JPH0512813A - Digital data reproduction method and device - Google Patents

Abstract

(57) [Abstract] [Purpose] When reproducing the ID code, C1 error check is performed to improve the error detection capability. Also, during variable speed reproduction, the reproduction speed is checked, the inspection method is changed according to the reproduction speed, and even if the C1 error check is invalid, the ID code is detected by another method. [Structure] Acquiring reproduction speed information, error checking by parity for ID code according to the speed,
The ID is detected by one of C1 parity error detection, match / majority error check, or a combination thereof.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary head type magnetic recording / reproducing apparatus for detecting an ID code included in reproduced data,
The present invention relates to a processing method and apparatus suitable for normal data reproduction, and particularly suitable for variable speed data reproduction across tracks.

[0002]

2. Description of the Related Art In a digital data reproducing device,
In the case of PCM audio recording in which an ID code is added to the reproduction data, the reproduction device is controlled by indicating the sampling frequency, the number of quantization bits, and the like. Therefore, the detection and method may cause the system to malfunction, and it is an important subject to obtain an accurate and reliable ID code.

FIG. 12 shows a track format and a block format of a rotary head type magnetic recording / reproducing apparatus which divides a video signal and a PCM audio signal into areas on a track for recording / reproduction. As shown in the track format of FIG. 12, the video signal 53 and the PCM audio signal 54 are divided into areas on the track and recorded. In the PCM audio signal, a predetermined number of blocks are recorded on each track, each block having a fixed number of data. An example of the block format is shown in FIG. Each block has a sync signal indicating the beginning of data, a block address indicating the order of blocks, an ID code for identifying the contents of data, a block address and an ID.
It is composed of a parity for checking an error of 2-byte data of the code, and data and a C1 parity which is a code for error detection / correction of this data. Also in FIG.
As shown in (1), the locus of the head when variable speed reproduction is performed changes with the speed ratio of 1 × 50, 2 × 51, 3 × 52, and the reproduced signal fluctuates.

FIG. 14 is a diagram showing an envelope of a reproduction signal during variable speed reproduction. In FIG. 14, 9 is the envelope of the reproduction signal. As shown in FIG. 14, since the C / N of the reproduced signal fluctuates, the C / N is not secured at a low reproduction level, and an error cannot be detected by the parity for error detection of the ID code. . Therefore, even if it is determined that the parity is correct, the reliability of the ID code may be low.

Regarding the conventional technique for obtaining a reliable ID code at the time of variable speed reproduction, when an ID code redundantly recorded on a magnetic tape as a recording medium is reproduced by searching the magnetic tape at a high speed. A system for performing coincidence detection is disclosed in JP-A-64-49193.

In addition, the start ID, which means the beginning of the song, is input to the register in the information other than the music signal on the tape.
A system for determining by majority decision is disclosed in Japanese Patent Laid-Open No. 64-64-
It is shown in the 19550 publication. In both cases, when performing high-speed reproduction and searching, parity check and coincidence detection or majority decision are performed to reduce erroneous ID detection and improve reliability.

[0007]

In the prior art, parity check and coincidence detection or majority decision were performed during high speed search. However, due to a change in reproduction speed of variable speed reproduction, the reliability of error detection by parity changes, and processing is performed. There was not enough consideration given to changing the method accordingly.

An object of the present invention is to improve the error detection capability of the ID code, and switch the ID detection method in response to variable speed reproduction to improve the reliability and the detection capability of the ID code.

[0009]

In order to achieve the above object, C1 parity including an ID code is generated at the time of recording, and C1 error check is performed at the time of reproduction to improve the error detection capability. Further, the envelope of the reproduction signal is detected, and it is determined whether the parity check result is valid or invalid depending on the magnitude of the reproduction signal. further,
When the digital data is reproduced at a variable speed, one of the checks such as parity check, C1 error check, coincidence check and majority check, or a combination of detection methods can be selected according to the reproduction speed. It is characterized by doing. In particular, during variable speed reproduction, it is determined whether or not to perform the C1 error check in accordance with the variable speed.

