JPS60113348A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To make noiseless still reproduction with high accuracy by comparing the phase difference between a recorded vertical synchronizing signal and a head changing signal, and detecting the point of time when the phase difference signal changes sharply and thereby controlling running of a tape. CONSTITUTION:A magnetic tape 1 is rotated at a constant speed by a capstan motor 5 through a capstan servo circuit 51. Magnetic heads 21, 22 that record video signals from a video signal recording circuit 61 alternately in the magnetic tape 1 for each field obtain pulses synchronized with rotation from a tack head 3. The DTP signal is supplied to a pulse forming circuit 32 by a phase adjusting circuit 31. Video signals from a terminal 10 are supplied to a vertical synchronizing signal separating circuit 101, and the vertical synchronizing signal VF is phase compared with rising phase of pulse S from the pulse forming circuit 32. The phase error signal is supplied to a disk motor 4 through a disk servo circuit 41 and phase controlled.

Description

Detailed Description of the Invention [Field of Application of the Invention] The present invention relates to a VTR equipped with a device for obtaining a noiseless reproduced image by tracking the occurrence position of a noise bar that appears on a screen VC during still reproduction into a vertical blanking period of a reproduced video signal.
The present invention relates to magnetic recording and reproducing devices such as the above.

[Background of the invention]

In conventional rotary head type VTRs, a still playback function is generally used to play back still images by temporarily stopping the running of the magnetic tape. During still playback, the magnetic tape is stationary, so the trajectory of the video head scanning the video track is different from that during normal playback.

For this reason, depending on the position at which the magnetic tape is stopped, a strip-shaped portion with a poor SIN ratio, that is, a noise bar, appears on the playback screen. Therefore, in order to perform noiseless still playback by forcing the generation position of this noise bar into the vertical blanking period of the reproduced video signal, in the conventional magnetic recording and reproducing device, the V ratio becomes bad because the level of the reproduced video signal is small. A commonly used method is to detect the sharp drop of a noise bar on a playback screen and to stop the running of the tape so that the position of the noise bar and the phase of the head switching signal are in a constant relationship.

However, this method of detecting dropout has the disadvantage that the accuracy of detecting the position of the noise bar is low because it depends on the amplitude drop of the reproduced video signal, and the accuracy of stoppage control of tape running is therefore low. Therefore, a new method with good stability was needed.

[Purpose of the invention]

In view of the above-mentioned drawbacks of the prior art, an object of the present invention is to detect the position of a noise bar on a vertical block of a reproduced video signal, in place of the method of detecting dropouts that has been conventionally used for stop control during still playback. There is a VC that provides a new means for performing noiseless still playback with full accuracy without noise bars appearing on the playback screen within the ranking period.

[Summary of the invention]

In order to accomplish the above-mentioned objectives f-h, the present invention compares the phase difference between a vertical synchronization signal recorded on a magnetic tape and a head switching signal during still playback, and detects the point in time when the phase difference signal changes sharply. By doing this, the tape running is controlled to stop so that the position of the noise bar appearing on the playback screen is forced into the vertical blanking period of the playback video signal.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in detail using all the drawings.

FIG. 1 is a block diagram showing a configuration example of a rotating head helical scan type magnetic recording/reproducing apparatus according to the present invention, and FIG.
The figure is a waveform diagram of each part.

The magnetic tape 1 is driven to run by a capstan motor 5, and the capstan motor 5 is driven to rotate at a constant speed by a capstan servo circuit 51.

Reference numerals 21 and 22 indicate magnetic heads that alternately record video signals from the video signal recording circuit 61 on the magnetic tape 1 field by field.
It is rotated and driven. Although not shown, a magnet is attached to the disk 2Vc, and by detecting this with the tack head 3, the magnetic head 21.22
A pulse synchronized with the rotation of the disk (hereinafter referred to as a disk tack pulse (abbreviated as DTP)) is obtained from all tack heads 3. The DTP signal from this tack head 3 is
The phase adjustment circuit 31 adjusts the phase of the magnetic head 21, 22 and the magnetic tape 1 so that they have a predetermined relative positional relationship, and then the signal is supplied to the pulse forming circuit 32. This pulse forming circuit 52 outputs a pulse S with a duty ratio of 50% in synchronization with the DTP signal.

