JPS59167801A - Device for recording or recording and reproducing video signal - Google Patents

Abstract

PURPOSE:To prevent an inaccurate character broadcast signal from being displayed by activating a clip circuit so as to eliminate the character broadcast signal when a character broadcast signal detecting circuit detects the character broadcast signal. CONSTITUTION:When a character broadcast is superimposed on an input video signal, a character broadcast signal presence detecting circuit 8 detects it, makes a pulse signal P pass through and supplies it to a clip circuit 3. The circuit 3 clips the video signal to a pedestal level only when the signal P is inputted. The video signal whose character broadcast signal is clipped is applied to a video signal recording processing circuit 4, where the video signal is processed in the form suitable to be applied to a magnetic head 5 and the processed signal is recorded on a magnetic tape 6. Since the video signal eliminating the character broadcast signal is recorded in this way, the display of the inaccurate character broadcast is avoided.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a video signal recording or recording/reproducing device into which a video signal on which a teletext signal is superimposed is input.

Conventional configurations and their problems Conventionally, in video signal recording or recording/playback devices such as video tape recorders, the frequency characteristics or phase characteristics of the recorded and played video signals are poor, and furthermore, due to noise or dropouts, etc. However, there was a problem in that the teletext signal was not transmitted accurately and an inaccurate teletext signal was displayed on the television receiver.

OBJECTS OF THE INVENTION It is an object of the present invention to eliminate the above-mentioned conventional problem, that is, the transmission of inaccurate teletext signals from a video signal recording/reproducing device such as a video tape recorder.

Structure of the Invention In order to achieve the above object, the present invention includes a teletext signal detection circuit for detecting a teletext signal included in an input video signal and a clip circuit, and the teletext signal detection circuit detects a teletext signal included in an input video signal. When a broadcast signal is detected, the clipping circuit is activated and a video signal from which the teletext signal has been removed is recorded on a magnetic recording medium. Regardless of the characteristics of the recording/reproducing system, the television An inaccurate teletext signal will not be displayed on the receiver.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of the main configuration of the present invention, in which a video signal including a teletext signal inputted to an input terminal 1 is inputted to a teletext signal detection circuit 2 and a clipping circuit 3. Further, the output signal of the teletext signal detection circuit 2 is also input to the clip circuit 3. The output signal of the clipping circuit 3 is supplied to the magnetic head 5 via the video signal recording processing circuit 4 and recorded on the magnetic tape 6. The teletext signal detection circuit 2 includes a position detection circuit 7 and a teletext signal presence/absence detection circuit 8. Furthermore, the position detection circuit 7 is composed of a vertical synchronization signal separation circuit 9 and a delay circuit 10.

FIG. 2A shows an example of a video signal input to the input terminal 1, and shows the vertical retrace period part thereof. Figure 2A
The numbers 524, 525.1 to 22 indicate horizontal scanning line numbers (hereinafter abbreviated as H), indicating that a teletext signal is superimposed on 201-1. the current,
The positions where the teletext signal is superimposed are i 0 l-1 to 21
) 1 and between 273H and 2841-1 (not shown), but here it is assumed that it is superimposed on 20H. Such a video signal is supplied to the vertical synchronization signal separation circuit 9. The configuration of the vertical synchronization signal separation circuit 9 is well known, and although not shown, it usually includes a low-pass circuit and a waveform shaping circuit. As shown in FIG. 2B, the output pulse signal (2) of the vertical synchronizing signal separation circuit 9 is delayed by about 30 μsec from the initial position of 4H (auxiliary line S). This is due to the characteristics of the above-mentioned low-pass circuit. The pulse signal V obtained here is delayed by the delay circuit 10 and converted into the pulse signal P shown in FIG. 2C. In addition,
The delay circuit 10 is composed of two stages of ordinary mono-multivibrators. The leading edge of the pulse signal P is at the same position as the start of the teletext signal 201-1 in FIG. 2A, or slightly before. Further, the trailing edge of the pulse signal P is at the same position as the end of the teletext signal, or a little later. The pulse signal P obtained here is supplied to the teletext signal presence detection circuit 8. The teletext signal presence detection circuit 8 is also supplied with an input video signal. Although not shown, the teletext signal presence/absence detection circuit 8 is composed of, for example, a gate circuit, a filter circuit, a detection circuit, a gate circuit, etc., and the video signal input to the filter circuit is detected only during the generation period of the pulse signal P. Supplied. Since the filter circuit is configured to filter the clock signal of the teletext signal, the filter circuit filters the clock signal and supplies it to the detection circuit. That is, even if a teletext signal is superimposed on the input video signal, the signal is detected by the detection circuit only when the teletext signal is superimposed on the input video signal. When a signal is detected here, the teletext signal presence detection circuit 8 passes the pulse signal P and supplies it to the clip circuit 3. The clipping circuit 3 is a dynamic clipping circuit that clips the video signal to the pedestal level only when the pulse signal P is input. Here, as shown in the second diagram, the video signal from which the teletext signal has been clipped (removed) is supplied to the video signal recording processing circuit 4 and subjected to processing suitable for supplying it to the magnetic head 5 ( Since this is well known, the explanation will be omitted), and the information is recorded on the magnetic tape 6.

In this way, since the video signal from which the teletext signal has been removed is recorded, the teletext signal is not superimposed on the reproduced video signal during playback, so even if the frequency characteristics or Even if the phase characteristics are poor, or even if noise or dropout occurs in the tape head system, an inaccurate teletext signal will not be displayed on the preview receiver 4IIn.

A similar effect can also be obtained by providing the teletext signal detection circuit 2 and clipping circuit 3 on the reproduction side.

Effects of the Invention According to the present invention, since the teletext signal superimposed on the video signal is removed and recorded during recording, the television receiver receives inaccurate teletext signals regardless of the characteristics of the recording/reproducing system. It has the effect that the signal is not displayed, and its industrial value is extremely large.

[Brief explanation of the drawing]

FIG. 1 is a schematic circuit block diagram showing one embodiment of the present invention;
FIG. 2 is a waveform diagram showing examples of signal waveforms at each part of FIG. 1. 2... Teletext signal detection circuit, 3... Clip circuit, 7... Position detection circuit, 8... Teletext signal presence/absence detection circuit, 9... Vertical synchronization signal separation circuit, 10... Delay circuit agent Yoshihiro Morimoto

Claims (1)

[Claims] 1. A teletext signal detection circuit that detects a teletext signal included in an input video signal and a clip circuit, and when the teletext signal detection circuit detects a teletext signal, . A video signal recording or recording/reproducing device which operates the clipping circuit to record a video signal from which the teletext signal has been removed onto a magnetic recording medium. 2. The teletext signal detection circuit includes a position detection circuit that detects the position where the teletext signal is superimposed, and a character detection circuit that detects whether the teletext signal is superimposed at the position detected by the position detection circuit. 2. The video signal recording or recording/reproducing apparatus according to claim 1, further comprising a signal presence/absence detection circuit.