JPH0132707B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a video signal reproducing apparatus applied to high-speed reproduction (picture search) in which the tape speed during reproduction is sufficiently faster than that during recording, for example, in a rotating two-head VTR.

When performing a picture search in which a magnetic tape is wound around the circumference of a rotating head and fast-forwarded or rewound, the tape speed becomes about 20 times that of recording, and the frequency deviation of the horizontal synchronization signal due to changes in relative speed increases. The horizontal synchronization of the receiver will no longer lock. During fast forwarding, if the running direction of the tape and the rotating direction of the rotary head are the same, the faster the tape speed, the slower the relative speed becomes.In the case of rewinding, on the contrary, the relative speed becomes faster. If the fast-forward playback operation is referred to as queue and the rewind playback operation is referred to as review, the deviation of the horizontal frequency (f _h ) of the reproduced horizontal synchronizing signal will decrease by approximately 6% in the queue operation and approximately 6% in the review operation. Rise.
Therefore, during picture search, the rotation speed of the head drum is changed to reduce the deviation of f _h . As a result, the frequency of the reproduced vertical synchronization signal shifts by about 6%, but this does not cause any problem because the vertical synchronization lock range of the receiver is wide.

FIG. 1 shows an example of a drum servo circuit that takes such picture search into consideration. In the figure, reference numeral 1 indicates a drum motor configured as a DC motor, for example, and the output of an adder 2 is supplied to the motor 1 as a drive voltage. As shown surrounded by broken lines, a phase servo circuit 3 and a speed servo circuit 4 are provided in association with the motor 1. Also, 5
indicates a pick-up coil. Two magnets are arranged on the rotating head drum at an angular interval of 180°, and a detection signal PG is generated each time these magnets approach the pickup coil 5. PG via amplifier (not shown)
A detection signal PG is supplied to the discrimination circuit 6. The magnetization directions of the two magnets are opposite to each other,
If the detection signal from one magnet changes from positive to negative, the detection signal from the other magnet changes from negative to positive, and these two are treated as separate pulses PGa and PGb, and the PG half circuit 6
arises from. A flip-flop 7 is provided which is set by the pulse PGa and reset by the pulse PGb, and the output of the flip-flop 7 whose phase is synchronized with the rotating head is fed to the phase servo circuit 3.
and is supplied to the speed servo circuit 4.

60 for phase servo circuit 3 from the terminal shown as 8
A servo reference signal in Hz is provided. At the time of recording,
The vertical synchronization signal is used as a reference signal, and during reproduction, a 60Hz signal obtained by counting down the color subcarrier is used as the reference signal. This servo reference signal is supplied to a slope signal (gradient wave) generator 10 via a 1/2 frequency divider 9, and the generated slope signal is supplied to a gate 11. On the other hand, the output pulse of the flip-flop 7 is supplied to the sampling pulse generator 13 via the delay circuit 12, the generated sampling pulse is supplied to the gate 11, and the gate output is supplied to the hold circuit 14. This hold circuit 1
4 is a phase error signal, which is applied to the adder 2 via the input terminal 16a and output terminal 16b of the changeover switch 15.

The speed servo circuit 4 supplies one output of the flip-flop 7 to a slope signal generator 19 via a delay circuit 18, and also supplies one output of the flip-flop 7 to a slope signal generator 19.
The other output is supplied to the sampling pulse generator 20, the slope signal is sampled by the sampling pulse at the gate 21, and the output is held at the hold circuit 22. The output of this hold circuit 22 is supplied to the adder 2.

By means of the phase servo circuit 3 and speed servo circuit 4 as described above, the rotational phase and rotational speed of the rotary head are set to predetermined values. During picture search, the other input terminal 16b of the changeover switch 15
and the output terminal 16c are connected, the system of the phase servo circuit 3 is disconnected, and a speed control signal for picture search is supplied to the adder 2. A control signal indicating whether a picture search (queue or review) is to be performed is applied to the changeover switch 15 from a terminal 17.