Reference numeral 10 denotes a terminal to which a video signal to be recorded is supplied. The video signal from this terminal 10 is supplied to a vertical synchronizing signal separation circuit 101, which separates a vertical synchronizing signal VS and outputs it. This vertical synchronization signal VS is down-done to a frequency of 172 by a frequency down-down circuit 102, and the circuit 102 outputs multiple vertical synchronization signals VF having a frame period. This vertical synchronization signal VF is phase-compared with the rising phase of the pulse S from the pulse forming circuit 32 in a phase comparison circuit 42, and a phase error signal corresponding to the phase difference between the two is outputted to the circuit 42.
is output. This phase error signal is supplied to the disk motor 4 via the disk servo circuit AI'i, so that the disk motor 4 is driven at a rotational speed equal to the frame frequency, so that the frequency of the pulse S is equal to the frame frequency.

In this way, as shown in FIG.
The phase of the disk motor 4 is controlled so that the phase difference between the pulse S and the rising phase of the pulse S is a constant time of 1x.

FIG. 5 is a diagram showing a part of a pattern of video tracks recorded and formed on the magnetic tape 1 by one or more servo controls during recording. In the figure, Ho is the scanning start point of the magnetic head on the magnetic tape, and thereafter the magnetic head scans the magnetic tape to create a video track T. Fully formed. C indicates the scanning center line at this time. The relative relationship between this scanning start point Ho and the magnetic tape end A is determined by the relative positional relationship between the disk 2 and the magnetic tape 1 in FIG. It is located on line F at a position on the tape a certain distance away from . So is a point where the phase of the rising edge of the pulse S corresponds to the position on the video track 1o, and the relative positional relationship between this 50 and the magnetic tape end A is determined by the phase adjustment circuit of FIG. 31, which 50 is located on line G at a position on the tape a fixed distance from end A of the magnetic tape. Vo is the video track T of the vertical synchronization signal. The above recording position is shown, and as is clear from the waveform diagram in FIG.
The recording position r0 is a point corresponding to a phase difference of a certain time tx from a point S0 corresponding to the rising phase of the pulse S, and is located on a line F at a position on the tape a certain distance away from the end A of the magnetic tape.

The video track T thus formed. If we consider the case where a tracking deviation sound occurs during complete reproduction and reproduction is performed at the scanning center line shown in CI in the figure, the scanning start point of the magnetic head is located at point H82 on the BffM mentioned above, and the pulse S is The rising phase is located at the SIo point on the G line,
As a result, the vertical synchronization signal V is reproduced. The special training of the phase difference between the rising phase of the pulse S and the rising phase of the pulse S appears as ii. That is, by detecting the phase difference time 1x between the vertical synchronizing signal and the rising phase of the pulse S, the video track To
The position of the scanning center line C of the magnetic head that scans can be known.

Next, the operation of magnetic tape stoppage control during noiseless still playback according to the present invention will be described. Figure 4 α is
FIG. 3 is a diagram showing the scanning trajectory of the magnetic heads 21 and 22 during still reproduction. At +A, magnetic head 21, B
O+B1 indicates a track recorded by the magnetic head 22. Since the two magnetic heads have different azimuth angles, only recorded tracks having the same azimuth angle are reproduced.

When tape running stops during still playback, the scanning trajectory of the magnetic head tilts in the tape running direction compared to during normal playback.
As shown in FIG. 4a, the video is played back across two adjacent video tracks.

Therefore, the magnetic heads 21 and 22 scan the same location. Figure 4 shows the reproduction envelope from the magnetic head at this time, and Figure C shows the head switching signal,
d and - in the figure show FM demodulated video signals when the scanning trajectory of the magnetic head coincides with Y and X of α in the figure, respectively. Note that d in the figure shows only the vertical synchronizing signal without the horizontal synchronizing signal for convenience of explanation.

