JPH03201789A - Color signal processing circuit - Google Patents

Abstract

PURPOSE:To provide hue information (phase) and saturation information z(color amplitude level) independently by using an amplitude of a chrominance carrier signal and a phase signal, multiplying a trigonometric function using the phase signal as an angle with the amplitude and using the result of multiplication as a color difference signal. CONSTITUTION:An amplitude A and a phase omegat+phi are calculated from a chrominance carrier signal (chrominance carrier signal subject to orthogonal phase modulation represented by Asin(omegat+phi)...A is amplitude and omegat+phi is phase) and the phase of a reference phase signal of the color signal generated based on the burst signal included in the chrominance carrier signal as the reference is calculated. Moreover, the amplitude A of the chrominance carrier signal and the phase signal theta of the chrominance carrier signal are used and a trigonometric function using the phase signal theta as an angle and the amplitude A are multiplied with each other. Then the result of multiplication is used as a color difference signal. Thus, the hue information (phase) and the saturation information (color amplitude) are provided independently and the respective adjustment is simplified.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention provides Y/C separation of a composite video signal or Y/C separation of a composite video signal.
6. Related to a color signal processing circuit that demodulates a carrier color signal to a color difference signal in a /C separated signal [Prior art] Conventional color signal processing that demodulates a carrier color signal to a color difference signal is performed in an analog signal processing circuit. It is common to generate a continuous subcarrier signal that is phase-locked to the burst signal included in the signal, and use this signal to synchronously demodulate the carrier color signal. In addition, in digital color signal processing circuits, sampling is normally performed using a frequency around 4 times the subcarrier frequency, which is 4 times the subcarrier frequency (hereinafter referred to as 4f a
When sampling is performed using the clock in c), the sampled data of the carrier color signal is R-Y, B-
Y, -(RY), -(B-Y).

It is well known that -(RY), -( of the data is determined based on the phase of the burst signal).
By inverting the polarity of the term B−Y), a color difference signal is obtained. Also, based on the same concept as analog signal processing circuits,
A method of A/D converting continuous subcarrier signals that are phase-locked to the burst signal in the same way as the carrier color signal and synchronously demodulating them in a digital circuit (SCAD method, 1987
The National Conference of the Television Society of Japan: Lecture No. 13-4) has also been put into practical use.

[Problems to be Solved by the Invention] The above-described demodulation method from a carrier chrominance signal to a chrominance signal is based on a reference signal generated from a carrier chrominance signal and a burst signal.In the synchronous demodulation method, a carrier chrominance signal and a subcarrier signal are The color difference signal is extracted by low-pass filtering the product of , and in the case of using a 4f clock, the color difference signal is extracted by selectively reversing the polarity of the carrier color signal. These demodulation methods handle the elements of hue and color saturation in a mixed form, and cannot separate and process hue and color saturation, which have visually different characteristics.

Furthermore, if hue information (phase value) and color saturation information (color amplitude value) can be held independently, adjustment operations for each will be extremely simple.

[Means for Solving the Problems] Therefore, in order to achieve the above object, the color signal processing circuit of the present invention processes carrier color signals (A sin (ωt+φ)...A
is an amplitude value, and ωt+φ is a phase value of a carrier color signal subjected to orthogonal phase modulation, expressed as −1. means for calculating a phase value of a reference phase signal of a color signal generated with reference to a burst signal generated by the carrier color signal, and an amplitude value A of the carrier color signal and a hue signal 0 of the carrier color signal.
It has means for multiplying a trigonometric function value whose angle is by an amplitude value A, and uses the multiplication result as a color difference signal.

Further, a multiplier for multiplying the amplitude value A of the carrier color signal by a preset value is provided to adjust the degree of color saturation.

Further, an adder is provided to add a preset value to the phase signal O of the carrier color signal to adjust the hue.

[Example] Next, an example of the present invention will be described with reference to the accompanying drawings.

An embodiment of the present invention is shown in FIGS. 1(a), (b), and (c). In this embodiment, an NTSC video signal is A/D converted using a sampling frequency around four times the subcarrier frequency. This shows a case where color signal processing is performed by a digital circuit.

In FIG. 1(,), an NTSC video signal (composite video signal) is A/D converted, and a volatility signal and a carrier color signal are output by a Y/C separation circuit. FIG. 1(b) shows a circuit that outputs a color amplitude value A and a phase signal 0 from continuous subcarrier signals phase-locked to a carrier color signal and a burst signal.

Here, a method for determining the one-color amplitude value A and the hue signal θ will be described.

The carrier color signal can be expressed by the following equation.

c = = Asin (ωt + φ) (1) Here, A: color amplitude value ωt + φ: g'l existing phase value If this signal is sampled at a frequency around 4 times the subcarrier frequency, the continuous sampling data will be ,
It goes like this:

Assuming that the information on the carrier color signal changes at a sufficiently low frequency compared to the sampling frequency, ω=2xf, t
O: First time.

