JPH09191314A - Continuous data transmission method and continuous data transmission device - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: In a transmission device for reproducing or displaying continuous data at the same time as a data generation time, if the data arrives at a receiving side after exceeding the time limit, transmission / reception of the next data is also within the time limit. This prevents the effect from propagating to the transmission of subsequent data. In addition, erroneous data is retransmitted only when the time limit is reached. SOLUTION: At a transmitting side, time stamp information indicating a time limit until data arrives at a receiving side and is reproduced is added to a packet header. On the receiving side, the time of the time stamp is compared with the system clock on the receiving side, and if an error is detected in the data, the packet is retransmitted only if there is a margin at the reception time limit. Does not retransmit even if there is a transmission error.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous data transmission method and a continuous data transmission apparatus for transmitting continuous data such as moving images and sounds and reproducing the same at the receiving side at the same time as the data generation time. To transmit data and play it at the same time as the data generation time is to display a 10-minute video in 10 minutes. It is not a matter of transmission delay.

[0002]

2. Description of the Related Art When, for example, moving picture information is digitally transmitted as continuous data information and is reproduced / displayed on the receiving side in real time at the same time as the data generation time, one picture which is an access unit is used as application level data. Each has a time stamp that specifies the display time. However, normally, in the transmission protocol, the transmission is performed by the following procedure without using the time stamp.

For example, FIG. 21 is a block diagram showing the role of a transmitter / receiver of TCP / IP which is a conventionally used transmission protocol. The continuous media data input from the application is divided by the packet generation unit 3 into packets of a size suitable for the TCP / IP protocol, regardless of the time information, and transmitted by the packet transmission / reception unit 5. In order to ensure the reliability of the data, the packet received by the packet transmitter / receiver 7 on the receiver side is checked for a transmission error by the packet analyzer 8, and the reception confirmation manager 9 confirms that the packet is correctly received. (ACK) is returned and the next packet is requested to be sent. Further, when a transmission error is detected, retransmission of the same packet is requested again in the confirmation of reception. Subsequently, when the transmission side receives a reception confirmation (ACK), the transmission management unit 4 instructs generation / transmission of the next packet according to the instruction. Finally, the data reproducing unit 10 rearranges the order of correctly received packets, extracts the data portion, and outputs it.

FIG. 22 shows a transmission sequence when this TCP / IP is used. For simplicity, it is assumed that one picture information is transmitted in one packet. Since the 1st packet was received correctly, the reception confirmation (ACK)
Is being sent back. Next, since the second packet detected an error at the time of reception, a retransmission request is made in the confirmation of reception, and the retransmission is performed in response to this, thereby improving the reliability of the data. Next, the third packet shows a case in which a large delay occurs on the transmission side or on the transmission path, and the third picture is not in time for the reproduction / display time limit on the reception side. Note that the transmission delay includes a case where the transmission line is congested and a case where the transmission / reception function on the transceiver is temporarily lowered. In this case, this data is not already necessary in the application on the receiving side that displays the moving image in real time, but in the TCP / IP transmission protocol, if an error is detected, a resend request is issued regardless of such time information, and then the data is transmitted correctly. Repeat retransmission until received. Therefore, such unnecessary transmission affects the transmission of the next fourth packet. In this case, even if the 4th packet is transmitted, it is already too late after the 3rd packet is correctly received. This is monitored at the application level, and the next 4th packet is sent out. You must give instructions to limit.

TIC / IP (Transmission Control Pro)
tocol / Internet Protocol) is a type of communication protocol, and uses a protocol (TCP) that defines a communication method between end nodes on the protocol (IP) that is the basis of the Internet. A sequence number is assigned to each TCP packet, and various controls such as error resending, sequence control, and flow control are performed to realize highly reliable communication. An application is assumed to be a video input and compression device that supplies compressed video data to the transmitter (that is, requests data transmission) on the transmitting side, and receives compressed video data from the receiver on the receiving side ( That is, it is assumed that a video decompression and display device (which requests data reception). The continuous media generation source 1 includes a data compression device, but is not shown. Further, the continuous media output destination 11 includes a data decompression device, but is not shown.

Next, FIG. 23 is a block diagram showing the role of a transmitter / receiver for transmission by UDP / IP which is also a transmission protocol which has been conventionally used. The continuous media data input from the application is divided by the packet generation unit 3 into packets of a size suitable for the UDP / IP protocol regardless of the time information of the data, and transmitted by the packet transmission / reception unit 5. Here, there is no guarantee for the reliability of the data, and the next data transmission is performed regardless of whether or not the data is correctly received on the receiving side. On the receiving side, the packet analysis unit 8 performs error detection on the received packet.
Even if an error is detected, the retransmission request is not issued, and only the correctly received data is output by the data reproducing unit 10.

