JP3331845B2 - Tape playback 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 tape reproducing apparatus such as a digital VTR for recording and reproducing a digital information signal such as a video and audio signal including at least a pilot signal for tracking control on a magnetic tape.

[0002]

2. Description of the Related Art A helical scan type tape reproducing apparatus in which information signals including video and audio signals are all digital signals, in which a pilot signal for tracking control is recorded on a track together with an information signal. A conventional technique for a reproducing apparatus will be described.

In recent years, high-density recording on a magnetic tape has become possible, and long-term recording has been realized by reducing the tape running speed and narrowing the track pitch. Further, in a tape reproducing apparatus in which the video / audio signal is a digital signal, an attempt is made to realize a longer recording time by a signal compression technique. As an example of long-time recording combining such a signal compression technique, information is compressed (for example, １ ／), and the number of tracks to be recorded is reduced according to the compression ratio (when the compression ratio is 数, the number of tracks is reduced). Is also halved). In this method, for example, one frame of a digital video / audio signal that has been divided into ten tracks and recorded is compressed to し, and one frame is divided into five tracks and recorded. A method for reducing the number of recording tracks to half in this manner will be described with reference to the drawings. FIG.
Shows an example of a magnetic head configuration of a rotating cylinder during normal recording. FIG. 3 shows a track pattern per unit time when normal recording is performed with the magnetic head configuration of FIG. FIG. 4 shows a track pattern per unit time during long-time recording, which is half the number of tracks per unit time during normal recording shown in FIG. One method of realizing the track pattern shown in FIG. 4 is to provide a magnetic head for long-time recording as shown in FIG. 5 and record one track per rotation cylinder circumference (for example, see FIG. 5). Kaihei 7-3720
No. 9).

In such a helical scan type tape reproducing apparatus, tracking control of a capstan for running a magnetic tape is required in order for a magnetic head to accurately scan a track. As an example of a method for implementing this tracking control, as shown in FIGS. 3 and 4, three types of pilot signals f0, f1, and
There is a method of recording f2 on a track together with an information signal. The pilot signals f1 and f2 are relatively low frequency signals that are hardly affected by azimuth loss, and the pilot signal f0 indicates that the pilot signals f1 and f2 are not recorded. In such a magnetic tape tape reproducing apparatus, when a track on which the pilot signal f0 is recorded is scanned, the pilot signals f1 and f2 recorded on the adjacent tracks are detected as crosstalk components. The tracking control is realized by controlling the speed of the capstan so that the difference between the magnitudes of the frequency components, i.e., the tracking error, becomes zero.

[0005]

The above-described tracking control in the conventional tape reproducing apparatus generally has low response, which causes a delay in output of normal video and audio. In particular, during long-time recording by information compression, the response speed of the magnetic tape is reduced because the running speed of the magnetic tape is reduced, and the number of times of scanning the track on which the pilot signal f0 is recorded is also reduced. , The responsiveness of the tracking control also decreases, so that the output of normal video and audio is further delayed.

Also, two types of pilot signals f1 and f2
When the tracking control is performed by creating a tracking error signal from the tracking error signal, the positional relationship between the tracks on which the pilot signals f1 and f2 exist differs depending on the track being scanned. Normal tracking control cannot be performed unless the polarity of the tracking error signal used for tracking control is switched in accordance with the track on which the tracking error signal is detected.

The present invention solves the above problems,
An object of the present invention is to improve the pull-in speed of tracking control during long-time recording and to speed up the output of normal video and audio. Another object of the present invention is to prevent the malfunction of the tracking control by outputting the correct polarity of the tracking error signal.

[0008]

In order to solve the above-mentioned problems, a tape reproducing apparatus of the present invention has at least one set of magnetic heads having different azimuth angles on a rotating cylinder, and performs tracking control. When reproducing a magnetic tape on which an information signal including a pilot signal for recording is recorded as a skew track, the magnetic head is run and n times (n ≧ 2 integer) scans of the magnetic head are performed for one time.
The information signals are reproduced in a predetermined order at a rate of times, and the order of magnetic heads used for reproduction is changed according to a tracking error signal created from a pilot signal detected from the reproduced information signal.

