JPH0425604B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a magnetic recording/reproducing device, and in particular, it uses a pilot signal instead of a recording track tracking signal or a tape speed control signal. During continuous shooting in a helical scan type magnetic recording and reproducing device that records video signals by superimposing them on a recording track,
The present invention relates to a magnetic recording/playback device that controls transition from playback mode to recording mode.

[Prior art]

2. Description of the Related Art There is a method for controlling the running of a tape in a conventional household magnetic recording/reproducing device (hereinafter referred to as a VTR) using a control signal. That is,
A control track was provided on the magnetic tape in addition to the video signal track, and the running of the tape was controlled by recording and reproducing control signals using this control track. In the conventional VTR mentioned above, recording is performed by switching from recording pause mode to recording mode during recording.
So-called continuous shooting is possible. However, if you simply pause recording, the next recording will start regardless of the position of the track that has already been recorded, which may cause the tracks to become irregularly arranged or the control signal to become discontinuous. ,
During playback, the tracking servo comes off before and after this continuous shooting, resulting in distorted images. Conventionally, various measures have been taken to prevent this image disturbance. For example, when a recording pause command is issued, the capstan shaft rotates in reverse while the pinch roller continues to press the magnetic tape, rewinds the magnetic tape for a certain period of time, then stops, and issues a command to start the next recording. Next, when a pause cancellation command is issued, the magnetic tape is driven by the rotation of the capstan shaft.
First, the playback state is entered, and during this playback state, the drive adjustment of the capstan is performed so that the phase of the control signal corresponding to the next video track to be recorded matches the phase of the control signal being played back, and then the method is changed to the recording state. It is.

However, there is a method in which a pilot signal for tracking the recording track or for controlling the running of the magnetic tape is recorded on the recording track in a superimposed manner with a video signal, and during playback, the recording track is tracked using the reproduction pilot signal from the magnetic tape. of
Since VTRs do not have the aforementioned control signals, the conventional control method using control signals during continuous shooting cannot be applied, and a new method is required.

[Summary of the invention]

This invention has been made to eliminate the above-mentioned drawbacks, and does not cause overlapping recording tracks or tracking deviations when transitioning from pause mode to recording mode during recording, and does not cause disturbances during playback. It is an object of the present invention to provide a magnetic recording and reproducing apparatus which records a pilot signal by superimposing it on a video signal, and which allows a normal reproduced image to be taken.

In summary, the present invention detects a plurality of different frequency components obtained from a pilot signal, and when at least one of the frequency components is not detected, a transition is made from a recording pause state to a recording state. This is a magnetic recording/playback device that has the function of shifting from playback mode during shooting to recording mode.

The objects and other objects and features of the present invention will become more apparent from the detailed description provided with reference to the following.

[Embodiments of the invention]

FIG. 1 shows the tape drive state of a VTR with a two-head helical scan mechanism using a so-called azimuth head.

In FIG. 1, a magnetic tape 1 is sandwiched between a capstan shaft 2 and a pinch roller (not shown), and is controlled to run in the direction of an arrow 5 as the capstan shaft 2 rotates. Note that the capstan shaft 2 is directly driven by a capstan motor 3. On the other hand, a rotating drum 4 is arranged opposite to the magnetic recording surface of the magnetic tape 1, and a magnetic head A and a magnetic head B having different azimuths are attached to the rotating drum 4 at symmetrical positions with respect to the rotation axis. As the rotary drum 4 rotates, the magnetic tape is traced in the direction of the arrow 6.
Note that the erase head is a fixed full width erase head 7.

FIG. 2 shows a pilot signal recorded on each recording track in the four-frequency pilot system of the VTR, superimposed with a video signal.

