JPH056248B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a rotary head type magnetic recording and reproducing system that controls the running of a magnetic tape using a pilot signal recorded on a video signal track superimposed on a video signal. Regarding devices (hereinafter referred to as VTR), in particular, when the signal recording is paused and the signal recording is resumed after the pause is released, the seam of the recording pattern on the magnetic tape is not disturbed, that is, it is highly accurate. This relates to a device that allows continuous shooting.

[Conventional technology]

Conventionally, a method using control signals used to control the feed of a magnetic tape has been widely used as a method for performing continuous shooting in a VTR.

Control signals are recorded and reproduced on the control track and used as signals for magnetic tape running control.
Figure 8 shows a schematic diagram of the tape running system of a VTR.
In the figure, 40 is a supply reel;
1 is the tension arm, 31 is the full width erase head,
42 is a drum equipped with a rotating magnetic head 24;
1 is an A/C head in which an audio head and a control head are assembled into the same head assembly, 43 is a capstan shaft driven by a capstan motor, 44 is a pinch roller, 1 is a magnetic tape, and 46 is a take-up reel. .

The general operation of a VTR with such a configuration will be explained. The magnetic tape 1 is attached to the pinch roller 44
It is crimped onto the capstan shaft 43 by the rotation of the capstan shaft 43, and travels by the rotation of the capstan shaft 43. Normal records/
In the playback mode, the magnetic tape 1 is fed out from the supply reel 40 and the tension arm 4
1, and the drum 4 after passing through the full width erase head 31.
2, and then passed through the A/C head 6 and capstan shaft 43 and wound onto a take-up reel 46.

Figure 7 shows a helical scan system with a control track separate from the video signal track.
FIG. 3 is a diagram showing a recording state of a magnetic tape recorded on a VTR. In this case, video signal tracks 2 are generally recorded diagonally in units of one field on the magnetic tape 1, and pilot signals 3 are recorded at regular intervals in the tape running direction. This control signal 3 is used to control tape running so that the video signal rotary magnetic head 24 can accurately scan the video track 2 during playback.
In the following explanation, signals before being recorded on the magnetic tape 1 will be referred to as recording control signals and magnetic tape 1.
The signal recorded on the magnetic tape 1 is called a control signal, and the signal reproduced from the magnetic tape 1 is called a reproduction control signal.

Usually, the recording control signal 3 is created by dividing the vertical synchronization signal of the video signal to be recorded by 1/2.
Therefore, during playback, the time when the control head 6 detects the control signal 3 and the time when the video signal rotating magnetic head 24 detects the video signal track 2 are determined.
The running state of the magnetic tape 1 is controlled so that the times when the magnetic tape 1 reaches the vicinity of the starting end, that is, the portion where the vertical synchronizing signal is recorded, coincide with each other.

By the way, if the magnetic tape 1 is temporarily stopped at an arbitrary time during recording, and then restarted again at an arbitrary timing and starts recording immediately, the recording phase of the video signal track 2 will be different at the joint, or Since the inclination angle of the video signal track 2 changes, there is a problem in that the reproduced image in that part becomes distorted. For example, when the magnetic tape 1 is temporarily stopped, the video signal rotating magnetic head 2
The traveling locus of No. 4 becomes as shown by the broken line 4 in FIG. In order to prevent such disturbances at the joints of images, the following operation is performed in the servo control system.

Now, if a pause command is issued during recording, the recording operation is immediately stopped and the magnetic tape 1 is moved a certain amount in the opposite direction. After being transferred by a certain amount, the transfer of the magnetic tape 1 is stopped and a recording standby state is entered.

Thereafter, when the temporary stop command is released, the magnetic tape 1 starts to be transferred in the forward direction. At this time, the recording operation does not start immediately, but after synchronizing the playback control signal from the control track of the magnetic tape 1 with the vertical synchronization signal that serves as the reference for the video signal to be newly recorded, that is, after the previously recorded video signal is After matching the phase of the existing video signal track with the phase of the video signal track to be newly recorded, the recording mode is switched to and the recording operation is restarted. In this way, continuous shooting is performed so that the connection between the previously recorded image and the newly recorded image is not disturbed.

