Efficient coding of global motion vector

Abstract

To efficient coding of satisfactory global motion vectors.SOLUTION: A decoder includes circuitry configured to receive a bitstream, extract the residual of a control point motion vector for a current frame from the bitstream, and combine the residual of the control point motion vector with the prediction of the control point motion vector for the current frame. Related apparatus, systems, techniques, and articles are also explained.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims the benefit of priority to U.S. Provisional Patent Application No. 62 / 838,521, filed April 25, 2019, and entitled "EFFICIENT CODING OF GLOBAL MOTION VECTORS," which is incorporated herein by reference in its entirety.

[0002] The present invention relates generally to the field of video compression, and in particular to efficient coding of global motion vectors. [Background technology]

[0003] A video codec can include electronic circuitry or software that compresses or decompresses digital video. It can convert uncompressed video into a compressed format, or vice versa. In the context of video compression, a device that compresses video (and / or performs some function thereof) can typically be called an encoder, and a device that decompresses video (and / or performs some function thereof) can be called a decoder.

[0004] The format of the compressed data can conform to standard video compression specifications. The compression can be lossy, in that the compressed video lacks some information present in the original video. The consequences of this can include the decompressed video having lower quality than the original uncompressed video because there is insufficient information to accurately reconstruct the original video.

[0005] There may be a complex relationship between video quality, the amount of data used to represent the video (e.g., determined by bit rate), the complexity of the encoding and decoding algorithms, sensitivity to data loss and errors, ease of organization, random access, end-to-end delay (e.g., latency), and the like.

[0006] Motion compensation can include an approach for predicting a video frame or a portion thereof given a reference frame, such as a past and / or future frame, by considering the motion of a camera and / or objects in the video. This can be employed in encoding and decoding video data for video compression, for example, in encoding and decoding using the Motion Picture Experts Group (MPEG)-2 (also referred to as Advanced Video Coding (AVC) and H.264) standard. Motion compensation can describe a picture in terms of the transformation of a reference picture into a current picture. The reference picture can be temporally past compared to the current picture and from the future compared to the current picture. Compression efficiency can be improved when images can be accurately synthesized from previously transmitted and / or stored images. Summary of the Invention [Means for solving the problem]

[0007] In one aspect, the decoder includes circuitry configured to receive a bitstream, extract from the bitstream residuals of control point motion vectors for a current frame, and combine the residuals of the control point motion vectors with predictions of the control point motion vectors for the current frame.

[0008] In another aspect, a method includes receiving, by a decoder, a bitstream, the method includes extracting from the bitstream residuals of control point motion vectors for a current frame, and combining the residuals of the control point motion vectors with predictions of the control point motion vectors for the current frame.

[0009] The details of one or more variations of the subject matter described herein are set forth in the accompanying drawings and the description below. Other features and advantages of the subject matter described herein will be apparent from the description and drawings, and from the claims. The present specification also provides, for example, the following items: (Item 1) A decoder, the decoder comprising: A circuitry comprising: receiving a bitstream; extracting control point motion vector residuals for a current frame from the bitstream; combining the residual of the control point motion vector with a prediction of the control point motion vector for the current frame; a network configured to: A decoder comprising: (Item 2) Item 1, the decoder further configured to decode the current frame using the combined residual of the control point motion vector and the prediction of the control point motion vector. (Item 3) Item 1. The decoder of item 1, further configured to determine the prediction of the control point motion vector. (Item 4) 4. The decoder of claim 3, wherein determining a prediction of the control point motion vector includes using a control point motion vector decoded for a previous frame as the prediction of the control point motion vector. (Item 5) 5. The decoder of claim 4, wherein the bitstream includes an index to a list of available reference frames, the index identifying the previous frame for use in determining the prediction of the control point motion vector. (Item 6) Item 1. The decoder of item 1, wherein the control point motion vectors include translational motion vectors. (Item 7) Item 2. The decoder according to item 1, wherein the control point motion vectors are vectors of a four-parameter affine motion model. (Item 8) Item 2. The decoder of item 1, wherein the control point motion vectors are vectors of a six-parameter affine motion model. (Item 9) an entropy decoder processor configured to receive the bitstream and decode the bitstream into quantized coefficients; an inverse quantization and inverse transform processor, the inverse quantization and inverse transform processor configured to process the quantized coefficients including performing inverse discrete cosine; A deblocking filter; A frame buffer and an intra-prediction processor; Item 1. The decoder of item 1, further comprising: (Item 10) Item 1. The decoder of item 1, wherein the current frame includes a current block that forms part of a quadtree+binary decision tree. (Item 11) Item 1. The decoder of item 1, wherein the current frame includes a current block that is a coding tree unit. (Item 12) Item 1. The decoder of item 1, wherein the current frame includes a current block that is a coding unit. (Item 13) Item 1, the decoder, wherein the current frame includes a current block that is a prediction unit. (Item 14) 1. A method comprising: receiving, by a decoder, a bitstream; extracting control point motion vector residuals for a current frame from the bitstream; combining the residual of the control point motion vector with a prediction of the control point motion vector for the current frame; A method comprising: (Item 15) Item 12. The method of item 11, further comprising: decoding the current frame using the combined residual of the control point motion vector and the prediction of the control point motion vector. (Item 16) Item 12. The method of item 11, further comprising determining the prediction of the control point motion vector. (Item 17) Item 17. The method of item 16, wherein determining a prediction of the control point motion vector includes using a control point motion vector decoded for a previous frame as the prediction of the control point motion vector. (Item 18) Item 18. The method of item 17, wherein the bitstream includes an index to a list of available reference frames, the index identifying the previous frame for use in determining the prediction of the control point motion vector. (Item 19) Item 12. The method according to item 11, wherein the control point motion vector is a translational motion vector. (Item 20) Item 12. The method according to item 11, wherein the control point motion vectors are vectors of a four-parameter affine motion model. (Item 21) Item 12. The method according to item 11, wherein the control point motion vectors are vectors of a six-parameter affine motion model. (Item 22) The decoder further comprises: an entropy decoder processor configured to receive the bitstream and decode the bitstream into quantized coefficients; an inverse quantization and inverse transform processor, the inverse quantization and inverse transform processor configured to process the quantized coefficients including performing inverse discrete cosine; A deblocking filter; A frame buffer and an intra-prediction processor; Item 12. The method of item 11, comprising: (Item 23) Item 12. The method of item 11, wherein the current frame includes a current block that forms part of a quadtree+binary decision tree. (Item 24) Item 12. The method of item 11, wherein the current frame includes a current block that is a coding tree unit. (Item 25) Item 12. The method of item 11, wherein the current frame includes a current block that is a coding unit. (Item 26) Item 12. The method of item 11, wherein the current frame includes a current block that is a prediction unit. [Brief explanation of the drawings]

