JP2001119712A - Color signal processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a color signal processor that can correct the offset angle of at least a demodulation axis in spite of employing a smaller number of ROMs. SOLUTION: Burst detection means 2, 3 detect a burst amplitude Ar of an R-Y component Er of a base band chrominance signal and detect a burst amplitude Ab of a B-Y component Eb of the base band chrominance signal, a 1st arithmetic means 4 applies multiplication and addition/subtraction processing to the values Er, Eb, Ar, Ab, the Ar, Ab values are given to a 2nd arithmetic means 5, which outputs a coefficient K that is expressed by Equation relating to (Ar2+Ab2) and multipliers 7, 8 multiply the coefficient K with the result of arithmetic operation by the 1st arithmetic means 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color signal processing device for suppressing hue fluctuations contained in a baseband color signal, and more particularly, to a color signal processing device which is preferably disposed after a decoder for demodulating a modulated color signal into a baseband color signal. A color signal processing device.

[0002]

2. Description of the Related Art In an actual operation of a decoder, a demodulation axis of a decoder has an axis deviation angle θ as compared with a normal axis due to a delay time caused by a time constant of a detection filter.
When displayed as an image on a TV monitor, color unevenness occurs and image quality is degraded.

For this reason, an analog input baseband color signal is converted into a digital color signal, and the above-described axis deviation is corrected using a phase error detection circuit and a phase error correction circuit. Such a concept is disclosed in Japanese Unexamined Patent Publication No. 5-34453.
No. 7 is also described.

FIG. 5 is a block diagram showing a conventional configuration, wherein 1 is a decoder, 15 is a phase error detection circuit, and 16 is a phase error correction circuit. Here, the phase error detection circuit 15
Are burst detection circuits 2 and 3 and a phase detection ROM 11
And the phase error correction circuit 16 is a sinROM
13, a cosROM 14 and an arithmetic means 12.

[0005] An input digital modulated chroma signal is demodulated by a decoder 1 and a baseband color signal RY
The component Er and the BY component Eb are output.

[0006] Er and Eb are respectively burst detection means 2,
At 3, the burst amplitudes Ar, Ab are detected. The phase detection ROM 11 receives the values of Ar and Ab, compares them with the function ROM table, and outputs the corresponding burst phase θ.

Here, a method of calculating the burst phase θ will be described.

FIG. 6 shows the relationship between the demodulation axis of the decoder 1 and the decoder output signal. In FIG. 6, the RY axis and the B-
The Y axis indicates an axis in an ideal state, that is, a normal axis. On the other hand, the r-y axis and the b-y axis correspond to the decoder 1
, And has an axis deviation angle θ as compared with the normal axis. In the actual operation of the decoder, θ does not become zero due to the influence of the delay time caused by the time constant of the detection filter, etc., and when the image is displayed as an image on the TV monitor,
It causes color unevenness and lowers image quality.

From FIG. 6, the following relational expression holds.

Ar = A * sin θ (1) Ab = −A * cos θ (2) ER = Eb * sin θ + Er * cos θ (3) EB = Eb * cos θ−Er * sin θ (4) where ER and EB are the RY component and the B-Y component of the baseband color signal when decoded on the normal demodulation axis.
A component is a Y component, and A is a value represented by the following equation (5) and corresponds to the burst amplitude of the modulated chroma signal.

A = √ (Ar ² + Ab ² ) (5) From the above equations (1) and (2), the burst phase θ of the following equation (6)
Is calculated.

Θ = −tan ⁻¹ (Ar / Ab) (6) Accordingly, if the phase detection ROM 11 has a function ROM table based on the relationship of Expression (6), it can respond to the input of Ar and Ab. The burst phase θ can be output.

The output θ of the phase detection ROM 11 is sinR
Input to the OM 13 and the cosROM 14,
The values of inθ and cosθ are output.

