KR920001127B1 - Recording mode switching method - Google Patents

Abstract

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Description

Record Mode Discrimination Switching Method

1 is a diagram schematically showing a tape pattern in a tracking method using four types of pilot signals.

2 is a block diagram showing a tracking method using four types of pilot signals.

3 is a diagram showing the scanning trajectory of the rotating head when the tape pattern recorded in the SP mode is reproduced by the LP mode.

4 is a diagram showing the scanning shown in FIG. 3 by another display method.

5 is a diagram showing the scanning trajectory of the rotating head when the tape pattern recorded with the LP mode is reproduced with the SP mode.

FIG. 6 is a diagram showing the scanning shown in FIG. 5 by another display method. FIG.

7 is a block diagram showing an embodiment of a detection circuit for discriminating an SP mode and an LP mode according to the present invention.

8 shows the correlation between the pulse period of the f-V conversion circuit and the threshold value of the f-V conversion circuit output and the summit circuit.

9 is an operational waveform diagram of the embodiment.

* Explanation of symbols for the main parts of the drawings

16: tuning circuit 17: detection rectification circuit

18: pulse shaping circuit 19: f-V conversion circuit

20: Summit circuit

The present invention relates to a magnetic recording and reproducing apparatus (hereinafter referred to as VTR) for sequentially recording and reproducing a signal as a discontinuous recording trajectory inclined on a magnetic tape by using a rotating head. It is about a method.

In the helical scanning system VTR, there is a VTR capable of recording by changing the recording time while switching the tape speed at the time of recording to one VTR.

In such a VTR, it is desirable to automatically determine the recording mode at the time of reproduction, and to reproduce the recording mode at the same speed as the recording speed at the time of normal reproduction. Conventionally, as a method of realizing this, it is recorded on a control track near the tape end. The method of discriminating whether the period of the control pulse which exists is shifted from the normal period was employ | adopted. However, as a new abbreviated VTR, a system that tracks based on a signal reproduced by a rotating video head itself, and a conventional automatic discriminating means in a system that does not use a conventional tape length control track. Will not be available.

The present invention provides a method for automatically determining and switching a recording mode even for a tracking method that does not use a control signal.

According to the present invention, a pilot signal having four different frequencies is repeatedly recorded one by one in a superimposed manner on a television signal, and a cross of a pilot signal reproduced from a recording track adjacent to the recording track to be reproduced at the time of reproduction is reproduced. A tracking method for controlling a relative position between a recording track and a reproduction scan trajectory of a reproduction magnetic head by using a tracking error signal in accordance with a level difference of a torque signal, wherein the reproduced pilot signal is divided into four different pilot signal frequencies. It consists of a detection circuit which detects a change in the period of the pulse signal after detecting and detecting a pulse after intervening a tuning circuit to tune to any one of them, and the difference between the tape speed at the time of recording and the tape speed at the time of reproduction. To automatically switch to the playback mode under the same conditions as when recording.

Before describing an embodiment of the present invention, a four-frequency pilot signal tracking method using four types of pilot signals that do not use a general control signal will be described.

FIG. 1 is a recorder and a trajectory by the four-frequency pilot signal tracking method, and FIG. 2 is a block diagram of a reproduction circuit for obtaining a tracking error signal.

In Fig. 1, A ₁ , B ₁ , A ₂ , B ₂ ,... Are each recording tracks recorded on the magnetic tape with A heads and B heads having different predetermined azimuth angles.

The arrow 1 indicates the scanning direction of the rotating head. In each recording track, the pilot signal indicated by f ₁ to f ₄ together with the video signal is repeatedly recorded one by one in sequence. The order in which the pilot signals are recorded is shown in Fig. 1, and one type of pilot signal is continuously recorded in one-feed period. The frequency of the pilot signal is set to the value shown in Table 1, for example.

TABLE 1

Incidentally, in Table 1, f _H indicates the frequency of the horizontal synchronization signal, and 6.5f _H indicates that the frequency is 6.5 times the frequency of the horizontal synchronization signal.

The frequency difference of the pilot signal between the recording tracks is a frequency of f _H or 3f _H as shown in FIG. When the head scans the Ai (i = 1, 2, ...) track, the frequency difference between the pilot signal of the scanning track and the pilot signal recorded on the right adjacent track on the ground is always f _H , It is always 3f _{H on the} left. When the head scans the B ₁ track, the opposite is true, whereby the frequency difference of the pilot signal between the scan track and the adjacent track on the right is always 3f _H , which is always f _{H on the} left.

