JP2001186518A - Transmission system for digital image data - Google Patents

Abstract

PROBLEM TO BE SOLVED: To build up an image distribution system which flexibly copes with a remote control by a transmission image and revision of a transmission rate or the like and to configure an image information transmission network, suitable for compressed image transmission in a transmission network of image information consisting of loop type transmission lines. SOLUTION: In the data communication transmission system, where data have a data frame structure sectioned by a time slot set in advance with respect to a transmission line, information of a node device is assigned to the unit time slot, and each node receives and sends data through the reception/ transmission of the data frame, a plurality of unit time slots are assigned to one terminal, as required, and the time slot is properly changed corresponding to the change in the transmission rate in a multiplex transmission system of digital image data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a multiplex transmission method and a data transfer method in digital data communication between terminals connected to an arbitrary node device of an information transmission line using an information transmission line such as an optical fiber in a loop type. With respect to these devices, it is intended to provide a digital image data transmission system particularly suitable for compression transmission of image information.

[0002]

2. Description of the Related Art When multiplexing and transmitting data of a plurality of digital data groups, it is necessary to bundle data groups having a low transmission speed output from a plurality of terminals into a trunk system having a high transmission speed such as an optical fiber. is there. For that purpose, it is necessary to absorb the difference in transmission speed, and as the method, a method that emphasizes band efficiency utilization, a method that emphasizes low transmission delay, and the like can be considered. Generally, congestion control that emphasizes efficient use of bandwidth is often used. However, when considering real-time communication, multiplexing and congestion control that emphasizes low transmission delay over efficient use of bandwidth may be necessary.

In the multiplexing method of the terminal system line, it is impossible to multiplex beyond the upper limit line (N) of the trunk system band. That is, N ≧ (A + B + C) in FIG. 9 and N ≧ (A
+ B '+ C + D). In both figures, 1
Indicates a trunk line, and 2 indicates a terminal line. The thickness of the line is proportional to the amount of information. Further, 2A, 2B, 2C, and 2D indicate individual terminal lines, and F11 and F12 indicate data streams of transmission information of the trunk line 1.

In the state shown in FIG. 9, since there is a margin 21 in the main system band, each communication is stable. FIG.
When a new terminal starts communication from the state of. The band required for communication may be insufficient. In such a case, as shown in FIG.
It is assumed that communication of the new terminal 2D has started. In the state of FIG. 9, the terminal 2B has transferred five data groups at the time t1, but when the state of FIG.
, Four data groups and the remaining data group are transferred at time t2. Here, assuming that the data stream of terminal 2B is composed of five data groups, in FIG.
At 1 the data stream is completed and data processing is possible, but at 10 it will wait until time t2.

[0005]

That is, during communication, the delay amount increases by (t2-t1). If this situation continues for a long time, (BB ') data is accumulated per unit time, and the delay is further increased. Further, when the storage capacity exceeds the limit, there is a possibility that data is discarded. The transmission delay and data discarding are important issues in remote image monitoring.

[0006] In remote image monitoring, camera control is performed while viewing transmitted images. The image observer starts and ends camera control based on the transmitted image. However, the actual start and end of the control are delayed by the amount of delay of the image. If the amount of delay is large, the response becomes poor, and it becomes difficult to control the camera for a short time. Regarding data discarding, if image data is discarded, image reproduction is disturbed. If data discarding occurs for a long period of time, it becomes a serious problem in an online monitoring system.

[0007] Normal images are transmitted by compressing a video signal. in this case. MPEG2 compression schemes are beginning to be widely used. In this MPEG2 compression method,
At present, since compression / expansion processing is performed using future image data, it is assumed that the input video signal to be compressed is a continuous signal. However, when the compression method of MPEG2 is used for a monitoring system, continuity of the input signal is not guaranteed if the above-mentioned data is discarded. For this reason, in such a case, noise peculiar to the compression code data error is generated, and the image may be distorted or, in the worst case, the encoding device may not operate. The same applies to the data stream input to the decoding device. That is, it is assumed that a fixed encoding device is connected to one decoding device.

