JP2007036887A - Coding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coding technique for moving image which is high in coding efficiency and can perform high-accuracy motion prediction, and a decoding technique thereof. <P>SOLUTION: A local motion vector detector 66 obtains a local motion vector LMV by macroblock units for a coding target frame image. A region setting section 64 sets a plurality of global regions on a frame image, and a large-region vector calculator 68 calculates a global motion vector GMV indicating large region motion inside each global region. A local motion vector difference coder 72 obtains and codes a difference ΔLMV, between the local motion vector LMV and the global motion vector GMV in the global region by global regions. A large area motion vector difference coding section 74 obtains and codes a difference ΔGMV between the global motion vector GMV of each global region and a global motion vector GMV<SB>B</SB>that serves as a reference. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an encoding method for encoding a moving image.

  Broadband networks are rapidly developing, and there are high expectations for services that use high-quality moving images. In addition, a large-capacity recording medium such as a DVD is used, and a user group who enjoys high-quality images is expanding. There is compression coding as an indispensable technique for transmitting moving images via a communication line or storing them in a recording medium. As an international standard for moving image compression coding technology, the MPEG4 standard and H.264 standard. There is a H.264 / AVC standard. There is a next-generation image compression technology such as SVC that has both a high-quality stream and a low-quality stream in one stream.

  When streaming a high-resolution moving image or storing it in a recording medium, it is necessary to increase the compression rate of the moving image stream so as not to compress the communication band or increase the storage capacity. In order to enhance the compression effect of moving images, motion compensation interframe predictive coding is performed. In motion-compensated interframe predictive coding, the encoding target frame is divided into blocks, the motion from a reference frame that has already been encoded is predicted for each block, a motion vector is detected, and motion vector information is encoded along with the difference image. Turn into.

Patent Document 1 discloses a moving image coding technique that selects a method with the highest coding efficiency from among various types of motion compensation using intra-frame coding, normal motion compensation, and global motion vectors. .
JP 2003-299101 A

  H. In the H.264 / AVC standard, in order to perform more detailed prediction in motion compensation, the block size of motion compensation can be made variable, and the pixel accuracy of motion compensation can be reduced to ¼ pixel accuracy. Therefore, the amount of code related to the motion vector increases. In addition, in SVC (Scalable Video Coding), which is a next-generation image compression technology, MCTF (Motion Compensated Temporal Filtering) technology is being studied in order to improve temporal scalability. This is a combination of subband division in the time axis direction and motion compensation. Since hierarchical motion compensation is performed, information on motion vectors becomes very large. As described above, the recent video compression coding technology tends to increase the data amount of the entire video stream due to an increase in the amount of information related to motion vectors, and there is a further demand for a technology for reducing the amount of codes resulting from motion vector information. ing.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a coding technique and a decoding technique for moving images that have high coding efficiency and can perform highly accurate motion prediction. .

  In order to solve the above-described problem, an encoding method according to an aspect of the present invention is a picture that configures a moving image, and includes at least one of a plurality of regions defined on a picture that is inter-picture prediction encoded. For one region, global motion vector information indicating the global motion in the region is included in the encoded data of the moving image.

  The “global motion vector” is a vector that represents the motion of the entire region.

  A “picture” is an encoding unit including a frame, a field, a VOP (Video Object Plane), and the like.

  According to this aspect, when a moving image is encoded, a global movement can be captured in at least one region among a plurality of regions defined in the moving image.

  When global motion vectors are defined for two or more regions, difference information between global motion vectors in different regions may be included in the encoded data of the moving image. According to this, the code amount of the global motion vector can be reduced by taking the difference between the regions for the global motion vector obtained for each region.

  When a local motion vector in a predetermined block unit is defined for the picture to be subjected to the inter-picture predictive coding, difference information between the global motion vector and the local motion vector is obtained for each region by using the code of the moving image. May be included in the data. According to this, when the local motion vector is encoded, the amount of code of the local motion vector can be reduced by taking the difference from the global motion vector given for each region on the encoding target picture. The compression efficiency of moving images can be increased.

