JPH1050003A - Digital signal recording / reproducing device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To accurately inform a digital signal recording / reproducing apparatus when maintenance is to be performed. When a digital signal reproducing device detects that a magnetic head 3 does not accurately trace a track 8 from a digital signal on a track 8, an error detection and correction circuit 70 that generates a flag and a predetermined signal are provided. Counter that calculates the number of error flag pulses that occurred during the measurement period t1
21, a comparison circuit 10 for comparing whether the number of the error flag pulses is equal to or more than a certain amount, and a display unit for indicating to the user when the comparison circuit 10 detects that the number is more than a certain amount. Four
Equipped. An arithmetic circuit 1 is connected between the counter 21 and the comparison circuit 10, and the arithmetic circuit 1 once takes in the total number of error flag pulses generated within the measurement time t1 × N, and divides the total number by N to obtain an average. It has a counting function of calculating a value and outputting it to the comparison circuit 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording / reproducing apparatus such as a digital VTR and the like.
The present invention relates to a digital signal recording / reproducing apparatus provided with a notifying means for indicating deterioration of a magnetic tape.

[0002]

2. Description of the Related Art A digital signal recording / reproducing apparatus for digitally processing a video or audio signal and recording / reproducing via a magnetic tape is known as shown in FIG.
No. 2745). This relates to a so-called DAT (Digital Audio Tape), and for convenience of explanation, only a reproduction circuit block is shown. A pair of magnetic heads (3) (3) are provided on the peripheral surface of the rotary cylinder (30), and perform recording and reproduction via a magnetic tape (6) conveyed by a capstan motor (32). The reproduced signal from the magnetic head (3) is
Through an amplifier (34) and a digital demodulation circuit (7), it is inputted to a detection and correction circuit (9) for performing signal correction and an error check circuit (90) for generating an error flag pulse described later.
The error check circuit (90) is connected to the detection and correction circuit (9),
An output from the detection and correction circuit (9) is converted into an analog signal by a D / A converter (72) and supplied to an output terminal (51). A pilot signal for ATF is inserted in the reproduction signal in the magnetic head (3), and the reproduction signal is input to a servo circuit (2) for controlling the phase of the capstan motor (32) based on the pilot signal. Is done.

As shown in FIG. 8, tracks 8 are formed on the magnetic tape 6 so as to be inclined with respect to the tape running direction. Controlling the running timing of the magnetic tape 6 so that the magnetic head 3 accurately traces the track 8 is called tracking control. The audio signal is digitally processed and recorded on the track (8) as described above, and a parity bit (80) for error correction detection is added to the digitally encoded signal for each predetermined code string. Has been added. Parity bit (80)
Corresponds to the digital code string recorded on the track (8). When the magnetic head (3) does not accurately trace the track (8), as shown by a dotted line, for example, the traced code string And the value of the parity bit (80) do not correspond to each other, it can be seen that the magnetic head (3) does not accurately trace the track (8). The error check circuit (90)
Compares the digital code string with the parity bit (80),
When there is a trace error of the magnetic head (3), an error flag pulse is generated.

At the time of reproduction, in FIG. 7, a clock generation circuit (20) generates a clock pulse as a reference signal, and the clock pulse is supplied to an error check circuit (90). The error check circuit (90) performs the operation for each magnetic head within the measurement time t1 (see FIG. 3) which is the section of the clock pulse.
(3) Detect a trace error for each. The error flag pulse from the error check circuit (90) is output to the detection / correction circuit (9)
And the detection and correction circuit (9) detects a position where the magnetic head (3) does not accurately trace the track (8).
Perform signal correction. Here, as a signal correction method, there are methods such as average value interpolation, previous value hold, and the like. Since all of them are well-known techniques, detailed descriptions thereof are omitted.

When the apparatus and the magnetic tape (6) are used for many years, the magnetic head (3) is clogged and the tape is damaged.
When reproduced in such a state, the number of occurrences of error flag pulses increases, and the detection and correction circuit (9) cannot correct the error.
Noise may occur on the screen. Therefore, it is necessary to perform maintenance such as cleaning of the magnetic head (3) and replacement of the magnetic tape (6), and the user must be informed of the maintenance. Therefore, the error check circuit (9
(0), based on the clock pulse, a counter (21) that measures the number of occurrences of the error flag pulse at every measurement time t1, a comparison circuit (10) that detects whether the number of occurrences is equal to or more than a certain amount, and a comparison circuit. When the circuit (10) detects that the number of generated error flag pulses has exceeded a certain amount, the display unit displays that fact.
The one provided with (4) is known.
No. 5).