[0008] Considering the operability of the system, FIG.
In a simple n: 1 system composed of a plurality of data transmitting terminal groups 3 and 4 and one data receiving terminal group 10 (10A, 10E, 10F, and 10C), the line bandwidth that the data receiving terminal can occupy is This is equivalent to the band of the trunk system 1 and is an efficient use in data reception. However, from such a state, in an n: n system composed of a plurality of data transmission terminal groups 2 and 3 and a plurality of data reception terminal groups 10 and 20 as shown in FIG.
The band that can be used by 0 and 20 is limited to a part of the main system band. At this time, the trunk system 1 is connected to all data receiving terminal groups.
When using the same bandwidth as that of FIG. 1, a copy of the data is made according to the data receiving terminal and transferred to each receiving terminal.
As shown in FIG. 3, data 41C and 41 of the data transmitting terminal
After transferring A, 31E and 31F to the data receiving terminal group 10, further data processing operations such as transferring the same data to the data receiving terminal 20 are required. If two data receiving terminal groups both try to use the same bandwidth as the trunk bandwidth, traffic twice as much as the trunk bandwidth occurs between the trunk line and the receiving terminal line, causing severe congestion, The data processing operation unit is overloaded. For temporary congestion,
Although it can be solved by data copy, re-transfer, etc., the amount of delay varies due to data transfer, etc. When permanent congestion occurs, a function such as securing another route is required according to the traffic.

FIG. 14 shows a means for performing communication with a constant transmission delay time and low delay. Terminal line 2 in FIG.
, The number of lines is set in advance irrespective of whether it is used. In this figure, five lines are set, and lines 2E and 2F are used. In the trunk system, all data frames E to I are always output, but since the 2G, 2H, and 2I lines are not used, they are transferred as empty data. For this reason, the data stream of each line is transferred at a constant cycle, and no fluctuation in delay occurs.

[0010] In the image data distribution system, the transmission point of the image data is not one place, and the number of transmission terminals is not fixed. As shown in FIG. 14, in a system that requires a limited number of transmission terminals, the construction will be sufficient. However, in an actual image data distribution system, additional transmission terminals and reception terminals at a plurality of locations are assumed. In this case, if lines are assigned to all terminals, the communication band per terminal becomes small.

Therefore, the form of the trunk line is set to a loop type, and lines required for system construction are allocated. All the transmitting terminals and all the receiving terminals can access the allocated line. For the line assignment, the number of lines to be monitored at a time on the image monitoring side, that is, the number of lines to be transmitted at the same time, is set, and for receiving image data, a transmission terminal connected to the line is switched to construct a system. In addition, it is necessary to adopt a method in which the line switching time can be performed instantaneously due to the nature of the monitoring system.

FIG. 1 shows an example of an image data distribution n: n system. Such a loop-type data transmission system is disclosed in detail in Japanese Patent Laid-Open No. Hei 10-79754 of the present applicant.

The present invention relates to an improvement of the loop type data transmission system, and more particularly to a digital image data transmission system which prevents a change in transmission rate during transmission of a compressed image and disturbance of an image upon switching channels. .

[0014]

FIG. 1 is a diagram showing the concept of a loop type data transmission system which is the basis of the present invention.
Is a trunk line, 10, 20 is a receiving terminal device, 3, 4, 5,
Is a transmission terminal device. When the trunk line 1 is in a loop communication mode, the data of the transmission terminal group is constantly updated and exists in the trunk line 1. The receiving terminal devices 10 and 20 establish communication by acquiring a copy of required data from the trunk line 1. Since copying of data is performed by the receiving terminal device 10 or 20 itself, a device for performing multicasting or broadcasting becomes unnecessary, and even when the number of receiving terminal groups increases and the same data is used, there is no problem regarding congestion.

In order to operate the system shown in FIG. 1, it is necessary to allocate lines first. In this figure, five lines are set, and only one device in a loop, for example, the data frame 1F set by the receiving terminal device 10 is transmitted.
The transmitted data frame 1F must always maintain continuity.

On the other hand, when communicating image data, simply encoding a video signal results in a huge data amount. Therefore, recently, communication is generally performed using an encoding technique for reducing the amount of data. JPEG for still images or picture-story forward videos,
In particular, a prediction-type method such as MPEG2 is used for highly efficient encoding. The operation concept of predictive coding is to decode a current image using past data and future data.

