Abstract:
A chrominance signal processing apparatus in a video signal processing system which has a simple configuration capable of achieving chrominance signal control and RGB transform functions using a single circuit. The chrominance signal processing apparatus includes a key input unit provided with a plurality of control keys for chrominance signal controls, the key input unit serving to generate key data in response to a manipulation of desired control keys by the user, a chrominance signal control coefficient computing unit adapted to calculate chrominance signal control coefficients in response to a user&#39;s request for chrominance signal controls received via the key input unit, respectively, the calculation of the chrominance signal control coefficients being carried out in accordance with a matrix computation for variations in chrominance signal coefficients respectively associated with the chrominance signal control coefficients to be calculated, and a chrominance signal control and RGB transform unit adapted to conduct the requested chrominance signal controls for chrominance signals separated from a video signal, along with a luminance signal, by a comb filter of the video signal processing system, based on the chrominance signal control coefficients received from the chrominance signal control coefficient computing unit, and adding the controlled chrominance signals to the luminance signal, respectively, thereby outputting R, G, and B video signals.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a video signal processing system, and more particularly to a chrominance signal processing apparatus in a video signal processing system. This application is based on Korean patent application 98-57167, which is hereby incorporated by reference for all purposes. 
     2. Description of the Related Art 
     Generally, video signal processing systems include, for example, color televisions, video cassette tape recorders, and video color printers. In such a video signal processing system, a composite video signal is divided into a luminance signal and a chrominance signal. The chrominance signal is then processed by various processes such as a color gain control, a color hue control, and flesh tone control, etc. After being processed by such processes, the resultant chrominance signal is transformed, along with the luminance signal, to an original RGB signal which is, in turn, output. To this end, the video signal processing system should be equipped with not only a circuit for transforming the luminance and chrominance signals to an RGB signal format, but also a variety of chrominance signal control circuits for conducting various controls for the chrominance signal including a color gain control, a color hue control, and flesh tone control, etc. according to the user&#39;s intention. 
     FIG. 1 is a block diagram schematically illustrating a digital color television receiver which is a video signal processing system as mentioned above. Referring to FIG. 1, a plurality of channels carrying television video signals are received by tuner  100  via an antenna  118 . The tuner  100  allows a user to select a channel from a plurality of channels, and outputs the television video signals of the selected channel to an intermediate frequency (IF) demodulator  102 . The IF demodulator  102  demodulates the television video signal received therein into an IF signal which is sent to an analog/digital (A/D) converter  104 . In the A/D converter  104 , the video signal outputted from the IF demodulator  102  in the IF-modulated state is converted to a digital signal using binary-sampling in a pulse code modulation (PCM) fashion. A comb filter  106  receives the digital data from the A/D converter  104  and separates a luminance signal Y and a chrominance signal C from the received digital data. The chrominance signal C from the comb filter  106  is applied to a chrominance signal demodulator  108  which demodulates the received chrominance signal C into an R-Y chrominance signal Cr and a B-Y chrominance signal Cb. A color gain controller  110  receives the chrominance signals Cr and Cb from the chrominance signal demodulator  108 , conducts a color gain control for those received signals, and outputs the resultant signals, namely, gain-controlled chrominance signals Cb_g and Cr_g, to a color hue controller  112 . The color hue controller  112  controls the gain-controlled chrominance signals Cb_g and Cr_g in accordance with a color hue control coefficient, and then outputs the resultant signals, namely, hue-controlled chrominance signals Cb_h and Cr_h, to a flesh tone controller  114 . In the flesh tone controller  114 , the hue-controlled chrominance signals Cb_h and Cr_h are controlled in terms of flesh tone in accordance with a flesh tone control coefficient. The resultant signals, namely, flesh tone-controlled chrominance signals Cb_f and Cr_f, are applied to an RGB transform unit  116 . The RGB transform unit  116  processes the flesh tone-controlled chrominance signals Cb_f and Cr_f along with the luminance signal Y, thereby transforming these signals to an original RGB signal which is finally outputted. 
     FIGS. 2,  4 , and  6  illustrate detailed circuit configurations of the color gain controller  110 , color hue controller  112  and flesh tone controller  114 , respectively. Now, the operations of these controllers will be described in more detail, in conjunction with FIGS. 2,  4 , and  6 . 
     FIG. 2 is a block diagram illustrating a detailed circuit configuration of the color gain controller  110 . As shown in FIG. 2, the color gain controller  110  multiplies the chrominance signals Cb and Cr received from the chrominance signal demodulator  108  of FIG. 1 by a color gain control coefficient G received from a multiplier  200 , respectively. That is, the color gain controller  110  serves to vary the value of a vector A representing the chrominance signal C in proportion to the gain control coefficient G, as shown in FIG. 3 illustrating a color vector diagram of the chrominance signal C with the chrominance signal Cb as an abscissa and the chrominance signal Cr as an ordinate. The values of output signals from the color gain controller  110  respectively associated with the luminance signal Y and chrominance signals Cb and Cr can be expressed as follows: 
     
