JPH0720226B2 - Mode change method of 4-frequency pilot type video tape player - Google Patents

Description

The present invention relates to a mode changing method for a 4-frequency pilot type video tape player. Specifically, it relates to an improvement of a mode changing method from a review mode (reverse rotation high speed reproduction mode) at the time of reproduction of an 8 mm VTR to a normal reproduction mode (normal reproduction mode).

(B) Conventional technology The VTR playback mode includes normal playback in which the tape is transferred at the same direction and speed as during recording, reverse playback at the same speed and reverse direction, and high speed (for example, 7 times the normal speed, 9 times the normal speed).
There is a high-speed playback in the forward and reverse directions that drives the tape at twice.

And when changing modes between these modes,
The tracking of the rotary head is disturbed and noise is generated on the screen. Also, when changing the mode in which the tape running direction is reversed, the mechanism system must be switched.

Therefore, in Japanese Patent Laid-Open No. 60-20346 (G11B 15/02), a stop playback state (still mode) is provided between the modes when the playback direction is switched, and the mechanism system is switched during this still mode. In addition to improving the tape feeding accuracy.

However, in a mode change that requires deceleration of tape running, such as a change from the -4 × speed review mode to the normal play mode, the change in speed is large. There is a problem that it is not possible to prevent the generation of noise bars on the screen.

Therefore, in Japanese Patent Laid-Open No. 62-198283 (H04N 5/783), when the review mode is changed to the normal reproduction mode, not only the still mode but also the reverse reproduction mode (reverse 1
Double speed playback mode).

Then, during this reverse playback, tracking control is performed to match the tape running and the tracking of the rotary head, and the tracking deviation due to the rapid deceleration of the tape from the review mode to the reverse playback mode is corrected and a noise bar is displayed on the screen. To prevent it.

The relationship between the tape running amount and time at this time is shown in FIG. point
AB indicates the review mode, point BC indicates the reverse reproduction mode, point CD indicates the still mode in which a predetermined track (for example, f ₁ track) is scanned, and point DE indicates the normal reproduction mode. Shows. Then, in the reverse reproduction mode between the points BC, the tracking is adjusted.

(C) Problems to be solved by the invention However, in the above-mentioned conventional example, the time (T ₁ ) in the reverse reproduction mode must be set to a time sufficient for completing the tracking adjustment.

It is sufficient if the movement to the reverse playback mode (capstan braking) can be performed according to the theory, but in the actual 8 mm VTR, naturally, it may be performed according to the above theory in some cases, or there may be an error.

That is, it is considered that the tape running at the beginning of the reverse reproduction mode includes both a phase error (tracking error) and a speed error. Then, it operates to eliminate this error in the VTR servo circuit.

This operation will be conceptually described with reference to FIG. In FIG. 3, (t) is a time axis,
(T _B ) is the time point when the mode is changed to the reverse reproduction mode from the review mode. The vertical axis represents the tracking deviation and corresponds to the ATF tracking error signal described later. In other words, if this mode change is properly performed, tracking is quickly adjusted by the servo operation as shown in FIG. ₁₁ and the tracking deviation is eliminated. However, if the tracking is greatly deviated as shown in Fig. 3 l ₂ ,
Due to the servo operation, the phase fluctuates before the tracking is completed. This swing is called "phase flow". Actually, it is also affected by the speed error. In the case of a speed error, the speed also fluctuates due to the servo operation. When the speed fluctuates, a phase fluctuation naturally occurs.

When such a swing occurs, it takes about 2 seconds until the tracking is completed (the servo operation is stabilized).

In other words, the period (T ₁ ) in FIG. 4 must be set to about 2 seconds.

This phase flow is good when the distinction detection of the front track and the back track for tracking peculiar to the 8 mm VTR (specific to the four-frequency pilot system video tape player) is performed.
A little improved.

The present invention provides a mode changing method in which the reverse reproduction mode is quickly changed to the still mode and a noise bar is not displayed on the screen.

A. Here, the detection of the front and back tracks will be described. The detection of the following front and back tracks is 8mmV
This is a well-known and commonly used technique in TR.

B. First, the tracking method of the 8 mm VTR will be explained.

The 8mm VTR tracking method is based on the Japan Broadcast Publishing Association, Showa
130 pages of "NHK Home Video Technology" edited by Japan Broadcasting Corporation published on April 20, 1955, and pages 157 to 159 of "Latest AV Equipment and Digital Technology" published by Corona on December 10, 1986. Since the basic principle is described in, etc., it will be briefly described here.

FIG. 5 shows the track of the tape. f ₁ ~f ₄ shows four pilot signal superimposed recorded in each track.

