JPH08249832A - Digital signal recording/reproducing device - Google Patents

Abstract

PURPOSE: To prevent the reproduction from being disturbed even when errors increase while reproducing rather than while recording. CONSTITUTION: The recording data are supplied to an encoder 2 through a terminal 1. The data added with a code for correcting the errors up to 2N word by the encoder 2 and encoded are supplied to a head 4 through an amplifier 3 and recorded on a recording medium 5. The data are read after write. The data are reproduced by the head 6 and supplied to a decoder 8 having error correction capability of 2N word through the amplifier 7. The error correction capability of the decoder 8 is made until N word by a signal 11 from a correction power switch circuit 10. When the errors exceeding the N word are contained in the supplied reproducing data, the data are recorded again. At a reproducing time, the error correction capability of the decoder 8 is made up to 2N word. Thus, even when the errors in the recorded data are increased, the data are reproduced with a margin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention records an encoded digital signal to which an error correction code has been added on a recording medium, and when it is detected that the error is larger than a predetermined amount when the digital signal is recorded. , A digital signal recording / reproducing apparatus for performing rewriting processing.

[0002]

2. Description of the Related Art When digital data is recorded on a recording medium such as a magnetic tape or a magnetic disk, the data is usually encoded by an error correction code, for example, a Reed-Solomon code. Error correction is performed by decoding. Also,
When such recording is performed for the purpose of preservation, for example, recording by a data recorder or the like, it is necessary to leave a medium in a recording state as good as possible.

For example, in the case of the Reed-Solomon code, at the time of error correction, the syndrome is first calculated, and how many bytes of error are detected using this syndrome. If this error can be corrected, The position of the error byte and the value of the error are obtained, and the error is corrected.

FIG. 8 schematically shows an example of the configuration of a conventional digital signal recording / reproducing apparatus in which such error correction is performed. When recording data, first
Digital data for recording is supplied to the encoder 100. The recording data supplied to the encoder 100 is coded with an error correction code added, for example, by the Reed-Solomon code. The encoded recording data is supplied to the recording head 102 via the recording amplifier 101 and recorded on the recording medium 103 such as a magnetic tape.

The recording data recorded on the recording medium 103 is read by the reproducing head 104 immediately after recording.
This is to check whether the recording was done correctly. Read After Write
Is called. The recording data read by the reproducing head 104 is supplied to the decoder 106 via the reproducing amplifier 105. The recording data supplied to the decoder 106 is error-corrected by the error correction code and decoded.

At this time, even if an error is included in the read-after-write reproduced signal, it is considered that the correct recording is possible within a range that can be corrected by the error correction code. For example, if this error correction code is a Reed-Solomon code and 2N bytes are assigned to the parity, it is considered that the correct recording was possible even if the reproduced signal contained up to N bytes of errors. If the error is N
If the number of bytes exceeds the correction capability of the error correction code, it is determined that the data has not been correctly recorded, and a retry process is performed to record the same data again.

During normal reproduction of data, reproduction data is read from the recording medium 103 by the reproduction head 104 and supplied to the decoder 106 via the reproduction amplifier 105. The reproduced data supplied to the decoder 106 is error-corrected by the error-correcting code decoding process and output.

[0008]

As described above, when the error correction is performed by the error correction code, it is considered that the recording is normally performed even if the maximum error that can be corrected occurs at the time of recording. . Therefore, when an error is newly added to this recording medium, even one byte, the number of errors exceeds the error correction capability. As a result, the data in that portion cannot be reproduced again. In particular, general digital data such as computer data cannot be corrected for errors by interpolation, and even if there is a 1-byte uncorrectable error, the entire data including such data cannot be used. I can not do it. That is,
There has been a problem that a recording medium that cannot be reproduced easily occurs due to changes over time.

Therefore, an object of the present invention is to provide a digital data recording / reproducing apparatus which does not hinder the reproduction even if the number of errors during reproduction is larger than that during recording.

