JPH09261686A - Video signal reproduction device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a video signal reproduction device providing a stable and excellent vertical synchronizing signal even in the case of system conversion from the PAL to the NTSC system. SOLUTION: In the video signal reproduction device, a vertical synchronizing signal separator circuit 105 detecting a vertical synchronizing signal frequency of a video signal recorded on a magnetic tape 101 and a pseudo synchronizing signal insert circuit 106 of a reproduction video signal are controlled in response to the result of detection of the vertical synchronizing signal frequency the pseudo vertical synchronizing signal generated based on the vertical synchronizing signal detected by the vertical synchronizing signal frequency detection circuit is inserted to a luminance signal.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to PAL, NTSC.
The present invention relates to a video signal reproducing apparatus suitable for reproducing video signals of different television signal (hereinafter referred to as TV signal) systems.

[0002]

2. Description of the Related Art In the overseas VTR market, recorded tapes, so-called soft tapes, are widely distributed. Therefore, there is a need for a function for converting and reproducing a signal system even when recorded with different signal systems, that is, a system conversion function. Is big. For this reason, VTRs used outside Japan (mainly VH
In the S system), there is a system having a function of recording or reproducing television signals of different TV signal systems such as PAL and NTSC. In this case, from the viewpoint of technical difficulty and cost, the simple method in which the method conversion is performed only for the color signal of the video signal is predominant. A problem in such a simple system is a synchronization system of the internal luminance signal of the video signal.

A conventional video signal reproducing apparatus and its problems will be described below. FIG. 7 is a block diagram of a video signal reproducing apparatus provided with a conventional system conversion system.
In FIG. 7, reference numeral 501 is a color signal input terminal, 502 is a subcarrier frequency input terminal, 503 is a balanced modulation circuit, and 50 is a balanced modulation circuit.
Reference numeral 4 is a doubler circuit that outputs a double frequency of the input signal, 505 is a first switch that switches between the output signal of the balanced modulation circuit 503 and the signal of the input terminal 501, and 506 is a color centered on the subcarrier frequency. A bandpass filter having a signal band as a pass band, 507 is a first phase shift circuit that outputs the phase of the frequency input from the input terminal 502 at +135 [deg], and 508 is a phase of the frequency input from the input terminal 502. Is output at -135 [deg], 509 is a second switch that switches between the output of the first phase shift circuit 507 and the output of the second phase shift circuit, and 510 is the horizontal synchronization frequency. A divide-by-2 circuit for dividing the frequency by 2 is a third switch 512 for switching between the output of the bandpass filter 506 and the output of the first switch 509, and 513 is a burst gate pad representing a burst signal period. Input terminal of the scan (hereinafter referred to as BGP), 514 is an output terminal of the type converted color signal.

The operation of the conventional video signal reproducing apparatus configured as described above will be described below.

First, an NTSC color signal is input from the input terminal 501 and input to the balanced modulation circuit 503.
On the other hand, the sub-carrier frequency input from the input terminal 502 is input to the doubler circuit 504 and to the balanced modulation circuit 503 as a signal of frequency 2fsc (fsc is the sub-carrier frequency), and the frequency of the color signal and the 2fsc signal is input. Multiplication is performed. As a result, a color signal having the same frequency and a phase inversion is obtained as the output signal of the balanced modulation circuit 503. If this is inverted every horizontal period via the first switch 505, the NTSC system can be converted to the PAL system. In the PAL system, the burst signal alternates in phase with + 135 ° / −135 ° in each horizontal synchronizing signal cycle, so that the outputs of the first phase shift circuit 507 and the second phase shift circuit 508 are output from the second switch 509. It is realized by switching with. However, what is called system conversion here is not conversion of the modulation frequency by conversion of the color signal modulation system.

[0006]

However, the above configuration is premised on the system conversion from NTSC to PAL, and at the time of system conversion from PAL to NTSC,
I have a problem with vertical sync on TV monitors. NTS
In the system conversion from C to PAL, since the video signal of 525 scanning lines is input to the TV monitor corresponding to 625 scanning lines, although the entire image shrinks in the vertical direction, almost normal images can be enjoyed. But from PAL to NTSC
In the system conversion, the video signal of 625 scanning lines is input to the TV monitor corresponding to 525 scanning lines, and the extra scanning lines are folded back in the screen, resulting in a very hard-to-see image. are doing.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a video signal reproducing apparatus which is stable in vertical synchronization even when the system is converted from PAL to NTSC.