When the magnetic head scans the trajectory Y shown in FIG. . It is a combination of the outputs from and B. When this trajectory Y is scanned, noise occurs at a portion N as shown in FIG. However, when the scanning locus of the magnetic head coincides with the locus X shown in FIG. 4a, the reproduction envelope becomes XE in the same figure, and the FM demodulated video signal becomes as shown in FIG. At this time, the noise N is located near the vertical blanking period of the video signal, and the playback screen becomes noiseless still playback with horizontal striped noise bars pushed up and down the screen. However, since the vertical synchronization signal is affected by the noise N that is driven into the vicinity of the vertical blanking period, the pseudo vertical synchronization signal that is generated with a certain period of delay from the rising phase of the pulse S is It is necessary to stabilize vertical synchronization by adding it within the vertical blanking period of the signal.

Next, the operation when transitioning from normal playback to noiseless still playback will be described. First, the set speed of the capstan servo circuit is set to a much lower speed than during recording, and the magnetic tape is run at a low speed. In this way, the blowing head no longer correctly scans the video track, and the scanning center of the magnetic head gradually shifts over the video track. FIG. 5 is a diagram showing a portion of a video track, showing the rising phase S of the pulse S shown in FIG. 3 with respect to the position of the scanning center line of the magnetic head. and vertical synchronization signal V. It shows the time of phase difference between In the figure, the scanning center line of the magnetic head is the video track T. The leftmost line C
0°, the rising phase of the pulse S is at point 5 (corresponding to 11) on the line G, which is a certain distance from the bottom edge A of the tape.
The rising phase S of the pulse S at this time. , to the vertical synchronization signal V. The phase difference time until then appears as tl. Similarly, the scanning center line of the magnetic head corresponds to the video track T.

When the pulse S coincides with the rightmost line Cat, the rising phase of the pulse S corresponds to the point S0° on the line G, and the vertical synchronizing signal V. The time of phase difference between the two appears as tl. The magnetic head is a video track T. When scanning the entire center line C8, the time of the phase difference between the rising phase So of the pulse S and the vertical synchronizing signal Vo appears as (tI+I'/2).

FIG. 6 shows the video track 'I+B shown in FIG. 4 α,
, A shows how the magnetic head scans in the vicinity of the vertical synchronizing signal from α toward C with slight deviations in the figure. ! Fig. 7 shows the reproduction envelope when the magnetic head 21 scans the magnetic tape while gradually moving to the right.

Rising phase S of pulse S. and vertical synchronization signal V. This figure shows how the phase difference between the two changes over time. 6th
In the figure, of the two magnetic heads, magnetic head 21
Let's consider only the case where it is played. That is,
The magnetic head 21 has the same azimuth angle as the video track 'I e '1, so the video signal and vertical synchronization signal of the video track B1 are not reproduced. At α in the figure, the magnetic head 21 is scanning approximately half of the video track A1, and the rising phase of the pulse S corresponds to the point So between the scanning center line C and the line G, and the vertical synchronization at this time is Signal V. The time of the phase difference between the two is C3 shown in FIG. When the magnetic head 21 scans a video track having the same azimuth angle while moving gradually to the right as time passes, the rising multiphase So of the pulse S and the vertical synchronization signal V.

The phase difference with respect to the current value gradually increases as shown in FIG. 7bK.

The scanning center of the magnetic head 210 has shifted further to the right.

When the magnetic head 2 reaches the position of the scanning center line C in the figure,
1 is scanning to the right end of the video track A, and is the rising and falling phase S of the pulse S at this time. The time of the phase difference between the vertical synchronization signal Vo and the vertical synchronization signal Vo becomes the maximum value t2.

Next, when the scanning center of the magnetic head is further shifted to the right, the scanning center line C comes to the position shown in FIG.

