JPH0832920A - Video tape recorder - Google Patents

Abstract

PURPOSE:To provide a video tape recorder which can secure the quick follow-up of its tape speed control to the shift of modes by reducing the tape speed down to a low speed reproduction mode of the same track pitch as a standard reproduction mode after the tape speed is once shifted to the standard reproduction mode from a high speed search mode. CONSTITUTION:When a high speed search mode H is selected by a push button 89, a microcomputer 74 orders a speed/phase control circuit 86 to control a capstan motor 80 to drive a tape T at a speed 7 times as high as a standard reproduction mode S. Then an operator operates the button 89 to instruct the shift of the tape speed to a 1/3 standard reproduction mode L equal to a frame thinning recording mode while looking at a reproduction screen. Thus the microcomputer 74 once commands the circuit 86 to set the mode S. Therefore the circuit 86 drives the tape T in the mode S. When the drive of the tape T is stabilized, the microcomputer 74 commands the circuit 86 to reduce in steps the tape speed down to the mode L of the same track pitch as the mode S. In such a constitution, the tape speed control can quickly follow the shift of modes and the operator can look at the reproduction screen even in a mode shift state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called time-lapse video tape recorder (VTR) capable of recording a video signal for a long time by skipping a frame.

[0002]

2. Description of the Related Art An example of a so-called time-lapse VTR for recording a video signal for a long time by using a normal tape by thinning out the video signal is disclosed in Japanese Patent Laid-Open Publication No. 62-166671 (H04N5 / 782). There is. In this conventional example, a video signal is extracted in a first field, a fourth field, and a seventh field and recorded on a magnetic tape at a period of three fields, that is, so-called frame-free recording. As a result, a recording pattern is an odd field and an even field. Therefore, adjacent tracks can be recorded by heads having different azimuth angles.

Further, the applicant of the present invention has filed Japanese Patent Application No. 5-2212.
No. 44 further details the above time-lapse VTR.

FIG. 2 is a circuit block diagram for explaining the supply of the video signal to the head during recording. The video signal input to the input terminal 1 is input to the sync separation circuit 4 and is amplified by the recording amplifier 2. After being processed, it is supplied to the gate circuit 3 and the processing circuit 52.

The sync separation circuit 4 extracts a vertical sync signal from the input video signal, and the obtained vertical sync signal is input to the cylinder drive circuit 5 and the gate control circuit 6.
The cylinder drive circuit 5 adds a well-known phase servo using the vertical synchronizing signal to the cylinder 7 in addition to a well-known speed servo for maintaining the rotation speed of the rotary cylinder 7 at a constant speed. Drive the cylinder motor.

On the other hand, the gate control circuit 6 creates a gate control signal using the vertical synchronizing signal. As shown in FIG. 3, this gate control signal is at the H level for one field period every three fields, and the gate circuit 3 receives this gate control signal and inputs it only during the period when the gate control signal is at the H level. The video signal is allowed to pass, and as a result, the video signal for one field is output from the gate circuit 3 in a cycle of three fields. In the example of FIG. 3, when the video signal V1 of the first field is output, the video signal V1 of the fourth field is next, and the video signal V of the seventh field is next.
4, V7 are output every 3 fields.

The video signal thus output is the cylinder 7
Built-in video head A + 4 facing each other
0 and A-41 are alternately supplied. Video head A +,
A- is a pair of heads having mutually opposite azimuths, and as shown in FIG. 3, the output from the gate circuit 3 is alternately distributed to the video heads A + and A- for each field. That is, the video signal V1 of the first field is the video head A +
4 to form a track pattern such as T1 in FIG. 4 on the tape, the video signal V2 of the next second field is cut off by the gate circuit 3 and the current of the video head A- is turned off. . As a result, the track pattern of T2 should originally be formed, but T2 is not formed due to the current off state. Similarly, the video signal V3 of the third field is cut off by the gate circuit 3 and the current of the video head A + is turned off. As a result, the track pattern T3 is not formed either. In this way, since T2 and T3 are not substantially formed on T1, the track pattern T1 having the track pitch Tp remains as it is, and the video signal V1 is recorded there.

Further, the next fourth field video signal V4
Is supplied to the video head A- and the track pattern T
4 is formed, the video signals V5 and V6 of the fifth and sixth fields are cut off and the current of the video head is turned off as described above, the track patterns T5 and T6 are not formed, and the track pattern of the track pitch Tp is formed. T4 remains as it is, and the video signal of the fourth field is recorded here.

Similarly, the video signal V7 of the seventh field and the video signal V10 of the track pattern T10 formed by the video head A- are sequentially recorded on the track pattern T7 formed by the video track A +. It As a result, the video signals of the 1st, 7th, 13th, ...
The video signals of the 0th, 16th, and so on fields are intermittently recorded by the video head A- with frame skipping.

FIG. 4 shows a track pattern formed on the magnetic tape. The chain line is a track pattern formed when video signals are sequentially recorded one field at a time without frame-free recording, and the solid line is the above-mentioned. Similarly, the track pattern is formed when the frame-out recording is performed. The track T1 when the frame-out recording is formed is formed in the portion where the first to third tracks are formed during the continuous recording.
The track T4 at the time of frame skip recording is formed at the portion where the sixth track is formed, and the track T7 at the time of frame skip recording is formed at the portion where the seventh to ninth tracks are formed at the time of continuous recording. Here, the azimuth angles of adjacent tracks are different from each other.