It is an object of the present invention to construct a transmission system free of delay fluctuation by distributing compressed image data having a large amount of information in such an information transmission system centered on a loop type image. Also, there is no data discard due to congestion, so that the reliability is improved, and the receiving side does not require a device such as a matrix switcher, and the output data can be easily selected and changed.
In addition, an image can be reproduced without any problem using an image compression method such as JPEG or a predictive image compression method such as MPEG2, and the transmission rate can be changed.

That is, according to the present invention, in a digital image data transmission system, a plurality of node devices are installed on a transmission line formed in a loop, and the transmission line has a data frame structure partitioned by a preset time. A data communication transmission system in which predetermined unit node information is assigned to each of the divided unit time slots, wherein a plurality of the unit time slots are assigned to one terminal as needed. It was made.
Further, the digital image data is compressed data, and the multiplex transmission is adapted to cope with the change of the number of channels by changing the clock of the terminal device in accordance with the change of the allocated terminal time slot, ie, the number of channels (lines). System. Further, in the present invention, when a moving image or a forward moving image is compressed and transmitted, the receiving terminal side of the compressed image in the terminal device inserts one packet of blank data when switching the received compressed data. It is a feature.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the system shown in FIG. 1, a function of performing line access is called a node device, and each terminal is connected to the node device. FIG. 2 shows an example of the state of the system. FIG. 3 shows a conceptual diagram of the system in the embodiment of the present invention. In the figure, 3, 4, and 5 are transmission terminals, 1 is a trunk line and a transmission line formed by a loop-type optical fiber, 10 and 20 are terminal devices on the reception side, and 10 has a base station configuration. Constitute a secondary base station. The same reference numerals as those in FIGS. 1 and 2 denote the same items, and are common to all drawings. 103, 203 are decoders, 2001, 3001,
4001 is an encoder, 2002, 3002, 410
2, 4202 and 4302 are television cameras. As can be seen from the figure, the transmitting terminal 5 has three television cameras, and if necessary, only one television camera may be used, or all three television cameras may be used. For this reason, the transmission terminal 5 may use up to three lines. 101 and 202 are operation consoles,
Reference numerals 201 and 102 denote monitor devices for images by the television camera. The receiving terminal device 10 is a base station. Also,
Although three transmitting terminals are shown in this embodiment, there are actually more transmitting terminals, and several television cameras may be connected to each transmitting terminal. Although not shown, each transmitting terminal includes a speaker, a microphone, a sensor for weather information, and the like.

FIG. 4 is a block diagram of the hardware configuration of the optical multiplex transmission apparatus 100. Although FIG. 2 basically shows a configuration common to each node device, FIG. 3 shows a configuration of the receiving terminal 10 as a representative.

In FIG. 3, each optical multiplex transmission apparatus 100 includes 100-10, 100-20, 100-3, 100
-4 and 100-5. In FIG. 4, 1
1 is an opto-electric signal converter, 12 is an electro-optical signal converter, 13
Is a switch, and the switch 13 serves as bypass means in the case where the terminal has failed. 14 is a signal multiplexing interface, 15 and 16 are image and audio multiplexing circuits,
The image is compressed or decompressed by MPEG and multiplexed or separated from the audio signal. Normally, the image and voice are compressed at the transmitting terminal, and decompressed at the receiving terminal. In the case shown in the figure, two audio / video multiplexing circuits 15 and 16 are provided, but one may be provided. This number depends on the number of channels in the image. Reference numeral 17 denotes a voice unit for voice communication between the transmitting terminal and the receiving terminal, or between the receiving terminals, or between the transmitting terminals as in a normal telephone. A CPU unit 18 exchanges control information. 19 is RAS (Reliability Av)
availability Serviceabilit
In y), when an abnormality of these devices is detected so that the whole system does not go down due to a failure of the image and audio multiplexing devices 15 and 16 or the audio unit 17 and the CPU unit 18, the switch 13 is controlled to switch the terminal. This is a device that controls to bypass.

