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Home | Alpha Telephone | Domain Names | Web Hosting | Get Traffic | xrEvidence | xrSoccer United States Patent
Luminance and chrominance signals separating filter adaptive to movement of image A luminance (Y) and chrominance (C) signals separating filter includes a motion detecting circuit which partially detects a movement of an image utilizing a correlation between frames; an inter-frame YC separating circuit which performs a separation utilizing the inter-frame correlation when the motion detecting circuit detects a still image, and outputs intra-frame YC separated C signals and intra-frame YC separated Y signals; an intra-frame YC separating circuit which partially detects a correlation between fields or between frames and a correlation in a field when the motion detecting circuit detects a moving image, performs a separation utilizing the correlations, and outputs intra-frame YC separated C signals and intra-frame YC separated Y signals; a C signal mixing circuit which mixes the inter-frame YC separated C signals and the intra-frame YC separated C signals in accordance with an output of the motion detecting circuit and outputs motion adaptive YC separated C signals; and a Y signal mixing circuit which mixes the inter-frame YC separated Y signals and the intra-frame YC separated Y signals in accordance with the output of the motion detecting circuit and outputs motion adaptive YC separated Y signals.
Assistant Examiner: Flynn; Nathan J. This application is a divisional of application Ser. No. 07/850,488, filed on Mar. 12, 1992 now U.S. Pat. No. 5,412,434, the entire contents of which are hereby incorporated by reference. We claim: 1. A luminance and chrominance signal separating filter for separating the luminance (Y) and chrominance (C) component signals from a composite color television signal defining sequential television frames adaptive to movement of an image defined by the composite color television filter, the C signals being frequency multiplexed with a high frequency region of the Y signals, comprising: a first Y-C separating circuit separating the C signals from the composite signal to develop a separated C signal; a two dimensional adaptive filter operatively connected to the first Y-C separating circuit and receiving the separated C signal for filtering only in a selected one or more of at least two dimensions in dependence on the level of correlation of the separated C signal in said dimensions to produce a filtered C signal, said two dimensional adaptive filter including, at least two dimensional filters, each providing directional filtering in a different set of one or more directions, of said separated C signal, and a correlation detector for determining the degree of image correlation in each of the directions employed by said at least two dimensional filters and selecting only the one of said dimensional filters which provides a higher correlation in at least one of said directions; and a brightness extraction circuit using the filtered C signal and the composite color television signal to produce said Y signals, thereby developing both a Y signal and a C signal from said composite color television signal. 2. The filter of claim 1 wherein said first Y-C separating circuit separates the composite signal in a first field by using signals from a second field. 3. A luminance and chrominance signal separating filter for separating the luminance (Y) and chrominance (C) component signals from a composite color television signal defining sequential television frames adaptive to movement of an image defined by the composite color television filter, the C signals being frequency multiplexed with a high frequency region of the Y signals, comprising: a first Y-C separating circuit separating the C signals from the composite signal to develop a separated C signal, wherein said first Y-C separating circuit separates the composite signal in a first field by using signals from a second field, and includes, an inter-field correlation detector monitoring the degree of correlation between at least two nearby field pixels, spatially located nearby each selected first field pixel in differing directions and from a different image field, and each selected first field pixel to determine a direction of maximum correlation, and inter-field processor means for combining each said selected first field pixel with an associated selected second field pixel in said direction of maximum correlation to develop the separated C signal associated with each selected first field pixel; a two dimensional adaptive filter operatively connected to the first Y-C separating circuit and receiving the separated C signal for filtering only in a selected one or more of at least two dimensions in dependence on the level of correlation of the separated C signal in said dimensions to produce a filtered C signal; and a brightness extraction circuit using the filtered C signal and the composite color television signal to produce said Y signals, thereby developing both a Y signal and a C signal from said composite color television signal. 4. The filter of claim 1, wherein said correlation detector is an intra-field correlation detector and monitors the degree of correlation between the selected first field pixel and adjacent pixels in the same field and extending in at least two dimensions to determine the degree of correlation in each of said dimensions. 5. The filter of claim 4, wherein said intra-field correlation detector further includes, vertical direction non-correlation energy detecting means for excluding a d.c. component in the vertical direction and a frequency component corresponding to a color sub-carrier component from a frequency component of a particular sampling point and finding an absolute value of the remaining frequency component to detect a vertical direction non-correlation energy; horizontal direction high frequency Y signal energy detecting means for extracting a frequency component, which is a low frequency component in the vertical direction and corresponds to a half of a color sub-carrier frequency in the horizontal direction, from the frequency component of the selected first field pixel and finding an absolute value of the extracted component to detect a horizontal direction high frequency Y signal energy; vertical correlation detecting means for comparing said vertical direction non-correlation energy with a first set value and comparing said horizontal direction high frequency Y signal energy with a second set value, and deciding that a correlation is present in the vertical direction when said vertical direction non-correlation energy is smaller than said first set value and said horizontal direction high frequency Y signal energy is larger than said second set value; horizontal direction non-correlation energy detecting means for excluding a d.c. component in the horizontal direction and a frequency component corresponding to a color sub-carrier component from a frequency component of the selected first field pixel and finding an absolute value of the remaining frequency component to detect a horizontal direction non-correlation energy; vertical direction high frequency Y signal energy detecting means for extracting a frequency component, which is a low frequency component in the horizontal direction and corresponds to a half of a color sub-carrier frequency in the vertical direction, from the frequency component of the selected first field pixel and finding an absolute value of the extracted components to detect a vertical direction high frequency Y signal energy; horizontal correlation detecting means for comparing said horizontal direction non-correlation energy with a third set value and comparing said vertical direction high frequency Y signal energy with a fourth set value, and deciding that a correlation is present in the horizontal direction when said horizontal direction non-correlation energy is smaller than said third set value and said vertical direction high frequency Y signal energy is larger than said fourth set value; and means for sending a control signal for selecting an output from outputs of a plurality of filters, which perform intra-field processes, in accordance with the result of the detections. 6. The filter of claim 1 wherein said at least two dimensional filters include, a horizontal direction C signal extracting filter, a vertical direction C signal extracting filter, and said correlation detector determining the degree of correlation of said composite color television signal in a vertical and horizontal direction. 7. A luminance and chrominance signal separating filter for separating the luminance (Y) and chrominance (C) component signals from a composite color television signal defining sequential television frames adaptive to movement of an image defined by the composite color television filter, the C signals being frequency multiplexed with a high frequency region of the Y signals, comprising: a first Y-C separating circuit separating the C signals from the composite signal to develop a separated C signal; a two dimensional adaptive filter operatively connected to the first Y-C separating circuit and receiving the separated C signal for filtering only in a selected one or more of at least two dimensions in dependence on the level of correlation of the separated C signal in said dimensions to produce a filtered C signal, said two dimensional adaptive filter including, a horizontal direction C signal extracting filter, a vertical direction C signal extracting filter, and a correlation detector for determining the degree of image correlation in each of the directions employed by said at least dimensional filters and selecting only the one of said dimensional filters which provides a higher correlation in least one of said directions, said correlation detector determining the degree of correlation of said composite color television signal in a vertical and horizontal direction, said correlation detector selecting said horizontal direction C signal extracting filter if the degree of horizontal correlation in said composite color television signal exceeds a first selected level, said correlation detector selecting said vertical direction C signal extracting filter if the degree of vertical correlation in said composite color television signal exceeds a second selected level; and a brightness extraction circuit using the filtered C signal and the composite color television signal to produce said Y signals, thereby developing both a Y signal and a C signal from said composite color television signal. 8. The filter of claim 6 wherein said at least two dimensional filters further includes a horizontal and vertical C signal extracting filter. 9. A luminance and chrominance signal separating filter for separating the luminance (Y) and chrominance (C) component signals from a composite color television signal defining sequential television frames adaptive to movement of an image defined by the composite color television filter, the C signals being frequency multiplexed with a high frequency region of the Y signals, comprising: a first Y-C separating circuit separating the C signals from the composite signal to develop a separated C signal; a two dimensional adaptive filter operatively connected to the first Y-C separating circuit and receiving the separated C signal for filtering only in a selected one or more of at least two dimensions in dependence on the level of correlation of the separated C signal in said dimensions to produce a filtered C signal, said two dimensional adaptive filter including, a horizontal direction C signal extracting filter, a vertical direction C signal extracting filter, and a horizontal and vertical C signal extracting filter, a correlation detector for determining the degree of image correlation in each of the directions employed by said at least two dimensional filters and selecting only the one of said dimensional filters which provides a higher correlation in least one of said directions, said correlation detector determining the degree of correlation of said composite color television signal in a vertical and horizontal direction, said correlation detector selecting said horizontal direction C signal extracting filter if there is a high degree of horizontal correlation in said composite color television signal but a lower degree of vertical correlation in said composite color television signal, said correlation detector selecting said vertical direction C signal extracting filter if there is a high degree of vertical correlation in said composite color television signal but a lower degree of horizontal correlation in said composite color television signal, said correlation filter selecting said horizontal and vertical C signal extracting filter if there is a high degree of both horizontal and vertical correlation in said composite color television signal; and a brightness extraction circuit using the filtered C signal and the composite color television signal to produce said Y signals, thereby developing both a Y signal and a C signal from said composite color television signal. 10. The filter of claim 3 wherein said first and second fields are in the same frame. 11. The filter of claim 10 wherein said nearby field used in said inter-field correlation detector is in the same frame as said first field. 12. The filter of claim 10 wherein said second field used in said inter-field correlation detector is in a different frame than said first field. 13. A luminance and chrominance signal separating filter for separating the luminance (Y) and chrominance (C) component signals from a composite color television signal defining sequential television frames adaptive to movement of an image defined by the composite color television filter, the C signals being frequency multiplexed with a high frequency region of the Y signals, comprising: a first Y-C separating circuit separating the C signals from the composite signal to develop a separated C signal; a two dimensional adaptive filter operatively connected to the first Y-C separating circuit and receiving the separated C signal for filtering only in a selected one or more of at least two dimensions in dependence on the level of correlation of the separated C signal in said dimensions to produce a filtered C signal; a brightness extraction circuit using the filtered C signal and the composite color television signal to produce said Y signals, thereby developing both a Y signal and a C signal from said composite color television signal an inter-frame Y-C separating circuit for separating the C signals from the composite signal by using the composite signals of a different frame to extract inter-frame Y and C signals; and mixing means for mixing said Y signal produced by said first Y-C separating circuit with said inter-frame Y signal produced by said inter-frame Y-C separating circuit to produce a Y output signal and for mixing said C signal produced by said first Y-C separating circuit with said inter-frame C signal produced by said inter-frame Y-C separating circuit to produce a C output signal. 