JPS62114393A - Color television signal processor - Google Patents

Abstract

PURPOSE:To reduce a cross color without deteriorating a resolution by raising the characteristics of an enhancer circuit and a trap circuit in an encoder at a transmission side in a color TV system which multiplexes and transmits a chrominance signal and a luminance signal. CONSTITUTION:In a trap circuit [figure (b)], a delay circuit 51(1H) is a delay line of 1H period, and the delay circuit 51(2tau) represents a delay line of 1/(2fs) assuming that a subcarrier frequency is (f). And the circuit 51, a counter 52, and an adder 53 are combined and constitute a filter, and the output signal of the adder 53 at the front of the counter 52 forms a pole at the center of an area 21, then being the maximum. By subtracting the signal from an original luminance signal with the counter 52 and the next adder 53, a luminance signal component at the area 21 can be eliminated. And when an impulse response characteristic is raised at an enhancer circuit [figure (c)] and the most boosted area is represented as the secondary space area, an area 24 and an area 25 are obtained separating from the area 21. Thereby, the cross color can be reduced without reducing the resolution.

Description

Detailed Description of the Invention (Industrial Application Field) This invention relates to a color television system in which a color signal is frequency-multiplexed to a luminance signal and transmitted, particularly on a transmission side for cross color reduction in an NTSC color television system. The present invention relates to a signal processing device.

(Prior art and problems) Various efforts have been made to reduce cross color in current color television systems, especially NTSC color television systems, but most of these efforts involve decoding NTSC color signals on the receiving side. It has been paid for and improvements have been made. However, when creating an NTSC color signal,
That is, sufficient efforts have not been made in the NTSC encoder on the transmitting side, and the transmitting/receiving system as a whole is still insufficient.

(Means for Solving the Problems) An object of the present invention is to introduce the concept of two-dimensional spatial frequency response characteristics to more effectively reduce the aforementioned still insufficient loss color. , a color television system that transmits frequency-multiplexed color and luminance signals;
Particularly in the NTSC system, it is an object of the present invention to provide a color television signal processing device in which the enhancer circuit and track circuit of the transmitting side encoder are improved.

In other words, the latex revision signal processing device according to the present invention has the following features:
On the transmission side of a color television system in which a color signal is frequency-multiplexed with a luminance signal and transmitted, the system of the luminance signal is near the center frequency of the frequency-multiplexing of the chrominance signal of a horizontal frequency component in a two-dimensional spatial frequency domain; A two-dimensional filter having a pole in a region filling around 1/2 of the total number of horizontal scanning lines of the vertical frequency component, and an enhancer having poles in the vicinity of the horizontal and vertical spatial frequency axes of the two-dimensional spatial frequency region, respectively. , which is characterized by reduced cross color.

(Example) The present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1(a) shows a block diagram of an NTSC color television transmission system encoder. The input signals @R (red), G (green), and B (blue) signals are converted by the matrix circuit 1 into Y (i degrees), ■ (broadband color, and Q (narrowband color) signals. The signal then passes through an enhancer circuit 3 that emphasizes the signal corresponding to the edge portion and a trap circuit 5 for reducing cross color, and is added to the color signal by an adder 15 after a filter 17. .

1. Regarding the Q color signal, low-pass filter 1 (7) and low-pass filter 2 (11) corresponding to the respective color bands are used.
), the balance modulation circuit 1 (
9) The subcarrier signal is modulated by the modulation circuit 2 (13). The two-tone signals output from the modulation circuit 1 (9) and the modulation circuit 2 (13) are then added together in an adder 15, passed through a subcarrier filter 17, and then added to the Y signal in the adder 15. will be added. This filtered output signal is the NTS
This is the C signal. In the above case, the synchronization relationship is omitted.

When transmitting the NTSC signal created in this way and decoding it on the receiving side, the color signal separation circuit
A portion of the (Tp degree) signal is also mixed into the color signal side and demodulated as a color signal, causing image interference as a cross color. This often occurs in images with thin striped patterns, and when cross-coloring occurs, parts of the image that are originally uncolored are colored, creating a phenomenon that causes a flicker to appear when viewed.

The above-mentioned drawbacks can be alleviated by reducing the luminance signal component that goes around to the color signal separation circuit on the transmitting side, and this will be described in detail below.

Figure 2 schematically shows the horizontal and vertical two-dimensional spatial frequency response characteristics of a television image signal.
The conventional trap circuit of the encoder shown in the block diagram of FIG. 1(a) is based on the simple idea that it is sufficient to simply reduce the response in the frequency i range of the luminance signal multiplexed with the chrominance signal. A frequency region 22 indicated by diagonal lines in FIG. 2(a) is attenuated. Although it is certainly possible to reduce cross color, this also attenuates the luminance signal near the x-axis at the same time, which not only reduces cross color but also reduces the resolution of the image.

The subcarrier component of the chrominance signal is located at the center of the double circle area 21 in FIG. 2(a), and the signal around this area is demodulated as the chrominance signal by the decoder on the receiving side. At this time, not only the color signal but also the Y (luminance) signal in the vicinity is partially demodulated as a color signal and becomes a cross color, which deteriorates the image quality of the image.

Therefore, in order to reduce cross color, it is sufficient to remove components in this vicinity from the Y signal in advance. Furthermore, even if the signal in this vicinity is removed from the Y signal, no particular deterioration of the image quality will occur, since the human eye is sensitive to resolution in the diagonal direction of the screen.

FIG. 1(b) shows an embodiment of the trap circuit 5 according to the present invention for attenuating the Y signal in the region 21 of FIG. 2 <a> by utilizing the visual characteristics of the human eye.

