JP5003521B2 - Update region detection device with motion compensation - Google Patents

Description

  The present invention relates to an update area detection apparatus, and more particularly to an update area detection apparatus that detects an update area associated with motion compensation from frames before and after drawing data on a computer screen.

  In recent years, all applications that are input / output and displayed on a terminal device are executed on a server device for the purpose of preventing leakage of information from the terminal device of the computer and facilitating application management on the terminal side. In addition, a thin client system has been introduced in which all generated files accompanying this are managed by the server device.

  In such a thin client system, drawing data of an application program executed on a server device is transferred to a terminal device on the client side through a network such as a LAN and displayed on the screen of the terminal device. For this reason, when the processing amount of drawing data increases or the number of terminal devices connected to the server device increases, the load on the server device for transferring drawing data to the terminal device increases, and the response time decreases. Problems such as significant restrictions on the number of connected terminal devices occur.

  Therefore, as a display control technique for drawing data by software, only a rectangular drawing area including a drawing data portion updated in one screen is cut out, and further compressed and transferred as necessary, so that the computer screen It is considered to reduce the load of the server device by reducing the amount of data accompanying the transfer of the drawing data (see, for example, Patent Document 1). However, since the amount of drawing processing on computer screens is increasing due to the high definition of drawing data and the dramatic improvement in monitor resolution, further reduction in processing load is required without reducing drawing quality. .

JP-T-2004-503862 JP 2004-129099 A

  In a moving picture coding system such as MPEG, the amount of transmission code is reduced by performing motion compensation using a movement vector indicating which position of a reference picture is similar to a pixel block to be coded. A technique called a full search method is generally used to detect a movement vector and a movement area. In the full search method, a comparison is made between a template block as an image to be searched and all search windows as search targets. That is, the movement vector and the movement area are detected in units of blocks of 8 pixels × 8 pixels. In the comparison, the difference absolute value sum of the pixel values is obtained in order while scanning the search window, and a motion with a place where the difference absolute value is minimized is detected as a movement vector. However, the full search method requires a very large amount of computation. For this reason, a high-speed method is proposed in which a rough search is first performed broadly, and a narrow search is performed according to the evaluation result with high accuracy (see, for example, Patent Document 2).

  Even in the transfer of drawing data on a computer screen from a server device to a terminal device in a thin client system, a significant reduction in the amount of transferred data can be expected by detecting the movement of an object such as a window and performing motion compensation. However, the distance that an object such as a window moves within the time of one frame may reach 100 or more in terms of the number of pixels, but many are expected to be several to several tens of pixels. Therefore, large windows generally overlap before and after movement. For this reason, when the update area is extracted by comparing the previous frame and the current frame that have undergone motion compensation, if the rectangle that includes all the update locations existing on the screen is extracted as the update area, the update area is excessive. As a result, the amount of code increases.

  An object of the present invention is to provide an update region detection apparatus capable of detecting an update region after motion compensation with high accuracy.

The update region detection apparatus of the present invention detects a moving region detection that detects, as a moving region, an image region that is the same or similar image region that exists in both the previous frame and the current frame, and whose position on the screen changes. Means,
Motion compensation means for copying the movement area detected by the movement area detection means to a position after movement on the previous frame;
Update area detection area setting means for setting an update area detection area;
For each update area detection area set by the update area detection area setting means, an update area detection means for detecting an area where the previous frame after the copy is different from the current frame as an update area, and
The update area detection area setting means includes a movement direction determination means for determining the movement direction of the movement area detected by the movement area detection means, and the movement direction determined by the movement direction determination means from the top to the bottom of the screen. When the moving direction is included, the screen is divided by the upper end of the moving area after moving, and when the moving direction determined by the moving direction determining means includes the component moving upward from the bottom of the screen, the moving area after moving Dividing means for dividing the screen by the lower end of each and setting each divided area as an update area detection area.

  ADVANTAGE OF THE INVENTION According to this invention, the update area | region detection apparatus which can detect the update area | region after motion compensation with high precision is obtained. Further, since the number of divisions is determined in consideration of the moving direction of the movement area, the number of divisions can be reduced.

  Referring to FIG. 1, an example of a video signal encoding device 100 according to an embodiment of the present invention includes an image input device 101, a data storage device 102, a data processing device 103, and a code output device 104. ing.

  The image input device 101 is a device that inputs a video signal to be encoded. For example, a color video signal on a display screen of a computer (not shown) is analog captured or digital captured and stored in the data storage device 102. The captured video signal for one screen is called a frame or screen data.

  The data storage device 102 stores an encoding target frame storage unit 111 that stores a frame input from the image input device 101, and a reference frame that stores a reference frame used for encoding the frame stored in the encoding target frame storage unit 111. The storage unit 112 includes a work area 113 that holds various data that are appropriately referenced and updated in the process of frame encoding.

  The data processing device 103 is a device that encodes the encoding target frame stored in the data storage device 102, and includes a movement vector detection unit 121, a movement region detection unit 122, a motion compensation unit 123, and an update region detection region setting unit. 124, an update region detection unit 125, and a region encoding unit 126. Each means generally has the following functions.

  The movement vector detection unit 121 has a function of detecting one main movement vector by comparing the encoding target frame with the immediately preceding frame. In other words, the main movement vector means a dominant one of one or more movement vectors. For example, when a map scroll and a mouse cursor move simultaneously on the computer screen, the map scroll occupies most of the movement vector, so the movement vector by the map scroll becomes the main movement vector.

  The movement area detection unit 122 is the same or similar image area that exists in both the encoding target frame and the immediately preceding frame, and the movement vector detected by the movement vector detection unit 121 is the position on the screen. It has a function of detecting an image area that changes only as a moving area.

  The motion compensation unit 123 copies the movement region detected by the movement region detection unit 122 to the movement destination indicated by the movement vector in the reference frame used for encoding the encoding target frame, and the reference frame after the motion compensation is performed. It has the function to generate.

  The update area detection area setting means 124 has a function of setting one or more update area detection areas on the frame.

  The update region detection unit 125 has a function of detecting, as an update region, a region where the reference frame after motion compensation is different from the encoding target frame for each update region detection region set by the update region detection region setting unit 124. .

  The region encoding unit 126 generates a code encoded by an arbitrary encoding method using the update region detected by the update region detection unit 125 as an image.

  The code output device 104 is a device that reads and outputs the code generated for the encoding target frame from the work area 113 of the data storage device 102, and is configured by a communication device that communicates with a client terminal (not shown), for example. The code generated for one encoding target frame includes the update region code generated by the region encoding unit 126, the movement region information detected by the movement vector detection unit 121 and the movement region detection unit 122 (the movement source information). Area coordinates and movement vectors).

  The movement vector detection means 121, the movement area detection means 122, the motion compensation means 123, the update area detection area setting means 124, the update area detection means 125, and the area encoding means 126 are the computer constituting the data processing device 103 and its It can be realized with the program that operates above. The program is provided by being recorded on a computer-readable recording medium such as a CD-ROM, and read by the computer when the computer is started up, etc., and controls the operation of the computer, thereby realizing each of the above means on the computer. .

  Next, the overall operation of video signal encoding apparatus 100 according to the present embodiment will be described.

  The image input device 101 of the video signal encoding device 100 captures a frame to be encoded and stores it as a current frame in the encoding target frame storage unit 111 of the data storage device 102 (step S101 in FIG. 2).

  Next, the movement vector detection means 121 compares the current frame with the frame (reference frame) immediately before encoding, which has been stored in the reference frame storage unit 112, and detects one main movement vector. (Step S102). For example, if the movement vector 134 illustrated from the comparison between the current frame 131 and the reference frame 132 in FIG. 3 is dominant, the movement vector 134 is detected as the main movement vector. Information on the detected movement vector 134 is temporarily stored in the work area 113.

  Next, when a movement vector is detected from the current frame (YES in step S103), the movement area detection unit 122 is the same or similar image area that exists in both the current frame and the reference frame, The image area where the position at is changed by the movement vector detected by the movement vector detecting means 121 is detected as a movement area (step S104). For example, in the current frame 131 and the reference frame 132 in FIG. 3, when the area 135 and the area 136 are the same or similar image areas, the areas 135 and 136 are detected as moving areas. The detected coordinate information of the moving areas 135 and 136 is temporarily stored in the work area 113.

  Next, when a movement area is detected (YES in step S105), the motion compensation unit 123 performs motion compensation for copying the image of the movement area before movement on the reference frame to the position after movement indicated by the movement vector. Thus, the reference frame storage unit 112 is updated (step S106). For example, in the case of FIG. 3, the area 136 is copied to a position corresponding to the area 135 in the current frame 131 on the reference frame 132. Thereby, the reference frame 137 after motion compensation in FIG. 3 is generated.

  However, when the movement vector is not detected (NO in step S103), the detection of the movement area and the motion compensation are not executed. Further, even if the movement vector is detected, if the detection of the movement area fails (NO in step S105), motion compensation is not executed.

  Next, the update area detection area setting means 124 sets one or more update area detection areas for detecting the update area on the frame (step S107). Next, the update area detection unit 125 detects, as an update area, an area where the reference frame is different from the current frame for each update area detection area set by the update area detection area setting unit 124 (step S108). Thereby, for example, in the case of FIG. 3, the update areas 138 and 139 are detected. The detected coordinate information of the update areas 138 and 139 is temporarily stored in the work area 113.

  Next, the region encoding unit 126 generates a code obtained by encoding the update region detected by the update region detection unit 125 as an image (step S109). The generated code is temporarily stored in association with the coordinate information of the update area stored in the work area 113.

  The code output device 104 receives the information generated for the current frame from the work area 113 of the data storage device 102, that is, the coordinate information of each update area and its code and movement area information (coordinate information and movement vector of the movement source area). Read and output (step S110). For example, in the case of FIG. 3, the coordinate information and code of the update area 138, the coordinate information and code of the update area 139, the coordinate information of the movement area 136, and the movement vector 134 are output as code information regarding the current frame.