[0006]

When the magnetic tape (6) is used, minute dust may adhere to the magnetic tape (6) or minute scratches may occur locally. In this case, only a part of the magnetic tape (6) has a defect, and there is no need for maintenance such as replacement of the magnetic tape (6). However, in the conventional magnetic recording / reproducing apparatus having the display unit (4), when reproducing a local portion having a flaw or the like on the magnetic tape (6), the number of generated error flag pulses is set to a certain value or more. Is displayed on the display unit (4). Therefore,
In spite of the fact that there is no need for maintenance yet, there is a risk that the user will be given the wrong information that maintenance is necessary. SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic recording / reproducing apparatus that accurately informs when maintenance should be performed.

[0007]

A track (8) on a running recording medium is traced by a rotary magnetic head (3), and digitally processed and recorded on the track (8) in advance. When the magnetic head (3) reproduces the signal from the signal,
When an error generated due to the deterioration of the magnetic head (3) or the recording medium is detected, an error flag pulse generating means for generating a pulse, and the number of error flag pulses generated within a predetermined measurement period t1 are counted. Counter means for comparing whether the number of the error flag pulses is equal to or more than a certain amount, and a display unit for indicating to the user when the comparing means detects that the number is more than a certain amount. In the digital signal recording / reproducing apparatus provided with (4), an arithmetic circuit (1) is connected between the counter means and the comparing means, and the arithmetic circuit (1) measures the measurement time t1 × N (N is Once the total number of error flag pulses generated within the
Has a counting function of calculating the average value divided by and outputting the calculated average value to the comparing means.

[0008]

[Operation and Effect] The arithmetic circuit (1) reads the error flag pulse generated within the measurement time t1 × N, divides the total number of error flag pulses by N, and averages the error flag pulse generated within the measurement time t1. Calculate the value. Therefore, even if the magnetic tape (6) has a minute flaw or the like and a large number of error flag pulses are locally generated within a certain measurement time t1, it is necessary to calculate the average value of the entire measurement time. Thus, the increase amount of the error flag pulse at the measurement time t1 is reduced. Therefore, the display unit (4) does not display that the amount of error flag pulse generation is equal to or more than the predetermined amount, and can prevent the user from erroneously determining that maintenance is necessary. In other words, it is possible to know exactly when maintenance should be performed.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of the present invention will be described below in detail with reference to the drawings. Note that the same reference numerals are used for the same configuration as the conventional one. In this example, a video or audio signal is digitally processed into a code string in which 0 and 1 bits are continuous, and a magnetic tape is used.
The present invention relates to a digital VTR for recording and reproducing via (6). Magnetic tape for other VTRs, eg 8mm VTR
In (6), an MP (Metal powder) tape, which is a metal coating tape, is generally used. However, in the case of a digital VTR, ME (Metal evapo
rated) tape is often used. Magnetic tape (6)
There are various types of display units (4) that indicate that maintenance such as replacement of the cassette (60) in which is stored or cleaning of the magnetic head (3) is necessary. For example, as shown in FIG. Typically, the indicator lamp (4a) is exposed to the apparatus body (40), and the indicator lamp (4a) is turned on when it is determined that the error flag pulse exceeds a certain amount during reproduction. . Note that a display (not shown) that emits predetermined warning characters or the like may be provided in place of the indicator lamp (4a).

FIG. 1 is a block diagram showing a configuration inside a digital signal recording / reproducing apparatus. The rotating cylinder (30) is provided with a pair of magnetic heads (3) and (3) on the peripheral surface, and the magnetic tape (6) wound around the rotating cylinder (30) is transported by the capstan motor (32). The configuration is the same as the conventional one.
For convenience of explanation, the magnetic heads (3) and (3) are referred to as Ach and Bch. The rotary cylinder (30) is rotationally driven by a cylinder motor (31), and an FG (Frequency Generator) pulse is emitted from the capstan motor (32) and the cylinder motor (31). The FG pulse is input to the servo circuit (2),
Based on the frequency of the FG pulse, the capstan motor (3
2) and speed control of the cylinder motor (31) are performed. The cylinder motor (31) emits a PG (Pulse Generata) pulse again, and the servo circuit (2) generates a pulse based on the PG pulse and a phase reference signal input from an external oscillator (not shown). Then, the rotational phase of the cylinder motor (31) is controlled.

The signal to be recorded is a changeover switch (SW)
3) (SW2), recording amplifier (33) (33), changeover switch (SW
Input to the magnetic head (3) via 1). The changeover switch (SW3) switches the connection between a digital input, an analog signal converted into a digital signal, and a nonvolatile memory (5) storing a predetermined data string, and is provided with a nonvolatile memory (5). The reason will be described later. The changeover switch (SW1) is a system control circuit (not shown)
The magnetic heads (3) and (3), the recording amplifiers (33) and (33), and the reproducing amplifier (3)
4) Switch the connection with (34). Changeover switch (SW2)
Is switched by the servo circuit (2) at the rotation cycle of the rotary cylinder (30), and digital data is input to each magnetic head (3) at regular intervals.

When the changeover switch (SW1) is switched to the reproducing side, the outputs from the magnetic heads (3) and (3) are input to the reproducing amplifiers (34) and (34). A switch (SW4) is provided on the output end side of the reproduction amplifier (34), and the switch (SW4) is switched by a switching pulse generated by the servo circuit (2) based on the PG pulse and the phase reference signal. . By such a switching operation, the servo circuit
The output of each magnetic head (3) is input to (2).

Outputs from the reproducing amplifiers (34) and (34) are output to an equalizing circuit (7) for waveform equalizing a signal reproduced by the magnetic head (3).
Entered in 1). Here, the equalizing circuit (71) performs the following operation. Generally, when a video or audio signal is reproduced from an MP tape used for an 8 mm VTR or the like, as shown in FIG. 2B, the one-level pulse waveform draws a symmetric differential waveform before and after the pulse. However, M used for digital VTR
When a signal is reproduced from the E tape, the waveform of the one-level pulse waveform is distorted due to the magnetic characteristics of the tape as shown in FIG. For this reason, the waveform is shaped by the equalizing circuit (71) as shown by the dotted line in FIG. 2 (c) so that one level can be detected accurately.

The output from the equalization circuit (71) is connected to a digital demodulation circuit (7) for restoring a signal obtained by modulating a digital signal during recording so as to be suitable for magnetic recording. ) Is input to the error detection and correction circuit (70). The error detection and correction circuit (70) corrects the error based on the error correction code, and the digital signal processing circuit (73) connected to the error detection and correction circuit (70) facilitates error detection / correction. In this case, the signals rearranged at the time of recording are restored. When an error that cannot be corrected occurs, signal replacement or interpolation is performed.

The error flag pulse generated by the error detection and correction circuit (70) is counted by the counter (21). The counter (21) is connected to a timing pulse generation circuit (20) for generating a gate pulse for controlling the measurement time t1 of the counter (21) based on the switching pulse from the servo circuit (2). Circuit (20) and counter (2
The output side of 1) is connected to the arithmetic circuit (1). Arithmetic circuit (1)
Is connected to a memory (15) capable of storing the results of averaging and statistical processing of the amount of error occurrence, and to a display unit (4) via a comparison circuit (10). The display unit (4) issues a warning message to the user when the measured value exceeds the warning set value, displays the measured value as it is, and displays the result of ranking the measured value in several stages. Or This example is characterized by the operation of the arithmetic circuit (1). Below, the arithmetic circuit
The operation of (1) will be described.

FIG. 3 shows each pulse emitted from each of the above circuits. (a) is an output waveform from the magnetic heads Ach and Bch, (b) and (c) are reset pulses of a counter generated by the timing pulse generation circuit (20), (d) and (e) are (b) and (e) respectively.
A gate pulse generated by the timing pulse generation circuit (20) based on the reset pulse of (c), and (f) is an error flag pulse. The measurement time t1 of the counter (21) is the same as the time during which the gate pulse is at one level, and the arithmetic circuit (1)
Starts at the time of playback, and in the case of the same magnetic tape (6) loaded in the VTR main unit before the start, compares the current date and time with the last measured date and time, and only when the preset measurement interval is exceeded Write to memory (15). At this time, the cassette
In the auxiliary memory (16) in (60), the ID (Ident
data (15)
If the cassette ID is written together with the measured data, it is possible to determine whether the error has increased due to deterioration of the magnetic tape (6) or the like, or has increased due to the VTR side of the magnetic head (3) or the like. The reason why the data is written into the memory (15) only when the measurement interval exceeds a preset value is that it is not necessary to frequently store error data. That is, the storage capacity of the memory (15) itself is finite, and the deterioration of the magnetic head (3) requiring maintenance does not occur frequently except for clogging. , Because it is not meaningful.

The arithmetic circuit (1) measures the number of error flag pulses for t1 seconds and temporarily stores the number in the memory (15). This series of operations is repeated N times. Here, N is an arbitrary natural number set in the arithmetic circuit (1). The arithmetic circuit (1) then divides the total number of error flag pulses stored in the memory (15) by N to calculate an average value of error flag pulses generated within the measurement time t1. In this way, by determining the average value of the amount of error occurrence within the measurement time t1, it is possible to know exactly when the device should be maintained.

That is, minute scratches and the like may be locally present on the magnetic tape (6). In such a case, only a part of the magnetic tape (6) has a defect, and there is no need to maintain the apparatus. However, in the conventional apparatus, when a defective local portion on the magnetic tape (6) is reproduced, the number of occurrences of the error flag pulse is set to a certain amount or more, and the fact is displayed on the display (4). So
Give the user the wrong information that equipment maintenance is required. In this example, the magnetic head (3) is a magnetic tape
(6) Trace a location having a local flaw or the like, and even if the generation amount of the error flag pulse within the measurement time t1 at the time of the trace increases, the arithmetic circuit (1) performs a plurality of measurement times t1 Are averaged, the increase amount of the error flag pulse within the measurement time t1 is reduced. That is, since it is determined whether or not maintenance is necessary based on the average value of the entire measurement time, there is no possibility of erroneously sensing whether or not maintenance is required.

Prior to the calculation of the average value, the arithmetic circuit (1) counts the number of error flag pulses for each measurement time t1, and the amount of error flag pulses generated is significantly larger than other measurement times. An operation of excluding data within the measurement time t1 from the calculation of the average value may be performed. That is, the measurement time t1
Is ignored from the calculation of the total number of error flag pulses, the number n of such measurement times t1 is counted, and the total number of error flag pulses is calculated as (N-
n). As described above, if data in the measurement period t1 in which the generation amount of the error flag pulse is remarkably large is removed from the calculation of the average value, the possibility of erroneous sensing can be further prevented.

As described above, the reproduced signal is composed of a digital code string. The code string which is digitally modulated and recorded on the magnetic tape (6) has an inter-code space based on the electromagnetic conversion characteristics of the magnetic tape (6). The interference causes a pattern peak shift, a decrease in output peak value, and the like, which causes an error. Therefore, when recording data including a large number of such code strings, the apparent error rate is deteriorated even if the magnetic tape (6) and the magnetic head (3) are not deteriorated, and maintenance is required. . The opposite is also true. In order to eliminate the erroneous determination due to the difference in the data sequence to be recorded, the same recording data may be used every time the measurement is performed. For this reason, the error frequency measurement data stored in the non-volatile memory (5) is used. Recording is performed on a magnetic tape (6). A changeover switch (SW3) is provided between the non-volatile memory (5) and the digital signal processing circuit (73), and data or an analog input signal from the non-volatile memory (5) is digitally converted by the changeover switch (SW3). Switches between data and digital input data to be recorded.

When the user wants to know whether maintenance is required or not, he operates the changeover switch (SW3) to read the error measurement data string stored in the non-volatile memory (5) with the magnetic tape ( 6) Perform recording and reproduction on the top, and check the generation status of the error flag pulse. In addition, even in the case of reproducing digital data such as normal video and audio data other than the data string for error measurement, it is possible to measure the degree of deterioration of the magnetic tape (6) and the quality of the recording state, as well as to measure the maintenance. If the standard signal in the non-volatile memory (5) is not deviated to a specific frequency and is a uniform frequency component from a low band to a recording data rate, accurate measurement can be performed. It is not shown in 4).

