Patent Publication Number: US-6665340-B1

Title: Moving picture encoding/decoding system, moving picture encoding/decoding apparatus, moving picture encoding/decoding method, and recording medium

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an image processing system and, more particularly, to a moving picture encoding/decoding system, moving picture encoding/decoding apparatus, moving picture encoding/decoding method, recording medium on which a moving picture encoding/decoding program is recorded, recording medium on which a moving picture encoding program is recorded, and recording medium on which a moving picture decoding program is recorded. 
     In recent years, moving picture encoding extensively uses a moving picture encoding means in units of objects. The MPEG (Moving Picture Experts Group)-4, which is being standardized in ISO/IEC, also adopts encoding in units of objects. In this method, an image object (to be simply referred to as an “object”) serving as a component of an image is encoded together with shape information representing the contour, and these objects are synthesized by a decoder, thereby reconstructing a target encoded image. 
     To encode an object with an arbitrary shape, a rectangular region including the object is set as a target encoding region, to which a conventional encoding method to a rectangular moving picture is applied. 
     However, when the target encoding region is encoded using “0” as a pixel value outside the object, the pixel prediction residual component on the object boundary increases along with inter-frame prediction to greatly decrease the prediction efficiency and encoding efficiency. 
     To solve this problem, a method called “padding” is used. According to this method, the target encoding region is encoded as a rectangular region after a pixel value near the boundary is substituted around the object. In synthesizing the object by the decoder, pixels outside the object are masked using shape information. 
     FIG. 14 shows the arrangement of a conventional moving picture encoding apparatus used in the ISO/IEC 14496-2 MPEG-4. 
     Referring to FIG. 14, an input image encoding means  103  encodes a rectangular input image  1000 . A first storage means  101  stores a target padding image signal  1001  transferred from the input image encoding means  103 . A second storage means  102  stores shape information  1002 . 
     A padding means  100  transfers to the second storage means  102  an address  1005  representing a pixel position in the shape information stored in the second storage means  102 , reads out the shape information  1002  stored in the second storage means  102 , and identifies a pixel outside the object in the image signal stored in the first storage means  101 . 
     The padding means  100  transfers to the first storage means  101  an address  1007  representing the pixel position outside the object in the image signal, refers to an image signal  1008  stored in the first storage means  101 , calculates a pixel value to be substituted into the address  1007 , and substitutes the pixel value into the address  1007 . 
     Padding processing in the padding means  100  is realized by executing padding processing for a one-dimensional pixel string twice. FIG. 15 shows a region to be padded within the target encoding region. In a target encoding region  40 , an object-including pixel string set  42  outside an object  41  is horizontally padded. Then, a region  43  not included in the pixel string set  42  is vertically padded. 
     By this processing, the input image encoding means  103  encodes the input image  1000  based on an image signal  1009  filled with proper pixel values outside the object. A shape information encoding means  104  encodes the shape information  1002 . Encoded image data  1010  is transferred or stored together with encoded shape information  1003 . 
     The image signal  1001  to be padded includes an input image signal transferred from the input image encoding means  103 , and a reference image which is generated inside the input image encoding means  103  and used for inter-frame prediction. When the encoding apparatus pads the reference image used for inter-frame prediction, the decoding apparatus must also pad the reference image. 
     In identifying the object boundary in padding processing, the conventional moving picture encoding apparatus searches for all the pixels of the target encoding region twice regardless of the object shape. This results in a large arithmetic amount. 
     For the same reason, the moving picture decoding apparatus for performing padding processing also suffers a large arithmetic amount. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a moving picture encoding/decoding system, moving picture encoding/decoding apparatus, moving picture encoding/decoding method, and recording medium capable of reducing the arithmetic amount and increasing the processing speed. 