FIG. 24 shows a transmission sequence when this UDP / IP is used. Similarly, for simplicity, it is assumed that one picture information is transmitted in one packet.
The first packet was received correctly, but the next packet was discarded as it was because an error was detected during reception.
The second data is missing. The necessary processing is lightened because reception confirmation and retransmission are unnecessary, but there is no guarantee of reliability for data. Next, the third packet has a large delay on the transmission side or on the transmission line, and is further erroneous. In this case, TCP /
Repeated retransmissions as in the case of IP do not affect the next data transmission. However, the missing data needs to be supplemented at the application level.

UDP / IP (User Datagram Protocol / I
Similarly, the nternet protocol is a combination of a protocol (UDP) that defines a communication method between end nodes on the Internet protocol (IP). There is a feature that various controls prepared by TCP are omitted, and there is no reliability, but the processing is light correspondingly.

[0009]

[Problems to be Solved by the Invention]
In the transmission method by IP, the arrival time limit required for continuous media transmission in real time cannot be performed at all, and there is a possibility that data transmission with a large delay with respect to the limited time is performed. Further, data that is no longer needed after the time limit is exceeded is transmitted including error retransmission, and the transmission band is wasted. Also, if a large delay occurs and the arrival time exceeds the time limit, the situation in which the next data transmission / reception processing cannot be performed occurs.
The effect of one piece of time limit overdue data is also propagated to subsequent data.

In this case, the upper application needs to request the transmission of data from the data which is in time next to the time limit, and further the next data is greatly separated from each other. A discontinuity will occur. Also, in UDP / IP, the influence of the transmission delay of one data is not transmitted to the following data, but it is a very unreliable protocol. For example, it is small in the communication path where cell loss may occur, such as ATM. Since a large cell loss leads to the loss of one large packet, there is room for improving reliability when there is a margin in the communication path. ATM (Asynchronous
Transfer Mode: Asynchronous Transfer Mode) is a type of transmission method located at the lower level of the communication protocol, and divides all types of information into 53-byte fixed length units called ATM cells and transmits at high speed. It has features such as high speed and multi-media information transmission, and has been attracting attention in recent years.

[0011]

[Means for Solving the Problems] In order to solve the above problems, the following measures are taken. First, the time limit information until the data arrives and is reproduced is added to the header information part of the packet to be transmitted as time stamp information, and the receiving side compares it with the system clock. When an error is detected in the data, it will be retransmitted only if the packet has a sufficient reception time limit, and will not be retransmitted even if a transmission error is detected when the time limit is exceeded at the time of reception. . When a large transmission delay occurs, if a packet that does not meet the time limit is detected based on the time stamp information, the subsequent transmission / reception processing for that packet will be stopped and the transmission / reception processing of the next packet data will be started. .

A continuous data transmission method according to the present invention is a method of transmitting continuous data generated at a transmission side to a reception side and reproducing the same at the same time as the generation time, and the steps (a) to (d) below are performed. It is characterized by including. (A) On the transmitting side, a step of generating and transmitting a packet to which a time stamp indicating the arrival time limit of data is added and transmitted (b) Step of detecting an error in the received packet (c) No error In this case, the time stamp of the received packet is read and compared with the reception time, and if it is received before the time stamp, the data is reproduced. Step (d) When an error is detected in the received packet, the time stamp is set. Read and compare with the reception time, and if the packet is received before the time stamp for the time required for retransmission, the packet is retransmitted.

Another continuous data transmission method according to the present invention is a method of transmitting continuous data generated on the transmission side to the reception side and reproducing the same at the same time as the generation time, and the following step (a): It is characterized by including ~ (c). (A) The transmitting side generates and transmits a packet to which a time stamp indicating the arrival time limit of the data is added and transmitted. (B) When an error is detected in the received packet, the packet is retransmitted. (C) A step of receiving the time stamp of the packet for which retransmission is requested and transmitting a retransmission packet if the time obtained by subtracting the time required for retransmission from the time stamp has not elapsed

A continuous data transmission apparatus according to the present invention is characterized by including the following transmitter and receiver. (A) Transmitter: a system clock indicating the time on the transmitter side, and a packet generator that uses this system clock to create a transmission packet to which a packet stamp is added with a time stamp indicating the destination arrival time of the data. A packet transmission / reception unit, a retransmission management unit that retransmits a designated packet when a retransmission request is returned (b) a receiver packet transmission / reception unit, and a packet analysis unit that detects an error in a received packet and decodes a time stamp , A time stamp comparison unit that calculates the difference between the system clock indicating the time on the receiver side and the decoded time stamp value and the time on the receiver side provided by the system clock, and a data error based on the calculated difference time. A resend determination unit that determines whether to retransmit the detected packet, and a resend request message for the specified packet Retransmission request section and data reproducing section for outputting returning the received packets into the original data to create

