JPH11145969A - Communication system and medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform communication without damaging a real time property and to provide high correction ability to burst errors by adding error correction codes to respective blocks into which one frame is divided, encoding them, then dividing them into plural blocks further, mixing respective block data and turning them to a prescribed length transmission/reception unit. SOLUTION: The moving image signals of a camera 101 are stored in a frame memory 107 for the respective frames through a DVC encoder 106. In this case, in DVC compression, since one-frame data are divided and recorded on ten oblique tracks on a tape, video data for one frame are divided into ten and turned to compressed data. Then, the error correction code is added to respective code blocks in an error correction encoder 108, divided data are connected and turned to one unit, a PDU number is added and they are transmitted and received. When an error is generated, since the data are lost by a PDU unit, actual burst error correction ability depends on the start position and a PDU boundary and thus, 2 PDU is surely guaranteed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication system and a medium for communicating, for example, image data, audio data and other auxiliary data in real time through a network.

[0002]

2. Description of the Related Art In recent years, in computers such as personal computers and workstations, with the advent of higher performance microprocessors and OSs equipped with network functions, faster peripheral device interfaces, and higher computer performance. Thus, the information handled by computers has changed dramatically. Initially ASCI
Although it was a character code such as an I code and a JIS code, the handling of graphics and the like in the CAD field and multimedia information such as moving images and sounds has become increasingly important today. The greatest feature is that such information is continuously generated in real time (hereinafter, real-time property).

On the other hand, with the spread of high-speed wide area networks, these multimedia data are stored and stored.
Networks with fast data transfer rates that can manage and transfer data to the network are also emerging.

By the way, a signal having a real-time property is
In order to transmit data using these networks, the transmitting terminal must transmit data to the receiving terminal without interruption.

As a network suitable for multimedia communication, for example, ATM (Asynchronous Transfer Mod
e: asynchronous transfer mode). According to this 155
Transmission at megabits / second is possible. Regarding ATM, ITU-T (International Telecommunication Uni
on-Telecommunication Standardization Sector: International Telecommunication Union-Telecommunication Standardization Sector) and The AT
It has been discussed and standardized by M Forum and others, and a number of related books have been issued. Other than ATM, 100
Mega Ethernet (100BASE-T), FDDI (Fiber D)
By using istributed DataInterface, etc., a high-speed transmission capability of 100 Mbit / s or more can be obtained, and multimedia communication can be realized. In addition, Ethernet (IEEE80
2.2, IEEE802.3), with the spread of switching hubs, each terminal is capable of transmitting at about 10 M / s, and real-time signals of less than this can be transmitted. Also, on the Internet, transmission of signals having real-time properties such as video conferences and Internet telephones is performed.

Conventional examples of a communication system for real-time signals include, for example, JP-A-7-170502 and JP-A-7-170502.
-170503, JP-A-7-170290, JP-A-7-170-
170291, JP-A-7-170504, JP-A-7-1
70292.

Japanese Patent Application Laid-Open No. 7-170502 discards portions other than particularly important portions in video and audio when the capacity of a video and audio buffer memory exceeds an upper limit value or falls below a lower limit value on the receiving side. This is a method of controlling the buffer memory as described above.

Japanese Patent Application Laid-Open No. Hei 7-170503 discloses a method of adjusting the speed of the clock read from the buffer when the capacity of the video and audio in the buffer memory exceeds the upper limit value or falls below the lower limit value.

Japanese Patent Application Laid-Open No. 7-170290 discloses that when the capacity of the audio buffer memory exceeds the upper limit value or falls below the lower limit value on the receiving side, a control signal to that effect is sent to the transmitting side.
The transmission side adjusts the speed of the memory reading clock.

Japanese Patent Application Laid-Open No. Hei 7-170291 discloses a method in which, when the capacity of a sound in a buffer memory exceeds the upper limit value or falls below a lower limit value, video and sound in the buffer memory are discarded.

Japanese Patent Application Laid-Open No. Hei 7-170504 discloses a transmission side in which a frame buffer is provided before a buffer memory, and when the capacity in the buffer memory exceeds an upper limit value or falls below a lower limit value, the clock of the frame buffer memory is adjusted. This is a method of adjusting the data amount by adjusting.