     To achieve the above object, according to the present invention, there is provided a moving picture encoding/decoding system comprising a moving picture encoding apparatus and a moving picture decoding apparatus, the moving picture encoding apparatus having input image encoding means for encoding an input image signal including an image object, first storage means for storing the image signal including the image object to be padded in the input image encoding means, and transferring the image signal to the input image encoding means if necessary, shape information encoding means for encoding shape information representing a shape of the image object to generate encoded shape information, and generating boundary information representing a boundary position of the image object, second storage means for storing the boundary information, and padding means for identifying an outer region of the image object in the image signal stored in the first storage means on the basis of the boundary information stored in the second storage means, calculating a pixel value to be substituted into the outer region, and substituting the pixel value into the region stored in the first storage means, and the moving picture decoding apparatus having image decoding means for referring to a reference image, and decoding encoded image data including an image object to generate an image signal, first storage means for storing the decoded image signal and supplying the decoded image signal as a reference image in next frame decoding processing to the image decoding means, shape information decoding means for decoding encoded shape information serving as encoded data of image object shape information to generate shape information, and generating boundary information representing a boundary position of the image object, second storage means for storing the boundary information, and padding means for identifying an outer region of the image object in the image signal stored in the first storage means on the basis of the boundary information stored in the second storage means, calculating a pixel value to be substituted into the outer region, and substituting the pixel value into the region stored in the first storage means. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram showing the arrangement of a moving picture encoding apparatus in the first embodiment of the present invention; 
     FIG. 2 is a block diagram showing the arrangement of a shape information encoding means in the first embodiment of the present invention; 
     FIG. 3 is a block diagram showing the arrangement of a padding means in the first embodiment of the present invention; 
     FIG. 4 is a flow chart showing operation of the padding means in the first embodiment of the present invention; 
     FIG. 5 is a flow chart showing padding region identification means in FIG. 4 in detail; 
     FIG. 6 is a flow chart showing horizontal padding value substitution processing in FIG. 4 in detail; 
     FIG. 7 is a flow chart showing operation of the padding means in the second embodiment of the present invention; 
     FIG. 8 is a flow chart showing vertical padding value substitution processing in FIG. 7 in detail; 
     FIG. 9 is a block diagram showing the arrangement of a moving picture decoding apparatus in the third embodiment of the present invention; 
     FIG. 10 is a block diagram showing the arrangement of a shape information decoding means in the third embodiment of the present invention; 
     FIG. 11 is a view showing an example of block classification information; 
     FIG. 12 is a view showing the coordinate system in the target encoding region; 
     FIG. 13 is a view showing an example of the search section and padding region in a horizontal pixel string; 
     FIG. 14 is a block diagram showing the arrangement of a conventional moving picture encoding apparatus for performing padding processing; and 
     FIG. 15 is a view showing an example of a padding region corresponding to an image object. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. 
     First Embodiment 
     FIG. 1 shows the arrangement of a moving picture encoding apparatus according to the first embodiment of the present invention. The moving picture encoding apparatus in FIG. 1 comprises an input image encoding means  103  for encoding an input image signal  1000  including an image object, a first storage means  101  for storing the image signal including the image object to be padded in the input image encoding means  103 , and transferring the image signal to the input image encoding means  103  if necessary, a shape information encoding means  104  for encoding shape information  1002  representing the shape of the image object to generate encoded shape information  1003 , and generating boundary information  1004  representing the boundary position of the image object, a second storage means  102  for storing the boundary information, and a padding means  105  for identifying the outer region of the image object in the image signal stored in the first storage means  101  on the basis of the boundary information stored in the second storage means  102 , calculating a pixel value to be substituted into the outer region, and substituting the pixel value into the region stored in the first storage means  101 . 
     In the following description, the present invention is applied to padding processing for a reference image used for inter-frame prediction. Also when moving picture encoding processing is done after padding an input image signal, the same padding processing as the first embodiment can be applied. 
     The input image encoding means  103  encodes the input image signal  1000  to generate encoded image data  1010 . The input image encoding means  103  generates an image signal  1001  representing the decoded image of the current frame, and stores the image signal  1001  in the first storage means  101 . In encoding the next frame, the input image encoding means  103  refers to the image signal  1001  as a reference image  1009  to perform inter-frame prediction. 
     The shape information encoding means  104  encodes the shape information  1002  representing the shape of the image object in the input image signal  1000 , thereby generating the encoded shape information  1003 . At the same time, the shape information encoding means  104  transfers to the second storage means  102  the boundary information  1004  representing the boundary position of the object within the target encoding region. 
     The padding means  105  designates an address  1005  in order to switch boundary information referred to in each processing stage, and receives corresponding boundary information  1006  from the second storage means  102 . The padding means  105  refers to the boundary information  1006  to identify an outer region outside the object in the image signal stored in the first storage means  101 , calculates a padding value as a pixel value to be substituted into the region, and substitutes the padding value into the region in the image signal of the first storage means  101 . 
