Moving image coder and moving image decoder

Video coding equipment and a video decoding device

0001The present invention relates to video coding equipment and a video decoding device provided with a motion compensation function.

0002As an encoding method of video data, coding between motion compensation prediction frames is known. In coding between motion compensation prediction frames, the motion vector showing a "motion" of an inter-frame image element is detected in coding equipment. using the detected motion vector, the picture of an original frame is predicted from the frame of the past and the future or -- from the past frame, and the difference of an actual picture and a prediction picture is detected. And motion vector information and its difference value information are transmitted. A decoding device reproduces video using motion vector information and difference value information.

0003In coding between motion compensation prediction frames, once an error occurs, the error will spread on a following frame. For this reason, in coding between motion compensation prediction frames, the coding picture in a frame is usually inserted periodically. Here, the coding picture in a frame is coded independently of other frames. Therefore, even if an error occurs, spreading of the error on the frame after the coding picture in a frame is lost.

0004However, the coding picture in a frame has the sharply large amount of information compared with an inter-frame coding picture. For this reason, if the coding picture in a frame is inserted periodically, the peak value of traffic will become high. And in order to guarantee this traffic, it is necessary to enlarge buffer size.

0005As one of the art which solves this problem, the encoding method called refreshment one by one is proposed. It explains, while referring to Drawing 1 for a refreshment method one by one. "Refreshment" means performing the coding in a frame. Each frame shall be constituted from four fields 501-504 by the following explanation.

0006As shown in Drawing 1, in the n-th frame, the picture of field 501 is coded by the coding in a frame, and the picture of fields 502-504 is coded by inter-frame coding. Then, in the n+1st frame, the picture of field 502 is coded by the coding in a frame, and the picture of fields 501, 503, and 504 is coded by inter-frame coding. Similarly, in the n+2nd frame, the picture of field 503 is coded by the coding in a frame, and the picture of field 504 is coded by the coding in a frame in the n+3rd frame. Thus, in the example shown in Drawing 1, all the fields are refreshed by making four frames into a cycle. The refreshment method is indicated in patent documents 1 - patent documents 3 one by one, for example.<patcit num="1"><text>JP,2003-179938,A</text></patcit><patcit num="2"><text>JP,6-113286,A</text></patcit><patcit num="3"><text>JP,2005-260936,A</text></patcit>

0007By the way, in the coding between motion compensation prediction frames which introduced the refreshment method one by one, in order to suppress propagation of errors or to realize a "head broth regenerative function", it is necessary to restrict the field which can be referred to for a motion compensation. Hereinafter, restriction of a reference field is explained, referring to Drawing 2 - Drawing 4. In Drawing 2 - Drawing 4, fields 501, 502, 503, and 504 shall be refreshed in order like Drawing 1 in the n-th frame, the n+1st frame, the n+2nd frame, and the n+3rd frame, respectively. In this case, in the n-th frame, refreshment has not completed fields 502-504. That is, fields 502-504 are refreshment uncompleted fields. In the n+1st frame, refreshment of field 501 is completed and refreshment of fields 503-504 has not been completed. Similarly, in the n+2nd frame, fields 501-502 are the completion fields of refreshment, and field 504 is refreshment an uncompleted field. In the n+3rd frame, fields 501-503 are the completion fields of refreshment.

0008When coding a picture by inter-frame coding, the picture of a front frame is referred to, for example. Here, when coding the picture of refreshment an uncompleted field, the picture of arbitrary fields can be referred to. That is, references 511 and 512 are allowed in Drawing 2. However, in order to suppress propagation of errors, when coding the picture of the completion field of refreshment, the picture of refreshment an uncompleted field cannot be referred to. That is, in Drawing 2, although references 513 and 514 are allowed, reference 515 is not allowed.

0009Also in order to realize "head broth reproduction" of video, when coding the picture of the completion field of refreshment, the picture of refreshment an uncompleted field cannot be referred to. For example, refer to the picture of a refreshment field or the completion field of refreshment for each in the example shown in Drawing 3 (references 521-523). Therefore, reproduction of video can be started from the n+3rd frame in this case. On the other hand, in the example shown in Drawing 4, when coding the picture of the completion field of refreshment, the picture of the refreshment uncompleted field is referred to (reference 524). In this case, since the n+1st frame cannot be decrypted, the n+2nd frame and the n+3rd frame are also unreproducible as a result. That is, reproduction of video cannot be started from the n+3rd frame.

