JPS60154305A - Magnetic video recording and reproducing device - Google Patents

Abstract

PURPOSE:To prevent generation of duplicated recording at the time of consecutive recording by recording a pilot signal having the 3rd or the 4th frequency difference to a track next to the video track at the end of recording and switching the mode to the recording mode when the signal is detected at the reproduction mode. CONSTITUTION:A pilot signal generator 1 generates circulatingly a pilot signal fm(m=1-4) at recording. The fm is superimposed on a video signal VD at an adder 12, fed to a head 16A or 16B via a recording amplifier 13, a recording/ reproducing changeover switch 14 and a head changeover switch 15 and recorded on a video tape 17. A reproducing signal is separated from the VD by a BPF21 at reproduction and the fm and the f2 are mixed at a mixer 22 and a mixed pilot signal fmm' is outputted. The fmm, is inputted to BPFs 30, 31 and a signal of the 3rd and 4th frequency difference gamma and delta is extracted and a deviation signal is fed to a switch circuit 36 via a hold circuit 35 from a differential amplifier 34 through detection circuits 32, 34 and the switch 14 is changed over to the recording position. Thus, duplicate recording is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a magnetic recording and reproducing apparatus such as a VTR that performs tracking control using a four-frequency Baytron 1 system.

In general, magnetic recording and reproducing devices with rotating magnetic heads such as VTRs are not capable of so-called splice editing, or are not able to perform AI [taking pictures] by performing Bose operations, etc. ing.

However, with a simple pause operation, the next recording will start regardless of the track that has already been recorded, so the arrangement of the tracks may become discontinuous or the control signal may become discontinuous. This causes a problem in that the tracking servo is lost in this part during playback, causing image distortion.

Therefore, in conventional magnetic recording and reproducing devices, the video tape is rewound while counting the control pulses already recorded on the video track from the last video track on which signal recording has already been completed, and when the counted value reaches a predetermined value. Stop the videotape once at , then run the videotape in the normal running direction and set it to playback mode 1-, perform tracking during this playback mode, and record the count value of control 1-roll pulse or the above count value. Some devices are designed to switch from playback mode to recording mode when a match occurs.

However, in such a magnetic recording/playback device, recording cannot be started from several video tracks before the final video track due to the sensitivity of the control amplifier and the accuracy of the video tape drive system. It didn't happen.

As a result, a double-recorded portion occurs where a new signal is recorded on a video track on which a signal has already been recorded, and during playback, beat noise occurs in this double-recorded portion, resulting in deterioration of image quality.

-Objective-- This invention has been made in view of the above points, and is particularly designed to prevent double recording from occurring during splicing in a magnetic recording/playback device that uses the 4-frequency pilot method for tracking. , the purpose is to prevent deterioration of image quality.

Composition---Construction.

Therefore, the magnetic recording and reproducing apparatus according to the present invention records a pilot signal having a third or fourth frequency difference with respect to the pilot signal at the end of recording on the next video track of the first hidden rack at the end of recording. Then, when a third or fourth frequency difference signal is detected in the playback mode for continuous shooting, the playback mode is switched to the recording mode.

Embodiments of the present invention will now be described with reference to the accompanying drawings.

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

First, the pilot signal generator 1 includes an oscillator 2 that generates a signal of a predetermined frequency, and a signal from the oscillator 2 that is sequentially divided into a predetermined frequency division ratio, for example, 115, according to an external control signal.
8.1150.1/36; An automatic frequency control oscillator consisting of frequency divider 3, etc., which divides the frequency by 1/40 and outputs it in a circular order, and can control the output and output stop by an external control signal. It is composed.

That is, this pilot signal generator 1 first generates a predetermined first signal. Second. Third. Fourth frequency difference α, β, γ
, δ, four types of picots 1-signal fm (fl
+f2+f3+f4).

That is, between the frequencies of these pilot signals f1 to f4, l fl - f21 = I f3 - f4 l = αlf2
There is the following relationship: f31=lf4 fl l=β+f3-fll=γ l 14-121=δ.

For example, the pilot signals f1 to f4 are each f,=lO
OKHz, f2=115KHz, f3=160K
Hz, f4 = 1.45 KHz, the first to fourth frequency differences α, β, γ, and δ are each a
= 15 K4(' z,, β=45KHz, y=6
0KHz + δ = 30KHz.

