JPH0526869Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a video signal reproducing device such as a video disk player, a video tape recorder, etc.

[Summary of the idea]

The present invention provides a video signal reproducing device that includes a detection circuit that detects a vertical blanking interval of a reproduced video signal, and a code signal included in the vertical blanking interval of the video signal in response to a detection signal of the detection circuit. a removal circuit; a switch means for selectively outputting either the video signal from which the code signal is removed by the removal circuit or the video signal from which the code signal is not removed; and control means for controlling the switch means to select the video signal from which the code signal has been removed, and output the video signal from which the code signal has been removed when the vertical synchronization signal of the video signal is unstable. , the code signal does not appear on the screen, allowing a high-quality image to be obtained.

[Conventional technology]

For example, in video disc players, etc.
The pickup is moved in the radial direction of the disk at a faster speed than during normal playback, making it possible to scan a desired screen while viewing the playback image. In addition, code signals containing various data such as frame numbers, audio multiplex codes, character multiplex codes, etc. are inserted in the vertical retrace section of the video signal, and can be used to search for a screen with a predetermined frame number, or to play still images. , various special reproductions are now possible.

[Problem that the invention attempts to solve]

By the way, when a conventional device performs a scan operation, especially when the disk is a CLV (constant linear velocity) disk, a vertical synchronization signal cannot be stably obtained, so a vertical retrace interval that normally does not appear on the screen appears. appear above. Since a code signal, which is a repetitive pulse of a white level and a black level, is recorded in the vertical retrace section, this code signal appears as a horizontal dotted line on the screen, which is an eyesore. In particular, for example, the present applicant proposed the following (Utility Application No. 59-115082)
When the screen is locked to a predetermined color and scanned, as in No. 1, this noise is particularly noticeable, and the commercial value of the operation is significantly impaired.

[Means for solving problems]

FIG. 1 is a block diagram of a video signal reproducing apparatus according to the present invention. In the figure, numeral 1 denotes a demodulation circuit that demodulates a video signal input as an RF signal. The output signal of the demodulation circuit 1 is supplied to one input terminal of a switch 2, and is also supplied to a removal circuit 3 and a detection circuit 4. The detection circuit 4 detects a vertical blanking interval from the output signal of the demodulation circuit 1 and supplies the detection signal to the removal circuit 3.
The removal circuit 3 removes various code signals included in the vertical retrace interval from the output signal of the demodulation circuit 1 in response to the detection signal supplied from the detection circuit 4, and sends the signal to the other input terminal of the switch 2. Output. 5 is a control circuit that controls switching of switch 2;
A delay circuit 6 that delays the trailing edge of the input high-level scan signal and outputs the delayed signal is installed.
It has an AND gate 7 to which the CLV signal, which is at a high level when it is a CLV disk, is input to one side, and the output of the delay circuit 6 is input to the other side.

[Effect]

The effect will now be explained. If it is a CAV (constant rotation speed) disk that is currently installed and being played, the CLV signal will be at a low level, and the output of the AND gate 7 will be at a low level. Therefore, the switch 2 is switched to the upper side in the figure, and the demodulated output signal of the demodulating circuit 1 is output as is. That is, as shown in FIG. 2a, various code signals C ₁ to C ₆ are present in the vertical blanking interval of the video signal output at this time
It is included. Even if a CLV disk is installed and the CLV signal is at a high level, a scan command is not issued and the scan signal is at a low level, since the AND gate 7 is not conductive and operates in the same manner.

Next, the CLV disk is attached, the CLV signal becomes high level, and a scan operation is commanded. When the high level scan signal is input to the delay circuit 6 as shown in FIG. 3a, the AND gate 7 becomes conductive. to output a high-level signal. Therefore, the switch 2 is switched to the removal circuit 3 side.

