JPS61265760A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To attain the accurate recording and the erasure of an index signal by recording or reproducing a signal having a frequency higher than the carrier frequency of an FM audio signal to a margin section as the index signal of the 1st information or the 2nd information. CONSTITUTION:The index signal is recorded to the margin section (c) of the 1st part of a track 2. In applying an index recording, the index signal is recorded on a magnetic tape with saturation. When the erasure of the index signal is commanded, an erasure signal having a prescribed frequency higher than that of the index signal generated from an oscillation circuit 26 is fed to a recording amplifier 22 via switches 21, 18 and recorded there, and in bringing the level of the erasure signal to a level corresponding to the optimum recording current, the erasure signal is recorded with saturation and the index signal is erased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording and reproducing apparatus for recording and reproducing information using a rotating magnetic head such as a video tape recorder.

[Summary of the invention]

In the present invention, a first portion and a second portion are formed on a track inclined with respect to the longitudinal direction of a magnetic tape by a one-rotation magnetic head, and at least the first portion further includes a portion a where a clock signal is recorded. The area where data such as PCM audio signals are recorded is divided into a margin area C for after-recording and a video overlap area d where the video signal of the immediately previous field is continuously recorded. In a magnetic recording and reproducing device that records or reproduces first or second information in a portion or a second portion.

At least in the second part, an FM audio signal obtained by frequency modulating a predetermined carrier with an audio signal can be multiplexed with the second information to be recorded or reproduced, and is generated in accordance with the rotational position of the rotating magnetic head. signal or first
Detecting the position of the margin part from the reproduction signal of the information, and recording or reproducing a signal of a higher frequency than the carrier of the FM audio signal in the margin part as an index signal of the first information or the second information, This makes it possible to record and erase index signals accurately and satisfactorily without the need for a special fixed head.

[Conventional technology]

2. Description of the Related Art In magnetic recording and reproducing devices such as video tape recorders, a tape counter is sometimes used to search for a predetermined recording or reproducing position. However, searching using a tape counter has the drawback of lacking accuracy. Therefore, a control signal (CTL signal) for tracking control, which is generally a 30 Hz rectangular wave signal obtained from a pulse generator of a rotating drum, is sometimes used for the search. Since the CTL signal only uses the timing of one edge for tracking, a signal with a changed duty can be used as a cue signal (cue signal or index signal) for position search. .

However, such a search method using CTL signals requires a fixed head placed corresponding to the track on which the CTL signal is recorded and an additional circuit around it. Like a video tape recorder, each track has a tracking pilot signal f1. f.

f, , f4 (for example, 6.5 f, , 7.5 f*
, 10.5f*, 9.5fs (fw is the frequency of the horizontal synchronization signal)), and basically cannot be used in equipment that does not require a CTL signal, but if adopted, it is basically necessary. A special fixed head, etc. without a A recording method is required, making the device complex and expensive. The frequency of the reproduction signal from the cue track is several tens of times higher during fast forwarding or rewinding than during normal recording and reproduction.

It is extremely difficult to extract an index signal for each track by processing significantly changing frequencies, periods, waveforms, amplitudes, etc. Furthermore, since the cue track is located near the edge of the magnetic tape, it is easily damaged by the tape guide.

The slanted track of an 8mm video tape recorder has
A first part in which first information is recorded and a second part in which second information is recorded are formed, and the first part further includes a part a in which a clock signal is recorded, a PGM audio signal, etc. There is a margin area C for after-recording, and a video overlap area d where the video signal of the previous field is continuously recorded.
The applicant previously proposed recording an index signal in this part d (Japanese Patent Application No. 59-2).
No. 77972 or Japanese Patent Application No. 60-2464).

However, when recording an index signal in such a video overlap part d, the recordable length is The maximum length is 0.8H (H is the horizontal scanning period), but when taking into account the margin for erasing, it has the disadvantage of being shortened to about 0.5H.

Therefore, in the worst case, the video signal recorded in the video overlap area d will be erased, and if the head switching signal exceeds the allowable range and fluctuates further toward the video overlap area d, the fluctuation will exceed the standard. However, since there is no margin at all, there is a drawback that a missing period occurs in the reproduced video signal.