  When decoding a frame from code information, it is performed in the reverse order of encoding. For example, when the current frame 131 in FIG. 3 is decoded from the reference frame 132 and the code information, first, the movement region 136 of the reference frame 132 is copied to the location indicated by the movement vector 134 to generate a reference frame 137 after motion compensation. The current frame 131 is generated by reflecting the update area 138 and the update area 139 decoded from the code information with respect to the reference frame.

  Next, each unit included in the data processing apparatus 103 will be described. Here, the motion compensation unit 123 can be realized by a copy unit, and the region encoding unit 126 can be realized by a known image encoding technique such as predictive encoding, transform encoding, vector quantization, entropy encoding, and so on. Now, the movement vector detection means 121, the movement area detection means 122, the update area detection area setting means 124, and the update area detection means 125 will be described in detail.

(1) Movement vector detection means 121
Referring to FIG. 4A, the first example of the movement vector detection unit 121 includes an edge extraction unit 201, a feature point extraction unit 202, a feature point pair extraction unit 203, and a movement vector calculation unit 204. Each has the following functions in general.

  The edge extracting unit 201 has a function of extracting a point having a large change in pixel value as an edge point in the current frame and the reference frame. Edge points are two predetermined orthogonal directions (up and left, left and bottom, bottom and right, right and top, diagonal top left and diagonal bottom left, diagonal bottom left and diagonal bottom right, diagonal bottom right and diagonal top right, The pixel values are different from each other by a predetermined threshold or more in the difference between the pixel values of the diagonally upper right and diagonally upper left adjacent pixels. For example, the difference between the pixel values is obtained for each of R, G, and B components, and if the difference between any of the components is equal to or greater than the threshold, it is determined that the difference between the pixel values of the two pixels is equal to or greater than the threshold. .

  The feature point extraction means 202 is an edge point whose position relationship with one or more other edge points is unique (also referred to as unique) among the edge points extracted from the current frame and the reference frame (that is, other points). And a function of extracting, as a feature point, an edge point whose positional relationship with one or more edge points appears only once in the frame. In this embodiment, one edge point that appears immediately before in the raster scan order of the frame is used as the other one or more edge points. However, as another embodiment, a plurality of edge points such as the immediately preceding first edge point and the immediately preceding second edge point may be used. In general, using a plurality of immediately preceding edge points can reduce the number of edge points having a unique positional relationship with other edge points in the frame, rather than using only one immediately preceding edge point. There is an advantage that the number of bits of the hash value can be reduced when using the hash value.

  As data defining the positional relationship between the edge point and other edge points, a value expressing the distance between the edge points by the number of pixels can be used. Further, not the distance itself but the number of lower bits of the bit string representing the distance may be used as a hash value, and an edge point having this unique hash value may be extracted as a feature point. In the present embodiment, for example, the lower 11 bits of the bit string representing the distance are used as the hash value.

  The feature point pair extracting unit 203 has a function of extracting a pair of feature points having the same positional relationship with other edge points from the current frame and the reference frame. Preferably, the feature point pair extraction unit 203 extracts a pair of feature points having the same positional relationship with other edge points and having a pixel value difference equal to or less than a threshold value.

  The movement vector calculation unit 204 has a function of calculating a difference between coordinate values of feature point pairs extracted from the current frame and the reference frame as a movement vector. Preferably, the movement vector calculation unit 204 includes a movement vector candidate generation unit 205 and a movement vector selection unit 206.

  The movement vector candidate generation unit 205 has a function of generating a difference between coordinate values as a movement vector candidate for each feature point pair when there are a plurality of pairs of feature points extracted from the current frame and the reference frame.

  The movement vector selection means 206 has a function of selecting a movement vector candidate that appears most frequently among the movement vector candidates as a movement vector.

  Next, the operation of the movement vector detection means 121 of this embodiment will be described.

  The edge extraction unit 201 of the movement vector detection unit 121 focuses on the first pixel of the current frame stored in the encoding target frame storage unit 111 (step S201 in FIG. 4B), and determines whether the pixel of interest is an edge point. It is determined whether or not (step S202). If it is not an edge point, attention is shifted to the next pixel in the order of the raster scan direction (step S206), and it is determined whether the pixel being noticed is an edge point (step S202).

  If the pixel of interest is an edge point (YES in step S202), the set of the coordinate value and pixel value of the pixel of interest is temporarily stored in the work area 113 as edge point information (step S203). Next, the distance to the immediately preceding edge point stored in the work area 113 is obtained, and the lower 11 bits of the distance are calculated as a hash value (step S204), corresponding to the current frame stored in the work area 113. The hash table to be updated is updated (step S205). For example, as illustrated in FIG. 4C, when the processing is performed in the raster scan order and the pixel P (5, 1) is detected as the edge point following the pixel P (1, 1), the pixel P (5, 1) Since the distance between the pixel P (1, 1) is 4 in terms of the number of pixels, a hash value of 4 is calculated, and information on the edge point is registered in the hash table.

  Referring to FIG. 4-4, an example of the hash table corresponding to the current frame has an entry corresponding to each hash value of 0 to 2047 in a one-to-one correspondence, and each entry has an appearance frequency, a final appearance coordinate, and a pixel. A value is registered. The initial value of the appearance frequency is 0, and the initial values of the final appearance coordinates and the pixel value are NULL. In the update process of the hash table in step S205, the edge extracting unit 201 increments the appearance frequency of the entry having the calculated hash value by 1, and the coordinate value and pixel value of the detected edge point are set to the final appearance coordinate and pixel value. Record in the column. For example, in the case of the pixel P (5, 1) described above, the appearance frequency in the entry of the hash value 4 in FIG. 4-4 is incremented by 1, and the coordinate value and the pixel value of the pixel P (5, 1) are the same entry. To be recorded.

  The edge extraction unit 201 repeatedly executes the above processing up to the last pixel of the current frame.

  When the processing of the edge extraction unit 201 is completed (YES in step S207), the feature point extraction unit 202 refers to the hash table corresponding to the current frame and sets the coordinate value and the pixel value to the entry whose appearance frequency is 1. Are extracted as feature points (step S208). For example, when the hash table corresponding to the current frame at the time when the processing by the edge extracting unit 201 is completed is the one shown in FIG. 4-4, the pixel P (5, 1) is extracted as one feature point.

  Next, the feature point pair extraction unit 203 refers to the hash table corresponding to the current frame and the hash table corresponding to the previous frame, and extracts all feature point pairs having the same hash value (step S209). Here, the hash table corresponding to the previous frame is created by the edge extraction unit 201 when the previous frame is processed as the current frame, and is stored in the work area 113. For example, when the hash table corresponding to the previous frame has contents as shown in FIG. 4-5, the pixel P (5,1) extracted as a feature point from the current frame shown in FIG. 4-4 and the hash value Since four pixels P (5, 8) having the same value exist in the previous frame, a pair of the pixel P (5, 8) in the previous frame and the pixel P (5, 1) in the current frame is a pair of feature points. Extracted as

  Next, the feature point pair extraction unit 203 has a high possibility of correspondence among pairs of feature points extracted in step S209, in which the difference between the R, G, and B color components is less than or equal to a preset threshold value. Therefore, the remaining feature point pairs are excluded (step S210). The feature point pair extraction unit 203 records the remaining feature point pair information in the work area 113.

  Next, the movement vector candidate generation means 205 of the movement vector calculation means 204 reads out feature point pair information from the work area 113 and generates a coordinate value difference as a movement vector candidate for each pair (step S211). For example, in the case of the above-described pair of feature points P (5, 8) and P (5, 1), (0, -7) is generated as a motion vector candidate. Since still vectors are ignored, they are excluded from candidates when the difference is (0, 0). The movement vector candidate generation unit 205 records information on movement vector candidates in the work area 113.

  Next, the movement vector selection means 206 reads out information on the movement vector candidates from the work area 113, counts the total number of the same movement vector candidates, obtains the appearance frequency of each movement vector candidate, and determines the most frequently used movement vector candidate. It selects as an estimated value of the main movement vector (step S212). Then, the movement vector selection unit 206 records the detection result of the movement vector in the work area 113 (step S213).

  An example of the detection result recorded in the work area 113 by the movement vector selection unit 206 is shown in FIG. In this example, in addition to the estimated movement vector, a list of feature point pairs from which the most frequent movement vector candidates are calculated is included in the detection result. FIG. 4-7 shows a relationship between an image obtained by plotting a pair of feature points included in the detection result in the previous frame and the current frame, and the estimated movement vector. As described above, the motion vector estimated from the most frequent motion vector candidate is the main motion vector among one or more motion vectors existing in the current frame.

  Thus, according to the movement vector detection means 121 of the present embodiment, it is possible to detect main movement vectors at high speed and with high accuracy from the video signal of the computer screen. The reason is that, firstly, it is not necessary to search various vectors in each pixel block, and the movement vector is obtained by extracting and comparing edge points and feature points, and secondly, the raster scan order in the frame. Because of this processing, the locality of memory access is high, and thirdly, since a comparison is made not on a block basis but on the entire screen, a movement vector in a relatively large object unit such as a window can be detected as a main movement vector. Fourthly, since the vector is detected based on the edge point, it is not necessary to accurately match the pixel value between the movement source and the movement destination, and it is possible to deal with a noisy video signal captured in analog. .

  On the other hand, the movement vector detection means 121 of this embodiment (1) does not detect a plurality of vectors at the same time, (2) does not detect a movement vector of an object accompanied by sub-pixel units or deformation, and (3) Although there is a restriction that motion vectors are not detected, (1) and (2) are unlikely to occur on a computer screen, and areas such as (3) are large because the amount of code is small even if they are encoded as images. It doesn't matter.