In FIG. 2, pilot signals f ₁ , f ₂ , f ₃ and f ₄ of four different frequencies are repeatedly recorded in this order on a video signal track 8, superimposed on the video signal. The frequency of f ₁ ~ f ₄ is for example from 100KHz
There are four types of values up to 200KHz, |f ₁ −f ₂ |=|
f ₃ −f ₄ |=Fa, |f ₁ −f ₄ |=|f ₂ −f ₃ |=Fb, Fa≠
Satisfies the condition of Fb. pilot signal f ₁
and f ₃ are the pilot signals f ₂ by the magnetic head A.
and _f4 are respectively recorded in a superimposed manner with the video signal by the magnetic head B. Here, the pilot signal
Since the frequencies of f ₁ , f ₂ , f ₃ , and f ₄ are lower than the frequency of the video signal, they are less affected by the azimuth effect of the magnetic head, and the recorded pilot signal has an azimuth angle different from that of the magnetic head during recording. Reproduction is also possible with a magnetic head having a In the recording state, after the magnetic recording surface on the magnetic tape 1 is made unrecorded by the fixed full-width erasing head 7, the two magnetic fields on the rotating drum 4 located behind the full-width erasing head 7 are The video signal and the pilot signal are superimposed and recorded by the head.

An embodiment of the present invention relating to continuous shooting in a VTR using such a pilot signal will be described below with reference to the drawings.

FIG. 3A is a configuration block diagram relating to a transition from a recording mode, which can be said to be the start of continuous shooting, to a recording pause according to the present invention.

First, superimposed recording of a pilot signal and a video signal in recording mode will be explained. terminal 32
In synchronization with the head switching signal applied to the four-frequency pilot signals f ₁ , f ₂ , f ₃ ,
Generate f ₄ in the order of f ₁ → f ₂ → f ₃ → f ₄ → f ₁ → f ₂ → f ₃ → f ₄ . In the mixer 22, the pilot signals f ₁ ,
f ₂ , f ₃ , f ₄ and the video signal applied to the terminal 23 are superimposed and output to the terminal 38, and the magnetic tape 1 is sent via the magnetic head as the tape runs as shown in FIG.
recorded above. FIG. 3B shows a timing chart of the main parts of the signals in the configuration block diagram. Referring to FIG. 3B, a case will be described in which a recording pause command is given to perform continuous shooting while this recording mode is continuing.

A head switching signal with a period T ₀ is applied to the terminal 32, and magnetic heads A and B correspond to a high potential H portion and a low potential L portion of the head switching signal, respectively. 4 frequency generation circuit 2
1, a pilot signal is repeatedly generated in the order of frequencies f ₁ , f ₂ , f ₃ , and f ₄ . In this state, a recording temporary stop command is given to the terminal 34. The head switching signal is input to a pulse generator 31 consisting of, for example, a gate circuit. The pulse generator 31 generates a pulse that rises to a high potential H in synchronization with the rise and fall of the head switching signal. This pulse and the clock signal from terminal 33 are input to counter 35. The clock signal from this terminal 33 is output during the period _T0 of the head switching signal.
N is a clock signal forming ₀ pulses.
This counter 35 resets the count value of the clock signal from the terminal 33 every time a pulse rises. The count output value of the counter 35 and the recording pause command are input to a comparator 36. This comparator 36 compares the count output value from the counter 35 at the moment when the recording pause command is input with a predetermined clock number N ₀ corresponding to the period T ₀ of the head switching signal. If the count output value does not reach the predetermined clock number _N0 , recording continues until the count output value from the counter 35 reaches _N0 , and at the same time the count output value reaches _N0 , recording is temporarily stopped. A command is sent to terminal 37. That is, the comparator 36 does not temporarily stop recording at the same time when the recording pause command is given, but switches the head corresponding to the magnetic head that was recording at the time the recording pause command was given. The recording mode remains until the signal ends, and a recording pause is executed when the magnetic head is switched. FIG. 4 is a timing chart of the recording mode, playback mode, and capstan rotation direction when executing and canceling a recording pause.

FIG. 5 shows the state of the recording track in the case of the above-mentioned recording pause.

