JPS60123181A - Track jump detector for video tape recorder - Google Patents

Abstract

PURPOSE:To detect a track jump time point with simple constitution by supplying the output signal of a signal omission pulse producing circuit to an integration circuit and comparing the peak holding value with the integration value of the integration circuit. CONSTITUTION:When a dropout compensating pulse C is supplied to a dropout compensation terminal 5, an output signal D is obtained at the output side of a pulse stretcher 8 in accordance with the duration of time of the pulse C. This signal D is integrated by an integration circuit 9 to obtain a dropout compensating pulse 5a, i.e., an integration signal 9a having an extremely high level of its track jump part for output signals E and F. At the same time, the peak holding voltage 11a is obtained at the output side of a peak holding circuit 11. Therefore a track jump detecting signal corresponding to the signal 9a is obtained at an output terminal 12 of a comparator 10.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is suitable for use in a video tape recorder capable of playing back at tape speeds other than normal speed such as still mode and yoshi mode. Regarding equipment.

BACKGROUND ART AND PROBLEMS Generally, video tape recorders are designed to allow playback at tape speeds other than normal speed, such as still mode and high speed mode.

In this variable speed playback other than normal speed, one video head traces multiple video tracks, and in this case, the video head for one azimuth passes the video trunk recorded by the video head for another azimuth B. It is required to know the point in time (track jump point).

To detect a track jump, a dropout compensation pulse obtained at the output side of a dropout compensation pulse generation circuit of a dropout compensation circuit that compensates for a signal deletion section generally provided in a video signal reproduction system is used. It is possible that However, this dropout compensation pulse is designed to be used exclusively for trotubout compensation, and regardless of the cause of dropout, when the signal level of the reproduced high-frequency signal exceeds a certain level compared to the fd level at steady state, However, with this dropout compensation pulse as it is, it is not possible to distinguish between a dropout that occurs during a track jump and a dropout that occurs due to other causes.

OBJECTS OF THE INVENTION It is an object of the present invention to solve this problem and to make it possible to detect this track jump point with a simple configuration by using the trotubout compensation pulse.

Summary of the Invention The present invention provides a signal deletion pulse forming circuit that forms a pulse having a width corresponding to a period when the reproduction high frequency signal is at a predetermined level or below, and an integrating circuit that integrates the output signal of the signal deletion pulse forming circuit. , a peak hold circuit that peak-holds the output signal of this integrator circuit, and a comparison circuit that compares the output signal of this integrator with the output signal of this peak bold circuit, according to the present invention. The trunk jump point can be detected with a simple configuration.

Embodiment Hereinafter, an example in which an embodiment of the track jump detection device for a video tape recorder of the present invention is used for still playback will be described with reference to FIGS. 1 to 4.

First, as a video tape recorder, the first
A second video head (1b) having an azimuth B different from the so-called azimuth A in the gear direction of the first video head (Ia) is located at a position where the rotation angle phase is 180 degrees different from the video head (1a). First video head (1a
)- and a third video head (lc) with the same azimuth as the rotary head (11), and normally these first and second video heads (18) and (1b) are used for playback. It has been proposed to use (la) and (lc) for the first and third videos during still playback.In Figure 1, (2) is a magnetic tape. , this magnetic tape (2) is attached to a rotating head (1).
), and the magnetic tape (2) is provided with, for example, first and second video heads' (Ia) and (1b) as usual.
A diagonal video track is formed by alternating video heads with different azimuths. or(
3) works together with the pinch roller (4) to remove this magnetic tape (
2) Destroy the capstan that runs at a predetermined speed.

In a video tape recorder, during normal playback, video tape recorders F(la) and (1b) with different azimuths are used.
As shown in Fig. 2, video tracks (2A) and (
2B) are played sequentially.

