JPH0770102B2 - Recording tape speed discriminating device - Google Patents

Description

Detailed Description of the Invention (a) Field of Industrial Application The present invention is a standard in 8 mm VTR, so-called
The present invention relates to a recording tape speed discriminating device during high-speed reproduction in a VTR that uses the ATF tracking system.

(B) Conventional technology In the 8 mm video, instead of forming a control track like a general VTR, a tracking pilot signal is superimposed on the video track, and the beat component with the injection pilot signal is extracted at the time of reproduction to determine the level difference. According to this, tracking is possible.

On the other hand, the 8 mm video has a standard recording mode and a double long-time recording mode, and it is necessary to determine the recording mode during reproduction. There are also normal playback mode and so-called picture search high-speed playback mode in forward and reverse directions, and the recording mode can be discriminated regardless of the tape speed during playback. Is desirable.

In Japanese Patent Laid-Open No. 61-1179, a tracking error signal is derived while switching the frequency of the injection pilot signal at the field cycle, the tracking error signal is divided according to the tape speed, and then the divided output cycle is obtained. Is shown to identify the recording mode.

By the way, in the direction of creating the tracking error signal in the high-speed reproduction mode, as described above, the frequency of the injection pilot signal is switched to ₁ , ₄ , ₃ , ₂ in the field cycle, and the method of switching all the tracks traced by the video head. There is a method of creating a tracking error signal by sequentially switching the injection pilot signals corresponding to the pilot signals. The latter method is described in, for example, JP-A-59-1919.
It is disclosed in Japanese Patent Publication No. 79. It is generally said that the latter method is superior in terms of servo stability.

However, when the latter method is used, the circuit disclosed in the above-mentioned Japanese Patent Laid-Open No. 61-1179 cannot be adopted as the recording mode discrimination device.

(C) Problems to be Solved by the Invention The present invention is a recording tape speed discriminating device in a VTR (video tape recorder) that creates a tracking error signal by switching the frequency of the injection pilot signal during one field during high speed reproduction. Is to provide.

(D) Means for solving the problem While running the tape at a high speed, the frequency of the injection pilot signal is switched a predetermined number of times during one field period to generate a tracking error (ATF error) signal.
In a video tape recorder in which the frequency of the injected pilot signal during the field period is changed at least at one place to create the phase lock signal, the level of the phase lock signal fluctuates randomly in order to discriminate the recording mode during high speed reproduction. It is a recording tape speed discriminating apparatus which detects the above and reverses the discrimination of the recording tape speed.

(E) Action Detects random fluctuations in the level of the phase lock signal,
By reversing the determination of the recording tape speed, the recording tape speed can be determined even by the method of switching the frequency of the injection pilot signal a predetermined number of times during one field period.

(F) Embodiments Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram, FIG. 2 is a flow chart showing the operation of the microcomputer, and FIGS. 3, 4, and 5 are explanatory diagrams.

In FIG. 1, (1) is an input terminal for a reproduction pilot signal, (2) is an input terminal for an RF switching pulse related to the head rotation phase, (3) is an input terminal for a signal designating high speed reproduction, (4) ) Is the output terminal of the ATF error signal, (5)
Is an output terminal for discriminating output of the recording tape speed.

(6) is a mixing circuit, (7) is an injection pilot signal generation circuit, (8) is a timing control circuit for controlling this injection pilot signal generation circuit (7), etc. (9) is a band pass of 47 KHz (delayed beat) Filter (BPF), (10) is the first
(11) is a bandpass filter (BPF) of 16 KHz (leading beat), and (12) is a second detection circuit.

(13) is a differential amplifier that receives the outputs of the first and second detection circuits (10) and (12), (14) is a first sample and hold circuit, and (15) is a second sample and hold circuit. The timing control circuit (8) controls the sample and hold circuits (14) and (15).

(16) is a first comparator that receives the output of the second sample and hold circuit (15), and (17) is a low-pass filter (LP).
F) and (18) are second comparators, and (19) is a microcomputer that outputs a recording tape speed discrimination output.

The first comparator (16) outputs a signal from the second sample and hold circuit (15) (changes between 0 and 5V) at a certain level (2.
When it is higher than 5V, L level is output, and when it is lower, H level is output. Conversely, the second comparator (18) outputs an H level when it is higher than a certain level (Vcc / 2),
When it is low, it is set to output the L level.
The broken line (20) indicates the IC (C × 22022).