[0010]

The ID code error detection capability can be improved by recording the C1 parity including the ID code and performing the C1 error check during reproduction. Further, during variable speed reproduction, by enabling / disabling the parity check by the envelope, it is possible to prevent the ID code from being erroneously detected because the reproduction C / N is low. Furthermore, during normal reproduction, the ID code can be reproduced without erroneous detection by performing C1 error check and coincidence / majority check for the ID code. During variable speed reproduction, C1 error check is not performed.
Change the detection method so that a parity check and a majority / consensus check are performed. This is to perform a C1 error check when the speed of the variable speed increases during variable speed reproduction.
This is because the block length cannot be reproduced and all ID codes are detected as errors. Even in such a situation, the ID code can be detected by the parity, matching / majority check.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIG. 1 as to a digital data reproducing method by a rotary head type magnetic recording / reproducing apparatus recorded in accordance with the track format and block format of FIG. Figure 1
FIG. 6 shows a flowchart of the digital data reproducing method of the present invention. 1 executes the error detection of the ID code by the parity, and when the error is detected, the flag F
In the step of setting p to 1, 2 is an error detection of the ID code by C1 parity, and when the error is detected, the flag Fc is set to 1 and 3 is of the rotary head type magnetic recording / reproducing apparatus. The tape feeding speed n is judged, and 4 and 5 are ID by the above Fp or Fc.
In the step of checking the coincidence or majority decision of the ID code written multiple times in one track with respect to the data determined not to be erroneous, 6 judges the result of the coincidence or majority decision, and 7, 8 Is a step of outputting an ID code and a flag indicating an error in the ID code in accordance with the judgment 6.

The operation of the above configuration will be described. In the rotary head type magnetic recording / reproducing apparatus, one track of data reproduced from the head has a predetermined number of blocks as described in the description of FIG. In step 1, the parity of each block is checked with respect to a predetermined block in this one track, the error detection of the ID code of each block is performed, and the resulting flag Fp is set for each code.

Next, in step 2, error detection by C1 parity is executed for a predetermined block of one track,
When an error is detected, the flag Fc is set to 1. Next, in judgment 3, the tape feeding speed n of the rotary head type magnetic recording / reproducing apparatus is judged, and the execution steps thereafter are changed depending on whether it is larger or smaller than the predetermined value N.
If n> N, step 4 is executed, and for ID data judged to be correct by the parity check, a plurality of ID codes that are multiple-written in one track are matched or a majority check is executed. If n ≦ N, step 5 is executed, and for the ID code determined to be correct by the C1 error check, a plurality of ID codes that are multiple-written in one track are matched or a majority check is performed.

After the step 4 or 5 is executed, if it is judged at the decision 6 that the data match or the majority decision is made, or if the majority decision is made, it is finally decided that the data is correct, and at step 7, the ID A flag F = 0 indicating that the code is correct is output. Further, if the result of judgment 6 is that there is no match or the majority decision cannot be taken, it is judged that the ID code is incorrect, and F = 1 is output to indicate that the ID code could not be detected.

The operation of changing the processing according to the tape feeding speed in the judgment 3 will be described in more detail with reference to the timing chart of FIG. FIG. 2 is a timing chart when the tape feeding speed n is higher than N. 9 is a reproduced signal, 10 is a block synchronization signal detected from the reproduced signal, 11 is a parity check result,
12 shows the C1 parity check result. As shown in FIG. 2, the reproduced signals are b ₀ , b ₁ , b ₂ ,
It is a block like b ₃ and b ₄ . In the parity check, the code length is 3 words consisting of the block address, the ID code, and the parity.
There is a high probability that the block b _{1 with} / N is judged to be correct. However, in the C1 error check, since the error check is performed on the data over one block, the probability of being judged as an error in all the blocks is high. Therefore, in such a case, if the ID code is detected due to the C1 error, the ID code cannot be detected, but the judgment 3 in FIG. Further, in the embodiment of the present invention shown in FIG. 1, the effect of the present invention can be obtained even if the majority decision and the coincidence check are executed on the data for which Fp is correct and Fc is correct in step 5.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 3 shows a flow chart of the digital data reproducing method for detecting the reproducing level according to the present invention. 13 determines the reproduction level 1 of the reproduction signal and determines 1
4 forcibly sets the parity detection result to an error and sets the flag F
In the step of setting p to 1, other steps and judgment are the same as those in FIG. In FIG. 3, when the reproduction level is equal to or higher than the fixed value L, step 1 is performed as in the flow of FIG.
When the reproduction level is smaller than the constant value L, the error detection result of the ID of the block is forcibly set to Fp = 1 in step 14. The subsequent processing is the same as that in FIG. This judgment 13 and step 14
C / N that easily causes error detection and omission
It is possible to make all the parity detection results of the part in which is deteriorated. As a result, even if only the parity check processing is performed in the execution of the processing in step 4, the error detection capability is improved and the reliability is improved.