       
         
           Y=Y 
         
       
     
     
       
         
           Cb 
           — 
           g=Cb×G 
         
       
     
     
       
           Cr   —   g=Cr×G   [Equation 1] 
       
     
     The above Equation 1 may be expressed in the form of a matrix equation as follows:                [         Y           Cb_g           Cr_g         ]     =       [         1       0       0           0       G       0           0       0       G         ]     ×     [         Y           Cb           Cr         ]               [Equation  1a]                                
     In the above Equation 1a, “Cb” represents a normalized value of the B-Y chrominance signal, “Cr” represents a normalized value of the R-Y chrominance signal, and “G” represents the color gain control coefficient. 
     FIG. 4 is a block diagram illustrating a detailed circuit configuration of the color hue controller  112 . As shown in FIG. 4, the color hue controller  112  serves to rotate or shift the coordinate axes of the chrominance signals Cb and Cr, as shown in FIG. 5, thereby achieving a variation in color. The hue of the chrominance signals Cb and Cr, which is the color represented by the color vector A, as shown in FIG. 5, may often be unacceptable to the viewer due to an inadequate chrominance signal phase sampling or a particular visual response of the viewer. In such a case, the viewer adjusts the hue of the chrominance signals Cb and Cr by varying the rotation angle or phase angle of the color vector A, while observing the display state of the television receiver, until a desired hue is obtained. In accordance with a viewer&#39;s adjustment of the hue, the coordinate axes of the chrominance signals Cb and Cr are rotated or shifted, thereby controlling the hue of the color vector A. 
     When the viewer shifts the coordinate axes of the chrominance signals Cb and Cr by an angle of θ in order to obtain a desired hue, the color hue control coefficient is set to “θ”. In this case, a color hue control coefficient value of “cos θ” or “−sin θ” is input to the color hue controller  112  via a first switch  402  which is coupled to the values “cos θ” and “−sin θ,” associated with the chrominance signals Cb and Cr, respectively. Another color hue control coefficient value of “sin θ” or “cos θ” is input to the color hue controller  112  via a second switch  408  which is coupled to the values “sin θ” and “cos θ,” associated with the chrominance signals Cb and Cr, respectively. In a first multiplier  400 , the chrominance signal Cb, which is input to the color hue controller  112 , is multiplied by “cos θ” applied to the first multiplier  400  in accordance with a switching operation of the first switch  402 . The resultant value from the first multiplier  400  is stored in a first delay  404 . In a second multiplier  406 , the input chrominance signal Cb is also multiplied by “sin θ” applied to the second multiplier  406  in accordance with a switching operation of the second switch  408 . The resultant value from the second multiplier  406  is stored in a second delay  410 . After completing the multiplication operations for the input chrominance signal Cb, multiplication operations for the input chrominance signal Cr are conducted in the first and second multipliers  400  and  406  using values of “−sin θ” and “cos θ,” respectively. After performing the multiplication operation for the input chrominance signal Cr, the resultant product value is outputted from the first multiplier  400  and inputted into a first adder  412  which adds the product value to the value received from the first delay  404 , having the input chrominance signal Cb. The resultant value from the first adder  412  is applied to a first input terminal of a third switch  414 . Also, after the multiplication operation for the input chrominance signal Cr, the resultant value is outputted from the second multiplier  406  and applied to a second adder  416  which, in turn, adds this value to the value received from the second delay  410 , having the input chrominance signal Cb. The resultant value from the second adder  416  is applied to the second input terminal of the third switch  414 . Thus, hue-controlled chrominance signals Cb_h and Cr_h are sequentially output in accordance with a switching operation of the third switch  414 . The respective values of the output signals from the color hue controller  112  associated with the luminance signal Y and the chrominance signals Cb and Cr can be expressed as follows: 
     
       
         