However, the trajectory of the rotating magnetic head drawn on the magnetic tape at the time when the recording mode is switched after the temporary stop command is canceled and the recording operation is resumed while the magnetic tape is being transported in the forward direction is If the trajectory of the rotating magnetic head drawn on the magnetic tape at the time when the recording operation is stopped is shifted in the tape running direction, causing a problem. In other words, if it shifts forward, there will be a portion that overwrites the recording pattern recorded on the magnetic tape before the pause command, and if it shifts backward, an unrecorded portion will occur, and this magnetic When the tape is played back, it gives a visually strange feeling on the screen.

To avoid this, generally, after a pause command is issued, the recording operation is stopped, the magnetic tape is transported in the opposite direction, and the number of control signals played back on the control track during this reverse transport period is counted. After the temporary stop command is released, the control signal is regenerated from the control track and the number is counted, and this number is compared with the number counted during the memorized reverse transfer period.
The recording operation is restarted based on the comparison result.

[Problem that the invention seeks to solve]

However, in such conventional VTRs, the contact between the tape and the control head becomes unstable when the tape starts running from a stop or when the tape is reversed in the forward direction. The reproduction of the control signal becomes unstable during the above-mentioned traveling transition. the result,
The problem is that the overwrite period may increase or, conversely, unrecorded areas may occur, giving a visual discomfort during signal reproduction.

In a VTR of the type in which a pilot signal for tracking is recorded by a rotating head, continuous shooting is carried out by a method as disclosed in, for example, Japanese Patent Laid-Open No. 58-203658. That is, when a pause command is issued, recording is temporarily stopped when recording to the track corresponding to a predetermined specific pilot signal is completed, and then the tape is moved backwards by a certain amount in the same manner as above to enter a standby state, and then recording is started. After the pause is released, the pilot signal is reproduced and the tracking servo is applied, and then the last recorded track or the next track is detected, and recording is restarted from the track next to the last track.

In order to detect the final track, crosstalk of pilot signals from adjacent tracks is used, but once the pause is released and the playback mode is entered, for a predetermined period of time,
That is, until the tracking servo is completed, crosstalk cannot be maintained in a normal state, and it is extremely difficult to detect the final track. It also describes a method of detecting the track following the last track based on the presence or absence of a pilot signal on that track. According to such a method, even if recording is restarted immediately upon detecting that track, recording will not continue. There is a problem that some parts are not displayed.

The present invention has been made in view of the above, and an object of the present invention is to provide a rotating head type magnetic recording and reproducing device that can perform continuous shooting with high precision without using a fixed head such as a control head. do.

[Means for solving problems]

The rotating head type magnetic recording/reproducing apparatus according to the present invention controls the running of a magnetic tape using a series of pilot signals of different frequencies, and includes a switching means for interrupting recording of the pilot signal for a predetermined period, and a switching means for interrupting recording and reproduction of the pilot signal. An operation mode switching means for switching the operation mode, a determining means for determining the presence or absence of a pilot signal on the playback track, a magnetic tape running control means for controlling the running of the magnetic tape, and controlling the recording, playback and running systems of the apparatus. The system control means does not record the pilot signal for a certain period of time immediately before interrupting recording during continuous shooting, detects that the output of the frequency band of the series of pilot signals has decreased during phase matching playback, and This system separates the video signal tracks and restarts recording from the next track.

[Effect]

In this invention, during continuous shooting, the pilot signal is not recorded for a certain period of time immediately before recording is interrupted, and the last video is Since the signal tracks are separated and recording is restarted from the next track, even if tracking is lost during the period from the start of phase matching playback until the tracking control is pulled in, the pilot signal will still be recorded. The detected output of the pilot signal does not decrease in the portion where the pilot signal is missing, and the missing portion of the pilot signal can be accurately identified, allowing highly accurate continuous shooting.