[0008]

In order to achieve this object, a video signal reproducing apparatus of the present invention is a video signal reproducing apparatus for reproducing a video signal recorded on a medium, the video recorded on the medium. A vertical sync signal frequency detecting means for detecting the vertical sync signal frequency of the signal; and a pseudo sync signal inserting circuit for inserting a pseudo sync signal into the reproduced video signal according to the detection result of the vertical sync signal frequency detecting means. Have

With this configuration, even when the video signal of 625 scanning lines is output to the TV monitor of 525 scanning lines, a good reproduced image without disturbance of vertical synchronization can be obtained.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The invention described in claims 1 to 4 of the present invention relates to a vertical synchronizing signal frequency of a video signal recorded on a medium in a video signal reproducing apparatus for reproducing a video signal recorded on the medium. It is configured to control the pseudo sync signal insertion circuit of the reproduced video signal according to the detection means and the vertical sync signal frequency detection result, and creates based on the vertical sync signal detected by the vertical sync signal frequency detection means. This has the effect of inserting the obtained pseudo vertical synchronization signal into the luminance signal.

An embodiment of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 is a block diagram of a video signal reproducing apparatus showing Embodiment 1 of the present invention. In FIG.
Reference numeral 01 is a magnetic tape which is a medium on which a video signal is recorded, 1
Reference numeral 02 is a magnetic head for recording / reproducing, 103 is a reproducing / amplifying circuit for amplifying a video signal input from the magnetic head 102, 104 is a reproducing signal processing circuit. For example, in a VHS VTR, a luminance signal in the video signal is FM modulation recording is performed, and the color signal is frequency-multiplexed after frequency conversion to the low frequency side of the FM modulated luminance signal. Reference numeral 105 is a vertical sync signal separation circuit that extracts a vertical sync signal from the reproduced luminance signal and outputs a pseudo vertical sync signal, and 106 is a sync signal insertion circuit that inserts the pseudo vertical sync signal into the reproduced luminance signal.

The operation of the video signal reproducing apparatus of the present embodiment configured as described above will be described with reference to FIG.

First, the video signal output from the reproduction signal processing circuit 104 is a signal waveform diagram shown in FIG. 6 (a).
At this time, for example, in the case of a PAL video signal, the vertical synchronizing signal frequency is 50 [Hz] and the cycle is about 20 [mse].
c], in the case of NTSC system, the vertical sync signal frequency is 60
At [Hz], the cycle becomes about 17 [msec]. When outputting a video signal with a vertical sync signal frequency of 50 [Hz] to an NTSC TV monitor, the vertical sync signal separation circuit 1
No. 05 is used to create a pseudo vertical sync signal as shown in FIG. 6B, and the sync signal insertion circuit 106 inserts it into the video signal. Then, the output signal of the sync signal insertion circuit 106 has a vertical sync signal interval of about 17 [msec] due to the pseudo vertical sync signal, as shown in FIG.
It is possible to obtain a stable image with good vertical synchronization even on an SC type TV monitor.

As described above, according to the present embodiment, the vertical synchronizing signal is extracted from the reproduced luminance signal in the video signal reproducing circuit, the pseudo vertical synchronizing signal is synthesized based on the extracted vertical synchronizing signal, and the reproduced signal is reproduced. By being configured to be inserted in the luminance signal, it is possible to provide stable and good video in vertical synchronization even when the system conversion from PAL to NTSC is performed.

(Second Embodiment) FIG. 2 is a block diagram of a video signal reproducing circuit according to a second embodiment of the present invention. In FIG. 2, 201 is an AND gate that performs logical operation with the output of the vertical synchronizing signal separation circuit 105 and a switching signal input from the outside, 202 is an input terminal of the switching signal, and other configurations are as follows.
Since the configuration is the same as that of the first embodiment shown in FIG. 1, description thereof will be omitted. The difference from the configuration of FIG. 1 is that the insertion of the pseudo vertical synchronizing signal to be inserted in the luminance signal
It is possible to control by a switching signal input from 02.

The operation of the second embodiment of the present invention configured as described above will be described below.

First, when a TV monitor with 525 scanning lines is connected to the output of the video signal reproducing circuit and the video signal reproducing device reproduces video signals with 625 scanning lines as in the PAL system, A “Hi” switching signal is input to the input terminal 202. Then, the AND circuit 201 inserts the pseudo vertical sync signal by the sync signal insertion circuit 106, and a reproduced video image of good vertical sync can be obtained.

On the other hand, when the connected TV monitor is a system of 625 scanning lines, or when the reproduced video signal is a video signal of a 525 system such as the NTSC system, the input terminal 202 is connected. Input a switching signal of "Lo". Then, the AND circuit 201 does not insert the pseudo vertical sync signal by the sync signal insertion circuit 106, and a normal reproduced image can be obtained.

As described above, according to the present embodiment, the insertion of the pseudo vertical synchronizing signal to be inserted into the luminance signal is performed by the input terminal 2.
Since it can be controlled by the switching signal input from 02, it is possible to always obtain a reproduced video of good vertical synchronization.