The pilot signal generator 1 is controlled by a head switching pulse (switching pulse) and a pulse obtained by dividing this switching pulse by 172 to generate these pilot signals f1 to f4.

It is output in the circular order of "1 → "2° → f3 → f4 → f.

On the other hand, the recording end switch 5 is turned on when recording ends, for example, when a pause button or stop button is operated.

The recording end detection circuit 6 switches the pilot rotation of the pilot signal generator 1 when the recording end switch 5 is turned on, and transfers the pilot signal fm output from the pilot signal generator 1 to the current pylon 1. A pilot signal having a third frequency difference γ or a fourth frequency difference δ with respect to the signal, for example, a positive switching instruction signal SA that instructs the next output of the pilot signal f1 to be the pilot signal f3, is sent to the ant circuit. 7 to the pylon 1 to the signal generator 1.

That is, the recording end switch 6 and the recording end detection circuit 7 constitute a recording order changing means.

In addition, in this magnetic recording/playback apparatus, when the switching instruction signal SC is output from the recording end detection circuit 6, the recording is possible by one video track more than in the process at the end of recording in the conventional magnetic recording/playback apparatus. This is what I want to do.

The edge detection circuit 8 outputs a positive detection signal SB to the circuit 7 when detecting a rising edge (or a falling edge) of the switching pulse (head switching pulse) SWP.

The hold circuit 9 issues a switching instruction (d
Video head or feel 1 from the time the issue SA was input
(When the time required for tracing has elapsed, an output stop instruction signal SC is output to pylon 1 to signal generator 1 to instruct them to stop outputting the pilot signal fm.

Then, pylon l from generator 1 to pylon 1
- the signal fm is passed through the adder 1 through the low-pass filter 11;
2, and also to a mixer 22, which will be described later.

The adder 12 superimposes the pilot signal fm on the video signal (chroma signal and luminance signal).

It is output to the recording amplifier 13 as a recording signal VA.

The recording amplifier 13 amplifies the recording signal VA from the adder 12 and supplies it to the video head 16A or 16B selected by the head changeover switch 15 via contacts a and c of the record/playback changeover switch 14. .

Note that the recording/playback selector switch 44 has contact a during recording.
The head selector switch 15 is switched to the contact a side or the contact side by the switching pulse SW I].

Hitohets F16A and 16B are rotating magnetic heads that record the output signal from the M'Qfa amplifier 13 on the video tape 17, and also read and output the signals recorded on the video tape 17.

The playback amplifier 20 inputs and amplifies the pickup signals from the video heads 16A and 16B via the switch 15 and the contact cbrfil of the record/playback switch 14, and outputs a playback signal V11. In addition to outputting to the demodulator of the reproduction system, the
Output to.

The pan 1 to pass filter 21 pass only the signal (re/l-pilot signal) fm' (m=1 to 4) to the pylon 1 out of the reproduction signal VB from the reproduction amplifier 20.

The iQ mold 22 mixes the regenerated pilot signal fm' that has passed through the bus filter 21 to the pan 1 with the pilot signal fm that is input from the pilot signal generator 1 via the low-pass filter 11, and generates the first to fourth signals. Frequency difference α, β
, γ, δ signals f m m
' Outputs '.

The pan 1-bass filter 23 filters the first frequency difference α of the mixed pilot signal −j3fm m′ from the mixer 22.
, and the pan 1 bass filter 24 also receives the second signal.
The signal with the frequency difference β is passed.

The detection circuits 25 and 26 detect the levels of the signal with the first frequency difference α and the signal with the second frequency difference β, respectively, and output them to the differential amplifier 27.

The differential amplifier 27 outputs a signal with a first frequency difference α and a second frequency difference α.
A deviation (1 (No. S1)) corresponding to the level difference of the signal of 1'1 wave discontinuity difference β is output to the I-racking surf system.

On the other hand, the band pass filter 30 receives the third frequency difference γ of the mixed pilot signal from' from the mixer 22, and the band pass filter 30 receives the fourth frequency difference δ of the mixed pilot signal from the mixer 22. Pass the signal.

The detection circuits 32 and 33 detect the levels of the signal with the third frequency difference γ and the signal with the fourth frequency difference δ, respectively, and output them to the differential amplifier 4.

The differential amplifier 34 outputs a deviation signal SE to the hold circuit 35 according to the level difference between the signal with the third frequency difference γ and the signal with the fourth frequency difference δ.