Further, when the reproducing order of the magnetic head is changed, the polarity of the tracking error signal used for tracking control is switched according to the detected polarity of the tracking error signal.

[0010]

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic tape on which an information signal including a pilot signal for tracking control is recorded as a skew track, and the magnetic tape is wound around a rotary cylinder. In the above tape reproducing apparatus for reproducing the magnetic tape by the magnetic heads having different azimuth angles, the magnetic tape is run, and the magnetic head is moved at a predetermined rate of n times (n ≧ 2 is an integer) once. The order of magnetic heads used for reproduction is changed in accordance with a tracking error signal created from the pilot signal detected from the reproduced information signal, and the same magnetic head is used twice. By continuously scanning the tracks, the tracking error signal can be reduced, and the capstan Control only than by the tracking control can be completed pull tracking control in a short time.

An embodiment of the tape reproducing apparatus according to the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram illustrating a configuration of a tape reproducing device according to an embodiment of the present invention. In FIG. 1, a magnetic tape 1 includes a video signal at the time of recording, a pilot signal for at least tracking control, and a mode signal indicating a recording time of a standard recording mode or a long-time recording mode (hereinafter, referred to as a recording signal).
MODE). The rotary cylinder 2 has a magnetic head 3 (L) having a positive azimuth;
Magnetic head 4 (R) for the standard recording mode having a negative azimuth and magnetic head 5 for the long-time recording mode
(R ′) are arranged as shown in FIG. The reproduced signals output from the magnetic heads 3 to 5 are amplified by the amplifiers 6 to 8, respectively, and output to the head selecting means 9. The head selecting means 9 includes a head switching signal (hereinafter abbreviated as HID) and MODE input from the signal processing means 10 and a head switching signal (hereinafter LHID) for a long-time recording mode input from the head switching means 11. , The magnetic heads 3 to
5 to select one of the reproduced signals and outputs it to the signal processing means 10.

The cylinder speed detecting means 12 includes a magnetic head position signal (hereinafter abbreviated as YPG) indicating a reference of a magnetic head position of the rotary cylinder 2 and a rotation speed signal (hereinafter, referred to as YPG) proportional to the rotation cycle of the rotary cylinder 2. YFG), and pulse waveform shaping and output. The signal processing means 10 detects a pilot signal and a MODE from the reproduced signal input from the head selecting means 9,
YPG and YF input from the cylinder speed detecting means 12
Create HID from G. Further, a tracking error signal (hereinafter abbreviated as TRE) is created from the detected pilot signal, HID and MODE are output to the head selecting means 9, HID and TRE are output to the head switching means 11, and the motor control means 13 is output. Output HID, MODE, and TRE. The head switching means 11 switches from HID to LHID
If the size of the TRE is larger than a predetermined value, the output of the TRE is outputted to the head selecting means 9 without inverting the logic of the LHID.

The motor control means 13 includes the signal processing means 10
And Y output by the cylinder speed detecting means.
The rotation speed control and the phase control of the rotary cylinder 2 are performed by the FG. A tape speed detecting means 16 for detecting a rotation speed signal proportional to the rotation cycle of the capstan 14 for running the magnetic tape 1, that is, a signal proportional to the running speed of the magnetic tape 1 (hereinafter abbreviated as AFG) is output. AFG and TRE and MOD output by the signal processing means 10
E controls the running speed and tracking of the magnetic tape 1. At this time, the motor control means 13 sets a TR
The tracking control is performed by switching the polarity of E. This P
OL is switched by the head switching unit 11 in accordance with the POL logic at that time when the head switching unit 11 determines that the magnitude of the TRE is larger than the predetermined value.

A method of reproducing a signal on the magnetic tape 1 according to the present embodiment having the above-described configuration will be described. FIG. 3 is a schematic diagram showing a track pattern of the magnetic tape 1 in the standard recording mode, and FIG. 4 is a schematic diagram showing a track pattern of the magnetic tape 1 in the long-time recording mode. FIG. 5 is a schematic diagram illustrating the mounting positions of the magnetic heads 3 to 5 mounted on the rotary cylinder 2. 3 and 4, the oblique lines drawn on the tracks and the magnetic head indicate the information signals recorded on each track and the azimuth angle of the magnetic head.

