JP2000165827A - Image communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely re-transmit data to a reception section whose hardware scale can be reduced only when the title system receives a re-transmission request from the reception section and the transmitted data is in-frame coded data. SOLUTION: A coding section 12 applies various coding systems such as in-frame coding, inter-frame coding and 2-way prediction coding to a received moving picture to code the picture as one-frame picture data including one frame coded data and generated code data and gives the resulting data to a coder 14. The coder 14 selects the bit string resulting from storing and reading the received image data or a picture data bit string by one frame received from an input line 106, divides the selected bit string into prescribed lengths, generates picture packets each consisting of picture data and generated cyclic redundancy check CRC codes and controls the transmission of the packets. When a processing section 20 receives a re-transmission request signal from a reception section, checks the coded type of the picture data stored in a buffer circuit 22 and gives the picture data to the coder 14 when the coded type is the in- frame coding system. The coder 14 selects the picture data received via the input line 106, generates packets and re-transmits the packets to the reception section.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image communication system, and more particularly, to a transmission unit of an image communication apparatus to which an error detection and retransmission correction method is applied via a transmission path having a transmission error and a reception unit of the image communication apparatus. The present invention relates to an image communication system suitable for transmitting moving image data encoded between the image data.

[0002]

2. Description of the Related Art In general, the waveform of transmitted information (data) is distorted by Gaussian noise, attenuation distortion, group delay distortion, phase jitter, impulsive noise, and the like during transmission through a data transmission line. This causes a bit error. Therefore, in data transmission, the transmitted information may arrive at the receiving side by mistake. For this reason, in data transmission, error control for detecting an error in received information and correcting the error to correct information is performed. For this error control, an error detection retransmission correction method (ARQ: Automatic Repeat Request) is generally used.

In this error detection / retransmission / correction system, the transmitting side adds redundant bits, for example, CRC (Cyclic Redunda
(ncy Check) code is sent to the receiving side, and the receiving side checks this redundant bit to detect whether or not there is an error. Considering this, a retransmission request signal requesting that the data be discarded and transmitted again is sent to the transmitting side, and the transmitting side adds redundant bits to the retransmitted transmission data and sends it to the receiving side again.

A moving image data transmission apparatus for transmitting and receiving moving image data by applying such an error detection / retransmission / correction method is disclosed, for example, in Japanese Patent Application Laid-Open No. 8-294123. In this moving image data transmission device, encoding is performed to reduce the amount of image information. For this encoding, intra-frame encoding, inter-frame encoding, and bidirectional predictive encoding are used.

[0005] Explaining these encodings, intra-frame encoding performs encoding using only information in each frame, and inter-frame encoding blocks only the motion from a past frame between consecutive frames. (For example, 16 × 16 pixels), a motion vector is calculated, and the motion vector is calculated. Is encoded.

[0006] The method described in claim 2 of this document will be described. The transmitting apparatus stores coded data coded by one of these coding methods for each frame (one screen). Then, the stored encoded data is read, and information (encoding type) indicating the encoding type of the frame and information for error control (redundant bits) are added to the read encoded data, and the reception side device is added. When the receiving-side apparatus receives the intra-frame encoded data indicated by the encoding type and detects that there is a transmission error due to the redundant bit, it requests the retransmission of the intra-frame encoded data. Is transmitted to the transmitting device, and the transmitting device transmits the intra-frame coded data that has received the retransmission request to the receiving device again.

In other words, the moving image data transmission device described in this document requests a retransmission only when an error occurs in intra-frame encoded data.

FIG. 5 shows an example of the configuration of a receiving section of a conventional receiving apparatus in a system for transmitting and receiving moving image data. The operation of this device will be described.

This apparatus has a multiplexed bit string input terminal 502. In this example, an image packet and audio packetized by a packet length of a predetermined number of bytes from a transmitting side apparatus (not shown) are connected to this input terminal 502. A time-division multiplexed signal of the packet is supplied, and this signal is sent to a multiplexed bit string reception buffer circuit 504.

In this example, the image packet is multiplexed in the order of a synchronization signal, identification information indicating that it is an image packet, image data, and a CRC code, and the audio packet is also a synchronization signal and an audio packet. Are multiplexed in the order of identification information, audio data, and CRC code.

The one-frame image signal is composed of a plurality of the above-described image packets. In this example, the format of the one-frame image signal is one frame of coded data, the coding type of the coded data, A frame sequence number (SN) is multiplexed. The multiplexed data is multiplexed at the position of the image data of the image packet.

The reception buffer circuit 504 is constituted by a storage circuit having a capacity for storing at least the number of bits in the above-described packet length. This storage circuit temporarily stores the data of the sequentially transmitted image or audio packet, The temporarily stored data is read out and sent to the system multiplex decoder 506.

The system multiplex decoder 506 has an image / audio packet separation circuit. This separation circuit identifies the image or audio attribute multiplexed in the header portion of the sequentially transmitted packet. , The image packet or the audio packet is identified, and the image packet and the audio packet are separated and output. The separated voice packet is output to a signal line (not shown), and the separated image packet is output to the coding type detection unit 508, the standby buffer circuit 510, and the selector circuit 512.

The system multiplex decoder 506 also has a circuit for detecting the above sequence number, and the sequence number detected by this circuit is sent to the retransmission request judging section 320. The system multiplex decoder 506 further includes a circuit for checking the above-described CRC code, and data resulting from the check by this circuit is sent to the retransmission request determination unit 520. In this case, the inspection result data includes data indicating normal reception and data indicating abnormal reception (error).

An encoding type detection unit 508 detects an encoding type from the separated image packets sent from the system multiplex decoder 506 and sends it to a retransmission request determination unit 520. In this example, in this case, the detected encoding types include an intra-frame encoding type, an inter-frame encoding type,
There are three types of bidirectional predictive coding types.

The standby buffer circuit 510 comprises a storage circuit having a capacity to store the number of bits of a plurality of image packets including at least one frame of image signal, and this storage circuit is provided with an image transmitted from the system multiplex decoder 506. The packet data is temporarily stored, and the temporarily stored data is read and sent to the selector circuit 512.