0010Drawing 5 is a figure explaining the issue which should be solved in a refreshment method one by one. Here, with reference to the picture of the n-th frame, the picture of the n+1st-frame block A shall be coded. Block B and block C shall be detected as a candidate of the picture which block A should refer to. Here, block B does not contain the picture of the refreshment uncompleted field. On the other hand, block C contains the picture of the refreshment uncompleted field.

0011He is trying to suppress propagation of errors by forbidding reference of block C in such a situation according to conventional technology (for example, art given in patent documents 1). However, if coding/decryption is performed in conventional technology as a picture which should be referred to for the motion compensation of block A using the picture of block B when the picture of block C is more preferred than the picture of B of a block, a picture will deteriorate.

0012Thus, in the conventional coding between motion compensation prediction frames, when refreshment was introduced one by one, there was a possibility that a picture might deteriorate. That is, in the conventional coding between motion compensation prediction frames, it was difficult to realize control of the peak of the amount of information, and the both sides of good picture quality.

0013In coding between motion compensation prediction frames, an object of the present invention while controlling the peak of the amount of information is to obtain good picture quality. The video coding equipment of the present invention is composition which codes about each of a plurality of blocks obtained by dividing an input picture, The definition means which defines the effective field which can be referred to in the reference picture of inter-frame coding, A detection means to detect the reference field which should be referred to in the above-mentioned reference picture for inter-frame coding of an object block, The picture of the reference field is outputted about the above-mentioned reference field belonging to the above-mentioned effective field, and a complement picture is outputted about the above-mentioned reference field which does not belong to the above-mentioned effective field, It has a prediction picture generation means which generates the prediction picture for inter-frame coding, and an encoding means which codes an input picture using the above-mentioned prediction picture.

0014In the video coding equipment of the above-mentioned composition, when the reference field for inter-frame coding contains the pixel outside an effective field and a prediction picture is created, a complement picture is used instead of the picture outside the effective field. Therefore, propagation of errors is controlled.

0015It may be made for a prediction picture generation means to be provided with a complement means to generate a complement picture based on the pixel in an effective field. In this case, it may be made for a complement means to generate the above-mentioned complement picture with the complementing method selected from a plurality of complementing methods currently prepared beforehand.

0016The video decoding device of the present invention is composition which decrypts the coding data obtained by the video coding equipment which codes about each of a plurality of blocks obtained by dividing an input picture, The acquisition means which acquires the effective field information which defined the effective field which can be referred to in the reference picture of inter-frame coding, A detection means to detect the reference field which should be referred to in the above-mentioned reference picture for inter-frame coding of an object block, The picture of the reference field is outputted about the above-mentioned reference field belonging to the above-mentioned effective field, and a complement picture is outputted about the above-mentioned reference field which does not belong to the above-mentioned effective field, It has a prediction picture generation means which generates the prediction picture for inter-frame coding, and a decoding means which decrypts the above-mentioned coding data using the above-mentioned prediction picture.

0017According to the present invention, good picture quality can be obtained in coding between motion compensation prediction frames, controlling the peak of the amount of information.

0018<figref num="1">It is a figure which illustrates a refreshment method one by one.</figref><figref num="2">It is a figure explaining restriction of a reference field.</figref><figref num="3">It is a figure explaining the head broth of video.</figref><figref num="4">It is a figure explaining the problem concerning the head broth of video.</figref><figref num="5">It is a figure explaining the issue which should be solved in a refreshment method one by one.</figref><figref num="6">It is a figure showing the composition of the video coding equipment of the embodiment of the present invention.</figref><figref num="7">It is a figure showing the composition of the prediction image generation part with which video coding equipment is provided.</figref><figref num="8">It is a figure explaining detection of a reference field.</figref><figref num="9">It is a figure explaining effective field information.</figref><figref num="10">It is a figure (the 1) explaining operation of a prediction image generation part.</figref><figref num="11">It is a figure (the 2) explaining operation of a prediction image generation part.</figref><figref num="12">It is a figure explaining the 1st complementing method.</figref><figref num="13">It is a figure explaining the 2nd complementing method.</figref><figref num="14">It is a figure explaining the 3rd complementing method.</figref><figref num="15">It is a figure showing the composition of a prediction image generation part provided with the function which chooses a complementing method.</figref><figref num="16">It is a figure showing the composition of a complement section provided with the function which chooses a complementing method.</figref><figref num="17">It is a figure explaining the notifying method of an effective field / un-effective field.</figref><figref num="18">It is a figure showing the composition of the video decoding device of the embodiment of the present invention.</figref><figref num="19">It is a figure explaining the composition and operation of an embodiment of a prediction image generation part with which a video decoding device is provided.</figref>