As described above, the operation of changing the processing according to the reproduction level in the determination 13 will be described in more detail with reference to the timing chart of FIG. FIG. 4 is a timing chart of the parity check using the reproduction level detection result. Reference numeral 15 is a reproduction level detection signal which is set to a high level when the detection result of the reproduction level 1 is a fixed value L or more and is set to a low level when the detection result is smaller than L. 9, 1
0, 11, and 12 are the same as in FIG. As shown in FIG. 4, the reproduced signal is in blocks such as b ₀ , b ₁ , b ₂ , ... B ₁₂ . With respect to the reproduction level of this reproduction signal, the reproduction level is detected with a high level when C / N is high and a low level when C / N is deteriorated with reference to a constant value L, and a high section , That is, the blocks b ₀ , b ₃ , b ₄ , b ₅ etc. in which C / N is taken are in step 1
Parity check is performed, and in the low section, that is, in the blocks b ₁ and b ₂ in which the C / N is deteriorated, in step 14, all the error detection results of the ID of the block are forced to be errors. Therefore, in such a case, the reproduction level 1 is a constant value L
If it is less than C, the parity check is not performed, so C /
The false detection of the part where N is deteriorated is eliminated, and step 4
Even if only the parity check process is performed by executing the process in step 1, the error detection capability is improved and the reliability is improved.

Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 5 is a flow chart of a digital data reproducing method for detecting the tape feeding speed from the reproducing level according to the present invention. Reference numeral 31 is a step of counting the section t in which the reproduction level 1 is equal to or more than the constant value L. 32 is determined that the tape feeding speed n is higher than the constant value N when t counted in step 31 is smaller than the constant value T. , T is a constant value T
In the above case, it is determined that n is equal to or less than the constant value N, and other steps and determinations are the same as those in FIG. In FIG. 5, judgment 1
3, the reproduction level 1 is detected, the same processing as in FIG. 3 is performed,
In step 31, the section t in which the reproduction level 1 is equal to or larger than the constant value L is counted, and if the result t is smaller than the constant value T in judgment 32, it is judged that the tape feeding speed n is larger than the constant value N, and t is equal to or larger than T. Then, n is determined to be N or less. The subsequent processing is the same as in FIG.

The operation of detecting the tape feed speed from the reproduction level detection signal in the determination 32 will be described in more detail with reference to the timing chart of FIG. FIG. 6 is a timing chart for explaining the operation of detecting the tape feed speed from the reproduction level detection signal. As shown in 1) and 2) of FIG. 6, the reproduction signal 9 fluctuates when the tape feeding speed n is changed. With respect to this reproduction signal, a reproduction level 1 is detected, and a high level section and a low level section are detected based on a constant value L to obtain a reproduction level detection signal 15.
The high section t ₁ or t ₂ of the reproduction level detection signal 15 is counted in step 31 of FIG. Regarding the count result t, in the judgment 32 of FIG. 5, when t is smaller than the constant value T, it is judged that the tape feeding speed n is larger than the constant value N, and when t is T or more, n is N or less. to decide. That is, if t ₁ > t ₂ , then n ₁ <n ₂ . Further, the constant values T and N are uniquely determined. Therefore,
The tape feed speed can be detected by detecting the reproduction level and counting the high section of the reproduction level detection signal. Based on the parity check result by the judgment 32 in FIG.
You can match the D code and check the majority.

