JP2581032B2 - Signal detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal detection device for detecting a control signal recorded on a recording medium, and more particularly to a signal detection device suitable for detecting a start identification signal in a rotary head type digital audio tape recorder. Related to the device.

[0002]

2. Description of the Related Art In recent years, with the advance of signal processing technology, when recording an audio signal or a video signal on a recording medium, a control signal relating to recording contents, operating conditions, and the like is simultaneously recorded. For example, in a rotary head type digital audio tape recorder, so-called R-DAT, a recording track TR of a track format as shown in FIG. 5 is formed obliquely on a magnetic tape 1 of FIG. 6 which is a recording medium. , Original audio PCM
In addition to the data, a control signal called a subcode is recorded at a predetermined position on one track TR.

In FIG. 5 and FIG. 6, one recording track TR is composed of several (for example, 16) areas (recording areas). ATF
A pilot signal recording area for (auto tracking finding) is provided, and further, sub-code signal recording areas SUB-1 and SUB-2 for various controls are arranged and recorded outside the pilot signal recording area. The numbers in FIG. 5 indicate the number of blocks arranged in each recording area, and one track is composed of 196 blocks.

FIG. 7 schematically shows a rotary head device of the above-mentioned R-DAT. The magnetic tape 1 is wound around a drum of the rotary head device in an angle range of about 90 ° and is driven to travel. It has become. The rotating drum 2 of the rotating head device is provided with a pair of rotating magnetic heads 3a and 3b with an angle difference of 180 °.

Here, as an example of the R-DAT standard, the width Wt of the magnetic tape 1 is 3.81 mm, the effective recording width Wa of digital data is 2.61 mm, the tape speed is 7.20 mm, and the oblique recording track TR Has a total length of 23.5mm and a track pitch of 1
2.0 μm, the inclination angle θ of the recording track TR is 6 ゜ 22 ′, and the azimuth angle α is ± 20 °. The diameter and the number of revolutions of the rotating drum 2 are, for example, 30 mm and 2000 rpm, respectively.
That is, the head moving speed or the head scanning speed on the track TR is set to 3.13 m / s.

Further, one of the 196 blocks in one track has 288 bits as shown in FIG. 8, and the block synchronization unit Sync of 8 bits and the identification code (ID) of 8 bits are sequentially provided from the head. Code) part W
A 1, 8-bit block address portion W2 and an 8-bit parity P are arranged, followed by 256-bit data (PCM data or subcode data). The parity P is obtained by an exclusive OR of the ID code part W1 and the block address part W2 or by addition processing modulo 2.

Here, the PCM data recording area PC shown in FIG.
In the M, 128 blocks described above are arranged, and each subcode recording area SUB-1,
Eight blocks are arranged in each of the SUB-2s. As shown in FIG. 8, for the ID code part W1 and the block address part W2 of the blocks in the subcode recording areas SUB-1 and SUB-2, even-numbered blocks (blocks having block numbers 0, 2, 4, and 6) ) BLev and odd-numbered blocks (blocks with block numbers 1, 3, 5, and 7)
The content is different from BLod. In the even-numbered block BLev, a 4-bit control ID and a 4-bit data ID are provided in 8 bits of the ID code section W1, and the first bit in the 8 bits of the block address section W2 is “1”.
The format ID is allocated to the next three bits, and the block address is allocated to the next four bits. Also,
The ID code part W1 and the block address part W2 in the odd-numbered block BLod have 4 bits, 4 bits and 3 bits, respectively.
Bit program numbers PNO-2, PNO-3 and PNO-1 are sequentially arranged, and a bit “1” is placed between PNO-3 and PNO-1 to indicate that PN
A 4-bit block address is allocated after O-1.

Further, as shown in FIG. 8, a start ID bit STR-ID, a skip ID bit SKP-ID, and the like are recorded in a 4-bit control ID in the even-numbered block BLev. For example, a start ID bit ST for about 9 seconds is provided at the beginning of a program such as a music song.
The R-ID is recorded as "1", so that the beginning of a song or a program search can be effectively performed.

[0009]

By the way, the magnetic tape 1 recorded on the basis of such a recording format.
(See FIG. 6), for example, when a search is performed at a high speed of 200 times, the error rate is extremely low, and it is extremely difficult to read out the control signal such as the start ID. If the start ID is not accurately read, the beginning of the music cannot be effectively performed.

The present invention has been made in view of such circumstances, and enables a highly reliable reading of a control signal such as a start ID even when an error rate is low such as in a high-speed search. It is intended to provide a simple signal detection device.

[0011]

In order to solve the above-mentioned problems, a signal detecting apparatus according to the present invention is provided with a reproducing means for reproducing a reproducing signal from a recording medium, and a reproducing signal from the reproducing means. Signal processing means, search control means for performing search control of the reproduction means in a search mode, and system control means for controlling operations of the reproduction means, signal processing means, and search control means. Among the control signals read n times (n is an integer of 2 or more) within a series of recording ranges of the recording medium, k times (k
≦ n) is detected as a predetermined control signal, and it is determined that the predetermined control signal is reliably recorded.

Here, the system control means includes the above-mentioned n
Of the control signals read out twice, the predetermined control signal and the one without error are detected k times or more, and the remaining control signals without error are j or less, and It is preferable to determine that the control signal has been reliably detected.

Only when k readings have been correctly read out of the past n readings is determined to be a predetermined control signal, for example, a start ID signal.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a signal detection device according to the present invention will be described with reference to the drawings.

FIG. 1 is a flowchart for explaining the operation of the signal detection device according to the embodiment of the present invention.
FIG. 2 is a plan view showing a head trajectory with respect to a track on a tape at the time of high-speed search, and FIG. 3 is a block diagram showing an example of a signal reproducing system to which the signal detecting device according to the embodiment of the present invention is applied. . In this embodiment, a start ID signal in a so-called R-DAT, which is a digital audio tape recorder of a rotary head system, is used, for example.
This is applied to a case where detection is performed in a high-speed search mode of about 00 times speed.

As shown in FIG. 3, the signal detecting device according to the embodiment of the present invention is a mechanical system as a reproducing means for reproducing a reproduced signal by driving a magnetic tape as a recording medium and a reproducing head. 11, a digital signal processing circuit 13 which is a signal processing means to which a reproduced signal from the mechanical system 11 is supplied via a head amplifier 12, a search control circuit 15 for performing search control of the mechanical system in a search mode,
It has a mechanical system 11, a digital signal processing circuit 13, a search control circuit 15, and a system controller 17 which is a system control means for transmitting and receiving signals and controlling operations. The system controller 17 determines that k times (k ≦ n) out of n (n is an integer of 2 or more) control signals detected in the past in a series of recording ranges of the recording medium are predetermined control signals. When it is determined that the signal is a certain start ID signal, it is determined that the signal is the head of a program such as a song. Regarding the operation of the system controller 17,
This will be described first with reference to FIG.

In FIG. 1, in step S1 immediately after the start ID search is started, a variable t indicating a kind of time, which will be described later, according to the number of times the start ID is detected is set to 0. A signal is read out according to the search. In this step S2, the start ID bit STR-ID and the flag P-FLG indicating the result of the parity P determination in the subcode recording area are read and assigned to the array variable DT (t). At this time, t of the array variable DT (t) is the start ID bit STR-ID.
Is used as a kind of time display value that advances in accordance with the passage of time such that it is incremented by one each time a sub-code having a sub-code is detected. The value of the array variable DT (t) is, for example, the first bit is the start ID bit STR-
The ID and the second bit are represented by a 2-digit binary number corresponding to the flag P-FLG, respectively.

Next, in step S3, both the variable Kc for counting and the variable i are set to 0, and the process proceeds to the next step S4. In step S4, the array variable D
It is determined whether the value of T (t−i) is (1, 0). That is, if the start ID bit STR-ID is "1" to indicate the head position of a program such as a song, and at the same time the flag P-FLG is "0" and there is no error, step S4 Is determined as YES, and the process proceeds to the next step S5. If these conditions are not satisfied at the same time, NO is determined in step S4, and the process proceeds to step S6. In step S5, the counting variable Kc is incremented by 1 (Kc = Kc + 1), and the process proceeds to the next step S6.