     The padding means  105  transfers to the first storage means  101  an address  1007  representing the position of a pixel referred to in padding value calculation, or the position of a pixel to be substituted. The padding means  105  reads out and writes a pixel value  1008 . 
     FIG. 2 shows the arrangement of the shape information encoding means  104  for outputting encoded shape information defined in the ISO/IEC 14496-2 MPEG-4. The shape information encoding means  104  in FIG. 2 comprises a block segmenting unit  106  for segmenting the shape information  1002  into a plurality of blocks, a block determination unit  107  for referring to segmented block shape information  1011  to generate block classification information  1012  representing whether the block is outside or inside the image object or on the boundary, a block shape information encoding unit  108  for referring to the block classification information  1012 , and when the block is on the boundary of the image object, encoding the block shape information  1011 , and a multiplexing unit  109  for multiplexing the block classification information  1012  and encoded block shape information  1013  to generate the encoded shape information  1003 . The block classification information  1012  and block shape information  1011  are transferred as the boundary information  1004  to the second storage means  102 . 
     The block segmenting unit  106  segments the shape information  1002  into a plurality of block shape information  1011  in accordance with a plurality of blocks prepared by dividing the target encoding region. The block segmenting unit  106  sends the block shape information  1011  to the block determination unit  107 . 
     The block determination unit  107  refers to each block shape information  1011  to generate block classification information  1012  representing whether the block is inside or outside the image object or on the object boundary. 
     The block shape information encoding unit  108  refers to the block classification information  1012 , and when the block is on the boundary of the image object, encodes the block shape information  1011  to generate the encoded block shape information  1013 . 
     The multiplexing unit  109  multiplexes the block classification information  1012  and encoded block shape information  1013  into the encoded shape information  1003 . 
     The block classification information  1012  and block shape information  1011  are transferred as the boundary information  1004  to the second storage means  102 . 
     When the target encoding region is a rectangle with a width W and height H, and the segmented block is a square with a side B, the block classification information is given by a matrix of the width W/B and height H/B, as shown in FIG.  11 . 
     In FIG. 11, a block hatched from the upper right end of the block to the lower left end, a white block, and a block hatched from the upper left end of the block to the lower right end are respectively a block outside an image object  41 , a block inside the image object  41 , and a block on the boundary of the image object  41 . 
     FIG. 3 shows the arrangement of the padding means  105 . The padding means  105  in FIG. 3 comprises an address calculation unit  110  for referring to the block classification information stored in the second storage means  102 , and only when the block is on the boundary of the image object, referring to the block shape information stored in the second storage means  102  to calculate an address  1014  representing a pixel position in the outer region from the block classification information and block shape information, and a padding value substitution unit  111  for referring to the image signal stored in the first storage means  101  to calculate a pixel value corresponding to the address  1014 , and substituting the pixel value into the address in the image signal stored in the first storage means  101 . 
     FIG. 4 shows operation of the padding means  105 . Operation of the padding means  105  will be explained with reference to FIGS. 1,  3 , and  4 . 
     The address calculation unit  110  starts referring to the boundary information  1006  (block classification information  1012 ) stored in the second storage means  102  using the upper left end of the target encoding region as a start position (step  201 ). 
     The address calculation unit  110  determines based on the block classification information  1012  whether the block is on the boundary of the image object (step  202 ). If YES in step  202 , the address calculation unit  110  reads out corresponding boundary information  1006  (block shape information  1011 ), and identifies a padding region to be padded (step  203 ). The padding value substitution unit  111  performs padding value substitution processing to a horizontal pixel string (step  204 ). 
     The processing from steps  202  to  204  is repeated till the completion of search for the block classification information (step  205 ). 
     After that, the address calculation unit  110  restarts calculating addresses from the left end of the target encoding region as a start position (step  206 ). The padding value substitution unit  111  performs padding value substitution processing to a vertical pixel string (step  207 ). 
     The padding value substitution position is updated (step  208 ), and vertical padding processing (step  207 ) is repeated until the target pixel string reaches the right end of the target encoding region (step  209 ). 
     Padding processing will be sequentially explained. 
     FIG. 5 shows padding region identification processing (step  203 ) in FIG. 4 in detail. In FIG. 5, Y and Y′ respectively represent the y-coordinate at the upper left end point of the block on the boundary, and the y-coordinate at the upper left end point of a previously referred block. FIG. 12 shows the coordinates in the target encoding region. The upper left end point of the target encoding region is defined as the origin, and the horizontal and vertical directions are respectively defined as x- and y-axes. 