Next, the operation of the embodiment of the present invention, the ID code matching and majority decision in FIGS. 3 and 5 will be described with reference to FIG.
Will be described. FIG. 7 is a time chart for explaining the error detection method by coincidence and majority decision according to the present invention. In FIG. 7, the reproduction signal 9 is a block like b ₀ , b ₁ , b ₂ , ... B ₂₂ . Regarding the reproduction level of this reproduction signal, the blocks such as b ₁ , b ₄ , b ₇ etc. in the high section of the reproduction level detection signal 15 detected on the basis of the constant value L perform parity check, but b ₀ , b ₂ , B ₃ etc. are forced to be in error as in the method described in the second embodiment of the present invention shown in FIG. The digital data reproduced by the digital data reproducing method of the present invention is the same data a plurality of times in each block. For example, ID code is ID0, ID1, ID
2 and ID3, there are IDs in the b ₀ block
0, b ₁ is the block ID1, b ₂ to the block ID2,
b ₃ to block ID3, b ₄ to block ID0, ... b
It is assumed that ID2 is repeatedly recorded in ₂₂ blocks. Then, as a result of the parity check in step 4 of FIG. 3, Fp determined to be correct is OK data,
Since the data having the same ID number should have the same data content, the ID ₁ of the b ₁ block, the ID 1 of the b ₁₃ block, the ID 0 of the b ₄ block, the ID 0 of the b ₁₆ block, and the ID 3 of the b ₇ block in FIG. b ₁₉ blocks ID3, b ₁₀ blocks ID2 and b ₂₂ block ID of
Regarding 2, it is possible to check the data for errors by matching the data or taking a majority vote. This allows
In the step of FIG. 3, even if the C1 error check result by the C1 parity is erroneous, that is, Fc is NG, the error detection capability is improved and the reliability is improved.

A fourth embodiment of the present invention will be described below with reference to FIG. FIG. 8 shows a flowchart of the digital data reproducing method of the present invention. Reference numeral 16 is a step for determining the tape feeding speed, and other steps are the same as those in FIG. The operation of the above configuration will be described. In the rotary head type magnetic recording / reproducing apparatus, first, the control means for determining the tape feeding speed according to the setting condition from the outside,
The playback speed is determined and the data is played back. The data of one track reproduced from the head is composed of a predetermined number of blocks as described in the description of FIG. In step 1, the parity of each block is checked with respect to a predetermined block in this one track, the error detection of the ID code of each block is performed, and the resulting flag Fp is set for each code.

Next, in step 2, error detection by C1 parity is executed for a predetermined block of one track,
When an error is detected, the flag Fc is set to 1. Next, in judgment 3, the tape feeding speed n of the rotary head type magnetic recording / reproducing apparatus is judged, and the execution steps thereafter are changed depending on whether it is larger or smaller than the predetermined value N.
If n> N, step 4 is executed, and for ID data judged to be correct by the parity check, a plurality of ID codes that are multiple-written in one track are matched or a majority check is executed. If n ≦ N, step 5 is executed, and for the ID code determined to be correct by the C1 error check, a plurality of ID codes that are multiple-written in one track are matched or a majority check is performed.

After the step 4 or 5 is executed, if it is judged in the decision 6 that the data match or the majority vote agrees, or if the majority vote is taken, it is finally decided that the data is correct, and in step 7, the ID A flag F = 0 indicating that the code is correct is output. Further, if the result of judgment 6 is that there is no match or the majority decision cannot be taken, it is judged that the ID code is incorrect, and F = 1 is output to indicate that the ID code could not be detected. In this way, the same operation as in FIG. 1 can be performed by receiving the information of the tape feeding speed n from the control means for determining the tape feeding speed and changing the processing in judgment 3 according to the tape feeding speed.

Next, a sixth embodiment of the present invention will be described with reference to FIG. FIG. 9 shows a flowchart of the digital data reproducing method for detecting the reproducing level according to the present invention. 13 determines the reproduction level 1 of the reproduction signal and determines 1
4 forcibly sets the parity detection result to an error and sets the flag F
In the step of setting p to 1, other steps and judgment are the same as those in FIG. In FIG. 9, when the reproduction level is equal to or higher than the constant value L, step 1 is performed as in the flow of FIG.
When the reproduction level is smaller than the constant value L, the error detection result of the ID of the block is forcibly set to Fp = 1 in step 14. The subsequent processing is the same as in FIG. This judgment 13 and step 14
C / N that easily causes error detection and omission
It is possible to make all the parity detection results of the part in which is deteriorated. As a result, even if only the parity check processing is performed in the execution of the processing in step 4, the error detection capability is improved and the reliability is improved.