In FIG. 5, the magnetic head 3 (L) has a positive azimuth angle, and the signal recorded on the magnetic tape is determined by the standard recording mode or the long-time recording mode. Instead, a track signal recorded by a magnetic head having plus azimuth is reproduced. The magnetic head 4 (R) has a negative azimuth angle, and reproduces a track signal recorded by the magnetic head having a negative azimuth in the standard recording mode. Specifically, in the track pattern of the magnetic tape 1 in the standard recording mode shown in FIG.
For each rotation of the magnetic heads 3 and 4, one track each,
That is, the signal of the magnetic tape is reproduced at a rate of two tracks per one rotation of the rotary cylinder 2. The magnetic head 5 (R ') has the same negative azimuth angle as the magnetic head 4, and reproduces a track signal recorded by the magnetic head having the negative azimuth in the long-time recording mode. Specifically, in the track pattern of the magnetic tape in the long-time recording mode shown in FIG. 4, the magnetic heads 3 and 5 alternately make one track for each rotation of the rotary cylinder 2, that is, for each rotation of the rotary cylinder 2, The signal of the magnetic tape 1 is reproduced at a rate of one track.

The operation of the tape reproducing apparatus for reproducing the signal of the magnetic tape 1 as described above will be described in detail. First, the operation of the signal processing unit 10 according to the present embodiment will be described in detail. FIG. 6 is a principle diagram for explaining the tracking control, and FIG. 7 shows an example of the tracking error signal. The TRE creation method of the signal processing means 10 will be described with reference to FIGS.

In FIG. 6, f1 and f2 indicate that pilot signals f1 and f2 having different frequencies are recorded on tracks in a manner redundant to the video and audio signals. f0 indicates that neither pilot signal f1 nor f2 is recorded. The magnetic head 3
When (L) scans, the pilot signals f1 and f2 recorded on the adjacent tracks are reproduced as crosstalk, and the difference between the magnitudes of the components is detected as an analog signal as shown in FIG. This analog signal represents a deviation between the center of the track and the head scanning, and is realized by a head switching means 1 implemented by a program of a microcomputer (not shown).
1 and is output to the motor control means 13 as digital data. The digital data is converted into 8-bit digital data by an A / D converter (not shown) and output as a tracking error signal TRE.

Here, the tracking control of the motor control means 13 will be described. The tracking control is control for causing the magnetic head to scan the center of the track, and performs control so that the TRE becomes zero. In FIG. 6, when the magnetic head 3 scans between the center of the track 0 and the center of the track A, as shown in FIG. 7, a positive value from 00h to 7Fh (h means a hexadecimal number) as TRE. Is output. This indicates that the traveling of the magnetic tape 1 is advanced with respect to the scanning of the magnetic head 3, so that if the traveling speed of the magnetic tape 1 is reduced, the TRE approaches 00h. Conversely, when the magnetic head 3 scans between the center of the track 0 and the center of the track B, as shown in FIG.
Negative values from h to 81h are output. This indicates that the traveling of the magnetic tape 1 is delayed with respect to the scanning of the magnetic head 3, so that if the traveling speed of the magnetic tape 1 is accelerated, the TRE approaches 00h.

However, even when the magnetic head 3 scans between the center of the right track 0 'and the center of the track A in FIG. 6, as shown in FIG.
A positive value from h to 7Fh is output. This is TR
As described above, the value of E is such that the magnetic head 3
Is equal to the case where scanning is performed between the center of the track A and the center of the track A. However, since the running of the magnetic tape 1 is delayed with respect to the scanning of the magnetic head 3, the running speed of the magnetic tape 1 is If T is accelerated, the TRE approaches 00h. Therefore, before the magnetic head 3 reproduces the information signal, the magnetic head 4 or the magnetic head 5 determines whether the track on which the pilot signal f1 or the pilot signal f2 is recorded is reproduced, and the TRE used for the tracking control. Must be switched.