Since the pilot signal is a relatively low frequency signal near 100 KHZ, the pilot signal recorded in the adjacent track can be reproduced as a crosstalk signal without the head scanning the adjacent track.

For example, a pilot signal obtained when the head scans along an A ₂ track (on track) is a composite signal of f ₃ , f ₂ , and f ₄ , with the level f ₃ being the largest, followed by f ₂ , f ₄ Play the same level.

The level of the reproduction pilot signal obtained when the head reproduces and scans slightly from the track A ₂ toward the track B ₂ decreases in the order of f ₃ , f ₄ , and f ₂ . On the contrary, the level of the pilot signal obtained when the head is shifted toward the track B ₁ and scanned is decreased in the order of f ₃ , f ₂ , and f ₄ . Therefore, when the difference frequency signals f _H and 3f _H between the pilot signal on the main scan track and each pilot signal recorded on both adjacent tracks are separated out, and the reproduction levels of both signals are compared, the head from the main scan track is compared. The shift amount and the shift direction can be known.

2 is a block diagram of a reproduction circuit for obtaining a signal in tracking. In FIG. 2, a reproduction RF signal obtained by combining a video signal and a pilot signal is input from the terminal 2. The circuit 3 is a low pass filter and separates only the pilot signal from the reproduced RF signal. The pilot signal obtained at this time is a composite signal of the pilot signals recorded on both adjacent tracks of the main scan track.

The circuit 4 is a balanced modulation circuit, and multiplies the synthesized signal by the reference signal supplied from the terminal 5. The reference signal supplied from the terminal 5 is a pilot signal of the same frequency as the pilot signal recorded on the scan track. For example, in FIG. 1, when the head reproduces and scans the track A ₂ , the input signals of the balanced modulator circuit 4 are f ₂ , f ₃ , f ₄ . Therefore, the balanced modulation circuit 4 outputs a signal of the sum and difference of frequencies between the signals of f ₂ , f ₃ , f _{4 and} the signals of f ₄ .

The circuit 6 is a tuning amplifier circuit that tunes to the signal of f _H , and the circuit 7 is a tuning amplifier circuit of 3f _H. Circuits 8 and 9 are detection rectifier circuits, and circuit 10 is a level comparison circuit.

Therefore, each pilot signal taken out from both adjacent tracks as a crosstalk signal is taken out separately as a difference signal from the pilot signal recorded on the main scan track, and then the signal according to the level difference is taken out from the level comparison circuit 10. do. In the signal obtained by the level comparison channel 10, when the regeneration level of f _H is greater than the regeneration level of 3f _H , a positive voltage is taken out according to the level difference, and in the opposite case, a negative potential Is pulled out. In addition, since the signal obtained by the level comparison channel 10 includes information of the track shift amount and the shift direction of the head, it can be used as a breaking error signal. In practice, however, suitable tracking error signals require further processing.

This is because, as apparent from FIG. 1, in the A track and the B track, the relationship between the head shifting direction and the crosstalk signal f _H or 3f _H obtained at that time becomes opposite to each other.

In FIG. 2, the circuit 11 is an analog inversion circuit, and the circuit 12 is an electronic switch switched in accordance with the period of the head switching signal supplied from the terminal 13. Therefore, the output signal of the level comparator 10 is output to the terminal 14 when the head A is reproduced and scanned, for example, and the level comparator 10 is output when the head is regenerated and scanned. The output signal is output inverted analogly. For this reason, the signal obtained at the terminal 14 always outputs a positive potential when the head shifts to the right from the track to be scanned regardless of the A and B tracks, and always a negative potential when shifted to the left.

Therefore, if the signal obtained at the terminal 14 is supplied as a tracking error signal and the tape speed is controlled, the head always scans (on track) along the main scanning track.

The above is an outline of how to obtain a tracking error signal using four types of pilot signals.

The present invention is, for example, in the configuration of the tracking method as shown in FIG. 1, in which the recording mode is automatically detected at the time of reproduction when recorded at least two or more different speeds.

Here, a description will be given of having two types of recording modes (SP → 1 hour recording, LP → 2 hours recording, for example).

First, the case where the tape recorded with the SP mode is reproduced with the LP mode will be described.

The trajectory of the rotary head when the tape recorded with the SP mode is reproduced with the LP mode is displayed as shown in FIG.

