node 2 starts transferring the video stream of the designated movie name.

In this embodiment, the transmitting node 2 uses two communication lines and uses the stream SA of the same data content.
And the stream SB are transmitted (steps S1 and S2).
Here, the stream SA is transmitted by a protocol that allows a certain amount of data loss and has a small data transfer delay. On the other hand, the stream SB has a relatively large data transfer delay by a protocol including an error resending procedure, but is transmitted by a highly reliable transfer process. Therefore, as shown in FIG. 4, the transmission node transmits the stream SB to the stream SA at a delayed timing. Further, the transmitting node 2 transmits the stream SB to the stream SA at a high transfer rate. That is, the stream SA is transmitted at a transfer speed that depends on the reception processing speed of the reception node 3.

In the relay node 1, the stream receiving section 6A
When the stream SA is received from the transmitting node 2, the buffer 5A, the stream reading unit 21A, the selector 2
3. The data is transmitted to the receiving node 3 at a predetermined transfer rate via the stream transmitting unit 24. Here, the selector 23 normally operates to select the transmission of the stream SA. On the other hand, when the stream SB is received by the stream receiving unit 6B, it is accumulated in the buffer 5B (step S3). Therefore, the stream SA is transmitted to the receiving node 3 while the stream SB is transmitted with a delay and accumulated in the buffer 5B.

The phase comparing section 27 constantly compares the phases (time stamp time information) of the respective frames of the streams SA and SB output from the stream phase measuring sections 26A and 26B, and monitors whether they match. (Step S
4). That is, since the stream SB accumulated in the buffer 5B is transferred at a high speed with respect to the stream SB, it catches up at a certain point and the phases match. Frames with the same phase are the same frames in the stream. Specifically, as shown in FIG. 4, the relay node 1
In FIG. 4, the phase of the frame F5 before being sent to the receiving node 3 of the stream SA and the phase of the frame F5 of the stream SB accumulated in the buffer 5B match each other (the position shown by the arrow in FIG. 4).

The phase comparison unit 27 outputs the phase coincidence signal PE at the time of coincidence, that is, at the time when the stream SB catches up with the stream SA, and controls the switching operation of the selector 23 via the selector control 25 (step S5). Y
ES, S7). That is, the selector 23 has transmitted the stream SA until the phases match, but stops the stream SA when the phases match (step S).
5, S6).

The stream reading unit 21B specifies the frame at the time of the coincidence with the pointer from the reading position control unit 22B to which the phase coincidence signal PE is input (step S8). The stream reading unit 21B uses the buffer 5
The stream B is read from the specified frame (frame F5 shown in FIG. 4) of the stream SB and output to the selector 23 (step S9). The stream transmitter 24 sends the stream SB from the selector 23 to the receiving node 3 as the stream ST.

Therefore, as shown in FIG. 4, the receiving node 3
Includes frames F1 (A) to F1 of the first stream SA.
4 (A) is transferred, and the stream SB is further continuously transmitted.
Frame F5 (B). That is, the frame F5 (B) of the stream SA having the same phase is not transferred to the receiving node 3. When all the streams SB accumulated in the buffer 5B are read out and sent to the receiving node 3, the stream transfer ends (step S10,
S11).

As described above, according to the present embodiment, the relay node 1 initially sends the stream SA, which allows data loss to some extent, to the receiving node 3, and the highly reliable stream SB accumulated in the buffer 5B is obtained. When catching up, the stream SB is sent to the receiving node 3. Therefore, at the start of stream transfer, the stream SA can be transmitted and the highly reliable stream SB can be transmitted midway without causing data delay.

Furthermore, the transmission node 2 can transmit the requested stream SB to the relay node 1 at a high transfer rate that does not depend on the reception processing speed of the reception node 3. When the transmission node 2 finishes transmitting the stream SB, the transmission node 2 shifts to a transmission process of a stream to another reception node. Therefore, the transmitting node 2 is released from the transmitting process before the receiving process of the receiving node 3 is completed. As a result, the release of the transmitting node can be speeded up, so that the stream can be efficiently distributed to a large number of receiving nodes. The relay node 1 buffers the stream SB, but while the buffer SB is being buffered, the stream SA is sent to the receiving node 3,
The stream to be supplied to the receiving node 3 can be transferred without interruption. (Application 1 of the present embodiment) As shown in FIG. 1, the transmission node 2 can adjust the transfer rates of the streams SA and SB by the function of the stream rate control unit 11. Now, assume that the transfer rate of the stream SA is RA
When the transfer rate of the stream SB is RB,
The transfer rate of the stream SA is “RA1 ≦ RA ≦ RA2”
Adjustable within the range. Further, the transfer rate of the stream SB can be adjusted within the range of “RB1 ≦ RB ≦ RB2”. In the case of the above-described present embodiment, RA is a fixed value and “RA1 = RA2”.

