JPH05114251A - Error correcting method - Google Patents

Abstract

PURPOSE:To provide an error correcting method by which the capacity of a memory required for making error correction can be reduced by performing the correction under a highly efficiently encoded state and variable length codes are not much deteriorated so that the codes can be properly decoded even after the codes are corrected. CONSTITUTION:Highly efficiently encoded data A and B which can be decoded independently from each other are inserted into three recording blocks after division. By superimposing the address information indicating the punctuation of the inserted data A and B upon a recording unit constituted of the three recording blocks, an error which is produced at the time of reproduction is corrected at the time of recording. The information indicating the data constitution of the corresponding recording unit on the current or the preceding page is selectively adopted as the information indicating the data constitution after correction in accordance with the position of the error. In addition, by detecting an address difference by comparing the address information of the recording unit on the current page and the address information of the corresponding recording unit on the preceding page, the correcting method of the error is decided in accordance with the detected difference.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an error correction method during reproduction in a digital recording / reproducing apparatus.

[0002]

2. Description of the Related Art In a digital recording / reproducing apparatus, an error generated during reproduction is corrected based on an error correction check symbol added during recording, and an error is corrected for uncorrectable data. The configuration and operation of the digital recording / reproducing apparatus and the error correction method will be described below.

FIG. 11 is a diagram showing the configuration of a conventional digital recording / reproducing apparatus. In FIG. 11, 1 is an input terminal,
Reference numeral 2 is an A / D converter for converting an input signal into digital data, 3 is a high efficiency encoder, 4 is an error correction encoder for adding a check symbol for error correction, and 5 is an interleave memory for rearranging the order of input data. 6 is a recording processing circuit,
Reference numeral 7 is a recording head. Next, 8 is a reproduction head, 9 is a reproduction processing circuit, 10 is a deinterleave memory for restoring the order of the data rearranged at the time of recording, and 11 is based on the error correction inspection symbol added at the time of recording. An error correction decoder for correcting and detecting an error in the reproduced data, 12 is an error flag for indicating the existence of an error,
Reference numeral 13 is an error correction circuit for correcting an error that cannot be corrected by the error correction decoder 10 based on the error flag 12, 13 is a D / A converter, and 14 is an output terminal.
The operation will be described below.

First, at the time of recording, the analog signal input from the terminal 1 is converted into digital data by the A / D converter 2 and the data amount is reduced to a predetermined data amount by the high efficiency encoder 3 and then error correction is performed. The encoder 4 adds a check symbol for error correction. At this time, the order of the data input in the interleave memory 5 is rearranged in order to prevent continuous errors due to dropout during reproduction. Finally, the recording processing circuit 6 performs the necessary processing for recording to perform recording.

Next, at the time of reproduction, the data reproduced from the reproducing head 8 is input to the error correction decoder 10 via the reproduction processing circuit 9. The error correction decoder 10 corrects the error of the reproduction signal based on the error correction check symbol added at the time of recording, and when an error exceeding the correction capability occurs, an error flag 11 indicating the existence of the error follows. It is transmitted to the error correction circuit 13. At this time, in order to restore the order of the data rearranged at the time of recording, the reverse interleaving memory 9 performs the reverse rearrangement processing. Next, the data encoded by the high-efficiency decoder 12 is decoded, but if there is an error in the data that cannot be corrected by the error correction decoder 10, the data is erroneously decoded, and therefore, the error is erroneous. Then, the error correction circuit 13 performs data correction on the decoded data. Hereinafter, error correction when orthogonal transform and variable length coding are used as a high efficiency coding method will be described.

FIG. 12 is a diagram specifically showing the configurations of the high-efficiency encoder 3 and the high-efficiency decoder 12. 100 is a blocker, 101 is an orthogonal transformer, 102 is an encoder, and 1 is a block diagram.
Reference numeral 04 is a decoder, 105 is an inverse orthogonal transformer, and 106 is an inverse blocker. First, at the time of encoding, the blocker 10
At 0, a predetermined number of input data are collected and divided into blocks, and the encoder 103 which has been transformed by the orthogonal transformer 101 is encoded. Next, at the time of reproduction, decoding is performed by the decoder 104, inverse transformation is performed by the inverse orthogonal transformer 105, and then the blocked data is restored to the original data by the deblocking unit 106.
Here, if there is an error in the reproduced data, the influence of the error spreads over the entire block by decoding, so the error correction circuit 13 must correct all the data in one block. In this case, since it is difficult to perform correction by interpolation using data in the vicinity, the correction is usually realized by substituting using the data of the corresponding block before one field or a plurality of fields (hereinafter referred to as one page).