           Y=Y 
         
       
     
     
       
           Cb   —   h=Cb ×cos θ− Cr ×sin θ 
       
     
     
       
           Cr   —   h=Cb ×sin θ+ Cr ×cos θ  [Equation 2] 
       
     
     The above Equation 2 may be expressed in the form of a matrix equation as follows:                [         Y           Cb_h           Cr_h         ]     =       [         1       0       0           0         cos                 θ             -   sin                   θ             0         sin                 θ           cos                 θ           ]     ×     [         Y           Cb           Cr         ]               [Equation  2a]                                
     In the above Equation 2a, “θ” represents the shift angle of the coordinate axes. 
     FIG. 6 is a block diagram illustrating a detailed circuit configuration of the flesh tone controller  114 . As shown in FIG. 6, the flesh tone controller  114  serves to correct colors near the skin color. When the phase angle of the coordinate axis of the chrominance signal Cr is shifted by an angle of θ′, the flesh tone control coefficient used in the flesh tone controller  114  is set to “θ′”. In this case, a flesh tone control coefficient value of “sin θ′” or “cos θ′” is input to the flesh tone controller  114  via a first switch  600  which is coupled to those values “sin θ′” and “cos θ′” associated with the chrominance signals Cb and Cr, respectively. Since the flesh tone controller  114  is adapted to only shift the coordinate axis of the chrominance signal Cr, the chrominance signal Cb, which is inputted to the flesh tone controller  114 , is directly applied to a first input terminal of a second switch  602 . The chrominance signal Cb is selectively outputted from the flesh tone controller  114 , without being changed, in accordance with a switching operation of the second switch  602 . The input chrominance signal Cb is also applied to a multiplier  604 . In the multiplier  604 , the input chrominance signal Cb is multiplied by “sin θ′” applied to the multiplier  604  in accordance with a switching operation of the first switch  600 . The resultant value outputted from the multiplier  604  is stored in a delay  606 . Subsequently, the chrominance signal Cr, is inputted into the flesh tone controller  114 , following the chrominance signal Cb, and is multiplied by “cos θ′” in the multiplier  604 . The resultant value output from the multiplier  604  after the multiplication operation for the input chrominance signal Cr is then applied to an adder  608  for adding to it the value received from the delay  606  associated with the input chrominance signal Cb. The resultant value from the adder  608  is applied to the second input terminal of the second switch  602 . The second switch  602  successively outputs from the flesh tone controller  114  the value received from the adder  608  along with the chrominance signal Cb not processed in the flesh tone controller. 
     The output signal values from the flesh tone controller  114  associated with the luminance signal Y and chrominance signals Cb and Cr, respectively, can be expressed as follows: 
       Y=Y   
     
       
         
           Cb 
           — 
           f=Cb 
         
       
     
     
       
           Cr   —   f=Cb ×sin θ′+ Cr ×cos θ′  [Equation 3] 
       