  When global motion vectors are defined for two or more regions, at least one global motion vector is selected as a reference, and difference information between the reference global motion vector and another global motion vector is selected from the moving image. It may be included in the encoded data. According to this, when encoding global motion vectors of a plurality of regions, the difference from the reference global motion vector can be taken to reduce the amount of coding of the global motion vector and to compress the moving image. Efficiency can be increased.

  Another aspect of the present invention is an encoding device. This apparatus calculates a global motion vector for calculating a global motion vector indicating a global motion in at least one area among a plurality of areas defined on a picture to be subjected to inter-picture prediction encoding of a moving image. Includes a vector calculator.

  Yet another aspect of the present invention is a data structure of a moving image stream. The data structure of the moving picture stream is a data structure of a moving picture stream in which a picture of a moving picture is encoded, and at least one of a plurality of areas defined on a picture to be inter-picture prediction encoded For a region, a global motion vector indicating a global motion in the region is encoded as motion vector information together with the picture to be inter-picture prediction encoded.

  According to this aspect, since the global motion vector indicating the global motion in each region provided on the encoding target picture is encoded, a video stream that captures the global motion for each moving image region is generated. Can be provided.

  The data structure of the moving image stream may be obtained by encoding a difference between global motion vectors in each region as motion vector information together with the encoding target picture. According to this, it is possible to provide a moving image stream with a small global motion vector code amount.

  Further, the data structure of this moving image stream is such that a difference between a global motion vector representing a local motion vector in a predetermined block unit in each region and the local motion vector is encoded as motion vector information together with the encoding target picture. It may be made. According to this, since the local motion vector is encoded in the form of a difference from the global motion vector for each region provided on the encoding target picture, a moving image stream with a small amount of coding of the local motion vector is provided. be able to.

  Yet another embodiment of the present invention is a decoding device. This apparatus is a decoding apparatus that decodes a moving picture stream in which a picture of a moving picture is encoded, and at least one area among a plurality of areas defined on a picture that has been inter-picture prediction encoded, A global motion vector calculating unit that acquires a global motion vector indicating global motion in the region from the moving image stream; The global motion vector calculation unit may acquire a difference value between global motion vectors of each region from the moving image stream, and calculate a global motion vector of each region using the difference value.

  According to this aspect, it is possible to acquire a global motion vector from a moving image stream in which a global motion vector is encoded for each region provided on an image picture, and to capture a global motion for each moving image region.

  By obtaining a difference value of a local motion vector indicating local motion in each region from the moving image stream, and adding the difference value of the local motion vector for each region to the global motion vector of the region, A local motion vector calculation unit that calculates a local motion vector in each region, an image restoration unit that restores a decoding target picture by adding the calculated local motion vector to a difference image acquired from the moving image stream, and May further be included. According to this, the difference between the global motion vector and the local motion vector is acquired from the video stream in which the difference between the local motion vector and the global motion vector is encoded for each region provided on the image picture, By adding the difference value of the local motion vector to the global motion vector every time to obtain the local motion vector and performing motion compensation, the moving image can be reproduced with high accuracy.

  Yet another embodiment of the present invention is a decoding method. In this method, a global motion vector indicating a global motion in a region of at least one region among a plurality of regions defined on an inter-picture predictive-coded picture of a moving image is used as a moving picture picture. Is obtained from the encoded video stream, and the global motion vector information is used for motion compensation of the inter-picture predictive encoded picture. A global motion vector indicating global motion in each region and a local motion vector difference value indicating local motion in each region are acquired from the video stream, and the difference value of the local motion vector for each region Is added to the global motion vector of the region to calculate a local motion vector in each region, and using the calculated local motion vector in each region, motion compensation of the decoding target picture is performed. Also good.

  It should be noted that any combination of the above-described constituent elements and a conversion of the expression of the present invention between a method, an apparatus, a system, a recording medium, a computer program, etc. are also effective as an aspect of the present invention.

