JPH0392017A - Error detection correcting and coding device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention is an error detection and correction method for decoding a code string obtained by error correction encoding digital information having correlation such as digital image information using a chain encoding configuration. This invention relates to a decoding device.

[Prior Art] Generally, in systems that digitize and transmit (record) information signals such as image information, a method is used in which the signals are converted into a transmission code 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.

5(A) and 5(B) are schematic block diagrams of a conventional digital information transmission system, and FIG.
A) shows a transmission system (recording system), and FIG. 5 CB) shows a reception system (reproduction system). Compression encoding is performed using the correlation. Compression encoding circuit 10
The output of is applied to the error correction encoding circuit 12, where
Error correction encoding is performed as a countermeasure against transmission errors. Then, the modulation circuit 14 converts the output of the error correction encoding circuit 12 into
It is modulated in a form suitable for the characteristics of the transmission path and recorded on the output recording medium on the transmission path.

On the other hand, on the receiving side (reproduction side), the demodulation circuit 16 demodulates the transmission signal on the transmission path, the error correction decoding circuit 18 corrects errors occurring on the transmission path, and the expansion circuit 20 and the compression encoding circuit 10 performs decompression and restoration using the reverse process. 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. [Problems to be Solved by the Invention] However, in the conventional example as described above, when performing a correction operation in the error correction circuit 22, the correction flag from the error correction decoding circuit 18 is referred to and the compression The information to be modified must be determined based on the method. In this way, information that cannot be corrected cannot be determined simply by the correction flag, and as mentioned above, a circuit is absolutely necessary to determine the information to be corrected, and it is necessary to increase the processing speed and simplify the circuit configuration. It was difficult to do so.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an error detection and correction decoding device that can increase the processing speed of the entire device and simplify the circuit configuration. [Means for Solving the Problems] In order to achieve this objective, the error detection and correction decoding device of the present invention has an error correction circuit that uses a chain-coded error correction code to compress information. The direction of the correlation that was previously decoded is repeatedly decoded to match the direction of the last decoded error correction code, and the correction flag of the last decoded error correction code is used to determine the correction operation of the error correction circuit. It was configured to do this.

[Operation] By configuring as described above, the direction of correlation used in compression encoding during transmission matches the direction of configuration of the error correction code that is finally decoded during decoding on the receiving side, so the correction flag is This corresponds to the code to be corrected, and it has become possible to perform correction IA processing for codes that cannot be error corrected with a simple circuit configuration and at high speed.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

Figures 1(A) and 1(B) show an information transmission system that uses the previous prediction DPCM method as the information signal compression method and uses double encoding as the chain-coded error correction code. It is a schematic block diagram of an embodiment to which the invention is applied, and FIG. 1(A) shows its transmission system (recording system);
FIG. 1(B) shows a receiving system (reproducing system).

In FIG. 1A, an information signal obtained by digitizing a horizontally scanned image signal, such as a television signal, is manually input to an input terminal 30. Previous price forecast tllDPc
The M circuit 32 converts the digital image information signal at the input terminal 30 into a DPCM data string having a reset value for each predetermined length i, as shown in FIG. In this embodiment, previous value prediction is used as the prediction method, so the direction of correlation used during compression is the horizontal scanning direction. The DPCM data generated by the previous value prediction DPCM 32 is added with a double-encoded error correction code by an outer code encoding circuit 34 and an inner code encoding circuit 36. Figure 3 shows the structure of a data string to which the error correction code has been added. In this embodiment, the outer code is formed by adding parity P, with J lines of image information as the number of information points, in the vertical direction of the image, as shown in FIG. In addition, in this embodiment, the inner code is made to match the horizontal scanning direction of the image data after CPDM, that is, the direction of the correlation used during information compression, and the number of information points of the code is the same as the DP including the reset value.
It is set to i, which is the first car position in the CM data. Then, according to a predetermined error correction code generation method, parity P2 is added to form an inner code.

As the error correction code here, a reset 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 of the receiving side (reproducing side) shown in FIG. 1(B) will be explained. The signal received from the transmission path is demodulated by the demodulation circuit 40. The demodulated code string is temporarily stored in the memory 41.

Further, 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.

Then, decoding of the inner code and outer code is repeated multiple times using the error-corrected code. For the final decoding, the direction configuring the error correction code to be decoded and the DPCM (
The direction of correlation (horizontal direction) used during compression encoding) is made to match. That is, in this embodiment, decoding is completed by decoding the inner code shown in FIG.

After decoding the error correction code as described above, for the code determined to be uncorrectable, a correction flag indicating uncorrectability is written in the 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 circuit 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 DPCM, and the difference value from the previous value is transmitted, so if an uncorrectable error remains in a group of data, the fourth
As shown in the figure, within one unit of DPCM, 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. It ends up being wrong. In FIG. 4, x indicates data that remains erroneous, and Δ indicates data that results in a DPCM decoding error due to the x data.

Whether or not the output of the D PCM decoding circuit 48 requires modification is determined by
This can be determined by referring to the correction flag memory 46. That is, in this embodiment, since the structure of the inner code is the same as the unit length of DPCM as shown in FIG.
One correction flag is prepared for each CM unit, and by referring to the correction flag memory 46, the DPC
It is possible to instantly decide whether to supply the output of the M 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, the data on the line containing the error (length i) is replaced by using data from the previous line or the next line to correct it. In this embodiment, the previous value prediction DP is used as the image information compression method.
Although CM was used, the present invention is not limited thereto. That is,
Any compression method that uses a direction of correlation that matches the direction constituting the error correction code that is last decoded when decoding the chained error correction code in the subsequent configuration of the error correction code can be used in the present invention. . 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 not limited to double encoding, and a case in which the code is configured n times can also be applied.

[Effects of the Invention] As explained above, according to the error detection and correction decoding device of the present invention, code error correction and modification processing can be realized at high speed and with a simple circuit configuration.

[Brief explanation of drawings]

Figure 1 (A). (B) is a diagram showing a transmission system and a reception system of an information transmission system as an embodiment of the present invention; FIG. 2 is a diagram for explaining the prior value prediction DPCM processing in the system of FIG. 1; Fig. 3 is a diagram for explaining error correction and correct code format rules in the system of Fig. 1, Fig. 4 is a diagram showing error propagation during DPCM decoding, and Fig. 5 (A). (B) is a diagram showing a transmission system and a reception system of a conventional information transmission system. In the figure, 32 is a previous value predictive encoding circuit, 34 is an outer code encoding circuit, 36 is an inner code encoding circuit, 38 is a modulation circuit, 40 is a demodulation circuit, 42 is an inner code decoding circuit, and 44 is an outer code decoding circuit. 46 is a correction flag memory, 48 is a DPCM decoding circuit, and 50 is an error correction circuit. 1 ぢ○ (A 87 diagram (B,)

Claims (2)

[Claims] (1) The digital information to be transmitted is compressed using its correlation, and an error correction code for detecting or correcting code errors on the transmission path is configured in a chain code and transmitted. an error correction circuit that decodes the chain-coded error correction code;
and an error correction circuit that corrects uncorrectable data,
The error correction circuit repeatedly decodes the chain-coded error correction code so that the direction of the correlation matches the direction of the error correction code to be decoded last, and An error detection and correction decoding device characterized in that a correction operation of the error correction circuit is determined using a correction flag. (2) The error correction code is double encoded using an inner code and an outer code, and the error correction circuit decodes the inner code last.
The error detection and correction decoding device described in section 1).