JPS60191582A - Video tape recorder - Google Patents

Abstract

PURPOSE:To simplify the circuit constitution and to save number of components by mixing a synchronizing signal from an oscillator and a character signal when no video signal exists. CONSTITUTION:When a video signal is fed to a video signal amplifier 9, a changeover switch 8 is thrown to the position of contact (a), horizontal/vertical synchronizing signals HS, VS are compared with signals HS, VS from an oscillator 17 and the oscillator 17 is controlled in response to the phase difference. Thus, the character signal and the video signal are synchronized. When no signal exists, the absence is detected by a no-signal detector 12 and the switch 8 is thrown to the position of contact (b). In this case, a synchronizing separator 14 is brought into free-run state, the signals HS, VS from the oscillator 17 are mixed, a composite synchronizing signal S is obtained, it is fed to a character signal superimposing circuit 7, mixed with the character signal, fed to a monitor and displayed on it.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a video tape recorder in which operation modes and the like can be displayed in characters on a monitor.

[Background of the invention]

In a conventional videotape recorder, recording.

Display means are provided for displaying operation modes such as playback, fast forwarding and rewinding, reception channel, tape counter, timer, etc. However, since a display element is attached to the operation button as a means of displaying the operation mode, the structure of the operation button becomes complicated, and many display elements must be used. This will affect the cost of the video tape recorder, and since display means such as the receiving channel, tape counter, and timer must be provided in the operating section with a limited area, it is necessary to Placement becomes very difficult. In recent years, video tape recorders have become increasingly multi-functional, and as a result, the issue of arrangement of various components in the operating section has become increasingly important.

In order to solve this problem, a video tape recorder is equipped with a nine-character signal generator, and the character signals from this character signal generator are used to display the operation mode, reception channel, etc. on the monitor.
Display the tenip counter, timer, etc. in text,
A technique has been proposed that reduces the number of display means on a video tape recorder.

FIG. 1 is a block diagram showing an example of such a conventional video tape recorder, in which l denotes an antenna.

2 is a tuner, 3 is a video amplifier, 4 is an FM modulator, 5 is a head, 6 is an output terminal, 7 is a character signal superimposition circuit, 8 is a changeover switch, 9 is a video signal amplifier, 10 is a changeover switch, 11 is FM 12 is a no-signal detector, 13 is a character signal generator, 14 is a sync separator, 15 is a sync signal generator, and 16 and 17 are changeover switches.

In the figure, the video signal of the channel selected by the tuner 2 (i.e., the reception channel) among the channels received by the antenna l during recording is transmitted to the video signal amplifier 3.
After being amplified, the signal is modulated by an FM modulator 4 and supplied to a head 5. At this time, the changeover switch 10 is closed to the contact a side, and the video signal from the video signal amplifier 3 is supplied to the video signal amplifier 9 through the changeover switch IO.

Also, during playback, the changeover switch 10 is closed to the contact P side, and the video signal reproduced by the head 5 and demodulated by the FM demodulator 11 is supplied to the video signal amplifier 9 through the changeover switch 10. Ru.

In this way, the video signal obtained during recording and playback is amplified by the video signal amplifier 9, and is supplied to the character signal superimposition circuit 7 through the changeover switch 8, which is closed to the contact a side, and is then amplified by the character signal generator 13. Character signals are superimposed. The output signal of the character signal superimposing circuit 7 is supplied from the output terminal 6 to a monitor (not shown), and is superimposed on the reproduced image of the video signal to display the characters.

On the other hand, the video signal from the video signal amplifier 9 is transmitted to the sync separator 1.
4, and a horizontal synchronizing signal (hereinafter referred to as H8) and a vertical synchronizing signal (hereinafter referred to as vs) are separated. H8
is supplied to the character signal generator 13 through the changeover switch 16 that is closed to the contact a side, and vS is supplied to the character signal generator 13 through the changeover switch 17 that is closed to the contact a side, and the character signal generator 13 is phase synchronized with the video signal. and it is working.

Therefore, on the monitor, characters are displayed at predetermined locations on the screen.

