Abstract:
A dynamic motion degree of a video composite signal is estimated. A chrominance signal after Y/C separation and chrominance demodulation is narrow-band low pass filtered (NBLPF) and wide-band low pass filtered (WBLPF), so as to generate a narrow-band filtered signal and a wide-band filtered signal. The narrow-band filtered signal and the wide-band filtered signal are weighted based on the estimated dynamic motion degree, so as to determine how much high frequency component of the chrominance signal is reserved. In the static image processing, more high frequency component is reserved, so as to reduce the color transition issue and keep the image color being sharp. In the dynamic image processing, more high frequency component is filtered, so as to reduce the cross color issue.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority benefit of Taiwan application serial no. 95127071, filed on Jul. 25, 2006. All disclosure of the Taiwan application is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a self-adaptive image processing device and a processing method capable of determining how much high frequency component of the image is reserved according to the motion degree of the image. 
     2. Description of Related Art 
     Watching TV has become one of the entertainments for modern people. Generally speaking, the type of a video composite signal received by the TV set varies depending upon the difference of the definition of the color space. For example, in the YUV color space, the video composite signal includes a luminance component (Y), and a color information component (U and V), and the video composite signal is expressed as: Y+U sin(ωt)+V cos(ωt). In the YCbCr color space, the video composite signal includes a luminance component (Y), and a chrominance component (Cb and Cr), and the video composite signal is expressed as: Y+Cb sin(ωt)+Cr cos(ωt). In the YIQ (I; in-phase, Q: quadrature) color space, the video composite signal includes a luminance component (Y), and a color component (I and Q), and the video composite signal is expressed as: Y+Q sin(ωt+33°)+I cos(ωt+33°). Generally speaking, Y video component is a luminance signal, and the U, V, Cb, Cr, I, Q and the like, which are not the luminance signal, are all called the chrominance signal. 
     When the TV set receives the video composite signal, it is required to separate the luminance component Y from the color information component U/V (or chrominance component Cb/Cr, color component I/Q) and demodulate the color information component U/V. However, the color information component U/V (or chrominance component Cb/Cr, color component I/Q) after demodulation includes a baseband component and a high frequency component. 
     For example, in the YUV color space, the baseband component and the high frequency component of the color information component U/V after demodulation are expressed as follows:
 
(( U  sin( wt )+ V  cos( wt ))*(2 sin( wt ))= U−U  cos(2 wt )+ V  sin(2 wt )  (1);
 
(( U  sin( wt )+ V  cos( wt ))*(2 cos( wt ))= V+V  cos(2 wt )+ U  sin(2 wt )  (2).
 