The selector circuit 512 is provided with a system multiplex decoder 506 based on the control signal sent from the retransmission request judging section 520.
Is a switching circuit that connects the output of the video decoding unit 514 to the input of the video decoding unit 514 or the output of the standby buffer circuit 510 to the input of the video decoding unit 514.

The moving picture decoding unit 514 is a circuit for decoding the coded picture data while referring to the coding type information of each frame sent from the selector circuit 512. The decoded image data is sent to an image signal output terminal 516.

As mentioned earlier, retransmission request determining section 520 receives the coding type information from coding type detecting section 508, and receives a result of checking the sequence number and CRC code from system multiplexing decoder 506. Receive data.

The retransmission request determining unit 520 determines whether the data obtained as a result of checking the received CRC code is data indicating normal reception.
Or a determination circuit that determines whether the data indicates an error, and a determination circuit that determines what type of information of the encoding type received when the determination circuit determines that the data indicates an error. A retransmission request signal to be transmitted when the determination circuit determines that the type is the intra-frame encoding type is generated, and the received sequence number and the generated retransmission request signal are transmitted through a retransmission request signal output terminal 518. A retransmission signal generation circuit to be sent to a device on the
And a control signal generation circuit for generating a control signal to be sent to the control signal generator 2.

That is, also in the case of the apparatus shown in FIG. 5, a retransmission request is issued together with a sequence number only when an error occurs in intra-frame encoded data.

[0022]

As described above, in the method of determining the coding type in the receiving section of the apparatus and requesting retransmission, if the coding type information itself has an error, the information is actually transmitted. There is a problem that it is impossible to know what the encoding type is. That is, for example, if the transmitted intra-frame coding type is erroneously set to the inter-frame coding type, there is a problem that a retransmission request is not issued. When it becomes a generalization type,
There was a problem that a retransmission request was issued.

Providing the function of detecting the coding type in the receiving section of the apparatus and issuing or not issuing a retransmission request based on this detection complicates the circuit configuration of the receiving section and increases the hardware There was a problem of increasing the scale. This is particularly problematic for receive-only devices.

The present invention solves the above-mentioned drawbacks of the prior art, and provides a receiving section of an image communication apparatus capable of reducing a hardware scale by simplifying a circuit configuration for detecting a transmission error and making a retransmission request. An image communication apparatus comprising: a transmission unit of an image communication device capable of reliably retransmitting only when transmitted coded data is intra-frame coded data when a retransmission request is received from a reception unit of the device; The purpose is to provide a system.

[0025]

According to the present invention, in order to solve the above-mentioned problems, a transmission unit of an image communication device is connected to a reception unit of the image communication device via a transmission line, and the transmission unit transmits a moving image to the reception unit. In an image communication system that sends an image and the receiving unit responds to the transmitting unit based on the received moving image, the transmitting unit includes:
Encoding that applies an intra-frame encoding method or an encoding method other than this encoding method to each frame of a sequentially input moving image frame by frame in a predetermined order, and indicates an encoding method applied to the encoding. Generate data of type
Encoding means for outputting data including one encoded frame of encoded data and generated encoding type data as one frame of image data, and inputting one frame of image data from a first input port Then, one frame of image data output from the encoding means is input from the second input port and stored, and the stored one frame of image data is read out or input from a first input port or a bit string. One of the bit strings of the image data for one frame is selected, the bit string of the selected image data is divided into a predetermined length, and encoded data for error detection corresponding to the divided image data is generated. A multi-encoding means for forming an image packet composed of the divided image data and the generated encoded data, and controlling transmission of the formed image packet; A storage unit for receiving and storing one frame of image data stored and read out by the multiplex encoding unit corresponding to the image packet just transmitted to the reception unit by the transmission control of the encoding unit; If the transmitted response is found to be a retransmission request signal, the encoding type data included in the image data for one frame stored in the storage unit is examined, and the data indicates the intra-frame encoding method. Retransmission processing means for reading out one frame of image data stored in the storage means and sending the image data to the first input port, and the multiplex encoding means transmits the image data to the first input port from the retransmission processing means. When one frame of image data is sent, this image data is selected, an image packet based on the selected image data is formed, and the formed image packet is retransmitted to the receiving unit. To.

The receiving section receives the image packet transmitted from the multiplex coding means, checks coded data added to the received image packet for error detection, and checks the data of the image packet received by the check. If it is determined that there is an error, a retransmission request signal is generated as a response, and an error detection unit that sends the generated retransmission request signal to the retransmission processing unit is provided.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of an image communication system according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows functional blocks of a first embodiment of the transmitting section of the image communication apparatus in the image communication system of the present invention. Referring to FIG. 1, the transmitting unit includes an image signal input terminal 10, a moving image encoding unit 12, a system multiplex encoder 14, a multiplexed bit string output terminal 16, a retransmission request signal input terminal 18, a retransmission processing unit 20, and a buffer. It is composed of a circuit 22.

When the transmitting section of FIG. 1 receives a retransmission request signal from the receiving section of the image communication apparatus on the receiving side (not shown) at a retransmission request signal input terminal 18, the retransmission processing section 20 operates as a buffer circuit.
Reference is made to the coding type of the encoded data of one frame stored in 22. If the reference result indicates that the coding type is the intra-frame coding type, the encoded data of one frame stored therein is read out. And retransmitting to the receiving section of the receiving side device via the multiplexed bit string output terminal 16.

A video (image) signal of a moving image from a television camera (not shown) is input to the image signal input terminal 10, for example. The input of the video encoding unit 12 is connected to the image signal input terminal 10 via a signal line 102, and the video encoding unit 12 converts an analog image signal input from the input 102 into a corresponding digital image signal, and performs conversion. One frame of image signal data including the encoded data encoded by one of the intra-frame encoding method, the inter-frame encoding method, and the bidirectional predictive encoding method. To the system multiplex encoder 14 via the signal line 104.