14. The filter of claim 11 further comprising: a motion detecting circuit detecting motion in the image represented by the composite color television signal; and said mixing means varying the proportion of said Y signal produced by said first Y-C separating circuit mixed with said inter-frame Y signal produced by said inter-frame Y-C separating circuit to produce the output Y signal and varying the proportion of said C signal produced by said first Y-C separating circuit mixed with said inter-frame C signal produced by said inter-frame Y-C separating circuit to produce the output C signal in response to the degree of motion sensed by said motion detecting circuit. 15. A method of separating luminance (Y) and chrominance (C) component signals from a composite color television signal defining sequential television frames adaptive to movement of an image represented thereby, the C signals being frequency multiplexed within a high frequency region of the Y signals, comprising: a) separating the C signals from the composite signal in a first field by using the composite signals from a second field to develop a separated C signal; b) judging the degree of correlation between a selected pixel and adjacent pixels in the same field and extending in at least two dimensions to determine the presence of one or more dimensions of higher correlation; c) adaptively filtering the separated C signal in selected one or more of at least two dimensions as determined by said step b) of judging to produce a filtered C signal; d) producing a Y signal from the filtered C signal and the composite color television signal; and e) producing a second separated C signal from said composite signal. 16. The method of claim 15 wherein said step e) includes, i) separating second C signals from the composite signal in a first field by using the composite signals from a second field to develop a second separated C signal; ii) judging the degree of correlation between a selected pixel and adjacent pixels in the same frame and extending in at least two dimensions to determine a direction of higher correlation; and iii) filtering the second separated C signal in a dimension of the higher correlation determined by said step ii) of judging. 17. A method of separating chrominance (C) component signals from a composite color television signal defining sequential television frames adaptive to movement of an image represented thereby, the C signals being frequency multiplexed within a high frequency region of luminance (Y) signals, comprising: a) separating the C signals from the composite signal in a first field by using the composite signals from a second field to develop a separated C signal; b) judging the degree of correlation between a selected pixel and adjacent pixels in the same field and extending in at least two dimensions to determine the presence of one or more dimensions of higher correlation; and c) using an adaptive filter, responsive to said step b) of judging to adaptively filter the separated C signal only in a selected one ore more of at least two dimensions as determined by said step b) of judging to produce a filtered C signal. 18. The method of claim 17 wherein said step a) of separating adaptively separates the C signals from the composite signal and includes, i) determining which of at least two nearby field pixels, spatially located nearby each selected first field pixel and from a different image field, most closely correlate with said first field pixel to determine a direction of maximum correlation, ii) combining a selected first field pixel with an associated second field pixel in said direction of maximum correlation to develop the separated C signal associated with the selected first field pixel, and iii) repeating said steps i) and ii) for each said pixel in said composite color television signal. 19. The method of claim 17 wherein said step c) of using an adaptive filter includes, i) filtering the separated C signal in a first dimension, ii) filtering the separated C signal in a second dimension, iii) filtering the separated C signal in both said first and second directions, and iv) choosing one of said steps i)-iii) of filtering based on the determined direction of higher correlation as determined by said step b) of judging. 20. The method of claim 17 wherein said second field used in said step a) is in the same frame as said first field. 21. The method of claim 18 wherein said nearby field used in said step i) is in the same frame as said first field. 22. The method of claim 18 wherein said nearby field used in said step i) is in a different frame than said first field. 23. The method of claim 17 further comprising: e) inter-frame separating the C signals from the composite signal by using the composite signals of a different frame to extract inter-frame C signals; and f) mixing said mixing said C signal produced by said step d)) with said inter-frame C signal produced by said step e) to produce a C output signal. 24. The method of claim 23 wherein said method of separating further comprises: g) detecting motion in the image represented by the composite color television signal; and said step f) of mixing varying the proportion of said C signal produced by said step d)) mixed with said inter-frame C signal produced by said step e) to produce the C output signal in response to the degree of motion sensed by said step g) of detecting. 25. The method of claim 1 wherein said dimensional filters are selected from a group consisting of a horizontal filter, a vertical filter, and a horizontal/vertical filter. 26. The method of claim 17 wherein the dimension of higher correlation determined by said step b) of judging is selected from horizontal, vertical, or horizontal/vertical. FIELD OF THE INVENTION The present invention relates to a filter for separating luminance signals (hereinafter referred to as Y signals or Y) and chrominance signals (hereinafter referred to as C signals or C) from composite color television signals (hereinafter referred to as V signals) in the C signals are frequency-multiplexed within a high frequency region of the Y signals and, more particularly, to a luminance and chrominance signal separating filter (hereinafter referred to as a YC separating filter) adaptive to a movement of an image. BACKGROUND OF THE INVENTION A YC separating filter adaptive to a movement of an image judges whether an image is a still image or a moving image and performs a YC separation suitable for an image signal of the type judged. According to the current NTSC, composite signals in which C signals are frequency-multiplexed to a high frequency region of Y signals are employed. Therefore, YC separation is required in a receiver and an imperfect separation causes a deterioration in the quality of the image, such as cross color or dot crawl. Recently, with development of large capacity digital memory, various kinds of signal processing circuits for improving the quality of image, such as a YC separating filter adaptive to a movement of an image utilizing a delay circuit having a delay time equal to a vertical scanning frequency of a television signal or more, have been proposed. FIG. 110 is a block diagram showing an example of a conventional YC separating filter adaptive to a movement of an image. In FIG. 110, video (V) signals 1101 of the NTSC type are input to an input terminal 1001 and applied to input terminals of an intra-field YC separating circuit 1004, an inter-frame YC separating circuit 1005, a Y signal motion detecting circuit 1006 and a C signal motion detecting circuit 1007. In the intra-field YC separating circuit 1004, by an intra-field filter (not shown), intra-field YC separated Y signals 1102 and intra-field YC separated C signals 1103 which are divided into Y signals and C signals by an intra-field filter (not shown) are applied to a first input terminal of a Y signal mixing circuit 1009 and a first input terminal of a C signal mixing circuit 1010, respectively. In addition, in the inter-frame YC separating circuit 1005, by an inter-frame filter (not shown), inter-frame YC separated Y signals 1104 and inter-frame YC separated signals 1105 which are divided into Y signals and C signals by an inter-frame filter (not shown), are applied to a second input terminal of the Y signal mixing circuit 1009 and a second terminal of the C signal mixing circuit 1010, respectively. On the other hand, signals 1106 showing the amount of movement of Y signals detected by the Y signal movement detecting circuit 1006 are applied to an input terminal of a composing circuit 1008 while signals 1107 showing the amount of movement of C signals detected by the C signal movement detecting circuit 1007 are applied to the other input terminal of the composing circuit 1008. Motion detecting signals 1108 composed by the composing circuit 1008 are applied to a third input terminal of the Y signal mixing circuit 1009 and a third terminal of the C signal mixing circuit 1010. A motion detecting circuit 1080 comprises the Y signal motion detecting circuit 1006, the C signal motion detecting circuit 1007 and the composing circuit 1008. Motion adaptive YC separated Y signals 1109, which are output from the Y signal mixing circuit 1009, are transferred to the output terminal 1002 and motion adaptive YC separated C signals 1110, which are output from the C signal mixing circuit 1010, are transferred to the output terminal 1003. The operation of FIG. 10 will now be described. In the motion detecting circuit 1080, when the V signals are divided into Y signals and C signals, the composing circuit 1008 composes the output of the Y signal motion detecting circuit 1006 and the output of the C signal motion detecting circuit 1007 to judge that the V signals 1101 are either signals showing a still image or signals showing a moving image. FIG. 111 shows the Y signal motion detecting circuit 1006 in detail. In FIG. 111, V signals 1101 are input to the input terminal 1011 and then signals obtained by delaying the V signals by one-frame in a one-frame delay circuit 1075 are subtracted from the V signals directly input by a subtracter 1076 to find a one-frame difference of the V signals 1101. Then, the one-frame difference is transferred to an absolute value circuit 1078 through a low-pass filter (LPF) 1077 and an absolute value thereof is found. The absolute value is converted to signals 1106, which show the amount of movement of low-frequency component of Y signals, in a non-linear converting circuit 1079 and then output to the output terminal 1081. In addition, FIG. 112 shows the C signal motion detecting circuit 1007 in detail. In FIG. 112, V signals 1101 are input to the input terminal 1011 and then signals obtained by delaying the V signals by two frames in a two-frame delay circuit 1082 are subtracted from the V signals directly input by a subtracter 1083 to find a two-frame difference of the V signals 1101. Then, the two-frame difference is transferred to an absolute value circuit 1085 through a band-pass filter (BPF) 1084 and an absolute value thereof is found. The absolute value is converted to signals 1107, which show the amount of movement of C signals, in a non-linear converting circuit 1086 and then output from the output terminal 1087. The composing circuit 1008 selects a larger value between the amount of movement of Y signals 1106 and the amount of movement of C signals 1107 and outputs it. The result of the judgment is represented in the form of a movement factor k (0.ltoreq.k.ltoreq.1) and, for example, when the image is judged to be a perfect still image, k is equal to 0 and when the image is judged to be a perfect moving image, k is equal to 1. Then, it is transferred to the Y signal mixing circuit 1009 and the C signal mixing circuit 1010 as a control signal 1108. Generally, when the image is a still image, the Y signals and the C signals are separated by performing inter-frame YC separation utilizing an inter-frame correlation. FIG. 113 shows the inter-frame YC separating circuit 1005 in detail. In FIG. 113, V signals 1101 are input to the input terminal 1011 and signals obtained by delaying the V signals by one-frame in the one-frame delay circuit 1088 and the V signals directly input are added by an adder 1089 to find a one-frame sum. Thus obtained Yf signals 1104 are output from the output terminal 1091 while the Yf signals 1104 are subtracted from the V signals 1101 input from the input terminal 1011 by a subtracter 1090, whereby CF signals 1105 are obtained and output from the output terminal 1092. When the image is a moving image, the Y signals and the C signals are separated by performing intra-field YC separation utilizing an intra-field correlation. FIG. 114 shows the intra-field YC separating circuit 1004 in detail. In FIG. 114, V signals 1101 are input to the input terminal 1011 and signals obtained by delaying the V signals by one-line in the one-line delay circuit 1093 and the V signals directly input are added by an adder 1094 to find a one-line sum. Thus obtained YF signals 1102 are output from the output terminal 1096 while the YF signals 1102 are subtracted from the V signals 1101 input from the input terminal 1011 by a subtracter 1095, whereby Cf signals 1103 are obtained and output from the output terminal 1097. In the motion adaptive YC separating filter, the intra-field YC separating circuit 1004 and the inter-frame YC separating circuit 1005 are arranged in parallel and the Y signal mixing circuit 1009 performs the following operation in accordance with the motion factor k composed by the composing circuit 1008, whereby the motion adaptive YC separated Y signals 1109 are output from the output terminal 1002. wherein Yf is the intra-field YC separated Y signal output 1102 and YF is the inter-frame YC separated Y signal output 1104. Similarly, the C signal mixing circuit 1010 performs the following