JP2985173B2 - Digital information receiver - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital information receiving apparatus for receiving digital information such as digital image information having a certain correlation between information.

[Conventional technology]

2. Description of the Related Art In general, in a system for digitizing and transmitting an information signal such as image information, a method of converting the information signal into a transmission code suitable for a transmission medium and transmitting the converted signal is used. 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 measure against transmission errors.

5A and 5B are schematic block diagrams of a conventional digital information transmission system. FIG. 5A shows a transmission system, and FIG. 5B shows a reception system. In the transmission system, the compression encoding circuit 10 compression-encodes an information signal such as digital image information using the 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 transmission error countermeasure. 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 result to the transmission path.

On the other hand, on the receiving side, the demodulation circuit 16 demodulates the transmission signal on the transmission line, the error correction decoding circuit 18 corrects the error that occurred on the transmission line, and the decompression circuit 20 performs the reverse Decompress and restore. For the data determined to be uncorrectable by the error correction decoding circuit 18, the error correction circuit 22 corrects the error by data replacement or the like.

[Problems to be solved by the invention]

However, in the conventional example as described above, the correlation between the compression encoding / decoding process and the error correction encoding / decoding process is not considered, and particularly, the unit of the chain error correction code including the outer code and the inner code is not considered. No consideration has been given to the relation with the units of the compression processing and the optimization of the processing order, and in this respect, it is not yet complete.

SUMMARY OF THE INVENTION An object of the present invention is to provide a more efficient digital information receiving apparatus, paying attention to the relevance between processes.

[Means for solving the problem]

A digital information receiving apparatus according to the present invention provides a compression code obtained by performing a compression process using a correlation between samples of a digital information signal by using a predetermined number of samples as one unit. When,
A first parity constituting a first error correction code corresponding to the unit of the compression code, and a second parity constituting a second error correction code composed of a unit different from the first error correction code A first decoding unit for receiving the parity and correcting the error of the compression code and the first parity by decoding the second error correction code;
A second decoding unit that corrects an error of the compression code by decoding the first error correction code, and determines presence or absence of an uncorrectable error occurring in the compression code for each of the first error correction codes. Storage means for storing the determination result of the second decoding means as a correction flag, and processing means for correcting an uncorrectable error occurring in the compression code using the correction flag stored in the storage means. It is characterized by having.

[Action]

By the above-mentioned means, the chain error correction code is provided with higher error correction capability, and the error correction code to be decoded first is made to correspond to the unit of the compression code, thereby compressing the error correction code decoded last. It is possible to correspond to the code unit, and the error flag of the error correction code (outer code) can be used as a correction flag as it is. As a result, it is possible to appropriately correct a non-error-correctable compression code with a simple circuit configuration.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIGS. 1A and 1B are schematic configurations of an embodiment taking an example of a case in which a preceding value prediction DPCM method is used as a compression method of an information signal, and a chain coding error correction code using double coding is used as an example. FIG. 1A is a block diagram, and FIG.
FIG. 1B shows a receiving system.

In FIG. 1A, an input terminal 30 receives an information signal obtained by digitizing a horizontally scanned image signal such as a television signal. The previous value prediction DPCM circuit 32 converts the digital image information signal at the input terminal 30 into a DPCM data sequence having a reset value for each predetermined length i as shown in FIG. 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.

DPCM data from the previous value prediction DPCM circuit 32 is added with a double-coded error correction code by an outer code encoder 34 and an inner code encoder 36. FIG. 3 shows a configuration of a data string to which the error correction code is added. In this embodiment,
The outer code matches the horizontal scanning direction of the image data after DPCM, that is, the direction of the correlation used at the time of information compression, and the number of information points of the code is i, which is one unit of the DPCM data including the reset value. Then, according to a predetermined error correction code generation method,
By adding a parity P ₂ to form an outer code. Further, in this embodiment, the inner code is in the vertical direction of the image as shown in FIG. 3, it is formed by adding a parity P ₁ a j line of image information as information points. Here, a Reed-Solomon code or the like is conceivable as the error correction code.