[0007]

However, the above-mentioned error correction method has the following problems.

The error correction of the image signal is realized by a method of interpolating error data from neighboring data or replacing it with data of one page before. When high efficiency coding in block units such as orthogonal transformation is used here, it is difficult to perform correction by interpolation from neighboring data because the influence of one error spreads over the entire block, and as described above. The modification is performed by replacing with the data of the corresponding block one page before. However, for that purpose, a large-scale memory of one page or more is required for modification after decryption. Further, when variable length coding that is completed in a plurality of blocks is used as an encoding method, the word synchronization of the variable length code is lost due to an error at the time of decoding, and the influence of the error spreads to a plurality of blocks. All blocks must be modified.

On the other hand, when the modification is performed in the high-efficiency coded state, when the modified data is decoded, it is necessary to perform the modification so that the variable length code can be correctly decoded.

The present invention solves the above-mentioned problems of the prior art by reducing the memory capacity required for the correction by performing the correction in a highly efficient coded state, and the deterioration due to the correction is small, and even after the correction. An object is to provide an error correction method capable of correctly decoding a variable length code.

[0011]

According to a first aspect of the present invention, an input sampled value is divided into blocks, and m blocks are collected from one page in a unit of one field or a plurality of fields and independently coded with high efficiency. When dividing the data A and B into the three recording blocks X, Y, and Z and inserting them, the data corresponding to mainly the low frequency component of the m blocks of the data A is transferred to the recording block X. Data corresponding to the low frequency component of the m blocks of the data B is inserted into the recording block Y, and data corresponding to the high frequency component of the block of the data A and B corresponds to the high frequency component. Data to be recorded in the recording block Z, and the address information indicating the delimiter of the inserted data A and B is multiplexed in the recording unit to record an error during reproduction, Present Information or the showing the configuration of a data recording unit of the current page in accordance with the error position of the over-di 1
An error correction method characterized in that information indicating a data structure of a corresponding recording unit before a page is selectively adopted as information indicating a data structure after correction.

A second aspect of the present invention is that the input sample values are divided into blocks, and m pieces of each of the blocks are collected from one page having one field or a plurality of fields as a unit, and the data A and B independently coded with high efficiency are obtained. 3 recording blocks X,
When dividing and inserting into Y and Z, data corresponding to mainly low frequency components of the m blocks of the data A are inserted into the recording block X, and the m blocks of the data B are Data corresponding to mainly low-frequency components of a block is inserted into the recording block Y, and data corresponding to mainly high-frequency components of the block of the data A and B is inserted into the recording block Z and inserted. A method of correcting an error at the time of reproduction when the address information indicating the delimiter between the data A and B is multiplexed and recorded in the recording unit,
Comparing address information in the recording unit of the current page with address information of the corresponding recording unit one page before the current page, detecting an address difference, and determining a retouching method according to the detected difference. Is an error correction method characterized by.

[0013]

According to the first aspect of the present invention, the highly efficient coded data A and B which can be independently decoded are divided into three recording blocks X, Y and Z and inserted. The address information indicating the delimiter between the data A and B is described in the above 3
A method of correcting an error at the time of reproduction when recording is performed by multiplexing in a recording unit composed of individual recording blocks,
Information indicating the data structure of the recording unit of the current page or the information indicating the data structure of the corresponding recording unit of the preceding page of the current page according to the error position of the current page. Is selectively adopted as and is modified into a form that can be correctly decoded by high-efficiency decoding.

The second aspect of the present invention has the above-mentioned structure.
A method of correcting an error during reproduction of the recording unit recorded by the same method, wherein address information of the recording unit of the current page is compared with address information of a corresponding recording unit one page before the current page. Then, the address difference is detected, and the retouching method is determined according to the detected difference.

[0015]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

First, the data structure of one recording unit consisting of three recording blocks is shown. FIG. 1 is a diagram showing a method of configuring three recording blocks X, Y, Z and a data configuration. The input image signal is divided into blocks, and the data A and B obtained by collecting m blocks each for high efficiency encoding are shown. It is divided into three recording blocks X, Y and Z and inserted. Here, orthogonal transformation and variable length coding are used as the high-efficiency coding method.
That is, the blocked data is decomposed into frequency components by orthogonal transformation, and variable length coding is performed in order from the low frequency component. Therefore, although the data amount of A and B differs depending on the information amount of each block, the total data amount of A and B is coded so as to be a constant data amount corresponding to three recording blocks. Is controlled.

