JPH011381A - video playback device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a video playback device.

[Conventional technology and its problems]

In a video playback device used in a VTR, two playback heads are arranged on a rotating drum, and a continuous playback video signal is obtained by alternately tracing recording tracks of a video tape. However, if foreign matter gets between the playback head and the video tape and sufficient playback output cannot be achieved, or if a good recording track cannot be formed during recording, the continuity of the playback video signal may be lost. It may happen. Conventional video playback devices have been unable to provide satisfactory playback images in such cases.

- In recent years, disk-shaped recording media (so-called optical disks, magneto-optical disks, compact disks, etc.) that can record continuous images over a sufficient length have become available.
Such sudden or instantaneous playback failures can occur not only in video tapes but also in disk-shaped recording media. However, even in video playback devices using disk-shaped recording media, no means have been taken to correct such playback defects.

To solve this problem, the same inventor as the present inventor proposed a configuration in which a normal reproduction signal is sequentially updated and stored in an image memory, and in the event of a reproduction failure, the signal from the image memory is substituted. However, in an ATF type 8 mm video apparatus that multiplexes and records a tracking pilot signal on a video signal, a pilot signal cannot be obtained during playback failure, which may cause a tracking malfunction.

SUMMARY OF THE INVENTION An object of the present invention is to provide a video playback device that can perform proper tracking even if tracking control information is temporarily unavailable.

[Means for solving the problem] The video playback device according to the present invention has a plurality of playback means for playing back recorded signals of a video recording medium, and obtains continuous video signals by switching and using the playback means. A video playback device, comprising an error detection means for detecting whether or not a playback signal by the playback means is normal and outputting a playback error signal in the case of poor playback, and a memory means capable of storing a video signal for a predetermined period of time. If the error detection means does not output the reproduction error signal, the memory means is controlled to write mode to write a normal reproduction signal, and when the error detection means outputs the reproduction error signal. includes a memory control means for controlling the memory means to a read mode and reading out the stored signal; an output means for selecting and outputting an output signal of the memory means in the event of a playback failure; and a tracking device according to the playback error signal. - Means for holding an error signal.

[Effect]

When the reproduction is temporarily defective, the tracking error signal is held by the above-mentioned holding means, so that the tracking becomes thick (does not go out of order) due to the temporal reproduction defect, and therefore a normal reproduction signal can be obtained thereafter. The memory means memorizes and saves the normal reproduction signal, and in the event of a reproduction error, the signal stored in the memory means immediately before is substituted, so that even if a reproduction error occurs in the reproduction means, Also, the reproduced image is
The reproduced image is almost the same as the reproduced image when no reproduction defect occurs, and the continuity of the image can be maintained, so that the viewer does not feel discomfort.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a block diagram of an embodiment in which the present invention is applied to a video tape playback device having a rotary head.

In Figure 1, 10.12 is a rotating drum (not shown)
a rotary head disposed on the radially opposite side of 14;
．． 16 are video R from rotating head 10°12 respectively.
This is a preamplifier that amplifies the F signal. 18 is an input terminal for a head switching signal formed from a signal indicating the rotational phase of the VTR rotating drum; 20 is an analog switch that switches according to the head switching signal; when the head switching signal is at "H" level, the rotation The trace output signal from the head 10 is selected, and when it is "L", the trace output signal from the rotary head 12 is selected.

22 is a video signal processing circuit that performs playback processing such as demodulation and time axis correction; 24 is a playback output detection circuit that monitors the playback signal from the rotary head 10° 12; and 26 is at least one
This is a video memory circuit with a storage capacity equivalent to one field, and includes an A/D converter for digital storage and a D/A converter for analog output. 28 is a head switching signal from the input terminal 18 and a reproduction output detection circuit 24;
This is a memory control circuit that controls the video memory circuit 26 according to the detection signal of. Reference numeral 30 designates an analog switch that switches according to a switching signal from the memory control circuit 28 to select either the output of the video signal processing circuit 22 or the output of the video memory circuit 26, and 32 represents a reproduction signal output terminal.

34 is the playback R from the switch (playback head 10.12)
a low pass filter (LPF) for extracting a biloft signal necessary for tracking from the F signal; 36 is a multiplier;
38 is a tracking reference signal input terminal; 4
0.42 is calculated from the output of the multiplier 36 to ro (
Horizontal synchronization frequency) or 3f) Band pass filter (BPF) that passes the frequency component of I, 44.46
48 is an envelope detector, 48 is a differential amplifier, 50 is a sample and hold circuit that samples and holds the output of the differential amplifier 48 in accordance with the reproduction error signal from the reproduction output detection circuit 24, and 52 is an output terminal for the tracking error signal. It is.

