JPH0719406B2 - Recording method of magnetic tape - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a magnetic tape recording method for recording information on a magnetic tape by a rotary magnetic head such as a video tape recorder.

[Conventional technology]

In a magnetic recording / reproducing apparatus represented by a video tape recorder, a tape counter may be used to search for a predetermined recording or reproducing position. However, the search by the 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 rotary drum pulse generator, may be used for searching. Since the timing of one edge of the CTL signal is only used for tracking, the signal with the duty changed can be used as a cue signal (cue signal or index signal) for position search. .

However, such a method of searching using the CTL signal requires a fixed head arranged corresponding to the track on which the CTL signal is recorded and an additional circuit around the fixed head. For example, a so-called 8 mm video recently standardized. Pilot signal for tracking on each track like tape recorder
f ₁ , f ₂ , f ₃ , f ₄ (for example, 6.5f _H , 7.5f _H , 10.5f _H , 9.
5f _H (f _H is the frequency of the horizontal sync signal) is recorded, and basically cannot be used in a device that does not require the CTL signal. If adopted, a fixed head, which is basically unnecessary, must be specially provided only for searching. Further, when recording a plurality of indexes corresponding to one tilt (video) track on one cue track, a special recording method such as time division is required, and the apparatus becomes complicated and expensive. The frequency of the reproduction signal from the cue track is several tens of times that during normal recording and reproduction during fast forward or rewind. It is extremely difficult to extract the index signal for each track by processing the frequency, the period, the waveform, the amplitude, etc. that change significantly. Further, since the cue track is near the edge of the magnetic tape, it has a drawback that it is easily damaged by the tape guide.

The inclined track of the 8 mm video tape recorder is formed with a first portion in which the first information is recorded and a second portion in which the second information is recorded, and the first portion further has a clock signal. A portion a to be recorded, a portion b to which data such as a PCM audio signal is recorded, a margin portion c for after-recording, and a video overlap portion d when the video signal of the immediately preceding field is continuously recorded. The applicant has previously proposed recording an index signal in this portion d (Japanese Patent Application No. 59-277972).
Or Japanese Patent Application No. 60-2464).

[Problems to be solved by the invention]

However, when an index signal is recorded in such a video overlap section d, the recordable length is the longest considering the accumulation of errors in the recording position and the switching position of the reproducing head, which is allowed by the 8 mm video tape recorder standard. However, there is a drawback that it becomes 0.8H (H is a horizontal scanning period), which is shortened to about 0.5H in consideration of a margin for erasing.
Therefore, in the worst case, the video signal recorded in the video overlap portion d is erased, and if the head switching signal fluctuates beyond the allowable range toward the video overlap portion d, the fluctuation exceeding the standard is Since there is no room at all, there is a drawback that a reproduction video signal has a missing period.

[Means for solving problems]

In order to solve the above problems, the present invention provides a first portion in which first information is recorded on a track inclined with respect to a longitudinal direction of a magnetic tape via a rotary magnetic head, and a second information. And a second portion on which a clock signal is recorded, and at least the first portion on which the clock signal is recorded.
And a part b where data such as PCM audio signal is recorded
And a margin part c for after recording,
In the magnetic tape recording method for recording the first or second information by dividing the video signal of the immediately preceding field into the video overlap portion d which is continuously recorded, the first portion is added to the margin portion c. The index signal of the information or the second information is recorded, and the recording start point of the index signal is set to a position corresponding to a substantially horizontal scanning period (1.0H) from the head position of the margin portion c.

[Action]

According to the present invention, the index signal of the first information or the second information is recorded in the margin portion c, and the recording start point of the index signal is substantially horizontal scanning period (1.0H) from the head position of the margin portion c. Positioned considerably.

Therefore, the recording position of the index signal and the recording position of the data or video signal are separated by a predetermined distance, and even if a time axis error occurs, the data or video signal is less likely to be lost.