Another continuous data transmission apparatus according to the present invention is characterized by including the following transmitter and receiver. (A) Transmitter A system clock indicating the time on the transmitter side, a time stamp imprinting unit for adding a time stamp indicating the limitation of the destination arrival time of the data at the time of packet generation using this system clock, and a time stamp A packet generation unit that creates an added transmission packet, a packet transmission / reception unit, a packet analysis unit that decodes the time stamp of the specified packet from the resend request message, and a difference between the decoded time stamp value and the time provided by the system clock. A time stamp comparison unit that calculates, a retransmission determination unit that determines whether or not to retransmit the requested packet based on the calculated difference time, and a designated packet when the retransmission determination unit determines retransmission. (B) Receiver packet transmitter / receiver and received packet error A packet analyzer for detecting a retransmission request section for preparing a retransmission request message for the specified packet, a data reproduction unit for outputting returning the received packets into the original data,

Further, the transmitter has a priority data information section for giving priority to the packet generation section according to the importance of the packet depending on the type of data, and the retransmission judgment section has a priority data information section for making a retransmission judgment. May be weighted.

Another continuous data transmission apparatus according to the present invention is characterized by including the following transmitter and receiver. (A) Transmitter A system clock that indicates the time on the transmitter side, and a time stamp stamping unit that adds a time stamp indicating the limitation of the destination arrival time of the data at the time of packet generation using the system clock, and a time stamp A packet generator for creating the transmitted packet, a packet transmitter / receiver (b) a receiver packet transmitter / receiver, a packet analyzer for decoding the time stamp of the received packet, a system clock indicating the time on the receiver side, and the decoded The time stamp comparison unit that calculates the difference between the time stamp value and the time on the receiver side provided by the system clock, and when the time stamp comparison unit detects a packet whose time stamp value is before the time on the receiver side, the received data is discarded. Alternatively, the invalid packet monitoring unit that outputs the received packet and returns the received packet to the original data To output Te data playback unit

Further, the transmitter and the receiver may include the following items. (A) The transmitter time stamp imprinting unit further has a function of adding the same time stamp value to a plurality of packets according to the data contents. When the packet sending suppression request is received from the receiving side, the specified time stamp is added. The packet further includes an invalid packet suppression unit for stopping the subsequent generation and transmission of the owned packet. (B) Receiver The invalid packet monitoring unit receives the packet when the time stamp value is before the reception side time by the time stamp comparison unit. It has the function of discarding or outputting the already-existing data, and further requesting the transmitter side to suppress the generation and transmission of packets with the same time stamp. It further includes a transmission suppression request unit that creates a packet suppression request message.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. 1 is a block diagram showing an embodiment of a continuous data transmission apparatus according to the present invention, FIGS. 2 and 5 are operation flowcharts of a transmitter 1, FIG. 4 is a flowchart of a receiver, and FIG. 3 is a configuration diagram of a transmission packet. FIG. 4 is a diagram showing a delay time generated from the transmission side to the reception side.

As an example of a continuous media generation source on the transmission side, which is a higher-level application, moving image data with 30 images per second as an access unit is input, and is reproduced / displayed in real time as a continuous media output destination on the reception side. Shall be performed. The image data has information about the time when this image data was created for each image, and this value is added for each 1/30 second in frame units. Therefore, each image data is received by the time created at the transmission side plus the allowable delay time to the reception side by the specified time when it arrives or after the arrival in the moving picture reproduction device on the reception side. If not transmitted to the user, the data loses its value as a real-time continuous media transmission system. The system clock SC of both the transmitter and the receiver is assumed to have a capability of providing a time completely synchronized with a common radio signal from a satellite or a reference signal in a transmission path.

When the packet generator 23 in the transmitter 20 generates a communication packet (step 48 in FIG. 2), encoding is performed by adding a redundant bit to enable error detection. Further, at this time, the time stamp imprinting unit 22 takes out the information regarding the arrival time limit specified for each image or the reproduction display after arrival from the data and provides it to the packet generation unit 23 as the header information of the packet (step in FIG. 2). 47). By adding the time stamp information to the header, when the header information of the packet received on the receiving side is viewed, the information regarding the arrival time limit of the content data can be known.

On the other hand, on the receiver 30 side, the packet analysis unit 32 detects an error in the packet received by the packet transmission / reception unit, and at the same time, reads the time stamp information added in the packet (steps 64 and 6 in FIG. 4).
8), and sends it to the time stamp comparison unit 34. The time stamp comparison unit 34 compares the current time indicated by the system clock SC with the time stamp information (step 65,
69), when an error is detected in the data in the received packet (step 63), the comparison result and which packet is designated are sent to the retransmission judgment unit 36. The resend determination unit 36 resends and determines whether or not the arrival time limit is reached (step 65). In response to this, the resend request unit creates a resend request message of the designated packet, and the packet transmission / reception unit 31 causes the transmission side. (Step 67). As a criterion for the retransmission determination in the retransmission determination unit 36, if the reception time has already exceeded the arrival time limit TS, it is determined that the retransmission is unnecessary. Also, the time required for retransmission is estimated in advance (this time is Tr), and the remaining time TS− until the arrival time limit calculated by the time stamp comparison unit 34 is
The retransmission is judged by comparing with SC (step 6).
5).