     In Equation (1), U represents the baseband component of the U component, and (−U cos(2wt)+V sin(2wt)) represents the high frequency component of the U component. Similarly, in Equation (2), V represents the baseband component of the V component, and V cos(2wt)+U sin(2wt) represents the high frequency component of the V component. 
     Currently, the low pass filter is used to remove the high frequency component. If a narrow-band low pass filer, suitable for processing dynamic images, is used in the static image processing, the color transition problem occurs, and the color is not sharp enough, because most of the high frequency component of the color is filtered. On the other aspect, if a wide-band low pass filter, suitable for processing static images, is used in the dynamic image process, the cross color problem occurs. 
     Therefore, a self-adaptive device and method for dynamically adjusting the color bandwidth is required, thus, in the static image processing, the color transition issue is reduced and the color is kept sharp; in the dynamic image processing, the cross color issue is reduced. 
     SUMMARY OF THE INVENTION 
     In order to resolve the above problems, the present invention provides a self-adaptive image processing device and a method, so as to process static images and dynamic images appropriately. In the static image processing, more high frequency component of the image is reserved. In the dynamic images processing, more high frequency component of the image is filtered. 
     Moreover, the present invention provides a self-adaptive image processing device and a method, wherein in the static image processing, the color transition issue is reduced, and the color of the image is kept sharp; in the dynamic image processing, the cross color issue is reduced. 
     In order to achieve the objective of the present invention, the present invention provides an image processing device, which comprises a dynamic estimating unit, for estimating a dynamic motion degree of a video composite signal so as to output a motion factor; a first low pass filter and a second low pass filter, for receiving a chrominance signal and performing a low pass filtering to generate a first filtered signal and a second filtered signal, wherein the chrominance signal represents a chrominance component of the video composite signal after a luminance/chrominance separation and a demodulation; and a weighting unit, for weighting the first filtered signal and the second filtered signal according to the motion factor, so as to determine how much high frequency component of the chrominance signal is reserved. 
     Moreover, the present invention also provides an image processing method, suitable for filtering a chrominance component of a video composite signal, the chrominance component being obtained after a luminance/chrominance separation and a demodulation of the video composite signal. The method comprises the following steps. A dynamic feature of the video composite signal is estimated; a first filtering and a second filtering are performed to the chrominance component of the video composite signal; and the results of the first and second filtering processes are weighted according to the dynamic feature, so as to determine how much high frequency component of the chrominance component of the video composite signal is filtered. 
     In order to make aforementioned and other objects, features and advantages of the present invention comprehensible, preferred embodiments accompanied with figures are described in detail below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a circuit block diagram of a self-adaptive image processing device according to a preferred embodiment of the present invention. 
         FIG. 2  is a circuit block diagram of a dynamic estimating unit of  FIG. 1 . 
         FIG. 3  is a circuit block diagram of a frame difference estimating unit of  FIG. 2 . 
         FIG. 4  shows a look-up table of  FIG. 1  and  FIG. 2 . 
         FIG. 5   a  is a schematic view of a narrow-band low pass filter. 
         FIG. 5   b  is a schematic view of a wide-band low pass filter. 
         FIG. 6  is a schematic view of a weighting unit of  FIG. 1 . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     In order to appropriately process static images and dynamic images, a self-adaptive image processing device is disclosed in an embodiment of the present invention, which at least includes two low pass filters with different bandwidths. In the static image processing, the signal processed by the wide-band low pass filter is assigned by a relative large weighting value. On the other aspect, in the dynamic image processing, the signal processed by the narrow-band low pass filter is assigned by a relative large weighting value. In this manner, in the static image processing, the color transition issue is reduced, and the color is kept sharp; in the dynamic image processing, the cross color issue is reduced. 