The hold circuit 35 receives the deviation signal s from the differential amplifier 34.
Hold E.

These bandpass filters 30, 31 . Detection circuit! +
2.33. The differential amplifier 64 and the halt circuit 35 constitute recording end position detection means.

The switching circuit '56 is a mode switching means, and when the halt circuit 35 holds the deviation signal SE during playback for continuous shooting, that is, the signal with the third frequency difference γ and the signal with the fourth frequency difference δ When there is a level difference between
At a predetermined timing, the recording/reproduction changeover switch 14 is switched from the contact a side to the contact side.

Next, the operation of this embodiment configured as described above will be explained with reference to FIG. 2 as well. In FIG. 2, arrow A indicates the running direction of the video tape 17, and arrow B indicates the rotating direction of the video heads 16Al to 16B.

First, the control operation of the four-frequency pilot type tracking will be explained.

First, during recording, the recording/reproduction changeover switch 14 is switched to the contact a side.

At this time, the pilot signal generator 1 is controlled by a switching pulse and a pulse obtained by dividing the frequency of this switching pulse by 1/2, and changes the pilot signal fm to f, → f2 → f
Output in the cyclic order of 3→f4→fl.

This pilot signal fm is converted into a video signal V by an adder 12.
I) and is superimposed on the recording amplifier 13. The signal is supplied to the video head 16A or 16B via the recording/playback switch 14 and the head switch 15, and is recorded on the video tape 17.

In other words, when recording, for example, 1-
Pilot signal f1 to rank T1, pilot signal f2 to track T2, track T31: /<d°'
/ I"(j8f a &, h 5') ') T
4 V) <do! The pilot signal f4 is recorded on the track T5, the pilot signal f1 is recorded on the track T5, and so on, the pilot signal fI-f4 is recorded together with the video signal VD in a circular order.

Next, during reproduction, the recording/reproduction changeover switch 14 is switched to the contact side.

Then, from the video tape 17, the video head 16Al
The reproduced pilot signal fm' contained in the reproduced signal vn which is alternately picked up by the reproducing amplifier 20 and amplified by the reproducing amplifier 20 is separated from the video signal VD by the band pass filter 21 and input to the mixer 22. .

At this time, the reproduced pilot signal fm' includes the pilot signal recorded on the track to be traced by the video heads F16A and IEiB, as well as the pylon signal recorded on the track adjacent to that track.・Includes signals.

.

For example, when racing from track T2 shown in FIG. A signal f3 is included.

On the other hand, during playback, from the pilot signal generator 1 to the video head IE)A, IEl[l or the regular 1 to be traced.
~Rack pilot signal fm is input to mixer 22.

For example, when tracing the track T2 shown in FIG. 2, the signal f2 is sent from the pilot signal generator 1 to the pylon 1.
or input to the mixer 22.

Once, the mixer 22 outputs a signal with a first frequency difference α, which is a heat signal due to crosstalk between the pilot signal of the regular truck and the pilot signal of the adjacent truck, and a signal with a second frequency difference β. A mixed pilot signal fmm' containing the signal fmm' is output.

For example, when tracing the track T2 shown in FIG. 2, a signal with a first frequency difference α having a frequency of lf+ −f21 and a signal with a second frequency difference β having a frequency of lf2 f3 t are as follows.
The video head IEIA or 16B is output at a level that corresponds to the level of the video head T2.

These signals with the first frequency difference α and the signal No. 6j with the second frequency difference β are separated by bandpass filters 23 and 24, their levels are detected by detection circuits 25 and 26, and the differential signal is It is input to the amplifier 27.

At this time, if the video head IE+A, 16]1 is accurately racing the regular track 1 to 1, the signals m of the first frequency difference α and the signal of the second frequency difference β will be at the same level, but the normal If either of the two adjacent 1-rank tracks in the trunk of the trunk is near the desired track,
Depending on the amount of deviation, one of the signals of the first frequency difference α and No. 48 of the second frequency difference β becomes thicker (and the level of the other becomes smaller).

For example, when tracing track T2 shown in FIG. 2, if it deviates toward track T1, the level of the signal with the first frequency difference α increases, whereas the level of the signal with the second frequency difference β increases. When the second frequency difference β becomes smaller and the signal moves toward the track T3, the level of the signal of the second frequency difference β becomes larger, whereas the level of the signal of the first frequency α becomes smaller.