FIG. 8 shows the optical multiplex transmission device 10 of the receiving terminal 10.
FIG. 4 shows a more detailed block diagram of 0-10. In the figure, a serial-to-parallel converter 141 performs serial-to-parallel conversion of the data frame 1F (see FIG. 5). The configuration of the data frame will be described later. The optical multiplex transmission apparatus 100 converts the serial data frame 1F into parallel data and performs each function processing.
A parallel-serial converter 142 converts the parallel data frame 1F into serial data and transmits the serial data to the next optical multiplex transmission device. Reference numerals 151 and 161 denote image data selection circuits for selecting an assigned line. In particular, the image data selection circuit 151 receives the information of the line change and selects the line of the required image data. Image data selection circuit 16
1 selects an empty line to multiplex images. PLL
The frequency dividers 152 and 162 operate the decoders 103 and 20 based on the system clock extracted from the data frame 1F.
3. Generate a clock to be supplied to the encoders 2001, 3001, 4001 and the like. Also, the PLL frequency dividing circuit 15
2, 162 receives the change information of the number of used lines and changes the clock. This clock depends on the data transmission rate. A parallel-serial conversion circuit 153 converts the parallel image data of the data frame 1F into serial data. 163 converts the serial image data from the decoder 103 into a parallel decoder. These, 15
Reference numerals 3 and 163 are connected to the optical multiplex transmission apparatus 100. Thus, the interface between the encoder and the decoder is serial data communication. Reference numerals 154 and 164 denote memories for adjusting the access timing of the data frame 1F and the image data. The memory 154 is used to extract image data from the data frame 1F, and the memory 164 is used to superimpose image data on the data frame 1F. 143 and 155 are demultiplexers,
144 and 165 are multiplexers. The demultiplexer 155 and the multiplexer 165 operate in accordance with a selection instruction from the image data selection circuits 151 and 161.
4, 164 and the data frame 1F are accessed.

FIG. 7 shows a data stream of the signal PL in FIG. This data stream is an MPEG2 data stream, and indicates packet data that comes periodically. This operation will be described later in detail.

FIG. 5 is a diagram showing the data structure of one frame 1F of data flowing through the trunk line 1 according to the present invention, wherein 31, 41, and 51 are superimposed by the terminal devices 3, 4, and 5. Reference numeral 10 denotes a data section for controlling voice and peripheral devices, and is accessed by the optical multiplex transmission apparatus 100. 31 is the MPE of the television camera 2002 of the terminal device 3
The image data compressed by G2, 41 is the image data of the terminal device 4 similarly, 51-1, 51-2, and 51-3 are the television cameras 4102, 4202, and 4302 of the terminal device 5.
These are the compressed image data from
1, 51-1, 51-2, and 51-3 may include compressed digital audio data by audio compression means such as MP3. Whether the image data 31, 41, 51-1, 51-2, and 51-3 are superimposed on the data stream of the frame 1F can be determined from the channel information of 10-6. In the actual superimposition, an unused line is used in response to a superimposition request, and thus the order does not always match the illustrated state. That is, each line (channel) 31, 41, 51-1, 51-2, 5 of the video / audio data portion
The order of 1-3 varies depending on the situation, and is not fixed. Further, the data frame configuration includes telephone data 10-1, data communication data 10-2, RAS information 10-3, 20-1, broadcast data 10-4, camera control data 10-5, and channel information 10--5 in FIG. 6, audio data 10-7 and sensor data 10-8. Each data has a header (not shown) at its head. The data communication data 10-2 is communication data between terminals connected to the optical multiplex transmission apparatus 100 (for example, personal computer communication by RS232C), and enables one-to-one communication. The communication partner can be selected. RAS data 10-3
Is data for transmitting information on abnormality of each terminal in this system. The broadcast data 10-4 is broadcast data, and is audio data that can be transmitted from one optical multiplex transmission device 100 to all the other optical multiplex transmission devices 100. The camera control information data 10-5 is data for remotely controlling the electric pan head of the television camera of each terminal to change the imaging direction and the zoom ratio. In this case, data is generated by the receiving terminal 10 as a base station and the receiving terminal 20 as a secondary base station.

The channel information 10-6 is the video / audio data 3
This is data for determining which transmission terminal is the data of the image-related lines 1, 41, and 51, and can also determine the line usage. The audio data 10-7 is the receiving terminal 10.
Alternatively, two-way communication is possible with a combination of image (audio) data of 31, 41, and 51 with audio data transmitted from the terminal 20 to the transmission terminals 3, 4, and 5.