Furthermore, a no-signal detector 12 is provided to which the video signal from the video signal amplifier 9 is supplied.

During various modes such as fast forward, rewind, and stop, as well as recording mode,
For example, if the tuner 2 is not tuned and there is no video signal, or if a non-recorded part of the magnetic tape is scanned during playback mode and the video signal is not played back, the no-signal detector 12 will not detect this. In this case, the presence or absence of a video signal is determined based on the presence or absence of a synchronization signal, etc.), and the changeover switch 8° 16.17 is switched to the contact side.

On the other hand, a synchronization signal generator 15 is provided which generates a synchronization signal of the same frequency as the synchronization signal of the video signal, and a changeover switch 8. i'6. By switching the side pressure to which the synchronous signal generator 15 contacts, the composite synchronous signal S output from the synchronous signal generator 15 is supplied to the character signal superimposition circuit 7 via the changeover switch 8, and the lateral pressure Ha output from the synchronous signal generator 15 is , V
8 are supplied to the character signal generator 13 via changeover switches 16 and 17, respectively.

For this purpose, the character signal generator 13 is connected to the synchronization signal generator 15.
A character signal synchronized with H8 and V8 is generated, and this character signal is mixed with a composite synchronizing signal S from a synchronizing signal generator 15 in a character signal superimposing circuit 7. This mixed signal is supplied from the output terminal 6 to a monitor (not shown), and only characters are displayed at predetermined positions on the monitor.

In this way, the operating mode, reception channel, tape counter, timer, etc. are displayed in text on the monitor, and this text display is performed regardless of the presence or absence of a video signal.

, Yua, Ka17, Ogaya, □Oi1. Yes, there are a lot of □7.1 inches, so maybe the changeover switch is 8゜16.17
T. 5□□8keyuwa4. Because there is no part A#1, the circuit configuration is complicated. There are many (・.

In addition, during playback, dropouts may occur due to scratches on the magnetic tape and the synchronization signal may be lost, and during variable speed playback such as still playback, slow playback, and high-speed playback, the video signal may be partially lost. There is a possibility that the synchronization signal is lost, and in such a case, at least one of HS and vS is not supplied to the character signal generator 13 temporarily. As a result, the synchronization between the reproduced video signal and the character signal may be lost, and the position of the characters on the monitor may change, making it impossible to determine the characters.

[Purpose of the invention]

It is an object of the present invention to eliminate the drawbacks of the above-mentioned prior art, simplify the circuit configuration, reduce the number of parts, and to always synchronize the character signal superimposed on the video signal with the video signal. To provide a video tape recorder.

[Summary of the invention]

In order to achieve this object, the present invention provides an oscillator that generates a synchronization signal of the same frequency as the synchronization signal of the video signal, operates a character signal generator in synchronization with the synchronization signal from the oscillator, and operates the character signal generator in synchronization with the synchronization signal from the oscillator. When there is a video signal, the synchronization signal of the video signal and the synchronization signal from the oscillator are phase-synchronized and the character signal output from the character signal generator is superimposed on the video signal, and when there is no video signal. A feature is that sometimes the synchronization signal from the oscillator and the character signal from the character signal generator are mixed.

[Embodiments of the invention]

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

FIG. 2 is a block diagram showing an embodiment of the video tape recorder according to the present invention, in which 16 is a phase comparator, 17 is an oscillator, 18 is a mixing circuit, and parts corresponding to those in FIG. 1 are denoted by the same reference numerals. Some explanations will be omitted.

In FIG. 2, an oscillator 17 generates Ha, vsy, which are equivalent to (S, VS) of the video signal processed by the video signal amplifier 9, and a character signal generator 13 generates H8 from this oscillator 17.
, VS.

Further, H8, VS from the oscillator 17 are mixed in a mixing circuit 18 and supplied as a composite synchronizing signal S to the contact bK of the changeover switch 8. Furthermore, H8 from the oscillator 17,
VS is the phase comparator 16 and H8, V from the synchronous separator 14
The phase is compared with S, and the respective phase difference signals are supplied to the oscillator 17 as control signals.