In this case, "RA1 <RB2" and "RB
It is assumed that the transfer rates of the streams SA and SB are set to 1 <RA2 ”. That is, the transfer rate RB1 is the minimum value and the transfer rate RB2 is the maximum value.
Further, the phases of the streams SA and SB are φA,
φB. That is, φA and φB are time stamp values of the latest frame received by the relay node 1.

When the relay node 1 switches the stream SA to the stream SB, if the phase of the stream SB is advanced (φA <φB) based on the comparison result of the phase comparison unit 27, the stream SA Transfer rate RA
Is changed to a value larger than the minimum value RB1, and the stream S
The transmission node 2 is instructed to change the transfer rate RB of B to the minimum value RB1 (via the control communication units 8A and 8B).

As a result, the transfer rate R of the stream SB is
Since B is smaller than the transfer rate RA of the stream SA (RB <RA), each phase φ of the streams SA and SB
The difference between A and φB approaches 0 quickly. The relay node 1 receives the stream SA when the difference between the phases φA and φB becomes zero.
To stream SB.

On the contrary, when the phase of the stream SB is delayed (φA> φB), the transfer rate RA of the stream SA is changed to a value smaller than RB2, and the stream S is changed.
The transfer rate RB of B is changed to the maximum value RB2.

As a result, the transfer rate R of the stream SB is
Since B becomes larger than the transfer rate RA of the stream SA (RB> RA), each phase φ of the streams SA and SB
The difference between A and φB approaches 0 quickly. The relay node 1 receives the stream SA when the difference between the phases φA and φB becomes zero.
To stream SB.

With such a transfer rate adjusting method, for example, when switching to the stream SB from the transmitting node having a relatively low cost, it is possible to easily switch without slipping. Therefore, the cost of the entire stream distribution can be reduced. (Application example 2 of this embodiment) Next, referring to the flowcharts of FIGS. 6 and 7, during stream transfer of this embodiment,
The operation when a transfer rate change command is given will be described. Here, the transfer speed change command is assumed to be a fast-forward reproduction mode (forward reproduction command) and a backward reproduction mode (reverse reproduction command) in the video reproduction mode. Normally, when such an instruction is issued, a process of sampling and transmitting a series of frames forming a stream is skipped at appropriate intervals in the forward direction or the backward direction.

First, in the relay node 1, the stream SA
It is assumed that the backward reproduction command is issued from the receiving node 3 via the control node 4 while being selected by the selector 23 and being sent to the receiving node 3 (YES in steps S20 to S23). Here, the output stream S when changed by a command (command for changing the transfer rate)
T (stream transferred to receiving node 3)
Is set to φ0.

The relay node 1 has, for its phase φ0,
While the phase φB of the stream SB is delayed (φ0>
φB), the buffer 5A of the stream SA is accessed to retrospectively read the frame (steps S24 and S2).
5, S26). Then, as described above, the stream S
When B catches up and the phase φB of the stream SB advances (φ0 <φB), the selector 23 is switched (YES in step S25, S29). That is, the buffer 5B
To read the frame of the stream SB retroactively and send it to the receiving node 3.

On the other hand, when the stream SB is selected by the selector 23, the switching operation of the selector 23 is not executed and the buffer 5B is accessed to retrospectively read the frame of the stream SB, and the receiving node 3 (Step S21: NO, S30, S31).

Further, it is assumed that the forward reproduction command is issued while the stream SA is selected by the selector 23 and sent to the receiving node 3 (NO in step S23, YES in S27). In this case, the relay node 1 sends the forward reproduction command to the transmitting node 2 (step S28). As a result, the transmitting node 2 executes the process of sampling and transmitting a series of frames constituting the stream SA while skipping in the forward direction at appropriate intervals, as described above.