When actually inserting data into a recording block, first, data corresponding to the low frequency components of m blocks from the data A is inserted into the recording block X, and similarly from the data string B, m. Data corresponding to the low-frequency component of each block is inserted into the recording block Y. Let these be AL and BL, respectively. Next, of the data A and B, the data that could not be inserted into the recording blocks X and Y, that is, the data AH and BH corresponding to the high frequency components of each block are inserted into the recording block Z, respectively. Here, the recording block Z is A
Since it is composed of H and BH, address information (AD) is added to a predetermined position of the recording block Z so that the position of the delimiter of AH and BH can be known at the time of decoding. Address information is A
Addresses separated by H and BH are shown. At the time of decoding, AH and BH are discriminated based on the AD of the recording block Z, and
Combine with L and BL to make a double sign.

Next, an error correction method at the time of reproduction when recorded by the above method will be described. In the description, it is assumed that the current page in which the error has occurred is n + 1 page.

FIG. 2 shows a first error correction method according to the present invention.
It is a figure showing an example of. In this embodiment, the error exists in the recording block X. Therefore, only the data A is modified and the data B is not modified. That is, as shown in FIG. 2, the AL n _{+ 1} of the recording block X _{n + 1} replaced by AL _n recording blocks X _n, the AH n _{+ 1} of the recording block Z _{n + 1} in AH _n recording blocks Z _n replace. Here, although the ADs of the nth page and the n + 1th page are different, the address ADn _{+ 1} of the current page is adopted as the address information after the modification. In this case, as shown in FIG. 2, both A _n and B _n exist before AD _{n + 1} in the modified recording block Z. However, when decoding a variable length code, E _n
A _n by counting the number of OB (End Of Block)
The end of the can be detected, so no problems occur during decoding.

FIG. 3 shows a first error correction method according to the present invention.
FIG. 6 is a diagram showing a case of another data configuration in the example of FIG.
It In FIG. 3, an error is recorded as in the embodiment of FIG.
Exists in the X and A_{n + 1}Modify only but the data
The configuration is different from that of FIG. Therefore, the recording block
Z_{n + 1}At the address AD of the current page_{n + 1}Up to AH _n
When replaced with, the shaded area in FIG. 3, ie, A
H_nA part of the high frequency component of will be lost. But
However, the information that is lost is the high-frequency component in the original block.
Therefore, the image quality after modification does not deteriorate significantly.

As described above, according to this embodiment, when the error occurs in the data A, the address information of the current page is adopted as the address information after the correction,
Since the data A and B after modification can be respectively decoded, and the number of data modified is smaller than that in the case where both data A and B are modified, deterioration of image quality due to modification is less noticeable.

FIG. 4 shows a second error correction method according to the present invention.
It is a figure showing an example of. In this embodiment, the error exists in the recording block Y, and the data B is reversed, contrary to the first embodiment.
Modify only. That is, as shown in FIG. 4, the BL n _{+ 1} of the recording block Y _{n + 1} replaced by BL _n recording blocks Y _n, the BH n _{+ 1} of the recording block Z _{n + 1} in BH _n recording blocks Z _n replace. Here, n pages and n + 1 pages of AD are different, as the address information after modification, employing the addresses AD _n before one page. In this case, as shown in FIG. 4, in the recording block Z after modification, both A _{n + 1} and B _{n + 1} exist before AD _n after modification, but as in the case of FIG. , EOB when decoding variable length code
Since the end of A _{n + 1} can be detected by counting the number of A, no problem occurs during decoding.

FIG. 5 shows a second error correction method according to the present invention.
FIG. 7 is a diagram showing a case of another data configuration in the embodiment of FIG. In FIG. 5, the error exists in the recording block Y as in the embodiment of FIG. 3 and only B _{n + 1} is modified, but the data structure is different from that in FIG. Therefore, in the recording block Z _{n + 1} , the address AD _n after the previous page is B
When it is replaced with H _n , a part shown by hatching in FIG. 5, that is, a part of the high frequency component of AH _{n + 1} is lost. However, since the information to be lost is a high frequency component in the original block, the image quality after modification does not significantly deteriorate.