(2) Moving region detecting means 122
Referring to FIG. 5A, the first example of the moving area detecting unit 122 includes an initial candidate determining unit 301 and a moving area determining unit 302. Each has the following functions in general.

  The initial candidate determination unit 301 has a function of determining an initial candidate for a moving area.

  The moving region determining unit 302 is configured to move the motion compensation unit 123 from among the initial moving region candidate determined by the initial candidate determining unit 301 and one or more other moving region candidates whose sizes are changed. It has a function of determining a moving area to be used for compensation.

  Next, the operation of the moving area detecting means 122 of this embodiment will be described.

  The initial candidate determining means 301 of the moving area detecting means 122 determines the moving area of the initial candidate (step S301 in FIG. 5-2). As an example of a method for determining an initial candidate, there is a method in which a rectangle circumscribing a feature point group that is a calculation source of the movement vector candidate used by the movement vector detecting unit 121 for estimating the movement vector is used as an initial candidate for the movement region. . For example, when the movement vector selection means 206 of the movement vector detection means 121 generates a detection result as shown in FIG. 4-6, the movement area detection means 122 reads the feature points described in the detection result from the work area 113. For each of the previous frame and the current frame, for example, a rectangle circumscribing the feature point group as shown in the previous frame in FIG. 5-3 is set as a movement area before the movement, and the feature points as shown in the current frame in FIG. A rectangle circumscribing the group is detected as a movement area after movement. Information on the detected moving area of the initial candidate is temporarily recorded in the work area 113.

  As another example of the method of determining the initial candidate, a rectangle circumscribing any three or more feature points in the feature point group included in the motion vector candidate used by the motion vector detection unit 121 for estimating the motion vector is used. There are a method for setting an initial candidate for a moving region, a method for setting an entire frame as an initial candidate for a moving region, and the like.

  Next, the moving area determining means 302 of the moving area detecting means 122 determines a moving area to be used for motion compensation from among the initial candidates and other candidates (step S302). Hereinafter, a configuration example of the movement area determination unit 302 will be described in detail.

(A) Example 1 of moving area determination means 302
A processing example of the movement area determination means 302 of Example 1 is shown in FIG. First, the moving area determination unit 302 performs motion compensation based on the determined moving area and moving vector of the initial candidate, compares the pixel values, and confirms whether or not the movement is correctly performed. Specifically, whether the code amount reduced by motion compensation or the code amount increased by motion compensation increases depends on whether the moving region is suitable as a moving region used for motion compensation or not. Using the merit values and demerit values shown as evaluation scales, estimation is performed by the following method (steps S311 and S312). Here, the merit value is an evaluation scale indicating the degree to which the moving area is suitable as a moving area used for motion compensation, and the demerit value is an evaluation scale indicating the degree to which the moving area is not suitable as a moving area used for motion compensation. In any case, the initial value is 0.

(A) When the “pixel value after motion compensation” and the “true pixel value” are different (for example, when any of the differences for each of R, G, and B components is different from a preset threshold value), the motion Assuming that there is a possibility that the amount of code will increase due to compensation, the demerit value is increased by one.
(A) When the “pixel value after motion compensation” does not differ from the “true pixel value” (for example, when any of the differences for each of R, G, and B components does not differ by a predetermined threshold value or more) And there is a luminance gradient greater than or equal to the threshold between the pixel at that coordinate and the adjacent pixel (for example, if the total difference between the upper pixel and the left pixel is greater than or equal to the threshold, When the difference from the left pixel is equal to or greater than a threshold value), the merit value is increased by 1 considering that there is a possibility that the code amount can be reduced by motion compensation. Here, the reason for adding the condition that there is a luminance gradient equal to or greater than the threshold value between adjacent pixels is that a portion including a point having a luminance gradient generally increases the amount of code in encoding by difference. .
(C) The above-mentioned processes (a) and (b) are performed on the entire moving area of the initial candidate, and if the merit value is larger than the demerit value, it is adopted as the moving area, otherwise it is rejected.
The process of adding the merit value and the demerit value according to the comparison result of the pixel value and comparing the final merit value and the demerit value is the addition using only one of the merit value and the demerit value. It is equivalent to using subtraction properly. Specifically, every time a pixel whose difference between the pixel value after motion compensation and the true pixel value is equal to or greater than a predetermined threshold is detected, the merit value is subtracted by the predetermined value (or the demerit value is added by the predetermined value). And a merit value every time a pixel having a difference between a pixel value after motion compensation and a true pixel value that is smaller than a predetermined threshold and having a luminance gradient greater than or equal to the threshold between adjacent pixels is detected. May be added by a predetermined value (or a demerit value is subtracted by a predetermined value) to determine whether the final merit value (or demerit value) is positive or negative.

  If the initial candidate for the moving area is rejected, the detection of the moving area is no longer performed in this example, and the detection result indicating that the detection of the moving area has failed is recorded in the work area 113 (step S323). The process of -4 ends.

  On the other hand, when the initial candidate for the moving area is adopted, it is checked whether the area can be further expanded vertically and horizontally by the following procedure.

(I) For each line of the moving area, check the number of consecutive pixels where the “pixel value after motion compensation” and the “true pixel value” match when the area is expanded to the right (the difference is below the threshold). The right end is determined by setting the minimum value of the number of continuous pixels as the maximum enlargement width to the right (step S313). For example, as shown in FIG. 5-5, when the right edge of the initial candidate is expanded to the right, the first line and the third line are 3 consecutive pixels, and the remaining lines are 2 consecutive pixels, respectively. If the “subsequent pixel value” and the “true pixel value” match, the maximum rightward expansion width is set to two pixels, which is the minimum value of the number of consecutive pixels.

(II) The maximum enlargement width to the left of the moving region is calculated by the same method as the enlargement method to the right, and the left end is determined (step S314).

(III) The area is further expanded upward by one line with respect to the moving area after performing the processes (I) and (II) (steps S315 to S318). Specifically, the merit value and demerit value when one line is enlarged are calculated in the same manner as in the above (a) and (b) (steps S315 and S316), and if the merit value is larger than the demerit value ( YES in step S317), the process returns to step S315, and the same processing is performed for the next line. If the merit value is not larger than the demerit value, the upper end before the enlargement of one line is determined as the upper end of the moving area (step S318).

(IV) The lower end is determined by enlarging the moving region downward by the same method as the upward enlargement (steps S319 to S322).

  Finally, the moving area determination unit 302 records the detection result including the coordinate information of the enlarged moving area in the work area 113 (step S323), and finishes the process of FIG. 5-4.

  Here, the reason for adopting different methods for the left and right expansion of the moving area and the vertical expansion is that the memory access to a plurality of pixels on the same line can be performed at a high speed, but the pixels on different lines can be accessed. This is because it takes time to access the memory. In other words, if the horizontal expansion is performed sequentially one column at a time in the same manner as the top and bottom, memory access over all lines of the moving area is required even if only one column is expanded. However, under such a situation where the memory access time does not become a problem, the movement region may be expanded to the left and right by the same method as the vertical expansion. On the contrary, the movement region may be enlarged up and down by a simple method used for right and left enlargement.

  According to the moving region determination unit 302 of Example 1, since the validity of the initial candidate determined by the initial candidate determination unit 301 can be quantitatively determined, motion compensation using an inappropriate moving region is prevented. can do. In addition, when the initial candidate is valid, it is possible to search for a moving region having a larger size and having a large code amount reduction effect.

(B) Example 2 of moving area determination means 302
A processing example of the movement area determination unit 302 of Example 2 is shown in FIGS. Example 2 differs from Example 1 in that only a moving area larger in size than the initial candidate was searched in Example 1, whereas in Example 2, the moving area is excessively detected as an area larger than the true moving area. In consideration of the possibility that the area has been reduced, the possibility of the reduction of the area is first determined for each side, and the side that has not been excessively detected is enlarged as in the first example.

  First, the moving area determination unit 302 determines the validity of the moving area of the initial candidate by the same method as in Example 1 (Steps S331 and S332). When the initial candidate for the moving area is rejected, the moving area is no longer detected in this example as in Example 1, and the detection result indicating that the moving area has failed is recorded in the work area 113 (step S357), the process of FIG.

  On the other hand, when the initial candidate for the moving area is adopted, the following procedure is used to check whether the area can be further reduced vertically and horizontally and whether it can be expanded vertically and horizontally.

  First, the moving area determination unit 302 calculates the maximum reduction width from the right of the moving area of the initial candidate (step S333). Specifically, for each line of the moving region, the number of consecutive pixels in which the “pixel value after motion compensation” does not match the “true pixel value” when the region is narrowed from the right (the difference is greater than or equal to the threshold value). And the right end is determined with the minimum value of the number of continuous pixels as the maximum reduction width from the right. For example, as shown in FIG. 5-7, when the right edge of the initial candidate is narrowed from the right, the first line, the fourth line, and the fifth line are three consecutive pixels, and the remaining all lines are two consecutive pixels. If the “pixel value after motion compensation” and the “true pixel value” do not match, the maximum reduction width from the right is set to two pixels, which is the minimum value of the number of continuous pixels.

  Next, the moving area determination unit 302 determines whether or not the maximum reduction width is 0 (step S334). If the maximum reduction width is not 0, for example, as shown in FIG. A portion narrowed by the reduction width is determined as the right end of the movement region (step S335). If the maximum reduction width is 0, the maximum enlargement width to the right of the moving area is calculated in the same manner as in Example 1, and the right end is determined (step S336).

  Next, the moving area determination unit 302 calculates the maximum reduction width from the left end of the initial area in the same manner as the right end (step S337). If the maximum reduction width is not 0, the left end is determined from the maximum reduction width (step S338). 339). If the maximum reduction width is 0, the maximum extension width from the left end is calculated in the same manner as in Example 1, and the left end is determined (step S340).