Here, the delay circuit 51 (1H) is a delay line for one horizontal scanning line period, and the delay circuit 51 (2τ) is a delay line for 1/2 fs (fs: subcarrier frequency) (τ - 1/4 fS
). Further, the numbers in parentheses written below the counter 52 in the figure indicate the coefficients of the counter. These delay circuits, counters,
The adders are combined to form a filter and a counter 52 (
The output signal of the adder 53 in front of -1) is a signal whose maximum is at the center of the area 21 in FIG.
By subtracting (-1) from the original Y signal by the next adder 53, the Y signal component in the region 21 is removed.

Next, Fig. 3 shows an enhancer circuit 3 that has been conventionally used.
A circuit configuration block diagram is shown. Counter 32 (Jl>,
kh and kV of the counter 32 (kv>) are coefficients of the counter that performs gain control of the image edge signals in the horizontal and vertical directions, respectively, and both kll and kv have roughly similar values.

The frequency boosted at this time is approximately 3 MHz on the horizontal spatial frequency axis, although it varies somewhat depending on the value of τ of the delay circuit 31 (τ, ), and is approximately 262 TV lines/vertical height on the vertical spatial frequency axis. In other words, the region that is most boosted is region 23 in FIG. 2(b) in the two-dimensional spatial frequency representation, and this is region 21 in FIG. 2(Fi) where the main energy of the color signal component due to the subcarrier exists. are extremely close.

Therefore, there has been a drawback that increasing the amount of enhancement also increases cross color. FIG. 4(a) shows an impulse response due to the circuit configuration of the enhancer circuit 3 shown in FIG. However, it is assumed that kh -1 and kv -1.

FIG. 1(0) shows an embodiment of the enhancer circuit 3 according to the present invention, which improves the conventionally used enhancer circuit 3 shown in FIG. 3 and reduces cross color. The impulse response of this is shown in Fig. 4(b) and Fig. 14(c). In this enhancer circuit 3, the most boosted region is region 2 in FIG. 2(C) in a two-dimensional spatial frequency domain.
4 and region 25, it gives good results as an enhancer circuit. Also, the area where the subcarrier is located (Fig. 2 (C)
) region 2b) becomes a null point in this case, and there is no boosting in this vicinity at all. Therefore, cross color can be significantly reduced compared to conventional enhancer circuits.

Furthermore, the trap circuit and enhancer circuit of the embodiment of the present invention shown in FIG. 1(b) and FIG. It is also possible to insert.

In general, the trap circuit and enhancer circuit used in the present invention are Y in the receiving side decoder.

It can also be used as a circuit for C separation, and its use has the advantage that it does not require lowering the vertical resolution of the image, compared to using a simple comb filter.

(Effect of light) By implementing the present invention as described above, Y
The energy near the subcarrier (color subcarrier) of the (luminance) signal can be reduced to almost zero, and even if a color difference signal is added thereto, crosstalk is unlikely to occur, and the enhancer also has a horizontal spatial frequency of two-dimensional spatial frequency. By providing a characteristic in which the amount of boost is largest on the vertical spatial frequency axis, it is possible to achieve the desired cross color reduction without deteriorating the resolution.

[Brief explanation of drawings]

FIG. 1(a) is a block diagram of a transmission encoder related to the color television signal processing apparatus of the present invention, and FIGS. 1(b) and (C) are diagrams of the trap circuit and enhancer circuit of the embodiment of the present invention, respectively. The configuration block diagram, FIGS. 2(a), (b), and (C) are diagrams showing two-dimensional spatial frequency characteristics of images for detailed explanation of the present invention, and FIG. 3 is a diagram showing the conventionally used FIG. 4(a), FIG. 4(b), and (C) are diagrams showing the impulse responses of the enhancer circuits of the conventional and inventive configurations, respectively. FIG. 5 is the inventive enhancer circuit diagram. FIG. 2 is a block diagram of the configuration of a second embodiment. 1... Matrix circuit 3... Enhancer circuit 5
... Trap circuit 1 ... Low pass filter 19 ... Modulation circuit 111 ... Low pass filter 21
3...Modulation circuit 215...Adder 11...Filter 19...NTSC encoder 31.32
．． 33... Delay circuit, counter, adder of the enhancer circuit of the present invention 51.52.53... Delay circuit, counter, adder of the trap circuit of the present invention 21.22.23.24.25.26. ...Each area in two-dimensional spatial frequency display (Figure 2 Ca) (b) Horizontal space Ilit/MHz) *
! ￥ M shoulder height 118 (MHz) -CC) Kit circumference Ltf, (MHz) -Figure 3 (C) L+ Figure 5

Claims (1)

[Claims] 1. On the transmission side of a color television system in which a color signal is frequency-multiplexed with a luminance signal and transmitted, the system of the luminance signal is a horizontal frequency component of the color signal in a two-dimensional spatial frequency domain. a two-dimensional filter having a pole near the center frequency of the frequency multiplexing in an area filling around 1/2 of the total number of horizontal scanning lines of the vertical frequency component; and near the horizontal and vertical spatial frequency axes of the two-dimensional spatial frequency domain. 1. A color television signal processing device comprising an enhancer each having a pole to reduce cross color. 2. The two-dimensional filter connects in cascade a delay circuit network having a pole near the center frequency of the color signal frequency multiplexing and a delay circuit network having a pole near 1/2 of the total number of horizontal scanning lines. A color television signal processing device according to claim 1, characterized in that the color television signal processing device is configured as follows. 3. The enhancer has a 1H±2τ delay element and a 4τ
The color television signal processing device according to claim 1, characterized in that the color television signal processing device is configured to include a delay element.