[0010] For the purpose of illustrating the invention, the drawings show aspects of one or more embodiments of the invention. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown in the drawings.

[0011] [Figure 1] FIG. 1 is a diagram illustrating motion vectors of an example frame with global and local motion.

[0012] [Figure 2] FIG. 2 illustrates three example motion models that may be utilized for global motion, including their index values ​​(0, 1, or 2).

[0013] [Figure 3] FIG. 3 is a process flow diagram according to some example implementations of the present subject matter.

[0014] [Figure 4] FIG. 4 is a system block diagram of an example decoder according to some example implementations of the present subject matter.

[0015] [Figure 5] FIG. 5 is a process flow diagram according to some example implementations of the present subject matter.

[0016] [Figure 6] FIG. 6 is a system block diagram of an example encoder in accordance with some example implementations of the present subject matter.

[0017] [Figure 7] FIG. 7 is a block diagram of a computing system that may be used to implement any one or more of the methodologies disclosed herein and any one or more portions thereof.

[0018] The drawings are not necessarily to scale and may be illustrated by phantom lines, schematic representations, and partial views. In some instances, details that are not necessary for an understanding of the embodiments or that make other details difficult to perceive may be omitted. Like reference symbols in the various drawings indicate like elements. DETAILED DESCRIPTION OF THE INVENTION

[0019] Global motion in video refers to motion occurring throughout the frame. Global motion may be caused by camera motion; for example, but not limited to, camera panning and zooming may typically generate motion within a frame that may affect the entire frame. Motion present within a portion of a video may be referred to as local motion. Local motion may be caused by moving objects within a scene, such as, but not limited to, an object moving from left to right within a scene. Video may contain a combination of local and global motion. Some implementations of the present subject matter may provide an efficient approach for communicating global motion to a decoder and the use of global motion vectors in improving compression efficiency.

[0020] FIG. 1 is a diagram illustrating an example embodiment of motion vectors for an example frame 100 with global and local motion. Frame 100 may include several blocks of pixels, illustrated as squares, and their associated motion vectors, illustrated as arrows. Squares (e.g., blocks of pixels) with arrows pointing up and to the left may indicate blocks with motion that can be considered global motion, while squares with arrows pointing in other directions (indicated by 104) may indicate blocks with local motion. In the illustrated example of FIG. 1, many of the blocks have the same global motion. Signaling global motion in a header, such as a picture parameter set (PPS) or sequence parameter set (SPS), and using the signaled global motion may reduce the motion vector information required by blocks and result in improved prediction. For illustrative purposes, the embodiments described below refer to determining and / or applying global or local motion vectors at the block level, although global motion vectors may be determined and / or applied with respect to any region of a frame and / or picture (including, without limitation, a region comprised of multiple blocks, a region bounded by any geometric form such as, but not limited to, a region defined by geometric and / or exponential coding, in which one or more lines and / or curves bounding a shape may be angled and / or curved, and / or the entire frame and / or picture). Although signaling is described herein as being performed at the frame level and / or within a header and / or frame parameter set, signaling may alternatively or additionally be performed at a sub-picture level, where a sub-picture may include any region of a frame and / or picture as described above.

[0021] As an example, still referring to FIG. 1, a simple translational motion is represented by a two-component MV that describes the amount of block and / or pixel displacement within the current frame. x , MV yMotion compensation may be described using a motion vector (MV) with ∑ m ... For example, a six-parameter affine motion can be described as follows: x'=ax+by+c y'=dx+ey+f The four-parameter affine motion can be described as follows. x'=ax+by+cy'=-bx+ay+f

[0022] where (x,y) and (x',y') are pixel locations in the current and reference pictures, respectively, and a, b, c, d, e, and f are parameters of the affine motion model.

