JPH0369293A - Device for regenerating video signal - Google Patents

Abstract

PURPOSE:To prevent the generation of a skew due to the phase shift of a horizontally synchronizing signal by providing a delay means for switching the delay time in accordance with the switching of a head switching means and correcting the phase shift of the horizontally synchronizing signal. CONSTITUTION:The terminal 24c of a head amplifier switch 24 is connected to the terminal 27b of a skew correcting switch 27 and also connected to the terminal 27a of the switch 27 through a delay line for delaying a signal only by a half of one horizontal period. The delay time is switched by the delay line 26 and the skew correcting switch 27 in accordance with the switching operation of the switch 24 to correct the phase shift of the horizontally synchronizing signal. Even if video signals outputted from plural magnetic heads are switched by the head switching means, the generation of the skew can be prevented.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a video signal reproducing device for reproducing video signals recorded on a magnetic tape, and in particular, uses a double azimuth head or a multi-head to perform noiseless search and The present invention relates to a video signal reproducing device capable of performing trick reproduction of field stills and the like.

[Conventional technology]

As an example of a conventional video signal reproducing device, a video signal reproducing device equipped with a double azimuth head and capable of performing a search operation in a standard mode of the VH3 system will be described.

For example, as shown in FIG. 3, the video signal reproducing apparatus is provided with a double azimuth head 11 including a magnetic head L1 and a magnetic head R having mutually different azimuth angles. The magnetic head L and the magnetic head R are arranged with a gap interval corresponding to, for example, 1/2 of one horizontal period.

The magnetic head and the magnetic head R are connected to the head amplifier switch 1 via the head amplifiers 12 and 13, respectively.
It is connected to the terminal 14a1 or the terminal 14b of No.4.

A terminal 14c of the head amplifier switch 14 is connected to a buffer amplifier 15.

The buffer amplifier 15 directly connects the skinny correction switch 1
7 and is connected to terminal 17b of 1 horizontal period.
It is connected to a terminal 17a of a skew correction switch 17 via a delay line 16 that delays the signal by /2.

A terminal 17c of the skew correction switch 17 is connected to an output terminal 19 via a reproduced video signal processing circuit 18 that performs processing such as extraction of a synchronization signal.

When a search operation is performed in such a video signal reproducing apparatus, each time the magnetic head and the magnetic head R trace a track recorded at a corresponding azimuth angle on the magnetic tape, for example, as shown in FIG. (a) (b)
), video signals are output alternately. Here, in FIG. 4, only the horizontal synchronization signal is shown as the video signal for convenience.

Then, as shown in FIG. 4(C), HAM changes in accordance with the level of the video signal output from each magnetic head L-R and at a timing synchronized with the horizontal synchronization signal. By switching the head amplifier switch 14 based on the PSW signal and selectively switching between the magnetic head L and the magnetic head R, a continuous video signal is obtained as shown in FIG. 4(d).

Incidentally, in the video signals output from the magnetic head and the magnetic head R, the phases of the horizontal synchronizing signals are shifted from each other by 172, which is one horizontal period. Therefore, the signal output from the head amplifier switch 14 will be out of phase with the horizontal synchronization signal before and after the head amplifier switch 14 is switched. In this case, horizontal synchronization cannot be achieved, resulting in skew.

Therefore, by using the delay line 16, (e) in FIG.
As shown in the figure, a signal delayed by 1/2 of one horizontal period is generated, and this delayed signal and the original signal are switched in synchronization with the switching timing of the head amplifier switch 14. That is, as shown in FIG. 4(f), the skew correction switch 17 is switched based on the skew correction SW signal obtained by inverting the HAMPSW signal, and the fourth
As shown in (g) of the figure, the signal output from the magnetic head R is delayed by 1/2 of one horizontal period. As a result, even when the video signal reproduced by the magnetic head L and the video signal reproduced by the magnetic head R are switched, it is possible to prevent skew from occurring due to a phase shift of the horizontal synchronization signal. There is.

[Problem to be solved by the invention]

However, in the conventional video signal reproducing device described above, when performing trick playback such as noiseless search or field still, although the phase of the horizontal synchronization signal is not shifted before and after the head amplifier switch 14 is switched, the video signal is not delayed. When switching to a delayed video signal, the video signal output from the skew correction switch 17 will be a mixture of video signals delayed by 1/2 of l horizontal period. As a result, the screen becomes unsightly due to the lack of line correlation, making it difficult to improve the image quality.