That is, since the pilot signals f1 and f2 are recorded alternately, the motor control means 13 performs tracking control by switching the polarity of the TRE every time the rotary cylinder 2 makes one rotation. When a track on which the pilot signal f1 is recorded is reproduced, a negative value is output as the TRE, and when a track on which the pilot signal f2 is recorded is reproduced, a positive value is output as the TRE. Therefore, the motor control means 13 controls the magnetic head 4
Alternatively, the polarity of the TRE can be determined based on whether the value of the tracking error signal detected from the information signal reproduced by the magnetic head 5 is positive or negative. The motor control means 13
A POL that takes two values of “H” and “L” is provided therein. This POL is used when the value of the tracking error signal detected from the information signal reproduced by the magnetic head 4 or the magnetic head 5 is positive. The value is set to 'H', and to 'L' in the case of a negative value. That is, when this POL is “L”,
The correct tracking control is performed by switching the polarity of.

FIG. 8 shows the timing of HID creation by the signal processing means 10 and the LHID of the head switching means 11 described later.
FIG. 4 is a signal waveform diagram showing a creation timing. In FIG. 8, YPG is a reference signal indicating the mounting positions of the magnetic heads 3 to 5 mounted on the rotary cylinder 2, and one pulse is output every time the rotary cylinder 2 makes one rotation. YFG is a signal proportional to the rotation cycle of the rotary cylinder 2, and four pulses are output each time the rotary cylinder 2 makes one rotation. HID is a head switching signal indicating the switching timing of the magnetic heads 3 to 5, and is a binary signal of 'H' and 'L'. The HID changes from "L" to "H" with a delay of a predetermined time DT1 from the rising edge of YFG following the rising edge of YPG. And
After 1/2 rotation of the rotary cylinder 2, that is, from the rising edge of YFG two pulses later, it changes from "H" to "L" with a delay of a predetermined time DT2. Here, DT1 is for the magnetic head 3 or the magnetic head 5, DT2 is for the magnetic head 4,
DT3 is a time determined by the mounting position of the magnetic head 5 from the rising edge of YPG.

The magnetic heads 3 to 5 are rotated by the rotary cylinder 2.
DT1, DT2, DT
By adjusting 3, HID can be corrected. DT3 is DT1 and DT2 only when the LHID created by the head switching means 11 described later is "L".
Is added to Next, the operation of the head switching means 11 in the present embodiment will be described in detail.

In FIG. 8, LHID is a head switching signal indicating which of the magnetic head 3 and the magnetic head 5 performs reproduction when reproducing a signal from the magnetic tape recorded in the long-time recording mode. This is a binary signal of “H” and “L”. This LHID is created by dividing the HID output by the signal processing means 10 by two. FIG. 9 is a flowchart showing the processing of a head switching routine of a microcomputer (not shown) for realizing the head switching means 11. This head switching routine is realized by an external interrupt routine of the microcomputer, and is executed each time a falling edge of HID is input to the microcomputer.

In FIG. 9, the LHID flag is a 1-bit flag set on the memory. When the falling edge of the HID is input and the head switching routine is executed, the logic of the LHID flag is determined (step 90).
1) If "L", proceed to step 908; if "H", store the TRE value input from the signal processing means 10 in the memory (step 902). In step 903, it is determined whether or not the TRE is greater than 40h, that is, whether or not the center of the magnetic head 3 is on the track A in FIG.
OL is set to 'H' (step 904), and the process proceeds to step 908, and if smaller, the process proceeds to step 905. In step 905, whether TRE is smaller than C0h,
That is, it is determined whether or not the center of the magnetic head 3 is on the track B in FIG. 6, and if it is smaller, the POL in the motor control means 13 is set to "L" (step 90).
6), go to step 908; if larger, go to step 90
Go to 7. In step 907, the logic of the LHID flag is inverted, and the flow advances to step 908.
LHID is output according to the logic of the HID flag, and the process ends. That is, if the LHID flag is 'H', 'H' is output as LHID, and if the LHID flag is 'L', 'L' is output as LHID.