〔Example〕

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram of a VTR according to an embodiment of the present invention. In the figure, 24 is a rotating magnetic head, and although only one is shown in the figure for convenience,
There are usually two of these. 22 is the main VTR
A video signal processing circuit 25 processes a video signal inputted to the rotary magnetic head 24 and outputs it as an FM modulated video signal. This is a pilot signal generation circuit that sequentially and repeatedly generates a pilot signal, and this pilot signal is used for tracking control. 23 is a switch provided at the output of the pilot signal generating circuit 25, and 30 is this switch 2.
A pilot signal gate circuit 50 controls the on/off state of the pilot signal generating circuit 25 to gate the output of the pilot signal generating circuit 25; The adder 21 is a recording/reproducing switch.

28 is a pilot signal extraction circuit for extracting a pilot signal from the reproduced signal; 29 is a pilot signal presence/absence determination circuit for detecting the level of the reproduced pilot signal and determining whether or not a pilot signal is recorded on the reproduced track; A magnetic tape running control circuit 26 controls the capstan motor 27 so that the magnetic tape is fed forward or backward, or stopped. 20 is a system control circuit, which is connected to the changeover switch 21,
It sends control signals to the video signal processing circuit 22, pilot signal gate circuit 30, and magnetic tape running control circuit 26 to control the operating system of the VTR.

FIG. 4 shows the pilot signal presence/absence determination circuit 29.
In the figure, 35 is an input terminal, 32 is a detection circuit for envelope detection of the reproduced pilot signal, and 33 is a comparison between the output of this detection circuit 32 and the potential of a DC power supply 34. The comparator 36 is an output terminal.

FIG. 5 is a diagram showing a specific example of the configuration of the pilot signal gate circuit 30, and in the figure,
51 is an input terminal, 52 is an inverter, 53 is a 2-input NAND gate, 54 is an output terminal, and R and C are a resistor and a capacitor for determining a time constant, respectively.

Next, the operation will be explained.

Before explaining the overall operation of this device, the operation of the pilot signal gate circuit 30 of the device will be explained using the timing chart shown in FIG. First, when a pause command signal G whose rising edge indicates a temporary stop is input from the input terminal 51 shown in FIG. A discharge output I is obtained with a time constant determined by the capacitance value C, and B is output from the two-input NAND gate. In this way, the output B is a signal that becomes low level for a certain period of time after the temporary stop command signal G is input.

FIG. 2 is a diagram showing a timing chart of the apparatus of this embodiment, and the overall operation of the apparatus will be explained with reference to this timing chart.

During normal recording, the switch 21 and the video signal processing circuit 22 are controlled to the recording mode by the control signal C from the system control circuit 20.
Switch 23 is turned on by control signal B, and FM
A signal in which a pilot signal is superimposed on a modulated video signal is recorded on a magnetic tape by a rotating magnetic head 24. At this time, the system control circuit 20
The capstan motor 27 is controlled by the magnetic tape running control circuit 26 which receives the control signals E and F, and the magnetic tape is fed at a constant speed in the forward direction.

When a temporary stop command is given in such a state, the switch 23 is turned off for a certain period of time by the aforementioned control signal B output from the pilot signal gate circuit 30, and then the system control circuit 20 is turned off in synchronization with the head switching signal A. The switch 21 is switched by the control signal C, and the recording of the video signal and pilot signal on the magnetic tape by the rotating magnetic head 24 is interrupted. FIG. 3 shows the state of the recording track at this time. In the figure, 1 is a magnetic tape,
2 is a video signal track. As is clear from this figure, during normal recording, a video signal and a pilot signal are recorded on video signal track 2, but if a pause command is given while recording track _T1 , the above-mentioned situation will occur. By means of the system control circuit 20 and the pilot signal gate circuit 30, no pilot signal is recorded in a portion of the track _T1 , only the video signal is recorded, and the track T1 is
After recording T ₁ , recording is interrupted.