     The address calculation unit  110  comprises B registers  0  to B−1 in order to store the left end point of an identified padding region, and the registers  0  to B−1 store corresponding pixel coordinates. Coordinates (xi, yi) are stored in the register i. Further, the address calculation unit  110  incorporates a memory for storing the y-coordinate representing a padding region subjected to vertical padding processing. 
     The address calculation unit  110  refers to the boundary information  1006  (block classification information  1012 ) to determine Y and compare it with Y′ (step  210 ). 
     If Y=Y′, the address calculation unit  110  searches for boundary information  1006  (block shape information  1011 ) corresponding to the block for each pixel, and identifies coordinates at the right and left ends of the padding region. A pixel outside the object that is adjacent to a right pixel inside the object is defined as the right end of the padding region, and a pixel outside the object that is adjacent to a left pixel inside the object is defined as the left end of the padding region. 
     If the coordinates (x, y) indicate the left end point (YES in step  211 ), the address calculation unit  110  stores the coordinates (x, y) in a corresponding register y-Y (step  212 ). 
     If the coordinates (x, y) indicate the right end point (NO in step  211 ), the address calculation unit  110  checks whether the register y-Y stores a corresponding left end point (step  213 ). 
     If the register y-Y stores the coordinates, the address calculation unit  110  sets a region from (xi, yi) to (x, y) subject to i=y-Y as a padding region, calculates corresponding addresses  1014  in the image signal stored in the storage means  101 , and transfers the addresses  1014  to the padding value substitution unit  111  (step  214 ). 
     Note that, at this time, yi=y. Then, the address calculation unit  110  resets the register y-Y (step  215 ). 
     If the register y-Y does not store the coordinates, the address calculation unit  110  sets a region from the left end coordinates ( 0 , y) of the target encoding region to (x, y) as a padding region, calculates corresponding addresses  1014 , and transfers them to the padding value substitution unit  111  (step  216 ). 
     If the Y&gt;Y′ in step  210 , the address calculation unit  110  checks whether coordinates are stored in each register before step  211  (step  218 ). 
     If coordinates are stored in the register i (NO in step  218 ), the address calculation unit  110  sets a region from (xi, yi) to the right end coordinates (W, yi) of the target encoding region as a padding region, calculates corresponding addresses  1014 , transfers them to the padding value substitution unit  111  (step  219 ), and resets the register i (step  220 ). 
     If no coordinates are stored in the register i (YES in step  215 ), this means that a pixel string having a y-coordinate of (Y′+i) does not include any pixel inside the image object. 
     The address calculation unit  110  sets and stores a region from the y-coordinate of Y′+i as a vertical padding region in the internal memory (step  221 ). 
     The address calculation unit  110  repeats the above processing from the register  0  (step  217 ) to the register B−1 (steps  222  and  223 ). 
     The address calculation unit  110  checks whether Y is larger than Y′+B (step  224 ). If Y&gt;Y′+B, this means that image strings not including the object successively exist between the lower end of a block having immediately undergone padding region identification processing and the upper end of a block undergoing padding region identification processing. The address calculation unit  110  sets a region from a y-coordinate of Y′+B+1 to Y−1 as a vertical padding region, and stores these y-coordinates in the internal memory (step  225 ). 
     FIG. 6 shows horizontal padding value substitution processing (step  204 ) in FIG. 4 in detail. Although padding value substitution processing shown in FIG. 6 is described in the ISO/IEC 14496-2 MPEG-4, the present invention can also be applied to another padding value substitution processing. 
     If the left end point of the padding region is the left end point of the target encoding region (YES in step  230 ), the padding value subtraction unit  111  sets a pixel value  1008  immediately adjacent to the right end of the padding region as a padding value, and substitutes this padding value into a corresponding position in the image signal stored in the first storage means  101  (step  233 ). 
     If the right end point of the padding region is the right end point of the target encoding region (YES in step  231 ), the padding value subtraction unit  111  sets a pixel value  1008  immediately adjacent to the left end of the padding region as a padding value, and substitutes this padding value into a corresponding position in the image signal stored in the first storage means  101  (step  235 ). 
     If neither the two end points of the padding region are the end points of the target encoding region (NO in step  231 ), the padding value subtraction unit  111  sets the average of the pixel values  1008  respectively immediately adjacent to the right and left ends of the padding region as padding values, and substitutes these padding values into corresponding positions in the image signal stored in the first storage means  101  (step  234 ). 