Further, 3 supplied from the gate control circuit 6
A gate control signal (see FIG. 3) that becomes H level at a rate of one field in a field is extracted by the signal processing circuit 52 every other pulse as shown in FIG.
That is, it is given to the gate circuit 51 as a signal which becomes H level at a rate of 1 field in 6 fields. As a specific example of the signal processing circuit 52, a frequency dividing circuit that divides the gate control signal from the gate control circuit 6 by 1/2 and an AND circuit that logically ANDs the frequency division output and the gate control signal are used. The AND circuit output is provided to the gate circuit 51.

The vertical synchronizing signal output from the sync separating circuit 4 is applied to the gate circuit 51, and the gate circuit 51 responds to the gate control signal processed as described above during the H level period. Only, that is, the vertical synchronizing signal is passed in a cycle of 6 fields. Thus, the gate circuit 51
The vertical synchronizing signal which has passed through is recorded as a control signal by the control head 53 on the control track of the magnetic tape at a cycle of 6 fields.

Next, drive control of the capstan for tape running during frame-free recording will be described with reference to the circuit block diagram of FIG. FIG. 5 shows a speed servo system of a capstan motor 20 that drives a capstan that runs the tape. The FG detector 10 detects the rotation state of the capstan motor 20, and the FG whose frequency is proportional to this rotation speed. The period of the signal is detected by the speed detector.
Specifically, this speed detector counts a clock of a predetermined frequency and is reset by the rising edge of the divided FG signal, and a latch circuit that latches the count value of the counter 12 in synchronization with the rising edge. 13 and outputs the cycle of the FG signal as latch data.

The comparison circuit 18 compares both input data, and compares the output from the memory 14 in which the VTR previously stores the speed data for frame removal recording and the latch data of the latch circuit 13 as the current speed data, The difference between the two is output as a speed error signal. This speed error signal is added by the adder 100 together with a phase error signal, which will be described later, and the addition result is supplied to the motor driver 19 to control the speed of the capstan motor 20. The constant-speed feeding of the tape is realized at the speed Va.

Here, the phase error signal is obtained by comparing the phase of the PG pulse obtained every one rotation of the capstan motor 20 with the phase of the vertical synchronizing signal in the video signal to be recorded, and calculating the phase difference between them. It is detected by calculating the difference between the phase difference and a reference value capable of maintaining the optimum phase state.

When the tape on which the frame-out recording pattern is formed is reproduced at the same tape feeding speed as that at the time of recording in this way, the head locus becomes as shown by the alternate long and short dash line as shown in FIG. The area surrounded by this alternate long and short dash line and the solid lines (time for half a cylinder revolution) drawn at equal intervals parallel to the vertical axis on the time axis shows the relationship between the recording pattern on the tape and the trace path of the head. Correspondingly, the area of the + part and the area of the-part in this area are respectively + azimuth head,-
Shows the size of the playback output from the azimuth head. Also, the one with the larger reproduction output is hatched. Incidentally, the track width Ht of the head is less than twice the track pitch Tp recorded on the tape and is set to 21.5 μm in this embodiment.

Here, when the head having the larger reproduction output is selectively reproduced, the azimuth angle of the track to be traced is + → − →→→→→→→→→→→→→→ +
→ You can see that ... is repeated. That is, if it is possible to recognize the position of the repeating pattern at the start of reproduction, then it is possible to perform the head switching operation regularly in accordance with the pattern.

FIG. 6 is a diagram showing the relationship between the pattern recorded on the tape and the head locus during reproduction. Figure 6 (a)
6 at time t1, FIG. 6 (b) at time t2, and FIG.
6 (c) at time t3, FIG. 6 (d) at time t4, and FIG.
(E) corresponds to time t5, and FIG. 6 (f) corresponds to time t6. After that, the states of FIGS. 6A to 6F are repeated.

On the tape, in addition to a video signal, an audio signal and a control signal serving as a servo reference signal for accurately tracing a recording track during reproduction are recorded. This control signal is a rectangular wave whose rising portion is recorded on every other track of the video signal on the tape recording pattern. That is, in this embodiment, the rectangular wave has a period of 1/10 SEC. This recorded rectangular wave becomes a differential waveform as shown in FIG. 8 at the time of reproduction, and only the positive pulse which is the reproduction signal at the rising of the recorded rectangular wave is used as the servo reference signal.

Therefore, the positional relationship between the recording pattern and the head at the time of detecting the positive pulse is uniquely determined. For example, if the relationship between the recording pattern and the head at the time of detecting the positive pulse is set as shown in FIG. 6A. + Operating head for positive pulse detection
As an azimuth head, hereafter-Azimuth head 3 times, +
The operation is repeated such that the azimuth head is repeated twice and the positive pulse is detected at the time of the third + azimuth head repetition (corresponding to FIG. 6A). That is, by detecting the rising edge of the control signal, it is possible to uniquely determine whether the operating head at the start of reproduction should be + azimuth or −azimuth. It is possible to selectively switch the reproducing head to a head having a large output.

Here, in order to realize regular head switching, the recording position of the control signal in the block diagram of FIG. 2 is set to the timing at which the video signal is recorded by the head A +.