[0010]

In order to solve the above-mentioned problems, the present invention provides a digital signal recording / reproducing apparatus which records a digital signal by performing coding capable of correcting N symbol errors. Therefore, the present invention is a digital signal recording / reproducing apparatus characterized in that an error of less than N symbols is corrected during an operation of immediately reproducing a recorded digital signal, and a write operation is performed again when the error cannot be corrected. .

Further, according to the present invention, in order to solve the above-mentioned problems, the recorded digital data is read by:
A digital signal recording / reproducing apparatus comprising a decoding unit of an error correction unit adapted to correct an error up to N symbols.

[0012]

According to the present invention, even if it has the capability of N symbols, error correction of less than N symbols is performed at the time of read-after-write. Can be performed and data can be reproduced.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings. In the first embodiment, in a digital signal recording / reproducing apparatus having an error correction capability of 2N words at the maximum, an error correction of less than N words is performed during recording, and an error correction of 2N words is performed during reproduction.

FIG. 1 schematically shows an example of the structure of such a data recorder. Further, FIG. 2 shows a flowchart of processing when recording a digital signal with this configuration. The digital recording data supplied to the input terminal 1 is supplied to the encoder 2 of the error correction code, encoded by, for example, the Reed-Solomon code, and the error correction code having the ability to correct an error of 2N words is added. . This encoded recording data is recorded by the recording amplifier 3
Predetermined signal processing is performed via, and the signal is supplied to the recording head 4 and recorded in the storage medium 5 (step S1).

The recording data recorded on the recording medium 5 is immediately read by the reproducing head 6 and read-after-written (step S2). This reproduced data that has been read out is passed through a reproduction amplifier 7 to a decoder 8 for error correction code.
Is supplied to. This decoder 8 performs error correction. The decoder 8 corresponds to the error correction capability of the encoder 2 and has the capability of correcting errors up to 2N words. A switching signal 11 is supplied from the correction capability switching circuit 10 to the decoder 8 and the correction capability can be switched by the switching signal 11. For example, the error correction capability is switched between 2N words and N words.

At the time of read / write, the switching signal 11 switches the decoder 8 to one having a lower error correction capability, that is, a decoder capable of correcting up to 2N words and capable of correcting up to N words. To be
Thus, N of the reproduction data supplied to the decoder 8
The error up to the word is corrected (step S3). As a method of switching the error correction capability of the decoder 8, it is detected how many words there are errors in this reproduction data, and when the number of these errors exceeds N words, this decoder 8 cannot perform error correction. It is said that Then, in order to perform re-recording (retry), the process returns to step S1 described above. Therefore, at the time of recording, there are only errors up to N words in this recording data.

If the number of errors in the reproduced data is smaller than N words, error correction is possible. In this case, the data recording process ends and the next data is recorded.

When the data on the recording medium 5 is reproduced, the decoder 8 has the maximum error correction capability by the switching signal 11, that is, is capable of correcting errors up to 2N words. As described above, at the time of recording, the data error of the recording medium 5 is N words or less. Therefore, even if the data error increases to some extent due to the storage condition of the tape, a change over time, or deterioration due to a large number of runs, the error can be corrected. In this example, since the error correction capability of the decoder 8 is up to 2N words, it is possible to correct even if the data error increases by N words.

As described above, by performing the recording while reducing the correction capability during data recording, it is possible to perform reliable recording with a margin at the time of reproduction against changes over time or damage to the recording medium due to a large number of runs. It is possible to leave.

Next, a second embodiment of the present invention will be described with reference to the drawings. This is an example in which the present invention is applied to a digital signal recording / reproducing apparatus (hereinafter referred to as a data recorder) in which digital data is recorded / reproduced on a cassette tape by a rotary head. Further, in this example, the Reed-Solomon code and the product code are used in combination with the error correction code.