  Next, the moving area determination unit 302 reduces the moving area by one line from the top, and calculates the merit value and demerit value when the line is reduced by the same method as the above-mentioned (a) and (b) (step) S341, S342). If the merit value is smaller than the demerit value (YES in step S343), the same reduction process is repeated for the next line (steps S344 to S346). If it is detected that the merit value is not smaller than the demerit value, the upper end before the reduction of one line is determined as the upper end of the movement region (step S347). On the other hand, if it is determined in step S343 that the merit value is not smaller than the demerit value, the maximum extension width above the moving region is calculated by the same method as in Example 1 and the upper end is determined (step S348).

  Next, the movement area determination means 302 performs the same processing from the bottom of the movement area as from the top (steps S349 to S356).

  Finally, the moving area determination unit 302 records the detection result including the coordinate information of the moving area in which the upper, lower, left, and right ends are determined in the work area 113 (step S357), and ends the processing of FIG. 5-6.

  Here, the reason why different methods are adopted for the reduction from the left and right of the moving region and the reduction from the top and bottom is that memory access to a plurality of pixels on the same line can be performed at a high speed, but to the pixels on different lines This is because it takes time to access the memory. In other words, if the horizontal reduction is performed one column at a time in the same manner as the top and bottom, memory access over all the lines of the moving area is required even by reducing one column. However, under such a situation where the memory access time does not become a problem, the movement area may be reduced from the left and right by the same method as the reduction from the top and bottom. Conversely, reduction from the top and bottom of the moving area may be performed by a simple method used for reduction from the left and right.

  According to the moving region determination unit 302 of this example 2, the validity of the initial candidate determined by the initial candidate determination unit 301 can be quantitatively determined, so that motion compensation using an inappropriate moving region is prevented. can do. In addition, when the initial candidate is valid, it tries to reduce from the top, bottom, left, and right, so if the initial candidate's moving area is excessively detected as a larger area than the true moving area, the excess detection amount should be reduced. Is possible. Furthermore, the side where there is no possibility of excessive detection can be expanded to a larger moving region with a large code amount reduction effect.

(C) Example 3 of moving area determination means 302
A processing example of the movement area determination means 302 of Example 3 is shown in FIGS. The difference between Example 3 and Example 2 is that in Example 3, when the merit value calculated for the initial candidate was lower than the demerit value, detection of the moving region was no longer given, whereas in Example 3, the move In consideration of the possibility that the area is detected to be extremely larger than the true moving area, the possibility of reducing the area is determined for each side.

  First, the moving area determination unit 302 determines the validity of the moving area of the initial candidate by the same method as in Example 2 (Steps S361 and S362). Processing step S363 when the initial candidate for the moving area is not rejected (YES in step S362) is the same as steps S333 to S356 of Example 2.

  On the other hand, when the initial candidate for the moving area is rejected, it is checked whether the area can be further reduced from the top, bottom, left, and right by the following procedure.

  First, the moving area determination unit 302 calculates the maximum reduction width from the right of the moving area of the initial candidate by the same method as in Example 2 (step S364). Next, the moving area determination unit 302 determines whether or not the maximum reduction width is equal to the horizontal width of the moving area (step S365). If the maximum reduction width is equal to the horizontal width of the moving area, it is determined that the detection of the moving area has failed. Then, a detection result to that effect is generated (step S372), and the processing of FIG. If the maximum reduction width is not equal to the horizontal width of the moving area, a portion narrowed by the maximum reduction width from the right end of the initial candidate is determined as the right end of the moving area (step S366).

  Next, the moving area determination unit 302 calculates the maximum reduction width from the left end of the initial area in the same manner as the right end, and determines the left end (step S367).

  Next, the moving area determination unit 302 calculates the maximum reduction width from above the moving area by the same method as in Example 2 (step S368). If the maximum reduction width is equal to the vertical width of the moving area, the detection result indicating that the moving area has failed is generated (YES in step S369, step S372), and the processing of FIG. finish. If the maximum reduction width is not equal to the vertical width of the movement area, the upper end of the movement area is determined from the maximum reduction width (step S370).

  Next, the moving area determining means 302 calculates the maximum reduction width from the bottom of the moving area in the same manner as from above, and determines the lower end (step S371).

  Finally, the moving area determination unit 302 records the detection result including the coordinate information of the moving area in which the upper, lower, left, and right end portions are determined in the work area 113 (step S372), and ends the process of FIG.

  According to the moving region determination unit 302 of this example 3, since the validity of the initial candidate determined by the initial candidate determination unit 301 can be quantitatively determined, motion compensation using an inappropriate moving region is prevented. can do. Even if the initial candidate is rejected, in order to search for the possibility of reduction, even if the moving area of the initial candidate is detected to be excessively larger than the true moving area, the moving area is set as much as possible. It becomes possible to detect. Further, as in Example 2, when the initial candidate is valid, first, the reduction from the top, bottom, left, and right is attempted. Therefore, if the initial candidate moving area is excessively detected as an area larger than the true moving area, excessive It is possible to reduce the amount of detection, and further, it is possible to expand the side where there is no possibility of overdetection to a moving region having a larger size that has a large code amount reduction effect.

(D) Example 4 of moving area determining means 302
A processing example of the movement area determination unit 302 of Example 4 is shown in FIGS. The difference between Example 4 and Example 2 is that in Example 2, the validity of the initial candidate is determined, and when it is determined to be valid, the moving region is reduced and expanded, whereas in Example 4, the initial candidate is It is in the point of omitting the determination of the validity of and trying to reduce or expand the initial candidate.

  First, the moving area determination unit 302 calculates the maximum reduction width from the right of the moving area of the initial candidate by the same method as in Example 2 (step S381). Next, the moving area determination unit 302 determines whether or not the maximum reduction width is equal to the horizontal width of the moving area (step S382). If the maximum reduction width is equal to the horizontal width of the moving area, it is determined that the detection of the moving area has failed. Then, a detection result to that effect is generated (step S399), and the processing of FIG.

  If the maximum reduction width is not equal to the horizontal width of the movement area, the movement area determination unit 302 determines whether or not the maximum reduction width is 0 (step S383). If not, the movement area determination unit 302 narrows the maximum reduction width from the right end of the initial candidate by the maximum reduction width. Is determined as the right end of the movement area (step S384). If the maximum reduction width is 0, the moving area determination unit 302 calculates the maximum enlargement width to the right by the same method as in Example 2 and determines the right end (step S385).

  Next, the moving area determination unit 302 calculates the maximum reduction width from the left of the moving area of the initial candidate by the same method as in Example 2 (step S386), and if the maximum reduction width is not 0 (NO in step S387). Then, a portion narrowed by the maximum reduction width from the left end of the initial candidate is determined as the left end of the moving region (step S388). If the maximum reduction width is 0, the moving area determination unit 302 calculates the maximum enlargement width to the left by the same method as in Example 2 and determines the left end (step S389).

  Next, the moving area determination unit 302 calculates the maximum reduction width from above the moving area by the same method as in Example 2 (step S390). If the maximum reduction width is equal to the vertical width of the moving area, the detection result indicating that the moving area has failed is generated (YES in step S391, S399), and the processing in FIG. To do. If the maximum reduction width is not equal to the vertical width of the moving area, it is determined whether or not the maximum reduction width is 0 (step S392). If it is not 0, a position narrowed by the maximum reduction width from the upper end of the initial candidate is determined. The upper end is determined (step S393). If the maximum reduction width is 0, the moving area determination unit 302 calculates the maximum enlargement width upward using the same method as in Example 2 and determines the upper end (step S394).

  Next, the moving area determining means 302 calculates the maximum reduction width from the bottom of the moving area by the same method as in Example 2 (step S395). If it is not 0, a location narrowed by the maximum reduction width from the lower end of the initial candidate. Is determined as the lower end of the movement area (NO in step S396, S397). On the other hand, if the maximum reduction width is 0, the moving area determination unit 302 calculates the maximum downward expansion width by the same method as in Example 2 and determines the lower end (step S398).

  Finally, the moving area determination unit 302 records the detection result including the coordinate information of the moving area in which the upper, lower, left and right ends are determined in the work area 113 (step S399), and finishes the process of FIG. 5-9.

  According to the moving area determination unit 302 of Example 4, since the validity of the initial candidate determined by the initial candidate determination unit 301 is not quantitatively determined, the processing amount can be reduced. In addition, since the first candidate moving area is excessively detected as a larger area than the true moving area in order to try to reduce from the top, bottom, left and right, it becomes possible to reduce the excess detection amount, The side where there is no possibility of excessive detection can be expanded to a larger moving region that has a large code amount reduction effect. However, since the validity of the moving area of the initial candidate is not determined, there is a possibility that an area where the donut-shaped hole part is completely different before and after the movement is detected as the moving area, for example.

(3) Update area detection area setting means 124
Referring to FIG. 6A, the first embodiment of the update area detection area setting unit 124 includes a movement area presence / absence determination unit 401, a movement direction determination unit 402, and a division unit 403. Each has the following functions in general.

  The moving region presence / absence determining unit 401 has a function of determining whether or not a moving region has been detected by the moving region detecting unit 122.

  The movement direction determination unit 402 has a function of determining the movement direction of the movement region detected by the movement region detection unit 122.

  The dividing unit 403 has a function of determining the necessity of screen division and setting an update region detection area by screen division according to the determination results of the moving region presence / absence determining unit 401 and the moving direction determining unit 402.

  Next, a first processing example of the update area detection area setting unit 124 of this embodiment will be described.

  The movement area presence / absence determination means 401 of the update area detection area setting means 124 reads out and analyzes the detection result of the movement area detection means 122 from the work area 113, thereby determining whether or not a movement area has been detected. Notification is made to the moving direction determining means 402 and the dividing means 403 (step S501 in FIG. 6-2).