On the other hand, it is assumed that the forward reproduction command is issued when the stream SB is selected by the selector 23 (NO in step S21, NO in step S30, S in step S30).
32 YES). The relay node 1 maintains the stream S while the phase φB of the stream SB is advanced (φ0 <φB).
The buffer 5B of B is accessed and transmitted to the receiving node 3 and the forward reproduction command is transmitted to the transmitting node 2 (steps S33 to S36). This allows
A series of frames of the stream SB accumulated in the buffer 5B is sampled and transmitted while skipping in the forward direction at appropriate intervals, and a frame transmitted by sampling is transmitted by the transmitting node 2 while skipping in the forward direction. And stores it in the buffer 5A. Then, when the phase φ0 of the output stream advances (φ0> φB), the selector 23 is switched (NO in step S34, S3).
7). That is, the buffer 5A is accessed to read the frame of the stream SA and send it to the receiving node 3.

As described above, when a fast-forward playback command (forward playback command) or a backward playback command (reverse playback command) is issued during stream transfer, the relay node 1
Responds to the maximum within the range of the streams accumulated in the buffers 5A and 5B, and when exceeding this, transmits an instruction to the original transmitting node 2. When the stream according to the command is transmitted from the transmission node 2, the relay node 1 switches from the stream from the buffer to the transmission of the stream from the transmission node. Here, as a matter of course, when the entire stream is accumulated in the buffers 5A and 5B, the process of switching to the stream from the original transmitting node 2 is not necessary.

[0044]

As described above in detail, according to the present invention, first, the transfer rate of the stream from the transmitting side is increased,
The transmitting side can be released quickly, and the requested stream can be continuously transmitted to the receiving node without delaying the arrival of the stream. Therefore, if the present invention is applied to, for example, a system that realizes video-on-demand, it becomes possible to efficiently transmit a necessary video stream and efficiently deliver it to a large number of receiving sides. Secondly, since the transfer rate of the stream from the transmitting side can be flexibly adjusted, the stream from the transmitting node having a relatively low cost can be easily switched without slipping. Therefore, the cost of the entire stream distribution can be reduced. Third,
Since it is possible to deal with the stream transfer rate change command as much as possible within the storage range of the buffer, the load on the transmission side can be reduced. Therefore, as a result, stream distribution processing can be made more efficient.

[Brief description of drawings]

FIG. 1 is a block diagram showing a system configuration related to an embodiment of the present invention.

FIG. 2 is a block diagram showing the configuration of a relay node related to this embodiment.

FIG. 3 is a conceptual diagram for explaining a stream configuration related to the present embodiment.

FIG. 4 is a timing chart for explaining the operation of the present embodiment.

FIG. 5 is a flowchart for explaining the operation of this embodiment.

FIG. 6 is a flowchart for explaining an application example of this embodiment.

FIG. 7 is a flowchart for explaining an application example of this embodiment.

[Explanation of symbols]

 1 ... Relay node 2 ... Sending node 3 ... Receiving node 4 ... Control node 5, 5A, 5B ... Buffer part 6, 6A, 6B ... Stream receiving part 7 ... Stream sending part 8, 8A, 8B ... Control communication part 9 ... Stream Speed control unit 10 ... Stream sending unit 11 ... Stream speed control unit 12 ... Control communication unit 13 ... Stream receiving unit 14 ... Stream decoding display unit 15 ... Transfer control unit 16 ... Control communication unit 20A, 20B ... Communication line 21A, 21B ... Stream reading unit 22A, 22B ... Read position control unit 23 ... Selector 24 ... Stream transmitting unit 25 ... Selector control unit 26A, 26B ... Stream phase measuring unit 27 ... Phase comparing unit

Claims (6)