Japanese Patent Application Laid-Open No. 7-170292 discloses that when the capacity of a voice in a buffer memory exceeds the upper limit value or falls below a lower limit value on the transmitting side, the clock speed of the memory reading is adjusted, and The capacity in the buffer memory of
This is a method of controlling the communication amount by changing the compression ratio when the value exceeds the upper limit or falls below the lower limit.

[0013]

However, the above-mentioned prior art has the following problems.

Further, Japanese Patent Application Laid-Open Nos.
-170503, JP-A-7-170290, JP-A-7-170-
170291, JP-A-7-170504, JP-A-7-1
7292 requires a buffer memory capacity measurement circuit, a buffer contents discard operation circuit, an operation determination circuit, a circuit for specifying a compression parameter for returning an image compression ratio, and the like. Has a problem that it becomes larger.

It also generally provides unreliable packet delivery at the lowest level of the communication network. Packets can be lost or corrupted when the load on the network becomes too heavy to adapt to the appearing load due to the time-varying conditions of the network. Therefore, in order to realize a large amount of data transfer, it is required to construct error detection and recovery in the system at the highest level. Further, in data transmission such as video and audio that requires real-time performance, it is necessary to process data within a prescribed period so that output is not interrupted. Therefore, in order to realize real-time transmission while minimizing the delay, even if a cell loss or the like occurs, it cannot be compensated by retransmission. Therefore, a method of performing error correction coding on communication data is used.

Incidentally, data in communication is PDU
It is transmitted and received in units called (Protocol Data Unit: protocol data unit, the entire data handled in the layer). From the viewpoint of communication efficiency, increasing the transmission / reception unit is advantageous because the number of communications within a specified period is reduced and the processing load required for communication is reduced, but from the viewpoint of error correction, data packets When an error occurs, since an error packet cannot be specified at a higher level, data is lost in transmission / reception units. Therefore, it is desirable to reduce the transmission / reception units in order to minimize the amount of lost data.

In all of the above-mentioned prior arts, when the transmission capacity is limited, it is impossible to maintain the real-time property of a real-time signal, or the quality of an image is deteriorated more than necessary. Was.

The present invention has been made in order to solve the above-mentioned conventional problems, and communicates digital data requiring real-time (real-time) such as a moving image (video) signal and an audio signal. In this case, an object of the present invention is to provide a communication system and a medium that can perform communication without deteriorating the real-time property and have a high correction capability for burst errors.

[0019]

According to the present invention, there is provided a real-time signal generating means for generating a real-time signal in units of one frame, and a frame memory for temporarily storing the real-time signal of the one frame. Means, coding means for adding an error correction code to the real-time signal read from the frame memory and outputting a coded signal, transmission code memory means for temporarily storing the coded signal, Coded signal transmitting means for transmitting; transmitting means for transmitting the coded signal; coded signal receiving means for receiving the coded signal transmitted from the coded signal transmitting means in the transmitting means; Receiving code memory means for temporarily storing the encoded signal received by the encoded signal receiving means, and decoding the encoded signal Decoding means, output frame memory means for temporarily storing the real-time signal decoded by the decoding means, and real-time signal output means for outputting the received real-time signal stored by the output frame memory means. It is provided.

[0020]

Embodiments of the present invention will be described below with reference to the drawings.

The real-time signal in the present invention is:
It can be applied to any signal that requires real-time properties such as a moving image signal or an audio signal. However, in the embodiment of the present invention, unless otherwise specified, a digitized moving image signal is converted to a real-time signal. Take an example.

The number of samples in the horizontal and vertical directions related to the resolution of the moving image signal, whether or not the moving image signal is subjected to compression processing, and if so, what kind of compression processing is performed is transmitted. The present invention is effective regardless of the quality of a moving image. That is, the present invention is effective regardless of the bit rate of the transmitted real-time signal.

In the embodiment of the present invention, the VT of the DVC standard is used.
An image signal of a sampling system and a compression system used for R is taken as an example.

"DVC" is an acronym for Digital Video Cassette, and this standard has been agreed upon by the HD Digital VCR Council. For example, the magazine "National Technical Report" Vol. 41, No. 2, April 1995, No. 15,
2 to 159. In the embodiment of the present invention, the case of the NTSC signal of the DVC standard is taken as an example. According to the system of the DVC standard (NTSC signal), the data bit rate is 28.8 Mbit / s (hereinafter referred to as 28.8 Mbit / s).
8.8 Mbps).

