Abstract:
Systems and methods are disclosed herein for a motion detection system for video signal processing that includes a luminance motion detector, a chroma motion detector, and a smoothness detector. These systems and methods may also include a phase motion detector, a baseband YC separation circuitry for video signal processing, a chip for video signal processing, and a video signal processing system used in an electronic article.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) AND CLAIM OF PRIORITY 
       [0001]    This application claims the benefit under 35 U.S.C. §119(a) to a Singapore patent application filed in the Intellectual Property Office of Singapore on Dec. 31, 2008 and assigned Serial No. 200809671-1, the entire disclosure of which is hereby incorporated by reference. 
       TECHNICAL FIELD OF THE INVENTION 
       [0002]    The present invention generally relates to video signal processing, and more particularly to a phase motion detector for baseband YC separation for image quality improvement. 
       BACKGROUND OF THE INVENTION 
       [0003]    In composite video television systems such as NTSC and PAL, luminance and chrominance information share a portion of the total signal bandwidth. While clean separation between luminance and chrominance is highly desired, current video signal decoders misinterpret the shared luminance and chrominance information, resulting in cross color and dot crawl. Both are highly disturbing artifacts. The term “cross color” refers to corruption of the chrominance spectrum caused by the misinterpretation of high-frequency luminance information as chrominance information. Cross color manifests itself in spectrum of bright colors changing from frame to frame. Conversely, the term “dot crawl” or “cross luminance” refers to corruption of the luminance spectrum by the misinterpretation of chrominance information as high-frequency luminance information. Dot crawl manifests itself in patterned high amplitude noise. 
         [0004]    Both artifacts can be reduced by selectively filtering video signals during signal processing. The filtering process usually employs a 3D comb filter comprising at least one line comb filter and at least one frame comb filter. A line comb filter can reduce such artifacts but its effectiveness is limited to artifacts generated by vertical edges and it has a disadvantage of decreasing the vertical resolution. A frame comb filter, on the other hand, provides maximum picture resolution but can only be applied to stationary parts of a picture. To maximize the effectiveness of the comb filters, a highly precise motion detector that can differentiate between the moving and stationary pixels is required. 
         [0005]    Conventional arts use a low pass inter-frame difference to generate a motion map to select line comb filters when motion is detected and frame comb filters when there is no motion. Depending on the cut-off frequency of the low pass filter, the performance of the 3D comb filter varies. If the cut-off frequency is high, some motion due to cross luminance may be falsely detected and the 3D comb filter&#39;s effectiveness is reduced. If the cut-off frequency is low, motion with higher frequency content may not be detected and motion smearing results. The higher the overlapping of the chrominance with video bandwidth, the more ineffective the motion detection. 
         [0006]    Some have improved the performance of motion detection by associating oblique correlation with likelihood of false motion. One disclosed motion detection device including an oblique correlation detection section, motion detection section and motion determination section decreases the sensitivity of motion detection in the presence of an oblique correlation. However, the implementation of the concept using decreased sensitivity in presence of oblique correlation is not sufficient because of the conflict of interests. On one hand, the decreased sensitivity may have impaired the detection of true motion for oblique objects. On the other hand, decreased sensitivity may not be sufficient to prevent false motion detection in mixed color/luminance edges since cross luminance are typically of large amplitudes. 
         [0007]    Another example for motion detection uses a plurality of temporal pixels to determine the motion or still status of the video composite signal suitable for use in a 3D comb filter in video decoder. Yet another example for motion detection uses a motion detection circuitry with precise Y motion and C motion detection. The Y motion detection uses the frame difference of line-comb Y signal with chroma level and vertical edge consideration. The C motion detection uses the frame difference of line-comb C signal, together with the frame difference of composite signal and chroma vertical and horizontal correlation computed from the frame-comb Y signals of adjacent lines. Yet another example for motion detection uses a two-frame difference signal that has been filtered to remove chrominance information. The filtering is performed on at least one spatial axis according to the spatial correlation. Although this motion detection considers the contributions from both luminance and chroma, it does not represent the temporal difference between the frames being filtered. 
         [0008]      FIG. 13  shows an exemplary functional block diagram of a motion detector of a conventional 3D comb filter. As to the NTSC standard, an approximate luminance data is obtained after the composite video signal has passed through a low pass filter, and a luminance data of the previous frame is obtained after the approximate luminance data has been delayed by a frame buffer for a frame time. The luminance data of the current frame is then compared with the luminance data of the previous frame so as to obtain a luminance difference. In addition, a chrominance data is obtained after the composite video signal has passed through a band pass filter and has been subtracted from the luma data. Then the chrominance data of the previous two frames is obtained after the chrominance data has been delayed by the frame buffers for two frame time. A chrominance difference is obtained after the chrominance data of the current frame is subtracted from the chrominance data of the previous two frames. A detecting circuit calculates a motion factor by selecting a number which is bigger between the luminance difference and the chrominance difference. 
         [0009]    Generally, these methods do not consider motion contributed by chroma component because of interfering high frequency luminance at chroma band. However, certain types of motion exist with purely color motion and a misdetection results in color smearing. 
         [0010]    Hence, there is a need to detect true luminance and chroma motions, especially chroma-only motion and high frequency luminance motion. Furthermore, the motion detection problem in baseband is more challenging than in composite domain in that there are 3 corrupted component inputs not guaranteed to be generated by complementary decoders. 
       SUMMARY 
       [0011]    In one embodiment of the present disclosure, there is provided a motion detection system that detects all types of motions including high frequency luminance motion and chroma motion independent of other signal processing. The motion detection system may comprises a luminance motion detector detecting the low frequency luminance changes, a chrominance motion detector for detecting the chroma changes, and a smoothness detector detecting the flat regions in chroma component. These systems and methods may further comprise a phase motion detector detecting the high frequency luminance and chroma changes and outputting the results of the detection into a video processing unit or other device. 