[Means to solve the problem]

In order to solve the above problems, a video signal reproducing device according to the present invention includes a plurality of magnetic heads that reproduce video signals recorded on a magnetic tape, and a head that switches video signals output from the plurality of magnetic heads. a switching means; a first delay means for correcting the phase shift of the horizontal synchronizing signal by switching the delay time according to the switching by the head switching means; It is characterized by comprising a second delay means that switches and outputs a signal delayed by an integral multiple.

[For production]

With the above configuration, when performing trick playback such as noiseless search or field still, even if the video signals output from multiple magnetic heads are switched by the head switching means, the phase shift of the horizontal synchronization signal will be the same as that of the first one. Since it is corrected by the delay means, it is possible to prevent skew from occurring.

Moreover, when the head switching means switches the video signal, the second delay means outputs a signal delayed by an integral multiple of the period of the horizontal synchronizing signal, so that the partially delayed video with no line correlation is generated. The signal is masked and
- No mixed output. Therefore, it is possible to prevent the screen from becoming unsightly.

〔Example〕

As an embodiment of the present invention, FIG. 1 and FIG.
The explanation will be as follows based on the figures.

As shown in FIG. 1, the video signal reproducing device includes a double magnetic head L and a magnetic head R having different azimuth angles, which are a plurality of magnetic heads for reproducing video signals recorded on a magnetic tape. An azimuth head 21 is provided. The magnetic head L and the magnetic head R are arranged with a gap interval corresponding to, for example, 1/2 of one horizontal period.

The magnetic head L1 and the magnetic head R are connected to a head amplifier switch 2 via head amplifiers 22 and 23, respectively.
It is connected to the terminal 24a1 or the terminal 24b of No.4.

This head amplifier switch 24 is a HAMPS switch which will be described later.
It is controlled by the W signal and acts as head switching means for switching the video signals output from the magnetic heads LR.

The terminal 24c of the head amplifier switch 24 is directly connected to the terminal 27b of the skew correction switch 27, and is also connected to the terminal 27b of the skew correction switch 27 via a delay line 26 that delays the signal by 1/2 of one horizontal period.
7a. This skew correction switch 27
is controlled by a skew correction SW signal, which will be described later, to switch the delay time of the video signal.

The delay line 26 and the skew correction switch 27 constitute a first delay means that changes the delay time in accordance with the switching by the head amplifier switch 24 and corrects the phase shift of the horizontal synchronizing signal.

A terminal 27c of the skew correction switch 27 is connected to a chroma signal processing circuit 31 and a luminance signal demodulation circuit 32 that performs FM demodulation of a luminance signal. Luminance signal demodulation circuit 3
The output terminal 2 is directly connected to the terminal 3 of the IH correction switch 34.
4b, and is also connected to a terminal 34a of an IH correction switch 34 via a delay line 33 that delays the signal by one horizontal period.

The IH correction switch 34 is controlled by an IH correction SW signal to be described later, and when the head amplifier switch 24 switches the video signal, the IH correction switch 34 outputs a signal delayed by a time equal to the period of the horizontal synchronization signal by the delay line 33 and the original signal. In other words, the delay line 33 and the IH correction switch 34 constitute a second delay means.

A terminal 34c of the IH correction switch 34 is connected to a luminance signal processing circuit 35 that performs processing such as extraction of a horizontal synchronization signal. The luminance signal processing circuit 35 is connected to a mixing circuit 36 together with the chroma signal processing circuit 31, so that the chroma signal and the luminance signal are mixed by the mixing circuit 36 and outputted from an output terminal 37. .

Further, the head amplifiers 22 and 23 further include detection circuits 41 and 42 that respectively detect the video signals reproduced by the magnetic heads L-R and output envelope signals.
It is connected to the. The detection circuits 41 and 42 are each
It is connected to the + terminal or one terminal of the comparator 43.

The output terminal of the comparator 43 is connected to the flip-flop 44
is connected to the D terminal of A horizontal synchronizing signal output from the luminance signal processing circuit 35 is input to a clock terminal of the flip-flop 44 .