operation in accordance with the control signal 1108, whereby the motion adaptive YC separated C signals 1110 are output from the output terminal 1003. wherein Cf is the intra-field YC separated C signal output 1103 and CF is the inter-frame YC separated C signal output 1105. In the motion adaptive YC separating filter, the C signal motion detecting circuit 1007 may be constructed as shown in FIG. 115. In FIG. 115, V signals 1101 are input from the input terminal 1011 and demodulated to two kinds of color difference signals R-Y and B-Y by a color demodulator 1098. These color difference signals R-Y and B-Y are time-shared and multiplexed at a prescribed frequency in the time-division multiplex circuit 1099 and delayed by two frames in the two-frame delay circuit 1082. Thereafter, the output of the two-frame delay circuit 1082 is subtracted from the output of the time division multiplex circuit 1099 by the subtracter 1083 to obtain a two-frame difference. Then, Y signal component is removed by passing the two-frame difference through the low-pass filter 1084 and an absolute value is obtained by the absolute value circuit 1085. Then, the absolute value is converted to signals 1107 showing the detected amount of movement of the C signals by the non-linear conversion circuit 1086 and then output from the output terminal 1087. FIG. 116 is a block diagram showing another motion adaptive YC separating filter. In FIG. 116, V signals 6201 of NTSC are input to an input terminal 6001 and applied to input terminals of an intra-field Y signal extracting circuit 6004, an inter-frame Y signal extracting circuit 6005, a color demodulation circuit 6006 and a Y signal motion detecting circuit 6011. In the intra-field Y signal extracting filter 6004, the intra-field separated Y signals 6202 are applied to a first input terminal of a Y signal mixing circuit 6014. In addition, in the inter-frame Y signal extracting filter 6005, the inter-frame YC separated Y signals 6203 are applied to a second input terminal of a Y signal mixing circuit 6014. In the color demodulation circuit 6006, the V signals are demodulated to two kinds of color-difference signals, i.e., R-Y signals and B-Y signals. These color-difference signals are time-shared and multiplexed at a prescribed frequency in the time-division multiplex circuit 6007. The output signals from the time-division multiplex circuit 6007 are band restricted by a low-pass filter (LPF) 6008 whose band pass is 1.5 MHz and below. The band-restricted color-difference signals 6204 is applied to the intra-field C signal extracting filter 6009, the inter-frame C signal extracting filter 6010 and the C signal motion detecting circuit 6012. In the intra-field C signal extracting filter 6009, the intra-field YC separated C signals 6205 are applied to a first input terminal of a C signal mixing circuit 6015. In addition, in the inter-frame C signal extracting filter 6010, the inter-frame YC separated C signals 6206 are applied to a second input terminal of a C signal mixing circuit 6015. On the other hand, signals 6207 showing the amount of movement of Y signals detected by the Y signal motion detecting circuit 6011 are applied to an input terminal of a composing circuit 6013 while signals 6208 showing the amount of movement of C signals detected by the C signal motion detecting circuit 6012 are applied to the other input terminal of the composing circuit 6013. Motion detecting signals 6209 composed by the composing circuit 6013 are applied to a third input terminal of the Y signal mixing circuit 6014 and a third input terminal of the C signal mixing circuit 6015. A motion detecting circuit 6080 comprises the Y signal motion detecting circuit 6011, the C signal motion detecting circuit 6012 and the composing circuit 6013. Motion adaptive YC separated Y signals 6210, which are output from the Y signal mixing circuit 6014, are transferred to the output terminal 6002 and motion adaptive YC separated C signals 6211, which are output from the C signal mixing circuit 6015, are transferred to the output terminal 6003. The operation of the FIG. 16 circuit will be described. In the motion detecting circuit 6080, when the V signals are divided into Y signals and C signals, the composing circuit 6013 composes the output of the Y signal motion detecting circuit 6011 and the output of the C signal motion detecting circuit 6012 to judge that the V signals 6201 are either signals showing a still image or signals showing a moving image. FIG. 117 shows the Y signal motion detecting circuit 6011 in detail. In FIG. 117, V signals 6201 are input to the input terminal 6021 and then signals obtained by delaying the V signals by one-frame in a one-frame delay circuit 6151 are subtracted from the V signals directly input by a subtracter 6152 to find a one-frame difference of the V signals 6201. Then, the one-frame difference is transferred to an absolute value circuit 6154 through a LPF 6153 whose band pass is 2.1 MHz and below and an absolute value thereof is found. The absolute value is converted to signals 6207, which show the movement of low-frequency component of Y signals, in a non-linear converting circuit 6155 and output to the output terminal 6156. In addition, FIG. 118 shows the C signal motion detecting circuit 6012 in detail. In FIG. 118, the band restricted color-difference signals 6204 are input to the input terminal 6023 and then signals obtained by delaying the color-difference signals by two frames in a two-frame delay circuit 6157 are subtracted from the color-difference signals 6204 directly input by a subtracter 6158 to find a two-frame difference of the color-difference signals 6204. Then, an absolute value of the two-frame difference is found in an absolute circuit 6159, and the absolute value is converted to signals 6208, which show the amount of movement of C signals, in a non-linear converting circuit 6160 and then output from the output terminal 6161. The composing circuit 6013 selects a larger value between the amount of movement of Y signals 6207 and the amount of movement of C signals 6208 and outputs it. The result of the judgment is represented in the form of a motion factor k (0.ltoreq.k.ltoreq.1) and, for example, when the image is judged to be a perfect still image, k is equal to 0 and when it is judged to be a perfect moving image, k is equal to 1. Then, it is transferred to the Y signal mixing circuit 6014 and the C signal mixing circuit 6015 as control signals 6209. Generally, when the image is a still image, the Y signals and the C signals are separated by performing YC separation using an the inter-frame Y signal extracting filter 6005 and the inter-frame C signal extracting filter 6010 utilizing an inter-frame correlation. FIG. 119 shows the inter-frame Y signal extracting filter 6005 in detail. In FIG. 119, V signals 6201 are input to the input terminal 6021 and signals obtained by delaying the V signals by one frame in the one-frame delay circuit 6162 and the V signals directly input are added by an adder 6163 to find a one-frame sum. Thus obtained YF signals 6203 are output to the output terminal 6164. FIG. 121 shows the inter-frame C signal extracting filter 6010 in detail. In FIG. 121, color-difference signals 6204 are input to the input terminal 6023 and signals obtained by delaying the color-difference signals 6204 by one frame in the one-frame delay circuit 6168 and the color-difference signals 6204 directly input are added by an adder 6169 to find a one-frame sum. Thus obtained Cf signals 6206 are output to the output terminal 6170. Generally, when the image is a moving image, the Y signals and the C signals are separated by performing YC separation using the intra-field Y signal extracting filter 6004 and the intra-field C signal extracting filter 6009 utilizing an intra-field correlation. FIG. 120 shows the intra-field Y signal extracting filter 6004 in detail. In FIG. 120, V signals 6201 are input to the input terminal 6021 and signals obtained by delaying the V signals by one-line and the V signals directly input are added by an adder 6166 to find a one-line sum. Thus obtained Yf signals 6202 are output from the output terminal 6167. FIG. 122 shows the intra-field C signal extracting filter 6009 in detail. In FIG. 122, color-difference signals are input to the input terminal 6023 and signals obtained by delaying the color-difference signals by one line in the one-line delay circuit 6171 and the color-difference signals 6204 directly input are added by an adder 6172 to find a one-line sum. Thus obtained Cf signals 6205 are output from the output terminal 6173. In the motion adaptive YC separating filter, the intra-field Y signal extracting filter 6004 and the inter-frame Y signal extracting filter 6005 are arranged in parallel and the Y signal mixing circuit 6014 performs the following operation in accordance with the control signal 6209, i.e., the motion factor k composed by the composing circuit 6013, whereby the motion adaptive YC separated Y signals 6210 are output from the output terminal 6002. wherein Yf is the intra-field YC separated Y signal output 6202 and YF is the inter-frame YC separated Y signal output 6203. Similarly, the intra-field C signal extracting filter 6009 and the inter-frame C signal extracting filter 6010 are arranged in parallel and the C signal mixing circuit 6015 performs the following operation in accordance with the control signal 6209, whereby the motion adaptive YC separated C signals 6211 are output from the output terminal 6003. wherein Cf is the intra-field YC separated C signal output 6205 and CF is the inter-frame YC separated C signal output 6206. In the conventional YC separating filter adaptive to the movement of image shown in FIG. 110, the Yf signals obtained by the intra-field YC separating circuit 1004 and the YF signals obtained by the inter-frame YC separating circuit 1005 are mixed on the basis of the amount obtained by composing the amount of movement detected by the Y signal motion detecting circuit 1006 and the amount of movement detected by the C signal movement detecting circuit 1007. Similarly, the Cf signals obtained by the intra-field YC separating circuit 1004 and the CF signals obtained by the inter-frame YC separating circuit 1005 are mixed on the basis of the composed amount of movement. In the YC separating filter adaptive to the movement of image shown in FIG. 116, the Yf signals obtained by the intra-field Y signal extracting filter 6004 and the YF signals obtained by the inter-frame Y signal extracting filter 6005 are mixed on the basis of the amount obtained by composing the amount of movement detected by the Y signal movement detecting circuit 6011 and the amount of movement detected by the C signal motion detecting circuit 6012. Similarly, the Cf signals obtained by the intra-field C signal extracting filter 6009 and the CF signals obtained by the inter-frame C signal extracting filter 6010 are mixed on the basis of the composed amount of movement. In the above-described conventional examples, the filter characteristic in the still image is completely different from that in the moving image, so that the resolution changes when the image changes from the still image to the moving image or from the moving image to the still image, with the result that the quality of the image deteriorates while processing the moving image. SUMMARY OF THE INVENTION It is an object of the present invention to provide a YC separating filter adaptive to a movement of an image that ensures a high resolution and that reproduces an image having less deterioration in quality. Other objects and advantages of the present invention will become apparent from the detailed description given hereinafter; it should be understood, however, that the detailed description and specific embodiment are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. According to a first aspect of the present invention, a YC separating filter adaptive to a movement of an image partially detects a correlation between fields or between frames and a correlation in a field when a motion detecting circuit detects a moving image, performs a separation utilizing the correlations to output an intra-frame YC separated Y signal and an intra-frame YC separated C signal, mixes an inter-frame YC separated C signal and the intra-frame YC separated C signal on the basis of the output of the motion detecting circuit to output a motion adaptive YC separated C signal, and mixes an inter-frame YC separated Y signal and the intra-frame YC separated Y signal on the basis of the output of the motion detecting circuit to output a motion adaptive YC separated Y signal. Therefore, the filter process can be changed according as the image is a moving image or a still image, whereby a difference in the qualities between the moving image and the still image caused by the filter process can be reduced. According to a second aspect of the present invention, in a YC separating filter adaptive to a movement of an image, when a motion detecting circuit detects a moving image, an intra-field correlation judge circuit includes vertical direction non-correlation energy detecting means for excluding a d.c. component in the vertical direction and a frequency component corresponding to a color sub-carrier wave component from a frequency component of a particular sampling point and finding an absolute value of the remaining frequency component to detect a vertical direction non-correlation energy; horizontal direction high-frequency Y signal energy detecting means for extracting a frequency component, which is a low-frequency component in the vertical direction and corresponds to a half of a color sub-carrier frequency in the horizontal direction, from the frequency component of the particular sampling point and finding an absolute value of the extracted component to detect a horizontal direction high-frequency Y signal energy; vertical correlation detecting means for comparing the vertical direction non-correlation energy with a first set value and comparing the horizontal direction high-frequency Y signal energy with a second set value, and deciding that a correlation is present in the vertical direction when the vertical direction non-correlation energy is smaller than the first set value and the horizontal direction high-frequency Y signal energy is larger than the second set value; horizontal direction non-correlation energy detecting means for excluding a d.c. component in the horizontal direction