Next, a method of switching heads during reproduction will be specifically described with reference to the block diagram of FIG. In the figure, a cylinder 7 is a double azimuth 4-head cylinder, and the heads A + and A- of these are used at the time of recording, but at the time of reproduction, in addition to the heads A + and A-, the azimuth angle is head A +. In addition to the head B + which is the same as the head B and is arranged near the head A-, and the head A-, a head B- which has the same azimuth angle as the head A- and is arranged near the head A + is used. , Playback amplifiers 56, 57, 5
After being amplified at 8, 59, the reproduction output of the head A- is output to the fixed contact 60a of the first switch 60, the reproduction output of the head B + is output to the fixed contact 60c of the first switch 60, and the reproduction output of the head A + is output to the first output. Fixed contact 60b of 1 switch 60
Then, the reproduction output of the head B- is supplied to the fixed contact 60d of the first switch 60.

The movable segment 60e selects the fixed contacts 60a and 60b by a switching pulse described later, the movable segment 60f selects the fixed contacts 60c and 60d, and the movable segment 60e is selected when the switching pulse is at L (low) level. The fixed contact 60a is selected, and at the same time, the movable piece 60f selects the fixed contact 60c. When the switching pulse is at the H (high) level, the movable piece 60e selects the fixed contact 60b, and at the same time, the movable piece 60f sets the fixed contact 60b.
Select d. The switching pulse is created by a switching pulse creation circuit 77 described later.

The selection output of the first switch 60 is the second output.
The movable segment 60e is supplied to the fixed contact 70a of the second switch 70, and the movable segment 60f is supplied to the fixed contact 70b of the second switch 70. The switching control of the movable section 70c of the second switch 70 is performed by a control signal from a microcomputer 74 described later.

The selected output of the second switch 70 is supplied to the video signal processing circuit 71, subjected to known reproduction signal processing, and then output as a reproduction video signal.

Reference numeral 72 is a control head for reproducing the control signal recorded on the tape 73. The output of the head 72 is input to the control signal detection circuit 73 and input to the microcomputer 74 in the subsequent stage as a signal shown in FIG. It

Reference numeral 76 is a rotation phase detection circuit which outputs one PG pulse each time the rotor of the cylinder 7 makes one rotation based on the output of the PG detection coil 75 which magnetically detects the rotation state of the cylinder 7. . The positional relationship between the PG detection coil and each head is determined at the position where the PG pulse is emitted when the video head A + traces the recording track in the state of FIG. 6A.

The obtained PG pulse is supplied to the switching pulse generating circuit 77 in the subsequent stage, where it is synchronized with the rotation phase of the cylinder 7 based on the PG pulse, that is, with the rising edge of the PG pulse, A switching pulse (SWP) having a duty of 50% with one rotation time as one cycle is created. Further, the switching pulse selects the fixed contacts 60a and 60b, and the fixed contact 6
0c and 60d are selected, and the head A-output and the head B + output are selected as the output of the first switch 60, or the head A + output and the head B- output are selected.

The switching pulse is also supplied to the microcomputer 74 and is a control signal for selecting the heads of the first group (head A +, head A-) and the second group (head B +, head B-). Is output.

A switching pulse of H level is output to the microcomputer 74 in synchronization with the rising edge where the reproduction control signal becomes H level, and then the switching pulse changes its level from H to L or from L to H. Then, in synchronization with each edge, H → H → L → H → H → L
The algorithm is determined in advance so that the H level and then the L level are repeated twice such as → H → ...

Therefore, at the time of reproducing by applying the servo using the control signal, the relationship between the head and the recording pattern when the positive pulse of the control signal is detected can be uniquely determined. That is, if the reproduction state of the head A + is set as shown in FIG. 6 (a), the head A + will always perform the tracing of FIG. 6 (a) when the positive pulse of the control signal is detected.

Next, the operation of the circuit block configured as described above will be described with reference to the timing chart of FIG.

When the cylinder and the capstan servo are applied in the reproduction mode while maintaining the tape running speed in the above-mentioned frame-free recording mode, first, the head A + is moved to the position shown in FIG.
The recording track is traced in the state of (a). This time,
The first switch 60 by the H level switching pulse
Switches to the H side, that is, the fixed contacts 60b and 60d side.

On the other hand, an H level reproduction control signal is supplied from the control signal detection circuit 73, and an H level control signal is issued from the microcomputer 74 which receives the reproduction control signal.
The second switch 70 switches to the H side, that is, the fixed contact 70a side. As a result, the reproduction signal from the head A + is input to the video signal processing circuit 71, and the corresponding video signal is output.

Next, the cylinder 7 makes a half rotation, and the head A-
And when the head B + comes to the position where the tape is traced,
Since the switching pulse is at the L level, the first switch 60 switches to the L side. At the same time, the microcomputer 74 outputs an H level control signal, the second switch 70 is continuously switched to the fixed contact 70a side, and the signal from the head A- is input to the video signal processing circuit 71.
The state of (b) is realized.

Next, when the head A + and the head B- reach the position where the tape is traced, the switching pulse becomes the H level, so that the first switch 60 is switched to the H side. At the same time, the microcomputer 74 outputs an L level control signal, the second switch 70 is switched to the fixed contact 70a side, and the signal from the head B- is input to the video signal processing circuit 71, as shown in FIG. ) State is realized.