[0023] Continuing with reference to FIG. 1 , parameters used to describe affine motion may be signaled to a decoder to apply affine motion compensation at the decoder. In some approaches, the motion parameters may be signaled explicitly or by signaling translational control point motion vectors (CPMVs) and then deriving affine motion parameters from the translational motion vectors. Two control point motion vectors (CPMVs) may be utilized to derive affine motion parameters for a four-parameter affine motion model, and three control point translational motion vectors (CPMVs) may be utilized to obtain parameters for a six-parameter motion model. Signaling affine motion parameters using control point motion vectors may enable the use of efficient motion vector coding methods to signal affine motion parameters.

[0024] In some implementations, still referring to FIG. 1, global motion signaling may be included in a header such as a PPS or SPS. Global motion may vary between pictures. Motion vectors signaled in the picture header may describe motion relative to a previously decoded frame. In some implementations, global motion may be translational or affine. The motion model used (e.g., the number of parameters, whether the model is affine, translational, or other) may also be signaled in the picture header. FIG. 2 illustrates three example motion models 200 that may be utilized for global motion, including their index values ​​(0, 1, or 2).

[0025] Continuing with reference to Figure 2, a PPS may be used to signal parameters that may change between pictures of a sequence. Parameters that remain the same for a sequence of pictures may be signaled in a sequence parameter set to reduce the size of the PPS and reduce the video bitrate. An exemplary picture parameter set (PPS) is shown in Table 1. [Table 1-1] [Table 1-2] [Table 1-3] [Table 1-4] [Table 1-5]

[0026] Still referring to FIG. 2, additional fields may be added to the PPS to signal global motion. In the case of global motion, the presence of global motion parameters within a sequence of pictures can be signaled within the SPS, and the PPS references the SPS by an SPS ID. The SPS may be modified to add a field to signal the presence of global motion parameters within the SPS in some approaches to decoding. For example, a 1-bit field may be added to the SPS. If the global_motion_present bit is 1, global motion-related parameters may be expected to be present in the PPS, and if the global_motion_present bit is 0, global motion parameter-related fields may not be present in the PPS. For example, the PPS of Table 1 may be extended to include a global_motion_present field, e.g., as shown in Table 2. [Table 2-1] [Table 2-2]

[0027] Similarly, the PPS may include a pps_global_motion_parameters field for the frame, for example, as shown in Table 3. [Table 3]

[0028] More specifically, the PPS may include fields for characterizing global motion parameters, for example, using control point motion vectors as shown in Table 4. [Table 4-1] [Table 4-2]

[0029] As a further non-limiting example, Table 5 below may represent an exemplary SPS. [Table 5-1] [Table 5-2] [Table 5-3] [Table 5-4] [Table 5-5] [Table 5-6] [Table 5-7] [Table 5-8] [Table 5-9]

[0030] The SPS table as above may be extended as described above to incorporate a global motion presence indicator as shown in Table 6. [Table 6]

[0031] Additional fields may be incorporated within the SPS to reflect further indicators as described within this disclosure.

[0032] In an embodiment, still referring to Figure 2, sps_affine_enabled_flag in the PPS and / or SPS may specify whether affine model-based motion compensation can be used for inter prediction. If sps_affine_enabled_flag is equal to 0, the syntax may be constrained so that affine model-based motion compensation is not used in coded video sequences (CLVS), and inter_affine_flag and cu_affine_type_flag may not be present in the coding unit syntax of CLVS. Otherwise (sps_affine_enabled_flag is equal to 1), affine model-based motion compensation can be used in CLVS.

[0033] Continuing with reference to FIG. 2, sps_affine_type_flag in the PPS and / or SPS may specify whether 6-parameter affine model-based motion compensation may be used for inter-prediction. If sps_affine_type_flag is equal to 0, the syntax may be constrained such that 6-parameter affine model-based motion compensation is not used in CLVS, and cu_affine_type_flag may not be present in the CLVS coding unit syntax. Otherwise (sps_affine_type_flag is equal to 1), 6-parameter affine model-based motion compensation may be used in CLVS. When not present, the value of sps_affine_type_flag may be inferred to be equal to 0.

[0034] Still referring to FIG. 2, translational CPMVs may be signaled within the PPS. Control points may be predefined. For example, control point MV 0 may be relative to the top left corner of the picture, MV 1 may be relative to the top right corner, and MV 3 may be relative to the bottom left corner of the picture. Table 4 illustrates an example approach for signaling CPMV data depending on the motion model used.