     The search section, padding region, and padding value in the horizontal pixel string will be explained with reference to an example shown in FIG.  13 . 
     A polygonal line  41  in FIG. 13 represents the boundary of the image object. In FIG. 13, blocks aligned in the lateral direction represent block classification information, and hatched blocks are on the object boundary. Points  400  and  409  indicate the left and right ends of the pixel string in the target encoding region. In this example, padding processing of a pixel string from the pixels  400  to  409  will be described. On this pixel string, search targets are regions inside boundary blocks, i.e., a section from the pixels  401  to  404  and a section from the pixels  405  to  408 . The pixels  402 ,  403 ,  406 , and  407  serving as the end points of these padding regions are identified by the above-described search processing. From the above operation, the pixel value of the pixel  402 , the average of the pixel values of the pixels  403  and  406 , and the pixel value of the pixel  407  are respectively substituted as padding values into the padding region from the pixels  400  to  402 , the padding region from the pixels  403  to  406 , and the padding region from the pixels  407  to  409 . 
     Referring back to FIG. 4, after padding region identification processing and horizontal padding value substitution processing are completed, the address calculation unit  110  defines the left end of the target encoding region as the start position of vertical padding processing (step  206 ). 
     The padding value subtraction unit  111  performs padding value substitution processing of sequentially substituting the values of adjacent pixels padded in units of vertical pixel strings (step  207 ). Padding processing for each vertical pixel string is the same as horizontal padding value substitution processing shown in FIG. 6 except that the padding directions are different from each other, and a description thereof will be omitted. 
     In the first embodiment, the encoded shape information  1003  output from the shape information encoding means  104  is made up of the block classification information and encoded block shape information. The present invention is also applied to another shape information encoding method using the outline of the object, e.g., a method of expressing the outline of the image object with a simple geometric figure. 
     When shape information encoding does not use any outline information, the shape information encoding means  104  newly comprises a means for identifying a block position on the object boundary at the same time as encoding the shape, and transfers the identified boundary information  1004  to the second storage means  102 . Even this arrangement can implement the present invention. 
     In the first embodiment, the entire region of the target encoding region outside the image object undergoes padding processing. The present invention can also be applied when the padding region is limited within a motion vector detection range in motion-compensated inter-frame prediction encoding. In this case, if an identified padding region exceeds the detection range, only a block within the detection range from the object boundary undergoes padding value substitution processing. 
     As described above, the present invention can reduce the arithmetic amount and increase the processing speed by limiting the pixel search region in padding processing. This is because the present invention uses boundary information obtained by shape information encoding and omits search for a block not on the boundary of the image object. 
     In conventional padding processing, all the pixels in the target encoding region are searched twice, as described above. To the contrary, in the present invention, pixels are searched only in blocks on the object boundary, e.g., blocks hatched from the upper left end to the lower right end in FIG.  11 . 
     In processing necessary for reducing pixel search, outline information of the image object is obtained by shape information encoding without requiring any additional arithmetic amount, and search for the outline information only spends a smaller arithmetic amount than search for the pixel in the target encoding region. Therefore, the present invention can remarkably reduce the arithmetic amount. 
     Second Embodiment 
     The second embodiment of the present invention will be described. In the second embodiment, a moving picture encoding apparatus has the same arrangement as in the first embodiment except for processing in a padding means  105 . FIG. 7 shows operation of the padding means  105  in the second embodiment of the present invention. The same reference numerals as in FIG. 4 denote the same parts. 
     The first embodiment applies horizontal padding value substitution processing to the vertical one except for the direction. However, the second embodiment adopts different padding processing from the horizontal one (step  238 ). FIG. 8 shows vertical padding value substitution processing in detail. 
     A padding value subtraction unit  111  refers to an address  1014  transferred from an address calculation unit  110 , and copies pixel strings to a vertical padding region one by one, thereby achieving padding value substitution processing. 
     If the upper end of the padding region is the upper end of the target encoding region (YES in step  240 ), the padding value subtraction unit  111  copies a pixel string below the lower end of the padding region to respective pixel strings in the padding region (step  243 ). 
     If the lower end of the padding region is the lower end of the target encoding region (YES in step  241 ), the padding value subtraction unit  111  copies a pixel string above the upper end of the padding region to respective pixel strings in the padding region (step  245 ). 