     
     The above Equation 3 may be expressed in the form of a matrix equation as follows:                [         Y           Cb_f           Cr_f         ]     =       [         1       0       0           0       1       0           0         sin                   θ   ′             cos                   θ   ′             ]     ×     [         Y           Cb           Cr         ]               [Equation  3a]                                
     FIG. 8 is a block diagram illustrating a detailed circuit configuration of the RGB transform unit  116 . As shown in FIG. 8, the RGB transform unit  116  processes the chrominance signals Cb_f and Cr_f received from the flesh tone controller  114  along with the luminance signal Y, thereby transforming those signals to an original RGB signal in a conventional fashion. The resultant signals, namely, R, G and B signals, from the RGB transform unit  116  are then sent to the television receiver. That is, the chrominance signal Cr, which is input to the RGB transform unit  116 , is multiplied by a gain control coefficient R_GAIN for R-Y chrominance signals in a first multiplier  800 . The resultant signal from the first multiplier  800  is applied to a first adder  802  which, in turn, adds that signal to the luminance signal Y applied thereto. The resultant signal from the first adder  802  is output as the R (red) signal. The input chrominance signal Cr is also applied to a second multiplier  808 . In the second multiplier  808 , the input chrominance signal Cr is multiplied by “R_COEF” applied to the second multiplier  808  via a switch  810 . The switch  810  is coupled to chrominance signal control coefficients of “R_COEF” and “B_COEF” for G (green) color values respectively associated with the chrominance signals Cr and Cb in order to selectively apply “R_COEF” or “B_COEF” to the second multiplier  808  in accordance with its switching operation. The resultant value from the second multiplier  808  is stored in a delay  812 . The input chrominance signal Cr is also applied to a third multiplier  804  which, in turn, multiplies the input chrominance signal Cr by a gain control coefficient B_GAIN for B-Y chrominance signals. The resultant signal from the third multiplier  804  is applied to a third adder  806  which, in turn, adds that signal to the luminance signal Y applied thereto. The resultant signal from the third adder  806  is prevented from being output as the B (blue) signal in accordance with a switching operation of a switch (not shown). Subsequently, the chrominance signal Cb, which is inputted into the RGB transform unit  116 , following the chrominance signal Cr, is applied to the multipliers  800 ,  808 , and  804 , respectively. Although the input chrominance signal Cb applied to the first multiplier  800  is processed in the same manner as that for the chrominance signal Cr applied to the first multiplier  800 , its resultant signal is prevented from being outputted from the first adder  802  as the R (red) signal. The input chrominance signal Cb applied to the second multiplier  808  is multiplied by “B_COEF” applied to the second multiplier  808  via the switch  810 . The resultant value from the second multiplier  808  is then applied to a fourth adder  814  which, in turn, adds that value to the value received from the delay  812  associated with the input chrominance signal Cr. The resultant value from the fourth adder  814  is applied to a second adder  816 . In the second adder  816 , the signal output from the fourth adder  814  is added to the luminance signal Y applied to the second adder  816 . The resultant signal from the second adder  816  is outputted as the G (green) signal. Meanwhile, the input chrominance signal Cb applied to the third multiplier  804  is processed in the same manner as that for the input chrominance signal Cr applied to the third multiplier  804 . The resultant signal from the third adder  806  is output as the B (blue) signal. Accordingly, the R, G, and B signals output from the RGB transform unit  116  can be expressed as follows: 
     
       
           R=Y+R _GAIN×Cr 
       
     
     
       
           G=Y+B _COEF×Cb+R_COEF×Cr 
       
     
     
       
           B=Y+B _GAIN× Cb   [Equation 4] 
       