As the transmission means, any transmission means may be used as long as it has a transmission capacity larger than the bit rate of the real-time signal to be used. In the embodiment of the present invention, an ATM network having a transmission rate of 155 Mbit / sec is used. The network protocol used is A, which is most commonly used for data transfer between ATM networks.
Take AL5 as an example.

Error detection in AAL5 is performed after PDU construction. For this reason, when a cell loss or erroneous insertion occurs in the ATM network, it is impossible to specify an error cell, and when an error is detected, data is lost in PDU units. In other words, if even one cell loss occurs in one PDU, all of the one PDU will be lost, and the lost data will expand.

For this reason, from the viewpoint of error correction, when a burst error occurs in data, it is desirable that the PDU size is small in order to match the amount of data lost due to the burst error to the PDU boundary as much as possible.

On the other hand, from the viewpoint of actual communication efficiency (transmission capability), it is advantageous to increase the PDU size, since the number of times of communication within a certain period of time is reduced, and the processing load required for communication is reduced.

(Embodiment 1) FIG. 1 shows a system configuration according to a first embodiment of the present invention.
01 is a camera for capturing a moving image, 102 is a transmitting terminal, 103 is an ATM switch, 104 is a receiving terminal,
Reference numeral 105 denotes a monitor for outputting a moving image.

Reference numeral 106 in the transmission terminal 102 denotes a DVC encoder for performing a DVC compression process, 107 denotes a frame memory for temporarily storing DVC-compressed frame data, and 108 denotes a D memory read from the frame memory 107.
An error correction encoder for adding an error correction code to the VC compressed data, a transmission code memory 109 for temporarily storing encoded transmission data, and an ATM network interface card (ATM-NIC) 110.

The receiving terminal 104 has an ATM network interface card (ATM-NIC), 1
Reference numeral 12 denotes a reception code memory for temporarily storing reception encoded data. Reference numeral 113 denotes an error correction decoder for performing error correction on the reception code data read from the reception code memory 112.
Reference numeral 4 denotes a frame memory for temporarily storing the decoded DVC compressed data, and 115 a DVC decoder for expanding the DVC compressed data.

The operation of the communication system configured as described above will be described below.

FIGS. 2 and 3 show data structures used in the embodiment of the present invention. First, at the transmitting terminal 102,
A moving image signal obtained from the camera 101 is DVC-compressed by the DVC encoder 106 in frame units.
Since the NTSC signal is composed of 30 frames per second, in the embodiment of the present invention, 30 frame data are obtained per second. The DVC data output from the DVC encoder is stored in a frame memory 107 for each frame.
Is stored. In the DVC compression, one frame of data is divided into ten oblique tracks on a tape and recorded, so that one frame of video data is divided into ten parts to obtain compressed data (FIG. 2A ) A, B, ..., J). If each part is called a code block, an error correction code is added to each code block by the error correction encoder 108 (FIG. 2B). This encoded data has a parity code for the information portion of the data and is used for correction when a code error is detected. By the way, in the DVC system, video data is handled on the basis of a unit called a sync block. Although any error correction code may be used here, a Reed-Solomon product code is used here, and its error correction capability can be corrected up to 11 sync block erasures. The data obtained as a result is further divided into A1, A2... A4 as shown in FIG.
It is divided into 43 blocks up to 3. The same applies to B to J. As a result, the size from A to E is 1
Since there are 50 sync blocks, 151 sync blocks from F to J, which are larger than the original size of 149 sync blocks, dummy data is inserted for data exceeding the original data. For the data divided as described above, data obtained by connecting A1, B1,.
Transmit and receive as U. Similarly, by connecting the corresponding blocks from B to J for A2 to A43 to form a PDU, 43 PDUs are obtained per frame as shown in FIG. 3B. As a result, the obtained data is transmitted through the ATM-NIC 110 to the ATM in units of PDU.
-Input to SW103. In other words, it is sent to the ATM network.

At the receiving terminal, the data is received through the ATM-NIC 111, and the data is stored in the reception code memory 112 through the reception code memory controller.
The received data is decoded through the error correction decoder 113 in code block units. The resulting data is stored in the frame memory 114, becomes a video signal through the DVC decoder 115, and is output and displayed on the monitor 105.

