JP3957903B2 - Image communication system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image communication system, and in particular, a moving image encoded between a transmission unit of an image communication apparatus and a reception unit of an image communication apparatus to which an error detection / retransmission correction method is applied via a transmission path having a transmission error. The present invention relates to an image communication system suitable for transmitting image data.
[0002]
[Prior art]
The waveform of transmitted information (data) is generally corrupted by Gaussian noise, attenuation distortion, group delay distortion, phase jitter, impulsive noise, and the like while traveling through the data transmission line. This causes a bit error. Therefore, in data transmission, transmitted information may arrive at the receiving side by mistake. For this reason, in data transmission, error control is performed to detect an error in received information and correct it to correct information. For this error control, an error detection retransmission correction method (ARQ: Automatic Repeat Request) is generally used.
[0003]
In this error detection retransmission correction method, the transmission side adds a redundant bit, for example, a CRC (Cyclic Redundancy Check) code to the transmission data and sends it to the reception side. If it is found that there is an error, it is considered that an error has occurred in the transmission system, and a retransmission request signal requesting that the data be discarded and transmitted again is sent to the transmission side. A redundant bit is added to the received transmission data and the data is sent again to the receiving side.
[0004]
A moving image data transmission apparatus that transmits and receives moving image data by applying such an error detection retransmission correction method is disclosed in, for example, Japanese Patent Application Laid-Open No. 8-294123. In this moving image data transmission apparatus, encoding is performed to reduce the amount of image information. For this encoding, intraframe encoding, interframe encoding, and bidirectional predictive encoding are used.
[0005]
When describing these encodings, intra-frame encoding performs encoding only with information in individual frames, and inter-frame encoding blocks only motion from past frames (for example, 16 frames) between consecutive frames. X16 pixels) is extracted and motion vectors are calculated and encoded. Bidirectional predictive encoding from both forward and reverse directions encodes the current frame from both the previous and subsequent frames. To do.
[0006]
Describing the method described in claim 2 of this document, the transmission-side apparatus stores encoded data encoded by one of these encoding methods for each frame (one screen), and this Read the stored encoded data, add the information indicating the encoding type of the frame (encoding type) and the information for error control (redundant bit) to the read encoded data, and send it to the receiving side device. 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 sends a request for retransmission of the intra-frame encoded data to the transmitting side. The transmission side apparatus sends the intra-frame encoded data that received the retransmission request to the reception side apparatus again.
[0007]
That is, the moving picture data transmission apparatus described in this document makes a retransmission request only when an error occurs in intra-frame encoded data.
[0008]
FIG. 5 shows a configuration example of a receiving unit of a conventional receiving apparatus in a system for transmitting and receiving moving image data. The operation of this apparatus will be described.
[0009]
This apparatus has a multiplexed bit string input terminal 502. In this example, the input terminal 502 is used for a video packet and a voice packet that are packetized with a packet length of a predetermined number of bytes from a transmitting apparatus (not shown). A division multiplexed signal is supplied, and this signal is sent to the multiplexed bit string reception buffer circuit 504.
[0010]
In this example, the image packet is multiplexed in the order of the synchronization signal, the identification information indicating that it is an image packet, the image data, and the CRC code. Similarly, the audio packet is also an identification that indicates that it is a synchronization signal and an audio packet. Information, audio data, and CRC code are multiplexed in this order.
[0011]
An image signal of one frame is composed of a plurality of the above-described image packets. In this example, the format of the image signal of one frame includes encoded data of one frame, encoding type of encoded data, frame, and the like. The sequence number (SN) is multiplexed. The multiplexed data is multiplexed at the position of the image data in the image packet.
[0012]
The reception buffer circuit 504 is composed of a storage circuit having a capacity for storing at least the number of bits in the packet length described above. This storage circuit temporarily stores data of image or audio packets that are sequentially transmitted, and this temporary storage. The read data is read out and sent to the system multiplex decoder 506.
[0013]
The system multiplex decoder 506 has an image / sound packet separation circuit, and this separation circuit identifies the above-described identification information for identifying the attribute of image or sound multiplexed in the header portion of the packets sent sequentially. To identify whether it is an image packet or a voice packet, and separates and outputs the image packet and the voice packet. The separated voice packet is output to a signal line (not shown), and the separated image packet is output to the encoding type detection unit 508, the standby buffer circuit 510, and the selector circuit 512.
[0014]
The system multiplex decoder 506 also has a circuit for detecting the above-described sequence number, and the sequence number detected by this circuit is sent to the retransmission request determination unit 320. The system multiplex decoder 506 further has a circuit for checking the CRC code described above, and the data checked 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).
[0015]
The encoding type detection unit 508 detects the encoding type from the separated image packets sent from the system multiplex decoder 506 and sends it to the retransmission request determination unit 520. In this example, in this case, there are three types of detected encoding types: an intra-frame encoding type, an inter-frame encoding type, and a bidirectional predictive encoding type.