         [0012]    Other technical features may be readily apparent to one skilled in the art from the following figures, descriptions, and claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    Preferred embodiments according to the present disclosure will now be described with reference to the Figures, in which like reference numerals denote like elements. 
           [0014]      FIG. 1  is a functional block diagram of the circuitry of the motion detection system for the NTSC standard in accordance with one embodiment of the present disclosure; 
           [0015]      FIG. 2  shows exemplary electric circuitries for the luminance motion detector  101 , the chrominance motion detectors  102 / 103 , the smoothness detectors  104 / 105 , and the phase motion detectors  106 / 107  in accordance with one embodiment of the present disclosure; 
           [0016]      FIG. 3  shows an exemplary circuitry of the motion detector for NTSC standard in accordance with another embodiment of the present disclosure; 
           [0017]      FIG. 4  is a functional block diagram showing a baseband YC separation circuitry in accordance with one embodiment of the present disclosure; 
           [0018]      FIG. 5  shows an exemplary circuit of the cross luminance suppression circuit  2001  for the NTSC standard in accordance with one embodiment of the present disclosure; 
           [0019]      FIG. 6 , there is provided an exemplary circuit of the cross chroma suppression circuits  2002 / 2003  in accordance with one embodiment of the present disclosure; 
           [0020]      FIG. 7  is a functional block diagram of a video signal processing system in accordance with one embodiment of the present disclosure; 
           [0021]      FIG. 8  is a functional block diagram of the circuitry of the motion detection system for the PAL standard in accordance with one embodiment of the present disclosure; 
           [0022]      FIG. 9  show exemplary electric circuitries for the luminance motion detector  1101 , the chrominance motion detectors  1102 / 1103 , the smoothness detectors  1104 / 1105 , and the phase motion detectors  1106 / 1107  in accordance with one embodiment of the present disclosure; 
           [0023]      FIG. 10  shows an exemplary circuit of the motion detector for PAL standard in accordance with another embodiment of the present disclosure; 
           [0024]      FIG. 11  shows an exemplary circuit of the cross luminance suppression circuit  2001  in the baseband YC separation circuitry  2000  as shown in  FIG. 4  for PAL standard in accordance with one embodiment of the present disclosure; 
           [0025]      FIG. 12  shows an exemplary circuit of the cross chroma suppression circuits  2002 / 2003  in the baseband YC separation circuitry  2000  as shown in  FIG. 4  for PAL standard in accordance with one embodiment of the present disclosure; and 
           [0026]      FIG. 13  shows a functional block diagram of a motion detector. 
       
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0027]    The present disclosure may be understood more readily by reference to the following detailed description of certain embodiments of the disclosure. Throughout this disclosure, where publications are referenced, the disclosures of these publications are hereby incorporated by reference in their entireties into this application in order to more fully describe the state of art to which this disclosure pertains. 
         [0028]    While embodiments of the present disclosure will be described in reference to the accompanying drawings, the specifics and details are provided for the sole purpose of illustrating selected embodiments of the present disclosure. It is to be appreciated that the present disclosure may be practiced without employing the specifics and details. Furthermore, certain variations of the specifics and details in the practice are permissible without deviation from the scope of the appended claims. 
         [0029]    As illustrated in  FIG. 1 , there is provided a functional block diagram of the circuitry of the motion detection system for the NTSC standard in accordance with one embodiment of the present disclosure. The motion detection system  100  comprises a luminance motion detector  101  that detects low frequency luminance motion between frame n and n−1; chrominance motion detectors  102 / 103  that detect U and V chroma motion between frame n and n−1 respectively; smoothness detectors  104 / 105  that detect presence of luminance residue on U and V chroma components in frame n and n−1 respectively; phase motion detectors  106  and  107  that detect average luminance and chroma motion between frames n, n−1, n−2 and n−3; and chroma motion combiner  108  that integrates the motions derived from U and V components. The motion detection system  100  further comprise a Max  606 , a saturation circuit  607 , and a 5H-max circuit  608 , which functions will be described in detail hereinafter. The saturation circuits clip an input signal to a defined output range, and the 5H-max circuit chooses the maximum value of 5 consecutive pixels in a horizontal window. 
         [0030]    With reference to  FIG. 2 , there are provided exemplary electric circuitries for the luminance motion detector  101 , the chrominance motion detectors  102 / 103 , the smoothness detectors  104 / 105 , and the phase motion detectors  106 / 107  in accordance with one embodiment of the present disclosure. 
         [0031]    The luminance motion detector  101  detects precisely changes in the luminance component between frame n and frame n−1 used for the frame comb in NTSC standard. The input signal is vertically filtered to remove chroma residue, to present the best-case line-comb Y signal for difference computation. The output signal is low-pass filtered to eliminate the possibility of chroma component corruption at high frequency. 
         [0032]    The luminance motion detector  101  receives three line signals from each of the current frame n and the previous frame n−1. For the current frame n, the three line signals are the next line signal Y m+1,n  current line signal Y m,n , previous line signal Y m−1,n  via two luminance line delay memories, where m denotes the line number. A vertical low pass filter  201  with coefficients [1 2 1]/4 is used to cancel out-of-phase chroma signal to generate line-comb signal YLC n . Concurrently, the luminance motion detector  101  also receives three line signals from the previous frame n−1: next line signal Y m+1,n−1 , current line signal Y m,n−1  and previous line signal Y m−1,n−1 , via one luminance frame delay memory and two additional luminance line delay memories. Similarly, a vertical low pass filter  202  is used to generate line-comb signal YLC n−1 . The line-comb signals YLC n  and YLC n−1  may alternatively be the output of line combs of the baseband circuitry. 