The speed control signal for picture search is connected to terminal 2.
3 is formed by frequency discriminating the control signal supplied to the frequency discriminator 24.
The control signal is recorded at a predetermined pitch on, for example, a lower control track along the longitudinal direction of the magnetic tape. Therefore, a control signal with a frequency proportional to the running speed of the magnetic tape is generated, and the frequency discriminator 24 generates a control signal with a frequency proportional to the running speed of the magnetic tape. A discrimination output of a level proportional to the traveling speed generated by the vehicle is supplied to the polarity divider 25. Outputs of opposite polarity from the polarity divider 25 are respectively supplied to two input terminals of a changeover switch 26, and the output terminals are connected to the variable gain amplifier 2.
8 input terminals. Changeover switch 26
is controlled by supplying control signals to the terminals 27a and 27b that are generated during the queue operation and the review operation, respectively. During the queue operation, a polar speed control signal that increases the rotational speed of the drum motor 1 is selected, and the review operation is performed. In operation, a speed control signal with a polarity that lowers this rotational speed is selected. The gain of the variable gain amplifier 28 is switched by a changeover switch 29. In this example, the tape speed during recording is, for example, 20 [mm/sec].
There are two possible options: 13.3 [mm/sec].
Therefore, the pitch of the control signal recorded between the two is different. On the other hand, since the tape speed at the time of picture search is irrelevant, a changeover switch 29 is provided to correct it. The tape speed during recording is automatically determined, and a control signal based on the determination is supplied from the terminal 30 to control the changeover switch 29.

With the configuration shown in FIG. 1 described above, the number of revolutions of the rotary head during picture search is controlled, changes in relative speed are suppressed, and the horizontal synchronizing signal in the reproduced signal is brought to approximately the normal frequency. By the way, in the servo circuit shown in FIG. 1, it is necessary to provide a changeover switch 26 that can be changed over for cue and review, and a changeover switch 29 that can be changed over depending on the tape speed during recording, and control signals for these changeover switches must be provided. need to be supplied,
There is a problem that the configuration is complicated. In addition, the control signal is reproduced from a magnetic tape run by a capstan and a pinch roller,
Fluctuations in the rotational speed due to variations in the drum load, etc., do not appear as frequency fluctuations in the control signal, and as a result, there has been a drawback that correction of fluctuations in the horizontal frequency f _h is insufficient.

An object of the present invention is to realize a video signal reproducing device in which such problems are solved.

Hereinafter, an embodiment of the present invention applied to a rotating two-head type VT will be described with reference to the drawings. In this embodiment, the drum motor 1 is driven by the output of an operational amplifier (operational amplifier) 31. A speed control signal from the speed servo circuit 4 is supplied to a non-inverting input terminal of the operational amplifier 31, and a signal via a changeover switch 15 is supplied to its inverting input terminal. The operational amplifier 31 is
This corresponds to adder 2 in FIG. The changeover switch 15 has three input terminals 16a, 16b, 16
c and an output terminal 16d, the connection state of which is controlled by a switching signal from the terminal 17. During normal playback, the phase control signal applied to the input terminal 16a is selected, during picture search, the speed control signal applied to the input terminal 16b is selected, and during slow motion playback, the signal from the terminal 32 to the input terminal 16c is selected. The applied speed control signal is selected.

The playback output from the rotary head is supplied to the input terminal 33 shown in FIG. The signal is supplied to a separation circuit 36. Synchronous separation circuit 35
The horizontal sync signal _Ph separated by Sampled by Ph. The output of the gate 40 is supplied to a hold circuit 41, from which a speed control signal SV ₂ for picture search is generated and supplied to the input terminal 16b of the changeover switch 15.

Horizontal sync signal separated from playback video signal
Assuming that Ph is as shown in FIG. 3A, the monomulti 37 is triggered at the rising edge, and _{the pulse P 1 shown} in FIG. A pulse P ₂ shown in Figure C is generated, and a slope signal SV ₁ whose level gradually decreases in the positive section of this pulse P ₂ is formed as shown in Figure D. Slope signal SV ₁
is sampled by the horizontal synchronizing signal Ph, thereby forming the speed control signal _SV2 as shown in FIG. 3E. The time constant of monomulti 37, 38 is
The frequency f _h of the horizontal synchronization signal Ph is normal (f _h0 )
In this case, the value is selected so that approximately the center of the slope section of the slope signal is sampled. If the horizontal frequency f _h becomes lower than f _h0 , the level of the speed control signal SV ₂ decreases, and the operational amplifier 3
The level of the motor drive signal originating from SV 1 is increased and the rotational speed of the rotary head is increased, and vice versa, the level of the speed control signal SV ₂ is increased and the rotational speed of the rotary head is decreased.

In this way, according to the present invention, when the relative speed between the magnetic tape and the rotary head changes, as in the case of picture search, the horizontal frequency f _h deviates from the normal value f _h0 , causing the horizontal synchronization of the receiver. This can prevent the lock from becoming locked. Unlike the servo circuit shown in Figure 1, the queue and review switch,
There is no need to provide a changeover switch related to the tape speed during recording, and the configuration can be simplified. However, since uneven rotation of the rotary head due to load fluctuations and the like also appears as frequency fluctuations in the horizontal synchronizing signal, it is possible to remove horizontal frequency deviations with high precision.