The signal output from the Q terminal of the flip-flop 44 is
The HAMPSW signal is used to control switching of the head amplifier switch 24 as described above. The signal output from the Q terminal of the flip-flop 44 is also input to the clock terminal of the flip-flop 45. The D terminal of this flip-flop 45 is pulled up to high level.

The d terminal of the flip-flop 44 is 1/2 of one horizontal period.
NA via a delay line 46 that delays the signal by
It is connected to the ND circuit 48.

This NAND circuit 48 also includes a luminance signal processing circuit 3.
A horizontal synchronizing signal outputted from the horizontal synchronizing signal 5 is input via a delay line 47 that delays the signal by a time W equal to the pulse width of the horizontal synchronizing signal. NA
The output terminal of the ND circuit 48 is connected to the clear terminal of the flip-flop 45.

The six terminals of the flip-flop 45 are connected to the AND circuit 49 together with the silk terminal of the flip-flop 44 . The signal output from the AND circuit 49 is designed to control switching of the skew correction switch 27 as a skew correction SW signal.

A signal output from the Q terminal of the flip-flop 45 as an IH correction instruction signal is input to an OR circuit 50 together with a dropout detection signal output from the luminance signal demodulation circuit 32. The signal output from the OR circuit 50 is designed to control switching of the IH correction switch 34 as an IH correction SW signal.

In the above configuration, when a search operation is performed for a video signal recorded on a magnetic tape, magnetic heads L and R each trace a track recorded at a corresponding azimuth angle on the magnetic tape. ,
For example, as shown in FIGS. 2(a) and 2(b), video signals are output alternately. Here, in FIG. 2, for convenience, only the horizontal synchronization signal is shown as the video signal.

The signals output from the magnetic head L and the magnetic head R are detected by detection circuits 41 and 42, respectively.
Envelope signals are output from the detection circuits 41 and 42. The comparator 43 compares the levels of these envelope signals, and when the level of the envelope signal output from the detection circuit 41 is large, that is, the magnetic head L
When a video signal is being output from the magnetic head R, a high level signal is output, while when the level of the envelope signal output from the detection circuit 42 is high, that is, when a video signal is being output from the magnetic head R, a low level signal is output. Outputs a level signal.

Therefore, for example, when a video signal is output from the magnetic head L, the signal output from the Q terminal of the flip-flop 44, that is, the HAMPSW signal, is
As shown in C), the signal is kept at a high level, and the terminal 24c of the head amplifier switch 24 is connected to the terminal 24a. That is, as shown in FIG. 2(d), the signal output from the magnetic head L is connected to the terminal 2 of the head amplifier switch 24.
Supplied to 4C.

The signal supplied to the terminal 24c of the head amplifier switch 24 is directly transmitted to the terminal 24c of the skew correction switch 27.
7b, and the signal delayed by 1/2 of one horizontal period is supplied to the terminal 27a of the skew correction switch 27 via the delay line 26, as shown in FIG. 2(e). .

Furthermore, when the video signal is being output from the magnetic head L as described above, the signal output from the Wataru terminal of the flip-flop 44 is at a low level, and the AND circuit 49 operates as shown in FIG. 2(f). , a low level signal is output as a skew correction SW signal. Therefore, the terminal 27c of the skew correction switch 27 is connected to the terminal 27b, and the undelayed video signal is sent to the chroma signal processing circuit 31.
, and is input to the luminance signal demodulation circuit 32.

Therefore, from the luminance signal demodulation circuit 32, (
As shown in g), a demodulated luminance signal containing a horizontal synchronizing signal having the same phase as the video signal output from the magnetic head L is output, and is supplied as it is to the terminal 34b of the IH correction switch 34, and also is connected to the delay line 33. through the second
As shown in (h) of the figure, a signal delayed by one horizontal period is supplied to the terminal 34a.

Furthermore, when the video signal is output from the magnetic head L as described above and the signal output from the Q terminal of the flip-flop 44 is maintained at a high level, the flip-flop 45 is in the reset state as described later. Yes, Q
The signal output from the terminal as the IH correction instruction signal is maintained at a low level, as shown in (i) of FIG.

Therefore, the OR circuit 50 outputs a low-level signal as the IH correction SW signal, except when the dropout detection signal is output from the luminance signal demodulation circuit 32.