     
     The above Equation 4 may be expressed in the form of a matrix equation as follows:                [         R           G           B         ]     =       [         1       0       R_GAIN           1       B_COEF       R_COEF           1       B_GAIN       0         ]     ×     [         Y           Cb           Cr         ]               [Equation  4a]                                
     As apparent from the above description, conventional video signal processing devices are equipped with respective circuits for the chrominance signal control and RGB transform functions. When one desires to add another function, it is necessary to provide an additional circuit for performing the added function. For instance, when it is desired to add another chrominance signal control function, a chrominance signal control circuit for the added chrominance signal control function must be provided. Due to the need for an additional chrominance signal control circuit, the entire circuit configuration becomes complex. Furthermore, additional components increase the cost of producing a device. 
     SUMMARY OF THE INVENTION 
     Accordingly, an object of the invention is to provide a chrominance signal processing apparatus in a video signal processing system which has a simple configuration capable of achieving chrominance signal control and RGB transform functions using a single circuit. 
     In accordance with the present invention, this object is accomplished by providing a chrominance signal processing apparatus in a video signal processing system comprising: a key input unit provided with a plurality of control keys for chrominance signal controls, the key input unit serving to generate key data in response to a manipulation of desired control keys by the user; a chrominance signal control coefficient computing unit adapted to calculate chrominance signal control coefficients in response to a user&#39;s request for chrominance signal controls received via the key input unit, respectively, the calculation of the chrominance signal control coefficients being carried out in accordance with a matrix computation for variations in chrominance signal coefficients respectively associated with the chrominance signal control coefficients to be calculated; and a chrominance signal control and RGB transform unit adapted to conduct the requested chrominance signal controls for chrominance signals separated from a video signal, along with a luminance signal, by a comb filter of the video signal processing system, based on the chrominance signal control coefficients received from the chrominance signal control coefficient computing unit, and adding the controlled chrominance signals to the luminance signal, respectively, thereby outputting R, G, and B video signals. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing and other objects, features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which: 
     FIG. 1 is a block diagram schematically illustrating a digital color television receiver; 
     FIG. 2 is a block diagram illustrating a detailed circuit configuration of a color gain controller shown in FIG. 1; 
     FIG. 3 is a color vector diagram of a color gain-controlled chrominance signal; 
     FIG. 4 is a block diagram illustrating a detailed circuit configuration of a color hue controller shown in FIG. 1; 
     FIG. 5 is a color vector diagram of a color hue-controlled chrominance signal; 
     FIG. 6 is a block diagram illustrating a detailed circuit configuration of a flesh tone controller shown in FIG. 1; 
     FIG. 7 is a color vector diagram of a flesh tone-controlled chrominance signal; 
     FIG. 8 is a block diagram illustrating a detailed circuit configuration of a conventional RGB transform unit shown in FIG. 1; 
     FIG. 9 is a block diagram illustrating a digital television receiver equipped with a chrominance signal processing apparatus configured in accordance with an embodiment of the present invention; and 
     FIG. 10 is a block diagram illustrating a detailed configuration of the chrominance signal processing apparatus shown in FIG.  9 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Reference will now be made in greater detail to the preferred embodiments of the present invention. In the following description, made in conjunction with a preferred embodiment of the present invention, a variety of specific elements such as concrete processing flows are described. The description of such elements is made only to provide a better understanding of the present invention. Those skilled in the art will appreciate that the present invention can be implemented without using the above mentioned specific elements. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein is omitted. 
     FIG. 9 is a block diagram illustrating a digital television receiver equipped with a chrominance signal processing apparatus configured to conduct both color signal control and RGB transform functions in accordance with an embodiment of the present invention. Referring to FIG. 9, a key input unit  905  is provided with a plurality of control keys for adjusting a variety of color signals. In response to a user&#39;s manipulation of selected control keys, the key input unit  905  generates key data. A chrominance signal control coefficient computing unit  904  calculates chrominance signal control coefficients in response to control signals inputted in accordance with a user&#39;s manipulations of the desired control keys of the key input unit  905 . In the chrominance signal control coefficient computing unit  904 , the calculation of chrominance signal control coefficients is carried out in accordance with a matrix computation. The array of numbers in the matrix correspond to variations in chrominance signal coefficients associated with the chrominance signal control coefficients used in subsequent calculations. The calculated chrominance signal control coefficients are applied to a chrominance signal control and RGB transform unit  902 . The chrominance signal control coefficient computing unit  904  may comprise a micro computer or computing circuit. The chrominance signal control coefficients generated in accordance with the matrix computation conducted in the chrominance signal control coefficient computing unit  904 , for variations in chrominance signal coefficients and associated chrominance signal control coefficients, are the same as those obtained using conventional circuits. This will now be verified by comparing the results obtained when the chrominance signal coefficients are computed using the matrix computation with the results obtained when the chrominance signals Cb and Cr are sequentially processed by chrominance signal control units, such as the color gain controller  110 , color hue controller  112 , and flesh tone controller  114  shown in FIG.  1 . 
     First, a description is provided for the equation representing the output obtained from sequentially processing the chrominance signals, Cb and Cr, received from the comb filter  106  of FIG. 1, by the chrominance signal controllers of FIG.  1 . In the final step, an RGB transform is performed on signals outputted from the last processing unit of the chrominance signal controllers. 
     As in Equation 1, the values of signals outputted from the color gain controller  110 , which represent a color gain control conducted on the chrominance signals Cb and Cr, are expressed as follows, along with the luminance signal Y: 
     
       
         
           Y=Y 
         
       
     
     
       
         
           Cb 
           — 
           g=Cb×G 
         
       
     
     
       
           Cr   —   g=Cr×G   [Equation 5] 
       
     
     Next, Equation 6 represents the values of signals outputted from the color hue controller  112 , which represents the color hue control conducted at a variation in hue of θ, performed on the color gain-controlled chrominance signals Cb_g and Cr_g output from the color gain controller  110 . The luminance signal Y is also shown. 
     
       
         
           Y=Y 
         
       
     
     
       
           Cb   —   h=Cb   —   g ×cos θ− Cr   —   g ×sin θ 
       
     
     
       
           Cr   —   h=Cb   —   g ×sin θ+ Cr   —   g ×cos θ  [Equation 6] 
       
     
     Equation 6 can be expressed in accordance with the chrominance signals Cb and Cr output from the comb filter  106 , as follows: 
     
       
         
           Y=Y 
         
       
     
     
       
           Cb   —   h=G×Cb ×cos θ− G×Cr ×sin θ 
       
     
     
       
           Cr   —   h=G×Cb ×sin θ+ G×Cr ×cos θ  [Equation 7] 
       