Then, from the differential amplifier 27, the first frequency difference α
A deviation signal SD corresponding to the difference between the signal level of the second frequency difference β and the signal level of the second frequency difference β is output.

Therefore, by applying the 1 to racking servo so that the level of the signal of the first frequency difference α and the signal a of the second frequency difference β are the same, a regular track can be accurately traced.

Note that during this normal reproduction, the mixed pilot signal fmm' from the mixer 22 is used as the third. Fourth frequency difference γ, δ
Since this signal is not included, the differential amplifier 34 does not output the deviation signal SE.

Next, I will explain how to use the continuous shooting method.

First, during recording, the track TI-T shown in Figure 2
Assuming that recording has been completed up to n-2 and the recording end switch 5 is turned on while recording to track T n -+,
As a result, the recording end detection circuit 6 outputs a positive switching instruction signal SA.

At this time, although originally the recording system would have ended the processing at the end of this track Tn-1, this magnetic recording/reproducing apparatus continues processing for an additional 9 minutes of l-tran.

Therefore, for example, if the switch pulse SWP rises to trace the track Tn, the edge detection circuit 8 detects the rising edge and outputs a positive detection signal SB, so the AND circuit 7 opens. become a state.

As a result, the switching instruction signal SA from the recording end detection circuit 6 is output to the frequency divider 6 of the pilot signal generator 1 via the ant circuit 7, and is also output to the hold circuit.

Thereby, the pylon 1-signal generator 1 transfers the signal 1 to the pylon 1 having a relationship of a third or fourth frequency difference γ or δ with respect to the pilot signal recorded on the track at the end of recording (the last track). outputs the next pilot signal fm of pilot No. 43 which is originally recorded in the 1-rack next to the 1-rack at the end of recording.

In other words, for example, as shown in FIG. 2, when the pilot signal f3 is recorded on the recording end track Tn-+, the next pilot signal f4 that is originally recorded on the next track -Tn of racks 1 to Tn-+ is Outputs pilot signal fl.

Therefore, a pilot signal having a third or fourth frequency difference γ or δ with respect to the pilot signal at the end of recording is recorded on the track next to the track at the end of recording.

In other words, for example, as shown in FIG.
1 is recorded.

This JL can be generally described as shown in the following table, assuming that the order of the signals (Byron) and signals is changed at a constant value, that is, that the pilot signal next to the original pilot signal is recorded.

Then, corresponding to the point in time when recording for the next 1 to racks of this recording end track is completed, the hold circuit outputs an output stop signal SC to stop the output of the pilot signal fm from the pilot signal generator 1. let

In this way, for example, as shown in FIG. 2, the pilot signal f1° [2r f
] A4+fl...L +f2, f3, f'l
The counterfeit recording ends when it is recorded together with the video signal VD.

Next, when performing continuous shooting, the videotape is rewound by a predetermined amount, that is, by an amount necessary for tracking during playback.

At this time, for example, if the tape has been rewound to the trunk T1 shown in Figure 2, it will enter playback mode 1- in this state and run the videotape from rack T in the playback direction (direction of arrow A). , as mentioned above, apply one Hertzkink search based on the deviation signal SD from the differential amplifier 27,
The video head 168 controls the rotational speed of a capstan motor (not shown).

1611 and the playback 1-rack position (take tracking).

After that, if we trace the video head 16Δ or, for example, 1 to rack TT n-1 in which the pilot signal f3 shown in FIG. However, a pilot signal f1 is also recorded on track Tn.

Therefore, at this time, the mixing pylon 1 to fmm' outputted from the mixer 22 includes a signal with the first frequency difference γ of fizf+l as well as a signal with the first frequency difference 1f3−f21. It is.

Then, the signal of the third frequency difference γ is extracted from this mixed picograph 1 signal fmm' by the band pass filter 30, its level is detected by the detection circuit 32, and is input to the differential amplifier 34.

At this time, the fourth
Since the signal with the frequency difference δ is not included, the differential amplifier '54 outputs the deviation -68r=, which is halted by the halt circuit 35. ::Thereby, the switching circuit 36 switches the recording/reproduction changeover switch 14 from the contact side (reproduction side) to the contact a side (recording side) at the time when tracing of the trunk Tn-1 is completed.

Then, the recording mode is entered and recording is started from track Tn, and at this time, the pilot signal f4 is recorded anew on tracks T and n.