  When the movement direction determination means 402 receives a notification that the movement area has been detected from the movement area presence / absence determination means 401, the movement direction determination means 402 moves before movement included in the detection result of the movement area detection means 122 read from the work area 113. By comparing the coordinates of the area with the coordinates of the moved area after movement, the direction in which the moving direction includes a component from the top to the bottom of the screen (hereinafter referred to as the downward direction), the component from the bottom to the top of the screen Is determined (hereinafter referred to as the upward direction), and the determination result is notified to the dividing means 403 (step S502). In addition to the movement direction, the determination result includes the coordinates of the upper end of the movement area after movement in the case of the downward direction, and the coordinates of the lower end of the movement area after the movement in the case of the upward direction. In addition, as a method of handling in the left-right direction that is neither downward nor upward, for example, it can be considered to include either the downward or upward direction.

  When the dividing unit 403 receives notification from the moving region presence / absence determining unit 401 that the moving region has not been detected, the dividing unit 403 sets the entire screen as one update region detecting region (step S503). When the notification that the moving area is detected is received from the moving area presence / absence determining unit 401, the screen is divided in accordance with the notification from the moving direction determining unit 402 (steps S504 to S506). Specifically, if the movement direction is downward, the screen is divided into two at the upper end of the moved area after movement, and each divided area is set as one update area detection area. If the moving direction is upward, the screen is divided into two at the lower end of the moving area after movement, and each divided area is set as one update area detection area. Thereafter, the update area detection unit 125 detects the update area for each update area detection area.

  The effect of the update area detection area setting means 124 of the first processing example will be described. Although the case where the moving direction is the downward direction is described below, the same effect can be obtained when the moving direction is the upward direction.

  As shown in the upper left of FIG. 6-3, when the moving area moves downward, setting the entire screen as the update area detection area corresponds to the moving area before the movement as shown in the upper right of FIG. 6-3. The entire area is detected as an update area. On the other hand, in this example, as shown in the lower right of FIG. 6-3, the screen is divided into two at the upper end of the moved area after movement, and the update area is detected in each update area detection area. The total area of the regions can be minimized, and the amount of codes can be reduced.

  Next, a second processing example of the update area detection area setting unit 124 of this embodiment will be described.

  The moving area presence / absence determining means 401 of the update area detecting area setting means 124 determines whether or not a moving area has been detected, as in the first processing example, and notifies the moving direction determining means 402 and the dividing means 403 of the determination result. (Step S511 in FIG. 6-4).

  Similar to the first processing example, when the movement direction determination unit 402 receives a notification that the movement region has been detected from the movement region presence determination unit 401, the movement direction determination unit 402 determines whether the movement direction is a downward direction or an upward direction. The determination is made and the determination result is notified to the dividing means 403 (step S512). In addition to the movement direction, the determination result includes the coordinates of the upper and lower ends of the movement area after the movement in both the downward direction and the upward direction.

  When the dividing unit 403 receives a notification that the moving area is not detected from the moving area presence / absence determining unit 401, the dividing unit 403 sets the entire screen as one update area detecting area as in the first processing example (step S513). ). When the notification that the moving area is detected is received from the moving area presence / absence determining unit 401, the screen is divided in accordance with the notification from the moving direction determining unit 402 (steps S514 to S516). Specifically, the screen is divided into three at the upper and lower ends of the moving area after movement in both the downward direction and the upward direction, and each divided area is set as one update area detection area. Thereafter, the update area detection unit 125 detects the update area for each update area detection area.

  Next, the effect of the update area detection area setting unit 124 of this processing example will be described. Although the case where the moving direction is the downward direction is described below, the same effect can be obtained when the moving direction is the upward direction.

  As shown in the upper left of FIG. 6-5, when the moving area moves downward, setting the entire screen as the update area detecting area corresponds to the moving area before moving as shown in the upper right of FIG. 6-5. The entire area is detected as an update area. On the other hand, in this example, as shown in the lower right of FIG. 6-5, the screen is divided into three at the upper and lower ends of the movement area after movement, and the update area is detected in each update area detection area. The total area of the update area can be minimized, and the code amount can be reduced.

  Also, as shown in the upper left of FIG. 6-6, when the detected moving area is smaller than the actual moving area, in the first processing example of FIG. As shown in the upper right of FIG. 6-6, a large update area is unnecessarily detected. On the other hand, in this example, as shown in the lower right of FIG. 6-6, the screen is divided into three at the upper and lower ends of the movement area after movement, and the update area is detected in each update area detection area. The total area of the update area can be reduced, and the code amount can be reduced accordingly.

  Next, a third processing example of the update area detection area setting unit 124 of this embodiment will be described.

  The moving area presence / absence determining means 401 of the update area detecting area setting means 124 determines whether or not a moving area has been detected as in the second processing example, and notifies the moving direction determining means 402 and the dividing means 403 of the determination result. (Step S521 in FIG. 6-7).

  Similar to the second processing example, when the movement direction determination unit 402 receives a notification that the movement region has been detected from the movement region presence / absence determination unit 401, the movement direction determination unit 402 determines whether the movement direction is a downward direction or an upward direction. The determination is made, and the determination result is notified to the dividing means 403 (step S522). In addition to the moving direction, the judgment result includes the coordinates of the upper and lower ends of the moving area after moving and the lower end of the moving area before moving if the moving direction is downward. If the moving direction is upward, The coordinates of the upper and lower ends of the movement area after movement and the upper end of the movement area before movement are included.

  When the dividing unit 403 receives notification from the moving region presence / absence determining unit 401 that the moving region has not been detected, the dividing unit 403 sets the entire screen as one update region detecting region as in the second processing example (step S523). ). When the notification that the moving area is detected is received from the moving area presence / absence determining unit 401, the screen is divided in accordance with the notification from the moving direction determining unit 402 (steps S524 to S526). Specifically, when the moving direction is downward, the screen is divided into four at the upper and lower ends of the moving area after moving and the lower end of the moving area before moving, and each divided area is set as one update area detection area. . When the moving direction is upward, the screen is divided into four at the upper and lower ends of the moving area after moving and the upper end of the moving area before moving, and each divided area is set as one update area detecting area. Thereafter, the update area detection unit 125 detects the update area for each update area detection area.

  Next, the effect of the update area detection area setting unit 124 of this processing example will be described. Although the case where the moving direction is the downward direction is described below, the same effect can be obtained when the moving direction is the upward direction.

  As shown in the upper left of FIG. 6-8, when the moving area moves downward, setting the entire screen as the update area detecting area corresponds to the moving area before moving as shown in the upper right of FIG. 6-8. The entire area is detected as an update area. On the other hand, in this example, as shown in the lower right of FIG. 6-8, the screen is divided into four at the upper and lower ends of the moving area after movement and the lower end of the moving area before movement, and is updated in each update area detection area. Since the area is detected, the total area of the update area can be minimized, and the code amount can be reduced.

  Also, as shown in the upper left of FIG. 6-9, when the detected moving area is smaller than the actual moving area, the first processing example of FIG. As shown in the upper right of FIG. 6-9, a large update area is unnecessarily detected. On the other hand, in this example, as shown in the lower right of FIG. 6-9, the screen is divided into four at the upper and lower ends of the moving area after movement and the lower end of the moving area before movement, and updated in each update area detection area. Since the area is detected, the total area of the update area can be reduced, and the amount of code can be reduced accordingly.

  Further, as shown in the upper left of FIG. 6-10, when the detected moving area is larger than the actual moving area, in the first processing example of FIG. As shown in the upper right of FIG. 6-10, a large update area is unnecessarily detected. Further, in the second processing example of FIG. 6-4 in which the screen is divided only by the upper and lower ends after movement, the update area becomes slightly redundant as shown in the lower right of FIG. 6-10. On the other hand, in this example, as shown in the lower left of FIG. 6-10, the screen is divided into four at the upper and lower ends of the moving area after the movement and the lower end of the moving area before the movement. Therefore, the total area of the update region can be reduced compared to the second processing example, and the amount of code can be reduced accordingly. However, if the area of the excessively detected region is not so large, the second processing example has an advantage that the number of update regions is reduced.

  Referring to FIG. 6-11, the second embodiment of the update area detection area setting means 124 includes a movement area presence / absence determination means 411, a movement area overlap determination means 412, a movement direction determination means 413, and a dividing means 414. Consists of Each has the following functions in general.

  The movement area presence / absence determination means 411 and the movement direction determination means 413 have the same functions as the movement area presence / absence determination means 401 and the movement direction determination means 402 in the first embodiment of the update area detection area setting means 124.

  The movement area overlap determination unit 412 has a function of determining whether or not there is a possibility of overlapping of the movement areas before and after the movement detected by the movement area detection unit 122.

  The dividing unit 414 has a function of determining the necessity of screen division and setting an update region detection area by screen division according to the determination results of the moving region presence / absence determining unit 411, the moving region overlap determining unit 412 and the moving direction determining unit 413. .

  Next, a processing example of the update area detection area setting unit 124 of this embodiment will be described.

  The movement area presence / absence determination means 411 of the update area detection area setting means 124 determines whether or not a movement area has been detected in the same manner as the movement area presence / absence determination means 401 of the first embodiment, and determines the determination result as a movement area overlap determination means. 412 and the dividing unit 414 are notified (step S531 in FIG. 6-12).