Here, the encoded data for each frame sequentially output from the video encoding unit 12 will be described.
For example, with respect to the image signal data of one frame first input to the encoding unit 12, the intra-frame coding method is applied to output the intra-frame encoded data. Outputs bidirectional predictive encoded data by applying bidirectional predictive coding,
The order of the output encoding schemes may be determined in advance so that the inter-frame encoding scheme is applied to the third input image signal data of the next frame to output inter-frame encoded data. .

The one-frame image signal data sequentially output from the moving image encoding unit 12 includes, in addition to the above-described one-frame encoded data, the encoded data generated by the encoding unit 12. And the frame sequence number.

In this example, there are three types of coded data output from the moving picture coding unit 12, an intra-frame coding method, an inter-frame coding method, and a bidirectional predictive coding method. However, there may be two types of intra-frame coding systems and inter-frame coding systems, or several types of intra-frame coding systems and coding systems other than the inter-frame coding system and the bidirectional predictive coding system. .

The system multiplex encoder 14 has a storage circuit for storing one frame of image signal data sequentially input from the input 104. This storage circuit sends the stored image signal data for one frame to the buffer circuit 22 via the readout signal line 110.

This storage circuit is used when the retransmission processing unit 20 sends one frame of image signal data stored in the buffer circuit 22 to the system multiplex encoder 14 via the signal line 106 in response to a retransmission request as described later. In the meantime, it has a capacity to store one frame of image signal data output from the moving image encoding unit 12. The storage circuit also has a capacity to store one frame of image signal data output from the moving image encoding unit 12 while audio packets are being multiplexed, as described later.

The system multiplexing encoder 14 also has an image packetizing circuit, and the image packetizing circuit reads one frame of image signal data read from the above-mentioned storage circuit or one frame inputted from the input 106 in response to a retransmission request. An image packet is generated by dividing the image signal data into a stream of an appropriate bit or byte length. More specifically, in this image packet, in addition to the above-described divided image signal data, a synchronization signal generated by an image packetizing circuit, identification information indicating that the packet is an image packet, a CRC code, and the like are described above. It may be included in the multiplexing position as described above.

The system multiplexing encoder 14 also has a packet multiplexing circuit. The packet multiplexing circuit appropriately time-divides an image packet sent from the above-described image packetizing circuit and an audio packet input from a signal line (not shown). This is a circuit for multiplexing. The packet output from the multiplexing circuit is sent to the receiving side device via the signal line 108 and the multiplexed bit string output terminal 16.

The system multiplex encoder 14 also has a transmission control circuit. The transmission control circuit has a circuit for forming, for example, a transmission request signal and a transmission end signal, and the formed transmission request signal is transmitted prior to transmission of a packet. The transmission end signal is sent to the receiving side device via the signal line 108 and the multiplexed bit string output terminal 16 after the data transmission is completed. The transmission control circuit also receives the input terminal 18 and the signal line 11 from the receiving device.
Control signal for receiving various response signals including a retransmission request signal transmitted via the line 6 and data and control signals transmitted via the signal line 106, and controlling each unit based on the received response signal, data and control signal. Is also provided.

The buffer circuit 22 has a storage circuit having a capacity for storing at least one frame of image signal data input from the input 110. This storage circuit stores one frame of image signal data input from the input 110. The data stored in the storage circuit is read based on a read control signal sent from the retransmission processing unit 20 via the control line 112. The read data is sent to the retransmission processing unit 20 via the signal line 114.

As mentioned earlier, various response signals including a retransmission request signal from a receiving side device (not shown) are input to the retransmission request signal input terminal 18. The input of the retransmission processing unit 20 is connected to the retransmission request signal input terminal 18 via a signal line 116, and the retransmission processing unit 20 has a detection circuit for detecting the retransmission request signal among the response signals input from the input 116. Retransmission processing unit 20
Receives a signal indicating that the retransmission request signal has been detected from the detection circuit, and responds to the signal to indicate that the buffer circuit 22 has received the signal.
And a read control signal generating circuit for generating a read control signal for reading data stored in the memory. The read control signal generated by this circuit is sent to the buffer circuit 22 via the control line 112.

The input 114 of the retransmission processing unit 20 receives the one read from the buffer circuit 22 by the above read control signal.
Image signal data for a frame is input. Retransmission processing unit
20 also extracts the coding type included in the image signal data of one frame input from the input 114, and investigates the type of the extracted coding type. In the case of an intra-frame encoding type, an instruction signal for generating a read control signal in the above-described read control signal generation circuit and sending it to the buffer circuit 22 is formed. In the case of the bidirectional predictive coding type, the control circuit for forming a signal to be sent to the signal line 106 indicating that retransmission is not performed is provided.

The control circuit of the retransmission processing section 20 also includes a circuit for transmitting one frame of image signal data read out from the buffer circuit 22 again and input from the input 114 to the signal line 106 for retransmission by an instruction of this circuit. ing. When the control function unit of the system multiplex encoder 14 determines that the signal input through the signal line 106 is image signal data,
This control function unit sends a control signal for retransmitting one frame of image signal data input via the signal line 106 to each unit. Thereby, the same image signal data of one frame transmitted immediately before is divided, packetized, and transmitted to the receiving side device.

If the control function of the system multiplex encoder 14 determines that the signal input via the signal line 106 is a signal indicating not to be retransmitted, the control function of the system multiplex encoder 14 Of one frame of image signal data which is stored in the storage circuit and is waiting to be read out from the storage circuit. The image signal data for one frame read by this instruction is sent to the image packetizing circuit and the buffer circuit 22 of the system multiplex encoder 14 as in the normal operation. Therefore, the sequence number of the image signal data of one frame output from the multiplexed bit string output terminal 16 is the number following the sequence number of the image signal data of one frame transmitted immediately before.

When there is no signal input from the input 106, the control function unit of the transmission control circuit of the system multiplex encoder 14 stores the signal in the system multiplex encoder 14 based on the response signal input from the input 116. An instruction to sequentially read one frame of image signal data sequentially stored in the circuit is issued.