As1n (c, +tO+φ), As1n (ωto+φ
+90"), As1n (c, +to+φ+180°), As1n(ωto+φ+270'), As1n(ω
to+φ+360'), As in (ωt.

+φ+450”) ... (2)
Rewriting this, As1n(ωto+φ), Aco s(ωtO+φ
), -Asin (ωto+φ), -Acos(ωtO
+φ), As1n(ωto+φ), Ac.

S(ω10+φ)... (3) From this, the color amplitude value A is derived by the linear equation using the two consecutive data XIy.

))”+ (Acos (c, +to+φ))2=
=A (4) Equation (4) is the same no matter what continuous data is used.

The phase value is derived as follows.

As mentioned above, the carrier color signal C is expressed as c=A i n (
ω is expressed as 10φ). When this C is represented as a vector,
As shown in FIG. 2, a point a with a radius A and centered on the origin O is rotating at an angular velocity ω on a complex plane represented by a real axis and an imaginary axis.

The instantaneous value C of the carrier color signal is represented by the projection of point a onto the imaginary axis. Here, the data digitized as described above is obtained by sampling this carrier color signal approximately at every 90° phase angle. Now, since the phase angle φ at a certain moment on the complex plane is = (ωt + φ), the real axis at that time,
Representing the projection onto the imaginary axis by r and i, respectively, r=Acosφ, =Asin(φ, +901'), 1=
Asinφ, (5).

When this equation (5) is compared with the data arrangement of the above-mentioned equation (2), two consecutive pieces of data are the same as r and i in equation (5). Therefore, the phase angle φ at a certain moment is φa=j a n−' (i/r) = sin−” (A/ i ) =co s−” (A/r) (6)
Therefore, by performing either equation (6), the phase angle φ1 at a certain moment can be found.

Based on the above formula, the actual configuration is as follows.

In FIG. 1(b), the multiplier 3 calculates the square of the input data using the input carrier color signal. This result and 1
An adder 6 adds the result delayed by the clock delay device 4. The output of adder 6 is

This corresponds to x''+y2 in equation (4).By inputting this signal to the square root circuit 8 and finding the square root of the input signal, (4)
As shown in the formula, the desired color amplitude value A is obtained. Since the input signal of the square root circuit 8 is a digital signal, the ROM
(read-only memory), or it is also possible to obtain an approximate solution by creating a square root approximation curve. Alternatively, the color amplitude value A can be directly determined from two consecutive pieces of data by storing data in the ROM.

Next, in order to obtain the phase angle φ, it is sufficient to configure a circuit to obtain equation (6) using two consecutive pieces of data. In FIG. 1(b), a delay is performed by a one-clock delay device 5, and the input signal and the delayed signal are input to the ROM 7. If the ROM7 stores the solution corresponding to φ,=tan-'(i/r) in equation (6) from two consecutive data, the output of the ROM7 will be the value of the phase angle φ, Become.

At the same time, the subcarrier signal phase-locked to the burst signal is A/D converted by an A/D converter 9, and a DC component is removed using a BPF (band pass filter) 10 to obtain a reference subcarrier signal. . The phase angle of the subcarrier signal obtained in this way is determined using the 1-clock delay device 11 and the ROM 12 in the same manner as the phase angle of the carrier color signal was determined.

The phase angle of the carrier color signal thus obtained is compared with the phase angle of the subcarrier signal to obtain a phase signal θ which is color phase information of the carrier color signal. This method will be explained below.

Here, phase signal 0, which is color phase information, is a value representing how much the phase is shifted with respect to the subcarrier signal. If the subcarrier signal is expressed by one equation like the carrier color signal, it will be as follows.

Subcarrier b=E sin (ωt+B) (7) Therefore, using the subcarrier signal as a reference, B=0 can be obtained, Subcarrier b=E sin (ωt) (
8) From equation (8) and equation (1) representing the carrier color signal, the phase angles of the subcarrier signal and carrier color signal are respectively (ωt+
φ) and (ωt), and it can be seen that there is always a phase difference of φ. Since the target phase signal O is the phase difference (difference in phase angle) between the carrier color signal and the subcarrier signal, φ=
It becomes 0.

Therefore, the actual configuration in which the difference between the calculated phase angle of the carrier color signal and the phase angle of the subcarrier signal becomes the phase signal θ is as follows:
It will look like this:

The calculated phase angle is expressed as a digital value from Oo to 360°. For the sake of clarity, we will use the digital value O that can be expressed as an 8-bit digital value as Oo, and 255 as (
Let's consider it in correspondence to 255X (360·256))°. The ROM 7.12 outputs digital values from 0 to 255 as the phase angle. A phase signal O is obtained by taking a difference between these phase angles using a subtracter 13. If the value of 255 is subtracted from O, a negative value will result, but in this case as well, it is sufficient to consider the negative angle as in the case of normal angle display.