     
     The values of output signals from the flesh tone controller  114 , resulting from a flesh tone control conducted at a shift angle θ′ of the Cr coordinate axis for the color hue-controlled chrominance signals Cb_g and Cr_g, received from the color gain controller  110  is expressed in Equation 8. The luminance signal Y is also shown. 
       Y=Y   
     
       
         Cb —   f=Cb   —   h   
       
     
     
       
         Cr —   f=Cb   —   h ×sin θ′+ Cr   —   h ×cos θ′  [Equation 8] 
       
     
     When the terms of Equation 8 are replaced with corresponding terms of Equation 7, Equation 8 can be expressed in accordance with the chrominance signals Cb and Cr output from the comb filter  106 , as follows:              Y   =   Y           [     Equation                 9     ]               Cb_f   =     Cb_h   =       G   ×   Cb   ×   cos                 θ     -     G   ×   Cr   ×   sin                 θ                                       Cr_f   =                  Cb_h   ×   sin                   θ   ′       +     Cr_h   ×   cos                   θ   ′                     =                    (       G   ×   Cb   ×   cos                 θ     -     G   ×   Cr   ×   sin                 θ       )        sin                   θ   ′       +                                (       G   ×   Cb   ×   cos                 θ     -     G   ×   Cr   ×   sin                 θ       )        cos                   θ   ′                   =                    G        (       sin                   θ   ′        cos                 θ     +     cos                   θ   ′        sin                 θ       )          Cb     +                                G        (       cos                   θ   ′        cos                 θ     -     sin                   θ   ′        sin                 θ       )          Cr                 =                    G   ·     sin        (     θ   +     θ   ′       )            Cb     +       G   ·     cos        (     θ   +     θ   ′       )            Cr                                                      
     The chrominance signals Cb_f and Cr_f, resulting from the above mentioned flesh tone control and the luminance signal Y, are subject to an RGB transform in the RGB transform unit  116  of FIG.  1 . With the terms “G·cos θ”, “−G·sin θ”, “G·sin(θ+θ′)”, and “G·cos(θ+θ′)” of Equation 9 are replaced by “A”, “B”, “C”, and “D”, respectively, the values of R, G and B signals output from the RGB transform unit  116  can be expressed as follows:                    R   =                Y   +     R_GAIN   ×   Cr_f                   =                Y   +     R_GAIN        (       C   ·   Cb     +     D   ·   Cr       )                     =                Y   +     C   ×   R_GAIN   ×   Cb     +     D   ×   R_GAIN   ×   Cr                     [     Equation                 10     ]                     G   =                Y   +     B_COEF   ×   Cb_f     +     R_COEF   ×   Cr_f                   =                Y   +     B_COEF   ×     (       A   ·   Cb     +     B   ·   Cr       )       +     R_COEF   ×                                (       C   ·   Cb     +     D   ·   Cr       )                 =                Y   +       (       A   ×   B_COEF     +     C   ×   R_COEF       )        Cb     +                                (       B   ×   B_COEF     +     D   ×   R_COEF       )        Cr                                         B   =                Y   +     B_GAIN   ×   Cb_f                   =                Y   +     B_GAIN   ×     (       A   ·   Cb     +     B   ·   Cr       )                     =                Y   +     A   ×   B_GAIN   ×   Cb     +     B   ×   B_GAIN   ×   Cr                                                      
     Equation 11 verifies that the results obtained in accordance with a matrix computation for the coefficients used in the above mentioned chrominance signal controllers are the same as the values of R, G and B signals obtained by sequentially processing the chrominance signals in the above mentioned chrominance signal controllers, and then conducting an RGB transform on signals output from the final one of those chrominance signal controllers. Equation 11 uses the coefficients of Equations 1a, 2a and 3a to conduct the above mentioned matrix computation:                      [         Y           Cb_f           Cr_f         ]     =                  [         1       0       0           0       1       0           0         sin                   θ   ′             cos                   θ   ′             ]     ×     [         1       0       0           0         cos                 θ             -   sin                   θ             0         sin                 θ           cos                 θ           ]     ×                                [         1       0       0           0       G       0           0       0       G         ]     ×     [         Y           Cb           Cr         ]                   =                  [         1       0       0           0           G   ·   cos                   θ               -   G     ·   sin                   θ             0         G   ·     sin        (     θ   +     θ   ′       )               G   ·     cos        (     θ   +     θ   ′′       )               ]     ×     [         Y           Cb           Cr         ]                     [     Equation                 11     ]                                
     After conducting a matrix computation for Equation 11, the following results are obtained: 
     