First, the operation of the first embodiment in FIG. 1 will be described using a normal operation sequence in data transmission shown in FIG.

The transmission control circuit of the system multiplex encoder 14 generates a transmission request signal prior to data transmission and sends it to the receiving section of the receiving device. Upon receiving this, the receiving unit sends a transmission response signal to the transmitting device because the reception is OK. This transmission response signal is sent to the transmission control circuit of the system multiplex encoder 14 via the retransmission request signal input terminal 18 on the transmitting side and the signal line 116. By transmitting and receiving the transmission request and the transmission response, a data link between the transmitting apparatus and the receiving apparatus is established.

Upon receiving the transmission response signal, the transmission control circuit of the system multiplex encoder 14 sends a transmission start signal # 1 to the storage circuit of the system multiplex encoder 14. When the storage circuit receives the transmission start signal # 1, it stores the encoded data for one frame and the image signal data for one frame including the encoding type thereof into the image packetizing circuit and the buffer circuit of the system multiplex encoder 14. Send to 22. This first frame is intra-frame coded data because inter-frame coding or the like cannot be used.

The buffer circuit 22 stores the received image signal data for one frame. The image packetizing circuit divides the received image signal data for one frame into an appropriate bit or byte length stream, generates an image packet in which a CRC code is added to the divided image signal data, and Send to the department.

The receiving unit of the receiving apparatus sequentially determines whether or not there is a transmission error in the sequentially received image packets, thereby determining whether or not there is a transmission error in the finally received image signal data for one frame. . In the case of FIG. 2, since the operation is normal, the receiving unit of the receiving-side apparatus determines that the reception result is normal, and based on this determination, sends a response signal # 1 indicating normal reception to the system-side multiplex coding of the transmitting side. To the transmission control circuit of the device 14.

As can be seen from the above, the function of the receiving section of the image communication apparatus for determining whether or not to send the retransmission request signal to the transmitting side is to check the CRC code in this example to determine whether or not there is an error. What is necessary is just the function of detecting whether or not. Therefore, the configuration of the receiving unit of the image communication apparatus can be simplified and the hardware scale can be reduced as compared with the related art.

When receiving the response signal # 1, the transmission control circuit of the system multiplex encoder 14 sends a transmission start signal # 2 to the storage circuit of the system multiplex encoder 14. The operations after the second transmission start signal # 2 are basically the same as the operations performed based on the first transmission start signal # 1.

That is, the storage circuit sends the encoded data for one frame and the image signal data for one frame including the encoding type to the buffer circuit 22 and the image packetizing circuit of the system multiplex encoder 14. However, the encoded data to be transmitted is inter-frame encoded data or bidirectional predictive encoded data in this example.

The buffer circuit 22 stores the received inter-frame coded data for one frame or the received image signal data including bidirectional predictive coded data. The image packetizing circuit divides the received image signal data containing one frame of inter-frame coded data or bidirectional predictive coded data into a stream of appropriate bits or bytes, and converts the divided image signal data into a CRC code. Is generated and sent to the receiving device.

Next, the operation of the first embodiment in FIG. 1 will be described using an abnormal operation sequence in data transmission shown in FIG.

The transmission and reception of the transmission request and the transmission response establishes the data link between the transmitting device and the receiving device. Once established, a transmission start signal # 1 is sent from the transmission control circuit of the system multiplex encoder 14 to the storage circuit of the system multiplex encoder 14. The storage circuit receiving the transmission start signal # 1 stores the intra-frame coded data for one frame and the image signal data for one frame including the coding type thereof in the buffer circuit 22 and the image packet of the system multiplex encoder 14. To the conversion circuit. The buffer circuit 22 stores the transmitted image signal data for one frame, and the image packetizing circuit divides the transmitted image signal data for one frame into a stream of an appropriate bit or byte length and divides the stream. An image packet in which a CRC code is added to the image signal data is generated and sent to the receiving unit of the receiving device. Up to this point, the sequence is the same as the normal operation sequence shown in FIG.

The receiving unit of the receiving apparatus sequentially detects the presence or absence of a transmission error in the sequentially received image packets, and determines whether or not there is a transmission error in the finally received image signal data for one frame. . In the case of FIG. 3, since the operation is abnormal, the receiving unit of the receiving apparatus determines that the reception result is abnormal, and transmits a retransmission request signal # 1 which is a response signal indicating abnormal reception based on the determination to the transmitting side. To the retransmission processing unit 20 of the system multiplex encoder 14.

The detection circuit of the retransmission processing unit 20 detects that the transmitted signal is a retransmission request signal, and sends this detection signal to the read control signal generation circuit of the retransmission processing unit 20. Upon receiving the detection signal, the read control signal generation circuit generates a read control signal and sends the generated read control signal to the buffer circuit 22.

Thus, the image signal data for one frame read from the buffer circuit 22 is sent to the control circuit of the retransmission processing unit 20. The control circuit extracts a coding type included in the transmitted image signal data for one frame, and checks which coding type is the extracted coding type. In the case of the intra-frame encoding type, an instruction signal for generating a read control signal and sending it to the buffer circuit 22 is sent to the read control signal generation circuit of the retransmission processing unit 20 described above. In addition, as a result of this investigation, a signal indicating that retransmission is not to be performed is transmitted to the signal line 106 if the interframe coding type other than the intraframe coding type or the bidirectional predictive coding type is used.

In this case, since the coding type determined by the examination is the intra-frame coding type, the control circuit of the retransmission processing unit 20 transmits one frame of image signal data read from the buffer circuit 22 via the signal line 106. To the transmission control circuit of the system multiplex encoder 14. The transmission control circuit is a signal line 106
Since the signal input through the interface is image signal data, it is determined that the data is retransmission data, and a control signal for transmitting the data is transmitted to each unit. Thereby, the same image signal data of one frame transmitted immediately before is divided, packetized, and transmitted to the receiving unit of the receiving side device.