When the packet transmission / reception unit receives the retransmission request message on the transmission side, it notifies the retransmission management unit 25 (steps 51 and 52), and the retransmission management unit instructs the packet generation unit 23 to specify the designated packet. It is retransmitted from 24 (steps 55 and 56).

As shown in FIG. 3, in each packet, transmission data has a packet number, a time stamp, priority information, and an error detection / correction code.

FIG. 6 shows the time required from data generation to data reproduction. Data compression time, packet generation time at the transmitter and modulation and transmission time at the transmitter / receiver, propagation time to the receiver, time at which the transmitter / receiver of the receiver demodulates to obtain a baseband signal, and packet analysis It takes time, packet disassembly time, data decompression reproduction time, etc.

The packet transmission sequence at this time is shown in FIG. The first packet has been received normally, so no acknowledgment is sent back. Next, the arrival time of the second error-detected packet is t-r (m), and the time stamp information indicating the arrival time limit of the packet is t-l.
In the case of (m), since the time limit has not yet been reached even if the estimated time Tr required for retransmission is added in the figure, it is determined to retransmit this packet and a request for retransmission is made. On the other hand, an error was detected in the packet arriving at time t-r (n) in the figure, but the time stamp information t-1 (n) indicating the arrival restriction.
Since it has already exceeded, the request for retransmission is not made.

By imparting time stamp information relating to the arrival time limit to the packet thus transmitted and determining whether or not to retransmit at the time of a transmission error based on the relationship with the arrival time, within the limit that does not impair the real-time property. It is possible to maximize the reliability of the data, prevent unnecessary retransmission that loses real-time property, and prevent the transmission of the next image data from being affected and consuming unnecessary communication bandwidth. You can

Although not shown, continuous media source 1
A data compressor is often provided between the 5 and the transmitter. The compression operation is performed by a standard system called JPEG for still images and MPEG for moving images. In addition, a data decompressor is often provided between the receiver 30 and the continuous media output destination 16.

Although it is necessary that the system clock of the transmitter and the system clock of the receiver are synchronized, they can be synchronized with a common radio signal from an artificial satellite. The reference radio wave from the satellite, the synchronization signal in the transmission path, and the like synchronize the system clocks of the respective nodes by, for example, sending time adjustment once an hour. For the reference time stamp, for example, the video frame generation interval Tc is calculated from the system clock value of the receiving side when the packet first arrives normally on the receiving side and the time stamp value of the arrived packet.
(1/30 seconds) is subtracted (that is, the time when the time stamp is set on the system clock of the transmitting side) and the one-way estimated transmission time Tr2 is added, and the result is compared with the time difference between the system clocks of the transmitting and receiving sides. To do.

However, since the first packet may be received by chance with a large delay, when the transmission / reception connection is established, a packet for time setting is created before starting the transmission of the actual data, and the above procedure is performed. Repeat several times to set. Or, start the actual data transmission and perform the above procedure to set the system clock time difference for the data for a while, and resend it after the time difference is set (while the time stamp value cannot be used for retransmission judgment etc.) It may be used for shifting to the data transfer mode with determination.

Embodiment 2 In the first embodiment, for the sake of simplicity, it is described that one image data is transmitted in one packet, but normally one image is several tens of KBytes.
There is a certain size, and in practice, it is usual to divide the communication packet into an appropriate size (variable length or fixed length) for transmission, and this will be shown below as a second embodiment.

A transmitter / receiver configuration diagram in the second embodiment is similar to that in FIG. It is assumed that moving image data of 30 frames per second is sent from the continuous media generation source 15, each image data has a size of about 40 KBytes, and the packet generation unit 23 packetizes every 4 KBytes. It has become. In this case, the packet generator 23 in the transmitter decomposes the data forming one image into about 10 pieces and packetizes each piece. At this time, the time stamp imprinting section 22 sets these 1
The packet generation unit 23 is instructed to add the same time stamp information to each of the 0 packets. On the other hand receiver 3
Within 0, the data reproducing unit 35 monitors that 10 packets having the same time stamp are gathered. If all 10 packets having the same time stamp value are gathered, it is possible that the packets were retransmitted. Are rearranged in the original order, extracted as original data, and output to the playback / display device that is the continuous media output destination 16.