  When the movement area overlap determination unit 412 receives a notification that the movement area is detected from the movement area presence / absence determination unit 401, the movement area overlap determination unit 412 includes the coordinates of the movement area before the movement included in the detection result of the movement area detection unit 122 from the work area 113. And the coordinates of the moving area after the movement are read out, and at least one of the area where the moving area before the movement is enlarged by a predetermined width Δ vertically and horizontally and the area after the movement is enlarged by a predetermined width Δ vertically and horizontally. In the case of overlapping, the determination result of the overlapping of the moving regions is notified to the moving direction determining means 413 and the dividing means 414 if the overlapping does not overlap (step 414). S532). Here, the predetermined width Δ is set in advance in accordance with the degree of insufficient detection of the moving area.

  When the movement direction determination unit 413 receives the notification that there is no overlap between the movement regions from the movement region overlap determination unit 412, the movement direction determination unit 413 determines the movement region before the movement included in the detection result of the movement region detection unit 122 read from the work area 113. By comparing the coordinates with the coordinates of the moved area after the movement, it is determined whether the moving direction is the downward direction or the upward direction, and the determination result is notified to the dividing unit 414 (step S533). The determination result includes coordinates for dividing the screen in addition to the moving direction as in the moving direction determining unit 402 in the first embodiment.

  When the dividing unit 414 receives a notification that the moving region has not been detected from the moving region presence / absence determining unit 411 and when the moving unit overlap determining unit 412 receives a notification that there is no overlapping of moving regions, the dividing unit 414 One update area detection area is set (step S534). On the other hand, when a notification indicating that a moving region has been detected is received from the moving region presence / absence determining unit 411, and when a moving region overlap notification is received from the moving region overlap determining unit 412, the notification from the moving direction determining unit 413 is followed. As in any of the first processing example, the second processing example, and the third processing example of the dividing unit 403 according to the first embodiment, the screen is divided and the update area detection area is set (steps S535 to S537). ). Thereafter, the update area detection unit 125 detects the update area for each update area detection area.

  According to the update area detection area setting means 124 of the second embodiment, the screen is not divided when there is no possibility that the movement areas before and after the movement overlap, so that an increase in the number of divisions of the update area is suppressed. Can do.

(4) Update area detection means 125
Referring to FIG. 7A, the first embodiment of the update region detection unit 125 includes a pixel comparison unit 601 and an update region extraction unit 602, and each update region set by the update region detection region setting unit 124. For each detection area, an update area that is a difference area between the reference frame after motion compensation and the current frame is detected. The pixel comparison unit 601 and the update region extraction unit 602 generally have the following functions.

  The pixel comparison unit 601 increases, for each update region detection area to be processed, a difference between pixel values at the same position in the reference frame after motion compensation and the current frame, which is larger than the first threshold value and the first threshold value. It has a function of comparing with a second threshold value.

  The update area extraction unit 602 includes, for each update area detection area to be processed, a block including pixels in which a difference greater than the second threshold is detected among pixels in which a difference greater than the first threshold is detected. Is extracted as an update area.

  Next, the operation of the update area detection unit 125 of this embodiment will be described.

  The update area detection means 125 reads the update area detection area information set by the update area detection area setting means 124 from the work area 113 and pays attention to one of the update area detection areas (step S701 in FIG. 7-2). . Next, an update area is extracted from the update area detection area under attention, and the extraction result is stored in the work area 113 (step S702). When the update region detection unit 125 finishes the process of extracting the update region from one update region detection region, the update region detection unit 125 moves attention to the next one update region detection region (step S703), and repeats the same processing as described above. . When the update area extraction process from all the update area detection areas is completed (YES in step S704), the process of FIG.

  Next, the process executed in step S702 will be described in detail with reference to the flowchart of FIG.

  First, the update area detection unit 125 initializes the upper end buffer, the lower end buffer, and the flag buffer used for the update area extraction processing (step S711). Each buffer has a one-to-one entry in each column of the frame. Among these, the upper end buffer is used to hold the row number of the highest row in which a difference larger than the first threshold is detected for each column, and the lower end buffer detects a difference larger than the first threshold. It is used to hold the row number of the lowest row for each column. The flag buffer holds a flag indicating whether or not a difference larger than the second threshold is detected for each column.

  Thereafter, the following processing is executed by the pixel comparison unit 601 of the update region detection unit 125.

  First, the pixel comparison unit 601 pays attention to the first pixel pair among a plurality of pixel pairs included in the update region detection area of the reference frame after the motion compensation and the current frame (S712). For example, as shown in FIG. 7-4, when the update region detection area of interest starts from the first row of the frame, the pixel P (0, 0) of the reference frame after motion compensation and the pixel P (0 of the current frame) , 0).

  Next, the pixel comparison unit 601 calculates the difference between the pixel values of the pixel pair of interest (step S713). Next, the difference is compared with a first threshold (step S714), and if the difference is larger than the first threshold, the upper end buffer and the lower end buffer are updated (step S715). Specifically, for the upper end buffer, if the upper end buffer entry corresponding to the column in which the pixel of interest is located is NULL, the number of the row in which the pixel of interest is located is recorded in the entry, not NULL If the line number has already been recorded, leave it as it is. On the other hand, for the lower end buffer, the number of the row where the pixel of interest is unconditionally recorded is recorded in the entry of the lower end buffer corresponding to the column where the pixel of interest is located.

  Next, the pixel comparison unit 601 compares the difference with the second threshold (step S716), and updates the flag buffer if the difference is greater than the second threshold (step S717). Specifically, 1 is unconditionally recorded in the entry of the flag buffer corresponding to the column where the pixel of interest is located.

  Next, the pixel comparison unit 601 shifts attention to the pixel pair of the next column in the same row in both frames (step S718), and returns to step S713. If the difference is not greater than the first threshold, the upper end buffer and the lower end buffer are not updated. If the difference is greater than the first threshold but not greater than the second threshold, the flag buffer is not updated.

  Here, the calculation of the difference between the pixel values is performed for each of R, G, and B components, for example. The comparison with the first and second threshold values is performed for each component difference, and if the difference between at least one component is greater than the threshold value, it is determined that the pixel value difference is greater than the threshold value.

  When the pixel comparison unit 601 finishes the process for the pixel pair for one row in the update region detection area under attention (YES in step S719), the pixel comparison unit 601 has called the process start time or the update region extraction unit 602 in the past. For example, the number of consecutive rows in which no difference greater than the first threshold has been detected since the previous call, that is, the number of consecutive non-updated rows is counted (step S720) and compared with a preset threshold value L (step S720). S721). Here, the threshold value L is set to a value of 1 or more (for example, 8) in order to avoid excessive division of the update area. If the number of consecutive non-updated rows exceeds the threshold L, the update region extraction unit 602 is called by specifying the first row and the last row of the update region extraction range, and update region detection processing by column division is performed. (Step S722). If the update area extraction means 602 has not been called in the past, the first line of the update area extraction range is the first line of the frame, and if it has been called, it is the line following the last line specified at the previous call. In addition, the last row of the update area extraction range is a row that has been processed for the pixels in the last column at the present time.

  When the process of the update region extraction unit 602 is completed, the pixel comparison unit 601 moves attention to the first pixel pair in the next row of the frame (step S723), and returns to step S713.

  If the number of consecutive non-updated rows does not exceed the threshold L, the pixel comparison unit 601 shifts attention to the first pixel pair in the next row of the frame without calling the update region extraction unit 602 (step S723), the process returns to step S713.

  Further, when the pixel comparison unit 601 finishes the process until the last pixel pair in the last row of the update area detection area of interest (YES in step S724), the process start point or the update area extraction unit 602 is set in the past. If it is called, it is determined whether or not there is a row in which a difference greater than the first threshold is detected after the previous call time (step S725). If there is no row, the processing of FIG. If it exists, the first and last rows of the update area extraction range are designated, and the update area extraction means 602 is called (step S726). After the update area detection processing by column division is completed, FIG. The process of 3 is finished. If the update area extraction means 602 has not been called in the past, the first line of the update area extraction range is the first line of the frame, and if it has been called, it is the line following the last line specified at the previous call. The last row of the update area extraction range is the last row of the frame.

  The matrix drawn on the upper side of FIG. 7-4 shows an example of the difference situation between the reference frame after motion compensation and the current frame, and one square shows the difference situation of one pixel pair. In addition, a blank cell has a difference smaller than the first threshold, a hatched cell has a difference larger than the first threshold and smaller than the second threshold, and a black cell has a difference. Indicates that it is greater than the second threshold. Under such circumstances, when the above-described operation is performed by the pixel comparison unit 601 for the range up to the ninth line of the frame, the upper end buffer, the lower end buffer, and the flag buffer include the lower side of FIG. The contents shown in Fig. 6 are recorded. Here, the numerical values in the upper end buffer and the lower end buffer indicate row numbers, and the symbol “-” indicates NULL. Further, 0 and 1 in the flag buffer indicate flag values, and a value 1 indicates that the second threshold value has been exceeded. If the threshold L is, for example, 3 rows, the number of consecutive non-updated rows becomes 4 when the processing up to the 9th row is finished, and exceeds the threshold L, so the update region extraction means 602 is called. .

  Next, update area detection processing by column division executed by the update area extraction unit 602 will be described with reference to the flowchart of FIG.

  The update region extraction unit 602 refers to the upper end buffer or the lower end buffer, and updates columns (a group of columns in which difference pixels exist) and non-update columns (difference pixels exist) from the update region extraction range specified in the current call. A group of columns that have not been performed is extracted (step S731). For example, in the case of FIG. 7-4, when referring to the entries in the upper end buffer in order from column 0, since one NULL is consecutive, 0 column is extracted as a non-update column (0-0), and then a numerical value is recorded. Since there are five consecutive entries, the first column to the fifth column are extracted as the update column (1-5). Similarly, the non-update column (6-7), the update column (8-9), the non-update column (10-14), the update column (15-16), and the like are extracted.

  Next, the update region extraction unit 602 combines adjacent update columns into one update column with non-update columns having a predetermined number W or less in order to avoid excessive division of the update region (step S732). For example, when W is 3, in the case of FIG. 7-4, the update sequence (1-5) and the update sequence (8-9) are combined as the update sequence (1-9).