In step S6, the start I
A variable i indicating the number of times the D-bit STR-ID is detected is incremented by 1 (i = i + 1), and the process proceeds to the next step S7 to determine whether or not the variable i is equal to the predetermined value n. NO
In the case of, the process returns to step S4, and the array variable DT
The value of (t−i) is sequentially determined, the counting operation using the variable Kc is advanced according to the determination, and the process is repeated until i becomes n.

When YES is determined in step S7, the process proceeds to the next step S8, in which it is determined whether or not the counting variable Kc is equal to or larger than k. If YES is determined in this step S8, the process proceeds to step S9.
Then, the detected signal is determined to be the start ID without fail, and the process proceeds to the next step S11. If NO, the process proceeds to step S10, where it is determined that the detected signal is not the start ID, and the process proceeds to the next step S11. In step S11, after the variable t is incremented by one (t = t + 1), the process returns to step S2.

Here, when the above-described high-speed search operation is performed, a head locus HT is drawn on an oblique recording track TR on a magnetic tape, for example, as shown in FIG. A in FIG. 2 corresponds to fast forward, and B corresponds to rewind. The above-described subcode recording areas SUB-1 and SUB-2 in which the start ID bit STR-ID is recorded are disposed slightly from both side edges in the effective recording width Wa of the magnetic tape shown in FIG. With one scan of the head,
Sub-code reading is performed twice corresponding to the sub-code recording areas SUB-1 and SUB-2. That is, as described with reference to FIG. 8, each area SUB-1 and SUB-2 is provided with eight blocks, and the start ID bit STR-ID is recorded in each of the even-numbered four blocks. However, these four start ID bits STR-
By taking majority decision of ID, etc., the above start ID detection is
1 for each subcode recording area SUB-1 or SUB-2
I'm going every time. Therefore, one of the two-head rotating drum
During rotation, start ID detection is performed four times. However, since the start ID bit STR-ID becomes "1" for about 9 seconds at the beginning of a program such as a song, the ID bit "1" is confirmed only for 9 / N seconds when reading at N-times speed. I can't. By the way, the applicant has previously filed Japanese Patent Application
Japanese Patent Application Laid-Open No. 9-232077 proposes a technique for controlling the rotation of a rotary drum so that the relative speed of a rotary head with respect to a magnetic tape is the same as during normal (normal) playback even during variable speed playback such as high-speed search. doing. In consideration of applying a servo for keeping the relative speed between the head and the tape constant, the number of times that the data can be read while the start ID bit STR-ID in the subcode is "1" during N-times playback. m is approximately given by the following equation.

M = | 3 + 1200 / N | where N is positive during fast-forward and negative during rewind, -200 ≦ N ≦ 20
Set to 0.

Accordingly, the number m of readable data at the time of fast forward in the high-speed search mode at 200 × speed is 9, and m at the time of rewinding is 3. At 150 × speed, m during fast forward is 11 and m during rewind is 5, and at 100 × speed, m during fast forward is 15 and m during rewind is 9. As described above, the number m of times that the start ID bit “1” can be read is limited, and the error rate is generally poor. Therefore, k or more of the past n read data as described above are valid start times. Only when the ID can be confirmed, the start ID is reliably recorded, and it is determined that it is the beginning of a program such as a song, thereby preventing deterioration of reliability.

A specific example of the configuration of a signal reproducing system for performing such an operation will be described with reference to FIG.