       
         
           Y=Y 
         
       
     
     
       
           Cb   —   f=G×Cb ×cos θ− G×Cr ×sin θ 
       
     
     
       
           Cr   —   f=G ·sin(θ+θ′) Cb+G ·cos(θ+θ′) Cr   [Equation 12] 
       
     
     It is found that Equation 12 is the same as Equation 9, which represents the values signal outputted from the flesh tone controller  114  of FIG.  1 . Equation 9 results from the flesh tone control conducted for the color hue-controlled chrominance signals Cb_g and Cr_g, and the chrominance signals Cb and Cr received from the comb filter Cb and Cr. 
     When the terms of Equation 4a are replaced with corresponding terms of Equation 11, wherein the terms “G·cos θ”, “−G·sin θ”, “G·sin(θ+θ′)”, and “G·cos(θ+θ′)” in Equation 11 are replaced with “A”, “B”, “C”, and “D”, respectively, the following Equation 13 is obtained:                      [         R           G           B         ]     =                  [         1       0       R_GAIN           1       B_COEF       R_COEF           1       B_GAIN       0         ]     ×     [         1       0       0           0       A       B           0       C       D         ]     ×     [         Y           Cb           Cr         ]                   =                  [         1         C   ×   R_GAIN           D   ×   R_GAIN             1           A   ×   B_COEF     +     C   ×   R_COEF               B   ×   B_COEF     +     D   ×   R_COEF               1         A   ×   B_GAIN           B   ×   B_GAIN           ]     ×                              [         Y           Cb           Cr         ]                   [     Equation                 13     ]                                
     After conducting a matrix computation for Equation 13, the following results are obtained: 
     
       
           R=Y+C×R _GAIN× Cb+D×R _GAIN× Cr   
       
     
     
       
           G=Y +( A×B _COEF+ C×R _COEF) Cb +( B×B _COEF+ D×R _COEF) Cr   
       
     
     
       
           B=Y+A×B _GAIN× Cb+B×B _GAIN× Cr   [Equation 14] 
       