Furthermore, correction of the horizontal frequency during slow motion reproduction in the above-described embodiment of the present invention will be described below. In this example, the slow motion reproduction method is such that the magnetic tape is advanced intermittently, and still reproduction and normal reproduction are performed alternately. For example, if still playback (field still or frame still) is performed for two frame periods and then normal playback is performed for one frame period, playback can be performed at a slow speed of 1/3. When the magnetic tape is intermittently fed in this way, the relative speed is higher during still playback than during normal playback, and a deviation in the horizontal frequency f _h occurs. This deviation is
Even if it is within the horizontal synchronization lock range of the receiver, if it occurs repeatedly in a short period as described above,
The width of the slow-motion playback image changes periodically. Therefore, in the embodiment described above, the rotational speed of the drum motor 1 is accelerated or decelerated in conjunction with the signal for driving the capstan motor to eliminate the above-mentioned deviation.

FIG. 4 shows an example of a capstan serve circuit for slow motion reproduction. In FIG. 4, reference numeral 42 indicates a capstan motor configured as a DC motor, and this capstan motor 42
A motor drive circuit 43 is provided in connection with this. Transistors 44a and 44b for supplying the forward drive current _ID to the capstan motor 42 as shown by the solid line, and transistors for supplying the reverse drive current _-ID to the capstan motor 42 as shown by the broken line. 45a and 45b constitute a motor drive circuit 43. The reverse drive current is used as a brake to properly stop the capstan motor 42 at a predetermined position. The transistors 44a and 44b are turned on by the normal rotation pulse FP ₂ generated from the normal rotation monomulti 50, and the transistors 45a and 45b are
Reverse pulse generated from brake monomulti 56
Turned on by RP ₂ .

RF switching pulse SWP is connected to the terminal indicated by 46.
is supplied. In this example, a pair of rotary heads HA and HB arranged at an angular interval of 180 DEG and a rotary auxiliary head HA' for field still reproduction are provided. To prevent crosstalk from adjacent tracks, sloped azimuth recording is performed.
The inclinations of the working gaps of the rotary heads HA and HB with respect to the line perpendicular to the scanning direction of the heads are made different from each other, and the rotary heads HA and the auxiliary heads
The above slope with HA' is assumed to be the same. Approximately one field of the video signal is alternately recorded by the rotating heads HA and HB. Means for detecting the rotational phase of this rotary head is provided, and the switching pulse shown in FIG. 5A is generated from this detection output.
SWP is formed. Switching pulse SWP
has a period of one frame, and its falling edge triggers the slow speed monomulti 47. In FIG. 5A, each head HA, HB,
The scanning period of HA′ is entered. A time constant circuit 48 is provided in association with the slow speed monomulti 47, and its time constant is determined by a slow speed volume 49 that changes in accordance with the slow speed (1/N). In this example, (N=3), therefore, the monomulti 47 generates a pulse FP ₁ having a pulse width longer than two frame periods and not exceeding three frames, as shown in FIG. 5B.

The output pulse FP ₁ of the monomulti 47 is supplied to the normal rotation monomulti 50, the rising edge of which coincides with the pulse FP ₁ , and a normal rotation pulse FP ₂ having a pulse width Tf is generated. This pulse width Tf is determined by the time constant circuit 51. This normal pulse FP ₂ is supplied to the bases of transistors 44a and 44b via base resistors, respectively.

Further, a reproduced control signal CTL is supplied to a terminal indicated by 52. control signal
CTL is a normal rotation pulse FP ₂ as shown in Fig. 5D.
This occurs when the magnetic tape is run at normal speed. This control signal CTL triggers the delay monomulti 53, which generates a pulse RP ₁ having a pulse width of τ as shown in FIG. 5E. delay mono multi 53
In conjunction with this, a tracking volume 55 is provided in the time constant circuit 54 to vary the time constant and change the pulse width τ. A brake monomulti 56 is provided which is triggered by the falling edge of the output pulse RP ₁ of the delay monomulti 53. The time constant circuit 57 associated with the brake monomulti 56 generates a reversal pulse as shown in FIG.
The pulse width Tr of RP ₂ is defined. This reverse pulse RP ₂ is supplied to the bases of transistors 45a and 45b of motor drive circuit 43 via base resistors, respectively.