[Claims] 1. A data transmission system for continuously transmitting a data string composed of a series of data elements from a transmission side to a reception side, wherein the data transmission system is provided at the transmission side and comprises a series of data elements. One data string is transmitted at a predetermined transfer rate, and a second data string consisting of the same data elements as the first data string is transmitted at a transfer rate higher than the transfer rate of the first data string. And a buffer unit for sequentially holding the second data sequence transferred from the transmission unit, and the first data sequence transferred by the transmission unit in response to the occurrence of a predetermined condition or the buffer unit. The second data string read from the buffer means is selected, and the second data string is selected, and the second data string is selected from the data elements included in the first data string and the data elements included in the second data string. Data transmission system, characterized in that it comprises a relay unit having a sending means for sending a data string continuously to the receiving side at a predetermined transfer rate that. 2. A data transmission system for continuously transmitting a data string consisting of a series of data elements from a transmission side to a reception side, wherein the data transmission system is provided on the transmission side and comprises a series of data elements. One data string is transmitted at a predetermined transfer rate, and a second data string consisting of the same data elements as the first data string is transmitted at a transfer rate higher than the transfer rate of the first data string. A transmission unit; and a relay unit that selectively sends the first data sequence or the second data sequence transferred from the transmission unit to the reception side. Said second transferred
The data element of the first data string being sent to the receiving side is compared with the data element of the second data string read from the buffer means. When the predetermined condition of each data element matches, the first data string is switched to the transmission of the second data string, and the second data string starting from the data element at the matched time is set. A data transmission system comprising control means for controlling such that the data is read from the buffer means and sent to the receiving side. 3. A relay device of a data transmission system, which receives a data string continuously transferred from a transmitting side and sends out the data string to the receiving side at a predetermined transfer rate, wherein the transmitting side transfers at a predetermined transfer rate. A first receiving means for receiving the first data string, and a data string having the same content as the first data string from the transmitting side, the transfer being faster than the transfer rate of the first data string. Second receiving means for receiving a second data string transferred at a speed; buffer means for sequentially storing the second data string received by the second receiving means in predetermined data element units; The data elements constituting the first data string received by the first receiving means are compared with the data elements constituting the second data string read from the buffer means, and the time series of the data strings is compared. In the upper position Phase comparing means for determining whether or not data elements match, and means for sending out one of the first data string or the second data string to the receiving side, wherein the phase comparing means The first data string is sent to the receiving side until the comparison result becomes a match according to the comparison result of the comparison means, and at the time when the comparison result becomes a match, the first data string is transferred to the buffer. It is provided with a sending means for switching to the second data string read from the means and sending the second data string to the receiving side with the data element corresponding to the coincident time as a head. Relay device. 4. A data transmission control method applied to a data transmission system for continuously transmitting a stream of a plurality of data frames from a transmission node to a reception node via a relay node, wherein the relay node comprises the transmission node. A first stream transferred from a node at a predetermined transfer rate and a second stream having the same content as the first stream, the second stream being transferred at a transfer rate higher than the transfer rate of the first stream. Receiving, the step of accumulating the second stream transferred from the transmitting node in a buffer memory in units of data frames, the first stream, and the second stream read from the buffer memory. Are compared on a data frame-by-data frame basis, and based on the time information included in each data frame, Performing a phase comparison of the data frame for position when the series of streams a determination is made as to whether or not to match, until the result of the phase comparison is determined to match, the first
Sending the stream to the receiving node at a predetermined transfer rate, and sending the stream to the second stream read from the buffer memory from the first stream at the time when the result of the phase comparison is determined to match. Switching and transmitting the second stream having the data frame corresponding to the determined time point to the receiving node to the receiving node, and continuing the stream to the receiving node at a predetermined transfer rate. A method for controlling data transmission, characterized in that the stream transferred at high speed from the transmitting node is accumulated in a state in which the stream is being transmitted. 5. The transmission means has a transfer adjustment means for adjusting a transfer speed of the first data string and a transfer speed of the second data string, and the relay means has the transfer data of the first data string. To a second data string for switching the transmission to the receiving side, outputting an instruction for adjusting each transfer rate of the first data string and the second data string to the transmitting means, The control means determines whether or not the respective data elements of the first data string and the second data string match at a time-series position of the data string, and until the judgment results are the same, A first data string is sent to the receiving side, and when the judgment results are in agreement, the first data string is switched to the second data string read from the buffer means and sent to the receiving side. 3. The method according to claim 2, wherein
Data transmission system as described. 6. A data transmission system for continuously transmitting a stream of a plurality of data frames from a transmission node to a reception node, wherein the transmission node is provided in the transmission node and transmits a first stream at a predetermined transfer rate. A second stream having the same content as the first stream at a transfer speed higher than the transfer speed of the first stream; and the first stream transferred from the transmitter and the first stream. The second stream is received to receive the first and second streams, respectively.
A relay node having a function of storing the first stream or the second stream selectively to the receiving node, the relay node storing the first stream. During transmission to the receiving node, a phase corresponding to a time-series data frame position of the second stream is transmitted to the receiving node in response to a backward transmission command from the receiving node. Tracing back the first stream from the first buffer memory means if it is behind the phase of the stream;
When the phase of the second stream advances, the second stream is traced back from the second buffer memory means, and when the second stream is being sent to the receiving node, In accordance with the forward transmission command of the second stream, if the phase corresponding to the time-series data frame position of the second stream leads the phase of the stream being transmitted to the receiving node, There is provided means for reading and sending the second stream from the buffer memory means, and for reading and sending the first stream from the first buffer memory means when the phase of the second stream is delayed. A data transmission system characterized in that