In FIG. 3, a reproduction signal from a mechanical system 11 of a digital audio tape recorder (DAT) including a rotary head device, a tape running system, a tape cassette and the like is transmitted via a so-called head amplifier 12 including a reproduction equalizer circuit and the like. , To the digital signal processing circuit 13. Further, a clock signal is extracted from an output signal of the head amplifier 12 by a clock reproducing circuit 14 using a PLL circuit or the like, and the clock signal is sent to a digital signal processing circuit 13 and a search control circuit 15. The digital signal processing circuit 13 is a circuit section for performing error correction processing, subcode decoding processing, D / A conversion processing, and the like. The analog signal is output from the output terminal 16 and the subcode signal is output from the output terminal 16. It is supplied to a system controller 17 using a microprocessor or the like. The search control circuit 15 is supplied with not only the clock signal from the clock reproduction circuit 14 but also a signal from the head amplifier 12, and further transmits and receives information to and from the system controller 17. In the search mode, the search control circuit 15 controls a servo drive circuit such as a drum motor of the rotary head of the DAT mechanical system 11 and a reel motor control circuit based on these signals, thereby performing a search operation. Here, in the case of using the technique described in Japanese Patent Application No. 59-232077, the search control circuit 15 sets the relative speed between the tape and the rotary head to be the same as that during normal (normal) reproduction. A drum motor, a reel motor, and the like are controlled.

As described above, the start ID bit in the subcode signal and the error flag by the parity check are sequentially read out while keeping the relative speed between the tape and the head constant even during the high-speed search. If it is correctly read, it is determined that the start ID is reliable. Here, for example, when n = 5 and k = 3, it is assumed that the following data string is obtained as an example. Start ID hit ・ ・ ・ 0 0 1 1 0 0 1 0 1 1 0 0 ・ ・ ・ Error flag ・ ・ ・ 0 1 0 0 1 0 0 1 0 1 1 0 ・ ・ ・ In the example of this data string, the third Looking at the results of the fifth to seventh detections, since there are three sets of (0,1), this is definitely determined to be the start ID. Note that, in the five detection results from the seventh to eleventh times, the start ID bit is "1" three times, but of those, the flag is "0", that is, no error is detected twice. There is no start ID.

As described above, by determining that the start ID is a reliable start ID only when k or more times out of n times are correctly read, high reliability can be obtained even when the error rate is low as in a high-speed search. The start ID can be detected below. For example, even under bad conditions with an error rate of 10% or more and an erroneous detection rate of several% or more, the probability of missing a start ID is about once per 500 songs, and the probability of false detection of a start ID is 0.1 per tape. Excellent results were obtained in the order of times.

Next, another embodiment of the control signal detecting method according to the present invention will be described with reference to FIG.

In the example of FIG. 4, not only k or more of the past n detection results are correctly detected as start IDs (error flag is 0) as in the above-described embodiment, but also Further, almost all of the remaining detection results are determined to have an error, and only when the number of error flags 0 (no error) is j or less, the start ID is reliably determined to be present.

Here, steps S21 to S25 in FIG. 4 substantially correspond to steps S1 to S5 in FIG. That is, step S2
In step 1, the variable t for the type of time indication is set to 0, and in the next step S22, the read data (the start ID bit STR-ID and the flag P-FLG indicating the discrimination result of the parity P) are stored in the array variable DT ( t). Next, the process proceeds to step S23, where the variables Ka and Kb for counting and the variable i are all set to 0, and the process proceeds to the next step S24. In step S24, similar to step S4 in FIG. 1,
It is determined whether or not the value of the read data DT (ti) is (1, 0). If YES, the flow advances to the next step S25 to increment the counting variable Ka (Ka = Ka + 1).
Then, the process proceeds to the next step S26. NO in step S24
When it is determined that the DT
It is determined whether or not the value of (ti) is (0,0). That is, the start ID bit is “0” and the error flag is 0.
When there is no error, it is highly likely that the start position is not at the start position. Therefore, in step S27, Y
In the case of ES, the process proceeds to step S28 to increment the count variable Kb (Kb = Kb + 1), thereby counting the number of times (0,0) is detected, and then proceeds to the next step S28.
It is proceeding to 26. When it is determined NO in step S27, the process proceeds directly to step S26.

In step S26, the variable i is incremented by 1 (i = i + 1), and the flow advances to the next step S29 to determine whether or not the variable i is equal to the predetermined value n. If the determination is NO, the process returns to step S24 to sequentially determine the value of the array variable DT (t−i), proceeds with the counting operation using the variables Ka and Kb according to the determination, and repeats until i becomes n. . When YES is determined in the step S29, the process proceeds to the next step S30, and it is determined whether or not the counting variable Ka is equal to or larger than the k. When YES is determined in step S30, the process proceeds to step S31, and it is determined whether or not the counting variable Kb is equal to or less than the predetermined value j. Only when YES is determined in step S31, step S32 is performed.
Then, after it is determined that the detected signal is the start ID, the process proceeds to the next step S34. On the other hand, when NO is determined in the step S30 or NO in the step S31, the process proceeds to a step S33, where it is determined that the read signal is not the start ID, and the next step S34 is performed. Proceed to. In step S34, after the variable t is incremented by one (t = t + 1), the process returns to step S24.

