JPH01228332A - Digital information transmission system - Google Patents

Abstract

PURPOSE:To more efficiently transmit digital information with a small circuit by using a chain encoding error correcting code where the direction of correlations used for compression encoding at the time of transmission and the direction of an error correcting code finally decoded at the time of decoding on the reception side coincide with each other. CONSTITUTION:A preceding value forecasting DPCM circuit 32 converts the digital picture information signal of an input terminal 30 to a DPCM data string. The direction of correlations used for compression is the horizontal scanning direction. A double encoded error correcting code is added to this DPCM data by an outer code encoding circuit 34 and an inner code encoding circuit 36. The outer code is equalized to the direction of correlations used for information compression. The signal received from a transmission line is demodulated by a demodulating circuit 42, and an inner code decoding circuit 42 and an outer code decoding circuit 44 decode the inner code and the outer code respectively in accordance with a prescribed algorithm to correct errors. A correction flag indicating that correction is impossible is written in a correction flag memory 46 with respect to the code whose correction is judged to be impossible at the time of decoding the outer code. An error correcting circuit 50 uses the correction flag to correct the data string where there is error left.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a system for transmitting digital information, such as digital image information, that has a certain correlation between pieces of information.

[Conventional technology]

Generally, in systems that digitize and transmit information signals such as image information, a method is used in which the signals are converted into transmission codes that are compatible with the transmission medium and then transmitted. At this time, input data is often compressed and encoded due to transmission bit rate limitations, and an error correction code is added as a countermeasure against transmission errors.

5A and 5B are schematic block diagrams of conventional digital information transmission systems, with FIG. 5A showing a transmitting system and FIG. 5B showing a receiving system.

In the transmission system, a compression encoding circuit 10 compresses and encodes information signals such as digital image information by utilizing their correlation. The output of the compression encoding circuit 10 is applied to an error correction encoding circuit 12, where error correction encoding is performed as a countermeasure against transmission errors.

Then, the modulation circuit 14 modulates the output of the error correction encoding circuit 12 into a form suitable for the characteristics of the transmission path, and outputs the modulated signal to the transmission path.

On the other hand, on the receiving side, a demodulation circuit 16 demodulates the transmission signal on the transmission path, an error correction decoding circuit 18 corrects errors occurring on the transmission path, and an expansion circuit 20 performs processing opposite to that of the compression encoding circuit 10. Extend and restore. For data determined to be uncorrectable by the error correction decoding circuit 18, the error is corrected by data replacement or the like in the error correction circuit 22.

[Problem to be solved by the invention]

However, in the conventional example as described above, the mutual relationship between each processing stage is not considered, and from an overall viewpoint, it is still not perfect.

The present invention aims to provide a more efficient digital information transmission system by paying attention to the relationship between each process.

[Means for Solving the Problems] In the digital information transmission system according to the present invention, the transmitting device includes a compression encoding circuit that compresses a digital information signal to be transmitted using the correlation that the information signal has;
Equipped with a circuit that generates a chain-coded error correction code in which the direction of the correlation used in the compression encoding circuit matches the direction constituting the error correction code to be decoded last at the time of decoding on the receiving side. do. The receiving device includes an error correction circuit that decodes the chain-coded error correction code, and a circuit that corrects uncorrectable data using a correction flag of the error correction code last decoded in the error correction circuit. do.

[Effect]

The direction of the above correlation used in compression encoding during transmission,
By using a chain-coded error correction code that matches the direction of the error correction code that is last decoded during decoding on the receiving side, it is possible to quickly discover data groups that cannot be error corrected with a simple circuit configuration. It becomes like this. Therefore, more efficient digital information transmission can be achieved with a smaller circuit.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. FIG. 1A and FIG. 1B show a schematic configuration of an embodiment in which a previous value prediction DPCM method is used as an information signal compression method and a double coding method is used as a chain coding error correction code. FIG. 1A shows the transmitting system, and FIG. 1B shows the receiving system.

In FIG. 1A, an information signal obtained by digitizing a horizontally scanned image signal, such as a television signal, is inputted to an input terminal 30. Previous value prediction DPCM circuit 3
2 inputs the digital image information signal of the input terminal 30 to a second
As shown in the figure, the DP has a reset value for each predetermined length i.
Convert to CM data string. In this embodiment, since the previous value prediction is used as the prediction method, the direction of the correlation used at the time of compression is the horizontal scanning direction.

The DPCM data from the previous value prediction DPCM circuit 32 is processed by the outer code encoding circuit 34 and the inner code encoding circuit 36.
A double encoded error correction code is added.