         [0033]    These line-comb signals YLC n  and YLC n−1  are then subtracted by a subtractor  203 . A horizontal low pass filter  204 , with low pass frequency characteristics not exceeding the lower end of the overlapping frequency band of chroma and luminance signal or band-stop frequency characteristics covering the chroma band, subsequently filters the line-comb signal differences to exclude possible interference of chroma residue. The magnitude is extracted by an absolute circuit  205  and passed through a coring circuit  206  to eliminate possible noise interference. Finally, the magnitude is multiplied by a multiplier  207  with gain, YGain (G 1 ), and clipped by a saturation circuit  208  to appropriate motion range to generate low frequency luminance motion YMn. 
         [0034]    The chroma motion detectors  102 / 103  detect precisely changes in the chroma components between frame n and frame n−1 used for frame comb in NTSC standard. The input signal is vertically filtered to remove luminance residue, to present best case line-comb C signal for difference computation. While each chroma component U or V is processed independently by the chrominance motion detectors  102 / 103  to generate chroma motions UD and VD, the operations for each chroma component are the same; thus for the sake of convenience, CD is used to refer inter-changeably to either UD or VD in this document. 
         [0035]    Similar to the luminance motion detector  101 , the chrominance motion detector  102 / 103  receives three line signals from each of the current frame n and previous frame n−1. For the current frame n, the three line signals are next line signal C m+1,n , current line signal C m,n  previous line signal C m−1,n  via  2  chroma line delay memories. A vertical low pass filter  301  with coefficients [1 2 1]/4 is used to cancel out-of-phase luminance signal to generate line-comb signal, CLC n . Concurrently, the chrominance motion detector  102 / 103  receives three line signals from the previous frame n−1: next line signal C m+1,n−1 , current line signal C m,n−1 , and previous line signal C m−1,n−1  received via one chroma frame delay memory and two chroma line delay memories. The line signals are vertically filtered by a vertical low pass filter  302  to generate line-comb signal, CLC n−1 . The signals CLC n  and CLC n−1  may be the output of line combs in a baseband circuitry discussed in detail hereinafter. 
         [0036]    These line-comb signals CLC n  and CLC n−1  are then subtracted by a subtractor  303 . Its magnitude is extracted by an absolute circuit  304  to generate intermediate chroma motion CD p , low pass filtered by a horizontal low pass filter  305  to smoothen transitions, and passed through a coring circuit  306  to eliminate possible noise interference. Finally, the magnitude is multiplied by a multiplier  307  with gain, CGAIN (G 2 ), and clipped by a saturation circuit  308  to appropriate motion range to generate chroma motion CD. 
         [0037]    The smoothness detector  104 / 105  detects the presence of luminance residue in chroma components. The detector uses a constructive phase-subtraction diagonally within field and temporally between frame n and frame n−1 used for frame comb in NTSC standard. A null output indicates flat region and accuracy of the chroma motion detector  102 / 103 . While each chroma component U or V is processed independently by smoothness detector to generate high frequency signal UF and VF, the operations for each chroma component are the same; thus for the sake of convenience, CF shall refer interchangeably to either UF or VF in this document. 
         [0038]    As the chroma motion may be influenced by luminance residue in chroma signal, it is desirable to differentiate between true and false chroma motion. The smoothness detectors  104 / 105  detect the presence of luminance residue and invalidate or override the output of respective chrominance motion detectors. The smoothness detectors  104 / 105  receive the same input as the chrominance motion detector  102 / 103 : next line signal C m+1,n , current line signal C m,n , and previous line signal C m−1,n  for current frame n; next line signal C m+1,n−1 , current line signal C m,n−1 , and previous line signal C m−1,n−1  for previous frame n−1. 
         [0039]    The smoothness detectors  104 / 105  include both forward and backward diagonal contributions. The line signals of current and previous frames are diagonally filtered by forward diagonal high pass filters  401 / 402 , and backward diagonal high pass filters  403 / 404  with common coefficients [−1 2 −1]/4. The input vector for forward diagonal contribution is [C x−1,m+1  C x,m  C x+1,m−1 ] while the input vector for backward diagonal contribution is [C x−1,m−1  C x,m  C x+1,m+1 ] where x is the horizontal position of the pixel. The forward diagonally filtered signals are subtracted by a subtractor  405  and its magnitude is extracted by an absolute circuit  407 . The backward diagonally filtered signals are subtracted by a subtractor  406  and its magnitude is extracted by an absolute circuit  408 . A max circuit  409  selects the maximum of the forward or backward contribution to generate an intermediate high frequency signal CF p . The CF p  is filtered by a horizontal low pass filter  410  to smooth transitions and then cored by a coring circuit  411  to eliminate small noise. A gain SmoGain (G 3 ) via a multiplier  412  is multiplied to the filtered output, and the signal is clipped by a saturation circuit  413  to generate high frequency signal CF. Alternatively, circuits  410 - 413  may be replaced by binary thresholding circuit to output  0  in presence of flat region and 1 in presence of luminance residue. 
         [0040]    The phase motion detectors  106 / 107  detect the luminance and chroma changes from the temporally co-located pixels in chroma components. The changes are made independent of luminance residue in chroma by considering the phase relationship of the interleave signal. Chroma pixels from current frame n(C n ), and three previous frames n−1 (C n −1), n−2 (C n −2), and n−3 (C n− 3) in NTSC standard are used to determine motion according to the following equation (1): 
         [0000]        YCD =Max{| C   n   +C   n−1   −C   n−2   −C   n−3   |, |C   n   −C   n−1   −C   n−2   +C   n−3 |}  (1) 
         [0041]    From one perspective, the first component gives the average chroma motion between frame n and n−2 while the second component measures the average luminance motion between frame n and n−2. From another perspective, the first component gives the difference in luminance motion between frame n and n−1 and frame n−2 and n−3 while the second component gives the difference in chroma motion between frame n and n−1 and frame n−2 and n−3. 