[Problem that the invention seeks to solve]

Therefore, the present applicant further proposed recording and reproducing an index signal in the margin section C in Japanese Patent Application No. 60-27256. However, in this proposal, since the index signal has a relatively low frequency, it is difficult to erase the data sufficiently after it has been recorded, and there is a high risk of erroneous retrieval.

[Means for solving problems]

FIG. 1 shows a block diagram of the case where the magnetic recording/reproducing apparatus of the present invention is applied to a video tape recorder.

In the figure, reference numeral 11 denotes a rotating drum, into which a rotating magnetic head (not shown) for recording or reproducing is mounted. 1
2 is a motor that rotates the rotating drum 11. Reference numerals 13 and 14 denote a frequency generator and a pulse generator, respectively, which output signals of a frequency and phase corresponding to the rotation of the rotary drum 11, and the outputs thereof are supplied to a servo circuit 15. The servo circuit 15 outputs a rotation control signal to the motor 12 and also outputs a head switching signal (H5WP signal) for switching a plurality of rotating magnetic heads. This head switching signal is supplied to a pulse generation circuit 17 via a variable delay circuit 16 provided as necessary. The pulse generating circuit 17 generates a pulse for controlling the on/off of the switch 18. Reference numeral 19 denotes a control device consisting of a microcomputer or the like, and is adapted to control on/off of the switches 20 and 21. 22 is a recording amplifier that amplifies a signal supplied to a rotating magnetic head for recording or reproducing information. 23 is an index signal generation circuit, which supplies the index signal to the recording amplifier 2 via a switch 20.18.
It is supposed to appear in 2nd place. Further, 24 is an index signal detection circuit, which detects an index signal from the reproduction signal of the preamplifier 25.

An oscillation circuit 26 generates a reference signal of a predetermined frequency and outputs it to the index signal generation circuit 23. 27
is a position detection circuit, which detects the predetermined position of the rotary head from the reproduction signal supplied from the rotary head.

[Effect]

The operation thereof will be explained with reference to FIGS. 2 to 6. The recording amplifier 22 receives signals to be recorded, such as video signals, PCM audio signals, FM audio signals, and tracking pilot signals, through a video circuit (not shown),
The signals are supplied from a PCM circuit, an FM audio circuit, a tracking circuit, etc., and these signals are recorded on a magnetic tape by a rotating magnetic head. During this time, the servo circuit 15 compares the signals from the frequency generator 13 and the pulse generator 14 with a reference signal, and controls the rotation of the motor 12 in response to the error signal. During reproduction, the reproduction signal from the rotating magnetic head is amplified by the preamplifier 25 and supplied to the video circuit, PCM circuit, FM audio circuit, tracking circuit, etc.

FIG. 3 shows how signals are recorded on the magnetic tape in this manner. That is, tracks 2 are formed on the magnetic tape 1, which are inclined with respect to its longitudinal direction. For convenience, the track 2 includes a first part corresponding to a winding angle of about 36 degrees of the magnetic tape 1 with respect to the rotating drum 11, and a first part corresponding to a winding angle of about 18 degrees.
a second part corresponding to the fifth, and the former has a PC
M audio signal and tracking pilot signal (T
PS signal), and in the latter, an FM video signal, an FM audio signal, and a tracking pilot signal can be multiplexed and recorded. The azimuth angle of the corresponding rotating magnetic head is inclined by about 10 degrees in the positive direction on one side of the adjacent track 2 and in the negative direction on the other side, so that crosstalk from the track 2 that is in contact with the track 2 can be reduced. It has become. Near edge 3, I
An iH audio track 4 is formed, and a regular analog audio signal can be recorded by a fixed head if necessary. A cue track having a width C is formed near the other edge 3, and a cue signal is recorded by a fixed head as necessary. 5 and 7 are guard tracks provided between the information recording track and the control signal recording track.

4 shows one track 2 enlarged. That is, the first part further includes a part a where a clock signal is recorded, a part where data such as a PCM audio signal is recorded, and a margin part C for after-recording.
and a video overlap section d where the video signal of the immediately previous field is continuously recorded.

The end position of the portion d is the switching position of the rotary magnetic head, and the vertical synchronizing signal is located at a position separated by a distance e from there.

The length of each part of the table is 525 lines and 60 fields as in the case of the NTSC system, for example, and
For example, 625 lines as in the PAL system,
In a 50-field system, the settings are as shown in the table.