  According to the present invention, it is possible to improve the encoding efficiency of moving images.

  FIG. 1 is a configuration diagram of an encoding apparatus 100 according to an embodiment. These configurations can be realized in hardware by a CPU, memory, or other LSI of an arbitrary computer, and in software, it is realized by a program having an image encoding function loaded in the memory. Here, functional blocks realized by the cooperation are depicted. Therefore, those skilled in the art will understand that these functional blocks can be realized in various forms by hardware only, software only, or a combination thereof.

  The encoding apparatus 100 according to the present embodiment includes an MPEG (Moving Picture Experts Group) series standard (MPEG-1, MPEG, standardized by ISO (International Organization for Standardization) / IEC (International Electrotechnical Commission)). -2 and MPEG-4), standardized by ITU-T (International Telecommunication Union-Telecommunication Standardization Sector), which is an international standard organization for telecommunications. 26x series standards (H.261, H.262 and H.263), or H.264, the latest video compression coding standard standardized jointly by both standards organizations. H.264 / AVC (official recommendation names in both organizations are MPEG-4 Part 10: Advanced Video Coding and H.264 respectively).

  In the MPEG series standard, an image frame for intra-frame encoding is an I (Intra) frame, an image frame for forward inter-frame predictive encoding with a past frame as a reference image, a P (Predictive) frame, and past and future An image frame that performs bidirectional inter-frame predictive coding using this frame as a reference image is referred to as a B frame.

  On the other hand, H. In H.264 / AVC, a frame that can be used as a reference image may be a past two frames as a reference image or a future two frames as a reference image regardless of the time. Further, three or more frames can be used as the reference image regardless of the number of frames that can be used as the reference image. Therefore, in MPEG-1 / 2/4, the B frame refers to a Bi-directional prediction frame. Note that in H.264 / AVC, the B frame refers to a bi-predictive prediction frame because the time of the reference image does not matter before and after.

  In the embodiment, a frame is used as an example of the encoding unit, but the encoding unit may be a field. The unit of encoding may be a VOP in MPEG-4.

  The encoding apparatus 100 receives an input of a moving image in units of frames, encodes the moving image, and outputs an encoded stream. The input moving image frame is stored in the frame memory 80.

  The motion compensation unit 60 uses a past or future image frame stored in the frame memory 80 as a reference image, performs motion compensation for each macroblock of the P frame or the B frame, and generates a motion vector and a predicted image. . The motion compensation unit 60 takes the difference between the P frame or B frame image to be encoded and the predicted image, and supplies the difference image to the DCT unit 20. In addition, the motion compensation unit 60 supplies the encoded motion vector information to the multiplexing unit 92.

  The DCT unit 20 performs discrete cosine transform (DCT) on the image supplied from the motion compensation unit 60, and gives the obtained DCT coefficient to the quantization unit 30.

  The quantization unit 30 quantizes the DCT coefficient and provides it to the variable length coding unit 90. The variable length coding unit 90 performs variable length coding on the quantized DCT coefficient of the difference image and supplies the result to the multiplexing unit 92. The multiplexing unit 92 multiplexes the encoded DCT coefficient given from the variable length coding unit 90 and the coded motion vector information given from the motion compensation unit 60 to generate an encoded stream. . When generating the encoded stream, the multiplexing unit 92 performs a process of rearranging the encoded frames in time order.

  In the case of P frame or B frame encoding processing, the motion compensation unit 60 operates as described above. However, in the case of I frame encoding processing, the motion compensation unit 60 does not operate and is not shown here. The I frame is supplied to the DCT unit 20 after intra prediction.

  FIG. 2 is a diagram illustrating the configuration of the motion compensation unit 60. The motion compensation unit 60 detects a motion vector (hereinafter referred to as a “local motion vector”) of a macroblock unit of an encoding target frame, and for each predetermined region provided on the image, A motion vector indicating a smooth motion (hereinafter referred to as “global motion vector”) is obtained. The global motion vector is a vector that represents the motion of the entire region. For example, the global motion vector in each region may represent a local motion vector in units of individual macroblocks in that region.

