JPH0369239B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a color coder matrix circuit that generates volatility signals and color difference signals from, for example, digitized primary color video signals.

[Technical background of the invention and its problems]

As is well known, this type of color coder matrix circuit that has been used in practice is based on analog signal processing, and is based on red, green, blue (hereinafter referred to as R, G, B).
The luminance signal and color difference signal are obtained from the primary color video signal (abbreviated as ) by a matrix circuit consisting of a resistor network and transistors. For this reason, each coefficient of the matrix circuit is affected by resistance accuracy, temperature changes, changes over time, and input/output impedance fluctuations due to changes in each parameter of the transistor.In actual operation, complicated daily adjustments and Daily inspection was required. Furthermore, many variable regulators, such as variable resistors, are used for adjustment and inspection, and this creates a contradiction in that the variable resistors become even more variable elements and become a factor that increases the failure rate.

For this reason, many digital color coders have been developed in recent years. In this case, the coefficients of the matrix circuit are obtained by approximate calculation, and the digitized R, G, B primary color video signals are approximately obtained by a combination of bit shift operation and addition/subtraction. That is, for example, the luminance signal Y according to the NTSC system is synthesized from the R, G, and B primary color video signals according to the following equation: Y=0.30R+0.59G+0.11B (1). digitized R,
When the calculation of equation (1) is performed using the G and B primary color video signals, an example of calculation using the shift calculation and addition/subtraction is as follows.

0.30≒2 ^-2 +2 ^-4 =0.3125 …(2) 0.59≒2 ^-1 +2 ^-4 =0.5625 …(3) 0.11≒2 ^-3 =0.125 …(4) In such a calculation, the coefficient of R is approximately 4
%, an error of about -4.7% for the coefficient of G, and an error of about 13.6% for the coefficient of B. This is because the matrix coefficients of the existing analog method are designed with an error of about 0.5%, and are adjusted to an error of about 1%.
This is an extremely large error compared to what has been confirmed. Further, this error can be similarly applied to a matrix circuit that synthesizes color difference signals. Therefore, conventional digital color coders are inferior to analog color coders in color reproduction, which is an important characteristic of color television cameras. In order to improve the precision of this characteristic, more shift operations, additions and subtractions are required, which complicates the circuit configuration and reduces reliability.

[Purpose of the invention]

The present invention has been made based on the above circumstances, and its purpose is to provide highly accurate luminance signals and color difference signals that are extremely close to the ideal values of coefficients specified in a predetermined television broadcasting system by simplifying the configuration. The present invention is intended to provide a color coder matrix circuit that can be obtained.

[Summary of the invention]

This invention stores, for example, in a storage circuit a value obtained by multiplying a digitalized R, G, and B primary color video signal by a coefficient necessary to obtain an NTSC luminance signal and a color difference signal, and then stores this value in a digital signal. Each address is designated and read out using the converted primary color video signal, and these read out signals are added and subtracted to obtain the required luminance signal and color difference signal.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, R components of a luminance signal Y and color difference signals I and Q are obtained from an R primary color video signal. The component RY of the luminance signal Y due to R is expressed in equation (1).
0.30R, and the components RI and RQ of color difference signals I and Q due to R are as follows: I=0.60R−0.28G−0.32B…(5) Q=0.21R−0.52G+0.31B…(6) It is indicated by 0.60R and 0.21R. 11 in the figure,
12 and 13 are read-only memory circuits (hereinafter abbreviated as ROM), respectively. This ROM11,
12 and 13 are each addressed by an R primary color video signal digitized with n bits, and after this address designation, the memory contents at the address designated by the clock signal CLK that designates the read timing are Read out. This ROM1
1, 12, and 13 each have an R primary color video signal.
Binary values RY ₁ to RY _o , RI ₁ to RI _o , and RQ ₁ to RQ _o obtained by multiplying the decimal number by the above-mentioned 0.30, 0.60, and 0.21 are stored at addresses 1 to n. Therefore, depending on the address specification, ROM11, 12, 1
From 3 onwards, the signal corresponding to the address is 0.30, 0.60,
Components of luminance signal Y, color difference signals I, and Q multiplied by 0.21 due to R RY ₁ ~RY _o , RI ₁ ~RY _o , RQ ₁ ~
RQ _o is output.