When a low level signal is output from the OR circuit 50, I
The terminal 34c of the H correction switch 34 is connected to the terminal 34b, and the signal output from the luminance signal demodulation circuit 32 is inputted to the luminance signal processing circuit 35 as it is. The luminance signal output from the luminance signal processing circuit 35 is combined with the chroma signal output from the chroma signal processing circuit 31 by the mixing circuit 36, and is output from the magnetic head L as shown in (j) in FIG. The video signal is output from the output terminal 37 as a video signal containing a horizontal synchronization signal having the same phase as the video signal.

Also, the magnetic head from which the video signal is output is the magnetic head L.
When changing from magnetic head R to magnetic head R, comparator 43
A low level signal is output from flip-flop 4.
The signal output from the Q terminal of No. 4 changes from high level to low level at a timing synchronized with the horizontal synchronizing signal, as shown in FIG. 2(C). Then, the terminal 24c of the head amplifier switch 24 changes from the terminal 24a to the terminal 24b.
The signal output from the magnetic head R is then supplied to the terminal 24C of the head amplifier switch 24. Therefore, the terminal 24 of the head amplifier switch 24
As shown in FIG. 2(d), a video signal is continuously supplied to C.

Then, as described above, when the magnetic head from which the video signal is output changes from the magnetic head L to the magnetic head R, and the signal output from the Q terminal of the flip-flop 44 changes from high level to low level, the The signal output from the silkworm terminal changes from low level to high level, as shown in FIG. 2(k). Further, since the D terminal of the flip-flop 45 is pulled up, the signal output from the d terminal of the flip-flop 45 changes from a high level to a low level, as shown in (1) of FIG.

Therefore, the AND circuit 49 continues to output a low-level signal, as shown in FIG. A video signal is input.

Furthermore, when the magnetic head that outputs the video signal changes from the magnetic head L to the magnetic head R as described above, the signal output from the Q terminal of the flip-flop 45 changes as shown in (i) of FIG. Since it will be at a high level, OR
The signal output from the circuit 5o also becomes high level. Therefore, the terminal 34c of the IH correction switch 34 is connected to the terminal 34a.
A signal delayed by one horizontal period as shown in FIG. 2(h) is input to the luminance signal processing circuit 35 via the delay line 33.

Therefore, in the video signal output from the output terminal 37, as shown in FIG. 2 (j), the video signal with no line correlation is masked, and the screen does not become unsightly.

Furthermore, as shown in FIG. 2(m), the NAND circuit 48 receives a signal that is output from the silk terminal of the flip-flop 44 and is delayed by 1/2 of the horizontal period via the delay line 46. As shown in FIG. 2(n), a signal obtained by delaying the horizontal synchronizing signal by a time W equal to the pulse width of the horizontal synchronizing signal is inputted via the delay line 47. Therefore, after the magnetic head from which the video signal is output changes from the magnetic head L to the magnetic head R, and the signal output from the Q terminal of the flip-flop 44 switches from high level to low level, one horizontal period is counted. After the time has elapsed, the NAND circuit 48 outputs a low-level pulse signal, as shown at (0) in FIG.

The flip-flop 45 is reset by the low level pulse signal output from the NAND circuit 48. That is, by providing the delay lines 46 and 47, the flip-flop 45 is maintained in the set state when the horizontal synchronizing signal falls when the magnetic head is switched, and when the next horizontal synchronizing signal rises. , is reset in synchronization with the falling edge of the horizontal synchronization signal after one horizontal period has elapsed since the magnetic head was switched.

When the flip-flop 45 is reset, the signal output from the page terminal of the flip-flop 45 becomes high level as shown in (i> in FIG. 2), and the signal output from the AND circuit 49 also becomes As shown in Cr) in FIG. 2, the level becomes high. Therefore, the terminal 27c of the skew correction switch 27 is connected to the terminal 27a, and the chroma signal processing circuit 31 and the luminance signal demodulation circuit 32 are connected to the chroma signal processing circuit 31 and the luminance signal demodulation circuit 32 via the delay line 26. A signal delayed by 1/2 of the horizontal period is input.

Furthermore, when the flip-flop 45 is reset, the signal output from the Q terminal of the flip-flop 45 is
As shown in (i) of the figure, the level becomes low. Therefore,
The terminal 34c of the 1H correction switch 34 is connected to the terminal 34a, and a signal delayed by 1/2 of one horizontal period is input to the luminance signal processing circuit 35 only via the delay line 26.

