JPH0194788A - Special image device - Google Patents

Abstract

PURPOSE:To display a small display screen without shifting the hue by taking correlation with the polarity of a chrominance signal and executing sampling when a video signal of a system where the polarity of a video chrominance signal is changed and transmitted at every H line is displayed as the small display screen. CONSTITUTION:The chrominance signal is inputted to a chrominance signal polarity discrimination circuit 31 and the output of that is inputted to a sampling control gate 33. When a small screen which is 1/n (n: even number) of the whole screen is displayed, the output of the circuit 31 is inputted to a sampling control gate 34 by switching a change-over switch 32 to a negative side and a chrominance signal sampling signal 14 is controlled. Besides, when a small screen which is 1/n (n: odd number) of the whole screen is displayed, the chrominance signal sampling signal 14 is not controlled by the output of the circuit 31 by switching the change-over switch 32 to a positive side. Thus, the hue shift of the small display screen of one even-number-th is fixed and the small screen of one odd-number-th can be displayed without shifting the hue.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a special image device, and in particular, displays a small screen by cutting out one screen of information every one horizontal scanning period (hereinafter referred to as H line). The present invention relates to a circuit that realizes a method of thinning H lines suitable for a special image device having such functions.

[Conventional technology]

Conventionally, a small screen of video signals created by a special NTSC image device was published in TV Technology, August 1986 issue, pages 39 to 4.
1 page “Picture-in-picture circuit”, same 1987
As stated in "12-screen multi-screen function" on pages 27 to 30 of the August issue, 8H of information on one screen
A small screen is displayed by writing each line to memory at intervals. FIG. 2 shows a block diagram of an NTSC system small screen display circuit. A video signal input from a video signal input terminal 1 is separated into a brightness signal and a color signal by a brightness signal extraction filter 2 and a color signal extraction filter 4. The luminance signal is input to an analog-to-digital signal converter (hereinafter referred to as an A/D conversion circuit) 3#ζ, sampled by a sampling signal 131 from the frequency dividing circuit 15, converted to a digital signal, and written into the memory 11. Further, the color signal is input to the color signal decoder 5 and becomes a BY signal.

The demodulated R-Y signal is input to each color signal A/D conversion circuit 6.7, sampled by the color signal sampling signal 14, converted to a digital signal, and written into the memory 11.

In order to eliminate the hue shift of the video signal, a circuit that displays a small screen of the video signal such as PAL system or SECAM system that changes the phase of the burst signal every 1H line, that is, changes the polarity of the color signal every 1H line, is used. It is shown in Figure 3. Compared to FIG. 2, the adder circuit 22. Subtraction circuit 23. IH
A new delay line 218 is provided. The chrominance signal is inputted to an addition circuit 22 and a subtraction circuit 23, added to and subtracted from the output of the 1H delay line 21, and inputted to the chrominance signal decoder 5. As described in "Color TV System" on pages 70 to 75 of Video Recording Technology (Sanpo Publishing), 1 is used to process color signals.
H delay line is required.

[Problems that the invention attempts to solve]

The above conventional technology is expensive because it requires a 1H delay line.
Further, there is a problem in that adjustment, trimming, etc. are required to obtain precision in the amount of delay. Furthermore, if sampling is performed without using a 1H delay line, the hue of the small screen will shift if the color signal is out of phase with the burst signal. In particular, when using multi-strobe (an operation in which video information is displayed on successive small screens and displayed at - degrees), there is a problem in that the directions of hue shifts on all the small screens do not match, resulting in a screen that is extremely difficult to view.

An object of the present invention is to eliminate hue shift without using the 1H delay i, or to display a small screen that is fixed in one direction and easy to view.

[Means for solving problems]

The above purpose is achieved by correlating the timing of thinning out information on one screen with the polarity of the video color signal, and sampling so that the polarity is alternately reversed, or sampling so that only the same polarity is used. , achieved.