The eighth embodiment of the present invention will be described below with reference to FIG. FIG. 10 is a block diagram of a digital data reproducing device for realizing the first to fourth embodiments of the present invention. Reference numeral 20 is a magnetic tape recorded according to the track format or block format as shown in FIG. 12, 21 is a rotary cylinder, 22,
23 is a head A attached to the rotary cylinder 21,
Heads B and 24 are reproduction amplifiers, 25 is a demodulation circuit that performs waveform equalization, data extraction, and demodulation processing, 26 is RAM that stores data, 27 is an address control circuit that controls RAM, and 28 is , A parity check circuit for performing an error check on the ID code by parity, 29 is a C
An error correction circuit for detecting and correcting a data error such as C1 error check by one parity, 30 is a data output control circuit for outputting data through interpolation processing or conversion from digital to analog, 33 is a servo circuit, 34 is
A system control circuit for controlling the entire apparatus, 35 is a reproduction level detection circuit for a reproduction signal, 36 is a counter for measuring a section of a detected reproduction level 1 which is a predetermined value L or more, 37
Is an Fp setting circuit that sets correctness / incorrectness for the parity check result, 38 is an Fc setting circuit that sets correctness / incorrectness for the C1 error check result, and 39 is based on the same data being recorded multiple times. , A coincidence / majority-check circuit for matching data or taking a majority decision to perform an error check, 40 is an F setting circuit for setting correctness / incorrectness of the result of the coincidence / majority decision, 41 is an output circuit for outputting ID and F, 42 Is a condition judging circuit for judging conditions at the time of performing various processes, 44 is a program ROM in which processing contents, judgment conditions, etc. are written, 43 is a program counter for controlling the program ROM, 45
Is a control signal generation circuit that generates a control signal for each circuit from a command signal from the program ROM. Since the Fp setting circuit 37 and the Fc setting circuit 38 are not set at the same time, one setting circuit can be switched and shared.

The operation of the above configuration will be described. The present invention controls a series of processes at the time of reproducing an ID code by using software. A magnetic tape 20 on which digital data including an ID code is recorded is attached to a rotary cylinder 21.
The digital data reproduced by the head A22 and the head B23 attached to, and reproduced through the reproduction amplifier 24 are waveform equalized by the demodulation circuit of 25, data extraction,
It is demodulated and temporarily stored in the RAM 26. The ID code and the block address of these are subjected to an error check by a parity check circuit 28 and temporarily stored in the RAM 26. The data temporarily stored in the RAM 26 is subjected to error detection / correction processing such as C1 error check by C1 parity in the error correction circuit 29. When storing data in the RAM 26 or performing correction processing in the error correction circuit 29, the address control circuit 27 is used to
Control M26. In addition, the data that has been subjected to one type of processing is output through 30 data output control circuits after undergoing interpolation processing and conversion from digital to analog. Incidentally, 3
Reference numeral 3 is a servo circuit, and 34 is a system control circuit, which controls the tape feed speed and the entire system.

Next, a detailed description will be given in correspondence with FIG. FIG. 5 is a diagram showing a flowchart of the digital data reproducing method of the present invention. The reproduction level detecting circuit 35 detects the reproduction level l, and the condition judging circuit 42 judges the magnitude relationship between l and a constant value L. If l ≧ L, then 2
The flag Fp is set to 0 or 1 in accordance with the check result by the parity check circuit 8 and if 1 <L, the flag Fp is forcibly set to 1. The program for performing this control is controlled by the program counter 43 to control the program R.
A signal for reading out from the OM 44 and controlling the Fp setting circuit 37 is generated and output by the control signal circuit 45. The above corresponds to the judgment 13, step 1 and step 14 in FIG.

In step 2, C1 of the error correction circuit 29 is
According to the error check result, the Fc setting circuit 38 sets the flag Fc to 0 or 1. Next, with respect to the detected reproduction level 1, a section of a certain value L or more, that is, C / N
The section t in which the difference is taken is measured by the counter of 36 to detect the tape feeding speed n, and the detection result is judged by the condition judgment circuit 42. If n> N, Fp = 0, that is, for the data whose parity check result is OK. , 39, or by a majority circuit, a match or majority check is performed. If n ≦ N, then Fc
= 0, that is, C1 error check result is OK, data is checked for agreement and majority. A program for performing this control is read from the program ROM 44 under the control of the program counter 43, and a signal for selecting the setting result Fp of the Fp setting circuit 37 and the setting result Fc of the Fc setting circuit 38 is generated and output by the control signal circuit 45. To do. The above is step 31, determination 32, step 4, step 5 in FIG.
Corresponding to. If the result of the agreement or majority decision is judged by the condition decision circuit 42, and if the result of the agreement or majority decision is OK, then ID
The flag F = 0 indicating that the code is correct is output, and NG
If so, a flag F = 1 indicating that the ID code is incorrect
Is output. A program for performing this control is read from the program ROM 44 under the control of the program counter 43, and a signal for controlling the F setting circuit 40 is generated and output by the control signal circuit 45. The above corresponds to judgment 6, step 7 and step 8 in FIG. The ID code thus obtained and the flag F indicating the correctness of the data are stored in the output circuit 41.