         [0042]    While each chroma component U or V is processed independently by the phase motion detectors  106 / 107  to generate YC motion signal YUD and YVD, the operations for each chroma component are the same; thus for the sake of convenience, YCD shall refer inter-changeably to either YUD or YVD in this document. 
         [0043]    The phase motion detectors  106 / 107  detect mainly chroma motion in the presence of luminance residue and high frequency luminance motion. The phase motion detectors  106 / 107  receive the current frame signal, C m,n , and a plurality of previous frame signals C m,n−1 , C m,n−2 , and C m,n−3 , via three chroma frame delay memories. Then the intermediate motion values YCD p  is computed via a circuit  501  according to the equation (2) below: 
         [0000]        YCD   p =Max{| C   m,n   +C   m,n−1   −C   m,n−2   −C   m,n−3   |, |C   m,n   −C   m,n−1   −C   m,n−2   −C   m,n−3 |}  (2) 
         [0044]    The motion values may be smoothed by a horizontal low pass filter  502  and cored through a coring circuit  503 . It may be scaled by gain PhaseGain (G 4 ) via a multiplier  504  and clipped by a saturation circuit  505  to generate YC motion signal, YCD. The same phase motion detector  106 / 107  may be applied on the luminance component to generate YC motion values according to the equation (3) below. 
         [0000]        YCD   p =Max{| Y   m,n   +Y   m,n−1   −Y   m,n−2   −Y   m,n−3   |, |Y   m,n   −Y   m,n−1   −Y   m,n−2   −Y   m,n−3 |}  (3) 
         [0045]    In this case, the phase motion detector can complement detection of high frequency luminance that may not be present as luminance residue in chroma signal. As each of the above detectors has its advantages and limitations, they are combined constructively to give measures of motion between the frames to be filtered. Now referring back to  FIG. 1 , the chroma combiner  108  combines results from independent detectors with U or V inputs. In the case of 4:2:2 sampling format, the samples of independent chroma is half that of luminance. The maximum chroma motion UD and VD is taken and duplicated corresponding to 2 luminance samples by a maxD circuit  601  to give C 2 D. Similarly, the maximum high frequency signal UF and VF is taken and duplicated by a maxD circuit  602  to give C 2 F and the maximum YC motion YUD and YVD is taken and duplicated by a maxD circuit  603  to give YC 2 D. Thus, the duplicated signals have the same sample rate as luminance motion. 
         [0046]    To suppress false chroma motion detected from luminance interference or temporally averaged motion, signals C 2 D and YC 2 D pass through a max circuit  604 . The output is further modified by a selector  605 . Output from the max circuit  604  is selected when flat chroma region is detected or C 2 F=0 and signal YC 2 D is selected in presence of luminance residue or C 2 F # 0  to give signal CM. This compensates for undetected chroma motion by phase motion detector due to averaging effect in phase motion detector. 
         [0047]    The final motion value, K_motion, is derived as the maximum  606  between the motion detected from luminance YM and motion detected from chrominance CM, clipped by a saturation circuit  607 , and further processed as the maximum in a 5-pixel horizontal window by 5H-max circuit  608 . 
         [0048]    Referring to  FIG. 3 , there is provided an exemplary circuitry of the motion detection system for NTSC standard in accordance with another embodiment of the present disclosure. Instead of combining the outputs of U and V detectors in the chroma combiner  108  as shown in  FIG. 1 , the intermediate output signals are combined before the filtering, coring, scaling and saturation processes. Intermediate chroma motions UDp and VDp are generated as before and combined either by simply interleaving UV or taking the maximum of UV and duplicating result via a maxD circuit  701 . The intermediate signal, C 2 Dp, is passed through a horizontal low pass filter  702 , coring circuit  703 , scaling circuit  704  and saturation circuit  705  to generate combined chroma motion C 2 D. 
         [0049]    Intermediate chroma high frequency signals UF p  and VF p  are generated via plurality of diagonal filters and subsequently combined either by simply interleaving UV or taking the maximum of UV and duplicating result via a maxD circuit  801 . The intermediate signal, C 2 F p , is passed through a horizontal low pass filter  802 , coring circuit  803 , scaling circuit  804  and saturation circuit  805  to generate combined high frequency signal C 2 F. Alternatively, signal C 2 Fp may be binary thresholded to output C 2 F=0 in presence of flat region and C 2 F-X in presence of luminance residue. 
         [0050]    Likewise, intermediate YC motion signals YUDp and YVDp are generated through an arithmetic circuit  901  and combined either by UV interleaving or duplicating maxd motion by the circuit  901 . The output signal YC 2 D P  that is subsequently processed by a horizontal low pass filter  902 , coring circuit  903 , scaling circuit  904  and saturation circuit  905  to generate combined YC motion signal YC 2 D. 
         [0051]    The various signals C 2 D, C 2 F and YC 2 D are combined through a selector circuit  1002  that selects YC 2 D when luminance residue is detected or the maximum of C 2 D and YC 2 D via a max circuit  1001  when flat chroma region is detected, according to control signal C 2 F. 
         [0052]    Referring to  FIG. 4 , there is provided a functional block diagram showing a baseband YC separation circuitry in accordance with one embodiment of the present disclosure. As shown in  FIG. 4 , the baseband YC separation circuitry  2000  comprises a cross luminance suppression circuit  2001  that suppresses dot crawl artifacts or chroma residue present in Y signal, a cross chroma (U) suppression circuit  2002  that suppresses cross colour artifacts or luminance residue present in U signals, a cross chroma (V) suppression circuit  2003  that suppresses cross colour artifacts or luminance residue present in V signals, and a baseband motion detector  2004  that differentiate between the moving and the stationary pixels such that the optimum comb filter can be selected to maximize effectiveness of YC separation. The baseband YC separation circuitry  2000  receives Y in , U in  and V in  input signals separately and outputs the clean Y out , U out , and V out , signals. The operation of such a baseband motion detector  2004  has been described above. 