FIG. 3 shows the structure of a data string to which the error correction code is added. In this embodiment, the outer code is made to match the horizontal scanning direction of the subsequent image data, that is, the direction of correlation used during information compression, and the number of information points of the code is determined by the DPC including the reset value.
Let i be one unit of M data. Then, according to a predetermined error correction code generation method, parity P2 is added to form an outer code. In addition, in this embodiment, the inner code is the third
As shown in the figure, in the vertical direction of the image, 3
It is formed by adding parity P1 with 947 minutes as the number of information points. As the error correction code here, a Reed-Solomon code or the like can be considered.

In this way, the digital image information signal to which the error correction code has been added is modulated in a form suitable for the characteristics of the transmission path by the modulation circuit 38, and sent out on the transmission path. The transmission order on the transmission path is arbitrary as long as the receiving side can correctly understand and restore the image.

Next, the operation on the receiving side (FIG. 1B) will be explained.

The signal received from the transmission path is demodulated by the demodulation circuit 42. The inner code decoding circuit 42 decodes the inner code according to a predetermined algorithm, and corrects errors occurring on the transmission path as much as possible. As with the inner code, the outer code decoding circuit 44 decodes the outer code according to a predetermined algorithm and corrects errors. For codes that are determined to be uncorrectable at the time of decoding the outer code, it indicates that the code is uncorrectable. Write the correction flag to correction flag memory 46. Inner code decoding circuit 42
The information signal that has undergone error correction processing in the outer code decoding circuit 44 is applied to the DPCM decoding circuit 42.

The DPCM decoding path 42 decodes the DPCM code and restores image data.

Here, let us consider a case where errors remain in the decoding processing of both the inner code and the outer code, that is, a case where an error exceeding the correction ability of the error correction code used here occurs on the transmission path. As mentioned above, the image data is compressed and encoded by the previous value predictive OPCM, and the difference value from the previous value is transmitted, so -
If uncorrectable errors remain in the group data, the fourth
As shown in the figure, within one unit of DPCH, that is, a data string of length i separated by reset values, the error propagates after the data with the error remains, and all data after the data with the error remain. In Fig. 4, the × indicates data that remains incorrect, and the △ indicates the DPC caused by the × data? I Indicates data that results in a decoding error.

Whether or not the output of the DPCM decoding circuit 48 requires correction can be determined by referring to the correction flag memory 46. That is, in this embodiment, the structure of the outer code is the same as the unit length of the DPCM as shown in FIG.
One correction flag is prepared for each unit of M, and by referring to the correction flag memory 46, the DPCM
It is possible to instantly decide whether to supply the output of the decoding circuit 48 as it is to the output terminal 52 or to perform error correction using a predetermined method. The error correction circuit 50 corrects the data string in which errors remain in this way in units of data lines of length i.

For example, using data such as the front line or the back line,
Correct by replacing the data of the line (length i) containing the error.

In this embodiment, the previous value is used as the image information compression method.

Although the predictor side is used, the present invention is not limited thereto. In other words, the present invention can be applied to any compression method that uses a direction of correlation that can match the direction of the error correction code that is decoded last when decoding the chained error correction code in the configuration of the error correction code that follows. Available. Further, in this embodiment, a case where double encoding is performed as a chain error correction code is taken as an example, but this is also not limited to double encoding, and can also be applied to a case where the code is configured n times.

[Effects of the Invention] As can be easily understood from the above explanation, according to the present invention, it is possible to construct a system that transmits digital information in a very short time and efficiently with a small circuit configuration.

[Brief explanation of the drawing]

1A and 1B are schematic configuration block diagrams of an embodiment of the present invention, FIG. 2 is an explanatory diagram of the processing unit of the previous value prediction DPCH, and FIG. 3 is an explanatory diagram of encoding for error correction, FIG. 4 shows the result of error propagation during DPCM decoding, and FIGS. 5A and 5B are schematic block diagrams of a conventional example. 30-input terminal 32-.-previous value prediction DPCM circuit 3
4--Outer code encoding circuit 36--Inner code encoding circuit 3
8 - Modulation circuit 4 - Demodulation circuit 42 - Inner code decoding circuit 44 - Outer code decoding circuit 46 - Correction flag memory 48 - DPCM decoding circuit 50 - Error correction circuit 52 - Output terminal Fig. 1A Figure 1B Figure 5A Figure 5B Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] A compression encoding circuit that compresses a digital information signal to be transmitted using the correlation of the information signal, and the direction of the correlation used in the compression encoding circuit and the final result when decoding on the receiving side. a transmitting device comprising a circuit that generates a chain-coded error-correcting code in which the direction constituting the error-correcting code to be decoded matches, and an error-correction circuit that decodes the chain-coded error-correcting code; 1. A digital information transmission system comprising a receiving device comprising a circuit for correcting uncorrectable data using a correction flag of an error correction code last decoded in the error correction circuit.