JPH01196988A - Television signal processing circuit - Google Patents

Abstract

PURPOSE:To prevent disturbance of a video image of a television signal obtained through processing by replacing a synchronizing signal mixed in a video signal into a prescribed level signal if the synchronizing signal is mixed in the video signal corresponding to an effective pattern written in the video memory. CONSTITUTION:If the synchronizing signal component is mixed in video signals SY, SC for effective pattern written in a video memory 4, the synchronizing signal component caused in a 2nd video signal is detected and replaced into a prescribed level of signal component by television signal processing sections 21, 22. Then if the video signals SY, SC of the effective pattern are mixed with the synchronizing signal component by the sections 21, 22, the synchronizing signal component caused in the 2nd video signal is detected and the synchronizing signal component is replaced into the signal component of a prescribed level. Thus, the occurrence of large disturbance deforming the picture is prevented in the poststage devices.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a television signal processing circuit, and is suitable for application to, for example, a television signal processing circuit that converts the format of television signals.

B. Summary of the Invention The present invention eliminates disturbances in images on a monitor screen by replacing a television signal output from a field memory that is at a synchronization signal level with a predetermined level in a television signal processing circuit. You can prevent this from happening.

C. PRIOR TECHNOLOGY A conventional television signal processing circuit obtains a converted television signal by once writing a signal portion of the television signal corresponding to an effective screen portion into a field memory and then reading it out. For example, it is used in standard television signal converters, noise reduction devices, time axis correction devices, etc.

For example, NTSC recorded on a video tape recorder
A standard television signal converter that reproduces a PAL television signal, converts it to a PAL television signal, and outputs the NTSC video signal corresponding to an effective screen for l fields written in the field memory. When reading, by performing interpolation processing as necessary, the number of scanning lines, number of fields, etc. are adapted to the PAL system to obtain a PAL system video signal, and by adding a synchronization signal to this video signal. , to obtain a PAL television signal.

That is, as shown in FIG.
) 2 is converted into a digital luminance signal Sv and a chroma signal Sc in an analog/digital conversion circuit 3, and then stored in a field memory 4.
At the same time, the luminance signal Sv and the chroma signal S are converted into effective screen video signals by the address signal S1 formed in the write control circuit 6 based on the horizontal and vertical synchronization signals H5, Nc and VSYNC obtained in the synchronization separation circuit 5. It is written into the field memory 4 as .

The video signal thus written in the field memory 4 is read out by the address signal S3 sent from the readout control circuit 7 in synchronization with the synchronization signal S2 of the PAL synchronization signal generation circuit 8, and is then read out by the readout control circuit 7 to generate the luminance signal S□ and the chroma signal SCI.
The signal is sent to the interpolation circuit 9 as a signal.

The interpolation circuit 9 interpolates the video signal S4 having the number of scanning lines and fields of the PAL system based on the read luminance signal SYI and the chroma signal SCI, and sends this video signal S4 to the addition circuit 10. Send. The adder circuit 10 adds the PAL synchronizing signal S sent from the PAL synchronizing signal generating circuit 8 to the video signal S4 to form a PAL digital television signal S6, which is converted into a PAL digital television signal S6 by the digital/analog converting circuit 11. The system television signal S%IO is transmitted.

In the case of FIG. 3, the synchronization signal S of the PAL synchronization signal generation circuit 8
, the NTSC reference signal forming circuit 12 generates a reference signal S, and the reference signal S s generates V
By applying servo to TR2, the time axis of the NTSC reproduced television signal SVI can be aligned with the PAL television signal SVO, thus facilitating overtaking control in the field memory 4.

D Problems to be Solved by the Invention By the way, in the television signal processing circuit 1 having the configuration shown in FIG. Excess/deficiency (for reading, write control circuit 6
And in the read control circuit 7, for example, P L L (p
It is necessary to control the timing of the address signals SI and S3 with high precision using a (has 1 locked 1 loop) circuit, and to servo control the VTR 2 using the reference signal S6.

However, in practice, the operations of the PLL circuit and the servo circuit may be disturbed, and in this case, there is a possibility that the horizontal synchronization signal and/or the vertical synchronization signal may be mixed into the video signal written to the field memory 4.

In this way, the PAL television signal SV, which contains the video signal mixed with the horizontal synchronization signal and the vertical synchronization signal,
When sent as O, the subsequent device (for example, a monitor) responds to the vertical synchronization signal in the television signal for one field and the horizontal synchronization signal within one horizontal period, so the screen is vertically There are problems that result in violently distorted images, such as violent vertical movement or horizontal movement of images.

The present invention has been made in consideration of the above points, and it is an object of the present invention to propose a television signal processing circuit that can effectively avoid the possibility that the synchronization of images will be disrupted in a subsequent device.

E Means for Solving the Problem In order to solve this problem, in the present invention, the video signal for the effective screen of the first television signal SVI including the first video signal and the first synchronization signal is , is once written into the video memory 4 in synchronization with the first synchronization signal, and then the second
A second video signal is obtained by reading out the television signal SVO at the timing of the second synchronization signal, and a second television signal SVO including the second video signal and the second synchronization signal is transmitted. In the television signal processing circuit 20 configured as above, when a synchronization signal component is mixed into the video signals Sy and Sc for the effective screen to be written to the video memory 4, the synchronization signal component occurring in the second video signal is detected. It is provided with television signal processing units 21 and 22 that replace the synchronization signal component with a signal component of a predetermined level.