         [0053]    Referring to  FIG. 5 , there is provided an exemplary circuit of the cross luminance suppression circuit  2001  for the NTSC standard in accordance with one embodiment of the present disclosure. A wideband filter  2101  with frequency response modeling the chroma band in composite signal and complementary to the horizontal filter  204  shown in  FIG. 1  filters out the low and high frequency signal and retains only the frequency band with interleave Y and C signal. The line comb  2102  removes the redundant chroma residue from the Y signal. It has a 3 line input, next line Y m+1,n,wbp , current line Y m,n,wbp  and previous line Y m−1,n,wbp . The inter-line differences are computed by subtractors  2103  and  2104  and subsequently mixed by a mixer  2105  corresponding to K_ 2 D signal from the inter-line correlator  2106  described hereinafter. 
         [0054]    The inter-line correlator  2106  detects the relative chroma correlation between the current and next line and current and previous line, such that the line comb does not filter across contrasting colour regions. The Y signal passes through the narrowband filter  2107  to isolate the sub-band of the YC interleave frequency band. The narrowband filter has a smaller bandwidth centered at chroma subcarrier frequency of 3.58 MHz compared to the wideband filter for purposes of less interference from luminance signal. The gradients of current and next line, G x,m,m+1 , and current and previous line, G x,m,m−1  are computed in gradient circuits  2108  and  2109  using band-passed Y signal represented by Y for simplicity according to the following equations (4-5) or (6-7). 
         [0000]        G   x,m,m+1= min{max{| Y   x,m+1−   Y   x+2,m   |, |Y   x+2,m+1   −Y   x,m |}, max{| Y   x,m+1   −Y   x−2,m   |, |Y   x−2,m+1−   Y   x,m |}}  (4) 
         [0000]        G   x,m,m−1= min{max{| Y   x,m−1−   Y   x+2,m   |, |Y   x+2,m−1   −Y   x,m |}, max{| Y   x,m−1   −Y   x−2,m   |, |Y   x−2,m−1−   Y   x,m |}}  (5) 
         [0000]        G   x,m,m+1= {max{| Y   x+1,m+1−   Y   x−1,m   |, |Y   x−1,m+1   −Y   x+1,m |}  (6) 
         [0000]        G   x,m,m−1= {max{| Y   x+1,m−1−   Y   x−1,m   |, |Y   x−1,m−1   −Y   x+1,m |}  (7) 
         [0055]    They are subsequently filtered by horizontal low pass filters  2110  and  2111  for continuity. The lower the gradient, the higher the correlation, meaning a higher possibility that the pixels from the two lines belong to the same colour region. Thus line-comb output from two lines having a lower gradient should have a higher contribution towards the final comb value. K_ 2 D is defined as the weight for the line comb filter between the current and previous line in the function circuit  2112 . K_ 2 D is represented by the equation (8) below. 
         [0000]        K   — 2 D= ( G′   m,m+1 )/( G′   m,m+1   +G′   m,m−1 )   (8) 
         [0056]    Alternatively, K_ 2 D can be obtained from the K_ 2 D values generated by the cross chroma suppression circuits  2002  and  2003 ′. An example method of combining may be represented by the equation (9) below: 
         [0000]        K   — 2 D =( GU′   m,m+1   +GV′   m,m+1 )/( GU′   m,m+1   +GV′   m,m+1   +GU′   m,m−1   +GV′   m,m−1 )   (9) 
         [0057]    where GU′ m,m+1  represents the low pass filtered gradient between the current and next line for chroma signal U, GV′ m,m+1  represents the low pass filtered gradient between the current and next line for chroma signal V, GU′ m,m−1  represents the low pass filtered gradient between the current and previous line for chroma signal U, and GV′ m,m−1  represents the low pass filtered gradient between the current and previous line for chroma signal V. 
         [0058]    The output of the line comb filter can be expressed according to the equation (10) below: 
         [0000]        Y   — 2 D=K   — 2 D *( Y   m   −Y   m−1 )+( l−K   — 2 D )*( Y   m   −Y   m+1 )   (10) 
         [0059]    The frame comb subtracts the previous frame signal Y m,n  from the current frame signal Y m , using subtractor  2113  to generate frame comb output Y_ 3 D. 
         [0060]    The residual chroma signal is extracted via a mixer circuit  2114  using motion value, K_motion from the baseband motion detector  2004  and the final clean luminance signal, Y out , is generated according to the equation (11) below by subtracting the residual chroma signal from input luminance signal, Y in , with a subtractor  2115  and clipping the output to defined pixel range with a saturation circuit  2116 . 
         [0000]        Y   out   =Y   m −( K _motion* Y   — 2 D +( l−K _motion)* Y   — 3 D )   (11) 
         [0061]    Referring to  FIG. 6 , there is provided an exemplary circuitry of the cross chroma suppression circuits  2002 / 2003  in accordance with one embodiment of the present disclosure. The architecture of the cross chroma suppression circuit is almost similar to the cross luminance suppression circuit. The differences are the absence of the wideband filter for line comb and narrowband filter for inter-line correlator. 
         [0062]    The chroma line comb  2202  removes the redundant luminance residue from the Uin or Vin signal. Signal C shall be referring to either signal U or V for the cross chroma suppression circuit. It has a three line input, next line C m+1,n,wbp  current line C m,n,wbp  and previous line C m−1,n,wbp . The inter-line differences are computed by subtractors  2203  and  2204  and subsequently mixed by a mixer  2205  corresponding to K_ 2 D signal from the inter-line correlator  2206 . 
         [0063]    The inter-line correlator  2206  detects the relative chroma correlation between the current and next line and current and previous line, such that the chroma line comb does not filter across contrasting colour regions. A low pass filter can be applied prior to gradient computation to exclude influence of luminance on chroma signal. The gradients of current and next line, G x,m,m+1 , and current and previous line, G x,m,m−1 , are computed in gradient circuits  2208  and  2209  according to the equations (12) and (13) below. 
         [0000]        G   x,m,m+1= min{max{| C   x,m+1−   C   x+1,m   |, |C   x+1,m+1   −C   x,m |}, max{| C   x,m+1   −C   x−1,m   |, |C   x−1,m+1−   C   x,m |}}  (12) 
         [0000]        G   x,m,m−1= min{max{| C   x,m−1−   C   x+1,m   |, |C   x+1,m−1   −C   x,m |}, max{| C   x,m−1   −C   x−1,m   |, |C   x−1,m−1−   C   x,m |}}  (13) 
         [0064]    They are subsequently filtered by horizontal low pass filters  2210  and  2211 . The lower the gradient, the higher the correlation, meaning a higher possibility that the pixels from the two lines belong to the same colour region. Thus line-comb output from two lines having a lower gradient should have a higher contribution towards the final comb value. K_ 2 D is defined as the weight for the line comb filter between the current and previous chroma line in the function circuit  2212 . K_ 2 D is represented by the equation (14) below. 
         [0000]        K   — 2 D= ( G′   m,m+1 )/( G′   m,m+1   +G′   m,m−1 )   (14) 
         [0065]    K_ 2 D from the cross chroma suppression circuits  2002  and  2003  can be combined using a max function and upsampled by two or interleaved to provide the K_ 2 D for the cross luminance suppression circuit  2001 . 
         [0066]    The output of the line comb filter can be expressed by the equation (15) below. 
         [0000]        C   — 2 D=K   — 2 D *( C   m   −C   m−1 )+( l−K   — 2 D )*( C   m   −C   m+1 )   (15) 
         [0067]    The frame comb adds the previous frame signal C m,n−1  from the current frame signal C m,n  using an adder  2213  to generate frame comb output C 3D. 
         [0068]    The final 3D value, C out  is generated via a mixer circuit  2214  using motion value, Kmotion from the baseband motion detector  2004  and clipped to valid pixel range with a saturation circuit  2216 . C out  can be represented by the equation (16) below. 
         [0000]        C   out   =K _motion* C   — 2 D +( l−K _motion)* C   — 3 D    (16) 
         [0069]    Referring to  FIG. 7 , there is provided a functional block diagram of a video signal processing system in accordance with one embodiment of the present disclosure. The signal processing system  4000  comprises a front end digital decoder  4001  and a baseband YC separation module  4007 . The front end digital decoder  4001  decodes the composite input signals to generate component Y, U and V signals. The decoder  4001  comprises a synchronization unit  4002  to capture the video synchronization signals and to lock the system clock to the frequency and phase of the incoming signal using the chroma burst, an input sample rate converter  4003  to re-sample the acquisition sample rate of 27 MHz to four times the sub-carrier frequency, a YC separation circuit  4004  to separate chroma and luminance signal from the composite signal, a chroma demodulator  4005  to demodulate the chroma signal according chroma phase lock loop, an output sample rate convertor and scaler  4006  to re-sample the separated signals to output sampling rate domain and to scale the video signal to required dynamics. 
         [0070]    The component signals from the decoder  4001  are input to the baseband YC separation circuit  4007  for further 3D comb filtering. The baseband YC separation circuit  4007  as described above is a second separation circuit in the signal processing system to compensate for inefficiency of the first separation circuit  4004  and to eliminate residual cross component signals. As such, the operation of the first separation circuit  4004  in composite domain may be simplified. In one embodiment, the baseband YC separation circuit  4007  may be a 3D comb filter using a mix of frame comb and line comb controlled by a motion detector. In another embodiment, the baseband YC separation circuit  4007  may be a 2D comb filter with a 3-line comb controlled by an inter-line correlator. In another embodiment, the baseband YC separation circuit  4007  may be a set of complementary or non-complementary filters around the chroma subcarrier frequency with band-stop or notch filter for the Y output and band-pass filter for the C output. In yet another embodiment, the input is bypassed for the Y output and band-pass filtered for the C output. The baseband YC separation circuit should operate independent of the front-end separation circuitry and the motion detector should perform precise motion detection regardless of source input. 
         [0071]    Now there is provided a detailed description of the motion detection system and baseband YC separation circuitry and signal processing system for PAL standard. Referring to  FIG. 8 , there is provided a functional block diagram of the circuitry of the motion detection system for the PAL standard in accordance with one embodiment of the present disclosure. As shown in  FIG. 8 , the motion detection system  1100  comprises a luminance motion detector  1101  that detects low frequency luminance motion between frames n and n−2; chrominance motion detectors  1102  and  1103  that detect U and V chroma motion between frames n and n−2; smoothness detectors  1104  and  1105  that detect presence of luminance residue on U and V chroma components in frames n and n−2; phase motion detectors  1106  and  1107  that detect average luminance and chroma motion between frames n, n−2, n−3, n−4 and n−5; and a chroma motion combiner  1108  that integrates the motion derived from U and V components. The motion detection system  1100  further comprises a max circuit  1606 , a saturation circuit  1607 , and a 5H-max circuit  1608 , which functions will be described hereinafter. 
         [0072]    The motion detector system  1100  for the PAL standard has a similar architecture of the motion detector system  100  for the NTSC standard. But the motion detector system  1100  uses previous frame n−2 instead of n−1, previous line signals Y m−2,n , C m−2,n  instead of Y m−1,n , C m−1,n  and next line signals Y m+2,n , C m+2,n  instead of Y m+1,n , C m+1,n  for luminance motion detector, chrominance motion detectors and smoothness detectors and computation specific to phase relationships of the standard in phase motion detector. 