In this case, when the still playback is displayed, the running of the magnetic tape (2) is stopped, so the 2nd drive (1a
) and (1b) are magnetic tape (
2) As soon as the same trajectory is drawn on the video head (1a) and (1b), when the switching signals of the video heads (1a) and (1b) are as shown in FIG. 3A, the reproduction signal level of the reproduction surface frequency signal is 3ml. As shown in 13, when the video head (1a) for azimuth is used, the amount is maximum, and when the video head (1b) for azimuth B is used, it is the minimum. In FIG. 2, video trunks (2Δ) and (2B) indicate video tracks recorded by video heads (1a) and (lb), respectively. When using this video head (1b), when the minimum point of the signal level of the reproduced high-frequency signal is fed very quickly to the stopped magnetic tape (2) so that it is at the center position of the switching signal, the video head (1a) and (1b) trace the video track of azimuth A shown by the broken line in Fig. 2. In this state, stop the magnetic tape (2) and change the video head (1b) to the video head (1c). If switched to azimuth, the video heads (1a) and (lc) for azimuth are used, and good still playback can be achieved.

In this example, the arrangement shown in FIG. 4 is used to find the minimum point of the signal level of the reproduced high-frequency signal when the video head (1b) is used.

In Figure 4, (5) indicates that the signal level of the high-frequency signal reproduced by the dropout compensation circuit provided in the video signal reproduction system of this video tape recorder is lower than the signal level at the specified time by more than a predetermined level. 3 shows a dropout compensation pulse input terminal to which a dropout compensation pulse that occurs during a period of time is supplied;

The dropout compensation pulse supplied to the dropout compensation pulse input terminal (5) is normally a pulse with a small pulse width that continues at equal intervals for a time period in which the pulse width remains below the predetermined level. This dropout compensation pulse is the third pulse when the reproduced high frequency signal is as shown in Figure 3B.
The result will be as shown in Figure C. In this Figure 3C, (
5B) is a dropout compensation pulse that occurs when the video head (lb) traces the video trunk (2^) of azimuth A with a different azimuth, that is, at the time of track jump, and the duration at this time is much longer than the other pulses.
5b) is a dropout compensation pulse caused by spacing loss near switching, and (5c) is a dropout compensation pulse caused by spacing loss, scratches on the magnetic tape, etc.

The levels of the dropout compensation pulses supplied to this dropout compensation pulse input terminal (5) are made equal (low level is, for example, OV, high level is, for example, power supply voltage Vc).
a reference signal input terminal (7) which is supplied to one input terminal of a comparator circuit (6) for the purpose of converting the reference signal to a reference signal (7) to which a reference signal for level shifting is supplied to the other input terminal of the comparator circuit (6)
In this case, a reference signal of more than 100% is supplied. This comparison circuit (6
) is a dropout compensation pulse with a uniform peak value as shown in FIG. 3C, which is obtained on the output side of Supply to stretcher (8).

On the output side of this pulse stretcher (8), a pulse having the width of the signal deletion period of the reproduced high-frequency signal is obtained as shown in the third diagram. The output signal of this pulse stretcher (8) is supplied to an integrating circuit (9). In this case, this integrating circuit (9
), an integral output signal as shown in Figure 3 is obtained, which is a continuation of the dropout compensation pulse (5a) that occurs when the video head (1b) traces the video track (2A) of azimuth A. This output signal Depending on the level, it is possible to clearly distinguish when this video head (1b) traces the video trunk (2A) of azimuth A. In this case, if there is no pulse stretcher (8), the integrating circuit (9) will directly integrate a unit pulse with a relatively small pulse width, and will be discharged before the next unit pulse comes, and this unit Even if the pulse continues, the output signal level of the integrating circuit (9) is almost irrelevant, and the duration of this unit pulse cannot be distinguished.

Further, the output signal of this integration circuit (9) is supplied to the non-inverting input terminal (■) of the operational amplifier circuit constituting the comparison circuit (101), and the output signal of this integration circuit (9) is supplied to the peak hold circuit (11). .This peak hold circuit (11
) is supplied to the inverting input terminal ○ of the comparator circuit (II).In this case, a predetermined discharge time constant is given to this peak hold circuit (11), and this peak hold circuit (II)
At this time, the peak value of the component signal (9a) corresponding to the dropout compensation pulse (5a) is enlarged in FIG. 98), this bold voltage (lla) is slightly lower than the peak value of the integral signal (9a) (
Let it be. In this comparator circuit (00), the output signal of the peak bold circuit v11 (11) is compared to the integration circuit (9
) only when the value of the output signal of the track jump detection signal output terminal (12) becomes large.
This was done as if to obtain ``.