By this operation, k or more of the past n detection results are correctly detected as the start ID (no error), and no error is detected among the remaining detection results (the flag is “0”). Nevertheless, only when the number of items that do not indicate the start ID (the bit is “0”) does not exceed j, it is reliably determined that there is a start ID, and the start ID can be detected with higher reliability. this is,
In the section with the start ID, (1,0) should be obtained as data, but if an error occurs, (0,1),
(1,1), (0,0) are also obtained. However, almost certainly an error flag is set to "1" (error detection is performed) when the error has occurred for the probability P _M of data (0, 0) is obtained is very small. Therefore, when (0,0) is obtained as many as j times, it should be determined that the section has no start ID. This way, the probability of missed, because come P _M ^j Dekiite, miss probability decreases remarkably, and by this effect, it is possible to reduce the n.

It should be noted that the present invention is not limited to only the above-described embodiment. For example, the R-DAT start I
The present invention can be applied to various control signal detections other than the D detection.

[0034]

According to the signal detecting device of the present invention, the operation of the reproducing means for reproducing the reproduced signal from the recording medium, the signal processing means for processing the reproduced signal, and the search control means for performing search control of the reproducing means are controlled. The control signal read from the recording medium is read by the system control means only when k times are correctly read out of the past n times read results.
Since it is determined that the signal is a predetermined control signal, for example, a start ID signal, it is possible to detect a control signal such as a start ID signal while maintaining high reliability even under a condition with a low error rate such as a high-speed search. Become.

[Brief description of the drawings]

FIG. 1 is a flowchart for explaining a start ID detection operation in a signal detection device according to an embodiment of the present invention.

FIG. 2 is a plan view showing a head trajectory with respect to a track on a tape during a high-speed search.

FIG. 3 is a block diagram illustrating an example of a signal reproduction system to which the signal detection device according to the embodiment is applied.

FIG. 4 is a flowchart for explaining the operation of another embodiment of the present invention.

FIG. 5 is a diagram showing an example of a track format in a rotary head type digital audio tape recorder.

FIG. 6 is a diagram showing an example of a tape recording format in a rotary head type digital audio tape recorder.

FIG. 7 is a schematic diagram showing a schematic configuration of a rotary head device.

FIG. 8 is a diagram showing a format of one block in the track format.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetic tape 2 Rotating drum 3a, 3b Rotating magnetic head 11 Mechanical system of DAT 12 Head amplifier 13 Digital signal processing circuit 14 Clock reproduction circuit 15 Search control circuit 17 System controller

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-168961 (JP, A) JP-A-60-253050 (JP, A) JP-A-50-702 (JP, A) JP-A 50-1985 151403 (JP, A) JP-A-51-73372 (JP, A)

Claims (2)

(57) [Claims] 1. A signal detecting device for detecting a control signal recorded over a series of recording ranges of a recording medium at a high speed, comprising: a reproducing means for reproducing a reproducing signal from the recording medium; and a reproducing signal from the reproducing means. Signal processing means, a search control means for performing search control of the reproduction means in a search mode, and a system control means for controlling operations of the reproduction means, the signal processing means, and the search control means. The system control means detects k times (k ≦ n) as a predetermined control signal among the control signals read n times (n is an integer of 2 or more) in a series of recording ranges of the recording medium. A signal detection device that determines that the predetermined control signal is recorded reliably. 2. The system control means detects, among the control signals read out n times, a signal which is the predetermined control signal and has no error, more than k times, and further detects an error in the remaining control signals. 2. The signal detecting device according to claim 1, wherein when there are no j signals or less, the predetermined control signal is determined to be reliably detected.