0019Drawing 6 is a figure showing the composition of the video coding equipment of the embodiment of the present invention. This video coding equipment 100 codes video data about each of a plurality of blocks obtained by dividing a picture using motion compensation prediction. In inter-frame coding, the sequential refreshment method explained while referring to Drawing 1 is adopted. Inter-frame coding may be forward direction prediction, and may be bidirectional prediction.

0020For every (every [ or ] block which constitutes a frame) frame, prediction error signal generating part 1 computes the difference of an original picture image and a prediction picture, and outputs it as a prediction error signal. A prediction picture is explained later. Orthogonal transformation section 2 performs rectangular conversion about a prediction error signal. Rectangular conversion is DCT conversion in this example, for example. In DCT conversion, each pixel value is changed into a frequency component, and the coefficient data showing each frequency component is generated. Quantizing part 3 quantizes the output signal (this example coefficient data) of orthogonal transformation section 3. Coefficient coding part 4 performs entropy coding to the quantized coefficient data. Multiplexing part 5 multiplexes the coded coefficient data, the coded motion vector information, and the coded control data, and transmits. Control data is explained later.

0021The data outputted from multiplexing part 5 is transmitted to a decoding device via a network, for example. Or the data outputted from multiplexing part 5 is written in a recorder. Although a multiplexing scheme in particular is not limited, it is TDM, for example.

0022Inverse quantization part 6 and reverse orthogonal transformation section 7 perform the conversion process corresponding to quantizing part 3 and orthogonal transformation section 2, respectively, and reproduce a prediction error signal. Decoding image generation part 8 generates a decoding image based on the prediction error signal and prediction image which were reproduced. This decoding image is an image which will be obtained in the decoding device.

0023Decoding image storage section 11 is semiconductor memory, for example. A decoding image generated by decoding image generation part 8 is stored temporarily. At this time, after a decoding image is removed by digital blocking filter 12 in block distortion, it may be made to be stored in decoding image storage section 11.

0024Motion vector calculation part 13 calculates the motion vector of an object block based on the decoding image stored in the original picture image and decoding image storage section 11. Although calculation in particular of a motion vector is not limited, it is realizable with publicly known art. It is detecting the reference field which the object block should refer to, and the substantially same thing to calculate the motion vector of an object block.

0025Prediction image generation part 14 generates a prediction image based on the decoding image stored in decoding image storage section 11, and the motion vector obtained by motion vector calculation part 13. The composition and operation of prediction image generation part 14 are explained in detail later.

0026Refreshment control part 15 generates the refreshment control signal for realizing sequential refreshment explained while referring to Drawing 1. Selecting part 16 chooses the prediction picture or the "zero" generated by prediction image generation part 14 according to a refreshment control signal. At this time, the prediction picture generated by prediction image generation part 14 is chosen in the field which does not perform refreshment. In this case, prediction error signal generating part 1 outputs the prediction error signal showing the difference of an original picture image and a prediction picture. That is, inter-frame coding is performed. On the other hand, "zero" is chosen in the field which performs refreshment. In this case, prediction error signal generating part 1 outputs a prediction error signal for an original picture image as it is. That is, the coding in a frame is performed.

0027Motion vector data coding part 21 codes the motion vector information showing the motion vector obtained by motion vector calculation part 13. The method of coding motion vector information is entropy coding, for example. Control data coding part 22 codes the control data generated in prediction image generation part 14. The method of coding control data is entropy coding, for example. Control data is explained in detail later.