The following description will be made with reference to FIGS. 4 and 5. The track of _the pilot signal _{f 1 by} the magnetic head _A indicated by diagonal lines in FIG. After forming, pause the recording. After the temporary stop is executed, the rotating drum 4 continues to rotate at the normal rotation speed, but the capstan shaft remains in the state where the pinch roller (not shown) is pressed against the magnetic tape and the rotation direction is the same as in the recording mode. The direction (hereinafter referred to as forward rotation) is reversed to the opposite direction (hereinafter referred to as reverse rotation), and the reverse rotation continues until time _t2 . That is, the magnetic tape is rewound in the reverse direction until time _t2 , and then the capstan shaft is stopped, and it remains on standby until a temporary stop release command is given.

In FIG. 4, when a pause release command is given at time t ₃ , the capstan shaft, which had been stopped before time t ₃ , starts rotating in the normal rotation direction, but instead of immediately restarting recording, Playback by magnetic head A or B placed on the rotating drum at time t ₃
Start from. In other words, the recorded portion of the magnetic tape that has been rewound for the time (t ₂ −t ₁ ) will be reproduced from time t ₃ . When playing,
Magnetic heads A and B not only reproduce the respective video signal tracks, but also reproduce pilot signals from adjacent tracks as crosstalk components. For example, when magnetic head A is operating the track of pilot signal f ₁ (hereinafter referred to as f ₁ track), pilot signals f ₄ and f ₂ of adjacent tracks are also reproduced at the same time.

FIG. 6 is a block diagram of the structure at the time of transition from the above-mentioned reproduction state to the recording state.