Therefore, the video signal output from the output terminal 37 is skewed because the phase shift of the horizontal synchronization signal in the video signal output from the magnetic head R is corrected, as shown in FIG. 2 (j). occurrence is prevented.

On the other hand, when the magnetic head from which the video signal is output changes from the magnetic head R again to the magnetic head L, as shown in FIG.
c) As shown in (k), the signal output from the Q terminal of the flip-flop 44 changes from low level to high level, and the signal output from the d terminal changes from high level to low level.

Therefore, the terminal 24c of the head amplifier switch 24 is switched from the terminal 24b to the terminal 24a, and the terminal 27c of the skew correction switch 27 is switched to the terminal 27b.

Further, when the signal output from the Q terminal of the flip-flop 44 changes from low level to high level as described above, the state of the flip-flop 45 changes as shown in (i) in FIG.
Since there is no change as shown in (f), the terminal 34c of the IH correction switch 34 remains connected to the terminal 34b.

Therefore, from the output terminal 37, (j) in FIG.
As shown in , the phase of the horizontal synchronization signal is not shifted.
In addition, a video signal with good line correlation is output.

In this way, when the magnetic head is switched, the phase shift of the horizontal synchronization signal is corrected, and the video signal with no line correlation is masked, which can cause skew or make the screen unsightly. This will definitely be prevented.

In this embodiment, the delay line 33 is also used to correct the dropout of the horizontal synchronizing signal, but the present invention is not limited to this, and a dedicated delay line may be provided. Furthermore, in that case, the position where the delay line is provided is not limited to the output side of the luminance signal demodulation circuit 32;
Chroma signal processing circuit 31 and luminance signal demodulation circuit 32
Further, the delay time is not limited to one horizontal period but may be an integral multiple of one horizontal period.

On the other hand, the delay time of the delay line 26 is not limited to 1/2 of the horizontal period, but depends on the gap interval of each magnetic head, the recording format of the magnetic tape, etc. of the video signal output from each magnetic head. It is only necessary to set the horizontal synchronizing signals included in the horizontal synchronizing signals so that the phases thereof match.

〔Effect of the invention〕

As described above, the video signal reproducing device according to the present invention includes: a plurality of magnetic heads for reproducing video signals recorded on a magnetic tape; a head switching means for switching video signals output from the plurality of magnetic heads; a first delay means that changes the delay time according to the switching by the head switching means and corrects the phase shift of the horizontal synchronization signal; and a first delay means that changes the delay time according to the switching by the head switching means, and delays by an integral multiple of the period of the horizontal synchronization signal when the video signal is switched by the head switching means. This configuration also includes a second delay means that switches and outputs the received signal.

As a result, when performing trick playback such as noiseless search or field still, even if the video signals output from multiple magnetic heads are switched, the phase of the horizontal synchronization signal will not shift and skew will occur. can be prevented.

Moreover, when switching video signals, it is possible to prevent partially delayed video signals with no line correlation from being mixed, thereby preventing the screen from becoming unsightly, and improving the video quality during trick playback. play.

[Brief explanation of drawings]

1 and 2 show one embodiment of the present invention. FIG. 1 is a block diagram showing the configuration of a video signal reproducing device. FIG. 2 is a time chart showing signals of each part in the video signal reproducing device. 3 and 4 show conventional examples. FIG. 3 is a block diagram showing the configuration of a conventional video signal reproducing device. FIG. 4 is a time chart showing signals of various parts in a conventional video signal reproducing device. L-R is a magnetic head, 24 is a head amplifier switch (head switching means), 26 is a delay line (first delay means), 27 is a skew correction switch (first delay means), and 33 is a delay line (second delay means). delay means), 34
is an IH correction switch (second delay means).

Claims (1)

[Claims] 1. A plurality of magnetic heads for reproducing video signals recorded on a magnetic tape, a head switching means for switching the video signals output from the plurality of magnetic heads, and switching a delay time in accordance with switching by the head switching means;
When switching the video signal by the first delay means for correcting the phase shift of the horizontal synchronization signal and the head switching means,
A video signal reproducing device comprising: a second delay means for switching and outputting a signal delayed by an integral multiple of a period of a horizontal synchronizing signal.