〔Example〕

Next, a preferred embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a block diagram of the apparatus configuration when the magnetic tape recording method of the present invention is applied to an 8 mm video tape recorder. In the figure, 11 is a rotary drum, and a rotary magnetic head for recording or reproducing, which is not shown, is mounted therein. Reference numeral 12 is a motor for rotating the rotary drum 11. Reference numerals 13 and 14 are a frequency generator and a pulse generator, which output signals of frequency and phase corresponding to the rotation of the rotary drum 11, respectively, and the outputs thereof are supplied to the servo circuit 15. The servo circuit 15 outputs a rotation control signal to the motor 12 and also outputs a head switching signal (HSWP signal) for switching a plurality of rotary magnetic heads. The head switching signal is supplied to the pulse generation circuit 17 via the variable delay circuit 16 provided as necessary. The pulse generation circuit 17 outputs a pulse for controlling on / off of the switches 18 and 26.
Reference numeral 19 denotes a control device including a microcomputer or the like, which controls the on / off of the switches 20 and 21. Reference numeral 22 is a recording amplifier that amplifies a signal supplied to the rotary magnetic head that records or reproduces information. 23 is an index circuit, which switches the index signal to the switch 26,
Output to adder 24 via 20 and preamplifier 25
The index signal is detected from the reproduction signal of. A position detection circuit 27 detects the predetermined position from the reproduction signal supplied from the rotary head.

The operation will be described with reference to FIGS. 2 to 6. The recording amplifier 22 has a video signal and audio (PCM).
Signals to be recorded such as signals and tracking pilot signals are supplied from a video recording circuit, a PCM recording circuit, a tracking recording circuit, etc. (not shown), 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 the reference signal, and controls the rotation of the motor 12 according to the error signal. During reproduction, the reproduction signal from the rotary magnetic head is amplified by the preamplifier 25 and supplied to the video reproduction circuit, PCM reproduction circuit, tracking circuit and the like.

FIG. 3 shows a state on the magnetic tape on which the signal is recorded in this way. That is, a track 2 is formed on the magnetic tape 1 so as to be inclined with respect to its longitudinal direction. For the sake of convenience, the track 2 is divided into a first portion corresponding to a winding angle of the magnetic tape 1 with respect to the rotary drum 11 of about 36 degrees and a second portion corresponding to a winding angle of about 185 degrees, and the former is a PCM audio signal. And tracking pilot signal (TPS signal)
However, in the latter, an FM video signal, an FM audio signal, and a tracking pilot signal can be recorded. The azimuth angles of the corresponding rotary magnetic heads are inclined by about 10 degrees in one of the adjacent tracks 2 in the positive direction and in the other of the adjacent tracks 2 in the negative direction so that crosstalk from the adjacent tracks is reduced. Has become. An audio track 4 having a width R is formed in the vicinity of one edge 3 so that a normal analog audio signal can be recorded by a fixed head as required. A cue track having a width C is formed in the vicinity of the other edge 3 so that a cue signal is recorded by a fixed head as required. Reference numerals 5 and 7 are guard tracks provided between the information recording track and the control signal recording track.

FIG. 4 shows one track 2 on an enlarged scale. That is, the first portion further includes a portion a in which a clock signal is recorded, a portion b in which data such as a PCM audio signal is recorded, and a margin portion c for after recording.
Then, the video signal of the immediately preceding field can be divided into a video overlap portion d in which the video signal 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 positioned at a position separated from the rotary magnetic head by a distance e. The length of each of these parts is set as shown in the table in a system of 525 lines and 60 fields as in the case of the NTSC system and in a system of 625 lines and 50 fields as in the case of the PAL system.

FIG. 5 shows a case where a plurality of portions corresponding to the first portion are formed in the second portion (the portion d may be included in the second portion, but for convenience, Think inclusive). That is, the length of the second portion is an integral multiple of about 5 times the length of the first portion, and five portions corresponding to the first portion are formed in the second portion, and portions a to A PCM audio signal, for example, is recorded in each of the six portions consisting of d.

Next, the recording / reproducing operation of the index signal will be described. In the present invention, the index signal is recorded in the margin portion c of the first portion of the track 2. The portion c has a length of 3.0H in the NTSC system (3.6H in the PAL system).
The servo circuit 15 obtains a predetermined delay time from the outputs of the frequency generator 13 and the pulse generator 14 corresponding to the rotation of the rotating drum 11 by, for example, counting a predetermined clock pulse to obtain a predetermined delay time as necessary, and Output a switching signal (second
Figure (a)). This signal is supplied to the pulse generating circuit 17 via the variable delay circuit 16 (the variable delay circuit 16 is not always necessary in the case of the track configuration as shown in FIGS. 3 and 4). The pulse generation circuit 17 outputs the index signal recording portion I of the portion c when a predetermined time has passed since the head switching signal was generated (for example, 256.7 (262.5-3.8-3.0 ± 1.0) H in the case of the NTSC system).
At the timing of arrival (FIG. 2 (b)), a recording pulse having a predetermined width (for example, 1.5H) is output, and the switch 26 is turned on during that period (solid line in FIG. 2 (c)). In addition, in order to prevent omission of erasure and not to erase PCM data,
For example, an erase pulse having a length of 2.5H is extended by 0.5H before and after the recording pulse so that the start end thereof is separated from the end of the portion b by 0.5H and coincides with the end of the end portion c. It is generated and output, and the switch 18 is turned on during that period (broken line in FIG. 2C). When the index recording operation is performed, the control device 19 turns on the switches 20 and 21, so that the index signal (FIG. 2 (d)) input from the index circuit 23 via the switches 26 and 20 is added to the adder. At 24, for example, it is added with a bias signal of several MHz (FIG. 2 (e)) and supplied to the recording amplifier 22 via the switches 18 and 21 (FIG. 2 (f)). Such an operation is performed for a period to be recorded (for example, several seconds). Therefore, a predetermined number of tracks 2 in which the index signal is recorded in the portion I are formed.