[0035] In an exemplary embodiment, still referring to FIG. 2 , an array amvr_precision_idx, which may be signaled within a coding unit, coding tree, or equivalent, may specify a resolution of the motion vector difference AmvrShift, which may be defined as a non-limiting example as shown in Table 7 as shown below: The array indexes x0, y0 may specify the location (x0, y0) of the top-left luma sample of the considered coding block relative to the top-left luma sample of the picture; when amvr_precision_idx[x0][y0] is absent, it may be inferred to be equal to 0. When inter_affine_flag[x0][y0] is equal to 0, the variables MvdL0[x0][y0][0], MvdL0[x0][y0][1], MvdL1[x0][y0][0], MvdL1[x0][y0][1], which represent the motion vector difference values ​​corresponding to the considered block, may be, for example, [ka] If inter_affine_flag[x0][y0] is equal to 1, then the variables MvdCpL0[x0][y0][0][0], MvdCpL0[x0][y0][0][1], MvdCpL0[x0][y0][1][0], MvdCpL0[x0][y0][1][1], MvdCpL0[x0][y0][2][0], and MvdCpL0[x0][y0][2][1] may be modified, for example, as follows: [ka] [ka] The correction may be made through a shifting step, such as: [Table 7]

[0036] Continuing with reference to Figure 2, the global motion may be relative to a previously coded frame. When only one set of global motion parameters exists, the motion may be relative to the frame presented immediately before the current frame.

[0037] Still referring to FIG. 2, some implementations of the present subject matter may include predicting global motion vectors in a current frame from previously encoded global motion vectors of past frames to improve compression.

[0038] Continuing with reference to FIG. 2, a current picture being encoded as an interpicture may use motion estimation to improve compression. Global motion vectors for the current picture may be signaled in the PPS. In some approaches to video compression, when encoding global motion parameters (e.g., control point motion vectors) in the current frame, the following information may already be decoded and available: 1) global motion parameters from past frames, 2) global motion parameters already encoded in the current frame for available reference pictures in List0, and 3) control point motion vectors in the global motion parameters being coded.

[0039] Still referring to FIG. 2, a predicted motion vector (PMV) of a control point motion vector (CPMV) may be determined from a previously coded motion vector, and the difference between the CPMV and the PMV may be coded to reduce bits and improve compression efficiency.

[0040] For example, with continued reference to Figure 2, CPMV0 i , CPMV1 i , and CPMV2 imay be three control point motion vectors for frame 'i' to be coded. In an exemplary method, CPMV0 represents vector components and / or vectors determined with respect to past frames relative to the current frame, including but not limited to a reference frame and / or immediately preceding frame. i-1 But CPMV0 i The difference between the x and y components of the motion vector and its predicted value may be coded.

[0041] Still referring to FIG. 2, for CPMV(j,i), j in the range 0<=j<3 may be a motion vector number, and i in the range 0<=i<=ref_pic_count may be a reference picture index. ref_pic_count=0 may refer to the current picture. CPMV(j,1) may be used as a prediction of CPMV(j,0). Control points for global motion within a frame may be at the corners of the frame, and CPMVs at the corresponding corners of the frame are likely to be similar and serve as better predictions.

[0042] Continuing with reference to Figure 2, as a non-limiting example, a more complex motion vector prediction may use CPMV with respect to all available reference pictures in the list. In this exemplary method, CPMV(j,i) may be used as a prediction of CPMV(j,0). In this case, the index i may also be coded in addition to the motion vector difference.

[0043] Still referring to Figure 2, a previously coded CPMV may be used as a prediction to encode a subsequent CPMV, which may be the next CPMV. For example, CPMV(j,i-1) may be used as a prediction for CPMV(j,i). In this case, the index i may also be coded in addition to the motion vector difference. When only one set of CPMVs is coded, CPMV0 may be the prediction for CPMV1 and CPMV2.

[0044] Still referring to FIG. 2, by way of non-limiting example, Table 5 shows an exemplary PPS with global motion parameters using control point motion vectors. [Table 8-1] [Table 8-2]

[0045] Table 6 shows another example PPS with differentially coded global motion parameters for one or more frames in the reference picture list. [Table 9-1] [Table 9-2]

[0046] With continued reference to FIG. 2, the following is exemplary pseudocode for deriving the expected CPMV according to an exemplary implementation: get_cpmv_pred(i,j){ if(i==0){ if(j==0){ pmv.x=0; pmv.y=0; }else{ pmv.x=mv0_x; pmv.y=mv0_y; } }else{ pmv[j]=cpmv(j,i-1) } return pmv; }

[0047] In many cases, still referring to FIG. 2, global motion may be likely to be present for a set of frames. Global motion may end in response to a scene change or when camera motion stops. Thus, the global motion of successive frames is likely to be similar. In some implementations, when global motion is used within past frames, the CPMV of the past frames is likely to be a good predictor, thereby reducing the bits required to code the motion vector difference and the motion vectors.

[0048] In some implementations, and continuing to refer to Figure 2, it is possible to implicitly code a zero residual for the global motion vector residual by incorporating global motion information of a previous frame. For example, if global motion is enabled and a global motion skip mode (e.g., global_motion_skip flag) is enabled, the global motion information of the previous frame may be incorporated by the current frame as the global motion of the current frame. In some implementations, an index may be provided to a reference list (e.g., List()) indicating from which reference frame motion information may be incorporated.

[0049] 3 is a process flow diagram illustrating an example process 300 for predicting a global motion vector in a current frame from a previously encoded global motion vector of a past frame. In step 305, a current block is received by a decoder. The current block may be contained in a bitstream received by the decoder. The bitstream may include data found in a stream of bits that is input to the decoder when using data compression, for example. The bitstream may include information necessary to decode the video. The receiving step may include extracting and / or parsing the block and associated signaling information from the bitstream. In some implementations, the current block may include a coding tree unit (CTU), a coding unit (CU), or a prediction unit (PU).