According to the first embodiment, one frame of image signal data just transmitted from the transmission unit of the image communication apparatus is stored in the buffer circuit 22 without exception. When there is a retransmission request from the receiving unit of the receiving-side apparatus for the just-transmitted one-frame image signal data, the retransmission processing unit 20 encodes the one-frame image signal data stored in the buffer circuit 22. Investigate the type. In this investigation, if the intra-frame encoding type, the image signal data for one frame stored in the buffer circuit 22 is transmitted, and if the intra-frame encoding type, the image signal data for the next frame to be transmitted next is transmitted. Transmit image signal data. As described above, even if a retransmission request is issued by a simple circuit of the receiving unit, there is an effect that retransmission can be reliably performed only when the transmitted coding type is the intra-frame coding type.

FIG. 4 shows a functional block diagram of a second embodiment of the transmitting section of the image communication apparatus in the image communication system of the present invention. Referring to FIG. 4, the transmitting unit includes an image signal input terminal 10, a moving image encoding unit 12, a system multiplex encoder 14, a multiplexed bit string output terminal 16, a retransmission request signal input terminal 18, a retransmission processing unit 20, It comprises a storage determination unit 30 and a buffer circuit 32.

As can be seen from the above description, FIG. 4 differs from FIG. 1 in that a data storage judgment unit 30 is added and that the buffer circuit 22 in FIG.
In FIG. 1, the storage circuit of the system multiplex encoder 14 is connected to the buffer circuit 22 via a signal line 110 in FIG. 1, but in FIG. 4, the storage circuit of the system multiplex encoder 14 is connected to a signal line. 110 and is connected to the data storage determination unit 30 via
The data storage judging unit 30 is connected to the buffer circuit via the signal line 130.
It is connected to 32. In FIG. 4, the same reference numerals are given to the portions corresponding to FIG.

The data storage judging section 30 judges what the coding type of the coded data in the image signal data for one frame sent from the storage circuit of the system multiplex encoder 14 is. When it is determined that the image signal is of the encoding type, the transmitted image signal data for one frame is sent to the buffer circuit 32. When it is determined that the image signal data is not of the intra-frame encoding type, the buffer circuit 32
In this example, an instruction signal for instructing the storage area of the storage circuit to store the data “0” is sent to the buffer circuit 32.

The buffer circuit 32 is the same as the buffer circuit 22 of FIG. 1 in that the sent image signal data for one frame is stored. The difference from the buffer circuit 22 of FIG. 1 is that the above-mentioned instruction signal is sent. In this case, the function of storing the data “0” in this example in the storage area of the storage circuit of the buffer circuit 32 It is to have. That is, it has a delete function.

That is, one frame of image signal data is stored in the buffer circuit 32 for only the intra-frame encoding type just transmitted from the transmission unit of the image communication apparatus. The reason why the data “0” is stored in the buffer circuit 32 is to reliably retransmit one frame of the intra-frame coding type image signal data when a retransmission request is received from the receiving unit of the receiving device. .

More specifically, when one frame of image signal data of a type other than the intra-frame encoding type is transmitted from the transmission unit of the image communication device, the data in the storage circuit of the buffer circuit 32 is not set to “0”. In this case, the data of the previous intra-frame encoding type remains stored in the storage circuit of the buffer circuit 32 until the next intra-frame encoding type comes. In this state, if the data just transmitted from the transmission unit of the image communication device is data other than the intra-frame coding type, and if there is a retransmission request from the reception unit of the reception side device at this time, the buffer circuit 32 The data of the intra-frame encoding type stored in the storage circuit will be retransmitted. That is, the data is set to "0" in order to avoid such retransmission.

In this example, when the data storage judging unit 30 judges that the data is not of the intra-frame coding type, an instruction signal for instructing the buffer circuit 32 to store “0” data is sent. Alternatively, when the data storage determining unit 30 determines that the data is not the intra-frame encoding type, the data of “0” may be transmitted to the buffer circuit 32. Also, in this case, after it is determined that the frame is of the intra-frame coding type, and if it is determined that the frame is not the first intra-frame coding type, data of “0” is sent. Until the determination, even if it is determined that the type is not the intra-frame encoding type, a method of not sending data of “0” may be used. In these cases, the function of the buffer circuit 32 may be the same as the function of the buffer circuit 22 in FIG.

In this example, the instruction signal is sent every time it is determined that the frame is not the intra-frame coding type. However, after the determination is made that the frame is the intra-frame coding type, the first intra-frame coding type is transmitted. If it is determined that the type is not the intra-frame encoding type, the instruction signal may be sent, and thereafter, the instruction signal may not be transmitted even if it is determined that the type is not the intra-frame encoding type until the intra-frame encoding type is determined. In this example, the data to be stored is “0” data. However, any code data may be used as long as it can be distinguished from intra-frame encoding type data.

First, the operation of the second embodiment in FIG. 4 will be described using a normal operation sequence in data transmission shown in FIG.

The transmission control circuit of the system multiplex encoder 14 generates a transmission request signal before transmitting data, and sends it to the receiving section of the receiving device. Upon receiving this, the receiving unit sends a transmission response signal to the transmitting device because the reception is OK. This transmission response signal is sent to the transmission control circuit of the system multiplex encoder 14 via the retransmission request signal input terminal 18 on the transmitting side and the signal line 116. By transmitting and receiving the transmission request and the transmission response, a data link between the transmitting apparatus and the receiving apparatus is established.

When receiving the transmission response signal, the transmission control circuit of the system multiplex encoder 14 sends a transmission start signal # 1 to the storage circuit of the system multiplex encoder 14. When the storage circuit receives the transmission start signal # 1, it stores the encoded data for one frame and the image signal data for one frame including the encoding type thereof in the image packetizing circuit of the system multiplex encoder 14 and data storage. It is sent to the judgment unit 30. This first frame is intra-frame coded data because inter-frame coding or the like cannot be used.