       FIG. 1  is a circuit block diagram of a self-adaptive image processing device  10  according to a preferred embodiment of the present invention. It should be noted that,  FIG. 1  shows the circumstance that is used in the YUV color space. In  FIG. 1 , an input signal CS represents the video composite signal, and a color information signal UV represents the color information signal with a high frequency component and a baseband component. Herein, the video composite signal CS includes a luminance component and a chrominance component. For example, when it is applied to the YUV color space, Y component represents the luminance component, and U component and V component represent the chrominance component. That is to say, the color information signal UV is considered as the chrominance component of the video composite signal CS. Particularly, the color information signal UV is the chrominance component obtained after the luminance component/chrominance component separating processing and the demodulation processing of the video composite signal CS. 
     As shown in  FIG. 1 , the image processing device  10  includes a dynamic estimating unit  100 , a narrow-band low pass filter  200 , a wide-band low pass filter  300  and a weighting unit  400 . 
     The dynamic estimating unit  100  receives the video composite signal CS, estimates the dynamic motion degree of the video composite signal CS, and outputs a motion factor MF. The motion factor MF is used to represent the dynamic motion degree of the video composite signal CS. For example, the value of the motion factor MF is large if the dynamic motion degree of the video composite signal CS becomes great, that is, the video composite signal CS may be considered as a dynamic image. On the contrary, the value of the motion factor MF is small if the dynamic motion degree of the video composite signal CS becomes small, that is, the video composite signal CS is considered as a static image. 
     The narrow-band low pass filter  200  receives the color information signal UV, and performs the narrow-band low pass filtering to the color information signal UV, so as to obtain a narrow-band filtered signal UV_NB. 
     The wide-band low pass filter  300  receives the color information signal UV, and performs the wide-band low pass filtering to the color information signal UV, so as to obtain a wide-band filtered signal UV_WB. 
     The weighting unit  400  receives the motion factor MF output by the dynamic estimating unit  100 , the narrow-band filtered signal UV_NB output by the narrow-band low pass filter  200  and the wide-band filtered signal UV_WB output by the wide-band low pass filter  300 . The weighting unit  400  determines the weight for the narrow-band filtered signal UV_NB and the weight for the wide-band filtered signal UV_WB according to the motion factor MF, so as to output a color information signal UV′. 
     Basically, the color information signal UV′ is considered as the baseband component with a part of the high frequency component of the color information signal UV. Alternatively, the color information signal UV′ is considered as the signal remained after a part of the high frequency component is removed from the color information signal UV. As for how much of the high frequency component of the color information signal UV is filtered, it depends upon the dynamic motion degree of the video composite signal CS. For example, the greater the dynamic motion degree of the video composite signal CS is, the more high frequency component is filter; and on the contrary, the smaller dynamic motion degree of the video composite signal CS is, the less high frequency component is filtered. 
       FIG. 2  is a circuit block diagram of a dynamic estimating unit  100  of  FIG. 1 . The dynamic estimating unit  100  includes a frame difference estimating unit  110  and a look-up table unit  120 . The representation meanings of the reference numerals p 2 , p 1 , c 1 , n 1  and n 2  of  FIG. 2  may be obtained with reference to  FIG. 3 . The frame difference estimating unit  110  outputs a frame difference value D according to p 2 , p 1 , c 1 , n 1  and n 2 , and the frame difference value D is input to the look-up table unit  120 , so as to correspondingly obtain the motion factor MF. 
     Referring to  FIG. 3 , five frames shown in  FIG. 3  respectively represent five successive frames displayed in sequence, that is, the displaying sequence is that, the frame before the previous frame→the previous frame→the current frame→the next frame→the frame after the next frame. Therefore, it is known from  FIG. 3  that, the reference numerals p 2 , p 1 , c 1 , n 1  and n 2  represent the video composite signal CS at the same display position (i.e., the same pixel) of the five frames. 
     When the National Television Standards Committee (NTSC) specification is applied in the present embodiment, the frame difference value D are defined as follows:
 