FIG. 6 shows a known ATF tracking error signal generation circuit (1
2) is shown. (20) is a reproduction signal input terminal. (22) is a low-pass filter that extracts pilot signals (f ₁ ) to (f ₄ ). (24) is a terminal to which the reference signals (f ₄ ) to (f ₁ ) are input, and (26) is a mixing circuit. (28) is a bandpass filter for extracting the advancing beat component (16 kHz), and (30) is the adjoining delay beat component 47.
It is a bandpass filter that extracts kHz. (32) (3
4) is a detection circuit, and (36) is a differential amplifier circuit. (38)
Is a sample hold circuit for ATF tracking error, which holds a value at a predetermined timing in one field and outputs an ATF tracking error signal. (40)
Is a sample and hold circuit for front and back track detection,
The value is held at a predetermined timing in one field and a front / back track detection signal is output. (42) and (44) are control signals (TSA) (T
SB) Input terminal. When the terminals (42) (44) are at a high level, the sample hold circuits (38) (40) are in a hold state, and when they are at a low level, they are conducting.

FIG. 7 shows the principle of the relationship between the pilot signal and the reference signal during normal reproduction. Further, FIG. 8a shows the relationship between the amount of track deviation and the level of the ATF tracking error signal.

As can be seen from FIG. 8A, when the tracking is deviated by two tracks, the relationship between the level of the ATF tracking error signal and the deviation direction is reversed, and tracking is not performed only with the ATF tracking error signal.

The normal case as shown in FIG. 8A is called the front track, and the opposite case is called the back track. In order to always perform good tracking, the back track is detected, and the timing of the reference signal frequency is advanced by two fields during the back track to switch to the front track state.

C. Fig. 9 shows a device for detecting this back track.
That is, in the actual 8 mm VTR, the reference signal switching timing is delayed by 2 msec from the change of the RF switching pulse indicating the head rotation phase. When the sample hold circuits (38) and (40) of the circuit of FIG. 6 are controlled as shown in (TSA) and (TSB) of FIG. 9, respectively, the sample hold circuit (38) is the same as that of FIG. Then, the ATF tracking error signal is outputted to the sample hold circuit (40) and the front and back track detection signal (see FIG. 8B) is outputted. The amplifier (46) in FIG. 6 outputs a high level back track detection signal (see FIG. 8 (c)). A servo circuit (not shown) advances the reference signal by two fields by the back track detection signal to prevent the malfunction of the tracking servo.

D. This back track detection is not limited to normal playback
It is also performed during reverse 1x speed reproduction (reverse reproduction). During reverse reproduction, the head locus becomes as shown in FIG. 10 and the reproduction pilot signal becomes as shown in FIG. 11 (b). Therefore, the reference signal is also changed from that during normal reproduction, as shown in FIG. 11 (c).

E. Next, the stop phase determination in the stop playback mode (still mode) will be described. It is desirable that the above-mentioned front track state is maintained when the still mode is changed to the normal reproduction mode. Therefore, in the still mode, it is determined in advance which track of the pilot signal the head is scanning, and the transition timing (or reference signal generation timing) to the normal reproduction mode is determined. This stop phase determination uses the back track detection signal. For example, in the case of a type in which the same track is scanned at the time of still operation with a normal 3-mm head 8 mm VTR, there is only one type of reproduction pilot signal. Therefore, the scanning track in the still mode is determined based on the phase relationship between the four types of reference signals and the back track detection signal.

F. For reference, Fig. 12 shows the head locus at the time of review. Also, FIG. 13 shows a waveform diagram at this time. Incidentally (TSA)
Is low level. At this time, the front and back tracks are not discriminated.

G. Since the above-mentioned back track detection is performed using part of the scanning period, quick detection cannot be performed with an actual 8 mm VTR. Therefore, when transitioning from the review mode to the normal reproduction mode, it takes a long time to detect the front and back tracks at the beginning of the reverse reproduction mode in the 8 mm VTR of the type through the reverse reproduction mode, and quick tracking operation is not performed.

(D) Means for Solving the Problems The present invention detects the level of the ATF tracking error signal in the reverse reproduction mode during the transition from the review mode to the normal reproduction mode, regardless of the back track front track. The on-track state is detected, and the mode is shifted to the still mode by this detection. At the same time, the stop phase is determined in the still mode to smoothly shift to the normal reproduction mode.

(E) Action Since the present invention has the above-described configuration, the ATF tracking error signal level is detected and the on-track state is detected even when the tracking of the tape and the head is being pulled in during the transition from the review mode to the reverse playback mode. If it is determined that the mode is changed to the still mode immediately, the time for changing the mode can be shortened.

(F) Embodiment An embodiment of the present invention will be described with reference to FIGS. 1 and 2.