Note that, for example, a pilot signal f is added to the track at the end of recording.
4 is recorded, and the pilot signal f2 is recorded on the next track.
is recorded, the mixed pilot signal fmm
' contains the signal of the fourth frequency difference δ of If4 f2 l.

Therefore, at this time, m of this fourth frequency difference δ
The signal is extracted by the band pass filter 31 and sent to the detection circuit 3.
3, and since the mixed pilot signal fmm' does not include the signal of the third frequency difference γ, the difference signal SE is output from the differential amplifier 34 as well.

As a result, at this time as well, the switching circuit 36 allows recording/recording.
The playback changeover switch 14 is switched to switch from the playback mode to the recording mode.

In this way, in this magnetic recording/playback device.

A pilot signal having a third or fourth frequency difference with respect to the pilot signal recorded in 1st to 3rd at the end of recording is recorded on the track next to the track at the end of recording, and when in playback mode for splicing. When the third or fourth frequency difference signal is detected, the reproduction mode is switched to the recording mode.

This will ensure that the next one of the tracks at the end of the
Recording can be performed from the rack, eliminating the risk of double recording of image signals, and resulting in poor image quality due to the occurrence of beats. There are no two.

By the way, as a method for recording continuous shots by switching the circulation order of the pilot signals and detecting the resulting change in the level of the two frequency difference signals, for example, can be considered as follows.

That is, the same pilot signal as the pilot signal recorded on the recording end track is recorded on the next track after the recording end track.

For example, if the pilot signal f2 is recorded on the recording end track, the pilot signal f2 will also be recorded on the next track.
Record.

By doing this, when the recording end track is traced, if tracking is achieved, in the above example, I
Since only the signal with the first frequency difference α of f+f21 is output, and the signal with the second frequency difference β is not output, the deviation signal reaches the maximum level even though tracking is achieved.

Therefore, if the reproduction mode is switched to the recording mode when this deviation signal reaches the maximum level, recording can be started from the track following the recording end track, and double recording will not occur.

In this way, the band pass filter, detection circuit, and differential amplifier for tracking servo can be shared, so the configuration becomes simple.

However, even if continuous shooting is performed in this manner, if the tracking servo is not completely locked when the recording end track is traced, there is a possibility that the joint cannot be detected.

Furthermore, when the mechanical system vibrates during splicing, or when the tape is scratched, the output of the differential amplifier fluctuates, and there is a risk that a part other than a gap will be detected as a seam.

On the other hand, according to the present invention, the first. Since the joint is detected by detecting the third or fourth frequency difference signal that is different from the second frequency difference signal, the joint is accurately detected even if a situation where tracking is not completely achieved occurs. can.

In addition, in the above embodiment, an example was described in which the third frequency difference and the fourth frequency difference were separate.

It can also be implemented when tracking is controlled using a four-frequency pilot method in which the third frequency difference and the fourth frequency difference are the same.

As explained above, according to the present invention, deterioration in image quality due to continuous shooting does not occur in a magnetic recording/reproducing device.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a main part showing an embodiment of the present invention, and FIG. 2 is an explanatory diagram showing a pattern on a videotape to explain the operation of FIG. 1. 1...Pilot signal generator 5...Record end switch 6...Record end detection circuit 12...Adder 14...Record/playback switch 15/Head selector switch 16A+1613/Hikoohetsu 1-

Claims (1)

[Claims] Fourteen consecutive video tracks, each with a predetermined first. Second. Four types of pilot signals having third and fourth frequency difference relationships are recorded in a circular order, and a mixed pilot signal obtained by mixing the reproduced pilot signal and the pilot signal of the bidet first rack to be traced is used. 1st. Detecting the second frequency difference signal, performing tracking control based on the detection result, and rewinding the video tape at a predetermined time from the video l-rack where recording has been completed;
In a magnetic recording/playback device that performs tracking and continuous shooting in a playback mode, the video track next to the video track at the end of recording is set to the third or fourth frequency with respect to the pilot signal at the end of recording. recording order switching means for recording pilot signals having a difference; recording end position detecting means for detecting a signal of the third or fourth frequency difference from a signal to the mixing pylon 1 in a reproduction mode; A magnetic recording and reproducing apparatus comprising: mode switching means for switching from the reproduction mode to the recording mode when the position detection means detects the third or fourth frequency difference signal.