[0050] In step 310, still referring to Figure 3, residuals of control point motion vectors for the current frame may be extracted from the bitstream. In step 315, the residuals of control point motion vectors may be combined with predictions of control point motion vectors for the current frame.

[0051] 4 is a system block diagram illustrating an example decoder 400 capable of decoding a bitstream 428 using predicting global motion vectors in a current frame from previously encoded global motion vectors of past frames. The decoder 400 may include an entropy decoder processor 404, an inverse quantization and inverse transform processor 408, a deblocking filter 412, a frame buffer 416, a motion compensation processor 420, and / or an intra-prediction processor 424.

[0052] In operation, still referring to FIG. 4, a bitstream 428 may be received by the decoder 400 and input to the entropy decoder processor 404, which entropy decodes a portion of the bitstream into quantized coefficients. The quantized coefficients may be provided to the inverse quantization and inverse transform processor 408, which performs inverse quantization and inverse transform and generates a residual signal, which may be added to the output of the motion compensation processor 420 or the intra-prediction processor 424, depending on the processing mode. The output of the motion compensation processor 420 and the intra-prediction processor 424 may include a block prediction based on previously decoded blocks. The prediction and residual sum may be processed by the deblocking filter 630 and stored in the frame buffer 640.

[0053] 5 is a process flow diagram illustrating an example embodiment of a process 200 for encoding video using a step of predicting a global motion vector in a current frame from a previously encoded global motion vector of a past frame in accordance with some aspects of the present subject matter, which may improve compression efficiency while reducing the complexity of the encoding step. In step 505, the video frame may undergo initial block segmentation using, for example, a tree-structured macroblock partitioning scheme, which may include partitioning the picture frame into CTUs and CUs. In step 510, residuals of control point motion vectors for the current frame may be determined. In step 515, the blocks may be encoded and included in the bitstream. The encoding may include, for example, utilizing inter-prediction and intra-prediction modes.

[0054] 6 is a system block diagram illustrating an example video encoder 600 capable of predicting a global motion vector in a current frame from a previously encoded global motion vector of a past frame in accordance with some aspects of the present subject matter. The example video encoder 600 may receive an input video 604, which may first be segmented or divided according to a processing scheme such as a tree-structured macroblock partitioning scheme (e.g., quadtree + binary tree). An example of a tree-structured macroblock partitioning scheme may include partitioning a picture frame into large block elements called coding tree units (CTUs). In some implementations, each CTU may be further partitioned one or more times into several sub-blocks, called coding units (CUs). The final result of this partitioning may include a group of sub-blocks, which may be called a prediction unit (PU). Transform units (TUs) may also be utilized.

[0055] The exemplary video encoder 600 may include an intra-prediction processor 415, a motion estimation / compensation processor 612 (also referred to as an inter-prediction processor) that can assist in predicting global motion vectors in a current frame from previously encoded global motion vectors of past frames in accordance with some aspects of the present subject matter, a transform / quantization processor 616, an inverse quantization / inverse transform processor 620, an in-loop filter 624, a decoded picture buffer 628, and / or an entropy coding processor 632. Bitstream parameters may be input to the entropy coding processor 632 for inclusion in an output bitstream 636.

[0056] In operation, and continuing to refer to FIG. 6 , for each block of a frame of the input video 604, it may be determined whether to process the block via intra-picture prediction or using motion estimation / compensation. The block may be provided to the intra-prediction processor 608 or the motion estimation / compensation processor 612. If the block is to be processed via intra-prediction, the intra-prediction processor 608 may perform processing and output a predictor. If the block is to be processed via motion estimation / compensation, the motion estimation / compensation processor 612 may perform processing, including predicting a global motion vector in a current frame from previously encoded global motion vectors of past frames, if applicable, in accordance with some aspects of the present subject matter.

[0057] Continuing with reference to FIG. 6, a residual may be formed by subtracting the predictor from the input video. The residual may be received by a transform / quantization processor 616, which may perform a transform operation (e.g., a discrete cosine transform (DCT)) to produce coefficients, which may be quantized. The quantized coefficients and any associated signaling information may be provided to an entropy coding processor 632 for entropy encoding and inclusion in an output bitstream 636. The entropy encoding processor 632 may assist in encoding signaling information related to encoding the current block. Additionally, the quantized coefficients may be combined with the predictor and provided to an inverse quantization / inverse transform processor 620, which may reconstruct pixels that may be processed by an in-loop filter 624, the output of which may be stored in a decoded picture buffer 628 for use by a motion estimation / compensation processor 612, which may predict global motion vectors in a current frame from previously encoded global motion vectors of past frames in accordance with some aspects of the present subject matter.

[0058] Still referring to Figure 6, several variations have been described in detail above, but other modifications or additions are also possible. For example, in some implementations, the current block may include any symmetric block (8x8, 16x16, 32x32, 64x64, 128x128, and the like) and any asymmetric block (8x4, 16x8, and the like).