After recording is interrupted, the capstan motor 27 is temporarily stopped by the control signal E from the system control circuit 20 via the magnetic tape running control circuit 26. Thereafter, the capstan motor 27 is reversed, and the magnetic tape 1 is reversely transported for a predetermined period of time, and then stopped.

Next, when the temporary stop command is released, magnetic tape running is activated by control signals E and F from the system control circuit 20, and the tape is transported in the forward direction. At this time, the switch 21 and the video signal processing circuit 22 are set to the playback mode by the control signal C from the system control circuit 20, and the pilot signal extraction circuit 28 to which the playback signal is input extracts the playback pilot signal. be done. The magnetic tape running control circuit 26 then uses the reproduction pilot signal to ensure that the locus of the rotating magnetic head 24 drawn on the magnetic tape matches the recording pattern on the magnetic tape recorded before the pause command was input. and pilot signal generation circuit 2
The tape running is controlled by controlling the capstan motor 27 so that the frequency of the pilot signal generated from the tape 5 coincides with the frequency of the pilot signal recorded on the track being scanned by the rotating magnetic head 24. Here, the amount of time for reverse transporting the magnetic tape when a pause command is input can be sufficiently controlled within this time if the magnetic tape running is controlled based on the playback pilot signal after restarting the magnetic tape running. The system is set so that it can settle.

The reproduced pilot signal extracted by the pilot signal extraction circuit 28 is input to the magnetic tape running control circuit 26 for tracking control as described above, and is also input to the pilot signal presence/absence determining circuit 29. That is, the reproduced pilot signal enters the input terminal 35 (see FIG. 4) of the discrimination circuit 29, is subjected to envelope detection in the detection circuit 32, is compared with a constant potential given by the DC power supply 34 in the comparator 33, and is output to the detection circuit 32. When the potential of the DC power supply 32 is higher than the potential of the DC power supply 34, a high level is outputted from the output terminal 36, and when it is smaller than the potential, a low level is outputted from the output terminal 36. Therefore, when the rotating magnetic head scans the recorded magnetic tape as shown in FIG. 3, a reproduced pilot signal of a certain level can be obtained from the track on which the video signal and the pilot signal are recorded. , a high level is output from the pilot signal presence/absence determination circuit 29, but when the rotating magnetic head is scanning a portion where only the video signal of track _T1 is recorded and no pilot signal is recorded, the reproduced pilot signal is not output. Since there is only crosstalk from the adjacent track _T0 , its level drops significantly, and the output of the pilot signal presence/absence determining circuit 29 becomes low level. The output D of this pilot signal presence/absence determination circuit 29 is output to the system control circuit 20.
is input.

In the system control circuit 20, when the signal D indicating that there is no reproduction pilot signal is input, the control signal C is switched to the recording mode from the next track in synchronization with the head switching signal A, and the control signal C is used to control the video signal. Then, recording of the pilot signal onto the magnetic tape is resumed.

In this way, in the device of this embodiment, after a pause is released, recording is resumed from the video signal track next to the last video signal track recorded before the pause. Also, no unrecorded portions occur, and the order of pilot signals is maintained correctly. However, although the pilot signal is not recorded in a portion of the last video signal track recorded before pausing, the fact that the pilot signal disappears in a portion of one track during playback has virtually no effect on the tape running control system. no problem. In addition, the pilot signal that is removed during splicing is an arbitrary signal that is determined by the timing at which a pause command is input during recording mode, and the output of the frequency band of the series of pilot signals decreases during phase matching playback. Since the absence of the pilot signal is detected by the following, the absence of the pilot signal can be accurately detected even if the tracking control is not engaged. Therefore, even if this spliced portion is played back, the reproduced image will not be distorted, and there will be no visual discomfort due to overwritten portions or unrecorded portions.