The operation means 12 includes Er, Eb, sin
θ and cos θ are input, and the above equations (3) and (4)
Is performed, and ER and EB are output. E
R and EB satisfy the equations (3) and (4), and correspond to the RY component and the BY component of the baseband color signal when decoded on the normal demodulation axis. That is, the above-described adverse effect of the axis shift angle θ is correctly corrected.

[0015]

However, in the prior art shown in FIG. 5, the phase detection ROM 11, the sinROM 1
3 and cosROM 14 are required as components. However, in an actual circuit, the ROM requires a larger number of elements than a simple adder / subtractor or a multiplier, so that there is a problem that the circuit scale becomes large.

The adverse effect of the axis deviation angle θ is corrected,
There is also a problem that it has no effect of correcting amplitude fluctuation.

An object of the present invention is to provide a color signal processing device which can correct at least the axis deviation angle of the demodulation axis by using less ROM.

[0018]

In order to achieve the above object, the present invention provides a method for detecting a burst amplitude Ar of an RY component Er of a baseband chrominance signal and a method of detecting a burst amplitude Ar of a baseband chrominance signal.
A burst detector for detecting the burst amplitude Ab of the Y component Eb, a first calculator for receiving values of the Er, Eb, Ar and Ab and multiplying and adding / subtracting them, and the Ar and Ab Is input, and the coefficient K is expressed by the following equation (7) related to (Ar ² + Ab ² ). A color signal processing device comprising: a multiplier for multiplying the calculation result by the coefficient K.

Here, the second calculating means calculates the coefficient K as follows: coefficient K = k1 / (√ (Ar ² + Ab ² )) where k1 is a coefficient K expressed by a constant (8) If the output is made, the axis deviation angle θ can be corrected.

Here, the second calculating means outputs a coefficient K represented by the following equation: K = k2 / (Ar ² + Ab ² ) where k2 is a constant (9) In this case, the axis deviation angle θ and the amplitude fluctuation can be corrected.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of one embodiment of the present invention, wherein 1 is a decoder, 2 and 3 are burst detection circuits, 4 and 5 are arithmetic means, 6 is a coefficient ROM, and 7 and 8 are It is a multiplier. The operations of the decoder 1, the burst detector 2, and the burst detector 3 are the same as those in FIG.
Arithmetic means 5 receives burst amplitudes Ar and Ab, and outputs Ar ² + Ab ² . Here, since the calculation is performed by multiplication and addition, the calculation means 5 is configured without using a ROM. In the coefficient ROM 6, an operation represented by the following equation (10) is realized.

[0022] K = 1 / √ (Ar ² + Ab ² ) = 1 / A (10) Er, Eb, Ar and Ab are input to the calculating means 4 and are expressed by the following equations (11) and (12). Two outputs ER
1 and EB1 are output.

ER1 = Ar * Eb−Ab * Er (11) EB1 = − (Ab * Eb + Ar * Er) (12) ER1 is multiplied by a coefficient K by a multiplier 7 to become ER2, and EB1 is multiplied by a coefficient K in a multiplier 8 to form EB2. From equations (10), (11) and (12), ER2 and E
B2 is represented by the following equations (13) and (14).

ER2 = (Ar * Eb−Ab * Er) / A (13) EB2 = − (Ab * Eb + Ar * Er) / A (14) On the other hand, equations (1) and (2) ( 3) Using (4), the following equation (1)
5) The relational expression of (16) is derived.

ER = (Ar * Eb−Ab * Er) / A (15) EB = − (Ab * Eb + Ar * Er) / A (16) From the above equations (13) and (15), ER2 is obtained. = ER, the above equation (1
4) It can be seen from (16) that EB2 = EB is realized. That is, the configuration of FIG. 1 achieves the same effect of correcting the axial deviation angle θ as that of FIG. 5 of the related art.

FIG. 2 is a block diagram of another embodiment of the present invention, wherein 1 is a decoder, 2 and 3 are burst detectors,
4, 5 are arithmetic means, 6 is a coefficient ROM, 7, 8 are multipliers,
9 and 10 are amplifiers. Here, the coefficient ROM 6
Then, the calculation represented by the following equation (17) is realized.

[0027] K = 2 / √ (Ar ² + Ab ² ) = 2 / A (17) On the other hand, the gains of the amplifiers 9 and 10 are halved in output with respect to the input. Therefore, for FIG.
The doubling by the OM 6 is halved by the amplifiers 9 and 10. Then, the configuration of FIG. 2 achieves the same effect of correcting the axis deviation angle θ as that of FIG. 5 of the related art.

According to the configuration shown in FIGS. 1 and 2, only the coefficient ROM 6 is used as the ROM, as shown in FIG.
Since it is not necessary to use three ROMs, the circuit scale can be reduced.

The following embodiment will be described. In the following embodiment, in FIG. 1, instead of the operation represented by the above-described expression (10), the following expression (1) is used as the operation of the coefficient ROM 6.
This is an example in which the calculation represented by 8) is used.

[0030] K = A / (Ar ² + Ab ² ) (18) where A is a constant and the burst amplitude A of the modulated chroma signal
Set to a value equal to the desired value of The relationship between A and A can be expressed by the following equation (19) using the amplitude variation rate k.

A = k * A (19) When the amplitude A of the modulated chroma signal fluctuates at the fluctuation rate k, generally, outputs Er and Eb of the decoder 1 and their burst amplitudes Ar and Since Ab also fluctuates at the same ratio, it can be expressed by the following equation.

Er = k * Er (20) Eb = k * Eb (21) Ar = k * Ar (22) Ab = k * Ab (23) Er , Eb , Ar , and Ab are constants.

At this time, equations (11), (12) and (20)
From (21), (22) and (23), ER1 = k ² ( Ar * Eb − Ab * Er ) (24) EB1 = −k ² ( Ab * Eb + Ar * Er ) (25) Further, the formula (18) (22) from (23), K = A / (k 2 (Ar 2 + Ab 2)) = 1 / (k 2 * A) ··· (26) formula (24) (25 ER1 and ER2 represented by
Multipliers 7 and 8 multiply the K value of equation (26) to obtain ER2 and EB2 represented by the following equations.

ER2 = K * ER1 = ( Ar * Eb − Ab * Er ) / A (27) EB2 = K * EB1 = − ( Ab * Eb + Ar * Er ) / A (28) On the other hand, the desired values ER and EB of ER and EB expressed by the equations (14) and (15) are realized when each term on the right side is a desired value, and can be expressed by the following equation.

[0035] ER = (Ar * Eb - Ab * Er) / A ··· (29) EB = - (Ab * Eb + Ar * E r) / A ··· (30) equation (27) (28) From (29) and (30), ER2 = ER (31) EB2 = EB (32) Therefore, at this time, in the configuration of FIG.
Is realized, and at the same time, a correction effect of the amplitude fluctuation expressed by the fluctuation rate k is realized.

In the configuration of the block diagram of FIG.
The coefficient ROM 6 may realize the calculation represented by the following equation (33).

K = 2A / (Ar 2 + Ab 2) (33) At this time, the gains of the amplifiers 9 and 10 at the subsequent stages of the multipliers 7 and 8 are halved in output with respect to the input.

Then, in the above configuration, the above-described axis deviation angle θ
May be realized, and at the same time, the effect of correcting the amplitude fluctuation expressed by the fluctuation rate k may be realized.

Therefore, according to this configuration, only the coefficient ROM 6 is used as the ROM, and three ROMs need not be used as in the conventional FIG. 5, so that the circuit scale can be reduced. The effect of correcting the amplitude fluctuation can also be realized.

FIG. 3 shows a block diagram of another embodiment of the present invention. The difference from FIG. 1 is that the dynamic range determination circuit 11 for the output K of the coefficient ROM 6 and the switches 12, 1
3 is added. The output Er of the decoder 1 is input to one input of the switch 12, and the output ER2 of the multiplier 7 is input to the other input. The output Eb of the decoder 1 is input to one input of the switch 13, and the output EB2 of the multiplier 7 is input to the other input.