For example, as shown in FIG.
When the PCM audio signal is recorded, the variable delay circuit 16 is provided so that the switches 18 and 26 are turned on in the six parts I of one track 2. Also in this case, since the basic timings match those shown in FIGS. 3 and 4, it is not necessary to separately provide a special circuit other than the variable delay circuit 16.

To erase the index signal, the switch 21 is turned on and the switch 18 is turned on by the erase pulse. Therefore, only the bias signal is supplied to the rotary magnetic head. In this case, the erasing effect can be enhanced by setting the bias signal to a level higher than that during recording.

By the operation described above, the index signal is recorded without the need for a fixed head and an additional circuit around the fixed head,
It becomes possible to erase.

By the way, in the above operation, since the signals for controlling the switches 18 and 26 are generated with the head switching signal as a timing reference, the recording position error on the magnetic tape during recording and reproduction, or the first portion It is inevitable that the timings of the recorded information and the information recorded in the second portion are deviated due to the time axis error. Therefore, when a PCM audio signal is recorded in at least the first portion, the position detection circuit 27 detects a demodulated signal of the PCM audio signal, for example, a synchronization signal indicating the start of data,
A signal obtained by decoding the data block address or the like is used as a timing reference to detect the start point of the portion c or the end point of the portion b (FIG. 2 (g)), and in synchronization with this detection signal. A signal indicating the recording position of the index signal may be generated. Therefore, in this case, the pulse generation circuit 17 outputs the output of the position detection circuit 27 when the PCM audio signal is recorded and the output of the variable delay circuit 16 when the PCM audio signal is not recorded, respectively. As a result, a recording pulse and an erasing pulse for controlling on / off of the switches 18 and 26 are generated respectively.

The relationship among the absolute position on the magnetic tape, the position detection signal, the recording pulse (recording area), and the erasing pulse (erasing area) when the index signal is recorded / reproduced in / from the margin portion c is shown in FIG. become. FIG. 6A shows the case where there is no time axis error at the time of recording.
FIG. 6 (b) shows the case where there is no time axis error during reproduction, and FIG. 6 (c) shows the case where the time axis error during recording is +1.5.
H, the worst case where the time axis error during reproduction is -1.5H is shown. It can be seen that even in the worst case, the video overlap portion d has a length of about 0.8H.

As shown in the sixth (a) and (b), in the present invention,
The recording start point of the index signal is set to a position corresponding to approximately one horizontal scanning period (1.0H) from the head position of the margin portion c, and the reason is as follows. That is,
Considering the recording of the index signal in the margin portion c, there are the following conditions.

I want the index signal to be as long as possible (about 1.5H
If you can get more than this, it is enough for practical use).

The index erase signal needs to be longer than before and after the index signal so that there is no unerased portion of the index signal.

In order not to erase the PCM data by mistake, the index erase signal should start from a position with a margin from the PCM data area b.

In consideration of such a point, as shown in FIG. 6 (a), the index signal is taken 1.5H, the erase signal is taken longer by 0.5H before and after the index signal to prevent erasure leakage, and the PCM data Separated by 0.5H from area b, P
Arrange so that CM data is not accidentally erased. Also,
As shown in Fig. 6 (c), 1.5H each during recording and playback
Even if an error occurs, the video overlap portion d is not lost by recording as in the present invention.

Considering such conditions, it is preferable to start recording the index signal at a position approximately 1.0H away from the beginning of the margin portion c.