In this case, the state of transmission / reception becomes a sequence as shown in FIG. However, in this case as well, as in the case of FIG. 7, there is a case where the retransmission request is made and a case where the retransmission request is not made, depending on the relationship between the reception time of the packet in which the error is detected and the arrival restriction time shown in the packet. The difference between the first embodiment and the second embodiment is that the definition of the word packet here does not have to refer to the minimum unit that flows on the physical transmission path. Therefore, when one communication packet is further decomposed into a plurality of packets (or frames or cells) and is transmitted, for example, when a 4 KBytes communication packet is further decomposed into 53 Bytes ATM cells and transmitted on the transmission line. The same effect can be obtained by applying this time stamp addition algorithm to a higher-order packet or a lower-order finer packet. This also applies to all of the following embodiments.

Embodiment 3 In the first or second embodiment, it is assumed that the system clock on the receiver side is completely synchronized with the system clock on the transmitter side by, for example, the common radio signal of the satellite or the reference signal on the transmission line. In the third embodiment described below, the system clock on the receiver side need not be completely synchronized with the system clock on the transmission side. First, the time stamp stamping unit on the transmitting side adds the time when the image data was created on the transmitting side to the packet as time stamp information. On the other hand, on the receiver side, the system clock is operated on the basis of the time stamp information of the packet which constitutes the image frame which is the continuous media data which first arrived and is correctly reproduced. That is, after that, the time of the system clock may be relatively read by the difference information from the arrival time of the packet that first arrived. In the third embodiment,
It is shown that even if the reference time referenced by the system clock in the transceiver is not absolute but relative, the same effect as in the first and second embodiments can be obtained. This also applies to all of the following embodiments.

Embodiment 4 FIG. In Embodiments 1 to 3, the time Tr expected for retransmission is estimated and prepared in advance as a retransmission determination criterion, but an example in which this is variable is shown as Embodiment 4 below. In the retransmission determination unit on the receiver side, as shown in steps 73 to 76 of FIG. 9, from the time stamp information of the received packet,
Measure the time taken from packet transmission to packet reception one by one or at regular intervals, and use the estimated retransmission time Tr expected to be retransmitted dynamically based on this measured time. To dt is a preset error value that serves as a reference for changing the value of Tr. However, when the transmitter / receiver has a relative system clock reference as shown in the third embodiment, the one-way transmission time cannot be measured in this way, but even in that case, a retransmission request is issued once. At this time, Tr may be determined by measuring the round-trip time from when the retransmission request message is created until the actual retransmission packet is transmitted, and absolute system clock synchronization is maintained. This method is also used in existing systems. By making such a device, it is possible to provide a more efficient judgment material when making a retransmission judgment than using a fixed estimation time for retransmission. is there. This also applies to all of the following embodiments.

Embodiment 5 This embodiment is an example of the case where the packet resend determination function is provided not on the receiver side but on the transmitter side in the first to fourth embodiments. FIG. 10 shows a configuration diagram of this embodiment. 11 is an operation flow chart of the receiver 40, and FIG. 12 is a packet retransmission operation flow chart of the transmitter 39. The operation flow other than the retransmission of the transmitter 39 is the same as in FIG. The difference from the first embodiment shown in FIG. 1 is that the function of performing the time stamp comparison using the system clock of the received packet and the retransmission decision based on it is deleted on the receiver 40 side. Therefore, a packet in which an error is detected on the receiving side immediately creates a retransmission request message and returns it to the transmitter 39 (steps 63, 77, 67 in FIG. 11).

On the other hand, when the transmitting side receives the retransmission request message packet, the packet analyzing section 32 first analyzes which packet the retransmission is requested (FIG. 12).
Step 79). Next, the time stamp information TS regarding the reception time limit in the packet requested to be retransmitted is compared with the system clock SC in the transmitter, and the difference result TS
-SC is notified to the retransmission decision unit 37 also in the transmitter. In the retransmission determination unit 37, this difference time information TS-SC
And the one-way estimated time Tr2 from when the packet is retransmitted to when it reaches the receiving side are compared to determine whether or not the packet is retransmitted. If TS-SC> Tr2, the resending is performed because the reception time limit is reached even if the resending is performed (steps 81 and 8 in FIG. 12).
2). Otherwise, the packet is discarded (step 83).

At this time, the time Tr2 estimated to take the retransmission may be changed dynamically from the time stamp information when the retransmission request is returned, as in the third embodiment. Further, as a retransmission determination criterion, the value obtained by adding Tr2 to the current time when performing retransmission is 1/30 seconds or more with respect to the time when the first packet is created and the transmission delay allowable time. The decision may be made based on whether or not there will be a delay.

By thus providing the transmitting side with the retransmission determining unit, it is possible to omit the execution of the retransmission determining process and the system clock which is synchronized with the transmitting side in some way on the receiving side. Especially in a system in which original transmissions must be processed simultaneously, there is an advantage that the load on the receiver side can be reduced.