Here, the coefficient ROM 6 performs the operation expressed by the equation (10) or (18). In either case, if the value of the input Ar ² + Ab ² becomes very small, In some cases, the value of the output K of the coefficient ROM 6 becomes very large and may exceed the output dynamic range. This state can occur if the amplitude of the modulated chroma signal input to the decoder 1 is input at a small value. Coefficient R
If the output dynamic range exceeds the output dynamic range of the OM 6, the output value naturally deviates from the calculation result represented by the equation (10) or (18). Not only is it not possible to obtain a correct image, but there is a high possibility that the image will be worse than the state before the correction.

In the embodiment of FIG. 3, the value of the output K of the coefficient ROM 6 is determined by the equation (1)
0) or (18), Er and Eb are selected as the outputs of the switches 12 and 13 when the output is shifted from the calculation result represented by (18). Otherwise, ER2 and EB2 are selected. ER3 and ER3, which are the outputs of the switches 12 and 13, are not degraded as compared with the state before the correction.

An example of a method for detecting a state exceeding the output dynamic range of the coefficient ROM 6 will be described below.
For example, it is assumed that the output bit width of the coefficient ROM 6 is 8 bits, and that the case where all 8 bits are 1 is defined to indicate the maximum output. Equation (10) or (1
If the result of the operation according to 8) exceeds the output dynamic range of the coefficient ROM 6, the ROM table is configured to output all 8 bits of 1. The dynamic range discriminating circuit 14 discriminates between the case where the output values of the coefficient ROM 6 are all 1 and other cases, and outputs a discrimination signal when all the values are 1 as exceeding the output dynamic range of the coefficient ROM 6. And 13 switching control.

FIG. 4 is a block diagram showing an example of a video signal reproduction processor to which the color signal processor of the embodiment of FIG. 1 is actually applied. The low-frequency modulated color signal and the FM-modulated luminance signal recorded on the magnetic tape are extracted by the magnetic head 22, amplified by the reproducing amplifier 23, and digitally modulated by the analog / digital converter (A / D converter) 24. Signal and a digital FM modulated luminance signal, and the digital FM signal is converted by a high-pass filter (HPF (LPF) 25).
A luminance signal is extracted, demodulated by an FM demodulator 26, passed through a low-pass filter (LPF) 27,
The analog signal is converted by an analog converter (D / A converter) 28 and supplied to an adder 29. Also, a low-pass modulation chroma signal is extracted by a low-pass filter (LPF) 30 from a digital low-pass modulation color signal and a digital FM modulation luminance signal output from an analog / digital converter (A / D converter) 24. The operation described above has already been performed by the color signal processing circuit (herein, F1 shown) disclosed in FIG. 1, the output of which is supplied to the encoder 31, and the fsc modulation using the color carrier frequency fsc of the television signal as a modulation carrier The signal is modulated into a color signal, passes through a band-pass filter (BPF) 32, is converted into an analog signal by a digital / analog converter (D / A converter) 33, and is supplied to an adder 29 to obtain a desired output signal.

[0045]

According to the present invention, only the coefficient ROM 6 is used as the ROM, and three ROMs need not be used as in the prior art, so that the circuit scale can be reduced. However, the operation of the coefficient ROM 6 can correct the adverse effect of the shift angle of the demodulation axis.
Depending on the calculation of 6, it is also possible to correct for amplitude fluctuations.

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of the present invention.

FIG. 2 is a block diagram of another embodiment of the present invention.

FIG. 3 is a block diagram of another embodiment of the present invention.

FIG. 4 is a block diagram showing an example of a video signal reproduction processing device to which the color signal processing device according to the embodiment of FIG. 1 is actually applied;

FIG. 5 is a block diagram of a conventional embodiment.

FIG. 6 is a diagram showing a relationship between a demodulation axis of the decoder 1 of FIG. 5 and a decoder output signal.

