JPH0654590B2 - Reproduction method of digital data - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a digital data recording / reproducing apparatus, and more particularly to a digital data reproducing method for reproducing digital information from a recording medium such as an optical disk or a magnetic tape.

BACKGROUND ART In a PCM (pulse code modulation) reproduction system of voice,
A method is known in which the content of the memory is read and replaced with an error pattern (see Japanese Patent Laid-Open No. 59-175011), and the configuration is shown in FIG.

In FIG. 3, the PCM audio information A / D converted by the A / D (analog / digital) converter 1 is stored in the buffer memory 2 and sent to the modulation circuit 4 together with the parity generated by the correction code generation circuit 3. The modulation circuit 4
Then, the error detection code is added and recorded on the recording medium 5.

During reproduction of information from the recording medium 5, the signal read from the recording medium 5 is demodulated by the demodulation error detection circuit 6,
If no error is detected in the data block, it is transferred to the buffer memory 7, and if an error is detected, that portion is not written in the memory 7. The error in the data on the memory 7 is corrected by the error correction circuit 8, the D / A (digital / analog) converter 9 converts the error into an analog signal, and the analog signal is output. At this time, an error data pattern is generated by the D / A converter 9 and written in the already read area of the buffer memory 7.

The read operation in such a configuration will be described with reference to the flowchart of FIG.

First, the signal read from the recording medium 5 is demodulated by the demodulation error detection circuit 6 (step 1), it is determined whether or not the sync code is detected in step 2, and if it is detected, the block error is detected in step 3. Is detected, and if not detected, data is written to the buffer memory 7 (step 4).

Then, in step 5, it is judged whether or not the reading of all blocks is completed, and if not completed, the process returns to step 1. When all blocks have been read,
The error correction circuit 8 performs signal processing for error correction (step 6), and the error data pattern generated by the D / A converter 9 during D / A conversion is stored in the buffer memory 7
Is written in the already read area of the memory (step 7).

In this way, since the data in the buffer memory 7 is replaced with the error data pattern immediately after being read, even if the demodulated data block has an error and is not written in the memory 7, it is read in the past. The voice data thus created does not remain and is not transferred to the D / A converter 9 in a duplicated manner. Then, the replaced data has an error pattern, and thus is error-corrected by the error correction circuit 8.

In the conventional device configured as described above, since the content of the memory is replaced with the error pattern after the reading, the device having a configuration in which the information storage memory is shared when writing information to the recording medium and reading information from the recording medium. In the case of the first read operation after writing to the recording medium,
If the information written to the recording medium immediately before, that is, the correctable data pattern remains in the memory, and the reading from the recording medium is not completed completely, the remaining information is processed as the read information. There is a drawback that it may be.

SUMMARY OF THE INVENTION The present invention has been made to eliminate the above-mentioned drawbacks of the conventional ones, and in reading information from a recording medium,
It is an object of the present invention to provide a method of reproducing digital data in which information written immediately before to a recording medium is not processed as read information or information read from a recording medium is not redundantly processed. To aim.

The method for reproducing digital data according to the present invention performs error correction using a Reed-Solomon code as an error correction code while writing demodulated digital data obtained by demodulating digital information read from a recording medium into a memory and then reading the data. A method of reproducing digital data, wherein a pattern setting step of setting the content of the memory into a predetermined data pattern in which error correction is impossible, and the demodulated digital data in the memory after the setting processing by the pattern setting step is completed. It consists of a writing process of writing.

Example Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention.
In the drawing, when writing to the recording medium 10, the buffer memory 1 is externally passed through the interface circuit 11.
The digital information is stored in 2, the signal processing circuit 13 adds the parity, and the digital information and the parity are transferred to the modulation / demodulation circuit 14. Then, the demodulation section of the modulation / demodulation circuit 14 adds the error detection code and records it on the recording medium 10.

On the other hand, when reading information from the recording medium 10,
At the time of reading, before the information read from the recording medium 10 is transferred to the buffer memory 12 via the modulation section of the modulation / demodulation circuit 14, the signal processing circuit 13 causes the contents of the buffer memory 12 to be other than [00]. The same fixed pattern, for example, all are set to [FF]. The same fixed patterns other than [00] are patterns that cannot be corrected. After setting the contents of the buffer memory 12 to the same fixed pattern other than [00], the information read from the recording medium 10 is put into the buffer memory 12.

Here, it will be described below that the same data pattern other than the above [00] cannot be corrected.

In a Reed-Solomon code of code length n, a generator polynomial G
If (x) is G (x) = (x + 1) (x + α), then the parity check matrix H is Becomes Transmission code W = (W ₀ , W ₁ , ... Wn _-3 ,
P, Q), the parities P and Q are defined to satisfy HW ^T = 0. On the other hand, the reception code W'becomes the transmission code W to which the error e is added, and W '= W + e. The received code W ′ is decoded by the parity check matrix H, and at this time, if the syndrome S is defined as S = HW ′ ^T = HW ^T + He ^T , 1) When the received code W ′ has no error, that is, e = 0 , S = HW ′ ^T = HW ^T + He = 0. Therefore, for the received code When, it is judged that there is no error.