  Next, the update area extraction unit 602 refers to the flag buffer and changes the update sequence in which the flag values are all 0 to a non-update sequence (step S733). For example, in the case of FIG. 7-4, referring to the flags corresponding to the columns 1 to 9 in the flag buffer with respect to the combined update column (1-9), the value 1 is included. 9) is left as it is. On the other hand, referring to the flag corresponding to the column 15-16 in the flag buffer with respect to the update column (15-16), since all values are 0, it is determined that the update column (15-16) is likely to be caused by noise. Changed to a non-updated column.

  Next, the update area extraction unit 602 examines the uppermost and lowermost rows in which the difference pixels are generated for each update column, and determines the update rectangle that defines the update area, together with the left and right ends of the update column. (Step S734). With this processing, for the update sequence (1-9), the uppermost buffer is 2 when referring to the upper end buffer, the lowermost end is 5 when referring to the lower end buffer, the left end of the update sequence is 1 and the right end is 9, so the update rectangle is When defined by the upper left and lower right end points, the upper left end point (2, 1) and the lower right end point (5, 9) are obtained. The information of the update area thus obtained (coordinates of the update rectangle) is recorded in the work area 113 as a part of the update area detection result.

  Next, the update area extraction unit 602 initializes the upper end buffer, the lower end buffer, and the flag buffer (step S735), and ends the processing of FIG. 7-5. In the processing of FIG. 7-5, an update column in which there are no pixels exceeding the second threshold after combining update columns adjacent to each other with a non-update column having a predetermined number of columns W or less in between. Is changed to a non-updated column, but on the contrary, an update column in which no pixel exceeding the second threshold exists is changed to a non-update column, and then adjacent to each other with a non-update column having a predetermined number W or less in between. It is also possible to perform processing for combining the update columns to be combined into one update column.

  Next, the effect of the update area detection unit 125 of this embodiment will be described.

  According to the update area detection means 125 of the present embodiment, the update area of the computer screen captured in analog can be detected with high accuracy. The reason is that, using two types of threshold values, a first threshold value and a second threshold value larger than the first threshold value, a difference larger than the second threshold value among the pixel clusters in which a difference larger than the first threshold value is detected. In order to extract a block including pixels in which an update is detected as an update region, it is possible to prevent excessive detection of an update region that is likely to occur when the update region is detected using only the first threshold, and only the second threshold is used. This is because it is possible to prevent insufficient detection of the update area, which is likely to occur when the update area is detected using.

  Specifically, for example, when there is a pixel change in a gradation part such as a moving image, even if only the change amount of a single pixel value is referred to, whether the pixel has been redrawn or the pixel value due to noise accompanying analog capture It is difficult to identify whether this is a change. For these reasons, the detection of the update area in the moving image may fail with a single threshold value. For example, in the experimental example shown in FIG. 7-6 in which only the moving image window at the center of the screen is updated in the front and rear frames 1 and 2, it is desirable that the entire moving image window at the center is detected as the update region. However, if only a small threshold value is used, the detection area becomes excessive as shown in the lower left of FIG. 7-6. Conversely, if only a large value threshold is used, detection is performed as shown in the lower right of FIG. 7-6. Insufficient space. If the detection becomes excessive, the amount of code increases even when the screen update is slight. Further, when a detection failure occurs over a plurality of frames, a boundary with a discontinuous luminance is perceived between a region where detection is successful and a region where detection is lost.

  On the other hand, according to the update region detection means 125 of the present embodiment in which two types of threshold values for difference determination (large and small) are set, as shown in the experimental example of FIG. Can be detected as an update area without excess or deficiency.

  In addition, according to the update area detection unit 125 of the present embodiment, the update area is detected unnecessarily large as compared with the method of detecting the update area with one rectangle circumscribing all the update areas existing in the update area detection area. Can be prevented.

  Further, according to the update area detection means 125 of the present embodiment, the update area of the computer screen can be detected at high speed. The reason is that the top and bottom buffers that hold the coordinates of the top and bottom edges of the difference pixels for each column of the frame, and the pixels of the reference frame and the current frame are compared in raster scan order, and the difference is greater than or equal to the first threshold. A pixel comparison unit 601 that rewrites the coordinates of the upper and lower ends of the corresponding column in the upper and lower end buffers when a pixel is found, and an update region extraction unit that determines an update region with reference to the upper and lower end buffers when a predetermined number of non-updated rows continue. This is because the update area can be detected by so-called one-pass processing.

1 is a block diagram of a video signal encoding device according to an embodiment of the present invention. It is a flowchart which shows the flow of a process of the video signal encoding apparatus which concerns on embodiment of this invention. It is explanatory drawing of the encoding process of the video signal by the video signal encoding apparatus which concerns on embodiment of this invention. It is a block diagram of the 1st Example of a movement vector detection means. It is a flowchart which shows the flow of a process of the movement vector detection means based on a 1st Example. It is explanatory drawing of the edge extraction process in the movement vector detection means based on a 1st Example. It is a figure which shows an example of the hash table of the present frame used with the movement vector detection means based on 1st Example. It is a figure which shows an example of the hash table of the previous frame used with the movement vector detection means based on 1st Example. It is a figure which shows an example of the detection result of the movement vector detection means based on a 1st Example. Relationship between an image obtained by plotting a pair of feature points included in a list of most frequent movement vector candidates detected by the movement vector detection unit according to the first embodiment in the previous frame and the current frame, and the estimated movement vector FIG. It is a block diagram of the 1st Example of a movement area | region detection means. It is a flowchart which shows the flow of a process of the movement area | region detection means based on a 1st Example. It is a figure which shows the example which makes the rectangle which circumscribes the feature point group into a movement area in the movement area detection means based on 1st Example. It is a flowchart which shows the 1st process example of the movement area determination means in the movement area detection means which concerns on a 1st Example. It is explanatory drawing of the method of determining the expansion width to the right of a movement area in the movement area detection means based on a 1st Example. It is a flowchart which shows the 2nd process example of the movement area determination means in the movement area detection means which concerns on a 1st Example. It is explanatory drawing of the method of determining the reduction width from the right of a movement area in the movement area detection means based on a 1st Example. It is a flowchart which shows the 3rd processing example of the movement area | region determination means in the movement area detection means based on 1st Example. It is a flowchart which shows the 4th example of a process of the movement area determination means in the movement area detection means based on 1st Example. It is a block diagram of the 1st Example of the update area detection area setting means. It is a flowchart which shows the 1st process example of the update area | region detection area setting means based on a 1st Example. It is explanatory drawing of the effect by the 1st process example of the update area | region detection area setting means which concerns on a 1st Example. It is a flowchart which shows the 2nd process example of the update area | region detection area setting means based on a 1st Example. It is explanatory drawing of the effect by the 2nd process example of the update area | region detection area setting means which concerns on a 1st Example. It is explanatory drawing of the effect by the 2nd process example of the update area | region detection area setting means which concerns on a 1st Example. It is a flowchart which shows the 3rd processing example of the update area | region detection area setting means which concerns on a 1st Example. It is explanatory drawing of the effect by the 3rd process example of the update area | region detection area setting means which concerns on a 1st Example. It is explanatory drawing of the effect by the 3rd process example of the update area | region detection area setting means which concerns on a 1st Example. It is explanatory drawing of the effect by the 3rd process example of the update area | region detection area setting means which concerns on a 1st Example. It is a block diagram of 2nd Example of an update area detection area setting means. It is a flowchart which shows the process example of the update area | region detection area setting means which concerns on a 2nd Example. It is a block diagram of the 1st Example of an update area | region detection means. It is a flowchart which shows the flow of a process of the update area | region detection means based on a 1st Example. It is a flowchart which shows the process example by the pixel comparison means in the update area | region detection means which concerns on a 1st Example. It is a figure which shows the example in which the upper end buffer, lower end buffer, and flag buffer used with the update area | region detection means based on 1st Example are updated according to the difference condition of the reference frame after motion compensation, and the present frame. It is a flowchart which shows the process example by the update area extraction means in the update area detection means based on 1st Example. It is a figure which shows the experimental example of the update area detection by a single threshold value. It is a figure which shows the experiment example of the update area detection by the update area detection means which concerns on a 1st Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 ... Image input device 102 ... Data storage device 103 ... Data processing device 104 ... Code output device 111 ... Encoding object frame storage unit 112 ... Reference frame storage unit 113 ... Work area 121 ... Movement vector detection means 122 ... Movement area detection means 123... Motion compensation means 124... Update area detection area setting means 125... Update area detection means 126.

