JPH044693A - Video signal processing unit - Google Patents

Abstract

PURPOSE:To reduce the circuit scale and to realize the device with low cost and power consumption by employing a means applying gamma correction to a luminance signal, a means extracting only a high frequency luminance signal form the luminance signal subjected to gamma correction, and a means adding both the low and high frequency luminance signals. CONSTITUTION:R, G, B input signals 1-3 are divided into two respectively, one is fed to low pass filters(LPF) 4-6 and they are subjected to band limit to a chrominance signal band (0-1.5MHz). Moreover, the other R, G, B input signals 1-3 are fed to a matrix circuit 11 directly, in which they are mixed in a ratio of 0.3:0.59:0.11 to obtain a luminance signal before gamma correction. Then a luminance signal Y' subjected to gamma correction is fed to a high pass filter(HPF) 13, in which the signal is converted into a high frequency luminance signal YH whose chrominance signal band component is cut. The high frequency luminance signal TH and the low frequency luminance signal YL are added by an adder circuit 14 to obtain the luminance signal Y.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a color video signal processing device.

[Summary of the invention]

The purpose of the present invention is to correct the drawback that the current color television system performs gamma correction on the transmitting side, so the constant brightness principle does not hold and the resolution of images with high nine-color saturation decreases. , G, and B signals when synthesizing a luminance signal.

The low-frequency components are synthesized by applying gamma processing to the R, G, and B signals individually and mixing them at a fixed ratio.For the high-frequency components, the R, G, and B signals are mixed at a fixed ratio and then synthesized. By applying gamma processing and extracting only the high frequency components from this output.

This is to prevent resolution deterioration of the above-mentioned image with high color saturation.

[Conventional technology]

First, we will briefly explain the effects of gamma correction performed on the transmission side in current television systems. N.T.
In current television systems such as SC and PAL, R, G,
The luminance signal Y and the color difference signal are synthesized from the B signal, and the luminance signal Y
A band-limited chrominance signal is modulated with a chrominance subcarrier and superimposed on the chrominance signal.

Therefore, the band components of each R, G, and B signal are the luminance signal Y
This is a high-frequency component that is transmitted only by That is, if the low-frequency component and high-frequency component of the R signal are respectively RL, and those of the RH1 luminance signal Y are tYLIYH, then the original R signal is RL.
+RH, but the R signal reproduced on the receiver side is RL
+Y14. Now, since gamma correction originally corrects the light emission characteristics of the cathode ray tube, the R signal R reproduced by the above-mentioned receiver has the following.

R= (R') + (Y')H・・・・・・・・・
・・・・・・・・・・・・Gamma processing should be performed so that (1) is obtained.

However, in reality, this gamma correction is performed on R and G on the transmitting side.
, in the R signal at the stage of the B signal.

R'=R'・・・・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・・・・・・・(2
). Therefore, if we consider a case where the level of the R signal is 1 (100%) and the levels of the G and B signals are O, the luminance signal Y will be R and G.

Since the B signals are mixed and synthesized at a ratio of 0.3: 0.59: 0.11, the R signal R', which has been gamma-processed on the transmitting side, is converted into the R signal actually reproduced by the receiver. The signal R' is.

It has the characteristics shown in. For this reason, now this 1
Even if there is a minute high frequency component on the 00% R signal, this component is compressed by 0.45 times, so the reproduced R signal R' is.

R'=R+ 0.135RH・・・・・・・・・
・・・・・・・・・・・・(4) γ L . On the other hand, as mentioned earlier, if gamma correction is to be performed on the receiver side, then from equation (1) above.

R,= (R')L+((0,3R)')□・・・・・・
(5), since the slope of the γ curve near the input level of 0.3 is approximately 1.

R,=RL+0.3RH・・・・・・・・・・・・
・・・・・・・・・・・・(6) That is, in the above case, when gamma correction is performed on the transmitter side, compared to when it is corrected on the receiver side.

The response of the high frequency component of the signal deteriorates to 0.13510.3.

As a conventional method to solve this problem, JP-A-63-67
There is a technique disclosed in Japanese Patent No. 890.

This configuration is shown in FIG. 3, and this method will be explained below.

In the matrix circuit 11, the R, G, and B signals each subjected to gamma correction by the gamma correction circuits 7 to 9 are mixed at a predetermined ratio to synthesize a luminance signal Y'.

In addition, in the matrix circuit 10, R2O before gamma correction,
B signals are mixed at a predetermined ratio, and gamma correction circuit 1 is applied to this mixture.
2, a luminance signal Y' to which gamma correction has been added is obtained. Then, the division circuit 21 calculates Y'/Y', and the conversion circuit 23 converts this value into a predetermined value, followed by a high-pass filter (H
The multiplier 24 multiplies the luminance signal YH passed through the PF) 22, and adds it to the luminance signal YL passed through the low-pass filter (LPF) 20 in the adder circuit 25 to obtain a corrected luminance signal Y. .