[0016]
The standby buffer circuit 510 is composed of a storage circuit having a capacity for storing the number of bits of a plurality of image packets including an image signal for at least one frame, and this storage circuit is the image packet data sent from the system multiplex decoder 506. Is temporarily stored, and the temporarily stored data is read and sent to the selector circuit 512.
[0017]
The selector circuit 512 connects the output of the system multiplex decoder 506 to the input of the video decoding unit 514 based on the control signal sent from the retransmission request determination unit 520, or the output of the standby buffer circuit 510 to the video decoding unit 514. A switching circuit connected to the input.
[0018]
The moving image decoding unit 514 is a circuit that decodes the encoded image data while referring to the encoding type information of each frame sent from the selector circuit 512. The decoded image data is sent to the image signal output terminal 516.
[0019]
As mentioned earlier, retransmission request determination section 520 receives the coding type information from coding type detection section 508 and receives the data resulting from the examination of the sequence number and CRC code from system multiplex decoder 506. To do.
[0020]
Retransmission request determination unit 520 determines that the data obtained as a result of checking the CRC code is data indicating normal reception or data indicating an error, and data indicating an error by this determination circuit. When it is determined, a determination circuit that determines what type of information of the received encoding type is generated, and a retransmission request signal to be transmitted when the determination circuit determines that the information is an intra-frame encoding type In addition, a retransmission signal generation circuit for sending the received sequence number and the generated retransmission request signal to the transmission side device via the retransmission request signal output terminal 518, and control for sending to the selector circuit 512 based on the output signal of these circuits And a control signal generation circuit for generating a signal.
[0021]
That is, in the case of the apparatus shown in FIG. 5 as well, a retransmission request is made together with a sequence number only when an error occurs in intra-frame encoded data.
[0022]
[Problems to be solved by the invention]
As described above, in the method of determining the encoding type in the receiving unit of the apparatus and requesting retransmission, if there is an error in the encoding type information itself, it is not possible to know what encoding type is actually sent. There was a problem. In other words, for example, if the transmitted intra-frame coding type is erroneously changed to the inter-frame coding type, there is a problem that a retransmission request is not issued, and for example, the transmitted intra-frame coding type is erroneously set to the intra-frame coding type. There has been a problem in that a retransmission request is issued when the type is changed.
[0023]
Thus, providing the function of detecting the encoding type in the receiving unit of the apparatus and issuing a retransmission request based on this detection complicates the circuit configuration of the receiving unit and increases the hardware scale. There was a problem to do. This is particularly a problem with a receive-only device.
[0024]
The present invention eliminates the drawbacks of the prior art, simplifies the circuit configuration for detecting a transmission error and making a retransmission request, and reduces the hardware scale, and the apparatus. Provides an image communication system comprising a transmission unit of an image communication apparatus that can reliably retransmit only when the transmitted encoded data is intra-frame encoded data when a retransmission request is received from the receiving unit The purpose is to do.
[0025]
[Means for Solving the Problems]
  The present inventionAccording to the senderThe transmission unit of the image communication device is connected via the transmission path.ReceiverConnected to the receiving unit of the image communication apparatus, the transmitting unit sends a moving image to the receiving unit, and the receiving unit converts the received moving image toaboutSend a response to the transmitterReturnIn the image communication system, the transmission unit sequentiallyArrivalOf moving imagespluralflameFor each ofIntraframe coding method orIs a signApply encoding methods other than encoding methods in a predetermined order,This generates one frame of encoded data,Generate encoding type data indicating the encoding method applied to the encoding,1Encoded data of frameAnd marksEncoding type dataT1 frame of data includingFirstOutput as image dataVideoEncoding means and first input portOn the secondImage datareceived, Second input portFirstImage datareceivedRemember, rememberFirst madeA bit string obtained by reading image data orThe received secondSelect one of the bit strings of the image data,This selected first or secondA bit string of image data is divided into a predetermined length,This divided first or secondGenerate encoded data for error detection corresponding to the image data,This divided first or secondimage dataAnd for error detectionEncoded dataincludingForm an image packet,PictureImage packetSend to the receiverMultiple encoding means;Storage means for storing first image data, or third image data having a predetermined value “0” different from at least one encoding type data value indicating an intra-frame encoding method, and multiple encoding When the first image data used for transmission from the means to the receiving unit is input, the encoding type data included in the input first image data is examined, and the encoding type data is The data storage judging means for storing the first image data in the storage means if it indicates the intra-frame encoding system, or the third image data in the storage means if it does not indicate the intra-frame encoding system, and the receiving unit If it is determined that the returned response is a retransmission request signal, the encoding type data corresponding to the first image data stored in the storage means is examined, and the encoding type data is stored in the frame. And a retransmission processing means for reading the first image data from the storage means and sending it as the second image data to the first input port if it indicates an intra-frame coding system, When the second image data is received from the retransmission processing means at the first input port, the second image data is selected, the selected second image data is formed into an image packet, and the formed image packet is received by the receiving unit. When the reception unit receives the image packet from the multiplex encoding unit, the reception unit inspects the encoded data for error detection included in the received image packet, and the data of the received image packet by this inspection If it is determined that there is an error, a retransmission request signal is generated, and error detection means for sending the generated retransmission request signal to the retransmission processing means as the response is provided.To do.
[0026]
  In this case, the data storage determining means gives an instruction signal for storing the third image data to the storage means when the encoding type data does not indicate the intra-frame encoding method, and the storage means The third image data may be generated and stored in response to the signal. The data storage determining means may generate third image data and store it in the storage means when the data of the encoding type does not indicate the intra-frame encoding method.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the image communication system according to the present invention will be described in detail with reference to the accompanying drawings.
[0028]
FIG. 1 shows functional blocks of a first embodiment of the transmission unit of the image communication apparatus in the image communication system of the present invention. Referring to FIG. 1, the transmission 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. The circuit 22 is configured.
[0029]
When the transmission unit in FIG. 1 receives a retransmission request signal from the reception unit of the image communication apparatus on the receiving side (not shown) at the retransmission request signal input terminal 18, the retransmission processing unit 20 stores one frame stored in the buffer circuit 22. Refers to the encoding type of the encoded data, and if the result of the reference is an intra-frame encoding type, reads the encoded data of one frame stored therein, and sets the system multiplex encoder 14 and the multiplexed bit string output terminal 16 And retransmitting to the receiving unit of the receiving side device.
[0030]
For example, a video (image) signal of a moving image from a television camera (not shown) is input to the image signal input terminal 10. The input of the moving image encoding unit 12 is connected to the image signal input terminal 10 via the signal line 102, and the moving image encoding unit 12 converts the analog image signal input from the input 102 into a corresponding digital image signal, One frame of image signal data is encoded by any one of an intra-frame encoding method, an inter-frame encoding method, and a bidirectional predictive encoding method, and one frame of image signal data including the encoded data is encoded. Is sent to the system multiplex encoder 14 via the signal line 104.
[0031]
Here, the encoded data for each frame sequentially output from the moving image encoding unit 12 will be described. For example, the intra-frame encoding method is applied to one frame of image signal data first input to the encoding unit 12. Then, the intra-frame encoded data is output, the bi-directional predictive encoding method is applied to the next input image signal data of the first frame, and the bi-directional predictive encoded data is output. The order of the output encoding methods may be determined in advance so that the inter-frame encoding method is applied to the image signal data of the first frame and the inter-frame encoding data is output.
[0032]
In addition to the one-frame encoded data described above, the one-frame image signal data sequentially output from the moving image encoder 12 encodes the encoded data generated by the encoder 12. The type, the sequence number of the frame, etc. may be included.
[0033]
In this example, there are three types of encoded data output from the moving image encoding unit 12: an intra-frame encoding scheme, an inter-frame encoding scheme, and a bidirectional predictive encoding scheme. There may be two types, an inner coding scheme and an interframe coding scheme, or several types of coding schemes other than an intraframe coding scheme, an interframe coding scheme, and a bidirectional predictive coding scheme.
[0034]
The system multiplex encoder 14 has a storage circuit for storing image signal data for one frame 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 read signal line 110.
[0035]
In addition, as will be described later, in this storage circuit, the retransmission processing unit 20 may send image signal data for one frame stored in the buffer circuit 22 to the system multiplex encoder 14 via the signal line 106 in response to a retransmission request. In the meantime, it has a capacity to store one frame of image signal data output from the moving image encoding unit 12. As will be described later, this storage circuit also has a capacity for storing one frame of image signal data output from the moving image encoding unit 12 while the voice packet is multiplexed.
[0036]
The system multiplex encoder 14 also has an image packetizing circuit. The image packetizing circuit reads one frame of image signal data read from the storage circuit or one frame of image input from the input 106 in response to a retransmission request. The signal data is divided into a stream having an appropriate bit or byte length to generate an image packet. Specifically, in this image packet, in addition to the above-described divided image signal data, the synchronization signal generated by the image packetizing circuit, the identification information indicating the image packet, the CRC code, and the like are described above. It may be included in the multiplexed position.
[0037]
The system multiplex encoder 14 also has a packet multiplexing circuit, and the packet multiplexing circuit appropriately time-division multiplexes the image packet sent from the image packetizing circuit and the voice packet inputted from a signal line (not shown). Circuit. 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.
[0038]
The system multiplex encoder 14 also has a transmission control circuit, and the transmission control circuit has a circuit for forming a transmission request signal and a transmission end signal, for example. 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 and receives various response signals including retransmission request signals sent from the receiving side device via the input terminal 18 and the signal line 116, and data and control signals sent via the signal line 106. It also has a control function unit that forms a control signal for controlling each unit based on the response signal, data, and control signal.
[0039]
The buffer circuit 22 has a storage circuit having a capacity for storing image signal data for at least one frame input from the input 110. This storage circuit stores image signal data for one frame input from the input 110. 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.
[0040]
As mentioned before, various response signals including a retransmission request signal from a receiving apparatus (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 through a signal line 116, and the retransmission processing unit 20 has a detection circuit that detects a retransmission request signal among the response signals input from the input 116. The retransmission processing unit 20 also receives a signal indicating that the retransmission request signal has been detected from the detection circuit, and generates a read control signal for reading the data stored in the buffer circuit 22 in response to the signal. A signal generation circuit; The read control signal generated by this circuit is sent to the buffer circuit 22 via the control line 112.
[0041]
The image signal data for one frame read from the buffer circuit 22 by the read control signal described above is input to the input 114 of the retransmission processing unit 20. The retransmission processing unit 20 also extracts an encoding type included in one frame of image signal data input from the input 114, and investigates which type of encoding type the extracted encoding type is. As a result of this investigation, if it is an intra-frame coding 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. If the coding type or the bidirectional predictive coding type, a control circuit for forming a signal instructing not to retransmit the signal line 106 is provided.
[0042]
The control circuit of the retransmission processing unit 20 is also provided with a circuit for sending one frame of image signal data read from the buffer circuit 22 again and input from the input 114 to the signal line 106 for the purpose of retransmission. When the control function unit of the system multiplex encoder 14 determines that the signal input via the signal line 106 is image signal data, the control function unit receives one frame input via the signal line 106. A control signal for retransmitting the image signal data is sent to each unit. Thereby, the same one-frame image signal data sent immediately before is divided, packetized, and sent to the receiving apparatus.
[0043]
In addition, when the control function unit of the system multiplex encoder 14 determines that the signal input via the signal line 106 is a signal indicating that the signal is not retransmitted, the control function unit performs the storage circuit of the system multiplex encoder 14. Is instructed to read out image signal data for one frame stored in the memory and waiting to be read out from the storage circuit. The image signal data for one frame read out by this instruction is sent to the image packetizing circuit and the buffer circuit 22 of the system multiplex encoder 14 in the same manner as in the normal operation. Therefore, the sequence number of one frame of image signal data output from the multiplexed bit string output terminal 16 is the number next to the sequence number of one frame of image signal data sent immediately before.
[0044]
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 sequentially applies to the storage circuit of the system multiplex encoder 14 based on the response signal input from the input 116. An instruction to sequentially read out the stored image signal data of one frame is issued.
[0045]
First, the operation of the first embodiment in FIG. 1 will be described using the normal operation sequence in data transmission shown in FIG.
[0046]
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 unit of the receiving apparatus. Upon receiving this, the reception unit sends the transmission response signal to the transmission side device because it is reception 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 and the signal line 116 on the transmission side. The data link between the transmission side device and the reception side device is established by the transmission / reception of the transmission request and the transmission response.
[0047]
When the transmission control circuit of the system multiplex encoder 14 receives the transmission response signal, it transmits 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, the image packetization circuit and the buffer circuit of the system multiplex encoder 14 convert the encoded data for one frame and the image signal data for one frame including the encoding type. Send to 22. Since this first frame cannot use interframe coding or the like, it is intraframe coded data.
[0048]
The buffer circuit 22 stores the received image signal data for one frame. The image packetization circuit divides the received image signal data for one frame into an appropriate bit or byte length stream, generates an image packet with the CRC code added to the divided image signal data, and receives it at the receiving device. Send to department.
[0049]
The receiving unit of the receiving-side apparatus sequentially determines whether or not there is a transmission error in the image signal data for one frame that is finally received by sequentially detecting the presence or absence of transmission errors in the sequentially received image packets. Since the normal operation is performed in the case of FIG. 2, the reception unit of the reception side apparatus determines that the reception result is normal, and transmits a response signal # 1 indicating normal reception based on this determination to the system multiplex coding on the transmission side. To the transmission control circuit of the device 14.
[0050]
As can be seen from the above, in this example, the CRC code is inspected to detect whether there is an error as a function for determining whether or not to send a retransmission request signal to the transmission side in the receiver of the image communication apparatus. All you need is a function to do. 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 prior art.
[0051]
When the transmission control circuit of the system multiplex encoder 14 receives the response signal # 1, it transmits a transmission start signal # 2 to the storage circuit of the system multiplex encoder 14. The operation after the second transmission start signal # 2 is basically the same as the operation performed based on the first transmission start signal # 1.
[0052]
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.
[0053]
The buffer circuit 22 stores the received image signal data including interframe encoded data or bi-directional predictive encoded data for one frame. The image packetizing circuit divides the received image signal data including interframe encoded data or bi-directional predictive encoded data for one frame into an appropriate bit or byte length stream, and converts the divided image signal data into a CRC code. Is added and sent to the receiving apparatus.
[0054]
Next, the operation of the first embodiment in FIG. 1 will be described using the abnormal operation sequence in the data transmission shown in FIG.
[0055]
A data link between the transmission side device and the reception side device is established by exchanging the transmission request and the transmission response. When 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 that has received the transmission start signal # 1 receives the intra-frame encoded data for one frame and the image signal data for one frame including the encoding type for the image packets of the buffer circuit 22 and the system multiplex encoder 14. To the circuit. The buffer circuit 22 stores the sent image signal data for one frame, and the image packetizing circuit divides the sent image signal data for one frame into a stream having an appropriate bit or byte length, and divides it. An image packet with a CRC code added to the image signal data is generated and sent to the receiving unit of the receiving apparatus. Up to this point, the operation sequence is the same as the normal operation sequence shown in FIG.
[0056]
The receiving unit of the receiving-side apparatus sequentially determines whether or not there is a transmission error in the image signal data for one frame that is finally received by sequentially detecting the presence or absence of transmission errors in the sequentially received image packets. In FIG. 3, since the operation is abnormal, the reception unit of the reception side apparatus determines that the reception result is abnormal, and sends a retransmission request signal # 1 that is a response signal indicating abnormal reception based on this determination to the transmission side. To the retransmission processing unit 20 of the system multiplex encoder 14.
[0057]
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. When 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.
[0058]
As a result, 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 the encoding type included in the transmitted image signal data for one frame, investigates the type of the extracted encoding type, and by this investigation, In the case of the intra-frame coding 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. If the inter-frame coding type or the bi-directional predictive coding type other than the intra-frame coding type is determined by this investigation, a signal instructing not to retransmit is sent to the signal line 106.
[0059]
In this case, since the coding type determined by the investigation is the intra-frame coding type, the control circuit of the retransmission processing unit 20 performs system multiplexing of one frame of image signal data read from the buffer circuit 22 via the signal line 106. The data is sent to the transmission control circuit of the encoder 14. Since the signal input via the signal line 106 is image signal data, the transmission control circuit determines that it is retransmission data, and sends a control signal for sending this to each unit. As a result, the same one-frame image signal data sent immediately before is divided, packetized, and sent to the receiving unit of the receiving apparatus.
[0060]
According to the first embodiment, image data for one frame just sent from the transmission unit of the image communication apparatus is stored in the buffer circuit 22 instead. Then, when there is a retransmission request from the receiving unit of the receiving side apparatus for the image signal data for one frame that has just been transmitted, the retransmission processing unit 20 encodes the image signal data for one frame stored in the buffer circuit 22. Investigate type. In this investigation, if it is an intra-frame coding type, the image signal data for one frame stored in the buffer circuit 22 is transmitted, and if it is not the intra-frame coding type, the next transmission is scheduled for one frame. Transmit image signal data. Thus, even if there is a retransmission request by a simple circuit of the receiving unit, there is an effect that the retransmission can be reliably performed only when the transmitted coding type is the intra-frame coding type.
[0061]
FIG. 4 shows functional blocks of a second embodiment of the transmission unit of the image communication apparatus in the image communication system of the present invention. Referring to FIG. 4, the transmission 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, data The storage determination unit 30 and the buffer circuit 32 are included.
[0062]
As can be seen from the above, FIG. 4 differs from FIG. 1 in that a data storage determination unit 30 is added, the buffer circuit 22 in FIG. 1 is changed to a buffer circuit 32 in FIG. In FIG. 1, the storage circuit of the system multiplex encoder 14 is connected to the buffer circuit 22 via the signal line 110. In FIG. 4, the storage circuit of the system multiplex encoder 14 is connected to the data storage judgment unit via the signal line 110. The data storage determining unit 30 is connected to the buffer circuit 32 via the signal line 130. 4, parts corresponding to those in FIG. 1 are denoted by the same reference numerals, and redundant description is omitted.
[0063]
The data storage determination unit 30 determines what is the encoding type of the encoded data in the image signal data for one frame sent from the storage circuit of the system multiplex encoder 14, and this determination determines the intra-frame encoding type. If it is determined that the image signal data for one frame is sent to the buffer circuit 32, and if it is determined not to be the intra-frame encoding type, the storage area of the buffer circuit 32 stores this image signal data. In the example, an instruction signal for instructing to store “0” data is sent to the buffer circuit 32.
[0064]
The buffer circuit 32 is the same as the buffer circuit 22 of FIG. 1 in that it stores image signal data for one frame that has been sent. The difference from the buffer circuit 22 of FIG. 1 is the case where the above-described instruction signal is sent. In this case, the function of storing “0” data in the storage area of the storage circuit of the buffer circuit 32 in this example. It is having. That is, it has a delete function.
[0065]
That is, the image signal data for one frame is stored in the buffer circuit 32 only for the intra-frame encoding type just transmitted from the transmission unit of the image communication apparatus, and “0” is stored for other than the next intra-frame encoding type. The reason for storing the data in the buffer circuit 32 is to reliably retransmit the image signal data for one frame of the intra-frame coding type when a retransmission request is received from the receiving unit of the receiving side apparatus.
[0066]
Specifically, when image signal data for one frame type other than the intra-frame coding type is transmitted from the transmission unit of the image communication apparatus, the data in the storage circuit of the buffer circuit 32 is not set to “0”. Until the next intra-frame coding type arrives, the data of the previous intra-frame coding type remains stored in the storage circuit of the buffer circuit 32. In this state, the data just sent from the transmission unit of the image communication apparatus is data other than the intra-frame coding type. At this time, if there is a retransmission request from the reception unit of the reception side apparatus, The intra-frame coding type data stored in the storage circuit is retransmitted. That is, the data is set to “0” to avoid such retransmission.
[0067]
In this example, when the data storage determining unit 30 determines that it is not the intra-frame encoding type, an instruction signal is sent to instruct the buffer circuit 32 to store “0” data. A method of sending “0” data to the buffer circuit 32 when the determination unit 30 determines that it is not the intra-frame encoding type. Also, in this case, after determining that it is the intra-frame coding type, if it is determined that it is not the first intra-frame coding type, data “0” is sent, and then the intra-frame coding type. Until the determination is made, a method in which data of “0” is not transmitted even if it is determined that the type is not the intra-frame encoding type may be used. In these systems, the function of the buffer circuit 32 may be the same as the function of the buffer circuit 22 of FIG.
[0068]
In this example, the instruction signal is sent every time when it is determined that it is not the intra-frame coding type, but it is determined that it is not the first intra-frame coding type after it is determined that it is the intra-frame coding type. In such a case, an instruction signal may be sent, and after that, until it is determined that it is an intra-frame coding type, even if it is determined that it is not an intra-frame coding type, a system that does not send an instruction signal may be used. In this example, the data to be stored is “0” data. However, any data may be used as long as it can be distinguished from intra-frame coding type data.
[0069]
First, the operation of the second embodiment in FIG. 4 will be described using the normal operation sequence in the data transmission shown in FIG.
[0070]
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 unit of the receiving apparatus. Upon receiving this, the reception unit sends the transmission response signal to the transmission side device because it is reception 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 and the signal line 116 on the transmission side. The data link between the transmission side device and the reception side device is established by the transmission / reception of the transmission request and the transmission response.
[0071]
When the transmission control circuit of the system multiplex encoder 14 receives the transmission response signal, it transmits 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, the image packetization circuit of the system multiplex encoder 14 and the data storage store the encoded data for one frame and the image signal data for one frame including the encoding type. Send to decision unit 30. Since this first frame cannot use interframe coding or the like, it is intraframe coded data.
[0072]
The data storage determination unit 30 determines what is the encoding type of the encoded data in the transmitted image signal data for one frame. In this case, since the determination result is the intra-frame coding type, the transmitted image signal data for one frame is sent to the buffer circuit 32.
[0073]
The buffer circuit 32 stores the received image signal data for one frame. The image packetization circuit divides the received image signal data for one frame into an appropriate bit or byte length stream, generates an image packet with the CRC code added to the divided image signal data, and receives it at the receiving device. Send to department.
[0074]
The receiving unit of the receiving-side apparatus sequentially determines whether or not there is a transmission error in the image signal data for one frame that is finally received by sequentially detecting the presence or absence of transmission errors in the sequentially received image packets. Since the normal operation is performed in the case of FIG. 2, the reception unit of the reception side apparatus determines that the reception result is normal, and transmits a response signal # 1 indicating normal reception based on this determination to the system multiplex coding on the transmission side. To the transmission control circuit of the device 14.
[0075]
When the transmission control circuit of the system multiplex encoder 14 receives the response signal # 1, it transmits a transmission start signal # 2 to the storage circuit of the system multiplex encoder 14. The storage circuit sends the encoded data for one frame and the image signal data for one frame including the encoding type 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.
[0076]
The data storage determination unit 30 determines what is the encoding type of the encoded data in the transmitted image signal data for one frame. In this case, since the determination result is not the intra-frame coding type, an instruction signal for instructing to store “0” data in the storage area of the storage circuit of the buffer circuit 32 is sent to the buffer circuit 32.
[0077]
In this example, the buffer circuit 32 stores “0” data in the storage area of the storage circuit. The image packetizing circuit divides the received image signal data including interframe encoded data or bi-directional predictive encoded data for one frame into an appropriate bit or byte length stream, and converts the divided image signal data into a CRC code. Is added and sent to the receiving apparatus.
[0078]
Next, the operation of the second embodiment in FIG. 4 will be described using the abnormal operation sequence in data transmission shown in FIG.
[0079]
A data link between the transmission side device and the reception side device is established by exchanging the transmission request and the transmission response. When 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 that has received the transmission start signal # 1 receives the intraframe encoded data for one frame and the image signal data for one frame including the encoding type of the data storage determination unit 30 and the system multiplex encoder 14. Send to image packetization circuit.
[0080]
The data storage determining unit 30 determines what is the encoding type of the encoded data in the transmitted image signal data for one frame. In this case, since the determination result is the intra-frame coding type, the transmitted image signal data for one frame is sent to the buffer circuit 32. The buffer circuit 32 stores the received image signal data for one frame. The image packetization circuit divides the received image signal data for one frame into an appropriate bit or byte length stream, generates an image packet with the CRC code added to the divided image signal data, and receives it at the receiving device. Send to department. The process up to this point is the same as the normal operation sequence.
[0081]
The receiving unit of the receiving-side apparatus sequentially determines whether or not there is a transmission error in the image signal data for one frame that is finally received by sequentially detecting the presence or absence of transmission errors in the sequentially received image packets. In FIG. 3, since the operation is abnormal, the reception unit of the reception side apparatus determines that the reception result is abnormal, and sends a retransmission request signal # 1 that is a response signal indicating abnormal reception based on this determination to the transmission side. To the retransmission processing unit 20 of the system multiplex encoder 14.
[0082]
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 32.
[0083]
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 the encoding type included in the transmitted image signal data for one frame, investigates the type of the extracted encoding type, and by this investigation, In the case of the intra-frame coding 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. If the inter-frame coding type or the bi-directional predictive coding type other than the intra-frame coding type is determined by this investigation, a signal instructing not to retransmit is sent to the signal line 106.
[0084]
In this case, since the coding type determined by the investigation is the intra-frame coding type, the control circuit of the retransmission processing unit 20 performs system multiplexing of the image signal data of one frame read from the buffer circuit 32 via the signal line 106. The data is sent to the transmission control circuit of the encoder 14. Since the signal input via the signal line 106 is image signal data, the transmission control circuit determines that it is retransmission data, and sends a control signal for sending this to each unit. As a result, the same one-frame image signal data sent immediately before is divided, packetized, and sent to the receiving unit of the receiving apparatus.
[0085]
According to the second embodiment, if the data just sent from the transmission unit of the image communication apparatus is data of the intra-frame coding type, the image signal data for one frame is stored in the buffer circuit 32. If not, data “0” is stored. Then, when there is a retransmission request from the receiving unit of the receiving side apparatus for the image signal data for one frame that has just been transmitted, the retransmission processing unit 20 encodes the image signal data for one frame stored in the buffer circuit 32. Investigate type. In this investigation, if it is an intra-frame coding type, the image signal data for one frame stored in the buffer circuit 32 is transmitted, and if it is not the intra-frame coding type, the next one frame is scheduled to be transmitted. Transmit image signal data. Thus, even if there is a retransmission request by a simple circuit of the receiving unit, there is an effect that the retransmission can be reliably performed only when the transmitted coding type is the intra-frame coding type.
[0086]
Note that these embodiments are image communication systems that send moving images in one direction. However, an image communication apparatus including a transmitting unit and a receiving unit according to the present invention is installed between two points, for example. May be an image communication system.
[0087]
【The invention's effect】
As described above, according to the present invention, in the transmission unit, the storage unit is stored and read out by the multiple encoding unit corresponding to the image packet just transmitted to the reception unit by the transmission control of the multiple encoding unit. When one frame of image data is received and stored, and the retransmission processing means knows that the response sent from the receiving section is a retransmission request signal, it will be included in the image data for one frame stored in the storage means. If the data of the included encoding type is examined and this data indicates an intra-frame encoding method, the image data for one frame stored in the storage means is read out and sent to the first input port. When the image data for one frame is sent from the retransmission processing means to the first input port, the converting means selects the image data, forms an image packet based on the selected image data, It retransmits the image packets to the receiving unit. In this way, when there is a retransmission request, the transmission unit can effectively retransmit only when the encoding type of the image data just sent is the intraframe encoding method.
[0088]
As described above, according to the present invention, in the transmission unit, the data storage determination unit stores and reads the data storage determination unit stored in the multiplex encoding unit corresponding to the image packet just transmitted to the reception unit by the transmission control of the multiplex encoding unit. Receives the output image data for one frame, checks the encoding type data included in the received image data for one frame, and receives this data if it indicates an intra-frame encoding method Instruct to store at least a predetermined value of image data different from the encoding type data value indicating the intra-frame coding method unless the intra-frame encoding method is indicated. When the image data for one frame is sent from the data storage judgment means, the storage means records the image data. When the instruction signal is sent, the image data of a predetermined value is generated and stored, and the retransmission processing means knows that the response sent from the receiving section is a retransmission request signal. If the data of the encoding type included in the image data for one frame stored in is checked and this data indicates the intra-frame encoding method, the image data for one frame stored in the storage means Is sent to the first input port, and the multiplex encoding means selects the 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. Based on this, an image packet 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 that has just been transmitted is the intraframe encoding method.
[0089]
As described above, according to the present invention, in the transmission unit, the data storage determination unit stores and reads the data storage determination unit stored in the multiplex encoding unit corresponding to the image packet just transmitted to the reception unit by the transmission control of the multiplex encoding unit. Receives the output image data for one frame, checks the encoding type data included in the received image data for one frame, and receives this data if it indicates an intra-frame encoding method 1 frame of image data is output, and if it does not indicate an intra-frame encoding method, at least image data having a predetermined value different from the encoding type data value indicating the intra-frame encoding method is generated and output The storage means stores the image data when one frame of image data is sent from the data storage judging means, and the image data of a predetermined value is sent. The image data of this predetermined value is stored, and when the retransmission processing means knows that the response sent from the receiving section is a retransmission request signal, the image data for one frame stored in the storage means If the data of the coding type included in the data indicates the intra-frame coding method, the image data for one frame stored in the storage means is read and sent to the first input port. The multiplex encoding means selects the image data when one frame of image data is sent from the retransmission processing means to the first input port, forms an image packet based on the selected image data, and forms the formed image. Retransmit the packet to the receiver. 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 sent is the intraframe encoding method.
[0090]
As described above, according to the present invention, the receiving unit for the transmitting unit described above receives the image packet transmitted from the multiplex coding unit, and encodes for error detection added to the received image packet. When the data is inspected, and when it is determined that there is an error in the data of the image packet received by this inspection, a retransmission request signal is generated as a response, and the generated retransmission request signal is sent to the retransmission processing means. . As described above, since the function of the error detection means is less than that of the conventional error detection 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 apparatus in an image communication system of the present invention.
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 illustrating an example of an abnormal operation sequence of the embodiment in FIGS. 1 and 4. FIG.
FIG. 4 is a functional block diagram of a second embodiment of the transmission unit of the image communication apparatus in the image communication system of the present invention.
FIG. 5 is a functional block diagram illustrating an example of a receiving unit of an image communication apparatus in a conventional image communication system.
[Explanation of symbols]
12 Video encoding unit
14 system multiplex encoder
20 Retransmission processing part
22, 32 Buffer circuit
30 Data storage decision section
504 Multiplexed bit string reception buffer circuit
506 System Multiplexer
508 Encoding type detector
510 Standby buffer circuit
512 selector circuit
514 Video decoding unit
520 Retransmission request decision section

Claims (5)

Transmission of the transmission-side image communication apparatus is connected to the receiving portion of the receiving image communication apparatus via the transmission path, the transmission unit sends the video image to the receiving unit, the receiving unit is attached to the moving image received the In the image communication system that returns a response to the transmission unit,
The transmitter is
For each of a plurality of frames of a moving image that arrives sequentially, encoding is performed by applying an intra-frame encoding scheme or an encoding scheme other than the encoding scheme in a predetermined order, thereby generating encoded data of one frame. generates a coding type data indicating an encoding method applied to the coding, the first image data for one frame data including the encoded data and the encoded type of data of the one frame Moving image encoding means for outputting as
The second image data is received at the first input port , the first image data is received and stored at the second input port, and the stored first image data is read out or received. 2 selects one of the bit strings of the image data, divides the selected bit string of the first or second image data into a predetermined length, and corresponds to the divided first or second image data error encoding data to generate for detection, an image packet formed including the encoded data for the detection Ri first or second image data and said error that is the split, the receive 該画 image packets Multiplex encoding means for transmitting to the unit,
Storage means for storing first image data or third image data having a predetermined value “0” different from at least one encoding type data value indicating an intra-frame encoding method, for one frame;
Wherein the first image data subjected from the multiplexing encoding means for transmission to the receiving unit is input, to investigate the data of the encoding type included in the first image data that has been said input, said code the type of data is the first image data as long as it exhibits an intraframe coding method, and the data storage of Ru stores the third image data if indicates the intraframe coding scheme in said storage means Judgment means,
Knowing the bounced the response from the receiving unit is a retransmission request signal, it examines the data of the encoding type corresponding to the first image data stored in the storage means, the encoding type data And a retransmission processing means for reading out the first image data from the storage means and sending the first image data to the first input port as second image data .
When receiving the second image data from the retransmission processing unit at the first input port, the multiplex encoding unit selects the second image data , and forms the selected second image data in the image packet. , Resend the formed image packet to the receiver ,
When the reception unit receives an image packet from the multiplex encoding unit, the reception unit inspects the encoded data for error detection included in the received image packet, and an error is detected in the data of the received image packet. If it is determined that there is, the image communication system, characterized in that the retransmission generates a request signal, to have a error detection unit for sending the retransmission processing means retransmits the request signal thus generated as the response. 2. The image communication system according to claim 1, wherein the data storage determining means stores an instruction signal for storing third image data when the encoding type data does not indicate an intra-frame encoding method. To the means,
The image communication system , wherein the storage means generates and stores third image data in response to the instruction signal . 2. The image communication system according to claim 1 , wherein the data storage determining unit generates third image data and stores it in the storage unit when the encoding type data does not indicate an intra-frame encoding method. An image communication system characterized by storing . The image communication system according to claim 1 , wherein the encoding method other than the intra-frame encoding method is at least one of an inter-frame encoding method and a bidirectional predictive encoding method. Communications system. 2. The image communication system according to claim 1, wherein when the retransmission processing means determines that the data of the encoding type for the retransmission request signal indicates an encoding scheme other than an intra-frame encoding scheme, the multiplex code It means an image communication system according to claim you to select the second input port.

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