FIG. 3 shows an example of use of this data recorder. In this way, the data recorder 20 and the host computer 21 are connected by the SCSI bus 22, and data and commands are exchanged between the data recorder 20 and the host computer 21 via the SCSI bus 22.

The data recorder 20 records / reproduces digital data on / from a cassette tape with a rotary head. FIG. 4 shows an example of the head arrangement of the data recorder 20. Four heads Ra, Rb, Rc for recording are provided on the drum 25 rotating at a predetermined speed in the direction shown in the figure.
And Rd and four heads Pa, Pb, Pc and Pd for reproduction are attached respectively.

The heads Ra and Rb are provided in close proximity to each other, and similarly, the heads Rc and Rd, the heads Pa and Pb, and the pair of heads Pc and Pd are provided in close proximity to each other. Further, the extension direction (called azimuth) of the gap between these two adjacent heads is different. Heads Ra facing each other at 180 ° intervals
And Rc has a first azimuth, similarly 180 °
Heads Rb and Rd facing each other at a distance of 2 have a second azimuth. The heads Pa and Pc have the first azimuth, and the heads Pb and Pd have the second azimuth. The different azimuths are used to prevent crosstalk between adjacent tracks. The two adjacent heads are actually realized as an integrally structured head called a double azimuth head.

A tape (for example, 1/2 inch width) pulled out from the cassette is obliquely wound around the peripheral surface of the drum 25 over an angular range slightly larger than 180 °. The tape is fed at a predetermined speed. Therefore, at the time of recording, in the first half of the period in which the drum 25 makes one rotation, the head Ra
And Rb scan the tape, and in the latter half, the heads Rc and Rd scan the tape. During playback, the head Pa
And Pb scan the tape, then heads Pc and Pd scan the tape.

FIG. 5 shows a track pattern on the tape of the data recorder 20. Longitudinal tracks are formed on the upper and lower sides of the tape in the width direction, and helical tracks are formed between them. A control signal is recorded on the upper longitudinal track 26, and a time code is recorded on the lower longitudinal track 27. The time code indicates the position of the tape in the longitudinal direction, and for example, SMPTE time code is used. With one rotation of the drum 25, the two heads Ra and Rb simultaneously form two helical tracks Ta and Tb.
The two heads Rc and Rd simultaneously form two helical tracks Tc and Td. It should be noted that each helical track is formed by separating the first half portion and the second half portion, and a tracking pilot signal recording area 28 is provided in the middle portion.

The SMPTE time code was developed for a video signal such as a VTR, and its minimum unit is a frame (1/30 second). As will be described later, the data recorder has four tracks Ta to Td shown in FIG.
Is a logical data unit of data (referred to as a track set) that handles recordable data. For example, in the case where 16 tracks correspond to one frame of a video signal, the lower digit (value of 0, 1, 2, or 3) of the digit of the frame of the time code is provided and the track set is set as a unit. It is necessary to use a time code (also referred to as an ID) to be used. In case of SMPTE time code,
Since the user data area is prepared, such a modification is possible.

When the data of the track set composed of these four tracks is subjected to error correction coding, the data is divided into a plurality of blocks, for example, eight blocks. Each of these blocks is encoded with the Reed-Solomon code and product code described above. The data of each product code block is distributed and recorded on four tracks. This is called track interleaving. By this track interleaving, it is possible to effectively correct data burst errors. In each product code block, the order of data is rearranged in units of a predetermined number of words. This is called word interleaving.

FIG. 6 schematically shows the structure of encoded data applied in this embodiment. This data structure corresponds to each divided product code block. In this example, the C2 code is, for example, (1
04, 77) Error correction coding is performed by the Reed-Solomon code. That is, the first 77 words of each column are the user data area, and the following 27 words are the C2 parity. In this case, there is an ability to correct an error of up to 13 words in the column direction.