and a frequency component corresponding to a color sub-carrier component from a frequency component of the particular sampling point and finding an absolute value of the remaining frequency component to detect horizontal direction non-correlation energy; vertical direction high-frequency Y signal energy detecting means for extracting a frequency component, which is a low-frequency component in the horizontal direction and corresponds to a half of a color sub-carrier frequency in the vertical direction, from the frequency component of the particular sampling point and fining an absolute value of the extracted components to detect a vertical direction high-frequency Y signal energy; horizontal correlation detecting means for comparing the horizontal direction non-correlation energy with a third set value and comparing the vertical direction high-frequency Y signal energy with a fourth set value, and deciding that a correlation is present in the horizontal direction when the horizontal direction non-correlation energy is smaller than the third set value and the vertical direction high-frequency Y signal energy is larger than the fourth set value; and means for sending a control signal for selecting an output from outputs of a plurality of filters, which perform inter-field processes, in accordance with the result of the detections. Therefore, a filter according to the image is selected also in the field using the correlation of the image when a motion detecting circuit detects a moving image. According to a third aspect of the present invention, a YC separating filter adaptive to a movement of an image includes an intra-frame YC separating circuit. The intra-frame YC separating circuit partially detects correlations in plural directions between fields by a horizontal low-frequency component of a difference between sampling points having opposite phases of color sub-carrier between fields when the motion detecting circuit detects a moving image and selects an optimum one from a plurality of inter-field operations in accordance with the result of the detection. Further, it partially detects correlations in a field and selects an optimum one from a plurality of intra-field processes in accordance with the result of the detection. In this way, the intra-frame YC separating circuit outputs intra-frame YC separated Y signals and intra-frame YC separated C signals. Therefore, a direction in which the image moves is detected, whereby an inter-field operation appropriate for the movement of the image is performed. According to a fourth aspect of the present invention, a YC separating filter adaptive to a movement of an image includes an intra-frame YC separating circuit. The intra-frame YC separating circuit partially detects correlations in plural directions between fields by a horizontal low-frequency component of a difference between sampling points having the same phases of color sub-carrier between fields and a horizontal high-frequency component of a sum of sampling points having opposite phases of color sub-carrier between fields when the motion detecting circuit detects a moving image, and selects an optimum one from a plurality of inter-field operations in accordance with the result of the detection. Further, it partially detects correlations in a field and selects an optimum one from three kinds of intra-field processes in response to the result of the detection. Thus, intra-frame YC separated Y signals and intra-frame YC separated C signals are output. Therefore, a direction in which the image moves is detected, whereby an inter-field operation appropriate for the movement of the image is performed. According to a fifth aspect of the present invention, a YC separating filter adaptive to a movement of an image includes an intra-frame YC separating circuit. The intra-frame YC separating circuit partially detects correlations in plural directions between frames by a difference between sampling points having the same phases of color sub-carrier between frames when the motion detecting circuit detects a moving image, and selects an optimum one from a plurality of inter-field operations in accordance with the result of the detection. Further, it partially detects correlations in a field and selects an optimum one from a plurality of intra-field processes in accordance with the result of the detection. Thereby, the band of the C signal is restricted. In this way, the intra-frame YC separating circuit outputs intra-frame YC separated Y signal and intra-frame YC separated C signals. Therefore, a direction in which the image moves is detected, whereby an inter-field operation appropriate for the movement of the image is performed. According to a sixth aspect of the present invention, a YC separating filter adaptive to a movement of an image includes an intra-frame YC separating circuit. The intra-frame YC separating circuit partially detects correlations in plural directions between frames or between fields when the motion detecting circuit detects a moving image, and selects an optimum one from a plurality of inter-field operations when it is judged that a correlation is present in some direction while it performs no inter-field operation when it is judged that no correlation is present. Further, it partially detects correlations in a field and selects an optimum one from a plurality of intra-field processes in accordance with the result of the detection. Thereby, the band of the C signal is restricted. In this way, the intra-frame YC separating circuit outputs intra-frame YC separated Y signals and intra-frame YC separated C signals. Therefore, a deterioration of the quality of the image caused by the inter-field operation is prevented. According to a seventh aspect of the present invention, a YC separating filter adaptive to a movement of an image includes an isolated point eliminating circuit. When the motion detecting circuit detects a moving image, the isolated point eliminating circuit partially detects a correlation between fields and corrects the result of the detection when the result is an isolated point. An optimum one is selected from a plurality of intra-frame processes including inter-field operations in accordance with the result of the isolated point eliminating circuit, whereby intra-frame YC separated Y signals and intra-frame YC separated C signals are output. Therefore, the detection of the correlation is possible after removing the isolated point, whereby the quality of the image is improved. According to an eighth aspect of the present invention, a YC separating filter adaptive to a movement of an image includes an isolated point eliminating circuit which detects directions, in which inter-field correlations are present, in the particular sampling point and the neighboring sampling points from the output of said correlation detecting circuit and selects the most numerous direction to decide the inter-field correlation of the particular sampling point. Therefore, the detection of the correlation is possible after removing the isolated point, whereby the quality of the image is improved. According to a ninth aspect of the present invention, a YC separating filter adaptive to a movement of an image includes an isolated point eliminating circuit which detects directions, in which inter-field correlations are present, in the particular sampling point and the neighboring sampling points from the output of the correlation detecting circuit, and selects the most numerous direction from the detected results to which weights are applied, thereby to decide the inter-field correlation at the particular sampling point. Therefore, the detection of the correlation is possible after removing the isolated point, whereby the quality of the image is improved. According to a tenth aspect of the present invention, a YC separating filter adaptive to a movement of an image includes an isolated point eliminating circuit which adds and compares inter-field correlation values in plural directions in the particular sampling point and the neighboring sampling points, whereby the inter-field correlation at the particular sampling point is decided. Therefore, the detection of the correlation is possible after removing the isolated point, whereby the quality of the image is improved. According to an eleventh aspect of the present invention, a YC separating filter adaptive to a movement of an image includes an isolated point eliminating circuit which adds and compares inter-field correlation values in plural directions, to which weights are applied, in the particular sampling point and the neighboring sampling points, whereby the inter-field correlation at the particular sampling point is decided. Therefore, the detection of the correlation is possible after removing the isolated point, whereby the quality of the image is improved. According to a twelfth aspect of the present invention, a YC separating filter adaptive to a movement of an image includes an isolated point eliminating circuit which adds and compares inter-field correlation values in plural directions in the particular sampling point and the neighboring sampling points and selects the most numerous direction to decide the inter-field correlation at the particular sampling point. Therefore, the detection of the correlation is possible after removing the isolated point, whereby the quality of the image is improved. According to a thirteenth aspect of the present invention, a YC separating filter adaptive to a movement of an image includes an isolated point eliminating circuit which adds and compares inter-field correlation values, to which weights are applied, in plural directions in the particular sampling point and the neighboring sampling points, and detects the most numerous direction from the obtained results to which weights are applied, to decide the inter-field correlation at the particular sampling point. Therefore, the detection of the correlation is possible after removing the isolated point, whereby the quality of the image is improved. According to a fourteenth aspect of the present invention, a YC separating filter adaptive to a movement of an image includes a motion detecting circuit partially detecting a movement of an image utilizing a correlation between frames; an inter-frame Y signal extracting filter which performs a separation utilizing the inter-frame correlation when the motion detecting circuit detects a still image, and outputs intra-frame YC separated Y signals; an intra-frame Y signal extracting filter which detects a correlation between fields or between frames and a correlation in a field when the motion detecting circuit detects a moving image, performs a separation utilizing the correlations, and outputs intra-frame YC separated Y signals; a Y signal mixing circuit which mixes the inter-frame YC separated Y signals and the intra-frame YC separated Y signals in accordance with an output of the motion detecting circuit and outputs motion adaptive YC separated Y signals; a color demodulation circuit which demodulates composite color television signals to color difference signals; an inter-frame C signal extracting filter which performs a separation utilizing the inter-frame correlation when the motion detecting circuit detects a still image and outputs inter-frame YC separated C signals; an intra-frame C signal extracting filter which detects a correlation between fields or between frames when the motion detecting circuit detects a moving image, performs a separation utilizing the correlations, and outputs intra-frame YC separated C signals; and a C signal mixing circuit which mixes the inter-frame YC separated C signals and the intra-frame YC separated C signals in accordance with the output of the motion detecting circuit and outputs motion adaptive YC separated C signals. The Y signals and the C signals are separately processed. Therefore, when there is a difference in directions of the correlation of the image between the Y signal and the C signal, the Y signal and the C signal are processed separately from each other. According to a fifteenth aspect of the present invention, a YC separating filter adaptive to a movement of an image includes an intra-field correlation judge circuit comprising vertical direction non-correlation energy detecting means for excluding a d.c. component in the vertical direction and a frequency component corresponding to a color sub-carrier component from a frequency component of a particular sampling point and finding an absolute value of the remaining frequency component to detect a vertical direction non-correlation energy; horizontal direction high-frequency Y signal energy detecting means for extracting a frequency component, which is a low-frequency component in the vertical direction and corresponds to a half of a color sub-carrier frequency in the horizontal direction, from the frequency component of the particular sampling point and finding an absolute value of the extracted component to detect a horizontal direction high-frequency Y signal energy; vertical correlation detecting means for comparing the vertical direction non-correlation energy with a first set value and comparing the horizontal direction high-frequency Y signal energy with a second set value, and deciding that a correlation is present in the vertical direction when the vertical direction non-correlation energy is smaller than the first set value and the horizontal direction high-frequency Y signal energy is larger than the second set value; horizontal direction non-correlation energy detecting means for excluding a d.c. component in the horizontal direction and a frequency component corresponding to a color sub-carrier component from a frequency component of the particular sampling point and finding an absolute value of the remaining frequency component to detect a horizontal direction non-correlation energy; vertical direction high-frequency Y signal energy detecting means for extracting a frequency component, which is a low-frequency component in the horizontal direction and corresponds to a half of a color sub-carrier frequency in the vertical direction, from the frequency component of the particular sampling point and fining an absolute value of the extracted components to detect a vertical direction high-frequency Y signal energy; horizontal correlation detecting means for comparing the horizontal direction non-correlation energy with a third set value and comparing the vertical direction high-frequency Y signal energy with a fourth