         [0073]    Referring  FIG. 9 , there are provided exemplary electric circuitries for the luminance motion detector  1101 , the chrominance motion detectors  1102 / 1103 , the smoothness detectors  1104 / 1105 , and the phase motion detectors  1106 / 1107  in accordance with one embodiment of the present disclosure. 
         [0074]    The luminance motion detector  1101  receives three line signals from each of the current frame n and previous frame n−2. For the current frame n, the three line signals include the next line signal Y m+2,n , current line signal Y m,n , previous line signal Y m−2,n  via 4 luminance line delay memories. A vertical low pass filtering  1201  with coefficients [1 2 1]/4 is performed to cancel out-of-phase chroma signal to generate line-comb signal YLC n . Concurrently, for the previous frame n−2, the three line signals include the next line signal Y m+2,n−2 , current line signal Y m,n−2  and previous line signal Y m−2,n−2 , via two luminance frame delay memories and four additional luminance line delay memories. Similarly, a vertical low pass filtering  1202  is performed to generate line-comb signal YLC n−2 . The line-comb signals YLC n  and YLC n−2  may alternatively be the output of line combs of the baseband circuitry. 
         [0075]    These line-comb signals YLC n , and YLC n−2  are then subtracted by a subtractor  1203 . The horizontal low pass filter  1204 , with low pass frequency characteristics not exceeding the lower end of the overlapping frequency band of chroma and luminance signal or band-stop frequency characteristics covering the chroma band, subsequently filters the line-comb signal differences to exclude possible interference of chroma residue. The magnitude is extracted by absolute circuit  1205  and passed through coring circuit  1206  to eliminate possible noise interference. Finally, it is multiplied by gain, YGain (GJ) via multiplier  1207  and clipped by saturation circuit  1208  to appropriate motion range to generate low frequency luminance motion YM. 
         [0076]    Similar to the luminance motion detector  1101 , the chrominance motion detector  1102 / 1103  receives three line signals from each of the current frame n and previous frame n−2. For the current frame n, the three line signals include the next line signal C m+2,n , current line signal C m,n , previous line signal C m−2,n  via four chroma line delay memories. A vertical low pass filter  1301  with coefficients [1 2 1]/4 is used to cancel out-of-phase luminance signal to generate line-comb signal, CLC n . Concurrently, for the previous frame n−2, the three line signals include the next line signal C m+2,n−2 , current line signal C m,n−2 , previous line signal C m−2,n−2 , received via two chroma frame delay memories and four chroma line delay memories, which are vertically filtered by a vertical low pass filter  1302  to generate line-comb signal CLC n−2 . The signals CLC n  and CLC n−2  may be from the output of line combs in a baseband circuitry described in detail hereinafter. 
         [0077]    These line-comb signals CLC n  and CLC n−2  are then subtracted by a subtractor  1303 . Its magnitude is extracted by an absolute circuit  1304  to generate intermediate chroma motion CDp and low pass filtered by a horizontal low pass filter  1305  to smoothen transitions and passed through a coring circuit  1306  to eliminate possible noise interference. Finally, it is multiplied by gain, CGAIN (G 2 ) via a multiplier  1307 , and clipped by a saturation circuit  1308  to appropriate motion range to generate chroma motion CD. 
         [0078]    The smoothness detectors  1104  and  1105  detect the presence of luminance residue and invalidate or override the output of respective chrominance motion detectors. The smoothness detectors  1104 / 1105  include both forward and backward diagonal contributions. The line signals of current and previous frames are diagonally filtered by forward diagonal high pass filters  1401 / 1402 , and backward diagonal high pass filters  1403 / 1404  with common coefficients [−1 2 −1]/4. It receives the same input as the chrominance motion detector with three line signals from the current frame n: next line signal C m+2,n , current line signal C m,n , previous line signal C m−2,n  and three line signals from the previous frame n−2: next line signal C m+2,n−2  current line signal C m,n−2 , previous line signal C m−1,n−2 . 
         [0079]    The line signals of current and previous frames are diagonally filtered by forward diagonal high pass filters  1401  and  1402 , and backward diagonal high pass filters  1403  and  1404  with common coefficients [−1 2 −1]/4. The input vector for forward diagonal contribution is [C x−2,m+2  C x,m  C x+1,m−2 ] while the input vector for backward diagonal contribution is [C x−1,m−2  C x,m  C x+1,m+2 ]. The forward diagonally filtered signals are subtracted by a subtractor  1405  and its magnitude is extracted by an absolute circuit  1407 . The backward diagonally filtered signals are subtracted by a subtractor  1406  and its magnitude is extracted by an absolute circuit  1408 . The max circuit  1409  selects the maximum of the forward or backward contribution to generate intermediate high frequency signal CFp. The signal is filtered by a horizontal low pass filter  1410  to smooth transitions and then cored by a coring circuit  1411  to eliminate small noise. A gain SmoGain (G 3 ) is multiplied to the filtered output and signal is then clipped by a saturation circuit to generate high frequency signal CF. Alternatively, circuits  1410 - 1413  may be replaced by binary thresholding circuit to output  0  in presence of flat region and 1 in presence of luminance residue. 
         [0080]    The phase motion detectors  1106 / 1107  complement the above detectors by detecting mainly chroma motion in the presence of luminance residue and high frequency luminance motion. Each receives the current frame signal, C m,n , and a plurality of previous frame signals C m,n−1 , C m,n−2 , C m,n−3  and C m,n−4 , via four chroma frame delay memories. Then each computes intermediate motion values YCDp via a circuit  1501  according to the equation (17) below. 