0028Drawing 7 is a figure showing the composition of prediction image generation part 14. While referring to Drawing 6, as it explained, motion vector information and a refreshment control signal are given to prediction image generation part 14.

0029Motion vector information is given to reference field primary detecting element 31. Motion vector information is generated by motion vector calculation part 13, and as shown in Drawing 8, it expresses the motion vector of an object block. And reference field primary detecting element 31 detects the position (namely, coordinates) of the reference field in the reference picture which a coding symmetrical block should refer to based on the motion vector information. If it is the thing of an object block for example, whose motion vector of the object block the coordinates of four corners were "" (96 (89 (96 (89, *121), *121), *128), *128), and was "" (7, *9), "" (89 (82 (89 (82, *112), *112), *119), *119) is obtained as a position of a reference field. Although a reference picture in particular is not limited, it is a picture of a just before [ an original picture image ] frame, for example. And reference field primary detecting element 31 gives the reference field information that the detected reference field is expressed to extraction part 32 and judgment part 34.

0030Extraction part 32 extracts a reference image from decoding image storage section 11, and extracts the pixel data of the reference field in a reference image further based on reference field information. When the size of a symmetrical block is 8x8, 64 pixel data is extracted.

0031A refreshment control signal is given to refreshment Management Department 33. A refreshment control signal is generated in refreshment control part 15, in order to realize refreshment one by one, and it directs the field which should perform the coding in a frame within each frame. And refreshment Management Department 33 generates the effective field information showing the effective field where it is allowed to be referred to in other pictures according to the refreshment control signal.

0032Drawing 9 is a figure explaining effective field information. In order to explain simply here, as shown in Drawing 9 (a), the imaging range of each frame shall comprise five fields 41a-41e, and each field 41a-41e shall be refreshed in order. That is, in the n-th frame, the n+1st frame, the n+2nd frame, the n+3rd frame, and the n+4th frame, field 41a, field 41b, field 41c, 41 d of fields, and field 41e shall be refreshed, respectively.

0033In an embodiment, an effective field is defined as "a refreshment field and the field above the refreshment field", as shown in Drawing 9 (b). That is, in the n-th frame, field 41a is an effective field. In the n+1st frame, fields 41a and 41b are effective fields. In the n+2nd frame, fields 41a-41c are effective fields. In the n+3rd frame, fields 41a-41d are effective fields. In the n+4th frame, fields 41a-41e are effective fields.

0034Or an effective field may be made to be defined as "the field where refreshment was performed within the refreshment field and the prescribed period", as shown in Drawing 9 (c). In Drawing 9 (c), a "prescribed period" is 2 frame time. That is, for example, if the n+2nd frame is observed, field 41b is refreshed in the n+1st frame, and field 41a is refreshed by the n-th frame. Therefore, the effective fields of the n+2nd frame are fields 41a-41c. An effective field is similarly defined about other frames. In the following explanation, fields other than the effective field in a frame may be called an "un-effective field."

0035Judgment part 34 investigates whether it is that the reference field detected by reference field primary detecting element 31 belongs only to an effective field. That is, judgment part 34 investigates whether the pixel of an un-effective field also includes whether a reference field contains only the pixel of an effective field. The effective field information showing an effective field (and un-effective field) is generated by refreshment Management Department 33 for every frame, as mentioned above.

0036Complement section 35 generates a complement picture according to the algorithm explained later. A complement image may be generated using the decoding image (namely, reference image) stored in decoding image storage section 11, and may be generated independently with a decoding image. Selecting part 36 chooses the pixel of the complement picture generated by the pixel or complement section 35 of a reference field extracted by extraction part 32 according to the judgment result by judgment part 34. That is, the picture of the reference field is outputted about the reference field belonging to an effective field, and a complement picture is outputted about the reference field belonging to an un-effective field.

0037Operation of prediction image generation part 14 is explained while referring to Drawing 10 and Drawing 11. Here, the block for coding shall be 8x8 pixels. In this case, a reference field is also 8x8 pixels.

0038Drawing 10 shows operation in case a reference field contains only the pixel of an effective field. In this case, prediction image generation part 14 outputs the image of the reference field in a decoding image as it is as a prediction image for inter-frame coding. That is, selecting part 35 chooses the pixel data of the reference field of a decoding image as pixel data of a prediction image, respectively.

