JPH03158091A - Video signal processor unit - Google Patents

Abstract

PURPOSE:To prevent appearance of noise at left end and an upper end of a screen by holding a color signal obtained from a matrix circuit to a black level forcibly for a period longer than the horizontal blanking period and the vertical blanking period of the color signal. CONSTITUTION:A 1st pulse width revision circuit 6 making a pulse width of a signal HBLK fed to a matrix circuit 4 narrow and a 2nd pulse width revision circuit 7 widening the pulse width of a signal VBLK are provided. Then the pulse width of the signal HBLK is made narrow and the noise generating period is contained in the horizontal blanking period. Moreover, furthermore, the analog switch is controlled to select a black level signal for the horizontal blanking period and the output pulse period of the 2nd pulse width revision circuit 7. Thus, the signal level is forcibly set to the black level for the periods and noise at left end and an upper end of the screen is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a video signal processing device that is used in television receivers, monitor devices, etc. and includes a matrix circuit and the like for obtaining predetermined color signals.

[Conventional technology]

FIG. 3 is a block diagram showing a conventional video signal processing device. In the figure, 1 is an input terminal for a video signal, and 2 is a demodulator for demodulating a luminance signal Y and color difference signals R-Y, B-Y from the video signal. 3 is a synchronization signal processing circuit that generates a horizontal blanking signal HBLK and a vertical blanking signal VBLK based on the synchronization signal; 4 is a synchronization signal processing circuit that separates the synchronization signal from the signals Y, R-Y, B-Y; , H
Predetermined color signals R, G, B based on BLK and VBLK
5 is a matrix circuit for demodulating the above color signals R, G, B.
Amplify and output color signal Rout * Gout , Bo
This is an amplifier circuit consisting of ut.

Next, the operation will be explained.

The video signal input from the input terminal 1 is processed by the signal processing circuit 2, thereby producing signals Y and RY.

B-Y is demodulated and the horizontal synchronization signal is separated. The synchronization signal processing circuit 3 outputs the signals HBLK and VBLK shown in FIG.

Create color signals R, G, and B shown in FIG. 4 (cl) based on R-Y, B-Y, HBLK, VBLK, etc.
These color signals R, G, and B are passed through the amplifier circuit 5 to the color signal Ro.
It is output as ut j Gout l Bout. Note that the color signal shown in FIG. 4 (CIK) indicates one of R, G, and B.

In this Fig. 4 fcl, when looking at the level of the horizontal blanking period indicated by the nox width of the signal HBLK, it rises to a level higher than the black level at approximately the center, and a level higher than this black level indicates the horizontal blanking period. It continues to the beginning of the video period beyond. Therefore, as shown in FIG. 2D, noise appears from the center of the horizontal blanking period to the beginning of the video period.

Also, when looking at the vertical blanking period indicated by the pulse width of the signal VBLK, the same phenomenon as above appears for each horizontal blanking period, and as a result, as shown in dl in the same figure, the first vertical blanking period Noise appears that continues from approximately the center of the horizontal blanking period to a point slightly beyond this incense stone blanking period.

The above phenomenon is experimentally observed when an IC for matrix circuit 4 is used in EDTV (high-definition television).

[Problem to be solved by the invention]

Since the conventional video signal processing circuit is configured as described above, noise as shown in FIG. , there was a problem in that noise appeared on the left and top edges of the screen.

This invention was made in order to solve the above five problems, and includes (a) a video signal that can remove noise at the left end and upper end of the screen that occurs when using an IC for IJx circuits; The purpose is to obtain a processing device.

[Means to solve the problem]

The video signal processing device according to the present invention includes a first pulse width changing circuit that narrows the pulse width of the signal HBLK applied to the matrix circuit, and a second pulse width changing circuit that widens the pulse width of the signal VBLK.
an analog switch for selecting each color signal or a black level signal, the analog switch being controlled by the signal HBLK and the output pulse of the second pulse width changing circuit; It is equipped with a control circuit.

[For production]

In the video signal processing device according to the present invention, by narrowing the pulse width of the signal HBLK, the noise generation period is kept within the horizontal blanking period.

Then, by controlling the analog switch to select the black level signal during the horizontal blanking period and the period of the output pulse of the second pulse width changing circuit, these periods are forced to the black level. Since the image is retained, noise at the left and top edges of the screen is removed.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In FIGS. 3 and 2, parts corresponding to those in FIGS. 3 and 4 are given the same reference numerals, and their explanations will be omitted.