Claims (25)

A moving area detecting means for detecting, as a moving area, an image area which is the same or similar image area existing in both the previous frame and the current frame and whose position on the screen is changed;
Motion compensation means for copying the movement area detected by the movement area detection means to a position after movement on the previous frame;
The mobile determines the moving direction of the detected moving region in the region detection means, in addition to the lower end on the moving region after movement when the movement direction which is the determination comprises a component directed from top to bottom of the screen the screen is divided by the lower end of the moving region before movement, when said determined movement direction includes a component directed from the bottom to the top of the screen in addition to the upper and lower ends of the moving region after movement, the movement before movement An update area detection area setting means for dividing the screen by the upper end of the area and setting each of the divided areas as an update area detection area that is a unit of processing for detecting the update area;
Update area detection means for detecting, as an update area, an area where the previous frame after copying is different from the current frame for each update area detection area set by the update area detection area setting means. Update area detection device. The update area detection area setting means determines whether or not the movement areas before and after the movement detected by the movement area detection means overlap, and does not perform the division when it is determined that there is no possibility of overlap. The update area detection apparatus according to claim 1, wherein the entire screen is set as an update area detection area. The update area detection area setting means determines whether or not a movement area is detected by the movement area detection means. If no movement area is detected, the entire screen is set as an update area detection area without performing the division. setting update region detection device according to claim 1 or 2, characterized in that. The update area detection means compares the pixel values of pixels at the same position in the previous frame and the current frame, according to claim 1, wherein detecting the cluster of pixels with a difference in pixel value as an update region The update area | region detection apparatus of any one of these. The update area detection apparatus according to claim 4 , wherein the update area detection unit uses a rectangle circumscribing the block of pixels as an update area. The update area detection means sequentially compares the pixels of the previous frame and the current frame one row at a time, and records, for each column, the upper row coordinates and the lower row coordinates where a difference larger than the first threshold is detected. In addition, it is recorded whether or not there is a pixel in which a difference greater than the second threshold is detected between the upper end and the lower end, and a row in which a difference greater than the first threshold is not detected continues for a predetermined number of rows. At that time, referring to the record, an update column including a group of columns in which a difference greater than the first threshold is detected and including a pixel in which a difference greater than the second threshold is detected is extracted and extracted. For each updated column, a rectangle defined by the uppermost row coordinate and the lowermost row coordinate where a difference larger than the first threshold is detected, and the leftmost column coordinate and the rightmost column coordinate of the updated column is defined. It is characterized by performing the process of confirming as an update area Update region detection device according to Motomeko 4 or 5. A group of columns in which a difference greater than the first threshold is detected is a difference greater than the first threshold even if columns in which a difference greater than the first threshold is detected are adjacent or not directly adjacent to each other. 7. The update region detection apparatus according to claim 6 , wherein the update region detection apparatus is a group of columns adjacent to each other with a predetermined number of columns not detected. An upper end buffer for holding, for each column, row coordinates in which a difference greater than the first threshold is detected, and a lower end buffer for holding, in each column, row coordinates in which a difference greater than the first threshold is detected And a flag buffer that holds a flag indicating whether or not a difference larger than the second threshold is detected for each column,
The update region detection means compares the pixels of the previous frame and the current frame in the scan order, and when a pixel whose difference is larger than the first threshold is found, rewrites the row coordinates of the corresponding column in the upper end buffer and the lower end buffer, If the difference is larger than the second threshold, the flag in the corresponding column of the flag buffer is set, and the upper end buffer and the lower end buffer are set when a predetermined number of consecutive rows have not been detected. The update area detection apparatus according to claim 7 , wherein the process of determining an update area is performed with reference to the flag buffer. a) a moving area detecting means detecting, as a moving area, an image area which is the same or similar image area existing in both the previous frame and the current frame and whose position on the screen is changed;
b) the motion compensation means copying the movement area detected by the movement area detection means to the position after movement on the previous frame;
c) The update area detection area setting means determines the movement direction of the movement area detected by the movement area detection means, and if the determined movement direction includes a component from the top to the bottom of the screen, in addition to the lower end on the moving area, the screen is divided by the lower end of the movement region before the movement, the determined movement direction on the moving region after movement in the case of including a component directed from the bottom to the top of the screen In addition to the lower end , further dividing the screen by the upper end of the moving area before moving, and setting each divided area as an update area detection area that is a unit of processing for detecting the update area;
d) an update area detecting unit detecting, for each update area detection area set by the update area detection area setting unit, an area where the previous frame after copying is different from the current frame as an update area; An update area detection method characterized by the above. The update area detection area setting means determines whether or not the movement areas before and after the movement detected by the movement area detection means overlap, and does not perform the division when it is determined that there is no possibility of overlap. The update area detection method according to claim 9 , wherein the entire screen is set as an update area detection area. The update area detection area setting means determines whether or not a movement area is detected by the movement area detection means. If no movement area is detected, the entire screen is set as an update area detection area without performing the division. The update area detection method according to claim 9, wherein the update area detection method is set. The update area detection means compares the pixel values of pixels at the same position in the previous frame and the current frame, according to claim 9 or 11, characterized in that detecting the cluster of pixels with a difference in pixel value as an update region The update area | region detection method of any one of these. 13. The update area detection method according to claim 12 , wherein the update area detection means sets a rectangle circumscribing the pixel block as an update area. The update area detection means sequentially compares the pixels of the previous frame and the current frame one row at a time, and records, for each column, the upper row coordinates and the lower row coordinates where a difference larger than the first threshold is detected. In addition, it is recorded whether or not there is a pixel in which a difference greater than the second threshold is detected between the upper end and the lower end, and a row in which a difference greater than the first threshold is not detected continues for a predetermined number of rows. At that time, referring to the record, an update column including a group of columns in which a difference greater than the first threshold is detected and including a pixel in which a difference greater than the second threshold is detected is extracted and extracted. For each updated column, a rectangle defined by the uppermost row coordinate and the lowermost row coordinate where a difference larger than the first threshold is detected, and the leftmost column coordinate and the rightmost column coordinate of the updated column is defined. It is characterized by performing the process of confirming as an update area Update region detection method according to Motomeko 12 or 13. A group of columns in which a difference greater than the first threshold is detected is a difference greater than the first threshold even if columns in which a difference greater than the first threshold is detected are adjacent or not directly adjacent to each other. 15. The update region detection method according to claim 14 , wherein the update region detection method is a group of columns adjacent to each other with a predetermined number of columns not detected. An upper end buffer for holding, for each column, row coordinates in which a difference greater than the first threshold is detected, and a lower end buffer for holding, in each column, row coordinates in which a difference greater than the first threshold is detected And a flag buffer that holds a flag indicating whether or not a difference larger than the second threshold is detected for each column,
The update region detection means compares the pixels of the previous frame and the current frame in the scan order, and when a pixel whose difference is larger than the first threshold is found, rewrites the row coordinates of the corresponding column in the upper end buffer and the lower end buffer, If the difference is larger than the second threshold, the flag in the corresponding column of the flag buffer is set, and the upper end buffer and the lower end buffer are set when a predetermined number of consecutive rows have not been detected. The update area detection method according to claim 15 , wherein the process of determining an update area is performed with reference to the flag buffer. Computer
A moving area detecting means for detecting, as a moving area, an image area which is the same or similar image area existing in both the previous frame and the current frame and whose position on the screen is changed;
Motion compensation means for copying the movement area detected by the movement area detection means to a position after movement on the previous frame;
The mobile determines the moving direction of the detected moving region in the region detection means, in addition to the lower end on the moving region after movement when the movement direction which is the determination comprises a component directed from top to bottom of the screen the screen is divided by the lower end of the moving region before movement, when said determined movement direction includes a component directed from the bottom to the top of the screen in addition to the upper and lower ends of the moving region after movement, the movement before movement An update area detection area setting means for dividing the screen by the upper end of the area and setting each of the divided areas as an update area detection area that is a unit of processing for detecting the update area;
Update area detection for causing each update area detection area set by the update area detection area setting means to function as an update area detecting means for detecting an area where the previous frame after copying is different from the current frame as an update area program. The update area detection area setting means determines whether or not the movement areas before and after the movement detected by the movement area detection means overlap, and does not perform the division when it is determined that there is no possibility of overlap. The update area detection program according to claim 17 , wherein the entire screen is set as an update area detection area. The update area detection area setting means determines whether or not a movement area is detected by the movement area detection means. If no movement area is detected, the entire screen is set as an update area detection area without performing the division. 19. The update area detection program according to claim 17 , wherein the update area detection program is set. The update area detection means compares the pixel values of pixels at the same position in the previous frame and the current frame, according to claim 17 or 19, characterized in that detecting the cluster of pixels with a difference in pixel value as an update region The update area detection program according to any one of the above. 21. The update area detection program according to claim 20 , wherein the update area detection means sets a rectangle circumscribing the block of pixels as an update area. The update area detection means sequentially compares the pixels of the previous frame and the current frame one row at a time, and records, for each column, the upper row coordinates and the lower row coordinates where a difference larger than the first threshold is detected. In addition, it is recorded whether or not there is a pixel in which a difference greater than the second threshold is detected between the upper end and the lower end, and a row in which a difference greater than the first threshold is not detected continues for a predetermined number of rows. At that time, referring to the record, an update column including a group of columns in which a difference greater than the first threshold is detected and including a pixel in which a difference greater than the second threshold is detected is extracted and extracted. For each updated column, a rectangle defined by the uppermost row coordinate and the lowermost row coordinate where a difference larger than the first threshold is detected, and the leftmost column coordinate and the rightmost column coordinate of the updated column is defined. It is characterized by performing the process of confirming as an update area Update region detection program according to Motomeko 20 or 21. A group of columns in which a difference greater than the first threshold is detected is a difference greater than the first threshold even if columns in which a difference greater than the first threshold is detected are adjacent or not directly adjacent to each other. 23. The update region detection program according to claim 22 , wherein the update region detection program is a group of columns adjacent to each other with a predetermined number of columns not detected. The computer holds, for each column, an upper end buffer for holding, for each column, a row coordinate in which a difference greater than a first threshold is detected, and a row coordinate in which a difference greater than the first threshold is detected for each column. And a flag buffer that holds, for each column, a flag indicating whether or not a difference larger than the second threshold is detected,
The update region detection means compares the pixels of the previous frame and the current frame in the scan order, and when a pixel whose difference is larger than the first threshold is found, rewrites the row coordinates of the corresponding column in the upper end buffer and the lower end buffer, If the difference is larger than the second threshold, the flag in the corresponding column of the flag buffer is set, and the upper end buffer and the lower end buffer are set when a predetermined number of consecutive rows have not been detected. 24. The update region detection program according to claim 23 , wherein the processing for determining an update region is performed with reference to the flag buffer. A video signal encoding apparatus comprising: an area encoding unit that encodes an update area detected by the update area detection apparatus according to any one of claims 1 to 8 as an image.