In this example, since the configuration is as described above, when the reproduced high frequency signal is as shown in FIG. 3B, dropout compensation as shown in FIG. 3C is applied to the dropout compensation pulse input terminal (5). The pulse is supplied, and as a result, an output signal with a pulse width corresponding to the duration of the dropout compensation pulse as shown in the third diagram is obtained at the output side of the pulse stretcher (8), and this is outputted by the integrator circuit (9). is integrated,
On the output side of this integrating circuit (9), a dropout compensation pulse (58) as shown in FIG. ), a peak-hold voltage ratio (lla) similar to that shown in FIG.
A track jump detection signal (12a) corresponding to the integral signal (9a) is obtained as shown in FIG. In this example, the phase relationship between the track jump detection signal (12a) and the video head switching signal is shown in FIG. When the position corresponds to the middle position of the usage period of 1b), this state is maintained and the video head used is changed to the video head (1b).
By switching to the video head (1c) from b), still playback can be performed.

As mentioned above, according to this example, the pulse stretcher (8
), it is possible to obtain an integrated signal with an output level corresponding to the duration of the drop-out compensation pulse, and it is possible to detect the track jump point from this drop-out compensation pulse. In addition, the reference level in the comparison circuit GO+ is determined by the integration circuit (9
) is obtained through the peak hold circuit (11), the reference level can be eliminated without adjustment, which has the advantage of simplifying the configuration.

Next, an example in which this example is used for triple speed playback will be described with reference to FIGS. 5 and 6.

During triple-speed playback, the magnetic tape (2) runs in the direction of the arrow at three times the speed of normal playback, so the video heads (1a) and (1b) are moved, for example, as shown in FIG. Three video tracks (2B).

(28), (2B) and video track (2A),
(2B).

(2^) will be traced. If the signal level of the reproduced high-frequency signal of the video tape recorder at this time is as shown in FIG. 6B, the dropout compensation pulse as shown in FIG. 6C is transmitted to the dropout compensation pulse input terminal ( 5), and as a result, the output side of the integrating circuit (9) receives an integral signal (9) as shown in Figure 6.
a) is obtained, and at this time, the peak hold circuit (11)
On the output side of , there is a hold voltage (Ila) as shown in Figure 6.
) is obtained, and therefore, a trunk jump detection signal (12&) as shown in FIG. 6E is obtained at the track jump detection signal output terminal (12). In this triple speed playback, the trunk jump detection signal (12a) corresponds to the switching point of the switching signal of the video head (18) and (To) as shown in FIG. 6A, so that the switching signal and the track jump If the phase with the detection signal (12a) is adjusted, the center of the video screen corresponds to the maximum point of the reproduced video signal level, so a good 3x speed image can be obtained.

It goes without saying that the invention of the face tree is not limited to the above-mentioned embodiments, and that various other configurations can be taken without departing from the gist of the invention.

Effects of the Invention According to the present invention, there is an advantage that track jump points can be known with a simple configuration.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an example of a rotating head; FIGS. 2, 3, 5, and 6 are diagrams for explaining the present invention, respectively;
FIG. 4 is a block diagram showing a main part of an embodiment of a track jump detection device for a video tape recorder according to the present invention. (5) is a dropout compensation pulse input terminal, (8) is a pulse stretcher, +9) is an integrating circuit, OI is a comparison circuit, (11) is a peak hold circuit, and (12) is a trunk jump detection signal output terminal. Agent Sadado Ito Hidemori Matsukuma

Claims (1)

[Claims] A signal deletion pulse forming circuit that forms a pulse having a width corresponding to a period when the reproduction high frequency signal is below a predetermined level, an integrating circuit that integrates an output signal of the signal deletion pulse forming circuit, and an output of the integrating circuit. 1. A track jump detection device for a video tape recorder, comprising: a peak-bold circuit for peak-holding a signal; and a comparison circuit for comparing the output signal of the integrator with the output signal of the -F peak-hold circuit.