(Third Embodiment) FIG. 3 is a block diagram of a video signal reproducing circuit according to a third embodiment of the present invention. In FIG. 3, reference numeral 301 denotes a color signal modulation method from NTSC to PAL.
Alternatively, the color signal system conversion circuit for system conversion from PAL to NTSC is the same as the configuration of the first embodiment shown in FIG. 1, and the description thereof is omitted. The difference from the configuration of FIG. 1 is that a color signal system conversion circuit 301 is provided, the color signal modulation system is converted into a modulation system suitable for a TV monitor, and a color video signal can be reproduced.

The operation of the third embodiment of the present invention configured as described above will be described below.

First, in the case where a TV monitor whose color system is NTSC is connected to the output of the video signal reproducing circuit,
When reproducing a color video signal of the PAL modulation system in the video signal reproducing device, the color video signal can be reproduced by converting the modulation system of the color signal by the color signal system conversion circuit 301, and reproduction with good vertical synchronization is also possible. You can get a video.

(Embodiment 4) FIG. 4 is a block diagram showing the structure of a video signal reproducing apparatus showing the structure of Embodiment 4 of the present invention. In FIG. 4, the same components as those in the third embodiment are designated by the same reference numerals and the description thereof will be omitted. 202 is a switching signal input terminal, and 201 is an AND circuit that outputs an H signal when both the output of the vertical synchronizing signal separation circuit 105 or the switching signal output from the switching signal input terminal 202 is input.

As described above, according to this embodiment, it is possible to reproduce a color video signal and obtain a reproduced video with good vertical synchronization.

(Fifth Embodiment) FIG. 5 is a block diagram of a video signal reproducing circuit according to a fourth embodiment of the present invention. In FIG. 5, reference numeral 601 is a detection circuit for detecting the TV signal system of the reproduced video signal, and 602 is an AND gate for logically operating the output signal of the detection circuit 601 and the switching signal input from the input terminal 202. The configuration is similar to that of the fourth embodiment shown in FIG. The difference from the configuration of FIG. 4 is that the TV signal system reproduced by the detection circuit 601 is automatically detected and the TV connected to the output of the video signal reproduction apparatus.
The point is that the pseudo sync signal insertion is controlled according to the monitor.

The operation of the fourth embodiment of the present invention configured as described above will be described below.

First, in the case where a TV monitor whose color system is NTSC is connected to the output of the video signal reproducing circuit,
When reproducing the color video signal of the PAL modulation system in the video signal reproducing device, the detection circuit 601 detects the TV signal system and the TV monitor system connected by the switching signal input from the input terminal 202. Automatically controls the insertion of the pseudo sync signal in the sync signal insertion circuit.

As described above, according to the present embodiment, it is possible to obtain a reproduced image with good vertical synchronization.

Appropriate means for detecting the TV signal system are (1) discrimination based on the frequency of the vertical synchronizing signal, and (2) VH.
It is possible to use the control signal (3) color signal modulation system recorded on the tape in the S system VTR.

[0030]

INDUSTRIAL APPLICABILITY As described above, the present invention is applicable from PAL to NT.
An excellent effect that stable vertical synchronization and a good image can be obtained at the time of system conversion to SC is obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of a video signal reproducing device according to a first embodiment of the present invention.

FIG. 2 is a block diagram of a video signal reproducing device according to a second embodiment of the present invention.

FIG. 3 is a block diagram of a video signal reproducing device according to a third embodiment of the present invention.

FIG. 4 is a block diagram of a video signal reproducing device according to a fourth embodiment of the present invention.

FIG. 5 is a block diagram of a video signal reproducing device according to a fifth embodiment of the present invention.

FIG. 6 is a signal waveform diagram of a video signal reproducing device according to a second embodiment of the present invention.

FIG. 7 is a block diagram of a conventional video signal reproducing device.

[Explanation of symbols]

 101 magnetic tape 102 magnetic head 103 reproduction amplification circuit 104 reproduction signal processing circuit 105 vertical synchronization signal separation circuit 106 synchronization signal insertion circuit 201 AND gate 202 switching signal input terminal

Claims (4)

[Claims] 1. A video signal reproducing apparatus for reproducing a video signal recorded on a medium, comprising: vertical synchronization signal frequency detecting means for detecting a vertical synchronization signal frequency of the video signal recorded on the medium; and the vertical synchronization. And a pseudo sync signal insertion circuit for inserting a pseudo sync signal into a reproduced video signal according to the detection result of the signal frequency detection means. 2. A vertical synchronization signal frequency detection result and a switching circuit inputted from the outside are provided with a logic circuit, and a pseudo synchronization signal insertion circuit is controlled by the output of the logic circuit. The video signal reproducing device according to claim 1. 3. The image according to claim 1, further comprising a system conversion circuit for converting a color system of the video signal, and the system conversion circuit is configured to be controlled according to the switching signal. Signal reproduction device. 4. A video signal reproducing apparatus comprising a detection circuit for detecting a TV signal system of a video signal, and configured to control a system conversion circuit according to an output of the detection circuit and the switching signal. .