By applying the above configuration to the G primary color video signal and the B primary color video signal, 2 of equations (1), (5), and (6) can be obtained.
G and B components of the luminance signal Y corresponding to terms 3 and 3
GY, BY and G, B components GI of color difference signals I, Q,
GQ and BQ are obtained. By combining these signal components, a luminance signal Y and color difference signals I and Q can be obtained.

FIG. 2 shows its configuration. 3 in the diagram
1, 32, and 33 are respectively addressed by R, G, and B primary color video signals digitized with n bits, and RY, RI, RQ, GY, GI, GQ,
This is a memory circuit that outputs signal components BY, BI, and BQ, and has the same configuration as that in FIG. 1. Among the outputs of the memory circuits 31, 32, 33, the luminance signal components RY, GY, BY are supplied to the digital adder circuit 34, and the I, Q signal components RI, GI, BI and
RQ, GQ, and BQ are supplied to digital addition/subtraction circuits 35 and 36, respectively. Therefore, adder circuit 3
4, the calculation corresponding to equation (1) is performed and the luminance signal Y is output, and the addition/subtraction circuits 35 and 36 calculate equation (5),
Calculations corresponding to equation (6) are performed, and color difference signals I and Q are output.

According to the above configuration, each of the R, G, and B primary color video signals digitized with n bits is converted to NTSC.
They are multiplied by the coefficient values required for system conversion, and these values are stored in the ROM. Since each digital value stored in this ROM is a finite number of bits, it is ±1/2 of the ideal value of equations (1), (5), and (6).
LSB error occurs. However, this error is about ± when the primary color video signal is digitized with 8 bits.
Approximately ± when digitized at 0.2%, 10 bits
Since it is 0.05%, it is possible to obtain luminance signals and color difference signals with extremely high precision compared to conventional analog or digital color coder matrix circuits.

In the above embodiment, the case where each signal of the NTSC system is obtained from the primary color video signals of R, G, and B was explained, but the present invention is not limited to this.
The same method can be applied to other methods by changing the coefficients of the matrix. Furthermore, it is also possible to convert the color difference signal into, for example, RY, BY by changing the coefficients of the matrix. In other words, even if the primary color video signal of the color television camera, which is the main signal source of the color coder matrix circuit, is different from the R, G, B system or the Y, R, B system, it is possible to make a major configuration change by changing the stored contents of the ROM. It has the advantage that it can be dealt with without having to do so. However, in this case, instead of ROM, for example, a programmable read-only memory circuit (P-ROM), etc.
It is necessary to use a memory circuit whose memory contents can be rewritten.

Further, the ROM may store numerical values subjected to γ correction. In this way, it is possible to simplify the circuit configuration of the previous stage.

〔Effect of the invention〕

As detailed above, according to the present invention, it is possible to obtain highly accurate luminance signals and color difference signals that are very close to the ideal values of coefficients specified in a predetermined television broadcasting system with a simple configuration. A coder matrix circuit can be provided.

[Brief explanation of drawings]

The drawings show an embodiment of a color coder matrix circuit according to the present invention, with FIG. 1 showing the configuration of a memory circuit, and FIG. 2 showing the configuration of the color coder matrix circuit. 31, 32, 33...memory circuit, 34...addition circuit, 35, 36...addition/subtraction circuit.

Claims (1)

[Claims] 1 A plurality of digitized video signals are each multiplied by a conversion coefficient corresponding to a predetermined television broadcasting system, and each of these multiplied values is stored, and this value is individually addressed by the corresponding digitized video signal. 1. A color coder matrix circuit comprising: a memory circuit that is specified and read; and means for adding and subtracting output signals of the memory circuit and outputting a signal conforming to the television broadcasting system.