If the scan shown in Fig. 3 is another display method, it is as shown in Fig. 4, and the recording pattern is 1 → 2 → 3 → 4 → 5 → 6 → 7 → 8 → 9 → 10. → in the order of injection.

Now, focusing on one pilot signal among four types of recorded pilot signals (here, f ₁ ). As shown in Fig. 4, the scanning of the f ₁ recording track is the ninth scanning after the first.

In other words, scanning is performed every 8 days (4 frames).

Next, the case where the tape recorded with the LP mode is reproduced with the SP mode will be described. When the recording pattern recorded by the LP mode is reproduced by the SP mode, the trajectory of the rotating head is displayed as shown in FIG.

If the scan shown in Fig. 5 is another display method, it is as shown in Fig. 6, and the recording pattern is 1 → 2 → 3 → 4 → 5 → 67 → 8. It is injected in the order of.

Now, focusing on f ₁ of the four types of recording pilot signals, as shown in Fig. 6, the scanning of the f ₁ recording track is the third after the first. That is, scanning is performed every two days (one frame).

Note that normal playback (when SP mode playback with SP mode recording, LP mode playback with LP mode recording) does not require scanning the f ₁ recording track every four frames (two frames).

The present invention discriminates the recording mode from the above relations, and one embodiment of a detection circuit for discriminating the recording mode according to the present invention is shown and described in FIG.

First, the configuration will be described. The reproduction pilot signal is input to the tuning circuit 16 through which the output signal is obtained by tuning to only one type of frequency among the four types of pilot signals via the terminal 15, and outputting the tuning circuit. Is inputted to the detection rectification circuit 17 for processing, and then pulsed by the pulse shaping circuit 18. The pulse output obtained from the pulse shaping circuit 18 is input to the fV converter circuit 19, and the output of the fV converter circuit 19 is shown in FIG. 8 according to the pulse output cycle of the pulse shaping circuit 18. FIG. As is converted to voltage.

과

주기의 펄스를 f-V 변환환전압(E₁)과 (E₂)의 사이에 설정한 스레쇼울드치전압(E_A)(낮은 쪽의 스레쇼울드치전압)과

과

주기의 펄스를 f-V 변환한 전압(E₂)과 (E₃)의 사이에 설정한 스레쇼울드치전압(E_B)(높은쪽의 스레쇼울드치전압)으로 설정된 시미트회로(20)에 입력되며, 이 시미트회로(20)를 스레쇼율드치전압(E_A) 이하가 되면 출력이 Hi 전압이 되고, 스레쇼울드치전압(E_A)과 스레쇼울드치전압(E_B)과의 사이면 시미트회로 출력의 상태를 유지하고, 스레쇼울드치전압(E_B) 이상으로 되면 출력이 Low 전압이 되도록 구성해 두고, 시미트회로 출력단자(21)로부터, 기록모우드를 판별하는 검출신호를 얻는다.The output of the fV conversion circuit 19 is fed by this fV conversion circuit 19.

and

Threshold value voltage (E _A ) (lower threshold value voltage) between the period pulse set between fV conversion ring voltage (E ₁ ) and (E ₂ )

and

To the summit circuit 20 set to the threshold value voltage E _B (higher threshold value voltage) set between the voltage E ₂ and E _{3 obtained} by fV conversion of the period pulse. When the summit circuit 20 falls below the threshold rate voltage E _A , the output becomes a Hi voltage, and the threshold value voltage E _A and the threshold value voltage E _{B are} reduced. It is configured to maintain the state of the inter-side shim circuit output, and to make the output low when the threshold value voltage (E _B ) or more is detected, and to detect the recording mode from the shim circuit output terminal 21. Get signal.

Next, the operation principle based on the structure of FIG. 7 is demonstrated. When the magnetic tape recorded with the SP mode is reproduced with the LP mode at the time of reproduction, as described above, for example, scanning a track recorded with f ₁ is every eight feeds (four frames).

의 주기가 펄스화된 펄스출력(다)을 얻을 수 있다.

의 주기의 펄스출력(다)을 f-V 변환회로(19)에 입력하면 제8도를 사용해서 설명한 바와같이, f-V 변환회로 출력전압은 E₃가 되기 때문에, 시미트회로(20)의 스레쇼울드치전압(E_B)보다 높게 되어, 시미트 회로 출력전압은, Low 전압이 된다.Therefore, since the tuning circuit 16 is configured to tune only to f ₁ , the tuning circuit output (A) is output as shown in FIG. 9, and the tuning circuit output (A) is detected and rectified circuit (17). From the output by inputting the detected rectifier circuit output (b) input to the pulse shaping circuit 18,

It is possible to obtain a pulse output (C) in which the period of is pulsed.