Sixth Embodiment An embodiment will be described below in which the transmitter attaches priority information to packets in accordance with importance depending on the type of data, and performs weighting in accordance with priority information when making retransmission determination. In the first to fifth embodiments, the presence / absence of retransmission is determined for all data based on the same criterion. On the other hand, it is assumed that the important data and the unimportant data are ranked at the application level, and the criterion for the retransmission determination is changed accordingly. For example, as an example of moving image data, in the case of an MPEG moving image, an especially high priority is given to an intra frame (I frame) that greatly affects the preceding and subsequent data unless it is correctly transmitted in a series of image data. .
Or, in various compression methods, a small amount of header data including parameters related to the compression method in a frame in one frame data is given high priority, and other large amount of actual data is given low priority. To do.

The system configuration diagram is shown in FIG. 13, the operation flow of the transmitter is shown in FIG. 14, and the operation flow of the receiver is shown in FIG. 15, and the operation procedure is as follows. First, the packet generation unit 23 in the transmitter 41 receives the priority / non-priority information from the priority data information unit 19 in addition to the time stamp information from the time stamp imprinting unit, and packetizes it (step 85 in FIG. 14, 86). On the other hand, in the receiver, the retransmission determination unit 36 obtains information from the priority data information unit 38, which determination is performed according to the degree of priority and what weighting should be performed (step 88 in FIG. 15). However, when the retransmission determination unit is on the transmitting side as in the fifth embodiment, the function of the receiving-side priority data information unit is also used by the transmitting-side priority data information unit.

For example, it is assumed that the transmitter classifies the data into two stages of priority and non-priority. On the other hand, the method of weighting on the receiving side is also divided into two stages. For example, when a priority packet is used, retransmission is performed by retransmission determination (steps 66 and 67 in FIG. 15), but when it is non-priority, Even if a packet error is detected, the packet is discarded without being retransmitted (step 78 in FIG. 15). In this way, priority information is added to the packet according to the importance of the packet data, and the weighting of the packet retransmission judgment criterion is added by this priority information, so that effective data transmission can be performed with a minimum number of retransmission processes. Is possible.

Embodiment 7 FIG. FIG. 16 is a diagram showing an embodiment having a configuration in which a receiver monitors and discards invalid packets. FIG. 17 is an operation flow chart of the receiver. The operation flow of the transmitter is the same as in FIG. Similar to the example described in the first embodiment, as an example of the continuous media generation source 15 on the transmission side, which is a higher-level application, moving image data in which 30 images per second are used as an access unit is input, and this is continuously transmitted to the reception side. Playback / display is performed in real time as a media output destination. The image data has information about the time when this image data was created for each image, and this value is added for each 1/30 second in frame units. Therefore, each image data arrives or after the arrival by the time created by the sending side plus the allowable delay time to the receiving side. If not transmitted, the data loses its value as a real-time continuous media transmission system. In addition, it is assumed here that the system clocks of both the transmitter and the receiver have the ability to provide the time perfectly synchronized by, for example, a common radio signal from a satellite or a reference signal in the transmission path.

When the communication packet is generated by the packet generation unit 23 in the transmitter, the time stamp imprinting unit 22 extracts from the data the arrival limit time specified for each image or the reproduction display after arrival. It is provided to the packet generation unit 23 as the header information of the packet. By adding the time stamp information to the header, when the header information of the packet received on the receiving side is viewed, the information regarding the arrival time limit of the content data can be known. Further, a transmission error in the packet may occur with respect to the time stamp information. Therefore, in order to prevent this, an error correction code is specially added to the header portion including the time stamp information.

On the other hand, on the receiver 90 side, the packet transmitting / receiving unit 3
The packet analysis unit 32 reads the time stamp information TS added to the packet received by No. 1 (step 68 in FIG. 17) and sends it to the time stamp comparison unit 34. The time stamp comparison unit 34 compares the current time indicated by the system clock with the time stamp information, and compares whether the received packet is still valid in time (step 69 in FIG. 17). If the time stamped is the current system clock SC
If the value of is exceeded, this result is notified to the invalid packet monitoring unit 89.

The invalid packet monitoring unit 89, which has detected the invalid packet whose reception time limit has passed, discards the invalid packet (step 99 in FIG. 17) and, at the same time, if there is a packet that has already been effectively received, then Is output from the data reproducing unit to the continuous media output destination (step 100 in FIG. 17).

The packet transmitted in this way is provided with time stamp information TS about the arrival time limit, and when the arrival time limit is exceeded, the packet reception processing after that is stopped, and the packet data received normally before that time is stopped. Only by making the output so as not to be delayed at the time limit by waiting for the arrival of subsequent packets,
For continuous media information that requires real-time property, it is possible to prevent the real-time property from being impaired and to prevent the delay of some packets from affecting the subsequent data transmission.

Also in this embodiment, the second embodiment
Even when one piece of image data is decomposed into a plurality of packets and transmitted as shown in FIG. 4, the synchronization between the transmitter and the receiver is not absolute as shown in the fourth embodiment, but relative. No matter what, the same effect is obtained. This also applies to the following examples.