Similarly, error correction coding is performed in the row direction as well. In this example, the C1 code is error correction coded by, for example, (211,192) Reed-Solomon code for 192 words in each row. It That is,
The first 192 words are the user data area, and the following 19 words are the C1 parity for this data area. In this case, there is an error correction capability of 9 words in the row direction. Also, for the C2 parity described above,
C1 parity is added in the row direction.

In the above code organization, the error correction is performed by alternately repeating the error correction in the row direction by the C1 code and the error correction by the C2 code. If the error position can be detected by another method, it is possible to correct an error of up to 27 words in the column direction and up to 19 words in the row direction.
This is called the pointer erasure method. In this embodiment, this pointer erasure method is applied, and C
An error in which one code is 19 words and C2 code is 27 words can be corrected.

FIG. 7 shows an example of the configuration of a signal processing system relating to data recording / reproduction in the system configuration of the data recorder 20. Digital data to be recorded is supplied to the C2 encoder 31 via the input terminal 30. This C2
Track interleave circuit 3 for encoder 31
2 is connected, and the track interleave circuit 32 has C
One encoder 33 is connected.

The C2 encoder 31 and the C1 encoder 33 perform error correction coding of the above-mentioned C1 code and C2 code on the recording data. In addition, recording / recording is performed by the track interleave circuit 32.
In order to enhance the ability to correct errors that occur during the reproduction process, the distribution of data to the tracks during recording is controlled and interleaving is performed in track units.

The recording data product-encoded and track-interleaved by the C2 encoder 31, the track interleave circuit 32, and the C1 encoder 33 are:
It is supplied to the word interleave circuit 34. The word interleaving circuit 34 interleaves in word units.

The record data interleaved in word units by the word interleave circuit 34 is S
It is supplied to the YNC addition circuit 35. When data is recorded on the tape, the SYNC block divided by the sync signal is used as a unit, so that the SYNC adding circuit 35 adds the block sync signal. The recording data to which the block synchronization signal is added is encoded and output to the recording heads Ra to Rd via the recording amplifier 36. Data is recorded on the magnetic tape 38 by the recording heads Ra to Rd. At this time, the recording amplifier 36 performs the processing of partial response class 4 (PR (1,0, -1)).

This data recorded on the magnetic tape 38 is read-after-written, and it is inspected whether or not an error has occurred during recording on the tape. That is,
Immediately after being recorded by the recording heads Ra to Rd, the recorded recording data is reproduced from the magnetic tape 37 by the reproducing heads Pa to Pd.

The reproduced data reproduced from the magnetic tape 37 by the reproducing heads Pa to Pd is reproduced by the reproducing amplifier 38.
Is supplied to the SYNC extraction circuit 39 via. The reproduction amplifier 38 includes an equalizer, a Viterbi decoder and the like. S
The reproduction data supplied to the YNC extraction circuit 39 is SYNC.
The C signal is removed and supplied to the word deinterleave circuit 40. Word deinterleave circuit 40
Then, the data interleaved in word units in the word interleave circuit 34 at the time of recording is restored. This restored data is supplied to the C1 decoder 41.

The reproduced signal supplied to the C1 decoder 41 is error-corrected in the row direction by the C1 code and supplied to the track deinterleave circuit 42. In the track deinterleave circuit 42, the data interleaved in track units in the track interleave circuit 32 during recording is correctly arranged, and the product code block is restored. The reproduced data whose data arrangement has been restored is supplied to the C2 decoder 43.

A switching signal 46 is also supplied from the correction capability switching circuit 45 to the C2 decoder 43. The switching signal 46 switches the error correction capability of the C2 decoder 43. In the case of reproduction in this read-after-write, the error correction capability of the C2 decoder 43 is lower than the maximum capability, for example, 1/3 of the maximum capability. Further, the error correction capability is maximized during normal reproduction of data.

As described above, as a device having a function capable of switching the error correction capability, a product such as L64712 manufactured by LSI Logic Co., which is an IC for error correction, which is already commercially available, can be used.