When the PDU is configured as described above, from the viewpoint of error correction, data is lost in units of PDU when an error occurs. Therefore, when an error occurs, 3.5 (actually 3 or 4) syncs per code block are performed. Block error. Therefore, even when three consecutive PDUs cause an error, the error becomes a maximum of 4 + 3 + 4 = 11 sync blocks and can be corrected. Since the actual burst error correction capability depends on the start position of the burst error and the boundary of the PDU, two PDUs are reliably guaranteed. Here, it is assumed that there is no other error in the same frame.

(Embodiment 2) FIG. 4 is a block diagram showing an embodiment of the present invention. FIG. 5 is a timing chart showing a relationship between received data and a frame reference signal in the embodiment of the present invention. In FIG.
1 is a frame reference signal generator. Other reference numerals the same as those in FIG. 1 indicate the same components. In the embodiment of the present invention, a PDU number to be transmitted is added with a frame number together with a PDU number, and transmitted / received.

Hereinafter, an embodiment of the present invention will be briefly described with reference to FIG. FxP shown in received data in FIG.
xx indicates that data is being received at that timing. For example, the received data F1P43 in FIG. 5 indicates the 43rd PDU of the first frame. Further, the frame reference signal in the timing chart of FIG. 5 takes a binary value of H or L, and the DVC decoder 1
15 outputs frame data. For example, T1 in FIG. 5 indicates the output timing of the first frame, and T2 indicates the output timing of the second frame. Here, at the time T1, all PDUs with PDU numbers up to 43 in the first frame have been received. On the other hand, at time T2, not all PDUs of the second frame have been received, and F2P42 and F2P43 have been received since T2. It is considered that the arrival of the PDU was delayed due to data congestion in the network.
This means that not all the data was in time for the frame output timing, and the data received thereafter (here, F2P42 and F2P43) are useless data, and are discarded at the time of reception.

According to this configuration, in addition to the effects described in the above embodiment, in the present embodiment, the receiving terminal views the frame number of the data received, and receives the data that cannot be processed in time for the frame. By discarding without performing the subsequent processing, the load on the processing of the receiving terminal can be reduced.

(Embodiment 3) FIG. 6 shows the order of PDUs transmitted for each frame in the embodiment of the present invention. It is assumed that the system configuration according to the embodiment of the present invention is the same as that of FIG.

In this embodiment, each frame is represented by P
The method of dividing into DUs is the same as in the above embodiment, but the transmission order of each PDU is different, and it is assumed that PDUs are transmitted in the order of PDU numbers shown in FIG. That is, in the first frame, first, a PDU whose PDU number including A1, B1,...
Then, PD composed of A2, B2, ..., J2
U2 transmits the PDU3 in the order of A3, B3,..., J3.

On the other hand, in the second frame, first, A
, A PDU1 composed of A3, B3,..., J3, and a PDU2 composed of A3, B3,. ,
J4 is transmitted in the order of PDU3.

According to the present embodiment, the transmission order of the mixed transmission / reception units is changed, and the received data that is not in time for the processing of the frame is discarded without performing the subsequent processing, and the total error amount of the data is reduced by the error correction capability. Is over,
Correctly received data is output as it is, and the part that was not correctly received is replaced with the previously received data, thereby limiting the transmission capacity of the communication line.
Even when all data for a frame cannot be received, the screen can be uniformly updated.

For example, if the capacity of the communication line is temporarily limited, 43 PDUs constituting a frame for two consecutive frames
If the reception of the last 4 PDUs is not in time for the processing of the frame, the PDs constituting the first frame
U 4 rear PDUs (PDU numbers 40 to 43 of frame number 1) and the rear 4 PDUs constituting the second frame
(PDU numbers 40 to 43 of frame number 2) cannot be processed in time for the frame. Therefore, the data lost in the first frame (PDU numbers 40 to 43 of frame number 1) are A40 to A43, respectively.
.., J40 to J43. On the other hand, data lost in the second frame (PDU numbers 40 to 43 of frame number 2) are
A1 and A41 to A43, B1 and B41 to B43,..., J1 and J41 to J43, respectively. As a result, since each frame loses 4 PDUs, an uncorrectable data portion exists, but the corresponding uncorrectable data position on the screen is different.
That is, even if the PDU cannot be received continuously, the data on the screen is updated evenly.

(Embodiment 4) FIG. 7 is a block diagram showing an example of an embodiment of the present invention. FIG. 8 shows a tape recording format on one track of a video section by the DVC VTR.