     If neither the two ends of the padding region are the boundary of the target encoding region (NO in step  241 ), the padding value subtraction unit  111  averages pixels having the same x-coordinate from a pixel string above the upper end of the padding region and a pixel string below the lower end of the padding region, and copies the newly generated pixel string to pixel strings in the padding region (step  244 ). 
     The second embodiment of the present invention can copy pixel values successively stored in the memory to another memory space, and can further increase the processing speed. 
     Third Embodiment 
     FIG. 9 shows the arrangement of a moving picture decoding apparatus in the third embodiment of the present invention. The moving picture decoding apparatus in FIG. 9 comprises an image decoding means  112  for referring to a reference image, and decoding encoded image data  1100  including an image object into an image signal  1102 , a first storage means  101  for storing the decoded image signal and supplying it as a reference image in next frame decoding processing to the image decoding means, a shape information decoding means  113  for decoding encoded shape information  1101  serving as encoded data of image object shape information to generate shape information  1103 , and generating boundary information  1004  representing the boundary position of the image object, a second storage means  102  for storing the boundary information, and a padding means  105  for identifying the outer region of the image object in the image signal stored in the first storage means  101  on the basis of the boundary information stored in the second storage means  102 , calculating a pixel value to be substituted into the outer region, and substituting the pixel value into the region stored in the first storage means  101 . 
     The moving picture decoding apparatus comprises the image decoding means  112  and shape information decoding means  113  in place of the input image encoding means  103  and shape information encoding means  104  in the moving picture encoding apparatus shown in FIG.  1 . 
     The image decoding means  112  decodes the encoded image data  1100  to generate the output image signal  1102 . The output image signal  1102  has a target encoding region represented by a rectangular outer frame, and includes an image object with an arbitrary shape. 
     The image decoding means  112  stores the output image signal of the current frame in the first storage means  101 . The image decoding means  112  uses this image signal as a reference image  1009  for inter-frame prediction in decoding the next frame. 
     The shape information decoding means  113  decodes the encoded shape information  1101  to output the shape information  1103  of the image object, and stores the boundary information  1004  in the second storage means  102 . 
     The padding means  105  sends a read request  1005  to the second storage means  102  every processing unit for padding processing, and receives boundary information  1006  from the storage means  102 . 
     The padding means  105  refers to the boundary information  1006  to calculate addresses  1007  representing a region outside the image object in the image signal stored in the first storage means  101 , and refers to an image signal  1001  stored in the first storage means  101  to calculate a pixel value  1008  to be substituted into the region, and substitutes the pixel value  1008  to the region in the first storage means  101 . 
     Detailed processing in the padding means  105  is the same as in the padding means  105  of the first or second embodiment, and a description thereof will be omitted. 
     FIG. 10 shows the arrangement of the shape information decoding means  113 . A demultiplexing unit  114  demultiplexes the encoded shape information  1101  into block classification information  1106  and encoded block shape information  1104 . 
     A block shape information decoding unit  115  decodes the encoded block shape information  1104  to generate block shape information  1105 . 
     A shape information integrating unit  116  refers to the block classification information  1106  and block shape information  1105  to generate the shape information  1103  of the entire image object. 
     The block classification information  1106  and block shape information  1105  are transferred as the boundary information  1004  to the second storage means  102 . 
     In this way, the moving picture decoding apparatus can attain the same effects as the moving picture encoding apparatus of the first embodiment. 
     In the third embodiment, the entire region of the target encoding region outside the image object undergoes padding processing. The present invention can also be applied when the padding region is limited within a motion vector detection range in motion-compensated inter-frame prediction encoding. In this case, if an identified padding region exceeds the detection range, only a block within the detection range from the object boundary undergoes padding value substitution processing. 
     The third embodiment may adopt the padding means  105  described in the second embodiment. 
     Fourth Embodiment 
     The above-described moving picture encoding apparatus can be realized by a computer. In this case, a moving picture encoding program for realizing the moving picture encoding method of the present invention is loaded from a recording medium such as a flexible disk, CD-ROM, or memory card on which this program is recorded to the memory of a computer (the computer may be a digital signal processor for image processing). By executing this program, the moving picture encoding apparatus can be realized. 
     Similarly, the moving picture decoding apparatus can be realized by a computer. In this case, a moving picture decoding program for realizing the moving picture decoding method of the present invention is loaded from a recording medium on which this program is recorded to the memory of the computer. By executing this program, the moving picture decoding apparatus can be realized.