set value, and deciding that a correlation is present in the horizontal direction when the horizontal direction non-correlation energy is smaller than the third set value and the vertical direction high-frequency Y signal energy is larger than the fourth set value; and means for sending a control signal for selecting an output from outputs of a plurality of filters, which perform inter-field processes, in accordance with the result of the detections. Therefore, a filter according to the image is selected also in the field using the correlation of the image when a motion detecting circuit detects a moving image. According to a sixteenth aspect of the present invention, a YC separating filter adaptive to a movement of an image, in which Y signals and C signals are separately processed, includes an intra-frame Y signal extracting filter. When the motion detecting circuit detects a moving image, the intra-frame Y signal extracting filter partially detects correlations in plural directions between fields by a horizontal low-frequency component of a difference between sampling points having opposite phases of the color sub-carrier between fields, and selects an optimum one from a plurality of inter-field operations in accordance with the result of the detection. Further, it partially detects a correlation in a field and selects an optimum one from a plurality of intra-field processes in accordance with the result of the detection. Thereby the band of the C signals is restricted. In this way, the intra-frame Y signal extracting filter outputs intra-frame YC separated Y signals. Therefore, a direction in which the image moves is detected, whereby an inter-field operation appropriate for the movement of the image is performed. According to a seventeenth aspect of the present invention, a YC separating filter adaptive to a movement of an image, in which Y signals and C signals are separately processed, includes an intra-frame Y signal extracting filter. When the motion detecting circuit detects a moving image, the intra-frame Y signal extracting filter partially detects correlations in plural directions between fields by a horizontal low-pass frequency component of a difference between sampling points having the same phases of color sub-carrier of the composite color television signal between fields and a horizontal high-frequency component of a sum of sampling points having opposite phases of color sub-carrier of the composite color television signal between fields, and selects an optimum one from a plurality of inter-field operations in accordance with the result of the detection. Further, it partially detects a correlation in a field and selects an optimum one from a plurality of intra-field processes in accordance with the result of the detection. In this way, the intra-frame Y signal extracting filter outputs intra-frame YC separated Y signals. Therefore, a direction in which the image moves is detected, whereby an inter-field operation appropriate for the movement of the image is performed. According to an eighteenth aspect of the present invention, a YC separating filter adaptive to a movement of an image, in which Y signals and C signals are separately processed, includes an intra-frame Y signal extracting filter. When the motion detecting circuit detects a moving image, the intra-frame Y signal extracting filter partially detects correlations in plural directions between frames by a difference between sampling points having the same phases of color sub-carrier between frames, and selects an optimum one from a plurality of inter-field operations in accordance with the result of the detection. Further, it partially detects a correlation in a field and selects an optimum one from a plurality of intra-field processes in accordance with the result of the detection. In this way, the intra-frame Y signal extracting filter outputs intra-frame YC separated Y signals. Therefore, a direction in which the image moves is detected, whereby an inter-field operation appropriate for the movement of the image is performed. According to a nineteenth aspect of the present invention, a YC separating filter adaptive to a movement of an image, in which Y signals and C signals are separately processed, includes an intra-frame C signal extracting filter. When the motion detecting circuit detects a moving image, the intra-frame C signal extracting filter partially detects correlations in plural directions between fields by a horizontal low- frequency component of a difference between sampling points having opposite phases of color sub-carrier between fields, and selects an optimum one from a plurality of inter-field operations in accordance with the result of the detection to restrict the band of the color difference signals. Thus, the intra-frame C signal extracting filter outputs intra- frame YC separated C signals. Therefore, a direction in which the image moves is detected, whereby an inter-field operation appropriate for the movement of the image is performed. According to a twentieth aspect of the present invention, a YC separating filter adaptive to a movement of an image, in which Y signals and C signals are separately processed, includes an intra-frame C signal extracting filter. When the motion detecting circuit detects a moving image, the intra-frame C signal extracting filter partially detects correlations in plural directions between fields by a difference between sampling points having the same phases of color sub-carrier between frames, and selects an optimum one from a plurality of inter-field processes in accordance with the result of the detection to restrict the band of the color difference signals. Thus, the intra-frame C signal extracting filter outputs intra-frame YC separated C signals. Therefore, a direction in which the image moves is detected, whereby an inter-field operation appropriate for the movement of the image is performed. According to a twenty-first aspect of the present invention, a YC separating filter adaptive to a movement of an image, in which Y signals and C signals are separately processed, includes an intra-frame C signal extracting filter. When the motion detecting circuit detects a moving image, the intra-frame C signal extracting filter partially detects correlations in plural directions between fields by a horizontal low-frequency component of a difference between sampling points having opposite phases of color sub-carrier of the composite color television signal between fields. When it is judged that a correlation is present in some direction, the band of the color difference signals is restricted by selecting an optimum one from a plurality of inter-field operations in accordance with the result of the detection. When it is judged that no correlation is present, the band of the color difference signals is restricted by the intra-field process. Thus, the intra-frame C signal extracting filter outputs intra-frame YC separated C signals. Therefore, a deterioration of the quality of the image caused by the inter-field operation is prevented. According to a twenty-second aspect of the present invention, a YC separating filter adaptive to a movement of an image, in which Y signals and C signals are separately processed, includes an intra-frame C signal extracting filter. When the motion detecting circuit detects a moving image, the intra-frame C signal extracting filter partially detects correlation in plural directions between fields by a difference between sampling points having the same phases of color sub-carrier between frames. When it is judged that a correlation is present in some direction, the band of the color difference signals is restricted by selecting an optimum one from a plurality of inter-field operations in accordance with the result of the detection. When it is judged that no correlation is present, the band of the color difference signals is restricted by the intra-field process. Thus, the intra-frame C signal extracting filter outputs intra-frame YC separated C signals. Therefore, a deterioration of the quality of the image caused by the inter-field operation is prevented. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram in accordance with an embodiment of the present invention; FIG. 2 is a block diagram showing first examples of an inter-field correlation detecting circuit, an intra-field correlation detecting circuit, and an intra-frame YC separating circuit according to the first embodiment of FIG. 1; FIG. 3 is a block diagram showing second examples of the inter-field correlation detecting circuit, the intra-field correlation detecting circuit, and the intra-frame YC separating circuit according to the first embodiment of FIG. 1; FIG. 4 is a block diagram showing third examples of the inter-field correlation detecting circuit, the intra-field correlation detecting circuit, and the intra-frame YC separating circuit according to the first embodiment of FIG. 1; FIG. 5 is a block diagram showing fourth examples of the inter-field correlation detecting circuit, the intra-field correlation detecting circuit, and the intra-frame YC separating circuit according to the first embodiment of FIG. 1; FIG. 6 is a block diagram showing an example of an intra-field correlation judge circuit shown in FIGS. 2 to 5; FIG. 7 is a plan view showing an arrangement of the V signal, which is digitized by a frequency four times the color sub-carrier frequency, in the three-dimensional time space by the t-axis and the y-axis; FIG. 8 is a plan view showing an arrangement of the same V signal by the x-axis and the y axis; FIG. 9 is a perspective view showing a spectral dispersion of V signals in the three-dimensional frequency space; FIG. 10 is a diagram showing the spectral dispersion of FIG. 9 viewed from the minus side of the f-axis; FIG. 11 is a diagram showing the spectral dispersion of FIG. 9 viewed from the plus side of the .mu.-axis; FIG. 12 is a block diagram in accordance with an embodiment of the present invention; FIG. 13 is a block diagram showing first examples of an inter-frame correlation detecting circuit, an intra-field correlation detecting circuit, and an intra-frame YC separating circuit shown in FIG. 12; FIG. 14 is a block diagram showing second examples of the inter-frame correlation detecting circuit, the intra-field correlation detecting circuit, and the intra-frame YC separating circuit shown in FIG. 12; FIG. 15 is a block diagram showing a first example of an inter-field correlation detecting circuits shown in FIGS. 13 and 14; FIG. 16 is a plan view showing an arrangement of the V signal, which is digitized by a frequency four times the color sub-carrier frequency, in the three-dimensional time space by the t-axis and the y-axis; FIG. 17 is a plan view showing an arrangement of the same V signal by the x-axis and the y-axis; FIG. 18 is a plan view showing an arrangement of the same V signal by the x-axis and the y-axis; FIG. 19 is a perspective view showing a spectral dispersion of V signals in the three-dimensional frequency space; FIG. 20 is a diagram showing the spectral dispersion of FIG. 19 viewed from the minus side of the f-axis; FIG. 21 is a diagram showing the spectral dispersion of FIG. 19 viewed from the plus side of the .mu.-axis; FIG. 22 is a block diagram showing a YC separating filter adaptive to a movement of an image in accordance with an embodiment of the present invention; FIG. 23 is a block diagram showing a first example of an isolated point eliminating circuit shown in FIG. 22; FIG. 24 is a block diagram showing a second example of the isolated point eliminating circuit shown in FIG. 22; FIG. 25 is a block diagram showing a first example of a correlation detecting circuit shown in FIG. 22; FIG. 26 is a block diagram showing a second example of the correlation detecting circuit shown in FIG. 22; FIG. 27 is a block diagram showing a third example of the correlation detecting circuit shown in FIG. 22; FIG. 28 is a block diagram showing a first example of an intra-frame YC separating circuit shown in FIG. 22; FIG. 29 is a block diagram showing a second example of the intra-frame YC separating circuit shown in FIG. 22; FIG. 30 is a block diagram showing a third example of the intra-frame YC separating circuit shown in FIG. 22; FIG. 31 is a block diagram showing a fourth example of the intra-frame YC separating circuit shown in FIG. 22; FIG. 32 is a block diagram showing an intra-field BPF in the intra-frame YC separating circuits shown in FIGS. 28 and 29; FIG. 33 is a block diagram showing another example of the intra-field BPF in the intra-frame YC separating circuits shown in FIGS. 28 and 29; FIG. 34 is a plan view showing an arrangement of the same V signal, by the t-axis and the y-axis; FIG. 35 is a plan view showing an arrangement of the same V signal by the x-axis and the y-axis; FIGS. 36(a) to 36(c) are a perspective view, a view from the minus side of the f-axis, and a view from the plus side of the .mu.-axis, of a spectral dispersion of V signals in the three-dimensional frequency space; FIGS. 37(a) to 37(c) are a perspective view, a view from the minus side of the f-axis, and a view from the plus side of the .mu.-axis, of a spectral dispersion of Y signals and C signals obtained by an inter-field YC separation A1, in the three-dimensional frequency space; FIGS. 38(a) to 38(c) are a perspective view, a view from the minus side of the f-axis, and a view from the plus side of the .mu.-axis, of a spectral dispersion of Y signals and C signals obtained by an inter-field YC separation B1, in the three-dimensional frequency space; FIGS. 39(a) to 39(c) are a perspective view, a view from the minus side of the f-axis, and a view from the plus side of the .mu.-axis, of a spectral dispersion of Y signals and C signals obtained by an inter-field YC separation C1, in the three-dimensional frequency space; FIGS. 40(a) to 40(c) are a perspective view, a view from the minus side of the f-axis, and a view from the plus side of the .mu.-axis, of a spectral dispersion of Y signals and C signals obtained by an inter-field YC separation A2, in the three-dimensional frequency space; FIGS. 41(a) to 41(c) are a perspective view, a view from the minus side of the f-axis, and a view from the plus side of the .mu.-axis, of a spectral dispersion of Y signals and C signals obtained by an inter-field YC separation B2, in the three-dimensional frequency space; FIGS. 42(a) to 42(c) are a perspective view, a view from the minus side of the f-axis, and a view from the plus side of the .mu.