[0059] In some implementations, and continuing to refer to FIG. 6, a quadtree plus binary decision tree (QTBT) may be implemented. In QTBT, at the coding tree unit level, partition parameters of the QTBT may be dynamically derived to adapt to local characteristics without transmitting any overhead. Subsequently, at the coding unit level, a joint classifier decision tree structure may eliminate unnecessary iterations and control the risk of erroneous predictions. In some implementations, an LTR frame block update mode may be available as an additional option available per leaf node of the QTBT.

[0060] In some implementations, still referring to Figure 6, additional syntax elements may be signaled at different hierarchical levels of the bitstream. For example, a flag may be enabled throughout a sequence by including an enabled flag coded in a sequence parameter set (SPS). Furthermore, a CTU flag may be coded at the coding tree unit (CTU) level.

[0061] It should be noted that any one or more of the aspects and embodiments described herein may be conveniently implemented using digital electronic circuitry, integrated circuit networking, specially designed application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), computer hardware, firmware, software, and / or combinations thereof, as embodied and / or implemented in one or more machines (e.g., one or more computing devices utilized as user computing devices for electronic documents, one or more server devices, such as document servers, etc.) programmed according to the teachings herein, as would be apparent to those skilled in the computer arts. These various aspects or features may include implementation in one or more computer programs and / or software executable and / or interpretable on a programmable system including at least one programmable processor, which may be special-purpose or general-purpose, coupled to receive data and instructions from and transmit data and instructions to a storage system, at least one input device, and at least one output device. Appropriate software coding may be readily prepared by skilled programmers based on the teachings of the present disclosure, as would be apparent to those skilled in the software arts. The aspects and implementations discussed above that employ software and / or software modules may also include appropriate hardware to assist in implementing the machine-executable instructions of the software and / or software modules.

[0062] Such software may be a computer program product employing a machine-readable storage medium. A machine-readable storage medium may be any medium capable of storing and / or encoding sequences of instructions for execution by a machine (e.g., a computing device), causing the machine to perform any one of the methodologies and / or embodiments described herein. Examples of machine-readable storage media include, but are not limited to, magnetic disks, optical disks (e.g., CDs, CD-Rs, DVDs, DVD-Rs, etc.), magneto-optical disks, read-only memory "ROM" devices, random-access memory "RAM" devices, magnetic cards, optical cards, solid-state memory devices, EPROMs, EEPROMs, programmable logic devices (PLDs), and / or any combination thereof. As used herein, machine-readable medium is intended to include a single medium and a collection of physically separate media, such as, for example, a compact disc or a collection of one or more hard disk drives in combination with computer memory. As used herein, machine-readable storage medium does not include a transitory form of signal transmission.

[0063] Such software may also include information (e.g., data) carried in a data signal on a data carrier, such as a carrier wave. For example, machine-executable information may be included as a data carrier signal embodied in a data carrier, which signal encodes a sequence of instructions, or a portion thereof, for execution by a machine (e.g., a computing device), and any associated information (e.g., data structures and data) that causes the machine to perform any one of the methodologies and / or embodiments described herein.

[0064] Examples of computing devices include, but are not limited to, e-book reading devices, computer workstations, terminal computers, server computers, handheld devices (e.g., tablet computers, smartphones, etc.), web appliances, network routers, network switches, network bridges, any machine capable of executing a sequence of instructions that define actions to be taken by the machine, and any combination thereof. In one example, the computing device may include and / or be included within a kiosk.

[0065] 7 shows a diagrammatic representation of one embodiment of a computing device in the exemplary form of a computer system 700 upon which a set of instructions for causing a control system to implement any one or more of the aspects and / or methodologies of the present disclosure may be executed. It is also contemplated that multiple computing devices may be utilized to implement a specially configured set of instructions for causing one or more of the devices to implement any one or more of the aspects and / or methodologies of the present disclosure. Computer system 700 includes a processor 704 and a memory 708, which communicate with each other and with other components via a bus 712. Bus 712 may include any of several types of bus structures, including, but not limited to, a memory bus, a memory controller, a peripheral bus, a local bus, and any combination thereof, using any of a variety of bus architectures.

[0066] Memory 708 may include a variety of components (e.g., machine-readable media), including, but not limited to, random-access memory components, read-only components, and any combination thereof. In one embodiment, a basic input / output system 716 (BIOS), containing the basic routines that help to transfer information between elements within computer system 700, such as during start-up, may be stored in memory 708. Memory 708 may also include (e.g., stored on one or more machine-readable media) instructions (e.g., software) 720 that embody any one or more of the aspects and / or methodologies of the present disclosure. In another embodiment, memory 708 may further include any number of program modules, including, but not limited to, an operating system, one or more application programs, other program modules, program data, and any combination thereof.

[0067] Computer system 700 may also include a storage device 724. Examples of a storage device (e.g., storage device 724) include, but are not limited to, a hard disk drive, a magnetic disk drive, an optical disk drive in combination with optical media, a solid-state memory device, and any combination thereof. Storage device 724 may be connected to bus 712 by an appropriate interface (not shown). Exemplary interfaces include, but are not limited to, SCSI, Advanced Technology Attachment (ATA), Serial ATA, Universal Serial Bus (USB), IEEE 1394 (FIREWIRE®), and any combination thereof. In one embodiment, storage device 724 (or one or more of its components) may removably interface with computer system 700 (e.g., via an external port connector (not shown)). In particular, storage device 724 and associated machine-readable media 728 may provide nonvolatile and / or volatile storage of machine-readable instructions, data structures, program modules, and / or other data for computer system 700. In one embodiment, software 720 may reside, completely or partially, within machine-readable medium 728. In another embodiment, software 720 may reside, completely or partially, within processor 704.