The operation during high speed reproduction will be described with reference to FIG. 3 (9 × speed, forward feed). FIG. 3A shows how the video head traces the recorded track in the normal case by the track pattern coordinate method. And indicate the pilot signals ₁ , ₂ , ₃ , ₄ .
(B) shows the RF switching pulse, and (C) shows the reproduction output envelope and the reproduction pilot signal.
(D) shows the injection pilot signal, and (e) shows the output of the differential amplifier (13).

When the speed of high-speed reproduction is determined, it is possible to know how to trace the track, and thus how to change the frequency of the injection pilot signal is determined. When the 9-speed reproduction is basically dividing one field into nine, _one at the time of the resulting pilot signal _{1 (= 102.5KHz), 2 (} = 119.0KHz) 4 when the ₍₌
The _{148.7KHz), 3} at the time of 3 (= 165.2KHz),
When the value is ₄ , ₁ is supplied. actually,
_The output may be in the order of ₁ , ₄ , ₃ , and ₂ .

Then, in order to determine whether or not the phase is locked, a phase lock signal is further created. In other words, when the phase is locked during high-speed playback and the noise bar is fixed, the frequency of the partial injection pilot signal is adjusted from the above regulation so that the ATF error signal of either H or L level is always obtained. Make it come off. That is, in a certain section (A), if an injection pilot signal of a frequency corresponding to the preceding or succeeding track is inserted in the center (A) 'of the section, when the phase is locked correctly, L A level or H level pilot signal is obtained. In other words, it means that one track is ahead or behind.

In the embodiment, the injection pilot signal of the frequency corresponding to the next track is inserted in the center (A) 'of the section (A) in the center of the screen. Therefore, if the phase is properly locked in the center of this section, an H level output (output of the differential amplifier (13)) is always obtained. When the phase is not locked and a noise bar appears, the level of this phase locked signal fluctuates randomly. When the phase lock is lost, the tape recorded in the standard recording (SP) mode is used for 9x high-speed reproduction in the long-time recording (LP) mode (4.5x speed reproduction) or (see Fig. 5). , When the tape recorded in LP mode is played at 9x speed in SP mode (18x speed playback) (see Fig. 4), the tape is played in a mode different from the tape speed at the time of recording. It also includes the state of being.

The ATF error signal is obtained as the output of the first sample hold circuit (14). The phase lock signal is the output of the second sample hold circuit (15). Controlling the creation of the injection pilot signal and the first and second sample and hold circuits (1
4) The sample / hold control of (15) is performed by the timing control circuit (8) according to the timing shown in FIG. At the time of high speed reproduction, the 9x speed designation signal is applied, and the timing control circuit (8) turns on the RF switching pulse (b).
In synchronism with, the control is performed so that the frequency of the injection pilot signal changes as shown in (d).

The second sample hold circuit (15) samples the output (e) of the differential amplifier (13) at a predetermined timing in the section (A) ', and is controlled to hold the value during the other periods. The first sample and hold circuit (14) is controlled so as to sample and hold the value immediately before the section (A) ', and removes the interference of the phase lock signal with respect to the ATF error signal.

The first comparator (16) which receives the output of the second sample and hold circuit (15) inverts the output as described above, so that the phase is locked, and when the correct tape speed is determined, the output of the L level is output. But the terminals of the IC (20) (21)
Can be obtained. On the contrary, when the phase is not locked, a random output is obtained at the terminal (21). The phase lock signal of this terminal (21) is applied to the low pass filter (17), and the smoothed output is compared with 1/2 (2.5V) of the power supply voltage by the second comparator (18).

That is, when the phase is not locked, the terminal (21)
Since the output of is a random state of H level and L level,
There is some level of output at the LPF (17). Then, the occurrence of this output is detected by the second comparator (18), that is, the output of the second comparator (18) becomes H level when a random output is obtained.

The output of the first sample hold circuit (14) is applied to the capstan servo circuit via an appropriate low pass filter.

As described above, the microcomputer (19) determines the final recording tape speed and outputs the SP / LP determination output. The operation is the rise of the RF switching pulse,
It is performed by interrupt processing based on the detection of the falling edge.

