JPS6251033B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an output circuit for a reproduced video signal in a video tape recorder.

Conventionally, the main method for displaying a reproduced video signal on a television screen in a video tape recorder (hereinafter abbreviated as VTR) has been to display only one reproduced image. In recent years, television receivers that can simultaneously display two video signals on one screen have been released, but they do not have complex and expensive signal processing circuits built into them, such as video signal band conversion. Therefore, the VTR's playback video signal output remained the same as before.

Additionally, magnetic memory and microcomputers are used to divide one screen and display multiple images simultaneously, but this method requires expensive magnetic memory and microcomputers. Furthermore, it is difficult to incorporate it into a VTR.

An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, to be able to display other video signals on a part of the playback screen of a VTR without the need for modifying the television receiver or using a microcomputer, and to be able to incorporate the video signal into the VTR. The purpose is to provide an output circuit for video signals.

The present invention, in a VTR, synchronizes the vertical synchronization signal of a reproduced video signal with the vertical synchronization signal of another video signal in phase, and switches and inserts another video signal into a part of the reproduced video signal during each field period. It is characterized by

FIG. 1 shows a block diagram of an embodiment of a video signal output circuit according to the present invention, and FIG. 2 shows main signals of the same figure. In FIG. 1, 1 is a reproduced video signal obtained from a VTR, 2 is a second video signal input from another VTR or externally, and 3 is a head switching signal. The head switching signal 3 is generated by the switching signal generator 4 in the next stage, as will be described later.
It is converted into a switching signal 5 and a gate signal 6.
By this switching signal 5 and gate signal 6, the reproduced video signal 1 and the second video signal 2 are switched by the switch 7 during every field period, and a mixed video signal 8 is obtained. Further, a composite synchronization signal 10 obtained from the second video signal 2 via the synchronization separation circuit 9 is input to a gate 11 and a drum servo control circuit 12. At the gate 11, a part of the synchronization signal of the second video signal 2 is extracted by the gate signal 6, and a video signal 13 at a black level (or a certain level) is obtained.
becomes. This video signal 13 and mixed video signal 8 are input to a mixing circuit 14 and become an output video signal 15. Here, the switch 7 is controlled by an external selection switch signal 22 to output the above-mentioned mixed video, only the reproduced video, or only the second video.

On the other hand, in the drum servo control circuit 12, a vertical synchronization signal 17 is obtained from the composite synchronization signal 10 in a vertical synchronization separation circuit 16. This vertical synchronization signal 17
is the reference signal 18 built into the servo control circuit 12.
Then, the selection switch signal 22 switches the switch 19 and inputs the signal to the phase comparator circuit 20.

On the other hand, a drum pulse 21 synchronized with a video head (not shown) is input to the other input terminal of the phase comparison circuit 20. Therefore, by this drum servo control circuit 12, the vertical synchronization of the reproduced video signal is brought into phase synchronization with the vertical synchronization signal 17 of the second video signal 2.

FIG. 3 shows how the output video signal 15 obtained as described above is displayed on a television receiver. The band-shaped portion 35 indicated by diagonal lines in the figure is the second
This is the pulse period of the gate signal 6 in the figure, and is located at the portion where the reproduced video 36 is switched to the second video 37. As can be seen, by varying the pulse width of the signal 5 in FIG.
The position of 5 can be easily changed.
Further, the width of the band-shaped portion is determined by the pulse width of the gate signal 6, and therefore the width of the band-shaped portion 35 can also be easily varied. The method of generating the switching signal 5 and the gate signal 6 will be explained below.