  The motion compensation unit 60 performs motion prediction based on the local motion vector, outputs a difference image, encodes a difference value between the local motion vector and the global motion vector, and outputs it as motion vector information.

  The local motion vector detection unit 66 refers to the reference image held in the frame memory 80, detects a prediction macroblock having the smallest error with respect to the target macroblock of the encoding target image from the reference image, and determines from the target macroblock. A local motion vector LMV indicating the motion to the predicted macroblock is obtained. Motion detection is performed by searching for a reference macroblock in a reference image matching the target macroblock in units of integer pixels or decimal pixels. The search is normally repeated a plurality of times within the pixel region, and the reference macroblock that best matches the target macroblock is selected as the predicted macroblock in the plurality of searches.

  The local motion vector detection unit 66 gives the obtained local motion vector LMV to the global motion vector calculation unit 68, the motion compensation prediction unit 70, and the local motion vector difference encoding unit 72.

  The motion compensation prediction unit 70 performs motion compensation on the target macroblock using the local motion vector LMV, generates a prediction image, and outputs a difference image between the encoding target image and the prediction image to the DCT unit 20.

  The region setting unit 64 sets a region (hereinafter referred to as “global region”) for obtaining the global motion vector GMV on the frame image. A plurality of global areas are provided in the image. For example, the region setting unit 64 may set a predetermined region as the global region, such as setting the vicinity of the center of the frame image as one global region and setting the periphery thereof as another global region. The global area may be set by the user.

  In addition, when an object such as a person is captured in the image, the region setting unit 64 may automatically extract a region where the object is captured and set it as a global region.

  The region setting unit 64 refers to the local motion vector LMV in the image detected by the local motion vector detection unit 66, automatically extracts a region occupied by a macroblock having a certain amount of motion, and sets the region as a global region. May be.

  The region setting unit 64 provides information on the set global region to the global motion vector calculation unit 68 and the global motion vector difference encoding unit 74.

  The global motion vector calculation unit 68 calculates a global motion vector GMV indicating a global motion in each global region set by the region setting unit 64. For example, the global motion vector calculation unit 68 obtains the average of local motion vectors LMV in the region and sets it as the global motion vector GMV.

  Further, the global motion vector calculation unit 68 may acquire information on global motion in each global region and calculate a global motion vector GMV for each global region based on the information. For example, when the camera is zoomed or panned, the screen is scrolled, etc., the global motion in each global region can be determined from the information regarding the motion of the entire screen, and the global motion vector GMV can be calculated. . The global motion vector calculation unit 68 may automatically extract the motion of an object such as a person on the screen, determine a global motion in each global region from the motion of the object, and calculate a global motion vector GMV. it can.

  The global motion vector calculation unit 68 gives the obtained global motion vector GMV to the local motion vector difference encoding unit 72 and the global motion vector difference encoding unit 74.

  The local motion vector differential encoding unit 72 receives the input of the local motion vector LMV from the local motion vector detection unit 66 and the input of the global motion vector GMV from the global motion vector calculation unit 68, respectively, and local motion in the global region for each global region. A difference ΔLMV = LMV−GMV between the vector LMV and the global motion vector GMV is calculated, and the local motion vector difference ΔLMV is variable-length encoded. The local motion vector difference encoding unit 72 supplies the encoded local motion vector difference ΔLMV to the multiplexing unit 92 as motion vector information.

The global motion vector differential encoding unit 74 receives an input of the global motion vector GMV of each region from the global motion vector calculation unit 68 and selects it based on the global motion vector GMV of at least one region. The reference global motion vector GMV is referred to as a reference global motion vector GMV _B. Global motion vector difference coding unit 74 calculates a difference ΔGMV = GMV-GMV _B of the global motion vector GMV and the reference global motion vector GMV _B reference global motion each global region other than the vector GMV _B, the reference global motion vector GMV Variable length coding is performed on _B and the global motion vector difference ΔGMV.

