JPH0744464B2 - Digital signal regenerator - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a digital signal reproducing apparatus for decoding error-correction-coded digital signals at regular intervals.

[Prior art]

Conventionally, in this type of digital signal reproducing apparatus, an (m, k, d) code is used as an error correction code (m: code length, k:
Information length, 2: minimum distance). Then, between the information data interval (hereinafter referred to as T) included in one codeword (codeword) and the time (decoding time) required to correct an error included in this one codeword, there is shown in FIG. There was a relationship as shown in. FIG. 1 (a) shows the clock pulse of the period T, and FIG. 1 (b) shows the decoding time in synchronization with FIG.

Here, the relationship between the correction capability with a code, the minimum distance, and the decoding time will be described before the description of the drawings.

When the number of errors (the number of error information) is ne, the number of erasures (the number of lost information) is nε, and the minimum distance is d, the following formula is established.

2ne + nε + 1 ≦ d (1) This shows that with a code having the minimum distance d, it is possible to correct up to ne errors and nε erasures that satisfy this equation. That is, the larger the minimum distance d, the more errors and erasures can be corrected.

On the other hand, regarding the relationship between the correction capability and the decoding time, generally, the larger the number of errors and the number of erasures, the more complicated the decoding algorithm and the longer the decoding time (details will be described later).

Therefore, in an error correction circuit that performs real-time decoding or performs decoding at constant time intervals, the minimum distance d for which a decoding time> T is satisfied at a code having a large minimum distance d (ne, nε that holds the code of the expression (1)). Code is used, ne, nε are limited so that the decoding time becomes shorter than T as shown in FIG. 1 (first method). Or, ne number of errors for which the equal sign of equation (1) holds, n
Even in the case of ε erasures, a code having a small minimum distance d such that the composite time is smaller than T is used (second method).

FIG. 2 shows, as an example, a table of the number of operations required for decoding the (32,24,9) Reed-Solomon code. As a decoding method, an algorithm for obtaining an error position equation from the syndrome by the Euclidean divisor method (Reference: Y. Sugiyam
a, et all: “A method for solving key equation for d
ecoding Goppa codes ", Inform, Cont., 27, pp.87−99 En
n.1975) was used. In the figure, the horizontal axis is the number of errors for correction, and the vertical axis is the number of erasures.

In FIG. 2, for example, when ne is 0 and nε is 1, the number of operations is 483, and when ne is 4 and nε is 0, the number of operations is 893, which is about a double difference. This means that there is a difference of about two times in decoding time, and the relationship between the above-mentioned correction ability and decoding ability can be understood.

Further, FIG. 3 shows the relationship between the decoding time and T. Third
Similar to FIG. 1A, FIG. 1A shows a clock pulse having a period T. FIGS. 3 (b) and 3 (c) show the decoding time in synchronism with the decoding time. In FIG. 3 (b), when the decoding time is smaller than T, the decoding time in FIG. It is a big case.

The relationship between the decoding time and T will be specifically described with reference to FIGS. 2 and 3 above. For example, the number of calculations corresponding to T is about 650
If the combination of ne and nε is expressed as (ne, nε), then (0,0), (0,1), (0,2), (0,3), (0,
The decoding time of the 9 sets of 4), (0,5), (1,0), (1,1), and (1,2) is smaller by T, which is as shown in FIG. 3 (b). In this case, decoding can be performed accurately without any problem. On the other hand, 16 sets other than the above 9 sets have a decoding time longer than T, that is, as shown in FIG. 3 (c), and the decoding is not completed within the time of T and the error cannot be corrected.

However, the number of calculations is not directly proportional to the decoding time, but the decoding time varies depending on the hardware configuration and the like. In addition, even if the en and nε are the same, different decoding values may cause different decoding times. Even in the case of (1, 3) in the above example (the number of operations 658), the decoding time is shorter than T and becomes as shown in FIG.

As can be understood from this, in the first method described above, ne and nε are limited, so in the case of (1,3) above, decoding is possible even though decoding is possible. Become.

Next, assuming that the number of calculations corresponding to T is 900, ne,
All combinations of nε satisfy the condition shown in FIG. 3 (b), and no problem occurs. However, on the contrary, there will be room. In this case, there is a possibility that even when nε is 9, decoding can be performed by slightly increasing the minimum code distance.

As can be understood from this, in the second method described above, there is a margin in the decoding time depending on the combination of ne and nε, so there is a possibility that the coding capability can be increased a little.

As described above, in the error correction method used in the conventional digital signal reproducing apparatus, the number of error information to be corrected is limited so that the decoding time does not exceed the information data interval T, and the decoding time and T are set. You have to have a margin,
Therefore, there is a drawback that the correction capability of the code is not sufficiently obtained.

[Outline of Invention]

The present invention has been made in order to eliminate the above-mentioned drawbacks of the conventional ones, and is provided with a decoding end detection means and a notification means in a decoder, and when the decoding is not completed within the data interval, a notification is issued. By doing so, it is an object of the present invention to provide a digital reproducing apparatus capable of maximizing the performance of a code and improving its reliability.

Example of Invention

Embodiments of the present invention will be described below with reference to the drawings. FIG. 4 is a schematic block diagram showing an embodiment of the present invention. In the figure, 1 is an input terminal for inputting a digital signal a containing an error, 2 is an error correction circuit for correcting an error contained in the digital signal a, and 7 is an error corrected by the error correction circuit 2. It is an output terminal for obtaining a digital signal. Reference numeral 6 denotes a synchronization signal generation circuit. The error correction circuit to which the synchronization signal c from the synchronization signal generation circuit 6 is input controls the start of decoding by the synchronization signal c, and the next If the synchronization signal c is given, the decoding is interrupted and the decoding of the next digital signal a is started. Denoted at 3 is a decoding end detection circuit, which receives the signal d necessary for judging the decoding end from the error correction circuit 2, generates a pulse when the decoding is completed, and gives a signal e to the pulse detection circuit 4. Is. Pulse detection circuit 4
Compares the signal c from the synchronizing signal generating circuit 6 and the signal e from the decoding end detecting circuit 3 to give a digital signal f to the notifying circuit 5. The notification circuit 5 outputs a notification signal to another circuit, and the pulse detection circuit 4 and the notification circuit 5 constitute a notification means 50.