[Explanation of symbols]

1—decoder 2, 3—burst detection means 4, 5—calculation means 6—coefficient ROM 7, 8—multiplier 9, 10—amplifier,
11—dynamic range discriminating circuit, 12, 13—switch.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshihide Takahashi 1410 Inada, Hitachinaka-shi, Ibaraki Pref. Digital Media Products Division, Hitachi, Ltd. (72) Katsuyuki Watanabe 1410 Inada, Inada, Hitachinaka-shi, Ibaraki Hitachi, Ltd. (72) Inventor Hideo Kadoya 1410 Inada, Hitachinaka-shi, Ibaraki F-term (reference) Digital Media Products Division, Hitachi, Ltd. 5C055 AA01 AA08 DA01 EA01 EA04 FA09 GA00 HA12 HA31 HA37 5C066 AA03 AA07 BA02 CA17 DB07 DC07 DD07 DD08 EB01 EC06 GA02 GA16 HA03 KA13 KD06 KD08 KE01 KE02 KE03 KE09 KE19 KE20 KF03 KG01

Claims (5)

[Claims] 1. Detection of burst amplitude Ar of RY component Er of baseband color signal and B-
Burst detection means for detecting the burst amplitude Ab of the Y component Eb, first arithmetic means for receiving the values of Er, Eb, Ar and Ab and multiplying and adding / subtracting these values; A second calculating means for inputting a value and outputting a coefficient K represented by the following equation, wherein the coefficient K is represented by (Ar ² + Ab ² ); and multiplying the calculation result of the first calculating means by the coefficient K A color signal processing device comprising: 2. The detection of the burst amplitude Ar of the RY component Er of the baseband color signal and the B-
Burst detection means for detecting the burst amplitude Ab of the Y component Eb, first arithmetic means for receiving the values of Er, Eb, Ar and Ab and multiplying and adding / subtracting these values; The value is input, and the coefficient K = k1 / (√ (Ar ² + Ab ² )) where k1
Is a color signal processing device comprising: a second calculating means for outputting a coefficient K represented by a constant; and a multiplier for multiplying the calculation result of the first calculating means by the coefficient K. 3. The detection of the burst amplitude Ar of the RY component Er of the baseband color signal and the B-
Burst detection means for detecting the burst amplitude Ab of the Y component Eb; first calculation means for receiving the values of Er, Eb, Ar, and Ab and multiplying and adding / subtracting these values; A value is input, and the coefficient K = k2 / (Ar ² + Ab ² ), where k2 is a second calculating means for outputting a coefficient K represented by a constant, and the coefficient K is added to the calculation result of the first calculating means. A color signal processing device comprising: 4. A switch according to claim 1, wherein the output of the multiplier is input to one input and the Er and Eb are input to the other input, and one of the switches is output. Means, the output dynamic range of the coefficient K output by the second arithmetic means is determined, and the value of K greatly exceeds the output dynamic range of the second arithmetic means, and the second arithmetic means And a discrimination control means for controlling the selection of the Er and Eb as the output of the switch means when a calculation result substantially matching the above equation cannot be output as the output of the color signal processing apparatus. . 5. A magnetic head for extracting a low-frequency modulated color signal recorded on a magnetic tape, an analog / digital converter for converting the low-frequency modulated color signal into a digital low-frequency modulated color signal, and the digital low-frequency signal. A low-pass filter for extracting a low-frequency modulated chroma signal from the modulated color signal; and demodulating the low-frequency modulated color signal to output a baseband color signal represented by an RY component Er and a BY component Eb. A decoder, a burst detecting means for detecting a burst amplitude Ar of the RY component Er and a burst amplitude Ab of the BY component Eb, and input values of Er, Eb, Ar, Ab, a first arithmetic means for multiplying and subtraction process these, the Ar, the second to the value of the Ab is inputted, the coefficient K and outputs the coefficient K represented by the associated expression in (Ar ² + Ab ²⁾ Calculating means and said first color signal reproducing apparatus characterized by comprising a multiplier for multiplying the coefficient K in the calculation result of the calculating means.