On the other hand, as in the conventional case, for example, the video overlap portion d
When the index signal is recorded at the beginning of, when there is no time axis error, it is shown in Fig. 7 (a), and when there is a time axis error of + 1.5H during recording and -1.5H during reproduction, it is shown in Fig. 7 ( b),
Further, when a time axis error of −1.5H during recording and + 1.5H during reproduction occurs, they are respectively shown in FIG. 7 (c). That is, as shown in Fig. 7 (b), + 1.5H during recording and -1.5H during reproduction.
In the worst case in which the time axis error occurs, the length of the video overlap portion d is about 0.8H, but if the index signal is recorded over the length of 0.8H, there is no margin, so if ± 1.5. When a time axis error that exceeds the H (PAL method ± 1.8H) standard occurs, part of the video signal will be lost. In addition, if a margin is taken, the length of the index signal recording section I must be shortened to 0.8H or less.

On the other hand, at the time of search, the magnetic tape 1 on which the index signal is recorded is fast-forwarded or rewound while being wound on the rotary drum 11. At this time, the index circuit 23 detects the index signal from the reproduction signal supplied from the rotary magnetic head through the preamplifier 25, and when detecting the index signal, outputs the detection signal to the control device 19. In order to detect the index signal, as a signal for gate-extracting only the reproduction signal in the vicinity of the index signal recording area I of the portion c, in synchronization with the output of the position detection circuit 27, the fluctuation during high-speed tape running is sufficiently included. A pulse having such a wide width may be generated and used.

The index signal is less affected by head azimuth,
It is desirable to use a signal having a frequency as low as possible so that detection can be easily performed even during fast forward or rewind. However, the standard permits the high level pilot signal f _{5 to} be recorded in the portion c at a frequency of 230 kHz or less. This pilot signal f ₅ is for controlling the heights of a plurality of rotary magnetic heads during recording when tracking control is performed by using a piezoelectric element or the like in the holding portion of the rotary magnetic head. Therefore, the index signal can be a signal having a frequency higher than 230 kHz, which can be sufficiently frequency-separated from the pilot signal f _5, and can also be frequency-separated from the low-pass conversion color signal of approximately 740 kHz ± 500 kHz.
For example, if the frequency of the index signal is 1.2MHz,
It is well separated from the frequency of the FM voice carrier, 1.5MHz,
Separation and detection are possible easily. Of course, a plurality of frequencies can be set as the index signal so that the type of search and weighting can be performed.

In addition to recording or erasing the index signal when the video signal or audio signal is recorded by the rotary magnetic head, the index signal may be recorded when the video signal or audio signal is reproduced by the rotary magnetic head. it can. In this case, since the leakage of the index signal affects the weak reproduction signal output, it is preferable to appropriately mute the video signal and the FMF audio signal when the index signal is supplied.

〔effect〕

As described above, in the present invention, the track formed to be inclined with respect to the longitudinal direction of the magnetic tape is divided into a first portion for recording the first information and a second portion for recording the second information. However, the first portion is further provided with a portion a in which a clock signal is further recorded, a portion b in which data such as a PCM audio signal is recorded, a margin portion c for after-recording, and a video signal in the immediately preceding field. The video overlap portion d recorded as
In the recording method of the magnetic tape for recording the information of No. 1, since the index signal of the first information or the second information is recorded in the margin portion c, the recording and erasing of the index signal can be performed without providing a fixed head. It is possible to perform a search by fast-forwarding or rewinding while the magnetic tape is wound on the rotating drum. Further, according to the present invention, the recording start point of the index signal is set to a position corresponding to about 1 horizontal scanning period (1.0H) from the head position of the margin part, so that even if a time axis error occurs, data or video signal etc. Is less likely to be missing.

[Brief description of drawings]

FIG. 1 is a block diagram of a magnetic recording / reproducing apparatus of the present invention, and FIG.
Figures and 6 show the timing chart, and Figure 3 shows 8mm.
A plan view of the video tape, FIGS. 4 and 5 are enlarged plan views of the tracks, and FIG. 7 is a timing chart of the conventional apparatus. 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 18,26 …… Switch 19 …… Control device, 22 …… Recording amplifier 23 …… Index circuit, 24 …… Adder 25 …… Preamplifier, 27 …… Position detection circuit

Claims (1)

[Claims] 1. A first portion in which first information is recorded on a track inclined with respect to a longitudinal direction of a magnetic tape via a rotary magnetic head, and a second portion in which second information is recorded. Of the first field, a part a in which a clock signal is further recorded, a part b in which data such as a PCM audio signal is recorded, a margin part c for after-recording, and a immediately preceding field. In a magnetic tape recording method for recording a first or second information by dividing it into a video overlap portion d in which a video signal is continuously recorded, in the margin portion c, the first information or the first information is recorded. A magnetic tape for recording an index signal of the second information, and recording start point of the index signal at a position corresponding to about 1 horizontal scanning period (1.0H) from the head position of the margin portion c. Recording method.