Further, as shown in FIG. 1, an auxiliary memory (16) and a date adding circuit (17) are connected to the arithmetic circuit (1), so that not only the average value of the measured error flag pulse but also the statistical error The auxiliary memory (16) may store a numerical value, a numerical value according to the frequency of occurrence of an error, or data indicating a stage after the occurrence frequency is classified, together with a measured date. here,
The numerical value according to the frequency of occurrence of an error indicates an error rate, that is, a value obtained by dividing the number of errors that have occurred within the time t1 by all data within the time t1. The data indicating the stage after the occurrence frequency is divided into, for example, the number of error occurrences in the time t1 is divided into five stages. A rank is 0 to 4 ranks, B rank is 5 to 9 ranks ... 20 Above, it indicates only the rank in the case of E rank. The provision of such an auxiliary memory (16) is convenient because it is not necessary to reproduce the magnetic tape (6) every time when it is determined whether maintenance is required at a later date. This auxiliary memory (16) is provided in the apparatus main body (40). In recent years, tape cassettes for digital VTRs (60)
As shown in FIG. 5, some have a built-in memory IC (61) at the end, and the memory IC (61) may be used as an auxiliary memory (16).

The description of the above embodiments is for the purpose of illustrating the present invention and should not be construed as limiting the invention described in the claims or reducing the scope thereof. Further, the configuration of each part of the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made within the technical scope described in the claims.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram inside a digital VTR.

FIG. 2A is a diagram showing levels 0 and 1 of a digital signal;
(b) is a diagram showing a state where the digital signal has correctly changed to a pulse, and (c) is a diagram showing a state where the pulse waveform is distorted.

FIG. 3A shows output waveforms from magnetic heads Ach and Bch,
(b) and (c) are reset pulses of the counter generated by the timing pulse generation circuit, and (d) and (e) are gates generated by the timing pulse generation circuit based on the reset pulses (b) and (c), respectively. The pulse (f) is an error flag pulse.

4A is a diagram illustrating a pulse having a short inversion section between 0 and 1 levels, and FIG. 4B is a diagram illustrating a pulse having a long inversion section between 0 and 1 levels.

FIG. 5 is a perspective view of a cassette provided with a memory at an end.

FIG. 6 is a perspective view of an apparatus main body.

FIG. 7 is a block diagram of a conventional digital signal recording / reproducing apparatus.

FIG. 8 is a diagram showing tracks on a magnetic tape and digital code strings.

[Explanation of symbols]

 (1) Arithmetic circuit (3) Magnetic head (4) Display (8) Track (16) Auxiliary memory (40) Main unit (60) Cassette

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location G11B 5/09 361 G11B 5/09 361Z

Claims (5)

[Claims] A track (8) on a running recording medium is traced by a rotating magnetic head (3), and the track (8) is traced.
A pulse is generated when the magnetic head (3) detects an error caused by the deterioration of the magnetic head (3) or the recording medium when the signal is reproduced from the signal previously digitally processed and recorded. Means for generating an error flag pulse,
A counter means for counting the number of error flag pulses generated within a predetermined measurement period t1, a comparing means for comparing whether or not the number of error flag pulses is equal to or more than a certain amount; When it is detected that the above is the case, in a digital signal recording / reproducing apparatus provided with a display section (4) for indicating to the user, an arithmetic circuit (1) is provided between the counter means and the comparison means. The arithmetic circuit (1) is provided and the measurement time t1 × N (N is a natural number)
A digital signal recording / reproducing apparatus having a counting function of once taking in the total number of error flag pulses generated in the internal memory, calculating an average value obtained by dividing the total number by N, and outputting the calculated average value to the comparing means. 2. The arithmetic circuit (1) reads the number of error flag pulses for each measurement time t1, and the measurement time t1 in which the generation amount of the error flag pulse is significantly larger than the generation amount in other measurement times. 2. The digital signal recording / reproducing apparatus according to claim 1, wherein data in the data is excluded from the calculation of the average value. 3. Each of the magnetic heads (3) and (3) is connected to a changeover switch (SW1) that switches between recording and reproduction, and an error is generated at a recording side terminal of the changeover switch (SW1). 3. A non-volatile memory (5) storing a standard digital data string for detection is connected.
A digital signal recording / reproducing device according to claim 1. 4. The arithmetic circuit (1) stores an average value of error flag pulses, a numerical value after statistical processing, a numerical value according to an error occurrence frequency, or data indicating a stage after the occurrence frequency is classified. 4. A digital signal recording / reproducing device according to claim 1, wherein an auxiliary memory (16) is connected, and said auxiliary memory (16) is provided in the apparatus main body (40) or in a cassette (60) containing a recording medium. apparatus. 5. The error amount in the same cassette (60) is written into the auxiliary memory (16) when the time measured last time is compared with the current time, and when the time exceeds a preset time. 5. The digital signal recording / reproducing apparatus according to claim 4, wherein the digital signal recording / reproducing is performed only for the digital signal.