Next, the operation of the head selecting means 9 in this embodiment will be described in detail. FIG. 10 is a circuit diagram showing a configuration example of the head selection means 9 shown in FIG. 1. FIG. 11 shows a signal waveform diagram of each part. In FIG. 10, a switch 18 selects a magnetic head for reproducing an information signal according to a switch switching means 19 (selects a signal from the magnetic head). Switch switching means 19
Creates a signal for selecting a magnetic head for reproducing an information signal from three signals of MODE, HID, and LHID, and switches the switch 18.

In FIGS. 10 and 11, MODE is a binary signal of "H" and "L" indicating whether the recording time mode is the standard recording mode or the long-time recording mode. Is output, and if the recording time mode is the long time recording mode, 'L' is output.
When the recording time mode is the standard mode, a reproduction signal from the magnetic head 3 (L) is output when HID is “H”, and a reproduction signal from the magnetic head 4 (R) is output when HID is “L”. You. Since the cycle of HID is the same as the cycle of the rotary cylinder 2, the magnetic heads 3 and 4 are each performed once per rotation of the rotary cylinder 2, that is, the magnetic heads 3 and 4 are each performed once in one scan. Thus, the signal of the magnetic tape 1 is reproduced. When the recording time mode is the long recording mode, the magnetic head 3 (L) or the magnetic head 5 when the HID is “H”.
A reproduction signal according to (R ') is output, and when the HID is "L", no reproduction signal from any magnetic head is output. Here, the reproduction signal from the magnetic head 3 or the magnetic head 5 is selected by the logic of LHID. When LHID is 'H', the reproduction signal from the magnetic head 3 (L) is output, and when LHID is 'L', the magnetic signal is output. Head 5
A reproduction signal according to (R ′) is output. Since the cycle of HID is the same as the cycle of the rotary cylinder 2 and the cycle of LHID is the same as the two cycles of the rotary cylinder 2, the magnetic heads 3 and 5 are turned on once for each turn of the rotary cylinder 2, that is, And the magnetic heads 3 and 5 reproduce the signal of the magnetic tape once every two scans.

As described above, in the tape reproducing apparatus according to the present embodiment for reproducing a signal recorded on the magnetic tape 1,
The method of pulling in the tracking control when the recording time mode is the long time recording mode will be described in detail. FIG.
(A) shows a head scan of the magnetic head 3 when the TRE is the largest, that is, a state where the magnetic head 3 (L) having a plus azimuth scans the track α recorded by the magnetic head having a minus azimuth. ing. At this time, in the next head scan, the track β is scanned by the magnetic head 5 (R ′).

In FIG. 12A, the head switching means 1
Reference numeral 1 indicates that the TRE is input from the signal processing means 10 when the magnetic head 3 is selected as the magnetic head for reproducing a signal. When the center of the magnetic head 3 scans the center of the track α and the TRE is 7Fh, it is determined in step 903 of FIG. 9 that the TRE is larger than 40h, and in step 908, the same value as the previous time is obtained. LHI
D is output. That is, LH that is switched from “H” to “L” or from “L” to “H” every falling edge of HID, that is, every rotation of the rotary cylinder 2.
As for ID, “H” is output while the rotary cylinder 2 makes two rotations. Therefore, as shown in FIG. 12B, the signal recorded on the track β is reproduced again by the magnetic head 3 following the reproduction of the signal recorded on the track α. At this time, since the center of the magnetic head 3 scans the center of the track β, the value of TRE becomes 00h, and the pull-in of the tracking control is completed instantaneously.

When the center of the magnetic head 3 scans the track α, that is, the track on which the pilot signal f2 is recorded, the position of the magnetic head 3 is changed to the track α.
The value of POL is set to “H” when the track is closer to the track β than the center, and is set to “L” when the track is farther. That is, the value of POL can take two values even when scanning on the same track α. However, if the POL is not “H” on the track β, correct tracking control cannot be performed. Therefore, the last POL
Regardless of the value, when the LHID having the same value as the previous time is output, by setting the polarity of the POL of the motor control means 13 to 'H' in step 904, correct tracking control can be realized.