In such a system, a unique ID on the loop is added to each node device, that is, the optical multiplex transmission device 100, so that the device can be identified. Also,
An input / output port for connecting to a terminal, that is, a multiplex interface 14 is provided. The node devices of the receiving terminals 10 and 20 determine the state of the line and request connection of the transmitting terminal. The transfer is started by specifying the device ID and the port. The determination of the line status on the receiving terminal side and the determination of the transmission request on the transmitting terminal are performed by the CPU unit 18 of each receiving node. The line connection information for determination is present in the channel information 10-6 in each data frame, and each terminal device 3, 4,.
5, 10, and 20 can refer to this. As described above, the data frame composed of the line information and the line data is composed of the line information (channel information) 10-6 and the line data 31, 41 and 51.
0-6 indicates all set line information.
The line data in FIG. 5 is data of an arbitrary transmitting terminal, and varies according to a request from the receiving terminal 10 or 20. Since the transmitting terminal connected to the line can be identified by referring to the line information, the receiving terminal makes a copy of only necessary data and communicates.

Summarizing the above operations: 1) The receiving terminal device sets the device ID to be output in the node device. 2) The receiving terminal device determines whether or not there is a connection by referring to the line information. 3) If there is no connection, set the device ID in the line information. 4) The receiving terminal device also sends the device ID to port 1 to which it wants to output.
Is set. The transmitting terminal devices 3, 4, and 5 always monitor the line information and start transmission immediately when the terminal device matches its own device ID. The line connection of the transmitting terminal is performed according to an instruction from the receiving side, but does not perform a handshake for confirming the connection. This is because one transmitting terminal and a plurality of receiving terminals may communicate with each other. Since the procedure is simple, high-speed connection can be realized. In the case of a line-connected terminal, output data can be switched only by changing the device ID of the output port.

Next, with reference to FIGS. 1 and 2, the operation when the information amount of the line of the specific terminal is doubled in this embodiment will be described in detail. This is dealt with by using a plurality of terminal lines. The receiving terminal sends to the transmitting terminal,
Notify multiple use of line and improve transmission speed. This example is shown in FIG. In FIG. 2, the use state of each line is changed from the state of FIG. 1 in accordance with the improvement of the band of the terminal F line. The terminal N line, which has been performing communication so far, indicates that the communication has been forcibly disconnected due to the improvement of the band of the terminal F line. This is performed by determining the priority in advance and selecting a disconnected line with a low priority. Or at this time,
It is also possible to reject the improvement of the terminal F line. Here, the improvement of the band occurs when the image transmission rate is changed to a high value, for example, from one frame per second to two frames per second.

As described above, regarding the use of a plurality of lines,
This is necessary when increasing the transmission rate. For example, in response to a request from an operator operation of the console 101 of the receiving terminal 10, the channel information 10-6 confirms that the receiving terminal is not using two pieces of line information, updates the line information, and updates any transmitting terminal. By notifying that there are two lines being used and making a transmission request, communication with a wider band becomes possible and the transmission rate can be increased.

Hereinafter, a specific example of this operation will be described. FIG. 1 shows a case in which one line is used, and the CPU unit 18 checks whether the bandwidth of the F line can be extended by the receiving terminal 10 using the channel information 10-6. FIG.
Since all five lines are used, band expansion is impossible, but when the priority of the N lines is low, the expansion of the F line can be forcibly performed. This state is shown in FIG. At this time, the CPU unit 18 stores the channel information 10
An ID indicating the same transmitting terminal is added to the information indicating the line and image data 41 and 51-1 in -6. The transmitting terminals 3, 4, 5 and the receiving terminals 10, 20 both switch to the access method for band expansion by referring to the channel information 10-6. This switching operation will be described with reference to FIG. At the time of this switching, the transmitting terminal 3 has to change the clocks below the video / audio multiplexing device according to the change of the transmission rate. This change is made by the CPU unit 18 in the channel information 1
0 to 6 and control the PLL frequency dividing circuits 152 and 162. In this case, since the use of the line is switched from the use of one line to the use of two lines and the transmission rate is doubled and used, the clock also needs to be doubled. In this way, the write timing of the memories 154 and 164 is changed.
In this way, transmission of a compressed image is supported.