The color amplitude value A and phase signal O obtained in this way are shown in Fig. 1 (
C) is input to the color amplitude value A input terminal and the phase signal 0 input terminal.

Phase signal 0 is an angle on a complex plane with the subcarrier signal as a reference, but the subcarrier signal represents the color signal (
Since the phase is on the -(B-Y) axis on the (B-Y) plane, the color difference of the signal with the color information of the color amplitude value A and the phase signal θ is calculated based on this point. Signal (R-Y
) and (B-Y) are each expressed as follows.

(RY) = -A sin θ (B-Y) = -A cos & (
9) Therefore, by calculating the product of the trigonometric function value with the phase signal 0 as an angle and the color amplitude value A, the desired color difference signal can be obtained.

In FIG. 1(c), from the phase signal θ, a coefficient generator 14.1
5 to find the trigonometric functions -5ina and -COSO. The output of multipliers 16 and 17 that multiply this trigonometric function by the color amplitude value is the color difference signal RY.

It becomes B-Y.

The coefficient generator 14.15 is R like the ROM 7.12.
Can be easily configured with OM. Also, since the input signal 1 corresponds to the output signal 1, create an approximate curve,
It can also be easily configured by generating coefficients.

Through the above signal processing, the carrier color signal can be demodulated into a color difference signal. In the case of a television receiver, R and G are obtained from a luminance signal that has undergone contrast adjustment and edge enhancement processing, and a color difference signal.

The digital value representing the phase angle used to create the B signal and drive the cathode ray tube was set from 0 to 255, which can be expressed in 8 bits, for ease of understanding.
2 and the contents of the coefficient generators 14 and 15, this range can be freely set.

Further, as shown in FIG. 4, the color gain can be adjusted by adjusting the gain using the 1 multiplier 19 for the color amplitude value A outputted in FIG. 1(b), and the phase signal θ
By adding the phase adjustment value α in the adder 20, the phase signal becomes θ+α, and the phase can be adjusted. Since the output of the adder 20 may exceed the value that can be expressed in 8 bits, the overflow processor 21 subtracts 256 from the input value for digital values of 256 or more, so that the angle falls within the range of 0 to 255. I can pay it. This is clear from the angle 360°=O°. If the signal subjected to these adjustment processes is inputted to FIG. 1(c), an adjusted color difference signal can be obtained.

Also, in the explanation, the subcarrier is used as a reference signal, and A
/D conversion, but when using a clock phase-locked to the burst signal as the clock for operating the system, the reference phase angle should be changed to Oo, 90", 180', 270”,
Even if the signal is generated in a fixed manner, the phase signal can be calculated. This is because the clock itself is phase-locked to the burst signal and serves as a reference point for the color signal.

[Effects of the invention] With the above configuration, it is possible to have one hue information (phase value) and one color saturation information (color amplitude value) independently, and also to adjust these independently and easily. I can do it.

[Brief explanation of drawings]

FIGS. 1(a) to 1(C) are block diagrams according to an embodiment of the present invention, and FIG. 1(a) shows the process from inputting an NTSC signal to obtaining a carrier color signal. (b) shows the process from inputting a carrier color signal and a subcarrier signal to obtaining a color amplitude value A and a phase signal 0. (c) inputs the color amplitude value A and the phase signal 0, and then inputs the color difference signal R.
-Y and BY are shown. FIG. 2 shows a vector representation of the carrier color signal on the complex plane, and FIG. 3 shows the phase of the burst signal and the phase of the carrier color signal C on the RY and BY planes. Figure 4 is Figure 1(b)
This is an example in which color gain adjustment and hue adjustment are performed using the color amplitude value A and hue signal θ obtained in . 1.9... A/D converter, 2... YlC separation circuit,
3, 16, 17, 19... Multiplier 1.5.11...
1 clock delay device, 6, 20... Adder, 7, 12...
・ROM (read only memory), 8... square root circuit, 10... BPF (band pass filter), 1
3... Subtractor, 14... Coefficient (-sin θ) generator,
15... Coefficient (-cos θ) generator, 21... Overflow processor.

Claims (3)

[Claims] (1) means for calculating an amplitude value and a phase value from a carrier color signal; and means for calculating a phase value of a reference phase signal of a color signal generated based on a burst signal included in the carrier color signal; A color characterized by comprising means for multiplying the amplitude value and the phase signal of the carrier color signal by a trigonometric function value using the phase signal as an angle and the amplitude value, and using the multiplication result as a color difference signal. signal processing circuit. (2) The color signal processing circuit according to claim 1, further comprising a multiplier for multiplying the amplitude value of the carrier color signal by a preset value to adjust color saturation. (3) The color signal processing circuit according to claim 1, further comprising an adder for adding a preset value to the phase signal of the carrier color signal to adjust the hue.