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

Next, the operation of the receiving side (FIG. 1B) will be described. 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 an error generated on the transmission path as much as possible. The outer code decoding circuit 44 decodes the outer code and corrects the error according to a predetermined algorithm in the same manner as the inner code. For codes determined to be uncorrectable at the time of decoding the outer code, a correction flag indicating uncorrectable is stored in a correction flag memory.
Write to 46. Inner code decoding circuit 42 and outer code decoding circuit 44
The information signal, which has been subjected to the error correction processing in, is applied to the DPCM decoding circuit. The DPCM decoding circuit decodes the DPCM code and restores the image data.

Here, consider a case where an error remains in the decoding processing of both the inner code and the outer code, that is, a case where an error exceeding the correction capability of the error correction code used here occurs in the transmission path. As described above, since the image data is compression-encoded by the previous value prediction DPCM and transmits the difference value from the previous value, if an uncorrectable error remains in the group of data, As shown, in one unit of the DPCM, that is, in the data string of length i divided by the reset value, the error propagates after the remaining error data, and all the data after the remaining error data are incorrect. It becomes something. In FIG. 4, ×
Indicates data that remains erroneous, and △ indicates data that results in DPCM decoding error due to x data.

Whether or not the output of the DPCM decoding circuit 48 needs to be corrected can be determined by referring to the correction flag memory 46. That is, in the present embodiment, the structure of the outer code is changed to DP as shown in FIG.
Since it is the same as the unit length of CM, one unit of DPCM is 1
Two correction flags are prepared, and by referring to the correction flag memory 46, whether the output of the DPCM decoding circuit 48 is directly supplied to the output terminal 52 or whether error correction is performed by a predetermined method is determined instantaneously. Can be determined. Error correction circuit 50
Corrects the data string in which such an error remains in units of data lines of length i. For example, the data of the line including the error (length i) is replaced with the data of the previous line or the rear line to correct the data.

In the present embodiment, the prior value prediction DP
Although CM was used, the present invention is not limited to this. That is, in the configuration of the subsequent error correction code, if it is a compression method using a direction of correlation that can be matched with the direction forming the error correction code decoded last when decoding the chain error correction code,
It can be used in the present invention. Further, in the present embodiment, the case where double coding is performed as the chain error correction code is taken as an example, but this is not limited to double coding, and the present invention can be applied to a case where a code is configured n times.

〔The invention's effect〕

As can be easily understood from the above description, according to the present invention, a system capable of efficiently detecting and correcting an uncorrectable error occurring in digital information can be realized with a simple circuit configuration.

[Brief description of the drawings]

FIGS. 1A and 1B are schematic block diagrams of one embodiment of the present invention, FIG. 2 is an explanatory diagram of a processing unit of the DPCM, and FIG.
5A and 5B are explanatory diagrams of encoding for error correction, and FIG. 4 shows a result of error propagation during DPCM decoding.
The figure shows a schematic block diagram of a conventional example. 30 ... input terminal, 32 ... previous value prediction DPCM circuit, 34 ... outer code encoding circuit, 36 ... inner code encoding circuit, 38 ... modulation circuit, 40 ... 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

Claims (1)

(57) [Claims] 1. A compression code obtained by performing a compression process on a digital information signal using a correlation between samples of the digital information signal by using a predetermined number of samples as one unit, and the compression code And a second parity constituting a second error correction code composed of a unit different from the first error correction code. A receiving device, comprising: first decoding means for correcting the error of the compression code and the first parity by decoding the second error correction code; and decoding the first error correction code. The second decoding means corrects the error of the compression code, determines whether there is an uncorrectable error in the compression code, for each first error correction code, and determines whether the second decoding means has an error. Digital information reception comprising: storage means for storing a result as a correction flag; and processing means for correcting an uncorrectable error occurring in the compression code using the correction flag stored in the storage means. apparatus.