 D 1= abs ( p 1− c 1)  (3);
 
 D 2= abs ( c 1− n 1)  (4);
 
 D=abs ( D 1− D 2)  (5).
 
     Equation (3) represents that, the absolute differential value of p 1  and c 1  is defined as D 1 . Similarly, Equation (4) represents that the absolute differential value of c 1  and n 1  is defined as D 2 . When the image is static, the value of D 1  is quite close to that of D 2 . On the contrary, when the image is dynamic, the value of D 1  is significantly different from that of D 2 . Equation (5) represents that the frame difference value D is defined as the absolute value of the difference value between D 1  and D 2 . 
     When the Phase Alternating Line (PAL) specification is applied in the present embodiment, the frame difference values D are defined as follows:
 
 D 1= abs ( p 2− c 1)  (6);
 
 D 2= abs ( c 1− n 2)  (7);
 
 D=abs ( D 1− D 2)  (8).
 
     The representations of Equations (6)-(8) are similar to that of Equations (3)-(5), which thus will not be repeated herein. 
     It is known by those skilled in the art that, the definition of the frame difference value D is not limited to the above equations. Those skilled in the art may appreciate different definition manners in the field, and the implementation of the present embodiment is not limited herein. 
     After the frame difference value D has been determined, the look-up table unit  120  obtains the corresponding motion factor MF according to an internal relationship curve. The curve of the relationship between the frame difference value D and the motion factor MF is as shown in  FIG. 4  for example. For convenience, the motion factor MF may be normalized to be between 0 and 1. When the D value is smaller than U 1 , MF value is V 1  (the value may be 0); when the D value is between U 1  and U 2 , MF value is V 2 , and so forth. V 7  is the maximum value of MF, which may be 1. 
     Next, how the narrow-band low pass filter  200  and the wide-band low pass filter  300  perform the low pass filtering to the color information signal UV is described below. 
       FIG. 5   a  is a schematic view of the narrow-band low pass filter  200 .  FIG. 5   b  is a schematic view of the wide-band low pass filter  300 . In the present embodiment, the structure and operations of the narrow-band low pass filter  200  are quite similar to that of the wide-band low pass filter  300 . However, the structures and operations of the narrow-band low pass filter  200  may be respectively different from that of the wide-band low pass filter  300 , so long that the narrow-band low pass filtering and the wide-band low pass filtering may be performed to the color information signal UV respectively. 
     As shown in  FIG. 5   a , the narrow-band low pass filter  200  includes a re-sampler  210 , adders  220 - 240 , multipliers  250 - 270  and an adder  280 . 
     The re-sampler  210  includes a plurality of (e.g., 10) serially-connected registers  210   a - 210   j . Each of the registers  210   a - 210   j  registers the color information signal UV and then outputs it as d 20 -d 29 . 
     The adder  220  sums up the color information signal UV and the register output d 29 , and outputs the summing result to the multiplier  250 . The adder  230  sums up the register output d 21  and the register output d 27 , and outputs the summing result to the multiplier  260 . The adder  240  sums up the register output d 23  and the register output d 25 , and outputs the summing result to the multiplier  270 . 
     The reason of selectively taking every other of the register outputs d 20 -d 29  lies in taking out the same sub components of the color information signal UV. Particularly, when 6 register outputs that are taken out at a certain time are all V components, the subsequent processing are conducted, and then, the weighting unit  400  outputs the processed V components. Then, at the next time point, the 6 register outputs are all U components, and the subsequent processing is conducted, and then, the weighting unit  400  outputs the processed U components. Moreover, if it is necessary, the sampling quantity may be changed. 
     The multiplier  250  multiplies the summing result of the adder  220  by the parameter p 21 , and outputs the multiplying result to the adder  280 . The multiplier  260  multiplies the summing result of the adder  230  by the parameter p 22 , and outputs the multiplying result to the adder  280 . The multiplier  270  multiplies the summing result of the adder  240  by the parameter p 23 , and outputs the multiplying result to the adder  280 . The adder  280  sums Up the multiplying results of the multipliers  250 - 270  to obtain the narrow-band filtered signal UV_NB. The parameters p 21 -p 23  may be varied depending upon the designed bandwidth. 
     As shown in  FIG. 5   b , the wide-band low pass filter  300  includes a re-sampler  310 , adders  320 - 340 , multipliers  350 - 370  and an adder  380 . The re-sampler  310  includes a plurality of (e.g., 10) serially-connected registers  310   a - 310   j . The parameters p 31 -p 33  may be varied depending upon the designed bandwidth. 
     Since the structure and operations of the narrow-band low pass filter  200  may be quite similar to that of the wide-band low pass filter  300 , based upon the above description, those skilled in the art may appreciate that how the wide-band low pass filter  300  performs the wide-band filtering to the color information signal UV, so as to obtain the wide-band filtered signal UV_WB. 
       FIG. 6  is a schematic view of a weighting unit  400  of  FIG. 1 . As shown in  FIG. 6 , the weighting unit  400  includes multipliers  410 ,  420  and an adder  430 . 
     The multiplier  410  multiplies the narrow-band filtered signal UV_NB by the motion factor MF, and outputs the multiplying result to the adder  430 . The multiplier  420  multiplies the wide-band filtered signal UV_WB by the parameter (1-MF), and outputs the multiplying result to the adder  430 . The adder  430  sums up the multiplying results of the multipliers  410  and  420 , so as to obtain the color information signal UV′. 
     It is known from the architecture of  FIG. 6  that, in the present embodiment, the greater the dynamic motion degree of the image is (that is, the motion factor MF is larger), the higher proportion the narrow-band filtered signal UV_NB takes in the color information signal UV′. On the contrary, the smaller the dynamic motion degree of the image is (that is, the motion factor MF is smaller), the higher proportion the wide-band filtered signal UV_WB takes in the color information signal UV′. 
     Although the weighting unit  400  utilizes the linear weighting to obtain the color information signal UV′ in this embodiment, those skilled in the art would understand that other weighting schemes also can be applied in the present embodiment. 
     Although the YUV color space is taken as an example for illustration in the present embodiment, other color spaces also can be applied in the present embodiment, as long as they have both the luminance component and the chrominance component. For example, when it is applied in the YCbCr color space, Y component still represents the luminance component, and the chrominance signal CbCr represents the chrominance component. Alternatively, when it is applied in the YIQ color space, Y component still represents the luminance component, and I component and Q component represent the chrominance component. The chrominance component serves as an input signal for the low pass filter  200 / 300 . 
     Although in the above embodiments, the image processing device only includes two low pass filters with different bandwidths, those skilled in the art may modify it to a plurality of low pass filters with different bandwidths, so as to achieve the purpose of the present embodiment. 
     To sum up, in the present embodiment, during the static image processing, not only the color transition issue is reduced, but also the color is kept sharp; and during the dynamic image processing, the cross color issue is also reduced. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.