-axis, of a spectral dispersion of Y signals and C signals obtained by an inter-field YC separation C2, in the three-dimensional frequency space; FIG. 43 is a block diagram showing a YC separating filter adaptive to a movement of an image in accordance with an embodiment of the present invention; FIG. 44 is a block diagram showing a first example of an isolated point eliminating circuit shown in FIG. 43; FIG. 45 is a block diagram showing a second example of the isolated point eliminating circuit shown in FIG. 43; FIG. 46 is a block diagram showing an absolute value circuit in the isolated point eliminating circuit shown in FIG. 45; FIG. 47 is a block diagram showing a first example of a correlation detecting circuit shown in FIG. 43; FIG. 48 is a block diagram showing a second example of the correlation detecting circuit shown in FIG. 43; FIG. 49 is a block diagram showing a third example of the correlation detecting circuit shown in FIG. 43; FIG. 50 is a block diagram showing a first example of an intra-frame YC separating circuit shown in FIG. 43; FIG. 51 is a block diagram showing a second example of the intra-frame YC separating circuit shown in FIG. 43; FIG. 52 is a block diagram showing a third example of the intra-frame YC separating circuit shown in FIG. 43; FIG. 53 is a block diagram showing a fourth example of the intra-frame YC separating circuit shown in FIG. 43; FIG. 54 is a block diagram showing an intra-field BPF in the intra-frame YC separating circuits shown in FIGS. 50 and 51; FIG. 55 is a block diagram showing another example of the intra-field BPF in the intra-frame YC separating circuits shown in FIGS. 50 and 51; FIG. 56 is a block diagram showing another example of the signal selecting circuit in the intra-frame YC separating circuits shown in FIGS. 50 to 53; FIG. 57 is a plan view showing an arrangement of the V signal, which is digitized by a frequency four times the color sub-carrier frequency, in the three-dimensional time space by the t-axis and the y-axis: FIG. 58 is a plan view showing an arrangement of the V signal, which is digitized by a frequency four times the color sub-carrier frequency, in the three-dimensional time space by the x-axis and the y-axis; FIGS. 59(a) to 59(c) are a perspective view, a view from the minus side of the f-axis, and a view from the plus side of the .mu.-axis, of a spectral dispersion of V signals in the three-dimensional frequency space; FIGS. 60(a) to 60(c) are a perspective view, a view from the minus side of the f-axis, and a view from the plus side of the .mu.-axis, of a spectral dispersion of Y signals and C signals obtained by an inter-field YC separation A1, in the three-dimensional frequency space; FIGS. 61(a) to 61(c) are a perspective view, a view from the minus side of the f-axis, and a view from the plus side of the y-axis, of a spectral dispersion of Y signals and C signals obtained by an inter-field YC separation B1, in the three-dimensional frequency space; FIGS. 62(a) to 62(c) are a perspective view, a view from the minus side of the f-axis, and a view from the plus side of the .mu.-axis, of a spectral dispersion of Y signals and C signals obtained by an inter-field YC separation C1, in the three-dimensional frequency space; FIGS. 63(a) to 63(c) are a perspective view, a view from the minus side of the f-axis, and a view from the plus side of the .mu.-axis, of a spectral dispersion of Y signals and C signals obtained by an inter-field YC separation A2, in the three-dimensional frequency space; FIGS. 64(a) to 64(c) are a perspective view, a view from the minus side of the f-axis, and a view from the plus side of the .mu.-axis, of a spectral dispersion of Y signals and C signals obtained by an inter-field YC separation B2, in the three-dimensional frequency space; FIGS. 65(a) to 65(c) are a perspective view, a view from the minus side of the f-axis, and a view from the plus side of the .mu.-axis, of a spectral dispersion of Y signals and C signals obtained by an inter-field YC separation C2, in the three-dimensional frequency space; FIG. 66 is a block diagram showing a YC separating filter adaptive to a movement of an image in accordance with an embodiment of the present invention; FIG. 67 is a block diagram showing an isolated point eliminating circuit shown in FIG. 66; FIG. 68 is a block diagram showing an absolute value adding circuit according to a first example of the isolated point eliminating circuit shown in FIG. 67; FIG. 69 is a block diagram showing a majority decision circuit according to the first example of the isolated point eliminating circuit shown in FIG. 67; FIG. 70 is a block diagram showing an absolute value adding circuit according to a second example of the isolated point eliminating circuit shown in FIG. 67; FIG. 71 is a block diagram showing a majority decision circuit according to the second example of the isolated point eliminating circuit shown in FIG. 67; FIG. 72 is a block diagram showing a first example of a correlation detecting circuit shown in FIG. 66; FIG. 73 is a block diagram showing a second example of the correlation detecting circuit shown in FIG. 66; FIG. 74 is a block diagram showing a third example of the correlation detecting circuit shown in FIG. 66; FIG. 75 is a block diagram showing a first example of an intra-frame YC separating circuit shown in FIG. 66; FIG. 76 is a block diagram showing a second example of the intra-frame YC separating circuit shown in FIG. 66; FIG. 77 is a block diagram showing a third example of the intra-frame YC separating circuit shown in FIG. 66; FIG. 78 is a block diagram showing a fourth example of the intra-frame YC separating circuit shown in FIG. 66; FIG. 79 is a block diagram showing an intra-field BPF in the intra-frame YC separating circuits shown in FIGS. 75 and 76; FIG. 80 is a block diagram showing another example of the intra-field BPF in the intra-frame YC separating circuits shown in FIGS. 75 and 76; FIG. 81 is a plan view showing an arrangement of the V signal, which is digitized by a frequency four times the color sub-carrier wave frequency, in the three-dimensional time space by the t-axis and the y-axis; FIG. 82 is a plan view showing an arrangement of the V signal, which is digitized by a frequency four times the color sub-carrier wave frequency, in the three-dimensional time space by the x-axis and the y-axis; FIGS. 83(a) to 83(c) are a perspective view, a view from the minus side of the f-axis, and a view from the plus side of the .mu.-axis, of a spectral dispersion of V signals in the three-dimensional frequency space; FIGS. 84(a) to 84(c) are a perspective view, a view from the minus side of the f-axis, and a view from the plus side of the .mu.-axis, of a spectral dispersion of Y signals and C signals obtained by an inter-field YC separation A1, in the three-dimensional frequency space; FIGS. 85(a) to 85(c) are a perspective view, a view from the minus side of the f-axis, and a view from the plus side of the .mu.-axis, of a spectral dispersion of Y signals and C signals obtained by an inter-field YC separation B1, in the three-dimensional frequency space; FIGS. 86(a) to 86(c) are a perspective view, a view from the minus side of the f-axis, and a view from the plus side of the .mu.-axis, of a spectral dispersion of Y signals and C signals obtained by an inter-field YC separation C1, in the three-dimensional frequency space; FIGS. 87(a) to 87(c) are a perspective view, a view from the minus side of the f-axis, and a view from the plus side of the .mu.-axis, of a spectral dispersion of Y signals and C signals obtained by an inter-field YC separation A2, in the three-dimensional frequency space; FIGS. 88(a) to 88(c) are a perspective view, a view from the minus side of the f-axis, and a view from the plus side of the .mu.-axis, of a spectral dispersion of Y signals and C signals obtained by an inter-field YC separation B2, in the three-dimensional frequency space; FIGS. 89(a) to 89(c) are a perspective view, a view from the minus side of the f-axis, and a view from the plus side of the .mu.-axis, of a spectral dispersion of Y signals and C signals obtained by an inter-field YC separation C2, in the three-dimensional frequency space; FIG. 90 is a block diagram showing an embodiment of the present invention; FIG. 91 is a block diagram showing first examples of an intra-frame correlation detecting circuit and an intra-frame Y signal extracting filter shown in FIG. 90; FIG. 92 is a block diagram showing second examples of the intra-frame correlation detecting circuit and the intra-frame Y signal extracting filter shown in FIG. 90; FIG. 93 is a block diagram showing third examples of the intra-frame correlation detecting circuit and the intra-frame Y signal extracting filter shown in FIG. 90; FIG. 94 is a block diagram showing fourth examples of the intra-frame correlation detecting circuit and the intra-frame Y signal extracting filter shown in FIG. 90; FIG. 95 is a block diagram showing fifth examples of the intra-frame correlation detecting circuit and the intra-frame Y signal extracting filter shown in FIG. 90; FIG. 96 is a block diagram showing sixth examples of the intra-frame correlation detecting circuit and the intra-frame Y signal extracting filter shown in FIG. 90; FIG. 97 is a block diagram showing a first example of an intra-field correlation judge circuit shown in FIGS. 91 to 96; FIG. 98 is a block diagram showing first examples of an intra-frame correlation detecting circuit and an intra-frame C signal extracting filter shown in FIG. 90; FIG. 99 is a block diagram showing second examples of the intra-frame correlation detecting circuit and the intra-frame C signal extracting filter shown in FIG. 90; FIG. 100 is a block diagram showing third examples of the intra-frame correlation detecting circuit and the intra-frame C signal extracting filter shown in FIG. 90; FIG. 101 is a block diagram showing fourth examples of the intra-frame correlation detecting circuit and the intra-frame C signal extracting filter shown in FIG. 90; FIG. 102 is a plan view showing an arrangement of the V signal, which is digitized by a frequency four times the color sub-carrier frequency, in the three-dimensional time space by the t-axis and the y-axis; FIG. 103 is a plan view showing an arrangement of the same V signal by the x-axis and the y-axis; FIG. 104 is a plan view showing an arrangement of the same V signal by the x-axis and the y-axis; FIG. 105 is a perspective view showing a spectral dispersion of V signals in the three-dimensional frequency space; FIG. 106 is a diagram showing the spectral dispersion of FIG. 105 viewed from the minus side of the f-axis; FIG. 107 is a diagram showing the spectral dispersion of FIG. 105 viewed from the plus side of the .mu.-axis; FIG. 108 is a diagram showing a Y signal output when a circular zone plate chart moves in a prescribed direction at a prescribed speed; FIG. 109 is a diagram showing a Y signal output when a circular zone plate chart moves in a prescribed direction at a prescribed speed; FIG. 110 is a block diagram showing a YC separating filter adaptive to a movement of an image according to a prior art; FIG. 111 is a block diagram showing a Y signal motion detecting circuit in the YC separating filter shown in FIG. 110; FIG. 112 is a block diagram showing a C signal motion detecting circuit in the YC separating filter shown in FIG. 110; FIG. 113 is a block diagram showing an inter-frame YC separating filter in the YC separating filter shown in FIG. 110; FIG. 114 is a block diagram showing an intra-field YC separating filter in the YC separating filter shown in FIG. 110; FIG. 115 is a block diagram showing another example of the C signal motion detecting circuit in the YC separating filter shown in FIG. 110; FIG. 116 is a block diagram showing a YC separating filter adaptive to a movement of an image according to another prior art; FIG. 117 is a block diagram showing a Y signal motion detecting circuit in the YC separating filter shown in FIG. 116; FIG. 118 is a block diagram showing a C signal motion detecting circuit in the YC separating filter shown in FIG. 116; FIG. 119 is a block diagram showing an inter-frame Y signal extracting filter in the YC separating filter shown in FIG. 116; FIG. 120 is a block diagram showing an intra-field Y signal extracting filter in the YC separating filter shown in FIG. 116; FIG. 121 is a block diagram showing an inter-frame C signal extracting filter in the YC separating filter shown in FIG. 116; and FIG. 122 is a block diagram showing an intra-field signal extracting filter in the YC separating filter shown in FIG. 116. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [Embodiment 1] FIG. 1 is a block diagram showing a YC separating filter adaptive to a movement of an image in accordance with a first embodiment of the present invention. In FIG. 1, the intra-field YC separating circuit 1004 shown in FIG. 110 is replaced by an inter-field correlation detecting circuit 1072, an intra-field correlation detecting circuit 1073, and intra-frame YC separating circuit 1074, and other structures are the same as those shown in FIG. 100, so that only these circuits 1072, 1073, and 1074 will be described. FIG. 2 is a block diagram showing first examples of an inter-field correlation detecting circuit 1072, intra-field correlation detecting circuit 1073 and an intra-frame YC separating circuit 1074 in FIG. 1 in detail. In FIG. 2, V signals 1101 are input to an input terminal 1011. Two-pixel delay circuits 1014, 1017, 1018 and 1019 delay the input signal by a time corresponding to two pixels. A two hundreds and sixty two-line (hereinafter referred to as 262-line) delay circuit 1015 delays the input signal by a time corresponding to 262 lines. A one-line delay circuit 1016 delays the input signal by a time corresponding to one line. Subtracters 1020, 1021, 1022 and 1036 perform subtraction between two input signals. Signal selecting circuits 1023 and 1035 select one of three input signals. Reference numerals 1024, 1025 and 1026 designate low pass filters whose pass band is 2.1 MHz and below. Absolute circuits 1027, 1028 and 1029 output an absolute value of an input signal. A minimum value selecting circuit 1030 detects a minimum value of three input signals and outputs a control signal. An intra-field correlation judge circuit 1031 partially detects a correlation in a field and outputs a control signal. A horizontal direction C signal extracting filter performs an operation in the horizontal direction and extracts C signals. Its characteristic is represented by the following formula, using a transfer function, that is; In addition, a vertical direction C signal extracting filter 1033 performs an operation in the vertical direction and extracts C signals. Its characteristic is represented by the following formula, using a transfer function, that is; In addition, a horizontal and vertical direction C signal extracting filter 1034 performs operations in the horizontal and vertical direction and extracts C signals. Its characteristic is represented by the following formula, using a transfer function, that is; In the above formulae, z.sup.