Next, when the head A- and the head B + come to the position where the tape is traced, the switching pulse becomes L level, so that the first switch 60 is switched to the L side. At the same time, the microcomputer 74 outputs an H level control signal, the second switch 70 is switched to the fixed contact 70a side, and the signal from the head A- is input to the video signal processing circuit 71. ) Will be realized.

Next, when the head A + and the head B- come to the position where the tape is traced, the switching pulse becomes the H level, so that the first switch 60 is switched to the H side. At the same time, the microcomputer 74 outputs an H level control signal, the second switch 70 switches to the fixed contact 70a side, and the signal from the head A + is input to the video signal processing circuit 71, as shown in FIG. The state of will be realized.

Next, when the head A- and the head B + come to the position where the tape is traced, the switching pulse becomes the L level, so that the first switch 60 is switched to the L side. At the same time, the microcomputer 74 outputs an L level control signal, the second switch 70 switches to the fixed contact 70b side, and the signal from the head B + is input to the video signal processing circuit 71, as shown in FIG. The state of will be realized.

Next, when the head A + and the head B- come to the position where the tape is traced, the switching pulse becomes the H level, so that the first switch 60 is switched to the H side. At the same time, the microcomputer 74 outputs an H level control signal, the second switch 70 is switched to the fixed contact 70a side, and the signal from the head A + is input to the video signal processing circuit 71, as shown in FIG. The state of will be realized. After that, the same operation is repeated.

That is, first, the second switch 70 is switched to the fixed contact 70a side at the time of track reproduction in which a positive pulse of the reproduction control signal is detected, and thereafter, the first switch 60 is set by an algorithm preset in the microcomputer 74.
Of the control signal to the second switch 70 in synchronization with the switching timing of the L side and the H side of H → H → L → H → H → L.
→ H → H → L is repeatedly switched in this order. As a result, the reproducing head can be selectively switched to a head having a large reproducing output without observing the envelope.

As described above, the time lapse V in which only one field is taken out of the three fields and the frame skip recording can be performed.
In the TR, normally, the tape running speed is tripled and the video signal is continuously recorded without the frame skipping and the track pitch T is set.
Compared to the case of executing so-called standard recording in which p is the same as the time-lapse recording, the tape running speed is as low as ⅓, so that the same tape can achieve a recording time three times that of normal recording. It is mainly used as a surveillance VTR in combination with a surveillance camera.

The object to be imaged by the surveillance camera recorded in the surveillance VTR usually has no new information, and an intruder has entered the screen, or the main subject is in a special state different from usual. Only if the watcher needs attention. Therefore, when the video signal recorded by the monitor VTR is reproduced and the monitor confirms that the abnormal state is found as described above, the VTR is set to the fast-forward reproduction mode and the normal screen is skipped. When the occurrence of a special state of an intruder or a main subject is found on the fast-forward playback screen, it is common to immediately switch to the low-speed playback mode and carefully check the intruder or the main subject. is there.

[0044]

As described above, when the time-lapse VTR is rapidly moved from the fast-forward reproduction mode to the reproduction mode in which the head of the same azimuth continuously traces one track three times to retrieve information, The rotation speed of the capstan motor, which is the drive source for running the tape, must be drastically reduced to bring the servo system of the motor into a state suitable for the playback mode. Cannot be followed, and the playback screen is disturbed when this is not followed.

[0045]

[Means for Solving the Problems] The above time-lapse VT
In R, the track pitch formed by frame-free recording at the tape speed Va for frame-free recording is three times the tape running speed, and when the video signal is continuously recorded without frame-free recording. Since it can be maintained at the same track pitch as during normal recording, normal playback can be performed by tracing each track once even at a speed three times the tape speed during frame-free recording during playback. , For example, the first field V1, the fourth field V4,
The seventh field V7 changes every one field period,
Paying attention to the fact that the screen becomes close to triple speed reproduction, when the mode is changed from the high speed search mode to the reproduction mode at the speed Va, the high speed search mode is once changed to the standard reproduction mode at three times the speed Va. The reproducing operation in the mode is continued for a predetermined time to wait for stabilization of the servo system, and thereafter, the reproducing mode is changed to the reproducing mode at the speed Va.

More specifically, a video signal for one field in 2n + 1 (n is a positive integer) field is periodically extracted and sequentially recorded at different first and second azimuth angles for each track. A first head group including a first head having a first azimuth angle and a second head having a second azimuth angle, the first head group having a first azimuth angle, and the second head having a second azimuth angle. A third head having a second azimuth angle arranged opposite to the head and a fourth head group having a first azimuth angle arranged near the third head are wound around a cylinder having a second head group and reproduced. However, in the 1 / n standard reproduction mode of the same tape speed as that at the time of frame-free recording, in the video tape recorder in which the heads of the same azimuth in both head groups alternately scan the same track n times continuously, Tape running control means for controlling the running speed of the tape to 1 / n times the standard playing mode in the standard playback mode and to the speed m (m is an integer) times in the standard playback mode in the high speed search mode; A mode setting means for setting the operation mode of the control means to one of the standard reproduction mode, the 1 / n standard reproduction mode and the high speed search mode, and a mode setting means when the mode is changed from the high speed search mode to the 1 / n standard reproduction mode. Switches the tape running control means from the high speed search mode to the standard playback mode.
It is characterized in that a mode transition command is issued, and a second mode transition command for switching from the standard reproduction mode to the 1 / n standard reproduction mode is issued after a predetermined time t from the first mode transition command.