In FIG. 7, reference numerals 701 and 704 denote DVCs.
The system VTR, 702 is a transmitting terminal, and 703 is a receiving terminal. 705 inside the VTR 701 is an error correction encoder 1
08, a switch for switching the output destination of the error correction coded signal obtained from the reference numeral 08, a tape 706 set on the VTR.
07 is a recorder for recording video.

708 inside transmission terminal 702 is a DV for inputting the encoded signal output from error correction encoder 108.
A C / I / F 709 is a CPU for controlling the transmitting terminal;
Reference numeral 0 denotes a memory for temporarily storing a control program and transmission data of the transmission side terminal 702, and reference numeral 711 denotes a PCI bus.

712 inside the receiving terminal 703 is a CPU for controlling the receiving terminal 703, and 713 is a receiving terminal 702.
714 is a memory for temporarily storing a control program and received data, 714 is a DVC-I / F for inputting a received coded signal to the error correction decoder 113, and 715 is a PCI bus.

Reference numeral 716 in the VTR 704 is a switch for switching the input source of the error correction coded signal to the error correction decoder 113, and 717 is a reproducer for reproducing a video from the tape 718 set in the VTR.

The same reference numerals as in FIG. 1 denote the same components.

In the DVC VTR, an error correction code is added to audio data, DVC-compressed video data, and auxiliary data, respectively, and the resulting data is recorded on a magnetic tape. FIG. 8 shows a recording format for video data on one track.

According to the present embodiment, it is possible to easily obtain an ATM transmission apparatus by using the processing in the DVC VTR.

In the embodiment of the present invention, AAL5
Has been described as an example of the transmission protocol, but the essence of the present invention is that it is possible to efficiently transmit real-time signal data with one frame as one unit and to obtain a high correction capability for burst errors. Therefore, the present invention is not limited to AAL5, and the use of other protocols having the same mechanism is not excluded from the scope of the present invention.

In the embodiment of the present invention, a case where only a moving image signal is handled has been described as an example. However, the present invention is also effective when a moving image, voice, auxiliary data, and the like are simultaneously communicated.

By the way, a magnetic recording medium or an optical recording medium in which a program for causing a computer to execute the functions of all or a part of each means described in any one of the above-described embodiments is prepared. By utilizing this, the same operation as described above can be performed, and the same effect as above can be exerted.

As described above, according to the communication system of the present invention, the data of one frame of the real-time signal input to the transmitting terminal is divided into a plurality of parts, and an error correction code is added to each part. By further combining data obtained by dividing the above data into transmission / reception units, a remarkable effect that communication with high efficiency and high burst error correction capability can be realized is obtained.

Further, by referring to the frame reference signal and discarding the received data that is not in time for the processing of the frame without performing the subsequent processing, the processing load on the receiving terminal can be reduced. it can.

Also, by changing the transmission order of mixed transmission / reception units for each frame and updating only a portion corresponding to correctly received data, the transmission capacity of the communication line is limited, and all data can be received. Even when it becomes impossible, the screen can be uniformly updated.

Further, it is possible to easily obtain a transmission apparatus by utilizing the processing of a recording / reproducing apparatus for recording / reproducing a signal including an error correction code on / from a recording medium.

[0059]

As is apparent from the above description, the present invention has an advantage that more reliable communication can be performed with respect to data requiring real-time performance as compared with the related art.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a communication system according to a first embodiment of the present invention.

FIG. 2A is a configuration diagram illustrating a configuration of compressed video data according to the first embodiment of the present invention. FIG. 2B is a diagram illustrating encoded video data according to the first embodiment of the present invention. Configuration diagram showing configuration

FIG. 3A is a configuration diagram illustrating a method of dividing encoded video data according to the first embodiment of the present invention. FIG. 3B is a PDU (transmission / reception unit) according to the first embodiment of the present invention. Configuration diagram showing the configuration of

FIG. 4 is a configuration diagram illustrating a communication system according to a second embodiment of the present invention;

FIG. 5 is a timing chart showing timings of received data and a frame reference signal according to the second embodiment of the present invention.

FIG. 6 is a configuration diagram showing a configuration of a PDU (transmission / reception unit) according to a third embodiment of the present invention.

FIG. 7 is a configuration diagram showing a communication system according to a fourth embodiment of the present invention.