-1 represents a delay of one sample (one pixel) and z.sup.-1 represents a delay of one line. Since the V signal is sampled synchronously with a color sub-carrier wave by a sampling frequency (=4 f.sub.sc : f.sub.sc is a color sub-carrier wave frequency), An output of the subtracter 1036 is output from the output terminal 1012 as an intra-frame YC separated Y signal 1112 and an output of the signal selecting circuit 1035 is output from the output terminal 1013 as an intra-frame YC separated C signal 1113. When an x-axis is taken along the horizontal direction of a screen, a y-axis is taken along the vertical direction of the screen, and a t-axis (time axis) is taken along the direction perpendicular to a plane produced by the x-axis and the y-axis, a three-dimensional time space is constituted by the x, y, and t axes. FIGS. 7 and 8 are diagrams showing the three-dimensional time space. FIG. 7 shows a plane constituted by the t axis and the y axis. FIG. 8 shows a plane constituted by the x axis and the y axis. Interlace scanning lines are shown in FIG. 7, each broken line shows one field and the full line shows that the color sub-carrier has the same phase. In FIG. 8, the full line and the broken line show scanning lines of n field and n-1 field, respectively, and marks (.largecircle.), (.circle-solid.), (.diamond.), and (.diamond-solid.) on the scanning lines are sampling points having the same phase of color sub-carrier in a case where the V signal is digitized by the frequency of four times the color sub-carrier wave frequency f.sub.sc (=3.58 MHz). In FIG. 8, when a particular sampling point is represented by (.star-solid.), sampling points (c) and (d) next but one to the particular sampling point in the same n field and sampling points (a) and (b) in the upper and lower n fields have color sub-carrier phases opposite the phase of the particular sampling point. Therefore, a line comb type filter utilizing a digital circuit or a YC separating filter adaptive to a movement of an image disclosed in Japanese Patent Published Application No. 58-242367 can be constituted. In addition, as shown in FIG. 7, the same sampling points apart by one frame from each other have opposite color sub-carrier phases, so that an inter-frame YC separation filter can also be constituted. Furthermore, as shown in FIG. 8, in the n-1 fields by one field before the particular sampling point, sampling point above the particular sampling point and sampling points and diagonally below the particular sampling point have phases opposite the phase of the particular sampling point, so that an inter-field YC separation is possible by operating one of these sampling points , , and with the particular sampling point. If a .mu.-axis as a horizontal frequency axis, a .nu.-axis as a vertical frequency axis, and a f-axis as a time frequency axis, which correspond to the x, y and t axes, are considered, a three-dimensional frequency space is constituted by the orthogonal .mu., .nu. and f axes. FIGS. 9, 10 and 11 show projections of the three-dimensional frequency space. More specifically, FIG. 9 is a perspective view of the three-dimensional frequency space, FIG. 10 is a view from minus side of the f-axis, and FIG. 11 is a view from plus side of the .mu.-axis. In these figures, spectrum dispersion of V signals on the three-dimensional frequency space is shown. The spectrum of Y signals broadens with the O point of the three-dimensional frequency space as a center. C signals are only present on the second quadrant and the fourth quadrant when the V signals are viewed on the .mu.-axis because the spectrum of the C signals has I signals and Q signals which are subjected to quadrarure two-phase demodulation by the color sub-carrier f.sub.sc. This fact corresponds to that the full line showing the same phase of the color sub-carrier rises with time in FIG. 8. In the aforementioned conventional example, when the movement of image is detected, since the YC separation utilizing the intra-field correlation is performed, band restriction in the f-axis direction is not possible although band restrictions in the .mu.-axis and .nu.-axis directions are possible. Therefore, the band of the Y signal in the moving image is narrow. When the YC separation is performed by the inter-field process as described above, the band of the Y signal in the moving image can be broadened. In FIG. 8, sampling points (.circle-solid.) , , and in the n-1 field and in the vicinity of the particular sampling point (.star-solid.) have color sub-carrier phases opposite the phase of the particular sampling point. The inter-field YC separation is possible by operating one of these sampling points with the particular sampling point. First of all, a high-frequency component on the three-dimensional frequency space including C signals can be taken out by the difference between the particular sampling point (.star-solid.) and the sampling point (.circle-solid.) shown in FIG. 8. This is defined as an inter-field YC separation A. When the high-frequency component passes through one of the horizontal direction C signal extracting filter 1032, the vertical direction C signal extracting filter 1033, and the horizontal and vertical direction C signal extracting filter 1034, C signals are obtained. Second, a high frequency component on the three-dimensional frequency space including C signals can be taken out by the difference between the particular sampling point (.star-solid.) and the sampling point (.circle-solid.) shown in FIG. 8. This is defined as an inter-field YC separation B. When thus obtained high-frequency component passes through one of the horizontal direction C signal extracting filter 1032, the vertical direction C signal extracting filter 1033, and the horizontal and vertical direction C signal extracting filter 1034, C signals are obtained. Third, a high frequency component on the three-dimensional frequency space including C signals can be taken out by the difference between the particular sampling point (.star-solid.) and the sampling point (.circle-solid.) shown in FIG. 8. This is defined as an inter-field YC separation C. When thus obtained high-frequency component passes through one of the horizontal direction C signal extracting filter 1032, the vertical direction C signal extracting filter 1033, and the horizontal and vertical direction C signal extracting filter 1034, C signals are obtained. In order to adaptively control the switching of these inter-field YC separations A, B, and C, it is necessary to detect correlations between the particular sampling point (.star-solid.) and the sampling points (.circle-solid.), and . Since V signals are input to the input terminal 1011, a horizontal low-pass frequency component of the difference between two sampling points having opposite phases in the n field and in the n-1 field is used to detect the correlation. The inter-field correlation detecting circuit, the intra-field correlation detecting circuit and the intra-frame YC separating circuit shown in FIG. 2 operate as follows. In this embodiment, when the image is judged to be a moving image by the motion detecting circuit 1080, an optimum filter among the intra-frame YC separating filters including three kinds of inter-field operations and three kinds of intra-field operations is used instead of the intra-field YC separating filter. In FIG. 2, V signals 1101 input to the input terminal 1011 are delayed by two pixels in the two-pixel delay circuit 1014 and delayed by 262 lines in the 262-line delay circuit 1015. The V signals delayed by two pixels in the two-pixel delay circuit 1014 and the output of the 262-line delay circuit 1015 are subtracted by the subtracter 1020, resulting in an inter-field difference for the inter-field YC separation C. The V signals delayed by two pixels in the two-pixel delay circuit 1014 and the output of the two-pixel delay circuit 1018 are subtracted by the subtracter 1021, resulting in an inter-field difference for the inter-field YC separation B. The V signals delayed by two pixels in the two-pixel delay circuit 1014 and the output of the two-pixel delay circuit 1019 are subtracted by the subtracter 1022, resulting in an inter-field difference for the inter-field YC separation A. These three kinds of inter-field differences are input to the signal selecting circuit 1023 and then selected by an output of a minimum value selecting circuit 1030 which will be described later. The inter-field difference as an output of the subtracter 1020 pass through the LPF 1024, whose pass band is 2.1 MHz and below, and then an absolute value thereof obtained in the absolute value circuit 1027. The absolute value is input to the minimum value selecting circuit 1030, thereby detecting a correlation between the particular sampling point and the sampling point shown in FIG. 8. The inter-field difference as an output of the substrate 1021 pass through the LPF 1025, whose pass band is 2.1 MHz and below, and then an absolute value thereof is obtained in the absolute value circuit 1028. The absolute value is input to the minimum value selecting circuit 1030, thereby detecting a correlation between the particular sampling point and the sampling point shown in FIG. 8. The inter-field difference as an output of the subtracter 1022 pass through the LPF 1026, whose pass band is 2.1 MHz and below, and then an absolute value thereof is obtained in the absolute value circuit 1029. The absolute value is input to the minimum value selecting circuit 1030, thereby detecting a correlation between the particular sampling point and the sampling point shown in FIG. 8. The minimum value selecting circuit 1030 selects the minimum value from the above-described three absolute values (the correlation detecting amount is the maximum) and controls the signal selecting circuit 1023. More specifically, the signal selecting circuit 1023 selects the output of the subtracter 1020 when the output of the absolute value circuit 1027 is the minimum, the output of the subtracter 1021 when the output of the absolute value circuit 1028 is the minimum, and the output of the subtracter 1022 when the output of the absolute value circuit 1029 is the minimum. Furthermore, C signals are extracted from the output of the signal selecting circuit 1023 in any of the horizontal direction C signal extracting filter 1032, the vertical direction C signal extracting filter 1033 and the horizontal and vertical direction C signal extracting filter 1034, by the filter process having the following transfer function. horizontal direction C signal extracting filter vertical direction C signal extracting filter horizontal and vertical direction C signal extracting filter Here, correlations in the horizontal direction and the vertical direction of the image is detected with respect to the particular sampling point, and when the correlation is especially remarkable in the horizontal direction, the output of the horizontal direction C signal extracting filter 1032 is selected. When the correlation is especially remarkable in the vertical direction, vertical direction C signal extracting filter 1033 is selected. The output of the horizontal and vertical direction C signal extracting filter 1034 is selected in other cases. Correlations in the horizontal direction and the vertical direction are detected in the intra-field correlation judge circuit 1031. The intra-field correlation judge circuit 1031 detects existences of correlations in the horizontal direction and the vertical direction of the image by the intra-field process and controls the signal selecting circuit 1035 by the result of the detection. The output from the signal selecting circuit 1035 is output from the output terminal 1013 as intra-frame YC separated C signals 1113. On the other hand, the intra-frame YC separated C signals 1113 are subtracted from the V signals output from the two-pixel delay circuit 1014 by the subtracter 1036, leaving intra-frame YC separated Y signals. In the first embodiment shown in FIG. 2, in a case where the signal selecting circuit 1035 is fixed to select only the output from the horizontal and vertical direction C signal extracting filter 1034, Y signals output from the output terminal 1012, when the inter-field process is adaptively switched, are shown in FIGS. 108 and 109. FIGS. 108 and 109 show circular zone plate charts moving in prescribed directions at a prescribed speed. More specifically, FIG. 108(a) shows a circular zone plate chart moving downward at a speed of one pixel per one field, FIG. 108(b) shows a circular zone plate chart moving leftward at a speed of one pixel per one field, FIG. 109(a) shows a circular zone plate chart moving rightward at a speed of one pixel per one field, and FIG. 109(b) shows a circular zone plate chart moving upward at a speed of one pixel per one field. In the FIGS. 108(b), 109(a), and 109(b), the white regions show absence of Y signals. In the conventional device shown in FIG. 110, when the motion detecting circuit 1080 judges that the image is a moving image, the Y signal mixing circuit 1009 and the C signal mixing circuit 1010 select the output of the intra-field YC separating circuit 1004. Therefore, when the circular zone plate chart moves in any direction, the Y signals output from the output terminal 1002 have a deterioration in resolution in the diagonal direction as shown in FIG. 109(b). On the other hand, in this embodiment of the present invention, by adaptively switching the inter-field processes, no deterioration in resolution occurs as shown in FIG. 108(a) when the image moves in some direction, so that crosstalks of the Y signals and the C signals are reduced. As described above, when the motion detecting circuit detects a moving image, in the intra-frame YC separating filter, correlations between fields are partially detected and a plurality