Therefore, when a video signal is being supplied to the video signal amplifier 9, the no-signal detector 12 detects this, and the changeover switch 8 is closed to the contact a side. At this time, the synchronous separator 14 is also supplied with the video signal to the video signal amplifier 9, and outputs H8 and VS. These H8 and VS are compared in phase with H8 and VS from the oscillator 17 by the phase comparator 16, and the oscillator 17 is controlled according to the phase difference between them.

For this reason, H8, VS from the sync separator 14 and H8, VS from the oscillator 17 are in phase synchronization, and therefore the character signal output from the character signal generator 13 and the video signal are in phase synchronization. There is.

This character signal is sent to a character signal superimposing circuit 7 and then to a video signal amplifier 9.
The signal is superimposed on the duck video signal and is supplied from the output terminal 6 to a monitor (not shown). Therefore, on the monitor, the characters are superimposed on the reproduced image based on the video signal and displayed at a predetermined position.

In this case, in the playback mode, the playback synchronization signal is temporarily lost due to dropout or variable speed playback, and even if H8 and VS cannot be obtained from the synchronization separator 14, the oscillator 17
operates in synchronization with the synchronization signal of the video signal for a certain period of time due to its time constant. Therefore, the character signal generator 13 generates a character signal phase-synchronized with the video signal without being affected by the loss of the reproduction synchronization signal. Occur. Therefore, as long as the video signal is supplied to the video signal amplifier 9, characters can be stably displayed on the monitor.

Next, if there is no video signal even in various operation modes such as fast-forwarding, rewinding, stopping, recording, and playback modes, the no-signal detector 12 detects this and changes the changeover switch 8 to the contact side. Switch.

At this time, the synchronous separator 17 enters a free run state. H8 and VS from the oscillator 17 are mixed in the mixing circuit 18,
The composite synchronizing signal S is supplied to the character signal superimposing circuit 7 via the changeover switch 8, mixed with the character signal from the character signal generator 13, and supplied to the monitor.

By the way, although the oscillator 17 is in a frozen state, the H8. VS is the video signal H8, VS
As a result, the monitor has a frequency equivalent to
Characters are displayed stably in the specified position.

In this way, this embodiment does not require a switch means for switching the synchronization signal generation source for the character signal generator 13 depending on the presence or absence of the video signal of the no-signal detection circuit 12, and in any case, the synchronization signal generation source can be switched. Therefore, the circuit configuration can be simplified and the number of parts can be reduced. Further, since the oscillator 17 including the mixer 189 and the phase comparator 16 in the above embodiment can be realized at a cost substantially equivalent to that of the synchronizing signal generator 15 in FIG. 1, at least the above switch means is provided. Costs can be reduced by the amount that is no longer needed. , [Effects of the Invention] As explained above, according to the present invention, stable character display can be realized at all times, and the number of components can be reduced by simplifying the circuit configuration, which is superior to the above-mentioned conventional technology. It is possible to provide a video tape recorder with excellent functions at a low cost except for its drawbacks.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an example of a conventional video tape recorder, and FIG. 2 is a block diagram showing an embodiment of the video tape recorder according to the present invention. 6...Output terminal, 7...Character signal superimposition circuit, 9...Video signal amplifier, 12...
・No signal detector, 13...Character signal generator, 1
4... Synchronous separator, 16... Phase comparator, 17... Oscillator, 18... Mixing circuit.

Claims (1)

[Claims] The presence or absence of a video signal is determined during recording and playback, and if there is a video signal, the character signal from the character signal generator is superimposed on the video signal and output, and when there is no video signal, the character signal and the synchronization signal are superimposed on the video signal and output. In a video tape recorder that mixes and outputs a video signal, a synchronization separation circuit to which the video signal is supplied, an oscillator that generates a synchronization signal, and a phase difference between the output signal of the synchronization separation circuit and the output signal of the oscillator. By providing a phase comparator that compares and outputs a control signal of the oscillator, and controlling the character signal generator in synchronization with the synchronization signal from the oscillator, the synchronization signal from the oscillator can be used when there is no video signal. A video tape recorder characterized in that a synchronization signal is mixed with a character signal from the character signal generator.