In FIG. 6, a pilot signal is separated from the head reproduction signal from a terminal 51 by a low pass filter 52. In FIG. The output of this low-pass filter 52 is input to a frequency converter 53. A pilot signal corresponding to the reproduced track is also input to the frequency converter 53. This frequency converter 5
In step 3, the reproduction level difference between the respective pilot signals from the left and right adjacent tracks is determined. That is, for example, when the magnetic head A is scanning the f ₁ track, the reproduction level difference between this f ₁ pilot signal and the f ₂ and f ₄ pilot signals of the left and right adjacent tracks is detected, and the frequency is |f ₁ - f ₂ |=Fa and |
It is converted into a signal of two frequency components: f ₁ −f ₄ |=Fb. The output of the converter 53 is separated into Fa and Fb components by a bandpass filter 54 having a center frequency of Fa and a bandpass filter 55 having a center frequency of Fb, respectively. separated
Fa and Fb components are each peak value detection circuit 5
6 and 57. The peak value detection circuits 56 and 57 detect the envelopes of the positive side peak values of the frequency components Fa and Fb, respectively, and detect changes in the reproduction envelopes regarding the Fa and Fb components. The outputs of these peak value detection circuits 56 and 57 are input to a subtracter 58, and a difference component regarding the detection level between the Fa component and the Fb component is output. The polarity of this difference component is inverted depending on whether the reproducing head is magnetic head A or B, by an inverting circuit 59 to which the head switching signal is also input. For example, if the reproducing head is magnetic head B, the polarity is inverted; If it remains uninverted,
It is output to a terminal 60 for tracking servo use. Further, as a feature of this embodiment, the outputs of the peak value detection circuits 56 and 57 are input to the positive input terminals of comparators 61 and 62, respectively, and are connected to a certain predetermined bias voltage Vb applied to the negative input terminals. be compared. In other words, the peak value detection circuits 56 and 57 each detect a predetermined level or higher.
If the Fa and Fb components are detected and output, the comparators 61 and 62 each output a high potential H signal. This comparator 61 and 62
The output is input to the AND circuit 63. terminal 32
The output pulse of the pulse generating circuit 63, which generates a pulse that rises to a high potential H in synchronization with the rising and falling of the head switching signal, is input to the counter 65 together with the clock signal at the terminal 66. This counter 65 counts the number of clocks,
This count value is reset each time the output signal of the pulse generating circuit 67 rises to a high potential H, that is, each time the reproduction head is switched. AND
The output of the circuit 63 and the count output value of the counter 65 are input to a timer 64. This timer 64
It is determined whether the output of the AND circuit 63 is a high level H or a low potential L, and if the output of the AND circuit 63 is a low potential L, the count output value of the counter 65 is the period T of the head switching signal. A recording restart command is sent to the terminal 68 to continue the reproduction until the count number _N0 corresponding to ₀ is reached, and the count is reset by the output pulse from the pulse generator 67, and the magnetic head is switched to the recording state.
This is what is output to. Furthermore, if the output of the AND circuit 63 is at a high potential H, reproduction continues even if the magnetic head is switched. Therefore, time t ₃
For playback starting from , time (t _{2 −}
Since the recorded portion of the magnetic tape that was rewound over time _t1 ) will be played back, in playback after time _t3 , the immediate frequency components Fa and Fb are continuously played by magnetic heads A and B. can be obtained. Therefore, since the outputs of the comparators 61 and 62 remain at a high potential H even when the magnetic head being reproduced is switched, the output of the AND circuit 63 also becomes a high potential H, and the reproduction state is maintained. will be maintained. Thereafter, the video signal track for the last field whose recording ended at time _t1 is reproduced. That is, according to FIG. 5, the _f1 track is played back. At this time, the only video signal track adjacent to the f ₁ track is the adjacent f ₄ track, and the other adjacent track is an unrecorded portion, so only the frequency component of |f ₁ − _{f 4} |=Fb It is separated by a bandpass filter 55, and the Fa component is not detected. here,
Even if one or both of the Fa and Fb component signals cannot be obtained, the capstan shaft is controlled by the signal from the terminal 60 and rotates at approximately the predetermined speed, so the magnetic tape remains almost constant. This is not a problem as the vehicle is controlled at a speed of Therefore, at this time, the output of the comparator 61 is a low potential L, the output of the comparator 62 is a high potential H, and the output of the AND circuit 63 is a low potential L. In other words, the output of the AND circuit 63 is switched from the high potential H to the low potential L at the same time as the magnetic head A switches to reproduction and starts reproducing the last _f1 track. As a result, due to the action of the timer 64 mentioned above, the reproduction state, which lasted until the reproduction of one field by magnetic head A is completed, is switched to the recording state at time _t4 when the next magnetic head B is switched. Then, so-called continuous shooting begins. Therefore, after continuous shooting, recording starts from the f ₂ track, and from then on, f ₃ → f ₄ → f ₁
Recording continues in the order of →f ₂ →f ₃ →f ₄ .

As is clear from the above explanation, the pilot signal in the video signal track recorded before and after the continuous shooting continues in the order of f ₁ → f ₂ → f ₃ → f ₄ without breaking the order, and the tracking servo also functions. Therefore, even when playing back this spliced part, the playback image will not be distorted and there will be almost no overlapping.

Note that although the capstan shaft is stopped at time _t2 , the rotating drum 4 continues to rotate after that.
Although not shown, phase control is performed between, for example, a reference frequency signal and a signal that detects the rotational speed of the rotating drum, so that the rotating drum rotates at a regular constant speed. Also, the unwinding time of the capstan shaft (t _2
−t1 ) is the time required for the capstan shaft to start rotating normally from a stop and stabilize at a nearly constant rotation speed during normal regeneration that starts in response to a pause release command given at time _t3 , the so-called servo retraction time. The time has been set accordingly.

In addition, in the above explanation, the last video signal track after recording is temporarily stopped at time _t1 is
I used f ₁ track as an example, but this is f ₂ other than f ₁ ,
Of course, the same applies to either the f ₃ or f ₄ track.