Embodiment 8 FIG. In the case where the time stamp values having the same content may be added to a plurality of packets, as shown in the second embodiment, the seventh embodiment
18 to 20 as an example 8 of a system in which a function of discarding a packet that has not arrived at the receiving side by the time limit and suppressing the transmission of a packet having the same time stamp to the transmitter is used as FIG. It is shown below.

For example, as a continuous media input source, 30 per second
It is assumed that the moving image data of the frame is sent, and each piece of image data has a size of about 40 KBytes, and the packet generation unit performs packetization every 4 KBytes. 19 is a flowchart of the transmitter, and FIG. 20 is a flowchart of the receiver.

As described in the seventh embodiment, the invalid packet monitoring unit 92 which has detected the invalid packet whose reception time limit has expired discards this invalid packet (step 99 in FIG. 20) and, at the same time, has already made it valid. If there is a packet that has been received, the data reproducing unit 35 outputs it to the continuous media output destination, and further creates a message that causes the transmission suppression requesting unit 93 to stop transmitting packets having the same time stamp value thereafter. Is instructed (steps 107 and 108 in FIG. 20). The transmission suppression requesting unit 93 sends a message to the transmitter side through the transmitting / receiving unit so as to stop the subsequent transmission of the packet having the designated time stamp value.

On the other hand, the transmitter side receiving the transmission suppression message transmits the designated time stamp value to the invalid packet suppression unit 95. The invalid packet suppression unit causes the packet generation unit to stop the subsequent transmission of the packet having the designated time stamp value that is still being generated or has not been transmitted (step 102 in FIG. 19).

The packet transmitted in this way is provided with time stamp information relating to the arrival time limit and monitored at the arrival time, and not only the reception processing of the invalid packet thereafter on the receiving side is stopped, but also on the transmitting side. By stopping the subsequent invalid packet transmission processing, it is possible to prevent the congestion state of the transmission path from affecting the subsequent data transmission that requires real-time processing.

[0054]

As described above, the present invention can eliminate the packets that exceed the reception time limit set for the data required to have real-time characteristics, and therefore have the following effects in continuous media transmission. It is possible to prevent unnecessary band consumption on the transmission path due to unnecessary retransmission.
It is possible to prevent the transmission delay of one data from spreading to the next data.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a transmitter and a receiver according to a first embodiment of the present invention.

2 is an operation flow diagram of the transmitter of FIG. 1. FIG.

FIG. 3 is a diagram showing an example of a packet of the present invention.

FIG. 4 is an operation flow diagram of the receiver of FIG.

5 is a flow chart of a retransmission operation of the transmitter of FIG.

6 is a diagram showing a time required for data transmission in the system of FIG.

FIG. 7 is an explanatory diagram of a transmission sequence according to the first embodiment.

FIG. 8 is an explanatory diagram of a transmission sequence according to the second embodiment of the present invention.

FIG. 9 is a flowchart of changing retransmission estimation time according to the fourth embodiment of the present invention.

FIG. 10 is a block diagram showing a system configuration according to a fifth embodiment of the present invention.

11 is an operational flowchart of the receiver of FIG.

12 is a retransmission operation flowchart of the transmitter of FIG.

FIG. 13 is a system configuration diagram of a sixth embodiment of the present invention.

FIG. 14 is an operational flowchart of the transmitter of FIG.

FIG. 15 is an operational flowchart of the receiver of FIG.

FIG. 16 is a system configuration diagram of a seventh embodiment of the present invention.

17 is an operation flowchart of the receiver of FIG.

FIG. 18 is a system configuration diagram of an eighth embodiment of the present invention.

FIG. 19 is an operation flowchart of the transmitter of FIG.

20 is an operation flowchart of the receiver of FIG.

FIG. 21 is a configuration diagram of an example of a conventional data transmission system.

22 is an explanatory diagram of the transmission sequence of FIG. 21. FIG.

FIG. 23 is a configuration diagram of an example of a conventional data transmission system.

FIG. 24 is an explanatory diagram of the transmission sequence of FIG. 23.

[Explanation of symbols]

16 Continuous media output destination 17 Time stamp comparison unit 18 Retransmission determination unit 19 Priority data information unit 20 Transmitter 21 System clock 22 Time stamp imprinting unit 23 Packet generation unit 24 Packet transmission / reception unit 25 Retransmission management unit 30 Receiver 31 Packet transmission / reception unit 32 Packet analysis unit 33 System clock 34 Time stamp comparison unit 35 Data reproduction unit 36 Retransmission determination unit 37 Retransmission request unit 38 Priority data information unit 39 Transmitter 40 Receiver 41 Transmitter 42 Receiver 89 Invalid packet monitoring unit 90 Receiver 91 Transmission Device 93 Transmission suppression request unit 94 Receiver 95 Invalid packet suppression unit 96 Transmitter

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Minoru Ozaki 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Sanryo Electric Co., Ltd.