As described above, according to the present embodiment, when the error occurs in the data B, the address information of the previous page is adopted as the address information after the correction, so that the data A and B after the correction can be obtained. Since the number of data that can be decoded is smaller and the number of data to be modified is smaller than that when both data A and B are modified, deterioration in image quality due to modification is less noticeable.

FIG. 6 shows a third error correction method according to the present invention.
It is a figure showing an example of. In Figure 6, the error is noted.
It exists in the recording block Z and the position of the error is unknown.
It Therefore, the error exists in either data A or B.
It is unknown whether or not the data A or B
Since it is impossible to modify only the recording block X
_{n + 1}, Y_{n + 1}, Z_{n + 1}All recording blocks X_n, Y_n, Z_nso
replace. Of course, the address information for the previous page
Of is used.

Next, a specific configuration for realizing the above-described error correction method will be described. FIG. 7 is a block diagram of a retouching device for realizing the error retouching method according to the first invention. In FIG. 7, reference numeral 200 is a memory having a capacity of two pages, and 201 is whether or not each recording block has an error. A flag memory for a flag indicating whether or not, 202 is an error detector that detects an error of a recording unit, 203 is an address information detector that detects address information (AD) of the recording unit, and 204 is address information of the recording unit of the current page. (AD
_{n + 1} ), 205 is address information (AD _n ) of the corresponding recording unit one page before, 206 is a retouching method determiner that determines the retouching method based on the detection results of the error detector 202 and the address information detector 203. , 207 are reading controllers for controlling reading of the memory 200.

Since the memory 200 has a capacity of two pages, it is composed of two areas each for one page. One area is written with the data of the current page whose error has been corrected, and the other area is written with 1 area. The data before the page is written. In modifying the data of the current page, the error detector 202 first detects a recording block in which an error exists in the recording unit of the current page. Next, the address information detector 203 detects the address information multiplexed in the recording block Z for each of the current page and the previous page. The position and address information of the error detected by each of the above detectors is input to the retouching method determiner 206 to determine the retouching method, and the retrieving controller 207 controls the current page if retouching is not performed. When data is read from the memory area and correction is performed, the data is read from the memory area one page before.

FIG. 8 is a diagram showing an embodiment of the error correction method according to the second invention. In this embodiment, an error exists in the recording block X, but the correction method is determined by comparing the address information of the corresponding recording unit of the current page and the preceding page. That is, as shown in FIG. 8A, when the difference between the address of the current page and the address of the previous page is small, the amount of loss of the high-frequency component data of AH _n indicated by the diagonal lines in the figure is small. Therefore, only data A is modified. next,
As shown in FIG. 8B, when the difference between the address of the current page and the address of the previous page is large, if only the data A is corrected, the data of the high frequency component of AH _n indicated by the diagonal line in the figure is lost. Both the data A and B are modified because the amount of exposure is large and there is a high possibility that image quality deterioration will occur.

FIG. 9 is a diagram showing a structure for realizing the error correction method according to the second invention. The basic structure is the same as the structure shown in FIG. An address comparator 300 is added to compare the address information with the address information of the corresponding recording unit one page before. The address comparator 300 compares the address information (AD _{n + 1} ) 204 of the recording unit of the current page with the address information (AD _n ) 205 of the corresponding recording unit of the previous page,
The address difference is output to the retouching method determiner 207. The modification method determiner 207 switches the modification method based on the comparison result of the address comparator 300 and a predetermined threshold value.

As described above, according to the present embodiment, the high frequency component lost when only one of the data A and the data B is modified is reduced, and the deterioration of the image quality due to the modification can be suppressed. is there.

Although the modification method has been described above, in order to know whether or not the recording unit of interest has been modified in the past, when an error modification is performed, the modification is made to the modified recording unit. It is possible to add the information (retouching information) indicating to each sync block and use the retouching information as a judgment item for a new retouching.

FIG. 10 is a diagram showing an embodiment of a retouching method using the retouching information, in which the recording unit of the current page has already been retouched. In this embodiment, since the error exists in the recording block X, normally, only the data A is modified and the data B is not modified. However, since the recording unit of the current page has been modified in the past,
There is a possibility that the high frequency component has already been lost in the recording block Z _{n + 1} . That is, if only the data A is modified for the current page, the high frequency components that are lost further increase, and there is a possibility that the image quality will be deteriorated to be visible. Therefore, when the current page or the previous page is already modified in the past, as shown in FIG. 10, all the data of one recording unit is modified regardless of the position of the error and the structure of the recording unit.