     
     It is found that Equation 14 is the same as Equation 10 representing the R, G and B signals finally output from the RGB transform unit  116  of FIG.  1 . 
     It is apparent from the above description that sequentially processing the chrominance signals in the above mentioned chrominance signal controllers and then conducting an RGB transform for signals outputted from the last processing unit provides results equivalent to those obtained in accordance with a matrix computation for variations of the coefficients respectively used in the above mentioned chrominance signal controllers in association with the luminance signal and chrominance signals. 
     Accordingly, it is verified that the chrominance signal control coefficient computing unit  904  produces respective control coefficients for appropriate chrominance signal controls in accordance with a matrix computation for variations of chrominance signal coefficients used to achieve those chrominance signal controls. Referring to FIG. 9, the chrominance signal control and RGB transform unit  902  conducts a chrominance signal control for the chrominance signals Cb and Cr received from the comb filter  106 , based on the chrominance signal control coefficients received from the chrominance signal control coefficient computing unit  904 . The chrominance signal control and RGB transform unit  902  then conducts an RGB transform for the resultant signals obtained after its chrominance signal control, along with the luminance signal Y, thereby outputting a video signal. 
     FIG. 10 illustrates a detailed circuit configuration of the chrominance signal control and RGB transform unit  902  of FIG. 9 in accordance with an embodiment of the present invention. As shown in FIG. 10, the chrominance signal Cb, which is inputted into the chrominance signal control and RGB transform unit  902 , is applied to a first multiplier  908 . In the first multiplier  908 , the input chrominance signal Cb is multiplied by a chrominance signal control coefficient “R_A” applied to the first multiplier  908  via a first switch  906 . The first switch  906  is coupled to chrominance signal control coefficients of “R_A” and “R_B” for R (red) color values respectively associated with the chrominance signals Cb and Cr in order to selectively apply “R_A” or “R_B” to the first multiplier  908  in accordance with its switching operation. The resultant value from the first multiplier  908  is stored in a first delay  910 . The input chrominance signal Cb is also applied to a second multiplier  918 . In the second multiplier  918 , the input chrominance signal Cb is multiplied by a chrominance signal control coefficient “G_A” applied to the second multiplier  918  via a second switch  916 . The second switch  916  is coupled to chrominance signal control coefficients of “G_A” and “G_B” for G (green) color values associated with the chrominance signals Cb and Cr, respectively, in order to selectively apply “G_A” or “G_B” to the second multiplier  918  in accordance with its switching operation. The resultant value from the second multiplier  918  is stored in a second delay  920 . The input chrominance signal Cb is also applied to a third multiplier  928 . In the third multiplier  928 , the input chrominance signal Cb is multiplied by a chrominance signal control coefficient “B_A” applied to the third multiplier  928  via a third switch  926 . The third switch  926  is coupled to chrominance signal control coefficients of “B_A” and “B_B” for B (blue) color values respectively associated with the chrominance signals Cb and Cr in order to selectively apply “B_A” or “B_B” to the third multiplier  928  in accordance with its switching operation. The resultant value from the third multiplier  928  is stored in a third delay  930 . 
     Subsequently, the chrominance signal Cr, which is input to the chrominance signal control and RGB transform unit  902 , following the chrominance signal Cb, is applied to the multipliers  908 ,  918 , and  928 , respectively. In the first multiplier  908 , the input chrominance signal Cr is multiplied by a chrominance signal control coefficient “R_B” applied to the first multiplier  908  via the first switch  906 . The resultant signal from the first multiplier  908  is applied to a first adder  912  which adds that signal to the value received from the first delay  910  and associated with the input chrominance signal Cr. The resultant signal from the first adder  912  is then applied to a second adder  914  which adds that value to the luminance signal Y applied thereto. The resultant signal from the second adder  914  is output as an R (red) signal. In the second multiplier  918 , the input chrominance signal Cr is multiplied by a chrominance signal control coefficient “G_B” applied to the second multiplier  918  via the second switch  916 . The resultant signal from the second multiplier  918  is applied to a third adder  922  which adds that signal to the value received from the second delay  920  and associated with the input chrominance signal Cr. The resultant signal from the third adder  922  is then applied to a fourth adder  924  which adds that value to the luminance signal Y applied thereto. The resultant signal from the fourth adder  924  is output as a G (green) signal. On the other hand, in the third multiplier  928 , the input chrominance signal Cr is multiplied by a chrominance signal control coefficient “B_B” applied to the third multiplier  928  via the third switch  926 . The resultant signal from the third multiplier  928  is applied to a fifth adder  932  which adds that signal to the value received from the third delay  930  and associated with the input chrominance signal Cr. The resultant signal from the fifth adder  932  is then applied to a sixth adder  934  which, in turn, adds that value to the luminance signal Y applied thereto. The resultant signal from the sixth adder  934  is output as a B (blue) signal. Assuming that the chrominance signal control coefficients “R_A”, “R_B”, “G_A”, “G_B”, “B_A”, and “B_B” correspond to “C×R_GAIN”, “D×R_GAIN”, “A×B_COEF+C×R_COEF”, “B×B_COEF+D×R_COEF”, “A×B_GAIN”, and “B x B_GAIN”, the R, G, and B signals output from the chrominance signal control and RGB transform unit  902  can be expressed as follows: 
     
       
           R=Y+C×R _GAIN× Cb+D×R _GAIN× Cr   
       
     
     
       
           G=Y +( A×B _COEF+ C×R _COEF) Cb +( B×B _COEF+ D×R _COEF) Cr   
       
     
     
       
           B=Y+A×B _GAIN× Cb+B×B _GAIN× Cr   [Equation 15] 
       
     
     It is shown that Equation 15 is the same as Equation 14. That is, it is found that the R, G, and B signals finally output from the chrominance signal processing apparatus are those reflecting variations of luminance and chrominance signal coefficients for color controls. 
     As apparent from the above description, it is possible to achieve both the chrominance signal control function and RGB transform function using a single chrominance signal processing unit in accordance with the present invention. Therefore, the hardware configuration for those functions is simplified, as compared to conventional configurations in which a variety of independent chrominance signal control circuits such as a color gain controller, a color hue controller, and a flesh tone controller should be used. 
     While this invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiment, rather, it is intended to cover various modifications within the spirit and scope of the appended claims. For instance, although the preferred embodiment of the present invention has been described in conjunction with chrominance signal control functions, namely, a color gain control, a color hue control, and a flesh tone control, along with an RGB transform function, the present invention may be equivalently applied to a case in which gain controls for a luminance signal are achieved.