Forward rotation pulse FP ₂ (Fig. 5C) and reverse rotation pulse
Capstan motor 4 by RP ₂ (Fig. 5F)
2 is supplied with a drive current _ID as shown in FIG. 5G. In the positive section of the drive current I _D , the capstan motor 42 is driven in the forward rotation direction, the tape is run at the normal speed, and the positive drive current
Even if I _D disappears, the capstan motor 42 continues to rotate due to its inertia, and is rapidly braked by the negative drive current - I _D , and the tape is held at a predetermined position. Stop. This stop position is set so that the level of the reproduction output is at its maximum approximately at the center of one field. If a noise band appears in the center of the slow motion image due to a low level of reproduction output, the tracking volume 55 changes the pulse width τ and adjusts the stop position.

Note that if there are two possible tape speeds during recording, the pitch of the video track will also differ accordingly, so which recording has been performed can be automatically determined from the frequency of the control signal, for example.
Depending on the determination, the time constants of the time constant circuits 51 and 57 are switched, and the pulse width Tf of the forward rotation pulse FP ₂ and the pulse width Tr of the reverse rotation pulse are respectively set to appropriate values.

A monomulti 58 that is triggered by the rising edge of the forward rotation pulse FP ₂ and a monomulti 59 that is triggered by the rising edge of the reverse rotation pulse RP ₂ are provided. Drum shift pulse SF shown in Figure I
and SR occurs. These shift pulses SF and
The pulse width of SR is narrow, for example, about 10 [ms], and the switches 61 and 62 of the speed control voltage generation circuit 60 are turned on during the period when the shift pulses SF and SR are at high level. A series circuit of resistors 63 and 64 is inserted between the power supply terminal and the ground, and the connection point between the two is connected to the output terminal 32 of the speed control voltage.
It is derived as This terminal 32 is connected to the input terminal 16c of the changeover switch 15 of the drum servo circuit shown in FIG. Further, a series circuit of a resistor 65 and a switch 62 is connected in parallel with the resistor 63, and a series circuit of a switch 61 and a resistor 66 is connected in parallel with the resistor 64.

Such a speed control voltage generation circuit 60 operates at a terminal 32 when both switches 61 and 62 are off.
A predetermined speed control voltage V ₀ is generated. here,
When the switch 61 is turned on by the drum shift pulse SF, the resistors 64 and 66 are connected in parallel, and the speed control voltage V ₁ at that time becomes (V ₁ <V ₀ ).
This increases the output level of the operational amplifier 31 and accelerates the drum motor 1. Further, when the switch 62 is turned on by the drum shift pulse SR, the resistors 63 and 65 are connected in parallel, and the speed control voltage V ₂ at that time becomes (V ₂ >V ₀ ). is slowed down. In this way, the pulse SF eliminates the deviation in the horizontal frequency f _h due to the relative speed between the magnetic tape and the rotating head not returning to the normal speed immediately after the change from still playback to normal playback. Also,
The pulse SR eliminates the deviation in the horizontal frequency f _h due to the increase in relative speed when still playback occurs. Therefore, the horizontal frequency f _h as shown by the broken line in FIG. 5 J that occurs during slow motion reproduction
After removing the fluctuation of
It can be f _h0 .

[Brief explanation of drawings]

Fig. 1 is a block diagram of an example of a video signal reproducing device, Fig. 2 is a block diagram of an embodiment of the present invention, Fig. 3 is a waveform diagram of each part used to explain its operation, and Fig. 4 is an embodiment of the present invention. FIG. 5 is a block diagram of a servo circuit for slow motion reproduction in this example, and is a waveform diagram of each part used for explanation. 1 is a head drum motor, 3 is a phase servo circuit, 4 is a speed servo circuit, 5 is a pickup coil, 15 is a changeover switch, 33 is an input terminal for playback output, and 36 is a synchronization separation circuit.

Claims (1)

[Scope of Claims] 1. A video signal reproducing device that performs normal playback, high-speed playback, and slow playback using intermittent playback, comprising: a motor that drives a rotating head; a speed servo circuit that detects the rotational speed of the rotating head; A phase servo circuit that detects the rotational phase of the rotating head, a detection circuit that detects the frequency deviation of the horizontal synchronizing signal separated from the video signal obtained from the rotating head, and an RF switching pulse during intermittent slow playback. and a speed control voltage generation circuit which outputs a predetermined voltage based on a signal obtained corresponding to the tape feeding speed and which causes the capstan motor to rotate forward or reverse; an output signal of the phase servo circuit, and an output signal of the detection circuit. and a switch circuit that switches and outputs the output signal of the speed control voltage generation circuit according to normal playback, high-speed playback, and slow playback, respectively, and the output signal of the speed servo circuit and the switch circuit. A video signal reproducing device that controls rotation of the motor based on an output signal of the motor.