As described above, when the apparatus of the present invention is used, the reproduction level of the reproduction signal is detected to detect the tape feeding speed, the C1 error check, the coincidence and majority check are performed during the normal reproduction, and further the variable speed reproduction is performed. However, since the data in the portion where the C / N is deteriorated from the reproduction level detection result is regarded as an error, erroneous detection is eliminated, and the flag indicating the correctness or erroneousness of the data is checked to make a data match and a majority decision. Ability is increased and highly reliable data reproduction is realized.

Next, a ninth embodiment of the present invention will be described with reference to FIG. FIG. 11 is a block diagram of a digital data reproducing device for realizing the fifth to seventh embodiments of the present invention. 11 differs from the embodiment of FIG. 10 in that instead of detecting the tape feed speed from the reproduction level detection,
The configuration is such that information on the tape feed speed is input from the system control circuit to the condition determination circuit 42, and the other parts are the same as in FIG. Next, a detailed description will be given in correspondence with FIG. FIG. 9 is a diagram showing a flowchart of the digital data reproducing method of the present invention. First, the system control circuit 34 determines the reproduction speed according to the setting condition from the outside when reproducing the digital data, and reproduces the data. This corresponds to step 16 in FIG.

With respect to this reproduction signal, the reproduction level detection circuit 35 detects the reproduction level l, and the condition judgment circuit 42 judges the magnitude relationship between l and a constant value L. If l≥L, then 2
The flag Fp is set to 0 or 1 in accordance with the check result by the parity check circuit 8 and if 1 <L, the flag Fp is forcibly set to 1. The program for performing this control is controlled by the program counter 43 so that the program R
A signal for reading out from the OM 44 and controlling the Fp setting circuit 37 is generated and output by the control signal circuit 45. The above corresponds to the judgment 13, step 1 and step 14 in FIG.
In step 2, the flag Fc is set to 0 by the Fc setting circuit 38 according to the C1 error check result of the error correction circuit 29.
Or set to 1.

Next, the tape feed speed information n previously determined by the system control circuit 34 is directly fetched into the condition judgment circuit 42 and compared with a constant value N, and if n> N, Fp =
0, that is, data whose parity check result is OK,
The matching or majority decision circuit of 39 performs a matching or majority decision check, and if n ≦ N, Fc = 0, that is, the data for which the C1 error check result is OK is subjected to a match or majority decision check. A program for performing this control is read from the program ROM 44 under the control of the program counter 43, and the setting results Fp and Fc setting circuit 3 of the Fp setting circuit 37 are read.
A control signal circuit 45 generates and outputs a signal for selecting the setting result Fc of 8. The above corresponds to judgment 3, step 4, and step 5 in FIG. The result of the coincidence / majority decision is judged by the condition judgment circuit 42, and if the result of the coincidence / majority check is OK, a flag F = 0 indicating that the ID code is correct.
Is output, and if NG, a flag F = 1 indicating that the ID code is incorrect is output. The program for performing this control is controlled by the program counter 43 to control the program RO.
It is read from M44, and the control signal circuit 45 generates and outputs a signal for controlling the F setting circuit 40. The above is FIG.
This corresponds to the judgment 6, step 7 and step 8. The flag F indicating the correctness of the ID code and the data thus obtained is set to 4
1 in the output circuit.

As described above, when the apparatus of the present invention is used, the reproduction level of the reproduction signal is detected and the tape feed speed information is directly obtained from the system control means, and the C1 error check, the coincidence and the majority decision are performed during the normal reproduction. Even at the variable speed reproduction, the data of the portion where the C / N is deteriorated from the reproduction level detection result is regarded as an error, so that the erroneous detection is eliminated, and the data coincidence and the majority decision are performed by looking at the flag indicating the correctness of the data. Therefore, the error detection capability is improved, and highly reliable data reproduction is realized.