A specific example of the switching signal generator 4 and switch 7 shown in FIG. 1 is shown in FIG. 4, and the waveforms of the main parts of the same figure are shown in FIG. In FIG. 4, the same signals and blocks as in FIG. 1 are designated by the same reference numerals.
First, the head switching signal 3 is converted into an edge pulse 23 by the edge detection circuit 22 at the next stage, which has a negative pulse at each of the rising and falling parts of the signal. This edge pulse 23 triggers a monostable multi-vibrator (hereinafter abbreviated as mono-multi) 24, which outputs a switching signal 5 with a pulse width determined by a variable resistor 25. By changing this pulse width, the switching position of the video signal changes. Further, the falling edge of this switching signal 5 triggers the next-stage monomulti 26 to output a gate signal 6 with a pulse width determined by a variable resistor 27. By changing this pulse width, the width of the strip portion 35 in FIG. 3 changes. Furthermore, gate signal 6 and switching signal 5 are
It is input to a NOR gate 28 to obtain a switching signal 29.

Switching signals 5 and 2 obtained in this way
By controlling switches 30 and 31 at 9, the reproduced video signal 1 and the second video signal 2 are gated to obtain intermittent video signals 32 and 33, respectively. These two video signals 32,
33 is input to a mixing circuit 34 at the next stage to obtain a mixed video signal 8. If it is desired to use only the reproduced video signal 1 or only the second video signal 2 as the output video signal 8, the monomultis 24 and 26 may be set or reset.

As described above, when the vertical synchronization signal of the VTR playback video signal is phase-synchronized with the vertical synchronization signal of the second video signal 2 from the outside, the horizontal synchronization is generally discontinuous at the switching position of the video signal. It is becoming. This discontinuity in horizontal synchronization may cause skew when viewed on a television screen, causing screen disturbances. The effect of this skew is the
Generally, the period is 1 to several ms depending on the AGC characteristics, but in the present invention, by replacing this period with a black or other constant level signal, screen disturbances can be seen as black or other constant level strips on the screen. is prevented.

In the above embodiment, on the screen of the television receiver,
Although the upper part is a reproduced video and the lower part is another video, the present invention is not limited to this. Further, although one signal is used as an example of another video signal, it is easy to configure one screen with a plurality of video signals at the same time as long as the video signals are synchronized with each other.

As described above, according to the present invention, there is no need for an expensive and complicated signal processing circuit outside the VTR that was required in the conventional technology, and the structure is inexpensive and simple, so it can be easily built into the VTR. .

Furthermore, the switching position between the two images on the television screen can be moved arbitrarily, and the switch can easily be used to switch only to the reproduced image or only to other external images.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention;
Fig. 2 is a waveform diagram of the main part thereof, Fig. 3 is a diagram showing a television screen obtained by the present invention, Fig. 4 is a block diagram showing a specific example of the main part of Fig. 1, and Fig. 5 is the main part. FIG. 1... Reproduction video signal, 2... Second video signal, 3...
Head switching signal, 4...Switching signal generator, 7...
Switch, 8...Mixed video signal, 10...Composite synchronization signal, 12...Drum servo control circuit, 15...Output video signal, 22...Selection switch signal.

Claims (1)

[Scope of Claims] 1. A video signal output circuit of a magnetic reproducing device configured to sequentially switch between a reproduced video signal and a second video signal to configure each field, which receives a head switching signal, a switching signal generator that generates a switching signal that lasts for a first scheduled time from the point of change of the switching signal and a gate signal that continues for a second scheduled time immediately thereafter; a reproduced video signal, a second video signal, the switching signal and the gate; The present invention is characterized by comprising a switch circuit which receives a signal and switches and outputs a reproduced video signal and a second video signal at a first scheduled time before the gate signal and at a time after the gate signal in each field. Video signal output circuit for magnetic playback equipment. 2. The video signal output circuit for a magnetic reproducing apparatus according to item 1, further comprising means for maintaining the level of the output video signal at a constant value at the second scheduled time when the gate signal is generated. 3. A video signal output circuit for a magnetic reproducing apparatus according to item 1 or 2, characterized in that a vertical synchronization signal of another video signal is used as a reference signal for a reproducing drum servo control system. 4. A video signal output circuit for a magnetic reproducing device according to any one of items 1 to 3, characterized in that at least one of the first and second scheduled times is variable.