When performing communication of image data, simply encoding a video signal results in a huge amount of data. Therefore, communication is generally performed using an encoding technique for reducing the amount of data. In the case of still images, JPEG is generally used.
A predictive method such as G2 is used. The MPEG2 is also used in the embodiments of the present invention. Here, the concept of operation of predictive coding will be briefly described. In predictive coding, a current image is decoded using past data and future data. FIG. 6 shows this state. If it is desired to decode the image at time T2 in FIG. 6, P1 is the past image data, P3 is the future image, and P2 refers to the data of P1 and P3. That is, in order to decode the image of P2, it is necessary to wait until time T3. As described above, in the present invention, such MP
It is possible to cope with a change in the data transmission rate of a compressed image such as EG2 or JPEG.

The operation when the receiving terminal switches the transmitting terminal that is receiving will be described. In the transmission system of the present embodiment, a plurality of transmission terminals can be selected and communicated with one reception terminal as described above. In addition, line switching at the time of selection is performed instantaneously, so that data streams of different transmitting terminals are continuously received. Therefore, P1
The data and the P3 data may be different transmission terminal data. The receiving terminal decodes P2 using P1 and P3 that have no correlation, and attempts to decode the next image using P2.

Although the receiving terminal itself is decoding normally, as an image, P1 and P3 are not established because P1 and P3 are data of different transmitting terminals. Therefore, it is necessary to notify that the switching has been performed. It is desirable that the image return after switching is as short as possible,
It is conceivable to reset the terminal by the switching signal, but resetting all the functions of the terminal and returning from the initial operation takes a long time, making smooth switching operation difficult. Therefore, it is necessary to consider the line switching function and the restoration function of the image decoding device together.

A communication terminal often has a data error check function and the like, and it is possible to reset only a part of the inside of the device when a data error occurs. Also in the present system, an image decoding device having this function is selected and used together with the image encoding device. The image data stream of this encoding device is a fixed-length packet and is output continuously. Next, a technique for preventing image disturbance at the time of line switching in this embodiment will be described with reference to FIG.

As shown in FIG. 7A, when switching from the transmitting terminal 3 to the transmitting terminal 4, since the unit packet PL of the data stream is a fixed-length packet, the packet header {PLH31, PLH32 switches the next packet header #P
Line switching can be inferred by the disturbance of the timing of LH41. This estimation is performed by the MPEG2 decoder, and the periodicity of the fixed-length packet header is monitored.

In the figure, PL 31 and 32 denote MPEG2 image data from the transmitting terminal 3, and PL 40, 41 and 42.
Is MPEG2 image data from the transmission terminal 4. At this time, the decoder 103 initializes only the decoding operation,
The freeze screen is held until the next image is prepared, thereby coping with the data stream switching. However, in FIG. 7B, since there is no irregular header even when switching from the data PL32 to the data PL40, the packet timing is not disturbed. For this reason, the line switching cannot be estimated and the decoding operation is continued.

According to the present invention, such a phenomenon can be avoided. In order to avoid this phenomenon, the receiving terminal 10 responds by intentionally masking the packet header ゛ when switching the line. The schematic diagram is shown in FIG. 7c. FIG.
In c, since the data PL32 and the data PL40 are masked by the blank data PLB, the initialization of the decoding timing # can be prompted.

Hereinafter, this operation will be described in detail with reference to FIG. In FIG. 8, the MPEG2 data stream shown in FIG. 7 is temporarily stored in the memory 154 and output to the decoder 103 as continuous data. At this time, when the channel is switched, for example, as shown in FIG.
Is changed to data PL40. This switching is notified to the CPU unit 18, and the CPU unit 18 and the channel information 10-6 are updated. 151 informs 155 of the change in the channel information 10-6, and 155 changes the write timing of the memory 154. At this time, in order to insert the blank data as shown in FIG. 7C, the output of the memory 154 is stopped by the change of the channel information 10-6 as a trigger. Since the output of the memory 154 is fixed data, it is possible to set the required number of data to blank data. After the necessary blank data is generated, the output of the memory 154 is activated again.

[0039]

In the loop type digital information transmission system, since a frame time slot is assigned to a node in advance, a transmission system having no delay fluctuation even when distributing image data having a large amount of information is used. Can be built. In addition, since data is not discarded due to congestion, reliability is improved, and a receiving side does not require a device such as a matrix switcher, and selection of output data is easily changed, thereby improving system structurability.