         [0000]        YCD   p =Max{| C   m,n   −C   m,n−1   +C   m,n−2   −C   m,n−3   |, |C   m,n−1   −C   m,n−2   +C   m,n−3   −C   m,n−4 |}  (17) 
         [0081]    The first component detects average chroma and luminance motion for plurality of frames from n to n−3 while the second component detects average chroma and luminance motion for plurality of frames from n−1 to n−4. As each component is asymmetrical about the temporal center, any scene change or chroma motion only occurring between second and third frame is not detected. Thus, a second component guarantees full motion detection. 
         [0082]    The motion values may be smoothed by a horizontal low pass filter  1502  and cored through a coring circuit  1503 . It may be scaled by gain PhaseGain (G 4 ) via a multiplier  1504  and clipped by a saturation circuit  1505  to generate YC motion signal, YCD. 
         [0083]    The same phase motion detectors  1106 / 1107  may be applied on the luminance component to generate YC motion values according to the equation (18) below. 
         [0000]        YCD   p =Max{| Y   m,n   −Y   m,n−1   +Y   m,n−2   −Y   m,n−3   |, |Y   m,n−1   −Y   m,n−2   +Y   m,n−3   −Y   m,n−4 |}  (18) 
         [0084]    In this case, the phase motion detector can complement detection of high frequency luminance that may not be present as luminance residue in chroma signal. 
         [0085]    The chroma combiner  1108  combines results from independent detectors with U or V inputs. In the case of 4:2:2 sampling format, the samples of independent chroma is half that of luminance. The maximum chroma motion UD and VD is taken and duplicated corresponding to two luminance samples by a maxD circuit  1601  to give C 2 D. Similarly, the maximum high frequency signal UF and VF is taken and duplicated by a maxD circuit  1602  to give C 2 F and the maximum YC motion YUD and YVD is taken and duplicated by a maxD circuit  1603  to give YC 2 D. The duplicated signals have the same sample rate as luminance motion. 
         [0086]    signals C 2 D and YC 2 D pass through the max circuit  1604  and is further modified by the selector  1605 . Output from max circuit  1604  is selected when a flat chroma region is detected or C 2 F=0 and signal YC 2 D is selected in presence of luminance residue or C 2 F≠0 to give signal CM. This compensates for undetected chroma motion by phase motion detector due to averaging effect in phase motion detector. The final motion value, K_motion, is derived as the maximum  1606  between the motion detected from luminance YM and motion detected from chrominance CM, clipped by the saturation circuit  1607 , and further processed as the maximum in a 5-pixel horizontal window by the 5H-max circuit  1608 . 
         [0087]    Referring to  FIG. 10 , there is provided an exemplary circuit of the motion detector for PAL standard in accordance with another embodiment of the present disclosure. Instead of combining the outputs of U and V detectors in the chroma combiner  1108 , the intermediate output signals are combined before the filtering, coring, scaling and saturation processes. The detailed description is similar to the one for NTSC standard described above. 
         [0088]    Referring to  FIGS. 11 and 12 , there are provided exemplary circuitries of the cross luminance suppression circuit  2001  and cross chroma suppression circuits  2002 / 2003  in the baseband YC separation circuitry  2000  as shown in  FIG. 4  for PAL standard in accordance with one embodiment of the present disclosure. The technical differences between circuits for the PAL and NTSC lie in the use of next line signal m+2 instead of m+1 and previous line signal m−2 instead of m−1 for line comb and previous frame signal n−2 instead of n−1 and in the design of wideband and narrow band filters for chroma subcarrier at 4.43 MHz instead of 3.58 MHz. Since the operation of the circuitry remains the same, detailed description of cross luminance suppression circuit  2001  and cross chroma suppression circuits  2002  and  2003  for the PAL standard is not provided. 
         [0089]    Generally, the disclosure is embedded in a baseband YC separation circuitry that reduces chroma residue in luminance component and luminance residue in chroma component. A preferred embodiment of the baseband YC separation circuitry comprises of a line comb filter that performs vertical filtering and a frame comb filter that performs temporal filtering. The disclosure is applied as a baseband motion detector to detect the motion between the candidate frames for temporal filtering. A mixer selects a high weight on the frame comb when the pixels are detected as stationary or selects a high weight on the line comb when pixels are detected as moving. 
         [0090]    The inputs to the baseband circuitry may be processed by a front end digital decoder. In this case, the front end digital decoder receives the composite signal or s-video signal and decodes it into component Y, U and V signals for processing in baseband. The decoding process may include YC separation with a simple 2D comb filter for example a line comb, a 3D comb filter for example a line and frame comb controlled by a motion detector, a notch filter for the Y signal and bandpass filter for the C signal, or simply a demodulation circuitry. 
         [0091]    Alternatively, the inputs may be processed by video decoder for example an MPEG 2 decoder. The inputs to the baseband motion detector may or may not be pre-processed by the baseband YC separation circuitry. Thus the disclosure is expected to consider the same variety of inputs as the baseband YC separation circuitry. 
         [0092]    The disclosure operates such that the inputs are not temporally filtered in the presence of motion and temporally filtered in the absence of motion, generating clean Y, U and V signals with reduction of cross colour and dot crawl and ensuring minimally modified signals in the absence of such artifacts. 
         [0093]    It can be applied to a chip or end consumer products like television, display sets, video CD player, DVD players or recorders and set-top-boxes with composite sources or sources that have composite conversion in at least one stage of processing prior to input. While the present disclosure has been described with reference to particular embodiments, it will be understood that the embodiments are illustrative and that the scope of the appended claims are not so limited. Alternative embodiments of this disclosure have been set forth by implication and will be apparent to those having ordinary skill in the art to which the present disclosure pertains. Such alternate embodiments are considered to be encompassed within the scope of one or more of the appended claims. Thus, the scope of this disclosure is described by the appended claims and is supported by the foregoing description. While this detailed description has set forth some embodiments of the present disclosure, the appended claims are sufficiently supported to cover and will cover other embodiments of this disclosure which differ from the described embodiments according to various modifications and improvements.