Note that in the above embodiment, execution of the recording pause was delayed from the recording pause command at time _t0 to time _t1 , but the counter 35 and comparator 36 that were used to do this were eliminated. , the temporary stop may be executed at time _t0 . In this case, when the head scans the last video signal track whose recording was paused at time _t0 during playback from time _t3 , it is unlikely that the head will no longer be able to obtain a video signal from the middle of playback. However, the output of the AND circuit 63 changes from the high potential H to the low potential L as reproduction by the head starts.
Therefore, even in this case, the playback by this head is 1
This is similar to the embodiment described above in that the recording mode is set at the point when the magnetic head is switched after continuing for the field. According to this embodiment, although there is a possibility that some noise may appear on the screen during reproduction of the portion before and after the continuous shooting, it has almost the same effect as the above embodiment.

〔Effect of the invention〕

As described above, when playing back the recorded portion of the magnetic tape during so-called splicing, in which the video signal is recorded by superimposing the pilot signal on the video signal, the VCR moves from the recording pause mode to the recording mode. Depending on the presence or absence of a pilot signal from the magnetic head, it is decided whether to continue playing or to switch to recording mode from the next magnetic head, so there is almost no overlap in the continuous shooting part, and there is no tracking deviation. Since it does not occur,
When playing back before and after a spliced shot, you can get a playback screen without noise or disturbance.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the basic structure of a helical scan type magnetic recording/reproducing apparatus that records a pilot signal in a superimposed manner with a video signal. FIG. 2 is a diagram showing a recording track pattern of a magnetic tape in the magnetic recording/reproducing apparatus. FIG. 3A is a configuration block circuit diagram for explaining the recording mode and temporary stop of recording in one embodiment of the present invention. FIG. 3B is a signal waveform diagram for explaining the operation of each block in FIG. 3A.
FIG. 4 is a state diagram for explaining the continuous shooting operation in the same embodiment. FIG. 5 is a diagram of a recording track pattern on the magnetic tape when recording is temporarily stopped in the same embodiment. Figure 6 shows
FIG. 3 is a block diagram for explaining reproduction and transition from reproduction to recording mode in the same embodiment. In the figure, 1 is a magnetic tape, 2 is a capstan shaft, 4 is a rotating drum, 7 is a fixed full-width erasing head,
21 is a 4-frequency generation circuit, 31 is a signal generator, 35
is a counter, 36 is a comparator, 53 is a frequency converter, 54, 55 are band pass filters, 56, 5
7 is a peak value detection circuit, 61 and 62 are comparators, 63 is an AND gate, 64 is a timer, 65 is a counter, 67 is a signal generation circuit, A and B are magnetic heads, f ₁ , f ₂ , f ₃ , f ₄ is the pilot signal,
is the head switching signal. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. In synchronization with the rotation of a plurality of rotating magnetic heads,
A magnetic recording/reproducing device having a playback mode and a recording mode, in which a plurality of pilot signals having different frequencies are superimposed on a video signal and recorded sequentially on each recording track, and the magnetic recording/reproducing device has a playback mode and a recording mode, and the magnetic recording/playback device has a playback mode and a recording mode. a frequency component detection means for detecting two types of frequency components obtained from pilot signals of two tracks; a switching point detection means for detecting a switching point of the magnetic head; a detection output from the frequency component detection means; and transition means for shifting from playback mode to recording mode when at least one of the two types of frequency components is not detected in response to the output of the switching point detection means. 2. The frequency component detection means includes a first comparator that compares the output level of one of the two types of frequency components with a predetermined reference voltage, and an output of the other frequency component of the two types of frequency components. a second comparing the level with the predetermined reference voltage;
Claim 1, comprising: a comparator; and a logic gate for logically processing the outputs of the first and second comparators.
The magnetic recording and reproducing device described in . 3. The logic gate is a gate that outputs a signal for maintaining the reproduction mode when both the first and second comparators indicate that the output level of the given frequency component is higher than the predetermined reference voltage. The magnetic recording and reproducing device according to claim 2, comprising a circuit.