In the above example, the case where the recording block Z is composed of both data A and B is taken up, but when the data amount of A and B is significantly different, for example, B
Is smaller than the data amount that can be inserted into the recording block Y, a part of the data of A is inserted into the remaining area of the recording block Y, and the recording block Z is composed of all A data. become. In this case, it is difficult to modify only one of the data A and B, and all the data of one recording unit will be modified.

[0034]

As described above, according to the present invention, since the error correction is performed in the high-efficiency coded state, the memory capacity required for the correction is small, and one recording unit is not always corrected. Depending on the structure of encoded data, only the data that is erroneous at the time of decoding can be modified, and it can be erroneously decoded at the time of highly efficient decoding, so the image quality deterioration due to modification is small and its practical effect is large. ..

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a configuration method and a data configuration of three recording blocks X, Y, and Z.

FIG. 2 is an explanatory diagram of a first embodiment of an error correction method according to the first invention.

FIG. 3 is an explanatory diagram in the case of another data structure in the first embodiment of the error correction method according to the first invention.

FIG. 4 is an explanatory diagram of a second embodiment of the error correction method according to the first invention.

FIG. 5 is an explanatory diagram in the case of another data structure in the second embodiment of the error correction method according to the first invention.

FIG. 6 is an explanatory diagram of a third embodiment of the error correction method according to the first invention.

FIG. 7 is a block diagram of a configuration for realizing the error correction method according to the first invention.

FIG. 8 is an explanatory diagram of an embodiment of an error correction method according to the second invention.

FIG. 9 is a block diagram of a configuration for realizing an error correction method according to a second invention.

FIG. 10 is an explanatory diagram of an embodiment of a modification method using modification information.

FIG. 11 is a block diagram of a conventional digital recording / reproducing apparatus.

FIG. 12 is a specific block diagram of the configurations of a high-efficiency encoder 3 and a high-efficiency decoder 12.

[Explanation of symbols]

 200 memory 201 flag memory 202 error detector 203 address information detector 206 retouching method determiner 207 read controller 300 address comparator

Claims (4)

[Claims] 1. An input sample value is divided into blocks, and m pieces of each block are collected from one page of one field or a plurality of fields as a unit, and three data A and B independently independently encoded for high efficiency recording are recorded. When dividing and inserting into blocks X, Y, and Z, data corresponding to mainly low-frequency components of the m blocks of the data A is inserted into the recording block X, and the data of the data B is Data corresponding to mainly low frequency components of m blocks are inserted into the recording block Y, and data corresponding to mainly high frequency components of the blocks of the data A and B are inserted into the recording block Z. , A method of correcting an error at the time of reproduction when the address information indicating the delimiter between the inserted data A and B is multiplexed in the recording unit for recording, and the error is corrected according to the error position of the current page. Error correction characterized by selectively using information indicating the data structure of the recording unit of the page or information indicating the data structure of the corresponding recording unit of the preceding page as the information indicating the data structure after modification Method. 2. The data A and B independently recorded with high efficiency by collecting m pieces of each block from one page in which the input sample value is divided into blocks and one field or a plurality of fields as a unit are recorded. When dividing and inserting into blocks X, Y, and Z, data corresponding to mainly low-frequency components of the m blocks of the data A is inserted into the recording block X, and the data of the data B is Data corresponding to mainly low frequency components of m blocks are inserted into the recording block Y, and data corresponding to mainly high frequency components of the blocks of the data A and B are inserted into the recording block Z. A method of correcting an error at the time of reproduction when the address information indicating the delimiter between the inserted data A and B is multiplexed in the recording unit and recording is performed. Error correction method, characterized in that the address information is detected by comparing the address information of the corresponding recording unit one page before the current page with the address information, and the correction method is determined according to the detected difference. .. 3. If there is an error in a recording block including information indicating the data structure among the recording units of the previous current page, all the recording units of the previous current page are the corresponding recording units of the preceding page. Data A, B by replacing
3. The error correction method according to claim 1, wherein both are corrected. 4. When the recording unit of the previous current page or the corresponding recording unit of the previous page of the current page is composed of already modified data, all the recording units of the previous current page are set to the one page. 3. The error correction method according to claim 1, wherein the data A and B are both modified by replacing them with the corresponding corresponding recording unit.