(Mc) in FIG. 1 is a capstan motor. (10) is a capstan motor control circuit, which is composed of a microcomputer. (12) is the ATF tracking error signal generation circuit of FIG. (10a) is an A / D conversion terminal for inputting an ATF tracking error signal, which A / D converts the ATF tracking error signal and processes it by the microcomputer (10). (14) is a hysteresis circuit that shapes the ATF tracking error signal, and (10b) is a high and low signal input terminal. In FIG. 1, other capstan control circuits (conventional control circuits for PF switching pulse signals, FG signals, PG signals, etc.) are omitted.

FIG. 2 shows the relationship between the tape running amount and time at this time.
FIG. 14 shows the operation of the microcomputer (10) at this time.

When the user presses the play playback button during review playback (AB), the VTR is
The tape is braked in synchronism with the F switching pulse and the reverse playback mode (BC) is set quickly. When this reverse playback mode is set, the ATF shown in FIG.
If the tracking error signal is in the range of ± 0.5V, it is almost on-track. Here, the microcomputer (1
0) indicates that if the ATF tracking error signal input from the A / D input terminal (10a) is in the range of ± 0.5V, it synchronizes with the RF switching pulse so that the head traces the track of a predetermined azimuth during still operation. Turn on the capstan brake and stop the tape. The VTR is in still mode. At this time, since the head is stopped regardless of the front and back tracks, the scanning tracks at this time are tracks with the same azimuth (for example, the pilot signal is f ₁ or
f ₃ ) One track. For example, a stopped truck
If it is f ₁ or f ₃ is, AT when the reference signal is f ₂
The stopped track is determined by whether the F tracking error signal (input signal of terminal 10b) is high (f ₃ o'clock) or low (f ₁ o'clock).

Incidentally, as shown from the review mode in FIG. 3 l ₂ when changing to the reverse reproduction mode, the same applies to the case where "phase flow" occurs. The microcomputer (10) monitors the ATF tracking error signal and is ± 0.5 V during “phase flow” (during fluctuation).
It is detected that it is within the range of (the on-track state during the change). And within this range and RF
Predetermined timing synchronized with switching pulse (timing when head goes on track in still mode)
Then, the capstan motor (MC) is stopped to enter the still mode, and the stopped track is determined in the same manner as described above.

In this way, since the stop track is discriminated, the microcomputer determines the timing of transition from the still mode to the normal reproduction mode according to this track, and at this determined timing, the capstan ( MC) to start.

There is a period (about 1/6 second) in which the tape speed decelerates from -7x speed to -1x speed when the review mode is switched to the reverse reproduction mode. Of course, the microcomputer (10) detects the level of the ATF tracking error signal after finishing this deceleration period.

In the above embodiment, the determination of the stop track is made by the tracking error signal. However, separately from this, as in the conventional case, the stop phase is determined and the tape start timing is set as described in the section E. Then, the normal playback mode may be entered.

(G) Effect of the Invention As described above, according to the present invention, even if a phase flow occurs at the time of shifting from the review mode to the reverse reproduction mode, the on-track in the middle of this phase flow is detected to shift to the still mode. Therefore, the change to the still mode can be performed quickly and the mode can be changed quickly.

[Brief description of drawings]

1 and 2 are views for explaining an embodiment of the present invention. FIG. 3 is a diagram for explaining the phase flow, FIG. 4 is a diagram showing tape feeding, FIG. 5 is a diagram showing tape, and FIG. 6 is ATF.
FIG. 7 is a diagram showing a tracking error signal generating circuit, FIG. 7 is a diagram for explaining the operation in the normal reproduction mode, FIG. 8 is a diagram for explaining the operation of FIG. 6, and FIG. 9 is an actual normal reproduction. FIG. 10 is a diagram showing the waveform of each part in the mode, FIGS. 10 and 11 are diagrams for explaining the rebus reproduction mode, and FIG.
FIG. 13 and FIG. 13 are diagrams for explaining the review mode. FIG. 14 is a diagram for explaining the operation of FIG.

Claims (1)

[Claims] 1. A method of changing the mode of a 4-frequency pilot type video tape player via a reverse 1 × speed reproduction mode and a stop reproduction mode when changing from a high speed reverse reproduction mode to a normal reproduction mode, wherein the reverse 1 × speed reproduction is performed. In the mode, by detecting that the magnitude of the ATF tracking error signal is below a predetermined level, the on-track state is detected regardless of the back track front track, and this detection shifts to the stop reproduction mode and the stop reproduction. A mode changing method for a 4-frequency pilot type video tape player, characterized in that after determining a stop track in the mode, the timing of shifting to the normal reproduction mode is determined according to the determination result.