FIG. 5 shows a case where a plurality of parts corresponding to the first part are formed in the second part (part d can be considered to be included in the second part, but for convenience's sake, it is included in the first part). In other words, the length of the first part is an integral multiple of approximately five times the length of the second part, and five parts corresponding to the first part are formed in the second part. For example, a PCM audio signal, for example, is recorded in each of six parts in total, consisting of parts a to d.

Next, the recording and reproducing operation of the index signal will be explained. In the present invention, the index signal is recorded in the margin section C of the first section of track 2. The section C is NTSC.
For C method 3. OH (3.6H for PAL method)
It has a length of The servo circuit 15 obtains a predetermined delay time as necessary by counting predetermined clock pulses from the outputs of the frequency generator 13 and the pulse generator 14 corresponding to the rotation of the rotating drum 11, and switches the head. A signal is output (FIG. 2(a)). This signal is supplied to a pulse generation circuit 17 via a variable delay circuit 16 (the variable delay circuit 16 is not necessarily necessary if the track configuration is as shown in FIGS. 3 and 4). The circuit 17 operates when a predetermined period of time has elapsed since the head switching signal was generated (for example, in the case of the NTSC system, 256.
7 (262,5-3,8-3,0+1.0)H has elapsed), that is, at the timing when the recording section of the index signal of section C arrives (Fig. 2(b)).
, output a recording pulse of a predetermined width (for example, 1.5H), and turn on the switch 18 during that time (solid line in FIG. 2(c));
When the index recording operation is done manually or automatically, the control bag! ! 19 activates the pulse generation circuit 17 and turns on the switch 20 for a predetermined period of time (for example, 10 seconds) required to reproduce and detect the index signal. 2(d)) is the switch 20.18
(FIG. 2(e))
, such operation is performed for a predetermined time (10 seconds) required to reproduce and detect the index signal, so that track 2 where the index signal is recorded in part I
A predetermined number of lines (the number required to reproduce and detect the index signal) are formed. At this time, no bias signal is supplied to the recording amplifier 22, and the index signal is recorded in saturation on the magnetic tape. In this way, by recording the index signal at the highest possible level of saturation so as to obtain the maximum playback output, when detecting the index signal, it is possible to distinguish it from other signals other than the index signal such as FM video signal. The detection level of the index signal can be easily set, and the detection accuracy of the index signal can be improved.

If, for example, a PCM audio signal is recorded on all of one track 2 as shown in FIG. It will be done. In this case as well, since the basic timing is the same as in the cases shown in FIGS. 3 and 4, there is no need to provide any special circuit other than the variable delay circuit 16.

When commanded to erase the index signal, the control device 19
As in the case described above, the pulse generating circuit 17 is activated to output an erase pulse of a predetermined width at the timing when the recording part of the index signal of part C arrives, and the switch 18 is turned on during this time (see FIG. 2). C) dashed line),
The width of the erase pulse can be made equal to the width of the recording pulse, but in order to avoid omission of erase and to avoid erasing PCM data, the width of the erase pulse is set at a distance of, for example, 0.5H from the end of the section. It is preferable to extend the length of the recording pulse by 0.5H, for example, so that the end of the recording pulse coincides with the end of portion C.When an erase command is issued, the control device 19 , a time equal to or slightly longer than the time to turn on the switch 20 (10 seconds),
Turn on the switch 21. Therefore, an erasure signal (FIG. 2(f)) having a predetermined frequency higher than the index signal generated by the oscillation circuit 26 is supplied to the recording amplifier 22 via the switch 21.18 and is recorded (FIG. 2(g)). ), also in this case, no bias signal is supplied to the recording amplifier 22, but when the erase signal is set to a level corresponding to the optimum recording current, the erase signal is saturated and recorded, and the index signal is erased. Of course, if the level of the erasing signal is set higher than this level, the erasing effect of the index signal will be further improved.