of inter-field processes are adaptively switched in accordance with the result of the detection while correlations in fields are partially detected and a plurality of intra-field processes are switched in accordance with the result of the detection. Therefore, when the moving image is processed by the YC separating filter adaptive to the movement, an optimum YC separation is possible using the correlation of the image, resulting in a YC separating filter adaptive to a movement of an image, which performs YC separation with less deterioration in resolution. In addition, according to the first embodiment of the present invention, inter-field correlations in plural directions are partially detected by the horizontal low-frequency component of the difference between two sampling points whose color sub-carrier phases are opposite from each other between fields. Therefore, the direction to which the image moves is detected, so that an operation between fields appropriate for the direction is possible. A description will now be given of a circuit that judges which C signal output is to be selected from the C signal outputs extracted by the horizontal direction C signal extracting filter 1032, the vertical direction C signal extracting filter 1033 and the horizontal and vertical C signal extracting filter 1034. FIG. 6 is a block diagram showing the intra-field correlation judge circuit 1031 of FIG. 2 in detail. In FIG. 6, V signals are applied to the input terminal 1053. Reference numeral 1055 designates a vertical direction low-pass filter through which low-frequency components in the vertical direction pass. Reference numeral 1056 designates a vertical direction band-pass filter, 1057 a vertical direction low-pass filter, 1058 a horizontal direction band-pass filter, 1059 a horizontal direction high-pass filter, and 1060 a horizontal direction low-pass filter. Reference numerals 1061, 1062, 1063, and 1064 designate absolute value circuits. Reference numerals 1065, 1066, 1067, and 1068 designate comparators which compare an input signal with a constant and output a control signal. Reference numerals 1069 and 1070 designate a vertical correlation detecting circuit and a horizontal correlation detecting circuit, respectively, and a judge circuit 1071 sends a control signal to the signal selecting circuit 1035 in accordance with the result of the detection. A control signal in accordance with the detected correlation is output from an output terminal 1054. The operation of FIG. 6 will now be described. In FIG. 6, a frequency component, which is a low-frequency component in the vertical direction at a particular sampling point and corresponds to a half of color sub-carrier frequency in the horizontal direction, is extracted by the vertical direction low-pass filter 1055 and the horizontal direction high-pass filter 1059 and then its absolute value is obtained by the absolute value circuit 1061, whereby a horizontal direction high-frequency Y signal energy is obtained. In addition, a d.c. component in the vertical direction at the particular sampling point and a frequency component corresponding to the color sub-carrier component are removed by the vertical direction band-pass filter 1056 and then its absolute value is obtained by the absolute value circuit 1062, whereby a vertical direction non-correlation energy is obtained. Furthermore, a frequency component, which is a low-frequency component in the horizontal direction at the particular sampling point and corresponds to a half of color sub-carrier frequency in the vertical direction, is extracted by the vertical direction high-pass filter 1057 and the horizontal direction low-pass filter 1060 and then its absolute value is obtained by the absolute value circuit 1063, whereby a vertical direction high-frequency Y signal energy is detected. In addition, a d.c. component in the horizontal direction at the particular sampling point and a frequency component corresponding to the color sub-carrier component are removed by the horizontal direction band-pass filter 1058 and then the remaining signals absolute value is obtained by the absolute value circuit 1064, whereby a horizontal direction non-correlation energy is detected. The vertical direction low-pass filter 1055 is represented by the following formula, that is; and the horizontal direction high-pass filter 1059 is represented by the following formula, that is; That is, the frequency component corresponding to a half of the color sub-carrier is extracted in the horizontal direction. The horizontal direction band-pass filter 1058 is represented by the following formula, that is; and the vertical direction high-pass filter 1057 is represented by the following formula, that is; That is, the frequency component corresponding to a half of the color sub-carrier is extracted in the vertical direction. The horizontal direction low-pass filter 1060 is represented by the following formula, that is; and the vertical direction band-pass filter 1056 is a digital filter represented by the following formula, that is; The vertical direction non-correlation energy Dv(z) and the horizontal direction non-correlation energy Dh(z) are represented by the following formulae by introducing absolute value approximation and using transfer function, that is; The Dv(z) and Dh(z) show filter characteristics that prevent the passage of the d.c. component and the color sub-carrier frequency component with respect to the vertical direction and the horizontal direction. The Dv(z) is obtained by the vertical direction band-pass filter 1056 and the absolute value circuit 1062 and the Dh(z) is obtained by the horizontal direction band-pass filter 1058 and the absolute value circuit 1064. In addition, the horizontal direction high-frequency Y energy DYh(z) and the vertical direction high-frequency Y energy DYv(z) are represented by the following formulae by introducing absolute value approximation and using a transfer function, that is; The DYh(z) is obtained by the vertical direction low-pass filter 1055, the horizontal direction high-pass filter 1059, and the absolute value circuit 1061 and the DYv(z) is obtained by the vertical direction high-pass filter 1057 and the horizontal direction low-pass filter 1060 and the absolute value circuit 1063. An output of the absolute value 1061 is input to the comparator 1065, an output of the absolute value circuit 1062 is input to the comparator 1066, an output of the absolute value circuit 1063 is input to the comparator 1067, and an output of the absolute value circuit 1064 is input to the comparator 1068. The comparator 1065 compares the input signal with a constant (Kdy.sub.1 described later) and sends a control signal to the vertical correlation detecting circuit 1069 in accordance with the result of the comparison. The comparator 1066 compares the input signal with a constant (Kd.sub.1 described later) and sends a control signal to the vertical correlation detecting circuit 1069 in accordance with the result of the comparison. The comparator 1067 compares the input signal with a constant (Kdy.sub.2 described later) and sends a control signal to the horizontal correlation detecting circuit 1070 in accordance with the result of the comparison. The comparator 1068 compares the input signal with a constant (Kd.sub.2 described later) and sends a control signal to the horizontal correlation detecting circuit 1070 in accordance with the result of the comparison. Then, the vertical correlation detecting circuit 1069 detects a correlation in the vertical direction when Dv(z) .ltoreq.Kd.sub.1 (Kd.sub.1 . . . correlation threshold coefficient) and DYh(z) .gtoreq.Kdy.sub.1 (Kdy.sub.1 . . . high-frequency signal energy threshold constant) and sends a control signal to the judge circuit 1071 in accordance with the result of the detection. In addition, it detects no correlation in the vertical direction when Dr(z)>Kd.sub.1 or DYh(z)<Kdy.sub.1 and sends a control signal to the judge circuit 1071 in accordance with the result of the detection. On the other hand, the horizontal correlation detecting circuit 1070 detects a correlation in the horizontal direction when Dh(z).ltoreq.Kd.sub.2 (Kd.sub.2 . . . correlation threshold coefficient) and DYv(z).gtoreq.Kdy.sub.2 (Kdy.sub.2 . . . high-frequency signal energy threshold constant) and sends a control signal to the judge circuit 1071 in accordance with the result of the detection. In addition, it detects no correlation in the horizontal direction when Dh(z)>Kd.sub.2 or DYh(z)<Kdy.sub.2 and sends a control signal to the judge circuit 1071 in accordance with the result of the detection. When the result of the vertical correlation detecting circuit 1069 is "correlation is present" and the result of the horizontal correlation detecting circuit 1070 is "correlation is absent", the judge circuit 1071 outputs a control signal so that the signal selecting circuit 1035 shown in FIG. 2 may select the output of the vertical direction C signal extracting filter 1033. When the result of the vertical correlation detecting circuit 1069 is "no correlation is present" and the result of the horizontal correlation detecting circuit 1070 is "correlation is present", the judge circuit 1071 outputs a control signal so that the signal selecting circuit 1035 may select the output of the horizontal direction C signal extracting filter 1032. When the result of the vertical correlation detecting circuit 1069 is "correlation is absent" and the result of the horizontal correlation detecting circuit 1070 is "correlation is absent" or when the result of the vertical correlation detecting circuit 1069 is "correlation is present" and the result of the horizontal correlation detecting circuit 1070 is "correlation is present", the judge circuit 1071 outputs a control signal so that the signal selecting circuit 1035 may select the output of the horizontal and vertical direction C signal extracting filter 1034. The output of the judge circuit 1071 is output from the output terminal 1045, whereby the correlation detection results in the horizontal direction and the vertical direction are output. According to the above-described first embodiment, since the detection of correlation is performed also in the field, a filter according to the image is selected in the field utilizing the correlation of the image. [Embodiment 2] FIG. 3 is a block diagram showing a second embodiment of the inter-field correlation detecting circuit 1072, the intra-field correlation detecting circuit 1073, and the intra-frame YC separating circuit 1074 shown in FIG. 1. In FIG. 3, the same reference numerals as those in FIG. 2 designate the same or corresponding parts. Reference numerals 1037 and 1038 designate adders and reference numeral 1039 designates a subtracter. Reference numerals 1040 and 1041 designate band-pass filters whose pass band is 2.1 MHz and above. Reference numerals 1042 designates a low-pass filter whose pass band is 2.1 MHz and below. Reference numerals 1043, 1044, and 1045 designate absolute value circuits. Reference numeral 1046 designates a maximum value selecting circuit which selects the maximum value of three input signals and outputs a control signal. This second embodiment is different from the first embodiment of FIG. 2 only in the method for detecting a correlation between field. In this second embodiment, in order to detect the correlation of V signals, a method of detecting a direction in which spectrum of Y signals broadens in the three-dimensional frequency space. Here, inter-field correlation is detected utilizing horizontal low-frequency component of a difference between two sampling points having the same phases of the color sub-carrier between the n field and the n-1 field and horizontal high-frequency component of a sum of two sampling points having opposite phases of the color sub-carrier wave between the n field and the n-1 field. A description is given of the inter-field correlation detecting circuit of FIG. 3, which is different from that of FIG. 2. In FIG. 3, in order to select the inter-field YC separation A, a difference between the particular sampling point (.star-solid.) shown in FIG. 8 and the sampling point (.largecircle.) I, beneath the sampling point (.circle-solid.) by one line passes through the LPF, thereby detecting the correlation. In order to select the inter-field YC separation B, a sum of the particular sampling point (.star-solid.) and the sampling point (.circle-solid.) passes through the BPF, thereby detecting the correlation. In order to select the inter-field YC separation C, a sum of the particular sampling point (star) and the sampling point (.circle-solid.) passes through the BPF, thereby detecting the correlation. The operation will be described hereinafter. An output of the 262-line delay circuit 1015 and an output of the two-pixel delay circuit 1014 are added by the adder 1037, the result passes through the BPF 1040 whose pass band is 2.1 MHz and above, its absolute value is obtained in the absolute value circuit 1043, the absolute value is input to the maximum value selecting circuit 1046, and the correlation between the particular sampling point and the sampling point shown in FIG. 8 is detected. The output of the 262-line delay circuit 1015 is delayed by four pixels by the two-pixel delay circuits 1017 and 1018. The output of the two-pixel delay circuit 1018 and the output of the two-pixel delay circuit 1014 are added by the adder 1038, the result passes through the BPF 1041 whose pass band is 2.1 MHz and above, its absolute value is obtained in the absolute value circuit 1044, the absolute value is input to the maximum value selecting circuit 1046 and the correlation between the particular sampling point and the sampling point shown in FIG. 8 is detected. The output of the two-pixel delay circuit 1017 and the output of the two-pixel delay circuit 1014 are subtracted by the subtracter 1039, the result passes through the LPF 1042 whose pass band is 2.1 MHz and below, its absolute value is obtained in the absolute value circuit 1045, the absolute value is input to the maximum value selecting circuit 1046, and the correlation between the particular sampling point and the sampling point shown in FIG. 8 is detected. The maximum value selecting circuit 1046 selects the maximum value (the correlation detecting amount is the maximum) from the above-described three absolute values and controls the signal selecting circuit 1023. More particularly, the signal selecting circuit 1023 |