The global motion vector difference encoding unit 74 gives the encoded reference global motion vector GMV _B and the global motion vector difference ΔGMV of each global region to the multiplexing unit 92 as motion vector information. At this time, the global motion vector difference encoding unit 74 adds the region information about the global region set by the region setting unit 64 to a part of the motion vector information.

The multiplexing unit 92 is provided with the reference global motion vector GMV _B , the global motion vector difference ΔGMV, and the local motion vector difference ΔLMV as motion vector information.

  FIG. 3 is a flowchart for explaining the procedure of motion vector differential encoding by the motion compensation unit 60. The encoding procedure will be described with reference to the examples of FIGS. 4 and 5 as appropriate.

  An encoding target image is input to the frame memory 80 of the encoding apparatus 100 (S10). The local motion vector detection unit 66 of the motion compensation unit 60 detects the local motion vector LMV for each macroblock in the encoding target image (S12).

  Next, the region setting unit 64 sets a global region on the image (S14), and the global motion vector calculation unit 68 calculates a global motion vector GMV for each global region (S16).

  The local motion vector difference encoding unit 72 calculates and encodes the local motion vector difference ΔLMV for each global region (S18). The global motion vector difference encoding unit 74 calculates and encodes the global motion vector difference ΔGMV for each global region (S20).

  4A to 4C are diagrams illustrating an example of the global area. In the example of FIG. 4A, the region setting unit 64 sets the first global region 211 and the second global region 212 on the encoding target image 200. The global motion vector calculation unit 68 obtains the first global motion vector GMV1 in the first global area 211 and obtains the second global motion vector GMV2 in the second global area 212. In this example, no area for obtaining a global motion vector is set in the background portion other than the first global area 211 and the second global area 212.

  In the case of FIG. 4A, when the local motion vector difference encoding unit 72 encodes the local motion vector LMV for each macroblock in the first global region 211, the difference ΔLMV from the first global motion vector GMV1 = LMV-GMV1 is obtained and encoded. Similarly, the local motion vector difference encoding unit 72 obtains and encodes the difference ΔLMV = LMV−GMV2 between the local motion vector LMV and the second global motion vector GMV2 for each macroblock in the second global region 212.

  In the example of FIG. 4A, since the global motion vector GMV is not obtained for the background regions other than the first global region 211 and the second global region 212, the local motion vector difference encoding unit 72 The local motion vector LMV is encoded as it is without obtaining the difference.

  In the example of FIG. 4B, unlike the example of FIG. 4A, the region setting unit 64 sets the background portion other than the first global region 211 and the second global region 212 as the third global region 210. Then, the global motion vector calculation unit 68 obtains the third global motion vector GMV0 in the third global region 210. The local motion vector difference encoding unit 72 obtains and encodes the difference ΔLMV = LMV−GMV0 between the local motion vector LMV and the third global motion vector GMV0 for each macroblock in the third global region 210.

  FIG. 4C shows an example in which a plurality of global regions have an inclusion relationship with each other on the encoding target image 200. In this example, the second global area 212 is included in the first global area 211, and the first global area 211 and the second global area 212 are entirely included in the third global area 210.

  The local motion vector difference encoding unit 72 encodes the difference between the local motion vector LMV and the second global motion vector GMV2 for each macro block inside the second global region 212, and the second outside the second global region 212. Inside the one global area 211, the difference between the local motion vector LMV and the first global motion vector GMV1 is encoded for each macroblock. Further, in the third global area 210 further outside the first global area 211, the difference between the local motion vector LMV and the third global motion vector GMV0 is encoded for each macroblock.

  FIGS. 5A to 5C are diagrams illustrating an example in which a global motion vector difference is calculated by the global motion vector difference encoding unit 74. FIG. Here, as shown in FIG. 4 (b) or FIG. 4 (c), when three global areas are set and global motion vectors GMV0, GMV1, and GMV2 of the respective global areas are obtained, these three global movements are obtained. An example in which the vectors GMV0, GMV1, and GMV2 are encoded will be described.