As described above, according to the present invention, it is possible to easily cope with a change in the information transmission rate in the loop type digital information transmission system. Also when transmitting a compressed image due to, for example, it is possible to prevent the image from being disturbed at the time of image switching, freezing, and the like.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram of the present invention.

FIG. 2 is a system configuration diagram of the present invention.

FIG. 3 is a conceptual diagram of a system according to an embodiment of the present invention.

FIG. 4 is a block diagram of an optical multiplex transmission apparatus according to an embodiment of the present invention.

FIG. 5 is a conceptual diagram of a data stream of a trunk line in the embodiment of the present invention.

FIG. 6 is a conceptual diagram of predictive image coding in MPEG2.

FIG. 7 is a conceptual diagram of an image data stream in the embodiment of the present invention.

FIG. 8 is a conceptual diagram of an audio-video multiplexing apparatus according to an embodiment of the present invention.

FIG. 9 is a conceptual diagram of a system in the related art.

FIG. 10 is a conceptual diagram of a system in the related art.

FIG. 11 is a conceptual diagram of a system in the related art.

FIG. 12 is a conceptual diagram of a system in the related art.

FIG. 13 is a conceptual diagram of a system in the related art.

FIG. 14 is a conceptual diagram of a system in the related art.

[Explanation of symbols]

1: trunk line, 3, 4, 5: transmitting terminal device, 10, 2,
0: data receiving terminal, 11, 12: photoelectric signal converter,
13: switch, 14: multiplex interface, 15,
16: video / audio multiplexing circuit, 17: audio unit, 18:
CPU unit, 19: RAS circuit, 100, 100-
2, 100-3, -100-4, 100-10: optical multiplex transmission apparatus, 103, 203: decoder, 2001, 30
01,4001: Encoder, 1F: Frame,

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) H04N 7/18 H04L 11/20 102F F-term (reference) 5C054 AA02 DA01 DA10 EA05 EB02 HA01 HA18 5C059 KK34 MA00 MA05 MA14 PP07 RA02 RA09 RB02 RB14 RC03 RC05 RC09 RC32 RC34 RE04 RE16 RF07 RF15 RF19 SS02 SS06 TA73 TB04 TC21 TC45 TD18 UA02 UA05 UA24 UA34 5K028 AA01 AA12 AA14 BB08 CC06 HH02 HH03 KK01 KK03 KK32 LL12 J0311 AA10 CA09 CB10 CC03 DA15 DA19

Claims (6)

[Claims] In a digital image data transmission system, a plurality of node devices are installed on a transmission line configured in a loop, and the transmission line has a data frame structure delimited by a preset time slot. Information of the node device is assigned to the unit time slot, a data communication transmission system in which the node device sequentially receives and transmits the data frame, the unit time slot to one terminal as needed A multiplex transmission system for digital image data, wherein a plurality of digital image data are allocated. 2. The digital image data multiplex transmission system according to claim 1, wherein said data frame structure comprises a plurality of data slots and a control slot. 3. The data frame structure of a digital image data multiplex transmission system according to claim 2, wherein each of said plurality of data slots comprises image information of each channel, and said control slot includes said image information of each channel. A multiplex transmission system for digital image data, comprising a channel information slot for controlling image information. 4. A digital image data multiplex transmission system according to claim 1, wherein said communication data includes compressed digital image data. 5. In a digital image data transmission system, a plurality of node devices are installed on a transmission line configured in a loop, and the transmission line has a data frame structure delimited by a preset time slot. A data communication transmission system in which the information of the node device is allocated to the unit time slot, and the node device sequentially receives and transmits the data frame, wherein the information includes compressed image data; A multiplex transmission system for digital image data, characterized in that when the assignment of the digital image data is changed, the operation clocks of the decoder and the encoder of the compressed image are changed in accordance with the change. 6. In a digital image data transmission system, a plurality of node devices are installed on a transmission line formed in a loop, and the transmission line has a data frame structure partitioned by a preset time. A data communication transmission system in which predetermined compressed image information of the node device is allocated to the divided unit time slots, and a receiving terminal of the compressed image in the node device receives the compressed image data of the node device. A multiplex transmission system for digital image data, wherein one packet of blank data is inserted at the time of switching.