Further, the first switch means for alternately selecting either the output of the first head group or the output of the second head group for each 1/2 rotation of the cylinder, and the output of the first head group. A first state in which the first head output is selected as the output of the second head group and the third head output is selected as the output of the second head group, and the second head output is output as the output of the first head group as the output of the second head group. A second switch means for selectively switching to a second state for selecting the fourth head output is provided, and the second switch means selects a track having a predetermined positional relationship with a reproduction control signal obtained when reproducing the magnetic tape. As a starting point, the preset first period is switched to the first state, and the preset second period different from the first period is switched to the second state.

[0048]

Since the present invention is configured as described above, signal reproduction is possible at the time of mode transition from the high speed search mode to the reproduction mode at the same tape running speed as the time-lapse recording.
Moreover, by temporarily passing through the standard playback mode, which can shift to the final playback mode without generating noise, it is possible to prevent a sudden tape running speed deceleration in the tape running control and prevent the generation of noise. It will be possible.

[0049]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a reproducing system of an apparatus according to an embodiment of the present invention. The same parts as those in the conventional example shown in FIG.

FIG. 1 is a block diagram of FIG. 10. Further, a capstan motor 80 for driving a capstan that runs the tape while sandwiching the tape between the pinch roller and the pinch roller, and a rotational state of the capstan motor is magnetically detected. FG detector 81, AMP8 that amplifies the FG signal from the FG detector
2. The FG signal shaping circuit 83, which shapes the amplified FG signal into an FG pulse signal by waveform shaping, and 1/7 the FG pulse signal
Frequency divider 84 for dividing, fixed contact 85a to which this divided output is supplied and fixed contact 85b to which the FG pulse signal is directly supplied. Third switch 85, third switch 85 output The speed / phase control circuit 86 which receives the speed and executes the phase control of the capstan motor 80.
A series of circuits of a driver 87 for driving the capstan motor 80 based on the output of the speed / phase control circuit 86, an operation key 89 and a timer 90 are added.

Using the time-lapse VTR having the structure shown in FIG. 1 as a monitoring device, reproduction of a magnetic tape which has already been subjected to frame-by-frame recording at the speed for recording 1/3 of the standard recording or standard reproduction mode as described above. In the case of executing the above, when the VTR operator initially skips the monitoring confirmation operation in the fast-forward playback mode (CUE), that is, the high-speed search mode, and finds an intruder or changes in the main subject during this, The operation when the mode is immediately changed to the reproduction mode at the same tape speed as the frame skip recording speed will be described. In this embodiment, the tape running speed in the high speed search is set to 7 times the standard playback mode.

First, the operator operates the operation key 89 to C
When the UE mode is selected, the microcomputer 74 receives a signal from this operation key and receives the signal from the speed / phase control circuit 86 and the third
A mode signal indicating the CUE mode is issued to the switch 85.

Here, the speed / phase control circuit 86 is shown in FIG.
The configuration has a speed control system and a phase control system as shown in FIG. First, the speed control system includes a counter 102, a latch circuit 103, a comparator 104, a memory 105, a multiplier 106, and a fourth switch 107, and a divided or non-divided FG input from the third switch 85. In order to measure the period of the pulse signal, the counter 102 that counts the clock signal of the predetermined frequency is reset every time the FG pulse signal is input, and the counter 102 immediately before the reset is reset.
The count value of is latched in the latch circuit 103, and this latched data is input to the comparator 104 as the current speed data of the capstan motor 80.

The reference speed data obtained from the fourth switch 107 is supplied to the other input of the comparator 104. This fourth switch is a standard speed data D stored in the memory 105 in advance and capable of executing the standard reproduction mode.
Fixed contact 107a to which S is applied, and fixed contact 1 to which output of multiplier 106 that triples the standard speed data is applied
07b is switched, and the switching control of the fourth switch is executed by a mode signal from the microcomputer 74. When the mode signal indicates the CUE mode or the standard reproduction mode, the fixed contact 107a is selected and the frame removal is performed. In the case of instructing the so-called 1/3 standard reproduction mode, in which reproduction is executed while maintaining the same tape running speed as that at the time of recording, that is, 1/3 of the tape speed in the normal standard reproduction mode. , Fixed contact 107b is selected.

In this way, the comparator 104 compares the current speed data with the output of the fourth switch 107, and the difference between the two is output as a speed error signal.

On the other hand, the phase control system includes a counter 110, a latch circuit 111, a comparator 112, memories 113 and 114,
It is composed of a frequency divider 115 and fifth and sixth switches 116 and 117. A phase reference signal is applied to the fixed contact 116a of the fifth switch 116, and the phase reference signal is applied to the fixed contact 116b by 1/3 by the frequency divider 115. It is divided and applied, the fifth switch 116 is switched by the mode signal to reset the counter 110 that counts the clock signal of a predetermined frequency, and the latch circuit 111 in the subsequent stage resets the count value of the counter 110 by the reproduction control signal. By latching, for example, the fifth switch 116 is switched to the fixed contact 116a and the phase reference signal is directly input as the reset signal of the counter 110, the latch circuit 111 detects the phase difference between the phase reference signal and the reproduction control signal. Will be.