[0068] Computer system 700 may also include input devices 732. In one embodiment, a user of computer system 700 may type commands and / or other information into computer system 700 via input devices 732. Examples of input devices 732 include, but are not limited to, an alphanumeric input device (e.g., a keyboard), a pointing device, a joystick, a gamepad, an audio input device (e.g., a microphone, a voice response system, etc.), a cursor control device (e.g., a mouse), a touchpad, an optical scanner, a video capture device (e.g., a still camera, a video camera), a touch screen, and any combination thereof. Input devices 732 may interface to bus 712 via any of a variety of interfaces (not shown), including, but not limited to, a serial interface, a parallel interface, a gameport, a USB interface, a FIREWIRE® interface, an interface directly to bus 712, and any combination thereof. Input devices 732 may include a touch screen interface, which may be part of or separate from display 736, discussed further below. The input device 732 may be utilized as a user selection device for selecting one or more graphical representations within a graphical interface such as those described above.

[0069] A user may also input commands and / or other information into computer system 700 via storage device 724 (e.g., a removable disk drive, flash drive, etc.) and / or network interface device 740. A network interface device, such as network interface device 740, may be utilized to connect computer system 700 to one or more of various networks, such as network 744, and one or more remote devices 748 connected thereto. Examples of network interface devices include, but are not limited to, a network interface card (e.g., a mobile network interface card, a LAN card), a modem, and any combination thereof. Examples of networks include, but are not limited to, a wide area network (e.g., the Internet, an enterprise network), a local area network (e.g., a network associated with an office, building, campus, or other relatively small geographic space), a telephone network, a data network associated with a telephone / voice provider (e.g., a mobile communications provider's data and / or voice network), a direct connection between two computing devices, and any combination thereof. A network, such as network 744, may employ wired and / or wireless modes of communication. In general, any network topology may be used. Information (eg, data, software 720 , etc.) may be communicated to and / or from computer system 700 via network interface device 740 .

[0070] Computer system 700 may further include a video display adapter 752 for communicating images displayable on a display device, such as display device 736. Examples of a display device include, but are not limited to, a liquid crystal display (LCD), a cathode ray tube (CRT), a plasma display, a light emitting diode (LED) display, and any combination thereof. Display adapter 752 and display device 736 may be utilized in combination with processor 704 to provide graphical representations of aspects of the present disclosure. In addition to a display device, computer system 700 may include one or more other peripheral output devices, including, but not limited to, audio speakers, a printer, and any combination thereof. Such peripheral output devices may be connected to bus 712 via a peripheral interface 756. Examples of a peripheral interface include, but are not limited to, a serial port, a USB connection, a FIREWIRE® connection, a parallel connection, and any combination thereof.

[0071] The foregoing is a detailed description of illustrative embodiments of the present invention. Various modifications and additions may be made without departing from the spirit and scope of the present invention. Features of each of the various embodiments described above may be combined, as appropriate, with features of other described embodiments to provide a combination of features in a related new embodiment. Moreover, while the foregoing describes several separate embodiments, what has been described herein merely illustrates the application of the principles of the present invention. In addition, although certain methods herein may be illustrated and / or described as being performed in a particular order, the order may be highly variable among those skilled in the art to achieve the embodiments as disclosed herein. Therefore, this description is intended to be taken as example only and is not intended to otherwise limit the scope of the present invention.

[0072] In the above description and in the claims, phrases such as "at least one of" or "one or more of" may appear and be followed by a conjunctive listing of elements or features. The term "and / or" may also appear within a listing of two or more elements or features. Unless otherwise implicitly or explicitly contradicted by the context in which such phrase is used, this is intended to mean any of the listed elements or features individually or any of the recited elements or features in combination with any of the other recited elements or features. For example, the phrases "at least one of A and B," "one or more of A and B," and "A and / or B" are intended to mean "A alone, B alone, or A and B together," respectively. A similar interpretation is also intended with respect to listings containing three or more items. For example, the phrases "at least one of A, B, and C," "one or more of A, B, and C," and "A, B, and / or C" are intended to mean "A alone, B alone, C alone, A and B together, A and C together, B and C together, or A, B, and C together," respectively. Additionally, use of the term "based on" above and in the claims is intended to mean "based at least on," so that unrecited features or elements also qualify as permissible.

[0073] The subject matter described herein can be embodied in systems, devices, methods, and / or articles, depending on the desired configuration. The implementations described in the foregoing description do not represent all consistent implementations of the subject matter described herein. Instead, they are merely some examples consistent with aspects related to the described subject matter. While some variations have been described in detail above, other modifications or additions are possible. In particular, additional features and / or variations can be provided in addition to those described herein. For example, the implementations described above can be directed to various combinations and subcombinations of the disclosed features and / or combinations and subcombinations of some additional features disclosed above. In addition, the logic flow depicted in the accompanying figures and / or described herein does not necessarily require the particular order shown or sequential order to achieve desirable results. Other implementations may be within the scope of the following claims.