0039Drawing 11 shows operation in case a reference field contains the pixel of an un-effective field. this example -- the of reference field 1- the 7th line assumes that it belongs to an effective field and the 8th line belongs to the un-effective field. In this case, prediction image generation part 14 outputs the picture of that reference field about the reference field belonging to an effective field as a prediction picture, and outputs a complement picture about the reference field belonging to an un-effective field. namely, 8x8-block the 1- the pixel data of the reference field of a decoding image is chosen as pixel data of the 7th line, and the pixel data of a complement image is chosen as pixel data of the 8th line.

0040The prediction picture generated by Above by making it like is sent to prediction error signal generating part 1. And the difference (namely, error) of an original picture image and a prediction picture is calculated, and the error is coded. However, in a refreshment field, since the coding in a frame is performed, "zero" is chosen as a change of a prediction picture by selecting part 16.

0041The effective field information generated by refreshment Management Department 33 is coded in control data coding part 22. That is, effective field information is transmitted as control data. Next, the example of the method of generating a complement picture is described. In the following explanation, as shown in Drawing 12 (a), the block for coding (or unit of motion prediction) shall be 16x16 pixels. And it is assumed that - (0, 0) (15, j) belongs to the effective field.

0042In the 1st complementing method, the pixel data (namely, pixel data of a complement picture) of an un-effective field is generated by copying the pixel data of the nearest pixel in an effective field, as shown in Drawing 12 (b). This processing is denoted by following the (1) type. pred*(x, y) *=*pred* (x, j) ... (1) -- here, "pred* (x, y)" is pixel data of the pixel of an un-effective field. "pred* (x, j)" is pixel data of each pixel on the line which adjoins an un-effective field.

0043The 1st complementing method is realized by the composition shown in Drawing 12 (c). That is, in order to realize the 1st complementing method, complement section 35 is provided with copy part 41. Copy part 41 performs the operation of the above-mentioned (1) formula about the pixel belonging to an un-effective-among pixels which constitute reference field field.

0044In the 2nd complementing method, the pixel data of each pixel of an un-effective field is generated by equalizing the pixel data of the pixel which adjoins the un-effective field in an effective field, as shown in Drawing 13 (a). This processing is denoted by following the (2) type.

0045<maths num="1"><img file="WO2009037726A1_D0001.tif" /></maths>

0046The 2nd complementing method is realized by the composition shown in Drawing 13 (b). That is, in order to realize the 2nd complementing method, complement section 35 is provided with effective reference pixel storage part 42, boundary pixel selection means 43, and equalizing section 44. Effective reference pixel storage part 42 memorizes the pixel data of the pixel belonging to the effective field of the pixels which constitute a reference field based on effective field information. Boundary pixel selection means 43 chooses the pixel data of the pixel on the line which adjoins an un-effective-among pixels memorized by effective reference pixel storage part 42 field. Equalizing section 44 equalizes pixel data with selected boundary pixel selection means 43. That is, the operation of the above-mentioned (2) formula is performed.

0047In the 3rd complementing method, the pixel data of an un-effective field is generated by filtering the pixel data of the pixel which adjoins the un-effective field in an effective field, as shown in Drawing 14 (a). This processing is denoted by following the (3) type.

0048<maths num="2"><img file="WO2009037726A1_D0002.tif" /></maths>

0049In (3) types, a filter factor shall be "1." That is, for example, when complementing in the direction of 45 slant, filtering is performed by the following conditions. w_x,y*(x-y+j-1)=0.25 w_x,y*(x-y+j)=0.5 w_x,y* (x-y+j+1) =0.25 The time of "i" corresponding to neither "x-y+j-1" nor "x-y+j" nor and "x-y+j+" "w_x,y* (i)=0 The 3rd complementing method is realized by the composition shown in Drawing 14 (b)." That is, in order to realize the 4th complementing method, complement section 35 is provided with effective reference pixel storage part 42, boundary pixel selection means 43, and filter 45. Effective reference pixel storage part 42 and boundary pixel selection means 43 are the same as the 2nd complementing method. Filter 45 performs filtering of the above-mentioned (3) formula about pixel data with selected boundary pixel selection means 43.