FIG. 8 is a configuration diagram showing a configuration of encoded video data according to a fourth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 Camera 102 Sending terminal 103 ATM switch 104 Receiving terminal 105 Monitor 106 DVC encoder 107 Frame memory 108 Error correction encoder 109 Transmission code memory 110 ATM network interface card 111 ATM network interface card 112 Receive code memory 113 Error correction decoding Unit 114 Frame memory 115 DVC decoder

Claims (5)

[Claims] 1. A communication system for communicating real-time signals, comprising: a real-time signal generating means for generating a real-time signal in units of one frame; and a frame memory for temporarily storing the real-time signal of one frame. Means, an encoding means for adding an error correction code to the real-time signal read from the frame memory means, and outputting an encoded signal; a transmission code memory means for temporarily storing the encoded signal; Coded signal transmitting means for transmitting a signal, transmitting means for transmitting the coded signal, coded signal receiving means for receiving the coded signal transmitted from the coded signal transmitting means in the transmitting means, Receiving code memory means for temporarily storing the encoded signal received by the encoded signal receiving means; Decoding means for decoding the encoded signal; output frame memory means for temporarily storing a real-time signal decoded by the decoding means; and outputting the received real-time signal stored by the output frame memory means. Real-time signal output means, wherein one frame divides data of length L into M blocks of length N (L = M × N, where L, M and N are natural numbers), and After adding and encoding an error correction code, the encoded data of each block is further divided into a plurality of blocks, and data of a predetermined length obtained by mixing data of each block is used as a transmission / reception unit. Communications system. 2. A communication system for communicating real-time signals, comprising: a real-time signal generating means for generating a real-time signal in units of one frame; and a frame memory for temporarily storing the real-time signal of one frame. Means, an encoding means for adding an error correction code to the real-time signal read from the frame memory means, and outputting an encoded signal; a transmission code memory means for temporarily storing the encoded signal; Coded signal transmitting means for transmitting a signal, transmitting means for transmitting the coded signal, coded signal receiving means for receiving the coded signal transmitted from the coded signal transmitting means in the transmitting means, Receiving code memory means for temporarily storing the encoded signal received by the encoded signal receiving means; Frame reference signal generating means for outputting a frame reference signal indicating the processing timing of the frame, decoding means for decoding the encoded signal, and an output frame for temporarily storing a real-time signal decoded by the decoding means Memory means; and real-time signal output means for outputting the received real-time signal stored by the output frame memory means, wherein one frame divides data of length L into M blocks of length N (L = M × N, where L, M, and N are natural numbers), after adding an error correction code to each of the blocks and encoding, the encoded data of each block is further divided into a plurality of blocks, The frame number of the received data is defined as the transmission / reception unit, which is the data in which the frame number is added to the data of a predetermined length that is a mixture of , The received data that is not in time for the processing of the frame is discarded without performing the subsequent processing. 3. The communication system according to claim 2, wherein a transmission order of said transmission / reception unit is changed for each frame, and only data which has been processed during processing of said frame is updated. 4. A communication system for communicating a signal having a real-time property, comprising: a real-time signal generating means for generating a real-time signal in units of one frame; and a frame memory for temporarily storing the real-time signal of one frame. Means, an encoding means for adding an error correction code to a real-time signal read from the frame memory means and outputting an encoded signal, a transmission code memory means for temporarily storing the encoded signal, and an error correction code. Recording means for recording on a recording medium a real-time signal including: a coded signal transmitting means for transmitting the coded signal; a transmitting means for transmitting the coded signal; and the coded signal transmitting means in the transmitting means. A coded signal receiving means for receiving the coded signal transmitted from the Reproducing means for reproducing a real-time signal from a recording medium; receiving code memory means for temporarily storing the encoded signal received by the encoded signal receiving means; decoding means for decoding the encoded signal; Output frame memory means for temporarily storing the real-time signal decoded by the decoding means; and real-time signal output means for outputting the received real-time signal stored by the output frame memory means. As for the recording data, one frame divides data of length L into M blocks of length N (L = M ×
N. However, L, M, and N are natural numbers), each block is configured by adding an error correction code, and data of a predetermined length obtained by mixing each block data of the recording data is used as a transmission / reception unit. Communications system. 5. A medium on which a program for causing a computer to execute the functions of all or a part of each of the means according to claim 1 is recorded.