  FIG. 5A shows a case where no hierarchical structure is provided between the three global motion vectors GMV0, GMV1, and GMV2. In this case, the global motion vector difference encoding unit 74 treats all three global motion vectors GMV0, GMV1, and GMV2 as reference global motion vectors, and obtains 9-bit global motion vectors GMV0, GMV1 and GMV2 are encoded as they are and output.

  FIG. 5B shows a case where a hierarchical structure is provided between the three global motion vectors GMV0, GMV1, and GMV2, where GMV0 is located in the upper hierarchy, and GMV1 and GMV2 are located in the hierarchy immediately below GMV0. . At this time, the global motion vector differential encoding unit 74 uses the global motion vector GMV0 in the upper layer as the reference global motion vector, and the difference ΔGMV1 = GMV1 between the global motion vectors GMV1 and GMV2 in the lower layer and the reference global motion vector GMV0. -Encode GMV0, [Delta] GMV2 = GMV2-GMV0. Thereby, the code amount of each of the global motion vectors GMV1 and GMV2 in the lower layer, which has 9 bits, is reduced to 3 bits and 4 bits by taking the difference from the global motion vector GMV0 in the upper layer.

  FIG. 5C shows a case where another hierarchical relationship is provided between the three global motion vectors GMV0, GMV1, and GMV2, where GMV0 is located in the highest hierarchy, GMV1 is located in the next hierarchy of GMV0, GMV2 is located in a layer below GMV1. At this time, the global motion vector differential encoding unit 74 uses the first-layer global motion vector GMV0 as a reference global motion vector, and the difference ΔGMV1 = GMV1 between the second-layer global motion vector GMV1 and the first-layer global motion vector GMV0. -Encode GMV0. The code amount of the global motion vector GMV1 in the second layer, which was 9 bits, is reduced to 3 bits by taking the difference from the global motion vector GMV0 in the first layer.

  Next, the global motion vector difference encoding unit 74 encodes the difference ΔGMV2 = GMV2−GMV1 between the global motion vector GMV2 in the third hierarchy and the global motion vector GMV1 in the second hierarchy. The code amount of the third-layer global motion vector GMV2 that is 9 bits is reduced to 2 bits by taking the difference from the global motion vector GMV1 of the second layer.

  5B and 5C, the global motion vector difference encoding unit 74 outputs the reference global motion vector GMV0 and the two global motion vector differences ΔGMV1 and ΔGMV2 as motion vector information. At this time, information indicating a hierarchical structure between the three global motion vectors GMV0, GMV1, and GMV2 is added as a part of the motion vector information.

  As shown in the examples of FIGS. 5B and 5C, a hierarchical structure is appropriately provided between global motion vectors, and the difference between adjacent layers is taken to reduce the code amount of the global motion vector. be able to. In the above example, the difference between the global motion vector at the lower level and the reference global motion vector at the higher level is encoded using the global motion vector at the higher level of the hierarchical structure as a reference. A difference between an upper global motion vector and a lower reference global motion vector may be encoded with a certain global motion vector as a reference.

  The global motion vector hierarchical structure may be determined regardless of the global region inclusion relationship, or the order of the global motion vector hierarchical structure may be determined according to the order of the global region inclusion relationship.

  For example, as shown in FIG. 4B, when the first global region 211 and the second global region 212 are included in the third global region 210, the global motion vector differential encoding unit 74 includes the global region. Using the relationship, as shown in FIG. 5B, the global motion vector GMV0 of the third global region 210 is set as the upper layer, and the global motion vectors GMV1 and GMV2 of the first global region 211 and the second global region 212 are used as the upper layer. A differential structure of the global motion vector is performed by providing a hierarchical structure immediately below.