The detection circuit 4 detects a vertical retrace interval from the output signal of the demodulation circuit 1 as shown in FIG. 2a, and outputs a detection signal corresponding to the vertical retrace interval as shown in FIG. 2b to the removal circuit 3. . While receiving the high level detection signal from the detection circuit 4, the removal circuit 3 removes the code signal by, for example, clamping the signal above the black level of the video signal input from the demodulation circuit 1. When the signal from the detection circuit 4 becomes low level, the removal circuit 3 stops the clamping operation and outputs the input video signal as it is. As a result, the signal outputted from the removal circuit 3 becomes as shown in FIG. 2c, and this video signal is outputted via the switch 2 to a CRT or the like (not shown). Even if the vertical synchronization signal is not stably obtained during scan operation and a vertical retrace interval appears on the screen, the code signal has been removed, so the vertical retrace interval simply appears black, and noise (horizontal dotted line) does not appear.

On the other hand, when the scan operation is stopped and the scan signal (FIG. 3a) returns from a high level to a low level, the output signal of the delay circuit 6 (FIG. 3b) does not return to a low level immediately, but after a predetermined time delay. After that it becomes low level. This delay time approximately corresponds to the time (for example, several 100 ms) required for the vertical deflection to stabilize after the scan operation is stopped. Therefore, immediately after the scanning operation is stopped (when the vertical deflection is not stable), the switch 2 is switched and the video signal containing the code signal is output, thereby preventing it from appearing as noise on the screen.

In the above, the output of the detection circuit 4 is supplied as is to the removal circuit 3, but for example, the output of the fourth detection circuit 4 is
As shown in the figure, it can also be supplied via an AND gate 11. If a high-level burst gate pulse, which is output in synchronization with the timing at which a color burst signal located on the back porch immediately after the horizontal synchronization signal is generated, is supplied to the AND gate 11 via the inverter 12, the color burst signal is generated. The AND gate 11 becomes non-conductive at the timing when the color burst signal is generated, and the color burst signal can be output without being removed. Further, although the control circuit 5 is configured by a delay circuit 6 and an AND gate 7, for example, as shown in FIG.
It is also possible to provide a detection circuit 13 for detecting discontinuous generation of the vertical synchronization signal of the signal outputted by the sensor. Such a detection circuit 13 detects a vertical synchronization signal from the output signal of the demodulation circuit 1, for example,
It can be configured to compare this with a reference signal of a predetermined frequency and monitor the periodicity of its timing. In this way, the code signal can be automatically removed not only during scan operation but also when the vertical synchronization signal is unstable.

〔effect〕

As described above, the present invention provides a video signal reproducing apparatus that includes a detection circuit for detecting a vertical retrace interval of a reproduced video signal, and a code signal included in the vertical retrace interval of the video signal in response to a detection signal of the detection circuit. a switching means for selectively outputting either the video signal from which the code signal has been removed by the removal circuit or the video signal from which the code signal has not been removed; and the vertical synchronization signal of the video signal having regular periodicity. and control means for controlling the switch means to select the video signal from which the code signal has been removed when the vertical synchronization signal of the video signal is not stable. It becomes possible to output the video signal and prevent the code signal from appearing on the screen as noise (white dotted line). Therefore, high-quality images can be obtained, and this method is particularly effective in locking to a predetermined color during scanning.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the video signal reproducing apparatus of the present invention, FIG. 2 is a waveform diagram thereof, FIG. 3 is a timing chart thereof, and FIGS. 4 and 5 are block diagrams of other embodiments. DESCRIPTION OF SYMBOLS 1... Demodulation circuit, 2... Switch, 3... Removal circuit, 4... Detection circuit, 5... Control circuit, 6...
Delay circuit, 13...detection circuit.

Claims (1)

[Scope of utility model registration request] A detection circuit that detects a vertical blanking interval of a reproduced video signal, a removal circuit that removes a code signal included in the vertical blanking interval of the video signal in response to a detection signal of the detection circuit, and the removal circuit. a switch means for selectively outputting either the video signal from which the code signal has been removed or the video signal from which the code signal has not been removed; and control means for controlling the switch means to select the video signal from which the code signal has been removed.