Next, the operation of the illustrated embodiment will be explained with reference to FIG.

FIG. 2 shows a case where no reproduction signal is obtained from the rotary head 12. FIG. 2 (al shows the head switching signal applied to the input terminal 18, (b) shows the output of the analog switch 20, and (C) shows the reproduction error signal output from the reproduction output detection circuit 24. , (dl is a write (W) or read (R) control signal of the video memory circuit 26 by the memory control circuit 28, (e) is a tracking error signal of the terminal 52, (fl is a control signal of the playback signal output terminal 32) is the output signal.

In this explanatory example, up to track n was played normally, but after that, (n+1), (n+3),
Assume that for some reason, sufficient reproduction output could not be obtained for tracks (n+5) and (n+7).

When the head switching signal shown in FIG. 2 (al) is input to the input terminal 18, the video signal processing circuit 22 and playback output detection circuit 24 are supplied with the signal shown in FIG. 2 (b) by switching the analog switch 20 for each field. ) is supplied.During normal playback, the playback output detection circuit 24 does not output a playback error signal, and the memory control circuit 28 keeps the video memory circuit 26 in the writing state. , the storage contents of the video memory circuit 26 are sequentially updated by the output of the video signal processing circuit 22.

Moreover, the multiplier 36 multiplies the tracking pilot signal output from the LPF-34 by the tracking reference signal from the terminal 38, and the BPF 40, 42
, detectors 44, 46 and differential amplifier 48 form a tracking error signal. Reproduction output detection circuit 24
When no hold signal is applied to the sample-and-hold circuit 50, the sample-and-hold circuit 50 directly outputs the output of the differential amplifier 48 to the terminal 52.

Therefore, when normal tracking is being performed,
The tracking error signal at terminal 52 has only very slight fluctuations.

When the reproduction signal is not obtained from the rotary head 12 during the period (n+1), the reproduction output detection circuit 24 transmits the reproduction error signal to the memory control circuit 28 and the sample/hold circuit 50.
to be applied. The memory control circuit 28 sets the video memory circuit 26 in a read mode in response to the playback error signal (FIG. 2(d)), and outputs the video memory circuit 26 from the video memory circuit 26 for a period n.
output the video signal. At the same time, switch 30
A switching signal is output to switch the analog switch 30 to the output side of the video memory circuit 30.

In addition, the sample and hold circuit 50 responds to the reproduction error signal from the reproduction output detection circuit 24, and the differential amplifier 48
Sample and hold the output of

Therefore, the tracking error signal at the terminal 52 becomes constant as shown in FIG. Normal playback from 10 will also become impossible.

Thereafter, during periods (n+2), (n+4), and (n+6) during which normal playback output is obtained from the rotary head 10, the video memory circuit 26 is put into a write operation state, a normal playback signal is written, and a playback error occurs. period (n+3
), (n+5), and (n+7), the signal written in the video memory circuit 26 in the previous period is read out, and the tracking error signal at the terminal 52 is held constant by the sample and hold circuit 50. By keeping the tracking error signal at the terminal 52 constant for a while and maintaining tracking, playback from the normal head can be continued. Therefore, by switching the operation of the video memory circuit 26 and switching the switch 30, the output terminal 2nd at 30
As shown in Figure (f), a reproduced video signal of normal level is obtained.

The above embodiment is for playing back a video tape, but in principle, video playback has a plurality of playback heads (optical pink-up in the case of optical playback) and switches and uses them field by field. The same applies to devices, and the present invention can be applied to such video playback devices in general.

Further, in the above embodiment, the case where two reproducing heads are used selectively has been described, but it goes without saying that the present invention can be similarly applied to the case where more reproducing heads are selectively used.

〔Effect of the invention〕

As can be easily understood from the above explanation, according to the present invention, even if the reproduction from one of the plurality of reproduction means becomes defective, the continuity of the reproduction output signal can be maintained by maintaining tracking. , the influence on the reproduced image can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a timing chart thereof.

Claims (1)

[Claims] A video playback device that has a plurality of playback means for playing back signals recorded on a video recording medium, and that obtains continuous video signals by selectively using the playback means, wherein the playback device determines whether or not the playback signal by the playback means is normal. an error detection means for detecting a playback error and outputting a playback error signal in the case of a playback failure; a memory means capable of storing a video signal for a predetermined period; and a memory for detecting a playback error when the error detection means does not output the playback error signal. A memory that controls the means to a write mode to write a normal reproduction signal, and when the error detection means outputs the reproduction error signal, controls the memory means to a read mode to read the stored signal. A video playback device comprising a control means, an output means for selecting and outputting an output signal of the memory means in the event of a playback failure, and means for holding a tracking error signal in accordance with the playback error signal. .