In the above description, the information compression and tape speed are reduced to 1/2, and the information signal is reproduced once every two scans of the magnetic head (ie, n = 2). It may be changed depending on the compression ratio.
For example, when the information compression and the tape speed are 1/4, the information signal may be reproduced once every four scans (n = 4) of the magnetic head.

In the above description, four pulses of YFG are output for one rotation of the rotary cylinder 2.
Any number of pulses may be used as long as 1/2 rotation of the rotary cylinder 2 can be determined to create an ID. In the above description, MODE is recorded on the magnetic tape 1. However, any means may be used as long as the recording time information is known. For example, when an information memory is attached to the cassette, that memory may be used.

In the above description, the TRE is signed 8-bit data, but the size of the data may be set arbitrarily. Also, the head switching means 11 is LHI
TRE for determining whether to switch the logic of D
Is set to 40h or C0h, but may be set arbitrarily according to the data amount of the TRE.

[0033]

As described above, according to the present invention, a magnetic tape on which an information signal including a pilot signal for tracking control is recorded as a skew track is wound around a rotary cylinder, and the magnetic tape is placed on the rotary cylinder. In a tape reproducing apparatus that reproduces the magnetic tape by using at least one set of magnetic heads having different azimuth angles, a magnetic tape is driven to move the magnetic tape.
The information signal is reproduced in a predetermined order at a rate of one scan (an integer of n ≧ 2), and the same magnetic head is used in accordance with a tracking error signal generated from a pilot signal detected from the reproduced information signal. By scanning the track twice consecutively, the pull-in speed of the tracking control can be improved, and the time until normal video and audio output can be shortened. Further, by switching the polarity of the tracking error signal used for the tracking control in accordance with the polarity of the tracking error signal, malfunction of the tracking control can be prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a tape reproducing apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing an example of a magnetic head configuration in a standard recording mode and a conventional magnetic head configuration in the embodiment.

FIG. 3 is a schematic diagram showing an example of a track pattern of a magnetic tape in a standard recording mode and a track pattern of a conventional magnetic tape according to the embodiment;

FIG. 4 is a schematic diagram showing a track pattern of a magnetic tape in a long-time recording mode according to the embodiment;

FIG. 5 is a schematic diagram showing a configuration of a magnetic head in a long-time recording mode according to the embodiment;

FIG. 6 is a principle diagram of tracking control in the embodiment.

FIG. 7 is a schematic diagram of a tracking error signal in the embodiment.

FIG. 8 is a signal waveform diagram of a signal processing unit and a head switching unit in the embodiment.

FIG. 9 is a flowchart showing processing contents of a head switching unit in the embodiment.

FIG. 10 is a circuit configuration diagram of a head selection unit in the embodiment.

FIG. 11 is a signal waveform chart of a head selecting means in the embodiment.

FIG. 12 is a schematic diagram showing a head switching operation in the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetic tape 2 Rotating cylinder 3,4,5 Magnetic head 6,7,8 Amplifier 9 Head selecting means 10 Signal processing means 11 Head switching means 12 Cylinder speed detecting means 13 Motor control means 14 Capstan 15 Pinch roller 16 Tape speed detecting means

────────────────────────────────────────────────── (5) References JP-A-4-356715 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 15/467

Claims (2)

(57) [Claims] 1. A magnetic tape on which an information signal including a pilot signal for tracking control is recorded as a skew track is wound around a rotary cylinder, and at least one set of different azimuth angles mounted on the rotary cylinder is different from each other. In a tape reproducing apparatus that reproduces the magnetic tape by using a magnetic head having the following structure, an information signal is transmitted in a predetermined order at a rate of once every n (n ≧ 2 integer) scans of the magnetic head by running the magnetic tape. A tape reproducing apparatus that reproduces and changes the order of magnetic heads used for reproduction according to a tracking error signal created from a pilot signal detected from the reproduced information signal. 2. The method according to claim 1, wherein when changing the order of the magnetic head used for reproduction, the polarity of the tracking error signal used for tracking control is switched according to the polarity of the detected tracking error signal. Tape playback device.