In the above operation, a signal to control the switch 18 is generated using the head switching signal as a timing reference, so there is no error in the recording position on the magnetic tape during recording and playback, or information recorded on the first part. It is inevitable that the timing will deviate due to a time axis error between the information recorded in the second part and the information recorded in the second part. Therefore, when playing the first part, if at least a PCM audio signal is recorded there, the position detection The circuit 27 decodes the demodulated signal of the PCM audio signal, for example, a synchronization signal indicating the start of data, an arbitrarily determined specific data block address, etc., and uses the signal obtained as a timing reference to determine the start point or portion of portion C. (Fig. 2 (h)).

A signal indicating the recording position of the index signal may be generated in synchronization with this detection signal. Therefore, in this case, the pulse generating circuit 17 is configured to generate a signal indicating the recording position of the index signal when the PCM audio signal is recorded. Output to PC
When the M audio signal is not recorded, the output of the variable delay circuit 16 is used.

Turn on the switch 18 as a reference for each timing.

A recording pulse and an erasing pulse for controlling off are generated respectively. .

The relationship between the position detection signal, the recording pulse (recording area), and the erasing pulse (erasing area) with respect to the absolute position on the magnetic tape when recording and reproducing the index signal to the margin part C in this way is shown in Figure 6. Figure 6i (a) shows the case where there is no time axis error in the recording special number, Figure 6 (b) shows the case where there is no time axis error during t± playback, and Figure 6 (Q ) is a time axis error force of 1+1° at the time of recording, a time axis error at the time of playback of 5H1 of -1,
Each represents the worst case of 5H. It can be seen that even in the worst case, the length of the video overlap portion d is approximately 0°8H.

On the other hand, as in the conventional case, for example, the video overlap part d
When the index signal is recorded at the beginning of the file, there is no time axis error, as shown in Fig. 7(a).

When a time axis error of +1.5H occurs during recording and -1.5H during playback, as shown in Fig. 7(b), and when a time axis error of -1.5H during recording and +1.5H occurs during playback. Figure 7 (Q
), respectively.

That is, as shown in FIG. 7(b), +1°5H1 during recording.
In the worst case where a time axis error of -1.5H occurs during playback,
The length of the video overlap part d is approximately 0.8H, but
If you record the index signal over a length of 0.8H, there is no margin at all, so if you record the index signal over a length of ±1.5H,
If a time axis error exceeding the standard (±1.8H in the case of PAL system) occurs, part of the video signal will be lost. Further, if a margin is to be provided, the length of the index signal recording section must be shortened to 0.8H or less.

On the other hand, during a search, the magnetic tape 1 on which the index signal is recorded is fast-forwarded or rewound while being wound around the rotating drum 11. At this time, the index detection circuit 24
detects the index signal from the reproduction signal supplied from the rotating magnetic head via the preamplifier 25, and outputs the detection signal to the control device 19 when detected. In order to detect the index signal, a signal for gate-extracting only the reproduced signal in the vicinity of the index signal recording area I of part C is synchronized with the output of the position detection circuit 27 and sufficiently includes fluctuations during high-speed tape running. Pulses with such a wide width may be generated and used.

Incidentally, it is desirable that the index signal has a frequency as low as possible in order to reduce the influence of head azimuth and to facilitate detection even during fast forwarding or rewinding. However, in the part C, it is stipulated in the standard that a high level viroft signal fs is recorded at a frequency of 230 or less. This pilot signal f is used to control the height of a plurality of rotating magnetic heads during recording when a piezoelectric element or the like is used in the holding portion of the rotating magnetic head for tracking control. The index signal is then higher than 230k)h and the pilot signal f
, sufficient frequency separation is possible, and furthermore, approximately 740kHz±5
It is desirable to use a signal with a frequency that can be separated in frequency from the low frequency conversion color signal of 00kHz.1For example, if the frequency of the index signal is approximately 1.2M&, it is frequency (FM) modulated by the audio signal, and the second Frequency 1 of the FM audio carrier multiplexed in the section
．． 5MIh are sufficiently separated and can be easily separated and detected. However, when the frequency of signals recorded on a magnetic tape is low, the erasing effect is reduced. If the index signal remains without being completely erased, erroneous operations will occur during retrieval. Therefore, the index signal is selected to have a higher frequency than the FM audio carrier.