FIG. 5 is a time chart for explaining the operation of the embodiment shown in FIG. The figure (a) is when the decoding time is smaller than T, and the figure (b) is when the decoding time is longer than T.

First, the operation when the decoding time is shorter than T will be described with reference to FIG. The error correction circuit 2 starts decoding with the signal c from the synchronization signal generation circuit 6 and gives a signal d to the decoding end detection circuit 3. The decoding end detection circuit 3 detects whether or not the decoding is completed based on the information from the signal d. Here, the pulse detection circuit 4 detects whether or not the signal e becomes the logic "1" during the period T. If the logic "1" is not detected, the digital signal f is set to the logic "1" for a certain period. Notification circuit 5
Let us know. Therefore, in this case, since the signal e becomes the logic "1" between the pulses of the synchronization signal c, the digital signal f which is the output of the pulse detection circuit 4 remains the logic "0", and the notification circuit 5 does not know what. Do not report.

Next, the operation when the decoding time is longer than T will be described with reference to FIG. The error correction circuit 2 starts decoding by the signal c from the synchronization signal generation circuit 6 and gives a signal d to the decoding end detection circuit 3. The decoding end detection circuit 3 detects whether or not the decoding is completed based on the information from the signal d, but since the decoding is not completed in this case, the signal e remains the logic "0". On the other hand, in the pulse detection circuit 4, the signal e does not become the logic "1" during the pulse interval (during the period T) of the synchronization signal c, so the signal f becomes the logic "1" for a certain period. The notification circuit 5 therefore receives this signal f and informs the other functions that the codeword during the pulse interval could not be corrected.

According to the present embodiment as described above, the decoding end detecting means circuit 3
Since the notification circuit 5 is provided, the decoding time is the data interval T.
If it exceeds, it is possible to detect this, so that it is not necessary to provide a margin between the information data interval T and the decoding time, and the correction capability of the code can be maximized. Therefore, the reliability of the device can be significantly improved as compared with the conventional one.

FIG. 6 shows another embodiment of the present invention, which is the case of a digital audio signal reproducing apparatus.

The input terminal 1, the error correction circuit 2, the decoding end detection circuit, the pulse detection circuit 4 (reporting means), the synchronization signal generation circuit 6, and the output terminal 7 are the same as those shown in FIG. Then, a correction circuit 8 and a selector 9 are added. The correction circuit 8 performs, for example, an average value correction and a previous value hold on the input information.

Next, the operation will be described.

The digital signal a including an error input to the terminal 1 is
After the error is corrected by the error correction circuit 2, it is added to one input of the selector 9 as a digital signal b, and after being corrected by the correction circuit 8, it is input to the other input of the selector 9 as a digital signal g. Added.

The selector 9 is configured so that its input is switched by the output signal f of the pulse detection circuit 4, and the signal f
Is a logic "0", the output b of the post-correction circuit 2 is selected, and if the signal f is a logic "1", the output g of the correction circuit 8 is selected, and this is supplied to the output terminal 7 as a digital signal h.

Therefore, the correction output is given to the output terminal 7 when the decoding is completed within the data interval T, and the correction output is provided when the decoding is not completed within the data interval.

In the present embodiment as described above, the correction circuit 8 can not only maximize the code correction capability as in the above embodiment, but also when the decoding time exceeds the data interval T, that is, when the input digital signal has many errors. Since the output of is selected, it is possible to prevent the generation of noise noise or the interruption of sound.

〔The invention's effect〕

As described above, according to the present invention, the time required for error correction decoding of one codeword differs depending on the number of errors, and the error correction decoding means is controlled to perform decoding at constant time intervals. In the digital signal reproducing apparatus having the decoding start means for starting the decoding, the decoding end detection means and the notification means are provided in the decoder, and when the decoding is not completed within the information data interval, the notification is performed. The number of correctable error information and the minimum distance of the code are not limited, and the correction capability possessed by the code can be maximized, and a highly reliable digital reproducing device can be obtained. .

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a data interval and a decoding time of an error correction circuit used in a conventional digital signal reproducing device,
FIG. 2 is a diagram showing the number of operations required for decoding a (32,24,9) Reed-Solomon code, FIG. 3 (a) is a diagram showing a data interval, and FIGS. 3 (b) and (c) are decoding times, respectively. Is shorter than the data interval, the decoding time is longer than the data interval, FIG. 4 is a block diagram of a digital signal reproducing apparatus according to an embodiment of the present invention, and FIG. 5 is an operation of the embodiment of FIG. FIG. 6 is a time chart diagram for explaining the above, and FIG. 6 is a diagram showing another embodiment of the present invention. 3 ... Decoding end detection circuit, 50 ... Notification means. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. An error correction decoding means for varying the time required for error correction decoding of one code word depending on the number of errors, and a decoding start means for controlling this error correction decoding means to start decoding at fixed time intervals. And a detection signal from the decoding end detecting means within the fixed time interval, the decoding end detecting means detecting whether or not the decoding means has finished decoding one codeword. A digital signal reproducing device, characterized in that the digital signal reproducing device is provided with a notifying means for making a notification when the above is not obtained.