Claims (7)

[Claims] 1. A method of transmitting continuous data generated by a transmitting side to a receiving side and reproducing the same at the same time as the generation time,
A continuous data transmission method including the following steps (a) to (d). (A) On the transmitting side, a step of generating and transmitting a packet to which a time stamp indicating the arrival time limit of data is added and transmitted (b) Step of detecting an error in the received packet (c) No error In this case, the time stamp of the received packet is read and compared with the reception time, and if it is received before the time stamp, the data is reproduced. Step (d) When an error is detected in the received packet, the time stamp is set. Read and compare with the reception time, and if the packet is received before the time stamp for the time required for retransmission, the packet is retransmitted. 2. A method of transmitting continuous data generated by a transmitting side to a receiving side and reproducing the same at the same time as the generation time,
A continuous data transmission method including the following steps (a) to (c): (a) A step of generating and transmitting a packet with a time stamp indicating a limitation of the arrival time of data at the transmitting side at the transmitting side (b) ) When an error is detected in the received packet, the step of requesting retransmission of the packet is performed. (C) The time stamp of the packet requested to be retransmitted is read, and the time obtained by subtracting the time required for retransmission from the time stamp has elapsed. If not, step to send retransmitted packet 3. A continuous data transmission device comprising the following transmitter and receiver. (A) Transmitter A system clock indicating the time on the transmitter side, and a time stamp imprinting unit for adding a time stamp indicating the limitation of the destination arrival time of the data at the time of packet generation using this system clock, and a time stamp A packet generation unit that creates an added transmission packet, a packet transmission / reception unit, and a retransmission management unit that retransmits a designated packet when a retransmission request is returned. (B) Receiver packet transmission / reception unit, detects an error in a received packet Then, a packet analysis unit for decoding the time stamp, a system clock indicating the time on the receiver side, and a time stamp comparison unit for calculating the difference between the decoded time stamp value and the time on the receiver side provided by the system clock, Based on the calculated difference time, it is determined whether to retransmit the packet in which a data error is detected. Retransmission determination unit and a retransmission request section for preparing a retransmission request message for the specified packet, the data reproduction unit for outputting returning the received packets into the original data 4. A continuous data transmission device comprising the following transmitter and receiver. (A) Transmitter A system clock indicating the time on the transmitter side, a time stamp imprinting unit for adding a time stamp indicating the limitation of the destination arrival time of the data at the time of packet generation using this system clock, and a time stamp A packet generation unit that creates an added transmission packet, a packet transmission / reception unit, a packet analysis unit that decodes the time stamp of the specified packet from the resend request message, and a difference between the decoded time stamp value and the time provided by the system clock. A time stamp comparison unit that calculates, a retransmission determination unit that determines whether or not to retransmit the requested packet based on the calculated difference time, and a designated packet when the retransmission determination unit determines retransmission. (B) Receiver packet transmitter / receiver and received packet error A packet analyzer for detecting a retransmission request section for preparing a retransmission request message for the specified packet, a data reproduction unit for outputting returning the received packets into the original data, 5. The transmitter further includes a priority data information section for giving a priority to the packet generation section according to the importance of the packet depending on the type of data, and further has a retransmission determination section and a priority data information section for retransmission. The continuous data transmission device according to claim 3 or 4, wherein weighting is performed in the determination. 6. A continuous data transmission device comprising the following transmitter and receiver. (A) Transmitter A system clock indicating the time on the transmitter side, and a time stamp imprinting unit for adding a time stamp indicating the limitation of the destination arrival time of the data at the time of packet generation using the system clock, and a time stamp addition A packet generator for creating the transmitted packet, a packet transmitter / receiver (b) a receiver packet transmitter / receiver, a packet analyzer for decoding the time stamp of the received packet, a system clock indicating the time on the receiver side, and the decoded The time stamp comparison unit that calculates the difference between the time stamp value and the time on the receiver side provided by the system clock, and when the time stamp comparison unit detects a packet whose time stamp value is before the time on the receiver side, the received data is discarded. Alternatively, the invalid packet monitoring unit that outputs the received packet and returns the received packet to the original data To output Te data playback unit 7. The continuous data transmission apparatus according to claim 6, wherein the transmitter and the receiver further have the following features. (A) The transmitter time stamp imprinting unit further has a function of adding the same time stamp value to a plurality of packets according to the data contents. When the packet sending suppression request is received from the receiving side, the specified time stamp is added. (B) Receiver The invalid packet monitoring unit detects that a packet whose time stamp value is before the reception time has already been received, and the invalid packet monitoring unit has already received the packet. This function has the function of discarding or outputting the data of the specified time stamp, and further requesting the transmitter side to generate packets with the same time stamp and suppress the transmission of packets. The system further includes a transmission suppression request unit that creates a suppression request message.