0050The data in which the 4th complementing method expresses independently the color decided beforehand and luminosity as the pixel of an effective field as pixel data of a complement picture is generated. Prediction image generation part 14 of an embodiment generates a complement picture by above 1st - the arbitrary methods in the 4th complementing method, for example. Prediction image generation part 14 chooses dynamically the 1st - the method optimal out of two or more complementing methods in the 4th complementing method (in for example, block unit), and it may make it generate a complement picture by the selected method.

0051Drawing 15 is a figure showing the composition of a prediction image generation part provided with the function which chooses a complementing method. In Drawing 15, reference field primary detecting element 31, extraction part 32, refreshment Management Department 33, and judgment part 34 are as having explained, while referring to Drawing 7.

0052Complement section 37 can perform a plurality of complementing methods (for example, the 1st - the 4th complementing method which were mentioned above). Calculation part 38 chooses the optimal method from a plurality of complementing methods. And complement section 37 outputs the complement picture generated with the selected complementing method. Calculation part 38 outputs the complementing method information showing the selected complementing method. It is coded in control data coding part 23, and complementing method information is sent to a decoding device.

0053Drawing 16 is a figure showing the composition of complement section 37 provided with the function which chooses a complementing method. the [ the 1st in which complement section 37 generates complement pixel data with the 1st - the 4th complementing method in this example - ] -- it shall have complement treating parts 41a-41d of four Error calculation parts 42a-42d calculate the error of the pixel data of the pixel belonging to the un-effective field in a reference field, and the complement pixel data generated by complement treating parts 41a-41d, respectively. "The pixel belonging to the un-effective field in a reference field" is a pixel replaced by the complement pixel in complement section 37. Judgment part 43 chooses the complement treating part which generates the pixel data in which an error serves as the minimum from complement treating parts 41a-41d. Selecting part 44 chooses the pixel data generated by the corresponding complement treating part according to the decision result by judgment part 43.

0054The method of choosing a complementing method is not limited to a described method. For example, it may be made to determine a complementing method based on the motion vector of the block for coding, or the motion vector of a circumference block. In this case, for example, if the motion vector of an object block is small, a complement picture will be generated in accordance with the 1st complementing method, and as long as the motion vector of an object block is large, it may be made to generate a complement picture in accordance with the 2nd complementing method.

0055A complement picture is generated when a reference field contains the pixel of an un-effective field, as mentioned above. If it puts in another way, when a reference field does not contain the pixel of an un-effective field, it is not necessary to generate a complement picture and to transmit complementing method information to a decoding device. Therefore, only when a reference field contains the pixel of an un-effective field, it may be made for a prediction image generation part to be provided with switch 39 which leads complementing method information to control data coding part 23. If this composition is introduced, the amount of information of the control data transmitted to a decoding device is reducible. It is judged using the effective field information generated by refreshment Management Department 33 whether a reference field contains the pixel of an un-effective field.

0056Drawing 17 is a figure explaining the notifying method of an effective field / un-effective field. Here, each frame shall comprise fields 501-505. Refer to the picture of the last frame for an original picture image (frame for coding). Field 503 shall be refreshed in a reference picture and field 504 shall be refreshed by an original picture image.

0057In the example shown in Drawing 17, the effective fields for each block belonging to fields 501-503 of an original picture image are only fields 501-503 of a reference picture. On the other hand, the effective fields for each block belonging to field 505 of an original picture image are all the fields (namely, fields 501-505) of a reference picture. Namely, effective fields differ for every block.

0058The effective field information which shows an effective field is transmitted to a decoding device via control data coding part 23, as mentioned above. Effective field information is generated per block and it may be made to transmit it to a decoding device at this time. A plurality of blocks which constitute an original picture image are group-ized to the block belonging to the field (fields 501-503) to which a reference field is restricted, and the block belonging to the field (field 505) to which a reference field is not restricted, and it may be made to transmit effective field information to a decoding device for every group. In H.264, it can process by making into a unit the slice which comprises a plurality of blocks. In this case, effective field information is given to a slice header and it may be made to transmit to a decoding device.

0059It is transmitted to a video decoding device and the video data coded by the video coding equipment of the above-mentioned composition is decrypted. Or once it is recorded on a recording medium, the coded video data is read by a video decoding device, and is decrypted.