  Further, as shown in FIG. 4C, the second global region 212 is included in the first global region 211, and the first global region 211 and the second global region 212 are included in the third global region 210 as a whole. When there is a relationship, the global motion vector differential encoding unit 74 sets the global motion vector GMV0 of the third global region 210 as the highest layer, the global motion vector GMV1 of the first global region 211 as the second layer, and the second global A hierarchical structure having the global motion vector GMV2 in the region 212 as the third hierarchy is provided, and differential encoding of the global motion vector is performed.

  In this way, if the inclusion relation of the global area set by the area setting unit 64 is used as it is in the global motion vector hierarchical structure, if information on the inclusion relation of the global area is included in a part of the motion vector information, the global area It is not necessary to separately include information on the hierarchical structure of the motion vector in the motion vector information, and the data amount of the header information can be reduced.

  In addition, if the inclusion relationship of the global area reflects the relative difference in the amount of motion of the image, such as near the center of the image and the background area, or the area of the specific object and its background, etc. It is generally expected that the number of bits when the difference is taken is reduced by reflecting the inclusion relationship as it is in the hierarchical structure of the global motion vector and obtaining the global motion vector difference according to the hierarchical structure.

  FIG. 6 is a configuration diagram of the decoding device 300 according to the embodiment. These functional blocks can also be realized in various forms by hardware only, software only, or a combination thereof.

  The decoding apparatus 300 receives an input of the encoded stream, decodes the encoded stream, and generates an output image. The input encoded stream is stored in the frame memory 380.

  The variable length decoding unit 310 performs variable length decoding on the encoded stream stored in the frame memory 380, supplies the decoded image data to the inverse quantization unit 320, and supplies the decoded motion vector information to the motion compensation unit 360. Supply.

  The inverse quantization unit 320 inversely quantizes the image data decoded by the variable length decoding unit 310 and supplies the image data to the inverse DCT unit 330. The image data inversely quantized by the inverse quantization unit 320 is a DCT coefficient. The inverse DCT unit 330 restores the original image data by performing inverse discrete cosine transform (IDCT) on the DCT coefficients inversely quantized by the inverse quantization unit 320. The image data restored by the inverse DCT unit 330 is supplied to the motion compensation unit 360.

  The motion compensation unit 360 uses a past or future image frame as a reference image, generates a prediction image using the motion vector information supplied from the variable length decoding unit 310, and a difference image supplied from the inverse DCT unit 330. Is added to restore and output the original image data.

FIG. 7 is a diagram illustrating the configuration of the motion compensation unit 360. The encoded stream input to the decoding apparatus 300 is encoded by the encoding apparatus 100 of FIG. 1, and the reference global motion vector GMV _B , global motion is the motion vector information supplied to the motion compensation unit 360. There are a vector difference ΔGMV and a local motion vector difference ΔLMV. The motion compensation unit 360 obtains a local motion vector LMV of the decoding target frame with reference to the motion vector information, and performs motion compensation.

The global motion vector calculation unit 362 receives the input of the reference global motion vector GMV _B and the global motion vector difference ΔGMV of each global region from the variable length decoding unit 310, obtains the global motion vector GMV = ΔGMV + GMV _B for each global region, This is given to the motion vector calculation unit 364.

  The local motion vector calculation unit 364 receives the input of the local motion vector difference ΔLMV from the variable length decoding unit 310 and the input of the global motion vector GMV of each global region from the global motion vector calculation unit 362, and the local motion vector for each global region. LMV = ΔLMV + GMV is obtained. The local motion vector calculation unit 364 gives the local motion vector LMV in each global region to the image restoration unit 366.

  The image restoration unit 366 generates a prediction image using the reference image and the local motion vector LMV for each macroblock in each global region, adds the difference image given from the inverse DCT unit 330 and the prediction image, and adds the original image Restore and output the image.