2) There is a single error in the i'th code of W ', that is, Wi' = Wi + ei, or E = (0 ... ei ...
0), Becomes Therefore, the error position is obtained by S ₁ / S ₀ = α ⁱ , and the magnitude of the error is S ₀ itself.
Therefore, the error is corrected by setting Wi '+ S ₀ = Wi.

3) There is an error in the ith and jth positions of W ', that is, in the case of, Becomes that time, In the case of, S ₁ / S ₀ = α ^k and K (0 ≦ K ≦ 2 ^n-1 )
On the other hand, when 0 ≦ K ≦ n−1, it is erroneously corrected as a single error, and when n ≦ K ≦ 2 ⁿ⁻¹ , it is judged to be two or more errors and cannot be corrected.

on the other hand, In the case of, it becomes uncorrectable as two or more errors.

Here, in the embodiment of the present invention, the buffer memory 12
When the content of is set to the same arbitrary data We, the decoding process is performed as W '= (WeWe ... We) (We ≠ 0). Syndromes S ₀ and S ₁ are Becomes When the code length n is an even number, S ₀ = 0, while for S ₁ , Galois field GF (2 ^m )
It has been proved above that S ≠ 0 in the range of n <2 ^m −1.

(Proof) The primitive polynomial F (x) in GF (2 ^m ) is a polynomial Is a factor of. That is, Is represented. on the other hand, Is represented. If the primitive element of F (x) is α, then F
Since (α) = 0, Becomes Since α + 1 ≠ 0, Is. Here, if l that satisfies α ^l + α ^l−1 + ... + α + 1 = 0 exists in the range of l <2 ^m −2, f ′ (x) = (x + 1) (x ^l + x ^l-1 + ... + x +
1) = x ^{l + 1} +1, it must be f '(α) = α ^{l + 1} + 1 = 0 (where l + 1 <2 ^m -1). However, the element α ⁱ of GF (2 ^m )
Circulates i modulo 2 ^m −1, so l + 1
In the range <2 ^m -1, α ^{1 + 1} ≠ 1, which is a contradiction. Therefore, The above polynomial becomes 0 only when l = 2 ^m −2.

Therefore, the syndromes S ₀ and S ₁ are GF
On (2 ^m ), if the code length n is an even number in the range of n <2 ^m −1, Becomes

As is clear from the above proof, when the same data pattern W = (We ... ... We) (We ≠ 0) with an accidental code length is decoded, S ₀ = 0, S ₁ ≠ 0, and the correction is uncorrected. It will be possible.

Next, the operation at the time of reading information in the digital data recording / reproducing apparatus according to the present invention will be described with reference to the flowchart of FIG.

First, when reading information from the recording medium 10, the contents of the buffer memory 12 are set to the same data pattern (≠ 0) (step 10). Then, the signal read from the recording medium 10 is demodulated by the demodulation section of the modulation / demodulation circuit 14 (step 11), and it is determined whether or not the block sync code is detected in step 12, and if it is detected, the buffer memory is detected. Data is written to 12 (step 13).

Subsequently, it is determined in step 14 whether or not the reading of all blocks is completed, and if not completed, the process returns to step 11. When all blocks have been read, it is determined whether or not a data error has been detected (step 15). If an error has been detected, then it is determined whether or not correction is possible (step 16). ). If the correction is possible, the error is corrected (step 17) and the data is output (step 18). If it is determined in step 16 that the correction is not possible, error information is output (step 1
9). If it is determined in step 12 that the block sync signal is not detected, the process proceeds to step 14, and if it is determined in step 15 that no data error is detected, the process proceeds to step 18.

As described above, according to the digital data recording / reproducing apparatus of the present invention, the contents of the buffer memory are set to the same data pattern, that is, uncorrectable data, before reading the information from the recording medium. Since it has become
Even if the information was not written to the memory because the reading from the recording medium was incomplete, the information that was previously read from the recording medium does not remain in the memory. Therefore, this residual information is output again. It can be prevented. In addition, at this time, although the uncorrectable data is still stored in the memory, the error correction circuit cannot correct the data, so that the information read from the recording medium is incomplete. Will not be processed as normal information. Furthermore, since the uncorrectable data described above is one fixed data pattern, it can be generated with a simple circuit configuration.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a flow chart for explaining the operation at the time of reading information in the circuit of FIG. 1, FIG. 3 is a block diagram showing a conventional example, and FIG. The figure is a flow chart for explaining the operation at the time of reading information in the circuit of FIG. Description of symbols of main parts 2, 12 ... Buffer memory 5, 10 ... Recording medium 13 ... Signal processing circuit 14 ... Modulation / demodulation circuit

Claims (2)

[Claims] 1. A method of reproducing digital data in which error correction is performed by using a Reed-Solomon code as an error correction code while writing demodulated digital data obtained by demodulating digital information read from a recording medium into a memory and then reading the same. There is a pattern setting process of setting the content of the memory into a predetermined data pattern in which error correction is impossible, and a writing process of writing the demodulated digital data into the memory after the setting process by the pattern setting process is completed. A method for reproducing digital data, characterized in that 2. The method for reproducing digital data according to claim 1, wherein the predetermined data pattern is a fixed pattern other than [00].