Further, unlike the conventional system, a dedicated fixed head for reproducing control signals is not required, and the configuration of the apparatus can be simplified.

In the present invention, the period during which the pilot signal is not recorded is set to be shorter than one track scanning period, but it may be considered to be one track period or two or more tracks.

〔Effect of the invention〕

As described above, according to the present invention, a rotary head is constructed in which a series of pilot signals having different frequencies are superimposed on a video signal and repeatedly recorded in sequence for each track, and tracking control during playback is performed using the pilot signals. In a type magnetic recording/reproducing device, during continuous shooting, the pilot signal is not recorded for a certain period of time immediately before recording is interrupted, and when the output of the frequency band of the series of pilot signals has decreased during phase alignment and playback, it is detected that the output of the frequency band has decreased. Since the video signal track is identified and recording is restarted from the next track, it is possible to accurately identify the missing portion of the pilot signal, which prevents overwritten portions or unrecorded portions from occurring in the spliced portion. High-precision continuous shooting can be performed without the need for continuous shooting, and since each signal can be reproduced only by the rotating head, there is no need for a fixed head for continuous shooting, which has the effect of simplifying the configuration of the device.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a VTR according to an embodiment of the present invention, Fig. 2 is a timing chart for explaining the operation of the device, and Fig. 3 is a magnetic tape immediately before a pause during splicing in the device. FIG. 4 is a circuit block diagram showing an example of the pilot signal presence/absence determination circuit in the device shown in FIG. 1, and FIG. 5 is a circuit showing an example of the pilot signal gate circuit in the device shown in FIG. 1. figure,
FIG. 6 is a timing chart for explaining the operation of the circuit, and FIG. 7 is a diagram showing the relationship between the recording pattern on the magnetic tape and the locus drawn on the magnetic tape by the rotating magnetic head during splicing in a conventional example. FIG. 8 is a schematic diagram of a general VTR magnetic tape running system. 20... System control circuit, 21... Changeover switch (operation mode switching means), 23... Switch, 24...
Rotating magnetic head, 25... Pilot signal generation circuit, 26... Magnetic tape running control circuit, 28... Pilot signal extraction circuit, 29... Pilot signal presence/absence determination circuit, 30... Pilot signal gate circuit, 3
2...Detection circuit, 33...Comparator, 34...DC power supply. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] 1. Using a plurality of rotating magnetic heads, a series of pilot signals, each having a different frequency, are superimposed on a video signal and are sequentially and repeatedly recorded on each video track on a magnetic tape, and upon playback, the playback signal is A rotary head type magnetic recording/reproducing device that controls the traveling of the magnetic tape based on the pilot signal extracted from the pilot signal, wherein when a pause command signal is input, the pilot signal is operated for a predetermined period shorter than one track scanning period immediately after a pause command signal is input. a switching means for interrupting signal recording; an operation mode switching means for switching between recording and reproducing operation modes; a determining means for determining the presence or absence of a pilot signal on a playback track; a magnetic tape running control means for controlling running of the magnetic tape; and when a pause command is input during a recording mode;
After recording only the video signal without recording the pilot signal for the predetermined period, recording is interrupted in synchronization with the head switching signal, and then the magnetic tape is moved in the opposite direction by a certain amount, and then the magnetic tape is stopped running; When a pause release command is input, the magnetic tape is moved in the forward direction, and the magnetic tape is moved so that the rotating magnetic head normally scans the recording tracks on the magnetic tape recorded before the pause in playback mode. Controlling the running, determining the presence or absence of a pilot signal on the reproduction track, identifying the last video signal track recorded before the pause, and recording the video signal and pilot signal from the video signal track next to the said track. What is claimed is: 1. A rotating head type magnetic recording/reproducing device, comprising: a system control means for restarting the system. 2. The discrimination means comprises a detection circuit that detects the extracted reproduced pilot signal, and a comparison circuit that compares the output obtained from the detection circuit with a preset level. A rotating head type magnetic recording and reproducing device according to item 1.