On the other hand, as mentioned above, the frequency of the index signal needs to be lower than the frequency of its cancellation signal. Also, from a practical standpoint, it is not a good idea to provide many oscillators inside the device, so for example, they are used as reference signals in a frequency conversion circuit (not shown) that converts the color signal to a low frequency during recording. Let the signal be an erasure signal, for example, 1/
A signal frequency-divided by 3 can be used as an index signal. The frequency of such a reference signal is 37 in the case of the NTSC system.
8f++ (f change is 7 to 15.734), 375 f* ←h is 15.625 &) in case of PAL system, so the index signal is 1 in case of NTSC system.
．． In the case of PAL system, it is 1.953MHz. In this way, the reference signal that the oscillation circuit 26 originally outputs for the frequency conversion circuit can be used as an erasure signal as is, and the index signal generation circuit 23 can easily divide the frequency into 1/3. An index signal can be generated. In addition, the index signal generated in this way is 3 MHz away from the carrier of the luminance signal on the lower side, and the level of its sideband component is reduced, so that the detection level when detecting the index signal will not be erroneously detected. Furthermore, in this case, it is possible to set a plurality of frequencies as index signals by changing the division ratio, etc., and to search for a plurality of types or to give one weight.

In addition to recording or erasing an index signal when recording a video signal or audio signal with a rotating magnetic head, the index signal is also recorded or erasing when a video signal or an audio signal is reproduced using a single rotation magnetic head. You can also do that. In the latter case, the leakage of the index recording signal will affect the weak playback signal output, so when the index signal is supplied, the video signal and FM
It is a good idea to mute the audio signal appropriately.

Furthermore, in the above description, the rotating magnetic head for recording and reproducing is used as the erasing head, but in a device equipped with a rotating magnetic head exclusively for erasing and its erasing signal, they can also be used for erasing the index signal. .

〔effect〕

As described above, the present invention forms a first portion and a second portion on a track inclined with respect to the longitudinal direction of a magnetic tape using a rotating magnetic silver head, and at least a clock signal is recorded in at least the first portion. a section a where data such as PCM audio signals are recorded, a margin section C for after-recording, and a video overlap section d where the video signal of the immediately previous field is continuously recorded.
and the first or second part is divided into two parts.
In a magnetic recording and reproducing device that records or reproduces information,
At least in the second part, an FM audio signal obtained by frequency modulating a predetermined carrier with an audio signal can be multiplexed with the second information to be recorded or reproduced, and is generated in accordance with the rotational position of the rotating magnetic head. signal or first
The position of the margin part is detected from the reproduction signal of the information, and a signal having a higher frequency than the carrier of the FM audio signal is recorded or reproduced in the margin part as an index signal of the first information or the second information. Therefore, the index signal can be recorded and erased accurately and satisfactorily without the need for a special fixed head.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the magnetic recording/reproducing apparatus of the present invention, and FIG.
The figure and FIG. 6 are the timing charts. 3v4 is a plan view of 8m videotape, Figures 4 and 5
The figure is an enlarged plan view of the track, and FIG. 7 is a timing chart of the conventional device. 1... Magnetic tape 2... Track 3... Edge 4... Audio track 5.7... Guard track 6... Cue track 11... Rotating drum 12... Motor 13...・
Frequency generator 14... Pulse generator 15... Servo circuit 16.
...Variable delay circuit 17...Pulse generation circuit 18.20.21...Switch 19...Control device! 22...Recording amplifier 23.
... Index signal generation circuit 24 ... Index signal detection circuit 25 ... Preamplifier 26 ... Oscillation circuit 27 ...
・More than position detection circuit

Claims (1)

[Claims] forming a first portion and a second portion on a track inclined with respect to the longitudinal direction of the magnetic tape by a rotating magnetic head;
At least the first part further includes a part a where a clock signal is recorded, a part b where data such as a PCM audio signal is recorded, a margin part c for after-recording, and a video signal of the immediately previous field. The first video overlap part d is recorded as a video overlap part d.
In the magnetic recording and reproducing device that records or reproduces the first or second information in the part or the second part, an FM audio signal obtained by frequency modulating a predetermined carrier with an audio signal is stored in at least the second part. The position of the margin portion is detected from a signal generated corresponding to the rotational position of the rotary magnetic head or a reproduction signal of the first information. , A magnetic recording/reproducing device characterized in that a signal having a higher frequency than the carrier of the FM audio signal is recorded or reproduced in the margin portion as an index signal of the first information or the second information.