When the pulse output (C) of the period of is inputted to the fV converter circuit 19, the output voltage of the fV converter circuit becomes E ₃ as described with reference to FIG. It becomes higher than the tooth voltage E _B , and the summit circuit output voltage becomes a low voltage.

Therefore, if the switching voltage of the SP mode at the time of recording is selected as the low voltage, the regeneration state is switched to the normal regeneration (SP regeneration of the SP recording mode) state.

Now, when switching to normal playback, scanning a track having f ₁ as described above is every four feeds (two frames).

의 주기의 펄스출력(다)을 얻는다.

의 주기의 펄스출력(다)을 f-V 변환회로(19)에 입력하면 f-V 변환회로 출력전압은 E₂가 되지만, 이때는 시미트회로 출력은 반전되지 않고 Low 전압 상태는 그대로 유지되어 안정된 상태로 들어가서 정상 재생을 계속한다.Therefore, as shown in FIG. 9, from the pulse shaping circuit 18,

Get the pulse output (C) of the period of.

When the pulse output (C) of the period of is input to the fV converter circuit 19, the output voltage of the fV converter circuit becomes E ₂ , but at this time, the summit circuit output is not reversed and the low voltage state is maintained as it is. Continue playing.

Next, when the magnetic tape recorded with the LP mode is reproduced with the SP mode during reproduction, scanning the track having recorded f ₁ as described above is every two feeds (one frame).

의 주기의 펄스화된 펄스출력(다)을 얻을 수 있다.

의 주기의 펄스출력(다)을 f-V 변환회로(19)에 입력하면 제8도를 사용해서 설명한 바와같이 f-V 변환회로 출력전압은 E₁보다 낮아지며, 시미트회로 출력전압은 Hi 전압이 된다.Therefore, as shown in FIG. 9, from the output of the pulse shaping circuit 18,

The pulsed pulse output (C) of the period of can be obtained.

When the pulse output C of the period of is input to the fV converter circuit 19, the output voltage of the fV converter circuit is lower than E ₁ as described with reference to Fig. 8, and the summit circuit output voltage becomes the Hi voltage.

Therefore, if the switching voltage of the LP mode at the time of recording is selected as the Hi voltage, the reproduction state is switched to the normal reproduction (LP recording mode to LP reproduction) state.

의 주기의 펄스출력(다)을 얻는다.

의 주기의 펄스출력(다)을 f-V 변환회로(19)에 입력하면 f-V 변환회로 출력전압은 E₂가 되며, 이 때는 시미트회로 출력은 반전하지 않고 Low 전압상태는 그대로 유지되어 안정된 상태로 들어가서 정상재생을 계속한다.Now, as described above, when switching to normal regeneration, from the pulse shaping circuit 18

Get the pulse output (C) of the period of.

When the pulse output (C) of the period of is input to the fV converter circuit 19, the output voltage of the fV converter circuit becomes E ₂ , at which time the output of the summit circuit is not reversed and the low voltage state is maintained as it is. Continue normal playback.

The above is the operation principle of the detection circuit for discriminating the write mode of the present invention.

According to the present invention, unlike the conventional method of tracking using a control track, the mode at the time of recording can be accurately determined by a simple configuration and a sequence of detecting a predetermined pilot signal and detecting the period change. Based on the discrimination, it can automatically switch to the same tape speed as when recording. Therefore, operation by a human hand for mode switching is unnecessary, and an operation error can be prevented in advance.

Claims (1)

When recording, superimposed signals of four different frequencies are superimposed on a television signal to be recorded sequentially one by one, and sequentially recorded as recording tracks on magnetic tape by a rotating magnetic head, and reproduced during playback. Magnetic recording and reproducing apparatus for controlling the relative position between the recording track and the reproducing scan trajectory of the reproducing magnetic head by using a tracking error signal corresponding to the level difference of the crosstalk signal of the pilot signal reproduced from the recording tracks adjacent to the recording track before and after the recording track. In the reproducing, any one of the pilot signals of the pilot signals having the four different frequencies is taken out during playback, and the period of the extracted signals is detected to determine and switch between the tape speed at the time of recording and the tape speed at the time of playback. Record Mode Discrimination Switching Method.

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