When a synchronizing signal component is mixed into the video signals Sv and Sc for the effective screen by the F-action television signal processing units 21 and 22, the synchronizing signal component occurring in the second video signal is detected and the synchronizing signal component is adjusted to a predetermined level. Since it can be replaced with a signal component, it is possible to prevent large disturbances that would cause the image to collapse in the subsequent device.

G example An embodiment of the present invention will be described in detail below with reference to the drawings.

In FIG. 1, in which parts corresponding to those in FIG. PAL after receiving chroma signal Set
A brightness signal S7□ and a chroma signal SCZ obtained by interpolating the television signal of the system are generated, and the brightness signal SY
2 is input to the synchronization signal detection circuit 21, and is also supplied to the addition circuit 23 as an output luminance signal SY2 via the signal input terminal a and signal output terminal C of the switching circuit 22, and the chroma signal Scz is input to the time adjustment circuit 24. Output brightness signal S via
Adding circuit 2 as output chroma signal SC3 synchronized with Y3
Supply to 3. The sum signal S11 of the output luminance signal SY3 and the output chroma signal SC3 thus obtained in the adder circuit 23 is given to the adder circuit 10 as a PAL video signal.

The synchronization signal detection circuit 21 sets a threshold to detect a synchronization signal level signal at a signal level lower than the pedestal level when the luminance signals S and t change to the signal levels of the vertical synchronization signal and the horizontal synchronization signal. By setting , a switching control signal S0 is applied to the switching circuit 22 to switch to the signal input terminal side.

At this time, the switching circuit 22 outputs a correction signal S having a predetermined voltage level (for example, pedestal level) from the signal input terminal.
The COR is supplied to the adder circuit 23 as the output luminance signal SVX.

(The synchronizing signal detection circuit 21 and the switching circuit 22 constitute a television signal processing section.

In the above configuration, for example, due to a servo loop from the NTSC reference signal forming circuit 11 to the NTSCVTR 2, or a disturbance in the operation of the PLL circuits of the write control circuit 6 and read control circuit 7, as shown in FIG. 2(A), When a vertical synchronization signal or a horizontal synchronization signal (for example, a vertical synchronization signal) is mixed into the video signal within the effective screen of the luminance signal SV□ sent from the interpolation circuit 9, this is The synchronizing signal detection circuit 21 detects it and sends a switching control signal SD to the switching circuit 22.

At this time, the switching circuit 22, as shown in FIG. 2(C),
Outputs the correction signal S COR having the pedestal level during the period of the written vertical synchronization signal The brightness signal SY3
By sending the signal as a black level video signal, processing equivalent to replacing the mixed vertical synchronization signal with a so-called black level video signal is executed. By replacing the synchronization signal level signal with a pedestal level signal, it is possible to minimize the disturbance of the image on the screen.

According to the above configuration, when a vertical or horizontal synchronizing signal is mistakenly mixed into the signal for an effective screen of the video signal in the field memory 5, the converted signal is replaced by a video signal of a predetermined level. It is possible to prevent a non-regular and unnecessary synchronization signal from being mixed into the PAL television signal Svo, and thus it is possible to prevent large disturbances that may distort images in a subsequent device such as a monitor.

In the above-described embodiment, a television signal processing circuit was described which is configured to obtain a PAL television signal from an NTSC television signal, but the present invention is not limited to this, and is applicable to converting from a PAL television signal to an NTSC television signal. It may also be applied to things that

Further, in the above-described embodiments, a case has been described in which a television signal is converted, but the present invention is not limited to this, and may be applied to a noise reduction device, a time axis correction device, etc.

Further, in the above-described embodiment, the signal of the effective picture portion of the television signal is written in the field memory, but the present invention is not limited to this, and the signal can be written in a video memory such as a frame memory. Good too.

Furthermore, in the above-described embodiment, a case was described in which a signal at a synchronization signal level of a video signal is replaced with a signal at a pedestal level; however, the present invention is not limited to this, and a signal level corresponding to the video signal is replaced. You can.

H Effects of the Invention As described above, according to the present invention, if a synchronization signal is mixed in the video signal corresponding to the effective screen written in the video memory, this is replaced with a signal of a predetermined level. Accordingly, it is possible to prevent the processed television signal from including signal components that may cause image disturbance.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a television signal processing circuit according to an embodiment of the present invention, FIG. 2 is a signal waveform diagram processed in each part of the television signal processing circuit, and FIG. 3 is a conventional television signal processing circuit. FIG. 2 is a block diagram showing a processing circuit. 1.20... Television signal processing circuit, 2.
...VTR14...Field memory,
9... Interpolation circuit, 21... Synchronous signal detection circuit, 22... Switching circuit, 24...
time adjustment circuit.

Claims (1)

[Scope of Claims] A video signal corresponding to an effective screen of a first television signal including a first video signal and a first synchronization signal is transmitted to the first video signal.
Once written to the video memory in synchronization with the synchronization signal of
A second video signal is obtained by reading out the second television signal at the timing of a second synchronization signal, and the second video signal includes the second video signal and the second synchronization signal.
In the television signal processing circuit configured to send out a television signal of 1, when a synchronization signal component is mixed into the video signal for the effective screen to be written to the video memory, the synchronization that occurs in the second video signal. A television signal processing circuit comprising a television signal processing section that detects a signal component and replaces the synchronizing signal component with a signal component of a predetermined level.