Claims

1. A decoder, comprising: A circuitry comprising: receiving a bitstream, the bitstream including: a first coded picture; first information for determining a first plurality of control point motion vector predictors for affine motion compensation including motion vector difference information for a first plurality of control point motion vector predictors and a first index to a first reference picture in a reference picture list; a second coded picture; and second information for determining a second plurality of control point motion vector predictors for affine motion compensation including an indication of absence of motion vector difference information for a second plurality of motion vector predictors and a second index to a second reference picture in the reference picture list; obtaining the first plurality of motion vector predictors using the first information, the first plurality of motion vector predictors being obtained from motion vectors used in decoding the first reference picture; and combining the first plurality of motion vector predictors with the motion vector difference information to form a first plurality of control point motion vectors for affine motion compensation for the first picture; forming a second plurality of control point motion vectors for affine motion compensation for the second picture by obtaining the second plurality of motion vector predictors using the second information, wherein the second plurality of motion vector predictors are obtained from motion vectors used in decoding the second reference picture, and there is no motion vector difference information for the second plurality of control point motion vectors as indicated in the bitstream; a network configured to: A decoder comprising:

2. A decoder as described in claim 1, wherein the affine motion compensation is six-parameter affine motion compensation, the plurality of control point motion vectors for the first picture include three control point motion vectors, and the plurality of control point motion vectors for the second picture include three control point motion vectors.

3. A decoder as described in claim 1, wherein the affine motion compensation is four-parameter affine motion compensation, the plurality of control point motion vectors for the first picture include two control point motion vectors, and the plurality of control point motion vectors for the second picture include two control point motion vectors.

4. A decoder as described in claim 1, wherein the first reference picture and the second reference picture are the same reference picture.

5. A method for decoding a bitstream, comprising: receiving a bitstream, the bitstream including: a first coded picture; first information for determining a first plurality of control point motion vector predictors for affine motion compensation including motion vector difference information for a first plurality of control point motion vector predictors and a first index to a first reference picture in a reference picture list; a second coded picture; and second information for determining a second plurality of control point motion vector predictors for affine motion compensation including an indication of absence of motion vector difference information for a second plurality of motion vector predictors and a second index to a second reference picture in the reference picture list; obtaining the first plurality of motion vector predictors using the first information, the first plurality of motion vector predictors being obtained from motion vectors used in decoding the first reference picture; and combining the first plurality of motion vector predictors with the motion vector difference information to form a first plurality of control point motion vectors for affine motion compensation for the first picture; forming a second plurality of control point motion vectors for affine motion compensation for the second picture by obtaining the second plurality of motion vector predictors using the second information, wherein the second plurality of motion vector predictors are obtained from motion vectors used in decoding the second reference picture, and there is no motion vector difference information for the second plurality of control point motion vectors as indicated in the bitstream; A method comprising:

6. The method described in claim 5, wherein the affine motion compensation is six-parameter affine motion compensation, the plurality of control point motion vectors for the first picture include three control point motion vectors, and the plurality of control point motion vectors for the second picture include three control point motion vectors.

7. The method described in claim 5, wherein the affine motion compensation is four-parameter affine motion compensation, the plurality of control point motion vectors for the first picture include two control point motion vectors, and the plurality of control point motion vectors for the second picture include two control point motion vectors.

8. The method described in claim 5, wherein the first reference picture and the second reference picture are the same reference picture.

9. A method for encoding a bitstream, comprising: receiving a video signal; generating a bitstream representing the video signal, the bitstream including a first coded picture, first information for determining a first plurality of control point motion vector predictors for affine motion compensation including motion vector difference information for a first plurality of control point motion vector predictors and a first index to a first reference picture in a reference picture list, a second coded picture, and second information for determining a second plurality of control point motion vector predictors for affine motion compensation including an indication of absence of motion vector difference information for a second plurality of motion vector predictors and a second index to a second reference picture in the reference picture list; the encoding method further comprising: obtaining the first plurality of motion vector predictors using the first information, the first plurality of motion vector predictors being obtained from motion vectors used in decoding the first reference picture; and combining the first plurality of motion vector predictors with the motion vector difference information to form a first plurality of control point motion vectors for affine motion compensation for the first picture; forming a second plurality of control point motion vectors for affine motion compensation for the second picture by obtaining the second plurality of motion vector predictors using the second information, wherein the second plurality of motion vector predictors are obtained from motion vectors used in decoding the second reference picture, and there is no motion vector difference information for the second plurality of control point motion vectors as indicated in the bitstream; configuring the bitstream for decoding by a method comprising:

10. The method described in claim 9, wherein the affine motion compensation is six-parameter affine motion compensation, the plurality of control point motion vectors for the first picture include three control point motion vectors, and the plurality of control point motion vectors for the second picture include three control point motion vectors.

11. The method described in claim 9, wherein the affine motion compensation is four-parameter affine motion compensation, the plurality of control point motion vectors for the first picture include two control point motion vectors, and the plurality of control point motion vectors for the second picture include two control point motion vectors.

12. The method of claim 9, wherein the first reference picture and the second reference picture are the same reference picture.

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