The data storage judging section 30 judges what the encoding type of the encoded data is in the transmitted image signal data for one frame. Since the determination result is the intra-frame encoding type in this case, the transmitted image signal data for one frame is transmitted to the buffer circuit 32.

The buffer circuit 32 stores the received image signal data for one frame. The image packetizing circuit divides the received image signal data for one frame into an appropriate bit or byte length stream, generates an image packet in which a CRC code is added to the divided image signal data, and Send to the department.

The receiving unit of the receiving apparatus sequentially determines whether or not there is a transmission error in the sequentially received image packets, thereby determining whether or not there is a transmission error in the finally received image signal data for one frame. . In the case of FIG. 2, since the operation is normal, the receiving unit of the receiving-side apparatus determines that the reception result is normal, and based on this determination, sends a response signal # 1 indicating normal reception to the system-side multiplex coding of the transmitting side. To the transmission control circuit of the device 14.

When the transmission control circuit of the system multiplex encoder 14 receives the response signal # 1, it sends a transmission start signal # 2 to the storage circuit of the system multiplex encoder 14. The storage circuit contains one frame of encoded data and its encoding type.
The image signal data for the frame is sent to the data storage determining unit 30 and the image packetizing circuit of the system multiplex encoder 14. However, the encoded data to be transmitted is inter-frame encoded data or bidirectional predictive encoded data in this example.

The data storage judging section 30 judges what the encoding type of the encoded data in the transmitted image signal data for one frame is. In this case, since the judgment result is not the intra-frame coding type, the buffer circuit
In this example, an instruction signal for instructing the storage area of the 32 storage circuits to store the data “0” is sent to the buffer circuit 32.

The buffer circuit 32 stores data "0" in this example in the storage area of the storage circuit. The image packetizing circuit divides the received image signal data containing one frame of inter-frame coded data or bidirectional predictive coded data into a stream of appropriate bits or bytes, and converts the divided image signal data into a CRC code. Is generated and sent to the receiving device.

Next, the operation of the second embodiment in FIG. 4 will be described using the abnormal operation sequence in data transmission shown in FIG.

The transmission and reception of the transmission request and the transmission response establishes the data link between the transmitting device and the receiving device. Once established, a transmission start signal # 1 is sent from the transmission control circuit of the system multiplex encoder 14 to the storage circuit of the system multiplex encoder 14. Upon receiving the transmission start signal # 1, the storage circuit stores the intra-frame coded data for one frame and the image signal data for one frame including the coding type thereof in the data storage determining unit.
30 and the image multiplexing circuit of the system multiplex encoder 14.

The data storage judging section 30 judges what the encoding type of the encoded data in the transmitted image signal data for one frame is. Since the determination result is the intra-frame encoding type in this case, the transmitted image signal data for one frame is transmitted to the buffer circuit 32. The buffer circuit 32 stores the received image signal data for one frame. The image packetizing circuit divides the received image signal data for one frame into an appropriate bit or byte length stream, generates an image packet in which a CRC code is added to the divided image signal data, and Send to the department. Up to this point, the operation sequence is the same as the normal operation sequence.

The receiving unit of the receiving apparatus sequentially determines whether or not there is a transmission error in the sequentially received image packet, thereby determining whether or not there is a transmission error in the finally received image signal data for one frame. . In the case of FIG. 3, since the operation is abnormal, the receiving unit of the receiving apparatus determines that the reception result is abnormal, and transmits a retransmission request signal # 1 which is a response signal indicating abnormal reception based on the determination to the transmitting side. To the retransmission processing unit 20 of the system multiplex encoder 14.

The detection circuit of retransmission processing section 20 detects that the transmitted signal is a retransmission request signal, and sends this detection signal to the read control signal generation circuit of retransmission processing section 20. Upon receiving the detection signal, the read control signal generation circuit generates a read control signal, and sends the generated read control signal to the buffer circuit 32.

As a result, the image signal data for one frame read from the buffer circuit 32 is sent to the control circuit of the retransmission processing unit 20. The control circuit extracts a coding type included in the transmitted image signal data for one frame, and checks which coding type is the extracted coding type. In the case of the intra-frame encoding type, an instruction signal for generating a read control signal and sending it to the buffer circuit 32 is sent to the read control signal generation circuit of the retransmission processing unit 20 described above. In addition, as a result of this investigation, a signal indicating that retransmission is not to be performed is transmitted to the signal line 106 if the interframe coding type other than the intraframe coding type or the bidirectional predictive coding type is used.

In this case, since the coding type determined by the check is the intra-frame coding type, the control circuit of the retransmission processing unit 20 transmits one frame of image signal data read from the buffer circuit 32 via the signal line 106. To the transmission control circuit of the system multiplex encoder 14. The transmission control circuit is a signal line 106
Since the signal input through the interface is image signal data, it is determined that the data is retransmission data, and a control signal for transmitting the data is transmitted to each unit. Thereby, the same image signal data of one frame transmitted immediately before is divided, packetized, and transmitted to the receiving unit of the receiving side device.

According to the second embodiment, if the data just transmitted from the transmission unit of the image communication device is the intra-frame encoding type data, the buffer circuit 32 stores the image of one frame. The signal data is stored, and otherwise, data of "0" is stored. And
When there is a retransmission request from the receiving unit of the receiving apparatus for the image signal data of one frame just transmitted, the retransmission processing unit
20 checks the encoding type of one frame of image signal data stored in the buffer circuit 32. In this investigation, if it is the intra-frame encoding type, the image signal data for one frame stored in the buffer circuit 32 is transmitted. If it is not the intra-frame encoding type, the image signal data for the next frame to be transmitted next is transmitted. Transmit image signal data. As described above, even if a retransmission request is issued by a simple circuit of the receiving unit, there is an effect that retransmission can be reliably performed only when the transmitted coding type is the intra-frame coding type.

Although the embodiments are directed to an image communication system for transmitting a moving image in one direction, an image communication apparatus having a transmission unit and a reception unit according to the present invention is installed, for example, between two points to enable bidirectional communication. An image communication system for transmitting a moving image to a computer may be used.