[0034]

As described above, according to the present invention, it is possible to improve the error detection capability of the ID code by recording the C1 parity including the ID code and performing the C1 error check at the time of reproduction, so that the variable speed reproduction is performed. At times, when the reproduction level of the reproduction signal is low, the parity check result is set as an error, so that the reproduction C / N is low and thus the ID code is not erroneously detected. Also, during normal reproduction, an ID without erroneous detection can be reproduced by performing a C1 error check, a match, and a majority check on the ID code. Depending on the reproduction speed during variable speed reproduction, the C1 error check is performed. Instead, the detection method is changed so that the parity check and the majority check are performed. This is because if the variable speed is increased during variable speed reproduction, the length of one block for C1 error check cannot be reproduced and all ID codes are detected as errors. Even in such a situation, the ID code can be detected by the parity, coincidence and majority check.

[Brief description of drawings]

FIG. 1 is a flowchart of a digital data reproducing method of the present invention.

FIG. 2 is a timing chart of a reproduction signal and each check signal.

FIG. 3 is a flowchart of a digital data reproducing method for detecting a reproduction level according to the present invention.

FIG. 4 is a timing chart for explaining a parity check using the reproduction level detection result of the present invention.

FIG. 5 is a flowchart of a digital data reproducing method for detecting a tape feeding speed from a reproducing level according to the present invention.

FIG. 6 is a timing chart illustrating a method of detecting a tape feeding speed from a reproduction level detection signal of the present invention.

FIG. 7 is a timing chart for explaining a coincidence and majority check method according to the present invention.

FIG. 8 is a flowchart of a digital data reproducing method of the present invention.

FIG. 9 is a flowchart of a digital data reproducing method for detecting a reproduction level according to the present invention.

FIG. 10 is a block diagram of a digital data reproducing apparatus for detecting a tape feeding speed using the reproduction level detection result of the present invention.

FIG. 11 is a block diagram of a digital data reproducing apparatus using tape feed speed information from the system control means of the present invention.

FIG. 12 is a diagram showing a track format of 8 mm video.

FIG. 13 is a diagram showing a block format of 8 mm video.

FIG. 14 is a diagram showing a relationship between a reproduction signal and the validity of reproduction data.

[Explanation of symbols]

28 Parity check circuit 29 Error correction circuit 34 System control circuit 35 Playback level detection circuit 36 counter 37 Fp setting circuit 38 Fc setting circuit 39 agreement, majority circuit 40 F setting circuit 42 Condition judgment circuit 43 Program counter 44 Program ROM 45 Control signal generation circuit

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yu Nagai             292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa             Ceremony Company Hitachi Media Media Research Center

Claims (18)