Here, the vertical synchronization signal V to be reproduced next by the magnetic head 21
o is not of the video track BS having a different azimuth angle, but of the video track A having the same azimuth angle. At this time, the magnetic head 21 is moving to the video track A!
The left end of the pulse S is scanned and the rising υ phase S of the pulse S is detected. The time of the phase difference between the signal and the vertical synchronization signal has a minimum value t1. In this way, when the scanning center line C of the magnetic head 210 moves from FIG.
As shown in FIG. 7, the time of the phase difference with o changes sharply from the maximum value t to the minimum value t1.

Next, the waveform of the reproduction envelope in Fig. 7 α is as follows.

The waveform becomes a waveform in which the maximum level M and the minimum level N are repeated alternately. Also, the rising phase S of the pulse S. and vertical synchronization signal V
The phase difference with o becomes a sawtooth waveform as shown in Figure 6, and the amplitude of the reproduction envelope shown in Figure 6 is at the minimum level N.
Only when , it changes sharply at 1, -10.

When this phase difference changes sharply, in FIG. 6, the magnetic head I is scanning the video track At'ft along the scanning center line C shown in FIG. The trajectory coincides with the scanning trajectory X shown in FIG. 4a. Therefore, the FM of the reproduction output from the magnetic head
The demodulated video signal becomes as shown in FIG. 4e, and as described above, on the playback screen, noiseless still playback is performed in which the noise bar is pushed into the vertical blanking period of the playback video signal. That is, the rising multiphase 5° of the pulse S and the vertical synchronization signal V. Noiseless still playback can be achieved by detecting the point in time when the phase difference between the tape and the tape changes sharply and stopping the tape running. Note that frame forwarding can be done by running the magnetic tape again at low speed and repeating the above operation.

Based on the above operating principle, an embodiment of the magnetic tape stoppage control device of the present invention is shown in FIG. 8, and a waveform diagram of each part thereof is shown in FIG. 9. A part of the stoppage control device shown in FIG.
Since it can be used in common with a part of the servo control device at the time of recording the figure, the same number is given to the common part. Since the functions and operations of the common parts are exactly the same as those described in FIG. 1, detailed explanation thereof will be omitted.

In FIG. 8, reference numeral 45 denotes a reference signal generating circuit which generates a reference signal having a frequency equal to the frame frequency of the video signal. The pulse S from the pulse forming circuit 32 is phase-compared with the reference signal from the reference signal generation circuit 46 in the phase comparison circuit 42, and a phase error signal corresponding to the phase difference between the two is outputted from the phase comparison circuit 42. This phase error signal is sent to the disk motor 4 via the disk servo circuit 41.
As a result, the pulse S is servo-controlled to be phase-synchronized with the reference signal, and therefore the magnetic head 2
1.22 is rotated at a rotation speed equal to almost the same frame frequency as during recording. The video signals that are reproduced from the magnetic tape 1 field by field by the magnetic heads 21 and 22 whose rotation is controlled in this way are transmitted to the video signal reproducing circuit 62, where they are reproduced field by field by the pulse S from the pulse forming circuit 32. Switched between one continuous iG
After being subjected to appropriate signal processing, the reproduced video signal is output to the output terminal 20.

On the other hand, this reproduced video signal is supplied to a vertical synchronizing signal separation circuit 70, and this circuit 70 separates the vertical synchronizing signal VS. This vertical synchronizing signal VS is supplied to a frequency down-down circuit 71. In the frequency down-conversion circuit 71, the pulse forming circuit 32
The pulse S from the field period vertical synchronizing signal VS is extracted from the field period vertical synchronizing signal VS during the period H11, and frequency-downgraded to the frame period vertical synchronizing signal VF. The vertical synchronization signal VF of this frame period is supplied to a phase comparator circuit 72, and this circuit 72 is also supplied with the pulse S from the pulse forming circuit 32, and a phase difference signal φ corresponding to the phase difference between the two is output. Ru.