Using this method, it is possible to correct resolution deterioration of signals with high color saturation caused by gamma correction on the transmitting side.
Since a divider and a multiplier are required, the scale of the 9 circuits inevitably increases.

Problems include increases in device size, cost, power, etc.

[Problem to be solved by the invention]

An object of the present invention is to enable resolution deterioration of an image signal with high color saturation caused by the above-mentioned gamma correction on the transmitting side to be performed without using a complex calculation circuit configuration with two circuits, and with a small circuit scale and power consumption. This makes it possible to realize a low-cost device.

[Means to solve the problem]

In order to achieve the above object, the present invention includes a means for extracting only the low frequency components of each R, G, and B signal, a means for applying gamma correction to the low frequency components, and a means for applying gamma correction to each signal subjected to the gamma correction. A means for synthesizing a low-range luminance signal by mixing at a ratio, mixing the R9G and B signals without band limitation at a predetermined ratio,
means for synthesizing luminance signals, means for gamma-correcting the luminance signals, means for extracting only high-frequency luminance signals from the gamma-corrected luminance signals, and means for adding the low-frequency and high-frequency surface luminance signals. is used.

[Effect]

The present invention takes into account that in current television systems, high-frequency components are transmitted only by luminance signals,
When synthesizing a luminance signal from R, G, and B signals, the low-frequency components are gamma-corrected separately at the R, G, and B signal stages, and the high-frequency components are synthesized using R without any band limitation. , G, and B signals and then performs gamma correction to obtain a gamma-corrected luminance signal.Therefore, there is no deterioration in the resolution of signals with high two-color saturation, there is no increase in the circuit size, and the receiver side This produces the same effect as when gamma correction is performed.

〔Example〕

An embodiment of the present invention is shown in FIG. 1, and the operation of the present invention will be explained in detail below. The R, G, and B input signals 1 to 3 are each divided into two parts, one of which is passed through each low-pass filter (
LPF) sent to 4-6.

Each is band-limited to a color signal band (about 0 to 1.5 MHz). These outputs are sent to each gamma correction circuit 7 to 9, and are subjected to gamma correction with characteristics as shown in FIG. 2 in order to reversely correct the emission characteristics of the cathode ray tube on the receiver side.

Each signal that has undergone this processing is as follows.

The R, G, and B signals are sent to the matrix circuit 10, respectively.
They are mixed at a ratio of 0.3:0.59:0.11 to form a low-band luminance signal YL. Furthermore, the other R, G,
The B input signals 1 to 3 are also directly sent to the matrix circuit 11, and the same <, R,
The G and B signals are mixed at a ratio of 0.3:0.59:0.11 to produce a luminance signal before gamma correction. This luminance signal is subjected to gamma processing with characteristics as shown in FIG. 2 in the gamma correction circuit 12. Thereafter, this gamma-corrected luminance signal Y' is sent to a high-pass filter (HPF) 13.

High-frequency luminance signal Y with components of the above color signal band cut)
It is converted to I. This high-frequency luminance signal YH and the low-frequency luminance signal YL are added by an adder circuit 14 to obtain a luminance signal Y. As described above, in the present invention, gamma correction is applied to the high frequency component in the state of the luminance signal, so when a color difference signal modulated by a color subcarrier is superimposed on the luminance signal obtained in this way and transmitted. Even when reproduced on a cathode ray tube without performing gamma correction on the receiver side, there is no degradation in the resolution of signals with high 9-color saturation, so an image equivalent to that obtained when gamma correction is performed on the receiver side can be obtained. It turns out.

〔Effect of the invention〕

As described above, by using the present invention, problems caused by gamma correction on the transmitting side of the current television system can be solved using a small-scale, low-cost circuit without performing complicated calculations using a square multiplier and a divider by 2. This has the great effect of being able to solve this problem.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention. FIG. 2 is a diagram illustrating gamma correction characteristics, and FIG. 3 is a block diagram illustrating a conventional system. 7 to 9, 12: Gamma correction circuit, 4 to 6: Low pass filter (LPF), 10.11: Matrix circuit, 13
: High-pass filter (HPF), 14: Adder. 2\'? JL Hale

Claims (1)

[Claims] 1. In a video signal processing device that mixes R, G, and B video signals at a predetermined ratio to synthesize a luminance signal, the R, G, and B video signals, each having a predetermined band limit and gamma correction, are means for synthesizing a low-band luminance signal by mixing at a ratio of
, a means for extracting a high-frequency luminance signal of a predetermined band after mixing B video signals at a predetermined ratio and applying gamma correction, and adding these low-frequency luminance signals and high-frequency luminance signals to synthesize a luminance signal. 1. A video signal processing device, comprising: means.