That is, when the edge of the RF switching pulse is detected, a discrimination routine for high speed reproduction is entered to check whether the terminal (22) of the microcomputer (19) is at H level. If it is not at H level, the counter R1 is reset and the process returns to the main routine. If H level is detected, set the value of counter R1 to 1
Then, it is checked whether the value of the counter R1 is larger than 60.

The high speed reproduction is executed by operating the fast forward and rewind buttons in the normal reproduction state. So the counter R1
During normal playback, it is always reset.
Also, the tape speed for high-speed playback corresponds to the determination result for the previous normal playback (and when the tape recording speed of the tape has changed during the high-speed playback, the determination in the high-speed playback mode is Required).

If it is smaller than 60, the state where the phase lock is out is within 1 second, so the process directly returns to the main routine. If it is larger than 60, the judgment of the recording tape speed at that time is reversed. (If in SP mode, go to LP mode, if in LP mode, go to SP mode). When the mode is reversed, the counter R1 is reset. Then return to the main routine.

In other words, the micro computer (19) considers the tape speed to be incorrect if the phase lock state continues for more than a certain period of time. This predetermined time must be longer than the time required until the phase is locked after the high speed reproduction state is designated.

The output of the terminal (21) of the IC (20) may be directly input to the microcomputer (19) to determine that the output changes in a random state. For example, the following method can be considered. That is, in the predetermined field period (X),
The number of fields (Y) at which the output of the terminal (21) becomes H is measured, and when this (Y) becomes larger than (X / 4), the reproduction mode is reversed. Is the way.

FIG. 6 is a flow chart showing this operation. The predetermined field period (X) is set to 60. The interrupt operation of the RF edge increases the value of the register X (indicating the number of RF edges) by "1" (61), and checks whether the ATF lock signal is at "H" level (62). "H"
If it is a level, the value of the register Y (indicating the number of times the H level of the ATF lock signal is increased) is increased by "1" (63).
After that and when the ATF lock signal is not at "H" level, it is checked whether the value of the register X is "60" (64). If it is "60", the value of the register X is set to "0" (65), otherwise. Return to the original processing (69).

After setting the register X to "0", it is checked whether the value of the register Y is "15" or more (66). If it is not "15" or more, the process returns to the original process (69). If the value of the register Y is "15" or more, it is considered that the reproduction mode is wrong, so the SP mode is inverted to the LP mode and the LP mode is inverted to the SP mode (67). And the value of register Y is "0"
After that (68), the original processing is returned to.

In this case, the contents of the registers X and Y must be "0" before entering the high speed reproduction mode. In a VTR configured so that the high speed reproduction mode can be set only from the normal reproduction mode, the values of the registers X and Y may be set to "0" in the normal reproduction mode.

Although the comparison value of the value of the register Y is set to 1/4 or more of X in the above example, this is determined by the S / N of the ATF error signal in the VTR to which the present invention is applied. It is a thing. That is, even if high-speed reproduction is performed in the correct mode (SP or LP), if the S / N is bad, the ATF lock signal may be at the "H" level. Therefore, it is desirable to set the comparison value to a value that does not cause the discrimination through experiments.

On the contrary, the function of this microcomputer can be realized by hardware (counter or the like).

(G) Effect of the Invention As described above, according to the present invention, in high speed reproduction,
In a VTR that performs phase servo control by using an injection pilot signal with a frequency corresponding to all tracks traced within the field period, it is effective because the recording tape speed can be discriminated even during high speed reproduction with a simple configuration.

[Brief description of drawings]

FIG. 1 is a block diagram of the embodiment, FIG. 2 is a flow chart showing the operation, and FIGS. 3, 4 and 5 are explanatory diagrams.
Further, FIG. 6 shows a flow chart in another embodiment. (15) …… Second sample and hold circuit, (16) …… First
Comparator, (17) ... Low-pass filter, (18) ...
… Second comparator, (19) Microcomputer

Claims (1)

[Claims] 1. A tape is run at a high speed, and the frequency of the injection pilot signal is switched a predetermined number of times during one field period to generate an ATF error signal, and the frequency of the injection pilot signal at at least one position during the one field period. In the recording tape speed discriminating device of the video tape recorder, in which the frequency is set to a frequency different from the frequency corresponding to the track to be scanned, a detecting means for detecting a random change of the phase lock signal, A discriminating result reversing unit for reversing the discriminating result of the recording tape velocity according to the detection result of the detecting unit.