  As described above, according to encoding apparatus 100 of the present embodiment, when encoding a motion vector, motion vector information in a spatial region is represented by a difference value from the global motion vector of that region. In addition, the data amount of the motion vector information itself can be reduced, and the code amount of the entire moving image stream can be reduced to increase the compression efficiency. In addition, by providing a hierarchical structure between the global motion vectors of each spatial region and obtaining and encoding the difference between the global motion vectors, the amount of code of the motion vector information can be further reduced.

  Also, according to decoding apparatus 300 of the present embodiment, a local motion vector difference value is acquired from a moving image stream with high compression efficiency encoded by encoding apparatus 100, and the difference between local motion vectors for each spatial region. A moving image with high image quality can be restored by adding a value to a global motion vector to obtain a local motion vector and performing motion compensation.

  The present invention has been described based on the embodiments. The embodiments are exemplifications, and it will be understood by those skilled in the art that various modifications can be made to combinations of the respective constituent elements and processing processes, and such modifications are within the scope of the present invention. .

  In the above description, the encoding device 100 and the decoding device 300 are MPEG series standards (MPEG-1, MPEG-2, and MPEG-4), H.264, and H.264. 26x series standards (H.261, H.262 and H.263), or H.264 Although video encoding and decoding are performed in accordance with H.264 / AVC, the present invention can also be applied to the case of hierarchical video encoding and decoding with temporal scalability. In particular, the present invention is effective in reducing the amount of motion vector codes in the encoding of motion vectors when the MCTF technique is used.

It is a block diagram of the encoding apparatus which concerns on embodiment. It is a figure explaining the structure of the motion compensation part of FIG. 3 is a flowchart illustrating a procedure for differential encoding of a motion vector by a motion compensation unit in FIG. 2. It is a figure explaining the example of the area | region set on an image by the area | region setting part of FIG. It is a figure explaining the example which calculates a global motion vector difference by the global motion vector difference encoding part of FIG. It is a block diagram of the decoding apparatus which concerns on embodiment. It is a figure explaining the structure of the motion compensation part of FIG.

Explanation of symbols

  20 DCT section, 30 quantization section, 60 motion compensation section, 64 area setting section, 66 local motion vector detection section, 68 global motion vector calculation section, 70 motion compensation prediction section, 72 local motion vector differential encoding section, 74 global Motion vector differential encoding unit, 80 frame memory, 90 variable length encoding unit, 92 multiplexing unit, 100 encoding device, 300 decoding device, 310 variable length decoding unit, 320 inverse quantization unit, 330 inverse DCT unit, 360 Motion compensation unit, 362 global motion vector calculation unit, 364 local motion vector calculation unit, 366 image restoration unit, 380 frame memory.

Claims (7)

  Global motion vector information indicating a global motion in at least one area of a plurality of areas defined on a picture that is a moving picture and is inter-picture prediction encoded Is included in the encoded data of the moving image.   The code according to claim 1, wherein when global motion vectors are defined for two or more regions, difference information between global motion vectors of different regions is included in the encoded data of the moving image. Method.   When global motion vectors are defined for two or more regions, at least one global motion vector is selected as a reference, and difference information between the reference global motion vector and another global motion vector is selected from the moving image. The encoding method according to claim 1, wherein the encoding method is included in the encoded data.   When global motion vectors are defined for two or more regions, a hierarchical structure is provided between the global motion vectors of each region, and difference information between the global motion vectors of different layers is included in the encoded data of the moving image. The encoding method according to claim 1, wherein the encoding method is included.   The difference information between global motion vectors of each region according to the order of the inclusion relationship when the plurality of regions have an inclusion relationship with each other is included in the encoded data of the moving image. 5. The encoding method according to any one of 4.   6. The encoded data of the moving image includes difference information with respect to a global motion vector at a lower level of an inclusion relationship based on a global motion vector of a region at an upper level of the inclusion relationship. Encoding method.   When a local motion vector in a predetermined block unit is defined for the picture to be subjected to the inter-picture predictive coding, difference information between the global motion vector and the local motion vector is obtained for each region by using the code of the moving image. The encoding method according to claim 1, wherein the encoding method is included in encoded data.

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