[Effect]

FIG. 5 shows a timing chart of color signal polarity and sampling. For example, when displaying a small screen of 1/5 of an odd number, such as 1/5 size, 1H line out of 3H lines is sampled, so the polarity of the color signal is alternately inverted every sampling. Therefore, a small screen with no hue shift is displayed. However, in the case of a small screen that is an even number, such as a quarter size, depending on the state at which the sampling operation is started, the polarity of the color signal within one small screen may be only ■ or only O, and the hue may vary. C) Therefore, a polarity discrimination circuit is provided, and sampling is controlled by the output of the circuit, and by sampling only the same polarity, the hue shift is fixed in one direction. Further, by changing the sampling timing and performing sampling such that the polarity is alternately inverted, hue shift can be eliminated.

〔Example〕

The first embodiment of the present invention will be described below using the fourth factor. Compared to FIG. 2, the color signal polarity determination circuit 31, changeover switch 32. A new 34% sampling control gate 35 will be installed. The color signal is input to the color signal polarity determination circuit 51, and its output is input to the sunblicida control gate 351. To display a small screen of even numbers, press switch 3.
28, the output of the color signal polarity determination circuit 51 is input to the sampling control gate 54 to control the color signal sampling signal 148. When displaying a small screen of 1/odd number, the changeover switch 528 is turned to the positive position so that the color signal sampling signal 14 is not controlled by the output of the color signal polarity determination circuit 31.

According to this embodiment, it is possible to fix the hue shift on the even-numbered small screen, and to display a screen without hue shift on the odd-numbered small screen.

Next, the embodiment of wc2 of the present invention is described in iii! This will be explained using Figure 1. A block diagram is shown in FIG. 1(a). Compared to FIG. 2, the color signal sampling signal 14 generated by the timing circuit 12 is different.

FIG. 1(b) shows a timing chart of color signal polarity and sampling. Sampling when displaying a small screen of 1/odd number is the same as in the conventional example.

Sampling in the case of a small screen of 1/4 of an even number such as 1/4 size is changed from timing (1) to timing (2). That is, in sampling A, polarity 2 is sampled, and in sampling B', polarity O is sampled, and thereafter, the timing circuit 12 is changed so that the polarity is alternately inverted every sampling.

According to this embodiment, 1/1 of an even number. f3'/J
% screen has the effect of displaying a screen without hue shift.

〔Effect of the invention〕

According to the present invention, when displaying a video signal of a method such as PAL or SECAM in which the polarity of the video color signal is changed and transmitted for each H line on a small screen, sampling can be performed by correlating with the polarity of the color signal. So expensive 1H delay fj!
8. It has the effect of displaying an easy-to-see small screen without hue shift or fixed in one direction without using it.

[Brief explanation of the drawing]

FIGS. 1(a) and 1(b) show 10 of the second embodiment of the present invention.
Figures 2 and 5 are block diagrams of the conventional example, Figure 4 is a block diagram of the first embodiment of the present invention, and Figure 5 is a timing chart of color signal polarity and sampling. It is a diagram. 1...Ei 1#! Signal power 4... Color signal extraction filter 5... Color signal decoder 6.7... A/D conversion circuit 12... Timing circuit 14... Color (K number sampling signal 15... minutes) Circulating circuit 31... Color signal polarity discrimination circuit 32... Changeover switch 55.54... Sampling control gate Fig. 1 (b
)

Claims (1)

[Claims] 1. Digital memory writing in a special image device having a digital memory, an analog-to-digital signal converter, and a timing circuit for a video signal that is transmitted by changing the polarity of the video color signal every horizontal scanning period. 1. A special image device comprising a circuit that controls a permission signal by a timing circuit and writes color signals in a memory at intervals so that the polarities of the color signals are alternately inverted. 2. In the special imaging device according to claim 1, a color signal polarity discriminator is provided, and the digital memory write enable signal is controlled using the signal obtained from the polarity discriminator and the timing circuit, so that the color signal is A special image device characterized by comprising a circuit that selectively writes only one polarity into a memory.