The mode signal of the fifth switch 116 is C
When the UE mode or the standard reproduction mode is instructed, the phase reference signal is switched to the fixed contact 116a, and when the 1/3 standard reproduction mode is instructed, the phase is switched to the fixed contact 116b side. A signal obtained by dividing the phase reference signal by 1/3 is selected.

The comparator 112 outputs the output of the latch circuit 111 to the sixth switch 117 of either of the memories 113 and 114.
The difference between the two is output as a phase error signal by comparison with the reference value obtained by selecting. Here, the memory 113
, The phase difference between the phase reference signal in the standard reproduction mode and the reproduction control signal is preset as a reference value, and the memory 114 stores the phase reference signal in the 1/3 standard reproduction mode as 1 The phase difference obtained by dividing the phase reference signal by / 3 and the reproduction control signal is set in advance as the reference value.

The phase reference signal is also used as a reference signal in a phase servo system of a cylinder motor (not shown).

The sixth switch 117 is switch-controlled by the mode signal. When the mode signal indicates the CUE mode or the standard reproduction mode, the sixth switch 117 is switched to the fixed contact 117a and the reference value in the memory 113 is selected. Three
When instructing the standard playback mode, the fixed contact 117b
The reference value in the memory 114 is selected.

The velocity and phase error data thus obtained are added by the adder 118 and then output to the driver 87 in the subsequent stage.

As described above, while the CUE mode signal is being issued, the fourth switch 107 is on the fixed contact 107a side and the standard speed data DS is selected, while the third switch 85 is on the fixed contact 85a side. Switch to frequency divider 8
The four outputs are supplied to the input terminal 101 of the speed / phase control circuit 86.

As a result, the counter 102 and the latch circuit 103 measure the period of the FG pulse signal divided by 1/7, compare this with the standard speed data DS, and use the difference between the two as a speed error signal in the driver 87. The capstan motor rotates at a speed of 7 times the standard playback speed, and accordingly, the tape is fed at a speed 7 times the tape speed in the standard playback mode, and the CUE mode of 7 times the speed is realized. It

Incidentally, the fifth and sixth switches 116 and 117.
Switches to the fixed contacts 116a and 117a, respectively, and phase control is applied.

In the CUE mode, the L-level control signal is always output from the microcomputer 74, and the second switch 70
Is fixed to the fixed contact 70b side, the cylinder 7
The heads B + and B- alternately serve as reproducing heads for each half rotation of, and as shown in FIG. 12 or FIG. 13, the head trace is executed in a state of straddling the tracks, and the signal is taken out from the portion where the azimuth angle matches. To be done.

Next, in this CUE mode, when the operator looks at the reproduction screen and finds an intruder or confirms that an abnormal state has occurred in the main subject, he / she operates the operation key 89 to / 3 Command the mode transition to the standard playback mode.

Upon receiving this mode shift command, the microcomputer 74 does not shift to the 1/3 standard playback mode suddenly, but first controls the standard playback mode to execute the standard playback mode by speed / phase control. Circuit 86,
Output to the third switch 85 and the timer 90.

The third switch 85 receives the mode signal instructing the standard reproduction mode, and immediately thereafter, the fixed contact 85b.
Then, the FG pulse signal is output to the speed / phase control circuit 86 without frequency division. On the other hand, in the speed / phase control circuit 86, in the speed control system, even if this mode signal is received, the fourth switch 107 still switches to the fixed contact 107a and selects the standard speed data DS. As a result, the counter 102 and the latch circuit 10
In 3, the capstan motor 80 rotates at a speed that matches the standard speed data most suitable for the standard playback mode by measuring the cycle of the FG pulse signal and comparing it with the standard speed data DS to create a speed error signal. To do.

In the phase control system, the fifth switch 11 receives the mode signal indicating the standard reproduction mode.
6 holds the fixed contact 116a side, the counter 110 is reset by the phase reference signal, the latch circuit 111 detects the phase difference between the phase reference signal and the reproduction control signal, and at the same time, the sixth switch 117 also fixes the fixed contact 117a.
And the reference value for the standard reproduction mode is output to the comparator 112, the phase error signal is output so that the phase difference matches the reference value, and the optimum phase servo is applied to the standard reproduction mode. Will be. In this way, the standard speed mode is realized.

In this standard reproduction mode, the video signal is continuously recorded without frame skipping, and the tape running speed is three times as fast as when the frame skip recording is performed (for example, 11.1 m).
(m / sec), the same operation as in the case of sequentially tracing tracks formed by normal recording with heads having different azimuth angles is performed. That is, as in the CUE mode, the first switch 70 causes the movable contact piece 60e to move to the fixed contacts 60a, 60 according to the switching pulse every half rotation of the cylinder 7.
b, and the movable contact piece 60f switches to fixed contacts 60c and 60d at the same time.
In this standard reproduction mode, the L level control signal is constantly output to the second switch 70, and the movable contact piece 70bc is constantly switched to the fixed contact 70b while this mode is maintained. The output of the piece 60e is not used, and it is the head B that is input to the video signal processing circuit 71.
The signals of + and the output of the head B- are alternately selected every half rotation of the cylinder 7.