The reproduced data supplied to the C2 decoder 43 is error-corrected with a correction capacity that is ⅓ of the maximum error correction capacity. As described above, C2 parity has a correction capability of up to 27 words by the point erasure method. Therefore, in this C2 decoder 43, the error correction capability is stopped up to 9 words.

If the reproduced data supplied to the C2 decoder 43 has an error exceeding 9 words, it is determined that the error cannot be corrected. This result is transmitted to a system controller (not shown) for controlling the entire data recorder via the output terminal 44, and the re-recording (retry) process of the same data is started under the control of the system controller.

If the error contained in the reproduction data supplied to the C2 decoder 43 is 9 words or less, the error can be corrected. The result is transmitted to the system controller, and the writing process of the next recording data is started under the control of the system controller.

Of the parities attached to this data, the C1 code is more effective for random errors, and the C2 code is more effective for burst errors. Since uncorrectable errors are often caused by burst errors, switching of error correction capability is only performed for C2 codes in this second embodiment.

When the magnetic tape 37 on which the data is recorded in this way is reproduced next time, the error correction capability of the C2 decoder 43 is set to the maximum by the switching signal 46. By doing this, this second
In this embodiment, as in the case of the above-described first embodiment, even if the error increases from the time of recording due to the change of the magnetic tape over time or the damage of the medium due to a large number of runs, the data can be reproduced with a margin. be able to.

In the above description, a magnetic tape is used as a recording medium for recording data, but this is not limited to this example. For example, the present invention is a disk such as a magnetic disk. It is also applicable to a digital signal recording / reproducing device using a medium. This is also applicable to a recording medium such as a magneto-optical disk using a recording or reproducing method other than magnetism.

Further, in the above description, the Reed-Solomon code and the product code are used as the digital data encoding method, but the present invention is not limited to this example.
It is also applicable to other types of error correction coding methods.

[0047]

As described above, by using the present invention, errors may increase more than when data is recorded due to storage conditions, changes over time, damage to the recording medium due to multiple runs, and the like. Even so,
There is an effect that the data can be reproduced with a margin.

Moreover, when the digital signal recording / reproducing apparatus to which the present invention is applied is used for a backup or the like, it is possible to leave a highly reliable recording medium.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a configuration of a data recorder in a first embodiment.

FIG. 2 is a flowchart showing a digital data recording process in the first embodiment.

FIG. 3 is a schematic diagram illustrating a usage example of a data recorder according to a second embodiment.

FIG. 4 is a schematic diagram showing an example of a head arrangement of a data recorder.

FIG. 5 is a schematic diagram showing a track pattern on a tape of a data recorder.

FIG. 6 is a schematic diagram showing an example of a structure of encoded data in the second embodiment.

FIG. 7 is a diagram showing an example of the configuration of a signal processing system relating to data recording / reproduction, of the system configuration of the data recorder.

FIG. 8 is a diagram showing an example of a configuration of a digital signal recording / reproducing apparatus according to a conventional technique.

[Explanation of symbols]

 2 encoder 5 recording medium 8 decoder 10 correction capability switching circuit 11 switching signal 31 C2 encoder 37 magnetic tape 43 C2 decoder 45 correction capability switching circuit 46 switching signal

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Claims (2)

[Claims] 1. A digital signal recording / reproducing apparatus adapted to record a digital signal by performing encoding capable of correcting N symbol errors, during the operation of immediately reproducing the recorded digital signal.
A digital signal recording / reproducing apparatus characterized in that an error of less than N symbols is corrected and a write operation is performed again when the error cannot be corrected. 2. A digital signal recording / recording device according to claim 1.
In the reproducing apparatus, the digital signal recording / reproducing apparatus is characterized in that the read of the recorded digital data is provided with a decoding means of an error correction unit adapted to correct errors up to N symbols.