[0087]

As described above, according to the present invention, in the transmitting section, the storage means stores the data in the multiplex coding means corresponding to the image packet just transmitted to the receiving section by the transmission control of the multiplex coding means. The retransmission processing unit receives and stores the image data of one frame read and read, and if the retransmission processing unit finds that the response transmitted from the receiving unit is a retransmission request signal, the retransmission processing unit stores The encoding type data included in the image data is checked, and if the data indicates the intra-frame encoding method, one frame of image data stored in the storage means is read out and the first input port is read. When the multiplex encoding unit receives one frame of image data from the retransmission processing unit to the first input port, the multiplex encoding unit selects the image data, and selects an image packet based on the selected image data. Forming a retransmits the image packet formed in the receiving portion. In this way, when there is a retransmission request, the transmitting unit can effectively retransmit only when the encoding type of the image data just transmitted is the intra-frame encoding method.

As described above, according to the present invention, in the transmitting section, the data storage judging section controls the transmission of the multiplex encoding section by the multiplex encoding section corresponding to the image packet just transmitted to the receiving section. One frame of image data stored and read out is received, and coding type data included in the received one frame of image data is examined. This data indicates an intra-frame coding method. If present, the received image data for one frame is output. If the data does not indicate the intra-frame coding method, at least image data having a predetermined value different from the coding type data value indicating the intra-frame coding method is stored. When the image data for one frame is sent from the data storage determining means, the image signal is generated and output. The data is stored, and when an instruction signal is transmitted, image data of a predetermined value is generated and stored. The retransmission processing unit determines that the response transmitted from the receiving unit is a retransmission request signal. , Stored in the storage means
The coding type data included in the image data for the frame is examined, and if this data indicates the intra-frame coding method, the image data for one frame stored in the storage means is read out and the first data is read out. Multiplexing means selects the image data when one frame of image data is sent from the retransmission processing means to the first input port, and forms an image packet based on the selected image data. Then, the formed image packet is retransmitted to the receiving unit. Also in this case, when there is a retransmission request, the transmission unit can effectively retransmit only when the encoding type of the image data just transmitted is the intra-frame encoding method.

According to the present invention, as described above, in the transmitting section, the data storage judging means uses the multiplex coding means corresponding to the image packet just transmitted to the receiving section by the transmission control of the multiplex coding means. One frame of image data stored and read out is received, and coding type data included in the received one frame of image data is examined. This data indicates an intra-frame coding method. If present, the received image data for one frame is output, and if the data does not indicate the intra-frame coding method, at least image data having a predetermined value different from the data value of the coding type indicating the intra-frame coding method is generated. The storage means stores the image data when one frame of image data is sent from the data storage determination means, and outputs the image data having a predetermined value. Stores the image data of the predetermined value when the over data is sent, the retransmission processing means seen that the response sent from the reception unit is a retransmission request signal,
The encoding type data included in the image data for one frame stored in the storage means is examined, and if this data indicates the intra-frame encoding method, the data for one frame stored in the storage means is examined. The image data is read out and sent to a first input port, and the multiplex encoding means selects this image data when one frame of image data is sent from the retransmission processing means to the first input port, and selects the selected image data. An image packet based on the data is formed, and the formed image packet is retransmitted to the receiving unit. Also in this case, when there is a retransmission request, the transmission unit can effectively retransmit only when the encoding type of the image data just transmitted is the intra-frame encoding method.

According to the present invention, the receiving unit for the above-mentioned transmitting unit receives the image packet transmitted from the multiplex coding unit, and detects the error added to the received image packet. Inspection of the coded data of the image packet, and when it is determined that there is an error in the data of the received image packet by this inspection, a retransmission request signal is generated as a response, and the generated retransmission request signal is transmitted to the retransmission processing means. Having means. As described above, since the function of the error detecting means is smaller than that of the conventional error detecting function, the hardware scale can be reduced. Therefore, the hardware scale of the receiving unit can be effectively reduced.

[Brief description of the drawings]

FIG. 1 is a functional block diagram of a first embodiment of a transmission unit of an image communication device in an image communication system of the present invention.

FIG. 2 is a diagram showing an example of a normal operation sequence of the embodiment in FIGS. 1 and 4;

FIG. 3 is a diagram showing an example of an abnormal operation sequence of the embodiment in FIGS. 1 and 4;

FIG. 4 is a functional block diagram of a second embodiment of the transmission unit of the image communication device in the image communication system of the present invention.

FIG. 5 is a functional block diagram of an example of a receiving unit of an image communication device in a conventional image communication system.

[Explanation of symbols]

 12 Video encoder 14 System multiplex encoder 20 Retransmission processor 22, 32 Buffer circuit 30 Data storage decision unit 504 Multiplexed bit string reception buffer circuit 506 System multiplex decoder 508 Coding type detector 510 Standby buffer circuit 512 Selector Circuit 514 Video decoding unit 520 Retransmission request determination unit

Continuation of front page (72) Inventor Toshihisa Nakai 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd. F-term (reference) 5C059 MA04 MA05 PP04 RB16 RF14 RF15 RF23 SS06 UA02 UA05 5C063 AB03 AB07 CA11 DA07 DA13

Claims (8)