By the way, in the standard reproduction mode,
The magnetic tape to be reproduced is the one in which the video signal is recorded without frame recording, and the pitch of the tracks formed in this frame recording is the same as the track pitch in the above-mentioned normal recording. Therefore, the head B +, It is possible to reproduce the video signal by sequentially tracing the tracks adjacent to B- alternately. In this case, since the magnetic tape in the frame-free recording is recorded by selecting only one field out of three fields of the video signal, the video signals V1, V4,
V7 ... are sequentially reproduced for each field, and a reproduction screen like triple speed is obtained.

As a result of this mode transition, as shown in FIG. 12 or 13, the tape feed is decelerated by 1/7 from 7 times to 1 times the standard speed. The control system is able to follow sufficiently, and the screen is not disturbed immediately after the transition. 12 and 13
As in FIG. 7, the horizontal axis represents time and the vertical axis represents tape running amount.

The timer 90 starts timing with a time point when the mode signal indicates the standard reproduction mode as a trigger, and when a preset time reaches t, a completion signal is sent to the microcomputer 74.
When the completion signal is input, the microcomputer 74 immediately instructs the mode signal to the 1/3 standard reproduction mode in order to realize the mode transition from the standard reproduction mode to the 1/3 standard reproduction mode. Switch.

Here, the time t is the time at which it is predicted that the speed / phase control of the capstan will be sufficiently stable due to the shift to the standard reproduction mode, and usually 200 msec to 300 msec.
Arbitrary time of ms is set.

In the speed / phase control circuit 86, when the mode signal instructing the 1/3 standard reproduction mode is input, the speed control system switches the fourth switch 107 to the fixed contact 107b side to output from the multiplier 106. The speed data, that is, the data for 1/3 standard reproduction which is three times the standard speed data DS is selected, the comparator 104 compares the speed data with the cycle of the FG pulse signal, and the difference between them is regarded as the speed error signal. By doing so, the capstan motor 80 will rotate at a speed of 1/3 of the standard reproduction mode, and the tape feeding will also follow the speed at a speed of 1/3 of the standard reproduction mode.

On the other hand, when the mode signal indicates the 1/3 standard reproduction mode, the fifth and sixth switches 1 in the phase control system.
16, 117 are respectively switched to the fixed contacts 116b, 117b side, the frequency division output from the frequency divider 115 is selected as the reset signal of the counter 110, and the reference value of the memory 114, that is, 1 / 3 A reference value for standard playback mode is selected.

As a result, in the 1/3 standard reproduction mode, the tape running speed becomes 1/3 of the standard reproduction mode, and the frequency of the reproduction control signal is also 1/3 of the standard reproduction mode.
However, the frequency of the phase reference signal is 1 in the standard playback mode.
Therefore, the latch circuit 111 can accurately measure the phase difference between the reference phase signal and the reproduction control signal. Further, a phase error signal is obtained so that the phase difference between the two thus obtained matches a reference value suitable for the 1/3 standard reproduction mode, and optimum phase servo is given to the 1/3 standard reproduction mode. become.

At the time of this mode transition, the microcomputer 74 first issues an L level control signal to the second switch 70 so that the head switching pattern starts from the state of (c) or (f) of FIG. The second switch 70 is forcibly switched to the fixed contact 70b side.

The first switch 60 includes movable contact pieces 60e, 6
Fixed contact 60 when 0f shifts to 1/3 standard playback mode
If the second switch 70 is forcibly switched to 70b in the case of switching to the a or 60c side, the head B + is selected as the reproducing head, and the state of (f) of FIG. 6 is realized. To be done. Based on the switching pulse and the reproduction control signal, the microcomputer 74 starts L →
The control signal level is changed in the above-described order of H → H → L → H → H → L → ..., and accordingly, the trace pattern is (f) → (a) → (b) → ( c) → (d) → (e)
The predetermined head switching is sequentially performed in the order of → (f) → ..., and a 1/3 standard reproduction mode without noise is realized. Incidentally, FIG. 13 shows the relationship between this mode transition and the head used as a reproducing head.

Further, when the first switch 60 is switched to the fixed contacts 60b and 60d side when shifting to the 1/3 standard reproduction mode, the second switch 70 is forced to 7
When switched to 0b, the head B- is selected as the reproducing head, and the state of FIG. 6C is realized.
After that, the control signal level is changed in the above-described order of L → H → H → L → H → H → L → ..., and accordingly, the trace pattern is (c) → (d) → of FIG. (E) → (f) →
Predetermined head switching is sequentially performed in the order of (a) → (b) → (c) → ..., and a 1/3 standard reproduction mode without noise is realized.

FIG. 12 shows the relationship between this mode transition and the head used as the reproducing head. 12 and 13, (a) shows the head to be used, and (b) shows which pattern of (a) to (f) in FIG. 6 corresponds to the 1/3 standard reproduction mode. , (C) indicate operation modes.

As described above, when the mode is changed from the standard reproduction mode to the 1/3 standard reproduction mode, the reference speed data and the phase reference value of the speed / phase control circuit 86 are switched to reduce the tape traveling speed to 1/3. It just slows down,
The capstan motor 80 can quickly follow the mode transition, and the head switching is instantaneously executed during the transition so that the reproduction pattern starts from (c) or (f) in FIG. There is no.