During frame-advance still playback, a frame-advance control signal FA is applied to the input terminal 30 and input to the control circuit 80. After this frame advance control signal FA rises to H, it returns to L'' after a while. In the control circuit 80, the capstan motor control signal R becomes H'' in synchronization with the rise of the frame feed control signal FA as shown in FIG.
2, the rotational speed of the capstan motor 5 is set so that the running speed of the magnetic tape 1 is much lower than that during recording. At this time, as described above, the phase comparison circuit 7
The phase difference signal φ outputted from the circuit 2 has a sawtooth waveform as shown by φ in FIG. 8 as well as in FIG. As shown by VJ in FIG. 9, this pulse forming circuit 73 generates a pulse VJ only when the amplitude of the phase difference signal φ changes sharply.
occurs. This pulse Vl is supplied to the control circuit 8°. In the control circuit 80, upon arrival of the pulse VJ,
The capstan motor control signal R is set to L" to stop the capstan motor 5. Thus, the tape running is stopped at the time when the pulse r1 is generated, and at this time, the fourth
As described in Figure α, the magnetic heads 21 and 22 scan the trajectory x'l on the magnetic tape, and as a result, the position of the noise bar on the playback screen is forced into the vertical blanking period of the playback video signal. Therefore, stable noiseless still reproduction can be performed.

As described above, the embodiments shown in FIGS. 1 and 8 are cases in which the present invention is applied to a rotating two-head type magnetic recording/reproducing apparatus, but the present invention is not limited to this and can be applied to one head type or four-head type, for example. It can be applied to a magnetic recording/reproducing device having an arbitrary number of heads, such as a type, etc., and FIG. For example, even if a vertical synchronization signal with a field period is used, or instead of a vertical synchronization signal, a predetermined signal tone with a frame period or field period multiplexed and recorded in advance within the vertical blanking period of the video signal may be used. Any of these cases does not depart from the spirit of the present invention.

〔Effect of the invention〕

As described above, according to the present invention, when noiseless still playback is performed in a rotary head type magnetic recording/playback device, the generation position of the noise bar on the playback screen and the stop position of the magnetic tape are determined in the playback video signal. Since it is detected with high precision by phase comparison between the vertical synchronization signal and the rising phase of the head switching signal, the running of the magnetic tape can be stably controlled to stop. In other words, compared to the conventional method of detecting all dropouts of the playback video signal, it is possible to stably place all the noise bar occurrence positions on the playback screen within the vertical blanking period of the playback video signal, making the playback screen easier to see. It can bring benefits such as becoming.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a servo control device for recording video signals in the magnetic recording/reproducing apparatus of the present invention, FIG. 2 is a waveform diagram of each part thereof, and FIG. 3 is a diagram of a video track pattern. Figures 4, 5, 6,
FIG. 7 is a diagram showing the operating principle of the present invention, FIG. 8 is a block diagram showing an embodiment of a stop control device for performing frame advance noiseless still playback according to the present invention, and FIG. 9 is a waveform diagram of each part thereof. . 1...Magnetic tape 21.22...Magnetic head 52
... Speed setting circuit 70 ... Vertical synchronization signal separation circuit 71 ... Frequency step-down circuit 72 ... Phase comparison circuit 7
3... Pulse forming circuit 80... Control circuit patent attorney Takahashi aAro≦'. Kun 2 Figure 3

Claims (1)

[Claims] 1. A first signal synchronized with the rotation of the rotary magnetic head is recorded on a magnetic tape by a rotating magnetic head, and a magnetic recording/reproducing apparatus for reproducing the first signal is used to record the first signal on the magnetic tape during reproduction. a separation circuit that separates the first signal reproduced by the rotating magnetic head; and a pulse generator that generates a pulse signal synchronized with the rotation of the rotating magnetic head. a phase comparison circuit that compares the phases of the signal from the first self-separation circuit and the pulse signal from the previous μ pulse generator and outputs a signal of the phase difference; A magnetic recording and reproducing device comprising: a pulse forming circuit that detects a steep amplitude change in a signal and forms a pulse; and a control circuit that controls the running of the magnetic tape to stop based on the pulse signal from the pulse forming circuit. 2. The magnetic recording and reproducing apparatus according to claim 1, wherein a vertical synchronization signal of a recorded video signal is used as the first signal.