In FIG. 1, reference numeral 6 denotes a first pulse width changing circuit, which is composed of a monomulti, etc., which generates a pulse HBLKo with a narrower pulse width of the signal HBLK, and converts the matrix circuit 4
Add to. 7 is a second pulse width changing circuit that generates a pulse VBLKo by widening the pulse width of the above signal
It is composed of a latch circuit that holds the H period. A black level setting circuit 8 outputs a predetermined black level signal BK obtained by dividing the power supply voltage by resistance. Reference numeral 9 designates an analog switch consisting of three switches, each of which has signals R, G, and B applied to its contact point a, and the black level signal BK applied to its contact point a. 10 is an analog switch control circuit for obtaining a control signal V for switching the analog switch 9, and the signal VBLK
and the above pulse VBLKO are added to the OR gate 10.
a, an OR game to which the output of this OR gate 10a and the signal HBLK are applied) 10b, and this OR gate 10b
The transistor 10C is controlled by the output signal U of the transistor 10C and outputs the control signal V.

Next, the operation will be explained.

The first pulse width changing circuit 6 generates a signal T (pulse HBLK shown in FIG. 2 fbl with a narrowed pulse width of BLK).

Create and add to matrix circuit 4. By narrowing this pulse width, the color signals R, G, and B obtained from the matrix circuit 4 become as shown in FIG.
However, this period above the black level ends within the horizontal blanking period, and therefore the noise does not continue into the video period.

On the other hand, the pulse V obtained from the second pulse width changing circuit 7
BLKo and signal VBLK are applied to OR gate 10a, and its output and signal IBLK are applied to OR gate 10b.
By being added to, from this or gate 10b,
The output signal shown in FIG. 2 is obtained. As shown in the figure, this output signal U has a pulse UH with a pulse width equal to the horizontal blanking period, a pulse UH with a pulse width that includes the vertical blanking period, and a period approximately 2H longer from the end of the vertical blanking period.
It consists of v. Therefore, by controlling the transistor 10C using this output signal U, a control signal V corresponding to this output signal U is obtained.

By switching the analog switch 9 from contact a to contact in a period corresponding to the pulses UH and Uv of this control signal V, the analog switch 9 changes the pulses UH and Uv as shown in FIG. A color signal whose period is forcibly maintained at the black level is obtained. As a result, noise as shown in FIG. 4 (dl) is removed, and no noise appears on the left and upper edges of the screen.

〔Effect of the invention〕

As described above, according to the present invention, the pulse width of the horizontal blanking signal applied to the matrix circuit is narrowed, and the horizontal blanking period and vertical blanking period of the color signal obtained from the matrix circuit are Since the black level is forcibly held for a longer period of time, the noise generated in conventional matrix circuit ICs is effectively removed and noise is prevented from appearing on the left and upper edges of the screen. The effect that can be obtained can be obtained.

[Brief explanation of the drawing]

Part 1 is a block diagram showing a video signal processing device according to an embodiment of the present invention, FIG. 2 is a timing chart showing the operation of the same device, FIG. 3 is a block diagram showing a conventional video signal processing device, and Part 4 is a block diagram showing a video signal processing device according to an embodiment of the present invention. The figure is a timing chart showing the operation of the device. 4 is a matrix circuit, 6 is a first pulse width changing circuit, 7
is the second pulse width changing circuit, 9 is the analog switch, 1
0 is an analog switch control circuit, HBLK is a horizontal blanking signal, VBLK is a vertical blanking signal, HBLKo and VBLKo are pulses, BK is a black level signal, R, G. B is a color signal, Y is a luminance signal, R-Y and B-Y are color difference signals, and ■ is a control signal. In addition, the same symbols in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] a first pulse width changing circuit that narrows the pulse width of the horizontal blanking signal; and a plurality of color signals based on the output pulse of the first pulse width changing circuit, the vertical blanking signal, the luminance signal, and the color difference signal. The matrix circuit to be created,
an analog switch for selecting a plurality of color signals obtained from the matrix circuit or a predetermined black level signal; a second pulse width changing circuit for widening the pulse width of the vertical blanking signal; and a second pulse width changing circuit for widening the pulse width of the vertical blanking signal. A video signal processing device comprising: an analog switch control circuit that controls the analog switch to select the black level signal during the output pulse period of the changing circuit and the horizontal blanking signal period.