In the present embodiment, the circuit configuration as shown in FIG. 1 is used. However, for example, in FIG. 1, the processing of the components within the broken line may be performed by a single microcomputer as software. It goes without saying that it is possible.

Further, in the apparatus of the above-described embodiment, the frame skipping recording is performed in which one field is extracted in three fields, but the present invention is not limited to this, and one in five fields.
2 fields, 1 field in 7 fields
It is also possible to skip one field in the n + 1 (n: positive integer) field. In this case, the tape speed in the frame skip recording or the lowest reproduction mode is 1 in the standard reproduction mode.
/ N. Further, the double speed number in the CUE mode is not limited to 7 times as in the above embodiment, and m
(M: positive integer) double speed is possible, and in this case, the frequency division ratio of the frequency divider 84 needs to be 1 / m.

Further, in the above-described embodiment, the case where the phase difference between the reproduction control signal and the switching pulse is zero has been described. However, for example, phase control is performed so that the reproduction control signal maintains a predetermined phase difference with respect to the switching pulse. It is needless to say that, if provided, it is possible to change the level of the control signal from the edge of the first switching pulse generated after the input of the reproduction control signal in a preset order. .

[0086]

As described above, according to the present invention, when the mode is changed from the high speed search mode to the 1 / n standard reproduction mode, the high speed search mode is once changed to the standard reproduction mode, and then the standard reproduction mode is changed. By gradually reducing the tape running speed to the low speed reproduction mode in which the track pitch is equal to the standard reproduction mode, the tape speed control can quickly follow the mode transition. Also, in the standard playback mode, the video signal can be played back from the time-lapse recording magnetic tape, so the playback screen can always be checked during this gradual mode transition, and the transition from the standard playback mode to the low-speed playback mode is possible. The heads can be easily switched in a preset order regardless of the azimuth of the immediately preceding reproducing head, and noise does not occur at the time of switching.

[Brief description of drawings]

FIG. 1 is a block diagram of one embodiment of the present invention.

FIG. 2 is a block diagram of a recording system for frame-free recording.

FIG. 3 is a timing chart of a recording system for frame-free recording.

FIG. 4 is an operation explanatory diagram of frame-out recording.

FIG. 5 is a conventional example of a reproducing system of a magnetic tape on which frame-free recording is performed.

FIG. 6 is an explanatory diagram of a head trace for frame-free recording.

FIG. 7 is an explanatory diagram of an operation of frame-out recording.

FIG. 8 is an explanatory diagram of control signals.

FIG. 9 is a waveform diagram illustrating a reproduction system of a magnetic tape on which frame-free recording is performed.

FIG. 10 is a block diagram of a conventional example.

FIG. 11 is a block diagram of an essential part of an embodiment of the present invention.

FIG. 12 is a diagram illustrating a track trace at the time of mode transition according to an embodiment of the present invention.

FIG. 13 is a diagram illustrating a track trace at the time of mode transition according to an embodiment of the present invention.

FIG. 14 is a diagram illustrating a track trace pattern in a standard reproduction mode according to an embodiment of the present invention.

[Explanation of symbols]

 86 Speed / Phase Control Circuit 74 Microcomputer 89 Operation Button 90 Timer 60 First Switch 70 Second Switch

Claims (2)

[Claims] 1. A magnetic field in which a video signal for one field in (2n + 1) fields (n is a positive integer) is periodically extracted and sequentially recorded at different first and second azimuth angles for each track. A tape is disposed near the first head having the first azimuth angle and the second head.
A first head group including a second head having an azimuth angle, a third head having a second azimuth angle facing the first head, and the first head having a third head having a second azimuth angle. It is wound around a cylinder having a second head group consisting of a fourth head having an azimuth angle and reproduced,
In the n standard playback mode, in a video tape recorder in which heads of the same azimuth in both head groups alternately scan the same track n times, the tape running speed is set to the first speed in the standard playback mode.
/ N to a second speed which is 1 / n of the first speed in the standard reproduction mode, and to m (m is an integer) of the first speed in the high speed search mode.
Tape running control means for controlling the double speed to a third speed, and mode setting means for setting the operation mode of the tape running speed control means to any one of the standard playback mode, the 1 / n standard playback mode and the high speed search mode. At the time of mode transition from the high speed search mode to the 1 / n standard reproduction mode, the mode setting means issues a first mode transition command to the traveling speed control means to switch from the high speed search mode to the standard reproduction mode, and the first mode transition command. Is issued for a predetermined time t and then a second mode transition command for switching from the standard reproduction mode to the 1 / n standard reproduction mode is issued. 2. A first switch means for alternately selecting one of the output of the first head group and the output of the second head group for every 1/2 rotation of the cylinder, and the first head. A first state in which the first head output is selected as the output of the group, the third head output is selected as the output of the second head group, and the second head output is selected as the output of the first head group; In the 1 / n standard reproduction mode, the second switch means is provided with second switch means for selectively switching to a second state for selecting the fourth head output as the output of the second head group. , Starting from a track having a predetermined positional relationship with a reproduction control signal obtained when reproducing the magnetic tape, a preset first period is switched to the first state, which is different from the first period. Preset Video tape recorder according to claim 1, wherein the second period of time, characterized in that switching to the second state.