0060Drawing 18 is a figure showing the composition of the video decoding device of the embodiment of the present invention. This video decoding device decrypts the coding data generated by above-mentioned video coding equipment, and reproduces video. In the following explanation, prediction image generation part 14 with which video coding equipment is provided shall generate a complement picture with the complementing method decided beforehand.

0061Separation part 51 divides the received coding data into coefficient data, motion vector data, and control data. Coefficient decoding part 52 carries out entropy decryption of the coefficient data. The entropy decryption by coefficient decoding part 52 corresponds to the entropy decryption by coefficient coding part 4 of video coding equipment. Inverse quantization part 53 carries out dequantization of the coefficient data by which entropy decryption was carried out. The dequantization by inverse quantization part 53 corresponds to quantization by quantizing part 3. Reverse orthogonal transformation section 54 carries out reverse rectangular cross conversion of the coefficient data by which dequantization was carried out. The reverse rectangular cross conversion by reverse orthogonal transformation section 54 corresponds to the rectangular conversion by orthogonal transformation section 2.

0062Decoding image generation part 55 reproduces an original picture image using a prediction image. The reproduced original picture image is temporarily memorized by decoding image storage section 56 as a decoding image. At this time, after a decoding image is removed by digital blocking filter 57 in block distortion, it may be made to be stored in decoding image storage section 56.

0063Motion vector data decoding part 58 decrypts the received motion vector data. The decryption by motion vector data decoding part 58 corresponds to coding by motion vector data coding part 21 of video coding equipment. Thereby, the motion vector about each block can be obtained. Control data decoding section 59 decrypts the received control data. The decryption by control data decoding section 59 corresponds to coding by control data coding part 22. Control data is effective field information which expresses the field which can be referred to in inter-frame coding here. Prediction image generation part 60 generates a prediction image based on the decoding image, motion vector, and effective field information which are stored in decoding image storage section 56. And in decoding image generation part 55, an original picture image is reproduced using this prediction image.

0064Although omitted in Drawing 18, when the block for decoding belongs to a refreshment field, prediction image generation part 60 outputs "zero." In this case, decoding image generation part 55 is stored in decoding image storage section 56 by making into a decoding image the image which comprises pixel data obtained by reverse orthogonal transformation section 54. That is, decryption in a frame will be performed about this field.

0065Drawing 19 is a figure explaining the composition and operation of an embodiment of prediction image generation part 60. Fundamentally, operation of this prediction image generation part 60 is the same as prediction image generation part 14 with which video coding equipment is provided. However, prediction image generation part 60 is provided in a video decoding device. Effective field information is given from coding equipment.

0066Complement pixel generation part 71 acquires the motion vector of the block for decoding, and takes out the image of the reference field to which the motion vector points from decoding image storage section 56. Judgment part 72 uses effective field information, and judges whether the reference field which complement pixel generation part 71 acquired contains the pixel of the un-effective field. Selecting part 73 chooses the pixel data read from decoding image storage section 56, when the pixel of a reference field belongs to an effective field. On the other hand, selecting part 73 chooses the pixel data of the complement picture which complement pixel generation part 71 generates, when the pixel of a reference field belongs to an un-effective field.

0067Complement pixel generation part 71 generates the pixel data of a complement picture by the same method as the complementing method in coding equipment. When the complementing method which should be performed for every block out of a plurality of complementing methods in coding equipment is chosen dynamically, the complementing method information showing the selected complementing method is given to prediction image generation part 60. And prediction image generation part 60 generates a complement picture with a corresponding complementing method according to the given complementing method information.

0068Thus, in the video coding equipment and the video decoding device of an embodiment, since the refreshment method is adopted one by one, the peak of the amount of information of the coding data for every frame is controlled. Since the picture of the optimal reference field can be used when performing inter-frame coding, degradation of the quality of a picture is suppressed. Since the complement picture generated from the pixel data of an effective field instead of the picture of the un-effective field is used when the reference field contains the pixel of the un-effective field, propagation of an error of an un-effective field can be suppressed.

0069One by one, refreshment may be performed for every block, may be performed for every lines of a plurality of, and may be performed in other units.