[Claims] 1. A transmission unit of an image communication device is connected to a reception unit of an image communication device via a transmission path, the transmission unit sends a moving image to the reception unit, and the reception unit receives a moving image based on the received moving image. In the image communication system that responds to the transmission unit, the transmission unit may sequentially select an intra-frame encoding method or an encoding method other than the encoding method in a frame unit for each frame of the sequentially input moving image. Apply and encode, generate encoding type data indicating the encoding method applied to the encoding,
Encoding means for outputting data including the encoded one-frame encoded data and the generated encoding-type data as one-frame image data; and one-frame image data from a first input port. , Input and store one frame of image data output from the encoding means from a second input port, and read the stored one frame of image data. One of the bit strings of the image data for one frame input from the input port is selected, the bit string of the selected image data is divided into a predetermined length, and an error corresponding to the divided image data is detected. And generates an image packet including the divided image data and the generated encoded data, and controls transmission of the formed image packet. Receiving the image data of one frame stored and read out by the multiplex encoding means according to the image packet just transmitted to the receiving section by the transmission control of the multiplex encoding means. Storage means for storing and storing, when the response sent from the receiving unit is found to be a retransmission request signal, the coding type included in the image data for one frame stored in the storage means; Retransmission processing means for examining the data, reading out one frame of image data stored in the storage means if the data indicates the intra-frame encoding method, and sending the image data to the first input port; The multiplex encoding unit selects the image data when one frame of image data is transmitted from the retransmission processing unit to a first input port, and selects the image packet based on the selected image data. Image communication system characterized by preparative is formed, and retransmits the image packets the form to the receiving unit. 2. The image communication system according to claim 1, wherein the receiving unit receives an image packet transmitted from the multiplex encoding unit and detects the error added to the received image packet. Inspection of the encoded data of the above, if it is determined by the inspection that there is an error in the data of the received image packet, a retransmission request signal is generated as the response, the generated retransmission request signal to the retransmission processing means An image communication system comprising an error detecting means for sending. 3. The image communication system according to claim 1, wherein the encoding system other than the intra-frame encoding system is an inter-frame encoding system and a bidirectional predictive encoding system. Image communication system. 4. A transmission unit of the image communication device is connected to a reception unit of the image communication device via a transmission line, and the transmission unit sends a moving image to the reception unit, and the reception unit receives a moving image based on the received moving image. In the image communication system that responds to the transmission unit, the transmission unit may sequentially select an intra-frame encoding method or an encoding method other than the encoding method in a frame unit for each frame of the sequentially input moving image. Apply and encode, generate encoding type data indicating the encoding method applied to the encoding,
Encoding means for outputting data including the encoded one-frame encoded data and the generated encoding-type data as one-frame image data; and one-frame image data from a first input port. , Input and store one frame of image data output from the encoding means from a second input port, and read the stored one frame of image data. One of the bit strings of the image data for one frame input from the input port is selected, the bit string of the selected image data is divided into a predetermined length, and an error corresponding to the divided image data is detected. And generates an image packet including the divided image data and the generated encoded data, and controls transmission of the formed image packet. Receiving the image data of one frame stored and read out by the multiplex encoding means according to the image packet just transmitted to the receiving section by the transmission control of the multiplex encoding means. Then, it checks the encoding type data included in the received one-frame image data, and outputs the received one-frame image data if the data indicates the intra-frame encoding method. And generating an instruction signal for instructing to store image data of a predetermined value different from the data value of the encoding type indicating at least the intra-frame encoding method unless the intra-frame encoding method is indicated. A data storage judging means for outputting, and when image data for one frame is sent from the data storage judging means, the image data is stored, and an instruction signal is sent. In this case, the storage means for generating and storing the image data of the predetermined value, and one frame stored in the storage means when it is determined that the response sent from the receiving unit is a retransmission request signal. Investigate the encoding type data included in the image data for one frame, and if the data indicates the intra-frame encoding method, read out the image data for one frame stored in the storage means, and Retransmission processing means for transmitting the image data to one input port, wherein the multiplex coding means selects the image data when one frame of image data is transmitted from the retransmission processing means to the first input port. Forming an image packet based on the selected image data, and retransmitting the formed image packet to the receiving unit. 5. A transmission unit of the image communication device is connected to a reception unit of the image communication device via a transmission path, the transmission unit sends a moving image to the reception unit, and the reception unit receives a moving image based on the received moving image. In the image communication system that responds to the transmission unit, the transmission unit may sequentially select an intra-frame encoding method or an encoding method other than the encoding method in a frame unit for each frame of the sequentially input moving image. Apply and encode, generate encoding type data indicating the encoding method applied to the encoding,
Encoding means for outputting data including the encoded one-frame encoded data and the generated encoding-type data as one-frame image data; and one-frame image data from a first input port. , Input and store one frame of image data output from the encoding means from a second input port, and read the stored one frame of image data. One of the bit strings of the image data for one frame input from the input port is selected, the bit string of the selected image data is divided into a predetermined length, and an error corresponding to the divided image data is detected. And generates an image packet including the divided image data and the generated encoded data, and controls transmission of the formed image packet. Receiving the image data of one frame stored and read out by the multiplex encoding means according to the image packet just transmitted to the receiving section by the transmission control of the multiplex encoding means. Then, it checks the encoding type data included in the received one-frame image data, and outputs the received one-frame image data if the data indicates the intra-frame encoding method. A data storage determining means for generating and outputting image data of a predetermined value different from at least a data value of a coding type indicating the intra-frame encoding method unless the data value indicates the intra-frame encoding method; When one frame of image data is sent from the storage determining means, the image data is stored. When image data of a predetermined value is sent, the image data of the predetermined value is stored. A storage unit for storing image data, and a coding type included in one frame of image data stored in the storage unit when the response transmitted from the receiving unit is found to be a retransmission request signal. And retransmission processing means for reading out one frame of image data stored in the storage means and sending it to the first input port if the data indicates the intra-frame encoding method. The multiplex encoding unit, when one frame of image data is transmitted from the retransmission processing unit to the first input port, selects the image data, and converts the image packet based on the selected image data. Forming an image packet and retransmitting the formed image packet to the receiving unit. 6. The image communication system according to claim 4, wherein the predetermined value is “0”. 7. The image communication system according to claim 4, wherein the receiving unit receives the image packet transmitted from the multiplex encoding unit and adds the image packet to the received image packet. The coded data for error detection is inspected, and if it is determined by the inspection that there is an error in the data of the received image packet, a retransmission request signal is generated as the response, and the generated retransmission request is generated. An image communication system comprising: an error detection unit that sends a signal to the retransmission processing unit. 8. The image communication system according to claim 4, wherein the encoding system other than the intra-frame encoding system is an inter-frame encoding system and a bidirectional predictive encoding system. An image communication system, comprising: