JPH09116904A - Data communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the technology capable of communicating image data without deteriorating a communication throughput. SOLUTION: In the case of transmission of an image subjected to digital compression coding by using a bidirectional communication system having a communication line error in the data communication system for image communication, a transmitter 100 sends compressed image data with a block length when an original image is divided into plural blocks. A receiver 200 decodes the compression image data and checks whether or not the block length of the decoded image data is coincident with the transmitted block length and when anticoincident, an identification number of a frame including the block is specified and the specified frame is requested for re-transmission.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data communication system for transmitting a digitally encoded image by using a bidirectional communication system, and more particularly, based on block synchronization information without using an error detection code. The present invention relates to a technique for detecting an error in each block in an image decoder.

[0002]

2. Description of the Related Art FIG. 7 shows an ARQ (Automatic Request f) used in a conventional data communication system.
FIG. 2 is a block configuration diagram for specifically explaining an or repeat transmission device, in which a transmission side includes an image encoding unit 1, a frame configuration unit 2, and a transmission buffer 3, and a reception side includes a communication path error detection unit 4 and a reception unit. It comprises a buffer 6 and an image decoding means 7.

Further, the transmitting side and the receiving side are connected by a bidirectional communication path (not shown) which enables bidirectional communication, and this bidirectional communication path may cause a transmission error during signal transmission. There is.

When transmitting an image from the transmitting side to the receiving side,
First, an original image, which is information to be transmitted, is divided into a plurality of blocks by the image encoding means 1, then compressed and encoded into compressed image data.

Next, the frame construction means 2 divides the compressed image data into frames of a fixed length, calculates an error detection code for each divided frame, and adds the calculated error detection code to the corresponding frame. .

Next, the frame constructing means 2 sequentially adds numbers to the frames to which the error detection code has been added, transfers the frames to the transmission buffer 3 in order, and stores them in the transmission buffer 3.

The transmission buffer 3 sequentially outputs the compressed image data accumulated for each frame to a bidirectional communication path (not shown) unless a retransmission request from the receiving side is received.

The operation when there is a retransmission request from the receiving side will be described later.

On the other hand, on the receiving side, the communication path error detecting means 4 first detects the communication path error in frame units with respect to the compressed image data received from the bidirectional communication path (not shown), and no error is detected. In this case, as a notification for confirming the reception of the frame, a reception confirmation signal is sent to the transmission side, and the received compressed image data is stored in the reception buffer 6 with a fixed number for each fixed length.

At this time, the transmission side, which has received the reception confirmation signal transmitted from the reception side, discards the corresponding frame in the transmission buffer 3 and secures an empty area for accumulating a new frame.

On the receiving side, when the compressed image data having a length that can be decoded by the image decoding means 7 is accumulated, the reception buffer 6 outputs the compressed image data to the image decoding means 7,
The image decoding means 7 decodes (decompresses) the compressed image data.
And output the reproduced image to a display device (not shown),
The compressed image data accumulated in the reception buffer 6 is discarded and reserved as an empty area for accumulating new data.

On the other hand, when the communication path error detecting means 4 detects an error in the received frame, the number added to the frame is sent to the transmitting side as a retransmission request signal.

On the other hand, the transmitting side, which is requested by the receiving side to resend, does not send the frame corresponding to the resending requested number again, instead of sending the new compressed image data to the bidirectional communication path (not shown). Send to the bidirectional communication path.

AR of the above-mentioned conventional data communication system
By using the Q device, it is possible to retransmit the frame using the error detection code and improve the error due to the bidirectional communication path (not shown), so that an image without image quality deterioration can be obtained.

[0015]

SUMMARY OF THE INVENTION As a result of studying the above prior art, the present inventor has found the following problems.

In a conventional data communication system using an ARQ device, compressed image data, which is original data and divided into frames, is added with an error detection code for detecting an error in a bidirectional communication path and received. To send to the side
There is a problem that the amount of compressed image data that can be transmitted in one frame is reduced by the number of bits required to transmit the error detection code, and the communication throughput is reduced.

An object of the present invention is to provide a technique capable of communicating image data without reducing the communication throughput.

The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

[0019]

SUMMARY OF THE INVENTION Among the inventions disclosed in the present application, the outline of a representative one will be briefly described.
It is as follows.

(1) When a digitally compressed and encoded image is transmitted using a bidirectional communication system in which a communication path error occurs, when an error exists in the received data, the error is detected on the receiving side. In a data communication system that requests the transmission side to retransmit data in which an error has been detected, the transmission side divides the original image into a plurality of blocks, binary-codes the number of bits of each block, and An image encoding unit that outputs the block length data in which the bit information of each block is placed and the compressed image data compressed and encoded for each block, the block length data and the compressed image data, arranged in the order of appearance. Is divided into a predetermined number of bits to form a plurality of frames each having a unique identification number. And a reception buffer that stores the transmission frame data, the reception side receiving the transmission frame data input from a communication path and accumulating the reception frame as reception data, and the reception buffer. The received data accumulated in the buffer is divided into the block length data and the compressed image data, the compressed image data is decoded into reproduced image data and reproduced as an image, and the end of the block of the compressed image data is detected. Then, it is determined whether or not the number of bits from the end of the immediately preceding block to the end of the decoded block matches the number of bits of the block recorded in the block length data. It is assumed that an error has occurred in the image decoding means for identifying the block number and the number specified by the image decoding means. And a retransmission frame determining means for transmitting the retransmission request signal including the identification number of the identified frame to the transmitting side, and the retransmission from the receiving side. When the request signal is transmitted to the transmission side, the transmission buffer determines retransmission data of the frame to be retransmitted based on the retransmission request signal, transmits the retransmission data to the reception side, and retransmits the transmission frame. On the receiving side receiving the data, the reception buffer allocates the retransmitted frame data retransmitted to a specified identification number to update the received data, and the image decoding means updates the received data updated. The image is reproduced based on the original.

(2) When a digital compression coded image is transmitted using a bidirectional communication system in which a communication path error occurs, when an error exists in the received data, the error is detected on the receiving side. In a data communication system that requests the transmission side to retransmit data in which an error has been detected, the transmission side divides the original image into a plurality of blocks, binary-codes the number of bits of each block, and An image encoding unit that outputs the block length data in which the bit information of each block is placed and the compressed image data compressed and encoded for each block, the block length data and the compressed image data, arranged in the order of appearance. Is divided into a predetermined number of bits to form a plurality of frames each having a unique identification number. And a reception buffer that stores the transmission frame data, the reception side receiving the transmission frame data input from a communication path and accumulating the reception frame as reception data, and the reception buffer. The received data accumulated in the buffer is divided into the block length data and the compressed image data, the compressed image data is decoded into reproduced image data and reproduced as an image, and the end of the block of the compressed image data is detected. Then, it is determined whether or not the number of bits from the end of the immediately preceding block to the end of the decoded block matches the number of bits of the block recorded in the block length data. Assuming that an error has occurred, the image decoding means for identifying the block number and the output signal of the image decoding means are used. The presence or absence of the image distortion of the block is checked, and when the image distortion is detected, the image distortion detecting unit that identifies the number of the corresponding block, and the number of the block in which the error input from the image decoding unit is detected It is checked whether or not the number of the block in which the image distortion is detected by the image distortion detection unit matches, and if the numbers match, the identification numbers of all the frames including the block are specified. A retransmission frame detecting means for transmitting to the transmitting side a retransmission request signal for requesting retransmission of the specified frame, and when the retransmission request signal is transmitted from the receiving side to the transmitting side, The transmission buffer determines retransmission data of the frame to be retransmitted based on the retransmission request signal, transmits the retransmission data to the receiving side, and receives the retransmitted transmission frame data. On the receiving side, the receiving buffer assigns the retransmitted frame data retransmitted to a specified identification number to update the received data, and the image decoding means is based on the updated received data. Play the image.

According to the above-mentioned means (1), when the image decoding means on the receiving side decodes the compressed image data, the block length data transmitted together with the compressed image data and the compressed image data are decoded. It is checked whether or not the block length of the obtained reproduced image data matches, and only when they match, it is determined that the compressed image data has been normally transmitted, and the reproduced image data is output to the display means and displayed. If they do not match, the transmitting side transmits the compressed image data of the corresponding block again, and the retransmitted compressed image data (retransmission data) is updated to the data of the non-matching block, and the reproduced image is obtained. By outputting and displaying the data on the display means, it is not necessary to transmit data such as an error detection code, which is data unrelated to the image information of the original image, to the receiving side. It is possible to improve the throughput for transmitting.

According to the above-mentioned means (2), when the image decoding means on the receiving side decodes the compressed image data, the block length data transmitted together with the compressed image data and the compressed image data are decoded. In addition to checking whether or not the block length of the obtained reproduced image data matches, the image distortion detecting means checks the presence or absence of distortion of the reproduced image for each block, and the block length mismatch and the image distortion are detected in the same block. Only when the compressed image data of the corresponding block is transmitted again from the transmitting side, and the retransmitted compressed image data (retransmission data) is replaced with the data of the block in which the block length mismatch and the image distortion are detected. When the reproduced image data obtained is output to the display means and only one of the block length mismatch and the image distortion is detected, By outputting the reproduced image data to the display means and displaying it in the block assuming that the communication path error has not occurred, the data error that does not affect the image quality of the reproduced image on the communication path, and other causes It is difficult to be visually sensed because it has little influence on the reproduced image quality generated in step 1, that is, in the case of distortion that is not detected by the image distortion detection means, retransmission is not performed, and thus the throughput for transmitting image information can be improved. .

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings together with embodiments (examples) of the invention.

In all the drawings for describing the embodiments of the present invention, components having the same functions are denoted by the same reference numerals, and their repeated description will be omitted.

(Embodiment 1) FIG. 1 is a block diagram showing a schematic configuration of a data communication system according to Embodiment 1 of the present invention, in which 1 is an image coding means, 2 is a frame construction means,
Reference numeral 3 is a transmission buffer, 5 is a retransmission frame determination means, 6 is a reception buffer, and 7 is an image decoding means.

The transmitter 100 comprises an image coding means 1, a frame construction means 2 and a transmission buffer 3.
On the other hand, the receiver 200 is composed of a retransmission frame determination means 5, a reception buffer 6, and an image decoding means 7.

In addition, the transmitter 100 and the receiver 200 are capable of bidirectional communication (not shown) bidirectional communication path (communication path).
This bidirectional communication path may cause a transmission error during signal transmission.

In FIG. 1, the image encoding means 1 uses a well-known technique. When the original image is input to the transmitter 100, the image encoding means 1 first divides the original image into a plurality of blocks. Then, the original image divided into a plurality of blocks is compressed according to a compression format predetermined for each block.

At the same time, the image coding means 1 calculates the block length, which is the bit length of each block, and adds the data indicating the block length before the compressed image data of the corresponding block.

The frame forming means 2 is the image encoding means 1.
After the compressed image data to which the data indicating the block length is added is divided into frames having a predetermined bit length, the identification number is, for example, 1 in the order of each frame.
Numbers are given in order from.

The transmission buffer 3 receives a reception confirmation signal transmitted from the receiver 200, or receives an operator's data transfer instruction input from an input means (not shown) to store a frame as transmission data (transmission frame data). Output.

Further, when the retransmission request signal indicating the retransmission request is received from the receiver 200, the transmission buffer 3 does not transmit the next frame (new compressed image data) to the bidirectional communication path (not shown), but transmits the retransmission request. The frame of the identification number included in the signal is transmitted again.

The reception buffer 6 stores the block length data to which the identification number is added and the compressed image data received from the bidirectional communication path (not shown) for each predetermined length, and also the compressed image data for one image is stored. It is a well-known receiving buffer that outputs the accumulated block length data and the compressed image data to the image decoding means 7 at the time point.

The image decoding means 7 first extracts the block length data from the block length data and the compressed image data output from the reception buffer 6, and then decodes (decompresses) the compressed image data to obtain a plurality of data. Convert to an image (image data) consisting of blocks.

At this time, it is checked whether or not the block length of the decoded block and the block length described in the block length data match, and if they match, it is determined that a communication path error has not occurred and decoding is performed. The reproduced image is restored from the block to be output as a good received image to the image decoding means 7, that is, the output means (not shown) from the receiver 200, and a signal indicating that the data is normally received is received by the receiving buffer 6. By discarding the compressed image data accumulated in the receiving buffer 6 by sending and the block length data indicating the block length of this compressed image data, an empty area for accumulating new data is secured in the receiving buffer 6. To do.

On the other hand, when the block length at the time of image decoding and the block length described in the block length data do not match, a block which does not match has a communication path error in the bidirectional communication path (not shown). Assuming that the block has occurred, the block number is checked and output to the retransmission frame determination means 5.

Details of the method for detecting an error in the reproduced image will be described later.

The retransmitted frame determining means 5 specifies the identification number of the frame forming the block in which the error is detected, based on the block number, the block length and the frame length output from the image decoding means 7, and The retransmission request signal including the identification number is output to a bidirectional communication path (not shown), that is, the retransmission request signal is transmitted to the transmitter 100.

FIG. 2 is a diagram for explaining a block configuration when an original image is divided into a plurality of blocks, (a)
Shows the case where the original image is divided into four, (b) shows the case where the original image is divided into eight, and (c) shows the case where the original image is divided into sixteen.

The number of bits of each block when divided as shown in FIGS. 2 (a) to 2 (c) is binary coded, and each block is, for example, (block 1, block 2, block 3, ...). The block length data is arranged in the order of appearance of the blocks and carries bit information for each block.

The order of the blocks shown in FIG. 2 is an example, and it goes without saying that the order is not limited to this.

FIG. 3 is a diagram for explaining a schematic configuration of blocks and frames according to the first embodiment. FIG. 3A shows block length data and compressed image data compression-coded for each block. (B) shows a frame (transmission frame) to which an identification number is given after dividing the block length data shown in (a) and the compressed image data for each block into a predetermined size. Transmission is performed frame by frame.

Therefore, for example, when a transmission error occurs in the block 1 indicated by hatching in (a), that is, when the retransmission request of the block 1 is in the transmitter 100,
As shown in (b), since the block 1 is divided into the frames having the identification numbers 2 to 4, the identification numbers 2 to 2 are transmitted at the time of retransmission.
Three frames including 4 are the target of the retransmitted frame.

Next, the operation of ARQ of the data communication system according to the first embodiment will be described with reference to FIGS. 1 to 3 by the image coding means 1 in which a plurality of original images, which are information to be transmitted by the transmitter 100, are transmitted. While being divided into blocks, the block length, which is the number of bits of the block, is calculated and added before the compressed image data.

Next, the original image divided into blocks is compressed into image data by the image coding means 1 into blocks, and then the receiver 200 identifies the transmitted frame. An identification number is given and accumulated in the transmission buffer 3.

The transmission buffer 3 sequentially transmits the compressed image data divided into frames to a bidirectional communication path (not shown) unless a retransmission request from the receiver 200 is received.

On the other hand, in the receiver 200, the block length data to which the identification number is received and the compressed image data received from the two-way communication path (not shown) have a constant length (first embodiment).
In (1 frame), the data is accumulated in the reception buffer 6.

When the compressed image data for one image is accumulated in the receive buffer 6, the receive buffer 6 outputs the accumulated block length data and the compressed image data to the image decoding means 7.

The image decoding means 7, which has received the block length data and the compressed image data from the reception buffer 6, reproduces the image from the compressed image data, and at the same time, the block length at the time of image decoding is the block transmitted from the transmitter 100. Check if it matches the long data.

If the block lengths match, it is assumed that no communication path error has occurred, and the reproduced image is output from the receiver 200 as a good received image, and at the same time the compressed image stored in the receive buffer 6 is stored. The data is discarded and secured as an empty area for accumulating new data, and a reception confirmation signal is transmitted to the transmitter 100 to wait for reception of new compressed image data.

Further, the transmitter 1 which has received the reception confirmation signal
At 00, the corresponding frame in the transmission buffer 3 is discarded and reserved as a free area for accumulating a new frame.

On the other hand, if the block lengths do not match, it is determined that a communication path error has occurred in the blocks that do not match, and the number of the block is transmitted to the retransmission frame determining means 5 to retransmit the frame. The determining means 5 identifies the identification number of the frame including the block in which the error is detected, and transmits the identified identification number to the transmitter 100 as a retransmission request signal.

In the transmitter 100 which has received the retransmission request signal, instead of transmitting the new compressed image data to the bidirectional communication path (not shown), the frame in the transmission buffer 3 designated by the number included in the retransmission request signal is transmitted. Is transmitted to a two-way communication path (not shown).

In the receiver 200 which has received the transmission frame data (retransmission frame data, retransmission data) including the retransmitted compressed image data, the contents of the reception buffer 6 are updated with the frame retransmitted from the transmitter 100, When the received frames for one image are collected, the image decoding means 7 is again used.
If you play the image with and the block lengths do not match,
The reception process of transmitting the transmission request to the transmitter 100 is repeated until there is no block length mismatch.

As described above, according to the data communication system of the first embodiment, the block length transmitted together with the compressed image data when the image decoding means 7 of the receiver 200 decodes the compressed image data. The image decoding means 7 checks whether or not the data and the block length of the reproduced image data obtained by decoding the compressed image data match, and if they match, the compressed image data is normally transmitted. It is determined that the data is reproduced and the reproduced image data is output to a display unit (not shown) for display.
To transmit a frame containing the compressed image data of the corresponding block, and update the data by replacing the retransmitted retransmission data with the data of the block that does not match,
The reproduced image data thus obtained is output to a display unit (not shown) for display, whereby data such as an error detection code, which is data unrelated to the image information of the original image, is received by the receiver 200.
Since it is not necessary to transmit the image information, it is possible to improve the throughput for transmitting the image information.

(Second Embodiment) FIG. 4 is a block diagram showing a schematic configuration of a data communication system according to a second embodiment of the present invention, and 8 shows an image distortion detecting means.

In FIG. 4, the image distortion detecting means 8 is
This is a means for detecting distortion due to a transmission error that appears in a reproduced image due to a bidirectional communication path (not shown), and detects the image distortion for each block.

The detailed operation of the image distortion detecting means 8 will be described later.

The transmitter 100 and the receiver 200 are connected by a bidirectional communication path (not shown).

Next, the operation of the data communication system according to the second embodiment of the present invention will be described with reference to FIG. While being divided into blocks, the block length, which is the number of bits of the block, is calculated and added before the compressed image data.

Next, the original image divided for each block is compressed for each block by the image encoding means 1 into compressed image data, and the receiver 200 identifies the transmitted frame. An identification number is given and accumulated in the transmission buffer 3.

The transmission buffer 3 sequentially transmits the compressed image data divided into frames to a bidirectional communication path (not shown) unless a retransmission request is received from the receiver 200.

On the other hand, in the receiver 200, the block length data to which the identification number is received and the compressed image data received from the two-way communication path (not shown) have a constant length (first embodiment).
In (1 frame), the data is accumulated in the reception buffer 6.

At the time when one image of compressed image data is stored in the reception buffer 6, the reception buffer 6 outputs the stored block length data and compressed image data to the image decoding means 7.

The image decoding means 7, which has received the block length data and the compressed image data from the reception buffer 6, reproduces the image from the compressed image data and outputs it to the image distortion detecting means 8 and also the block length at the time of image decoding. Is the transmitter 10
It is checked whether it matches the block length data transmitted from 0.

The image distortion detecting means 8 which has received the reproduced image checks the presence or absence of distortion of the reproduced image for each block by a method described later.

The reproduced image in which the block length mismatch is not detected by the image decoding means 7 and the image distortion is not detected by the image distortion detecting means 8 is a receiver image which is a good reception image in which no channel error occurs. It is output from 200 to a display means (not shown).

At the same time, the compressed image data stored in the reception buffer 6 is discarded and secured as an empty area for storing new data, and a reception confirmation signal is transmitted to the transmitter 100 to send a new image. Wait for compressed data to be received.

On the other hand, when the image distortion detecting means 8 detects distortion in the image, the image distortion detecting means 8 outputs the number indicating the block position where the image distortion is detected to the retransmit frame determining means 5.

The retransmitted frame determining means 5 checks whether or not the block number received from the image distortion detecting means 8 matches the block number determined to have a mismatch in block length. The number of the frame including the block is determined, and the transmitter 10 is used as a retransmission request signal.
Transmit to 0.

On the other hand, when the block number detected by the image distortion detecting means 8 and the block number detected by the image decoding means 7 do not match, the retransmitted frame determining means 5 sends a retransmission request signal to the transmitter 100. Instead of transmitting the reception confirmation signal to the transmitter 100.

The operation of the transmitter 100 for the resend request is the same as that of the data communication system of the first embodiment.

The receiver 200 having the compressed image data retransmitted from the transmitter 100 updates the contents of the reception buffer 6 with the retransmitted frame, and when the reception frames for one image are prepared, the image decoding is performed again. The means 7 reproduces the image and outputs the reproduced image to the image distortion detecting means 8 to check whether the reproduced image is distorted. When the image distortion is detected, the above-mentioned resend request is transmitted by the transmitter 100. The receiving process of transmitting the image is repeated until the image decoding unit 7 and the image distortion detecting unit 8 no longer detect the same frame.

Needless to say, the retransmission frame determining means 5 may be provided with a counter for counting the number of retransmission requests, and the retransmission request may be made until the count value reaches a predetermined number.

As described above, according to the data communication system of the second embodiment, the block length transmitted together with the compressed image data when the image decoding means 7 of the receiver 200 decodes the compressed image data. The image decoding means 7 checks whether or not the data and the block length of the reproduced image data obtained by decoding the compressed image data match, and the image distortion detection means 8 blocks the presence or absence of distortion of the reproduced image. Each time, only when the block length mismatch and the image distortion are detected in the same block, the transmitter 100 transmits the frame including the compressed image data of the corresponding block again, and the retransmitted retransmission data is blocked. Output the reproduced image data obtained by replacing the data of the block where the length mismatch and the image distortion are detected, to the display means (not shown), If only one of the lock length mismatch or the image distortion is detected, it is assumed that no communication path error has occurred in that block, and the reproduced image data is output to the display means (not shown) and displayed. , A data error that does not affect the image quality of a reproduced image that occurs in a two-way communication path (not shown), and an image distortion that is difficult to be visually sensed because it has little influence on the reproduced image quality caused by other causes, that is, image distortion When the image distortion that is not detected by the detection unit 8 occurs, the retransmission is not performed, so that the throughput for transmitting the image information can be improved.

Next, a method for detecting the distortion of the reproduced image in the above embodiment will be described.

FIG. 5 is a diagram for specifically explaining the method of detecting an error in a reproduced image after image decoding in the above embodiment, where Nx, Sx, Wx, and Ex are respectively
These blocks are adjacent to the north, south, west, and east of X. In the above embodiment, the block of the image is encoded,
If it is assumed that the blocks are synchronized, the deterioration of the reproduced image due to the communication path error occurs in units of blocks.

That is, since there is a characteristic that an error propagates within a block, these characteristics are utilized to detect the distortion generated in the reproduced image in block units.

Specifically, first, the distortion function d _sm is defined as follows for a specific block. The pixel value of one block (8 × 8) of the image is represented in a matrix form like X, and [X] fc, [X] lc, [X] fr, [X]
Let lr be the column vector of the first pixel, the column vector of the last pixel, the row vector of the first pixel, and the row vector of the last pixel, respectively.

Then, d _sm is expressed by the following equation (1).

[0082]

(Equation 1)

Here, Nx, Sx, Wx, and Ex are blocks adjacent to the north, south, west, and east of X, respectively.

Further, α, β, γ, and δ are "when an error is detected in the adjacent block itself."
It is a coefficient that takes "0" and "1" otherwise.

It is considered that the smaller the d _{sm, the} higher the possibility that the block X is a correct block.

Then, applying this calculation to each block,
If the distortion function d _sm is above a certain threshold, it is a method of performing error detection assuming that an error has occurred.

Table 1 shows the specifications of the computer simulation performed using this apparatus.

FIG. 6 shows the CNR-throughput characteristic of the communication path.

The CNR-throughput characteristic shown in FIG.
In particular, a reproduced image having an SNR of 30 (dB) or more is shown.

The threshold value of the distortion function was set to 3162. Although the conventional method does not cause deterioration of the reproduced image,
If R is low, the throughput is greatly reduced.

In comparison with this, in the method of the second embodiment, it is understood that the throughput characteristic is improved because the deterioration of the image quality which is hard to be visually recognized is allowed.

[0092]

[Table 1]

The inventions made by the present inventors are as follows.
Although specifically described based on the embodiments of the present invention, the present invention is not limited to the embodiments of the present invention, and it is needless to say that various modifications can be made without departing from the gist of the present invention. .

[0094]

The effects obtained by typical ones of the inventions disclosed in the present application will be briefly described as follows.

Since it is not necessary to transmit the data such as the error detection code, which is the data unrelated to the image information of the original image, to the receiving side, the image data can be communicated without lowering the communication throughput.

[Brief description of the drawings]

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

FIG. 2 is a diagram for explaining a block configuration when an original image is divided into a plurality of blocks.

FIG. 3 is a diagram for explaining a schematic configuration of blocks and frames according to the first embodiment.

FIG. 4 is a block diagram showing a schematic configuration of a data communication system according to a second embodiment of the present invention.

FIG. 5 is a diagram for specifically explaining a method of detecting an error in a reproduced image after image decoding according to the embodiment of the present invention.

FIG. 6 is a CNR- of a communication path according to the embodiment of the present invention.
It is a figure which shows a throughput characteristic.

FIG. 7 is a diagram for explaining a problem of a conventional data communication system.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Image coding means, 2 ... Frame construction means, 3 ... Transmission buffer, 4 ... Channel error detection means, 5 ... Retransmission frame determination means, 6 ... Reception buffer, 7 ... Image decoding means,
8 ... Image distortion detecting means, 100 ... Transmitter, 200 ... Receiver.

Claims (2)

[Claims] 1. When transmitting a digital compression coded image using a bidirectional communication system in which a channel error occurs,
When there is an error in the received data, in the data communication system that detects the error on the receiving side and requests the transmitting side to retransmit the data with the detected error, the transmitting side divides the original image into multiple blocks. It is divided, the number of bits of each block is binary-coded, the blocks are arranged in the order of appearance, block length data carrying bit information of each block, and compressed image data compressed and coded for each block. And an image encoding unit for outputting the block length data and the compressed image data are divided into predetermined number of bits to form a plurality of frames each having a unique identification number. A frame forming means that forms transmission frame data by combining them in the order of identification numbers and a transmission buffer that stores the transmission frame data are provided. A reception buffer that receives the input transmission frame data and accumulates it as reception data, and divides the reception data accumulated in the reception buffer into the block length data and the compressed image data,
The compressed image data is decoded into reproduced image data and reproduced as an image, the end of the block of the compressed image data is detected, and the number of bits from the end of the immediately preceding block to the end of the decoded block is the block length. An image decoding unit that determines whether or not the number of bits of the block recorded in the data matches, and determines that an error has occurred in the block if the numbers do not match, and an image decoding unit that specifies the number of the block. Retransmission frame determining means for identifying the identification number of the frame including the block based on the number identified by the image decoding means, and transmitting a retransmission request signal including the identification number of the identified frame to the transmission side. When the retransmission request signal is transmitted from the reception side to the transmission side, the transmission buffer retransmits based on the retransmission request signal. The retransmission data of the frame is determined and transmitted to the reception side, and on the reception side that receives the retransmitted transmission frame data, the reception buffer retransmits the retransmitted frame data to a specified identification number. A data communication system, characterized in that the received data is allocated and updated, and the image decoding means reproduces an image based on the updated received data. 2. When transmitting a digital compression coded image using a bidirectional communication system in which a channel error occurs,
When there is an error in the received data, in the data communication system that detects the error on the receiving side and requests the transmitting side to retransmit the data with the detected error, the transmitting side divides the original image into multiple blocks. It is divided, the number of bits of each block is binary-coded, the blocks are arranged in the order of appearance, block length data carrying bit information of each block, and compressed image data compressed and coded for each block. And an image encoding unit for outputting the block length data and the compressed image data are divided into predetermined number of bits to form a plurality of frames each having a unique identification number. A frame forming means that forms transmission frame data by combining them in the order of identification numbers and a transmission buffer that stores the transmission frame data are provided. A reception buffer that receives the input transmission frame data and accumulates it as reception data, and divides the reception data accumulated in the reception buffer into the block length data and the compressed image data,
The compressed image data is decoded into reproduced image data and reproduced as an image, the end of the block of the compressed image data is detected, and the number of bits from the end of the immediately preceding block to the end of the decoded block is the block length data. It is determined whether or not the number of bits of the block recorded in No. 3 is coincident with each other, and if the number of bits is not coincident with each other, it is determined that an error has occurred in the block, The presence or absence of the image distortion of each block is checked from the output signal of the image decoding means, and when the image distortion is detected, the image distortion detecting means for specifying the number of the corresponding block is input from the image decoding means. Check whether the number of the block in which the error is detected matches the number of the block in which the image distortion is detected by the image distortion detecting means. If they match, the retransmission frame detection means that specifies the identification numbers of all the frames that include the block and transmits a retransmission request signal for requesting retransmission of the specified frames to the transmission side. When the retransmission request signal is transmitted from the reception side to the transmission side, the transmission buffer determines retransmission data of the frame to be retransmitted based on the retransmission request signal and transmits it to the reception side. Then, on the receiving side that received the retransmitted transmission frame data, the reception buffer updates the reception data by assigning the retransmitted retransmission frame data to a specified identification number, and decoding the image. A means for reproducing an image based on the updated received data, the data communication system.