[Claims] 1. A constant number of digital data is defined as one block, a synchronization signal indicating the beginning of each block, an identification signal indicating the order of blocks (hereinafter referred to as a block address), and an identification signal identifying the contents of data. (Hereinafter referred to as an ID code), a code for error checking the block address and the ID code (hereinafter referred to as parity), and a code for detecting an error in the data of one block including the ID code. A signal in which an ID code that is the same data is arranged a plurality of times over each block in the added recording signal, and the recording signal is formed by forming a track on a magnetic tape by a rotary head type magnetic recording device and recording a predetermined number of blocks in one track. In the reproducing method for reproducing, the first step of checking the ID code for an error by the parity, A second step of detecting an error in the ID code by the C1 parity, and a tape feeding speed of the magnetic tape are detected, and one of the first and second steps is detected based on the tape feeding speed.
One or two, and a third step of determining an error in the ID code, a digital data reproducing method. 2. The digital data reproducing method according to claim 1, wherein the third step uses the error detection result of the second step when the tape feeding speed is equal to or less than a predetermined value N, and Error determination is performed, and when it is larger than N, the error determination result of the first step is used to perform the error determination of the ID. 3. The digital data reproducing method according to claim 2, wherein the third step is to judge an error based on the same data being provided a plurality of times over each block. . 4. A digital data reproducing method according to claim 1, 2, or 3, wherein the first step detects an envelope of a reproduced signal,
A method for reproducing digital data including forcibly making an error when the reproduction signal level is low. 5. The digital data reproducing method according to claim 1, wherein the third step detects the envelope of the reproduced signal,
A digital data reproducing method characterized by detecting a tape feeding speed from an envelope detection result. 6. A constant number of digital data is defined as one block, a synchronization signal indicating the beginning of each block, an identification signal indicating the order of blocks (hereinafter referred to as a block address), and an identification signal identifying the contents of data. And a code for error check of the block address and the ID code (hereinafter referred to as parity), and a code for detecting an error of the data of the one block including the ID code. In the reproducing method, an ID code that is the same data is arranged over a plurality of times, and the recording signal is reproduced by forming a track on a magnetic tape by a rotary head type magnetic recording device and recording a predetermined number of blocks on one track. A first step of checking the ID code for errors with the parity; and the C1 parity with A second step of detecting an error in the ID code and one of the first and second steps based on the tape feeding speed information from the control means for determining the tape feeding speed of the magnetic tape, or And a third step of selecting two and determining an ID code error. 7. The digital data reproducing method according to claim 1, wherein the third step uses the error detection result of the second step when the tape feeding speed is equal to or lower than a predetermined value N, and Error determination is performed, and when it is larger than N, the error determination result of the first step is used to perform the error determination of the ID. 8. The digital data reproducing method according to claim 2, wherein the third step determines an error based on the fact that the same data is provided a plurality of times over each block. . 9. The digital data reproducing method according to claim 1, 2, or 3, wherein the first step detects an envelope of a reproduced signal,
A method for reproducing digital data including forcibly making an error when the reproduction signal level is low. 10. A constant number of digital data is defined as one block, a synchronization signal indicating the beginning of each block, an identification signal indicating the order of blocks (hereinafter referred to as a block address), and an identification signal identifying the contents of data. (Hereinafter referred to as an ID code), a code for checking the block address and the ID code for error (hereinafter referred to as parity), and a code for detecting an error in the data of one block including the ID code (hereinafter referred to as a parity). , C1 parity) is added to each block, and an ID code having the same data is arranged a plurality of times over each block. The recording signal is formed by a rotary head type magnetic recording device to form a track on a magnetic tape. A digital data reproducing apparatus for reproducing a signal in which a predetermined number of blocks are recorded on a track, A first check unit for checking an ID code error, a second check unit for detecting the ID code error by the C1 parity, a detecting unit for detecting a tape feeding speed of the magnetic tape, And a discriminating means for discriminating an ID code error by selecting one or two of the check results by the first and second checking means based on the tape feeding speed detected by the detecting means. A digital data reproducing device characterized by the above. 11. The digital data reproducing apparatus according to claim 10, wherein when the tape feeding speed detected by the detecting means is equal to or less than a predetermined value N, the discriminating means makes an error in the second checking means. An ID error judgment is made using a detection result, and when it is larger than N, an ID error judgment is made using an error detection result of the first checking means. 12. The digital data reproducing apparatus according to claim 11, wherein the discriminating means judges an error based on the same data a plurality of times over each block. 13. The digital data reproducing apparatus according to claim 10, wherein the first checking means detects an envelope of a reproduced signal and forcibly makes an error when the reproduced signal level is low. A digital data reproducing apparatus including: 14. The digital data reproducing apparatus according to claim 10, wherein the detecting means detects the envelope of the reproduction signal and detects the tape feeding speed from the detection result of the envelope. 15. A constant number of digital data is defined as one block, a synchronization signal indicating the beginning of each block, an identification signal indicating the order of blocks (hereinafter referred to as a block address), and an identification signal identifying the contents of data. (Hereinafter, referred to as an ID code), a code for checking the block address and the ID code for error (hereinafter, referred to as parity), and a code for detecting an error in the data of one block including the ID code (hereinafter, referred to as a parity). , C1 parity) is added to each block, and an ID code having the same data is arranged a plurality of times over each block. The recording signal is formed by a rotary head type magnetic recording device to form a track on a magnetic tape. In a digital data reproducing device for reproducing a signal in which a predetermined number of blocks are recorded on a track, First check means for checking an ID code error; second check means for detecting the ID code error by the C1 parity; control means for determining a tape feeding speed of the magnetic tape; and the control means And a discriminating means for discriminating an ID code error by selecting one or two of the check results by the first and second check means based on the tape feeding speed determined by. Characteristic digital data reproducing device. 16. The digital data reproducing apparatus according to claim 15, wherein when the tape feeding speed determined by the control means is less than or equal to a determined value N, the discriminating means makes an error in the second checking means. An ID error judgment is made using a detection result, and when it is larger than N, an ID error judgment is made using an error detection result of the first checking means. 17. The digital data reproducing apparatus according to claim 16, wherein the judging means judges an error based on the fact that the same data is provided a plurality of times over each block. 18. The digital data reproducing apparatus according to claim 15, 16, or 17, wherein the first checking means detects an envelope of a reproduced signal and forcibly makes an error when the reproduced signal level is low. A digital data reproducing apparatus including: