Derivation of processing area for parallel processing in video coding

A video coder may determine a partitioning of a current picture of the video data into a plurality of partition blocks. The video coder may determine a plurality of processing areas in a unit in the current picture having sizes, where an average size of all of the plurality of processing areas in the unit is greater than or equal to a parameter N, and where determining the plurality of processing areas in the unit includes defining a processing area of the plurality of processing areas that has a size that fits two or more adjacent partition blocks of the plurality of adjacent blocks. The video coder may independently code coding units (CUs) within the processing area having the merged two or more adjacent partition blocks.

TECHNICAL FIELD

BACKGROUND

SUMMARY

In general, this disclosure describes techniques for selecting processing areas, such as merge estimation regions, for pictures of video data in a potentially more flexible manner. The techniques of this disclosure may enable different neighboring partition blocks to be combined together to form a processing area and may also loosen the restriction on the size of processing areas. For example, processing areas in a picture may not have to each be the same area size as defined by coding parameters of a video codec. Rather, the average size of the processing areas may be constrained to be larger than or equal to the area size defined by coding parameters. Accordingly, the techniques described herein may be able to achieve higher coding performance by increasing the capability of a video coder to encode or decode blocks in parallel.

In one example, a method for coding video data includes determining a partitioning of a current picture of the video data into a plurality of partition blocks. The method further includes determining a plurality of processing areas in a unit in the current picture having sizes, wherein an average size of all of the plurality of processing areas in the unit is greater than or equal to a parameter N, and wherein determining the plurality of processing areas in the unit includes defining a processing area of the plurality of processing areas that has a size that fits two or more adjacent partition blocks of the plurality of partition blocks. The method further includes independently coding coding units (CUs) within the processing area having the merged two or more adjacent partition blocks.

In another example, a video coding device includes a memory to store video data. The device further includes one or more processors implemented in circuitry and configured to: determine a partitioning of a current picture of the video data into a plurality of partition blocks; determine a plurality of processing areas in a unit in the current picture having sizes, wherein an average size of all of the plurality of processing areas in the unit is greater than or equal to a parameter N, and wherein determining the plurality of processing areas in the unit includes defining a processing area of the plurality of processing areas that has a size that fits two or more adjacent partition blocks of the plurality of partition blocks; and independently code coding units (CUs) within the processing area having the merged two or more adjacent partition blocks.

In another example, a device for coding video data includes means for determining a partitioning of a current picture of the video data into a plurality of partition blocks. The device further includes means for determining a plurality of processing areas in a unit in the current picture having sizes, wherein an average size of all of the plurality of processing areas in the unit is greater than or equal to a parameter N, and wherein the means for determining the plurality of processing areas in the unit includes means defining a processing area of the plurality of processing areas that has a size that fits two or more adjacent partition blocks of the plurality of partition blocks. The device further includes means for independently coding coding units (CUs) within the processing area having the merged two or more adjacent partition blocks.

In another example, a computer-readable storage medium having stored thereon instructions that, when executed, cause one or more processors configured to code video data to: determine a partitioning of a current picture of the video data into a plurality of partition blocks; determine a plurality of processing areas in a unit in the current picture having sizes, wherein an average size of all of the plurality of processing areas in the unit is greater than or equal to a parameter N, and wherein determining the plurality of processing areas in the unit includes defining a processing area of the plurality of processing areas that has a size that fits two or more adjacent partition blocks of the plurality of partition blocks; and independently code coding units (CUs) within the processing area having the merged two or more adjacent partition blocks.

DETAILED DESCRIPTION

Aspects of the present disclosure describe techniques for selecting processing areas for pictures of video data in a way that increases the number of blocks in pictures of video data that may be processed in parallel. During the video coding process, a picture of video data may be partitioned into partition blocks, where each partition block is a portion of the picture. When the partition blocks are processed as part of the video coding process, dependencies between neighboring partition blocks may decrease the performance of the video coding process. The techniques of this disclosure may allow different partition blocks to be combined to form a processing area to resolve such dependencies between neighboring blocks to thereby increase the performance of the video coding process, and the techniques of this disclosure may also apply constraints to processing areas in a way that loosen one or more restrictions on the size of processing areas.

The way that a video coder derives candidate lists for blocks, such as merge candidate lists, may potentially introduce dependencies between neighboring blocks in a picture of video data because a neighboring block may be, for example, a merge candidate for another neighboring block. Due to such dependencies between neighboring blocks, a video coder may not necessarily be able to process neighboring blocks in parallel, thereby introducing a potential bottleneck in the video coding process. For example, a video coder may not be able to determine, for a block, whether a neighboring block is a merge candidate until motion data is available for the neighboring block, such that performing motion estimation for the block may be dependent upon determining motion data for the neighboring block.

A video coder may use the concept of a merge estimation region (MER) to reduce the local interdependency between small blocks and to thereby enable parallel merge candidate derivation for those blocks. A MER may indicate a region in which merge candidate lists can be independently derived for blocks within the region by checking whether a candidate block is in the same MER as a current block. If a candidate block is in the same MER as the current block, the candidate block is not included in the merge candidate list for the current block, so that the motion data for the candidate block does not need to be available at the time of constructing the merge candidate list for the current block. In this way, blocks within the same MER may be coded in parallel.

One example of a MER mechanism uses square MER grids (e.g., 4×4, 8×8, 16×16, 32×32, and 64×64 grids), and each MER may be required cover all coding units that overlap with the MER. However, such a MER mechanism may not be flexible enough for actual encoder/decoder design.

Another example of a MER mechanism uses area-based MER, may be more flexible than fixed square MER grids. In area-based MER, one specific size of N can be defined as an MER area, and once a coding tree unit is split to the size of N, a corresponding partition block of size N is considered as a MER, thereby allowing parallel processing of all coding units within the partition block. However, area-based MER may not be flexible enough to be applicable to the different ways in which a partition can be split, such as via quad-tree splitting, binary-tree splitting, ternary-tree splitting, and the like.

In particular, the boundaries of area-based MERs may not always be able to match partition boundaries of partition blocks. For example, if the size of an area-based MER is specified to be 32, and if a partition of size 64 is split into 4 sub-partitions each of size 16 via quad-tree splitting, there may be no partition block that can exactly match the MER block having a size of 32. Thus, the area of a MER may have to be properly selected in order to allow parallel processing inside the MER and to reduce the sacrifice of rate-distortion performance as much as possible.

Aspects of the present disclosure describes techniques to determine the sizes and shapes of processing areas, such as a MER, of a picture of video data in a way that is potentially more flexible than the approaches discussed above, thereby enabling greater performance gains in video coding by increasing the amount of parallel processing of partition blocks that may be performed. In some examples, the techniques include merging several adjacent partition blocks into a processing area if the processing area does not exactly match the boundary of a single partition block, and corresponding rules can be applied to all partition blocks within the processing area to enable parallel processing of the partition blocks within the processing area.

Further, in some examples, the techniques also include the sizes of processing areas to be different from an area size defined by a parameter N. Instead, processing areas within a unit may be constrained to have an average area size that is greater than or equal to the parameter N, so that individual processing areas may have sizes that are greater or less than the parameter N as long as the average area size is greater than or equal to the parameter N, thereby ensuring that parallel processing capabilities do not decrease due to such non-standard sized areas.

In accordance with aspects of the present disclosure, a video coder may determine a partitioning of a current picture of the video data into a plurality of partition blocks. The video coder may determine a plurality of processing areas in a unit in the current picture having sizes, wherein an average size of all of the plurality of processing areas in the unit is greater than or equal to a parameter N, and wherein determining the plurality of processing areas in the unit includes defining a processing area of the plurality of processing areas that has a size that fits two or more adjacent partition blocks of the plurality of partition blocks. The video coder may independently code coding units (CUs) within the processing area having the merged two or more adjacent partition blocks.

In some examples, source device102may output encoded video data to file server114or another intermediate storage device that may store the encoded video generated by source device102. Destination device116may access stored video data from file server114via streaming or download. File server114may be any type of server device capable of storing encoded video data and transmitting that encoded video data to the destination device116. File server114may represent a web server (e.g., for a website), a File Transfer Protocol (FTP) server, a content delivery network device, or a network attached storage (NAS) device. Destination device116may access encoded video data from file server114through any standard data connection, including an Internet connection. This may include a wireless channel (e.g., a Wi-Fi connection), a wired connection (e.g., digital subscriber line (DSL), cable modem, etc.), or a combination of both that is suitable for accessing encoded video data stored on file server114. File server114and input interface122may be configured to operate according to a streaming transmission protocol, a download transmission protocol, or a combination thereof.

Although not shown inFIG. 1, in some examples, video encoder200and video decoder300may each be integrated with an audio encoder and/or audio decoder, and may include appropriate MUX-DEMUX units, or other hardware and/or software, to handle multiplexed streams including both audio and video in a common data stream. If applicable, MUX-DEMUX units may conform to the ITU H.223 multiplexer protocol, or other protocols such as the user datagram protocol (UDP).

Video encoder200and video decoder300may operate according to a video coding standard, such as ITU-T H.265, also referred to as High Efficiency Video Coding (HEVC) or extensions thereto, such as the multi-view and/or scalable video coding extensions. Alternatively, video encoder200and video decoder300may operate according to other proprietary or industry standards, such as the Joint Exploration Test Model (JEM) or ITU-T H.266, also referred to as Versatile Video Coding (VVC). A recent draft of the VVC standard is described in Bross, et al. “Versatile Video Coding (Draft 6),” Joint Video Experts Team (JVET) of ITU-T SG 16 WP 3 and ISO/IEC JTC 1/SC 29/WG 11, 15thMeeting: Gothenburg, SE, 3-12 Jul. 2019, JVET-02001-vE (hereinafter “VVC Draft 6”). The techniques of this disclosure, however, are not limited to any particular coding standard.

In some examples, a tile may be partitioned into multiple bricks, each of which may include one or more CTU rows within the tile. A tile that is not partitioned into multiple bricks may also be referred to as a brick. However, a brick that is a true subset of a tile may not be referred to as a tile.

The bricks in a picture may also be arranged in a slice. A slice may be an integer number of bricks of a picture that may be exclusively contained in a single network abstraction layer (NAL) unit. In some examples, a slice includes either a number of complete tiles or only a consecutive sequence of complete bricks of one tile.

As mentioned above, a video coder (e.g., video encoder200or video decoder300) may apply inter prediction to generate a prediction block for a video block of a current picture. For instance, the video coder may apply inter prediction to generate a prediction block for a prediction block of a CU. If the video coder applies inter prediction to generate a prediction block, the video coder generates the prediction block based on decoded samples of one or more reference pictures. Typically, the reference pictures are pictures other than the current picture. In some video coding specifications, a video coder may also treat the current picture itself as a reference picture. The video coder may determine one or more reference picture lists. Each of the reference picture lists includes zero or more reference pictures. One of the reference picture lists may be referred to as Reference Picture List 0 (RefPicList0) and another reference picture list may be referred to as Reference Picture list 1 (RefPicList1).

The video coder may apply uni-directional inter prediction or bi-directional inter prediction to generate a prediction block. When the video coder applies uni-directional inter prediction to generate a prediction block for a video block, the video coder determines a single reference block for the video block based on a samples of a single reference picture. The reference block may be a block of samples that is similar to the prediction block. Furthermore, when the video coder applies uni-directional inter prediction, the video coder may set the prediction block equal to the reference block. When the video coder applies bi-directional inter prediction to generate a prediction block for a video block, the video coder determines two reference blocks for the video block. In some examples, the two reference blocks are in reference pictures in different reference picture lists. Additionally, when the video coder applies bi-direction inter-prediction, the video coder may determine the prediction block based on the two reference blocks. For instance, the video coder may determine the prediction block such that each sample of the prediction block is a weighted average of corresponding samples of the two reference blocks. Reference list indicators may be used to indicate which of the reference picture lists include reference pictures used for determining reference blocks.

As mentioned above, a video coder may determine a reference block based on samples of a reference picture. In some examples, the video coder may determine the reference block such that each sample of the reference block is equal to a sample of the reference picture. In some examples, as part of determining a reference block, the video coder may interpolate samples of the reference block from samples of the reference picture. For example, the video coder may determine that a sample of the prediction block is a weighted average of two or more samples of the reference picture.

In some examples, when video encoder200performs uni-directional inter prediction for a current block of a current picture, video encoder200identifies a reference block within one or more reference pictures in one of the reference picture lists. For instance, video encoder200may search for a reference block within the one or more reference pictures in the reference picture list. In some examples, video encoder200uses a mean squared error or other metric to determine the similarity between the reference block and the current block Furthermore, video encoder200may determine motion parameters for the current block. The motion parameters for the current block may include a motion vector and a reference index. The motion vector may indicate a spatial displacement between a position of the current block within the current picture and a position of the reference block within the reference picture. The reference index indicates a position within the reference picture list of the reference frame that contains the reference picture list. The prediction block for the current block may be equal to the reference block.

When video encoder200performs bi-directional inter prediction for a current block of a current picture, video encoder200may identify a first reference block within reference pictures in a first reference picture list (“list 0”) and may identify a second reference block within reference pictures in a second reference picture list (“list 1”). For instance, video encoder200may search for the first and second reference blocks within the reference pictures in the first and second reference picture lists, respectively. Video encoder200may generate, based at least in part on the first and the second reference blocks, the prediction block for the current block. In addition, video encoder200may generate a first motion vector that indicates a spatial displacement between the current block and the first reference block. Video encoder200may also generate a first reference index that identifies a location within the first reference picture list of the reference picture that contains the first reference block. Furthermore, video encoder200may generate a second motion vector that indicates a spatial displacement between the current block and the second reference block. Video encoder200may also generate a second reference index that identifies a location within the second reference picture list of the reference picture that includes the second reference block.

When video encoder200performs uni-directional inter prediction on a current block, video decoder300may use the motion parameters of the current block to identify the reference block of the current block. Video decoder300may then generate the prediction block of the current block based on the reference block. When video encoder200performs bi-directional inter prediction to determine a prediction block for a current block, video decoder300may use the motion parameters of the current block to determine two reference blocks. Video decoder300may generate the prediction block of the current block based on the two reference samples of the current block.

Video encoder200may signal motion parameters of a block in various ways. Such motion parameters may include motion vectors, reference indexes, reference picture list indicators, and/or other data related to motion. In some examples, video encoder200and video decoder300may use motion prediction to reduce the amount of data used for signaling motion parameters. Motion prediction may comprise the determination of motion parameters of a block (e.g., a PU, a CU, etc.) based on motion parameters of one or more other blocks. There are various types of motion prediction. For instance, merge mode and advanced motion vector prediction (AMVP) mode are two types of motion prediction.

In merge mode, video encoder200generates a candidate list. The candidate list includes a set of candidates that indicate the motion parameters of one or more source blocks. The source blocks may spatially or temporally neighbor a current block. Furthermore, in merge mode, video encoder200may select a candidate from the candidate list and may use the motion parameters indicated by the selected candidate as the motion parameters of the current block. Video encoder200may signal the position in the candidate list of the selected candidate. Video decoder300may determine, based on information obtained from a bitstream, the index into the candidate list. In addition, video decoder300may generate the same candidate list and may determine, based on the index, the selected candidate. Video decoder300may then use the motion parameters of the selected candidate to generate a prediction block for the current block.

Skip mode is similar to merge mode. In skip mode, video encoder200and video decoder300generate and use a candidate list in the same way that video encoder200and video decoder300use the candidate list in merge mode. However, when video encoder200signals the motion parameters of a current block using skip mode, video encoder200does not signal any residual data for the current block. Accordingly, video decoder300may determine a prediction block for the current block based on one or more reference blocks indicated by the motion parameters of a selected candidate in the candidate list. Video decoder30may then reconstruct samples in a coding block of the current block such that the reconstructed samples are equal to corresponding samples in the prediction block of the current block.

AMVP mode is similar to merge mode in that video encoder200may generate a candidate list for a current block and may select a candidate from the candidate list. However, for each respective reference block used in determining a prediction block for the current block, video encoder200may signal a respective motion vector difference (MVD) for the current block, a respective reference index for the current block, and a respective candidate index indicating a selected candidate in the candidate list. An MVD for a block may indicate a difference between a motion vector of the block and a motion vector of the selected candidate. The reference index for the current block indicates a reference picture from which a reference block is determined.

Furthermore, when AMVP mode is used, for each respective reference block used in determining a prediction block for the current block, video decoder300may determine an MVD for the current block, a reference index for the current block, and a candidate index and a motion vector prediction (MVP) flag. Video decoder300may generate the same candidate list and may determine, based on the candidate index, a selected candidate in the candidate list. As before, this candidate list may include motion vectors of neighboring blocks that are associated with the same reference index as well as a temporal motion vector predictor which is derived based on the motion parameters of the neighboring block of the co-located block in a temporal reference picture. Video decoder300may recover a motion vector of the current block by adding the MVD to the motion vector indicated by the selected AMVP candidate. That is, video decoder300may determine, based on a motion vector indicated by the selected AMVP candidate and the MVD, the motion vector of the current block. Video decoder300may then use the recovered motion vector or motion vectors of the current block to generate prediction blocks for the current block.

When a video coder (e.g., video encoder200or video decoder300) generates an AMVP candidate list for a current block, the video coder may derive one or more AMVP candidates based on the motion parameters of reference blocks (e.g., spatially-neighboring blocks) that contain locations that spatially neighbor the current PU and one or more AMVP candidates based on motion parameters of PUs that temporally neighbor the current PU. The candidate list may include motion vectors of reference blocks that are associated with the same reference index as well as a temporal motion vector predictor which is derived based on the motion parameters (i.e., motion parameters) of the neighboring block of the co-located block in a temporal reference picture. A candidate in a merge candidate list or an AMVP candidate list that is based on the motion parameters of a reference block that temporally neighbors a current block. This disclosure may use the term “temporal motion vector predictor” to refer to a block that is in a different time instance than the current block and is used for motion vector prediction.

In HEVC, the concept of merge estimation region (MER) are introduced to reduce the local interdependency between small blocks so that parallel merge candidate derivation for those blocks is allowed. The MER mechanism adopted by HEVC uses fixed square MER grids. Each MER must cover all CUs that overlaps with the MER, thus the MER mechanism is not flexible enough for actual encoder/decoder design.

Area-based MER is more flexible, one specific size of N can be defined as MER area and once a coding tree unit is split to the size of N, the corresponding partition block is considered as MER and parallel processing of all CUs within the partition block is allowed. However, the area-based MER has a problem in that the way to split a coding tree unit (CTU) can be very flexible. For example, in versatile video coding (VVC), some different kinds of splitting such as quad-tree partitioning, binary-tree partitioning, and ternary-tree partitioning are allowed. In quad-tree partitioning, a block is split into four sub-blocks. In binary-tree partitioning, a block is split into two sub-blocks. In ternary-tree partitioning, a block is split into three sub-blocks.

Area based MER boundaries may not always be partition boundaries. For example, in the example ofFIG. 8, MER size is specified to 32 but the partition of size 64 is split into 4 sub-partitions of size 16 via a quad-tree splitting. Then, there is no partition block that can exactly match the MER block. The MER area needs to be properly selected to allow parallel processing inside MER and reduce the sacrifice of rate-distortion performance as much as possible.

This disclosure describes techniques to determine a processing area based on the parameter N. In some examples, if the processing area cannot fit exactly to the boundary of a partition block, several adjacent partition blocks may be merged to the processing area and corresponding rules can be applied to all CUs within the area so that parallel processing is allowed. In one example, a parameter N is defined as the number of samples included in the processing area. In another example the parameter N is defined as the number of minimum CU block sizes covered by the processing area. In this example, if the parameter N has a value of 16, and if the minimum CU block size is 4×4, then the processing area may be a block having a size of 16×16. There may be alternative definitions of parameter N to which the techniques of this disclosure are still applicable.

The process for defining the processing area can be applied to MER, shared candidate list (in which all CUs within a processing area share the same merge candidate list), and can be applied to other tools such as AMVP, affine mode, etc. In one example, such tools are the tools that require deriving a candidate list based on neighbor information.

Based on the condition of block partitioning, the final processing area size may be different from the area size defined by the parameter N, and therefore be a non-standard sized processing area. One example rule that may be applied to those non-standard sized processing areas to guarantee the parallel capability of processing does not decrease due to the non-standard sized areas: All processing areas have an average area size that is greater than or equal to N. As a few examples, the unit which has average area size no less than the defined area can be a picture, a slice, a tile, a CTU, a partition block of size 2*N or other predefined regions.

In one example, to accomplish the rule in cases when size of processing area does not fit the partitioning, one processing area can be defined larger than a desired area defined by the parameter N, and next processing area is defined as being smaller than the desired area. In such case, average size of processing areas is not decreased, and parallel processing capability is maintained. How the larger and smaller areas are defined may depend on the partition type.

Some examples of the techniques of this disclosure can be as follows.

For example, for a quad-tree splitting, processing area sizes can be specified as 32 samples, 64 samples, 128 samples, 256 samples, etc. When the total partition size is 2*N (the 4 sub-partitions are all of size N/2), the processing area size may be defined as N. A rectangular area which includes or consists of 2 horizontally adjacent sub-partitions can be treated as the first processing area. As another example, a rectangular area including or consisting of 2 vertically adjacent sub-partitions can be treated as the first processing area. The second rectangular partition is treated as the second processing area. The processing areas for the two examples mentioned in this paragraph are shown inFIG. 5AandFIG. 5B.

For another example, for horizontal ternary-tree splitting, the size of processing area can be specified as 32 samples, 64 samples, 128 samples, 256 samples, etc. When the total partition size is 2*N and the 3 sub-partitions are of size N/2, N and N/2, the center sub-partition is combined with the left sub-partition to form the first processing area and the right sub-partition is treated as the second processing area. In this example, the 2 areas corresponding to the 2*N sized partition block are guaranteed to have an average size of N. As another example, the center sub-partition is combined with the right sub-partition to form the first processing area and the left sub-partition is the second processing area. In this example, the two areas corresponding to the 2*N sized partition block are also guaranteed to have an average size of N. The processing areas for the two examples mentioned in this paragraph are shown inFIG. 7AandFIG. 7B.

For another example, vertical ternary-tree splitting is used. The processing area sizes can be specified as 32 samples, 64 samples, 128 samples, 256 samples, etc. When the total partition size is 2*N and the 3 sub-partitions are of size N/4, N/2 and N/4. The center sub-partition is combined with the top sub-partition to form the first processing area and the bottom sub-partition is treated as the second processing area. In this example, the two processing areas corresponding to the 2*N sized partition block are guaranteed to have an average size of N. As another example, the center sub-partition is combined with the bottom sub-partition to form the first processing area and the top sub-partition is the second processing area. In this example, the two processing areas corresponding to the 2*N sized partition block are also guaranteed to have an average size of N. The processing areas for the two examples mentioned in the paragraph are shown inFIG. 6AandFIG. 6B.

Similar method can be applied to any other partition types. For example, when a partitions of size 2*N is split into four horizontal sub-partitions each of size N/2, or is split into four vertical sub-partitions each of size N/2, two processing areas each of size N may each combine two of the four sub-partitions. Alternatively, one processing area of size 3N/2 may combine three adjacent sub-partitions to form the processing area while another processing area of size N/2 may contain the remaining sub-partition.

There may be a case when a candidate in a shared candidate list is derived from the bottom-right corner of the processing area. In one example, such candidate can be a temporal motion vector predictor (TMVP). In other words, a video coder may derive a temporal motion vector predictor based on motion parameters of a reference block, where the reference block in a reference picture and covers a location within the reference picture that is collocated with a location immediately below and right of the bottom-right corner of the processing area. However, some parts of the processing area can be located outside of a picture boundary. In this case, the bottom-right block (i.e., a reference block collocated with a location immediately below and right of the bottom-right corner of the processing area) may not be available. In this case, the center of the processing area can be used to derive the candidate. In other words, a video coder may derive a temporal motion vector predictor based on motion parameters of a reference block, where the reference block is in a reference picture and covers a location within the reference picture that is collocated with a center location of the processing area. However, the techniques for using the center of the processing area to derive the candidate may be different from temporal motion vector prediction in HEVC. For example, a video coder may need to check whether the center location of the processing area is located within the picture boundaries, and if the center location is outside of the picture boundaries then such candidate (e.g., a TMVP) is not available. The center location is used as an example, and any other location within the processing area can be used instead. In the HEVC case, a block always fits the picture boundary and a center block is always located within the picture boundaries.

In accordance with the techniques of this disclosure, a video coder such as video encoder200or video decoder300shown inFIG. 1, may determine a partitioning of a current picture of the video data into a plurality of partition blocks. The video coder may determine a plurality of processing areas in a unit in the current picture having sizes, wherein an average size of all of the plurality of processing areas in the unit is greater than or equal to a parameter N, and wherein determining the plurality of processing areas in the unit includes defining a processing area of the plurality of processing areas that has a size that fits two or more adjacent partition blocks of the plurality of partition blocks. The video coder may independently code coding units (CUs) within the processing area having the merged two or more adjacent partition blocks.

FIGS. 2A and 2Bare conceptual diagrams illustrating an example quadtree binary tree (QTBT) structure130, and a corresponding coding tree unit (CTU)132. The solid lines represent quadtree splitting, and dotted lines indicate binary tree splitting. In each split (i.e., non-leaf) node of the binary tree, one flag is signaled to indicate which splitting type (i.e., horizontal or vertical) is used, where 0 indicates horizontal splitting and 1 indicates vertical splitting in this example. For the quadtree splitting, there is no need to indicate the splitting type, because quadtree nodes split a block horizontally and vertically into 4 sub-blocks with equal size. Accordingly, video encoder200may encode, and video decoder300may decode, syntax elements (such as splitting information) for a region tree level of QTBT structure130(i.e., the solid lines) and syntax elements (such as splitting information) for a prediction tree level of QTBT structure130(i.e., the dashed lines). Video encoder200may encode, and video decoder300may decode, video data, such as prediction and transform data, for CUs represented by terminal leaf nodes of QTBT structure130.

In general, CTU132ofFIG. 2Bmay be associated with parameters defining sizes of blocks corresponding to nodes of QTBT structure130at the first and second levels. These parameters may include a CTU size (representing a size of CTU132in samples), a minimum quadtree size (MinQTSize, representing a minimum allowed quadtree leaf node size), a maximum binary tree size (MaxBTSize, representing a maximum allowed binary tree root node size), a maximum binary tree depth (MaxBTDepth, representing a maximum allowed binary tree depth), and a minimum binary tree size (MinBTSize, representing the minimum allowed binary tree leaf node size).

The root node of a QTBT structure corresponding to a CTU may have four child nodes at the first level of the QTBT structure, each of which may be partitioned according to quadtree partitioning. That is, nodes of the first level are either leaf nodes (having no child nodes) or have four child nodes. The example of QTBT structure130represents such nodes as including the parent node and child nodes having solid lines for branches. If nodes of the first level are not larger than the maximum allowed binary tree root node size (MaxBTSize), then the nodes can be further partitioned by respective binary trees. The binary tree splitting of one node can be iterated until the nodes resulting from the split reach the minimum allowed binary tree leaf node size (MinBTSize) or the maximum allowed binary tree depth (MaxBTDepth). The example of QTBT structure130represents such nodes as having dashed lines for branches. The binary tree leaf node is referred to as a coding unit (CU), which is used for prediction (e.g., intra-picture or inter-picture prediction) and transform, without any further partitioning. As discussed above, CUs may also be referred to as “video blocks” or “blocks.”

In one example of the QTBT partitioning structure, the CTU size is set as 128×128 (luma samples and two corresponding 64×64 chroma samples), the MinQTSize is set as 16×16, the MaxBTSize is set as 64×64, the MinBTSize (for both width and height) is set as 4, and the MaxBTDepth is set as 4. The quadtree partitioning is applied to the CTU first to generate quad-tree leaf nodes. The quadtree leaf nodes may have a size from 16×16 (i.e., the MinQTSize) to 128×128 (i.e., the CTU size). If the leaf quadtree node is 128×128, the leaf quadtree node will not be further split by the binary tree, because the size exceeds the MaxBTSize (i.e., 64×64, in this example). Otherwise, the leaf quadtree node will be further partitioned by the binary tree. Therefore, the quadtree leaf node is also the root node for the binary tree and has the binary tree depth as 0. When the binary tree depth reaches MaxBTDepth (4, in this example), no further splitting is permitted. When the binary tree node has a width equal to MinBTSize (4, in this example), it implies no further horizontal splitting is permitted. Similarly, a binary tree node having a height equal to MinBTSize implies no further vertical splitting is permitted for that binary tree node. As noted above, leaf nodes of the binary tree are referred to as CUs, and are further processed according to prediction and transform without further partitioning.

FIG. 3is a block diagram illustrating an example video encoder200that may perform the techniques of this disclosure.FIG. 3is provided for purposes of explanation and should not be considered limiting of the techniques as broadly exemplified and described in this disclosure. For purposes of explanation, this disclosure describes video encoder200in the context of video coding standards such as the HEVC video coding standard and the H.266 video coding standard in development. However, the techniques of this disclosure are not limited to these video coding standards and are applicable generally to video encoding and decoding.

In the example ofFIG. 3, video encoder200includes video data memory230, mode selection unit202, residual generation unit204, transform processing unit206, quantization unit208, inverse quantization unit210, inverse transform processing unit212, reconstruction unit214, filter unit216, decoded picture buffer (DPB)218, and entropy encoding unit220. Any or all of video data memory230, mode selection unit202, residual generation unit204, transform processing unit206, quantization unit208, inverse quantization unit210, inverse transform processing unit212, reconstruction unit214, filter unit216, DPB218, and entropy encoding unit220may be implemented in one or more processors or in processing circuitry. For instance, the units of video encoder200may be implemented as one or more circuits or logic elements as part of hardware circuitry, or as part of a processor, ASIC, or FPGA. Moreover, video encoder200may include additional or alternative processors or processing circuitry to perform these and other functions.

As part of determining motion vectors for blocks, motion estimation unit222may construct merge candidate lists for blocks. Construction merge candidate lists for blocks may potentially introduce dependencies between neighboring blocks in a picture of video data because a neighboring block may be a merge candidate for another neighboring block. Due to such dependencies between neighboring blocks, merge candidate lists of neighboring blocks may not necessarily be able to be generated in parallel, and may therefore introduce a bottleneck in the video coding process. As such, HEVC introduced the concept of merge estimation region (MER) to reduce the local interdependency between small blocks to enable parallel merge candidate derivation for those blocks.

A MER may indicate a region in which merge candidate lists can be independently derived for blocks within the MER by checking whether a candidate block is located in the same MER as a current block. If a candidate block is in in the same MER as the current block, the candidate block is not included in the merge candidate list for the current block, so that the motion data for the candidate block does not need to be available at the time of constructing the merge candidate list for the current block. By grouping blocks of a picture into MERs, motion estimation unit222may be able to independently determine merge candidate lists for blocks within the same MER, thereby allowing motion estimation unit222to determine merge candidate lists for blocks within the same MER in parallel or in a pipelined fashion.

Aspects of the present disclosure describes techniques to determine the sizes and shapes of processing areas, such as MERs, in a picture of video data in a way that increases the amount of parallel processing of partition blocks that may be performed by components of video encoder200, such as motion estimation unit222. In some examples, the techniques include motion estimation unit222merging several adjacent partition blocks into a processing area (e.g., a MER) if the processing area does not exactly match the boundary of a single partition block, and applying corresponding rules to each partition block within the processing area, thereby enabling motion estimation unit222to independently process each the partition blocks within the processing area, such as independently determine motion data (e.g., a merge candidate list) for each of the partition blocks without dependencies between partition blocks within the same processing area.

By enabling motion estimation unit222to independently process partition blocks within a processing area, estimation unit222may be able to process the partition blocks within the processing area in parallel or in a pipelined fashion. For example, motion estimation unit222may be able to independently determine motion vectors for partition blocks within the same processing area, so that motion estimation unit222may be able to determine motion vectors for partition blocks within the same processing area in parallel.

In accordance with aspects of the present disclosure, mode selection unit202of video encoder200may determine a partitioning of a current picture of the video data into a plurality of partition blocks. For example, as discussed above, mode selection unit202may partition CTUs into CUs for a current picture of the video data in a number of ways, such as according to one or more of: a ternary tree, a quad tree, or a binary tree.

Motion estimation unit222may determine the number of processing areas for a unit in the current picture of video data as well as the sizes and shapes of such processing areas in a way that is able to handle the flexible ways of partitioning CUTs and CUs while optimizing the encoding performance as well as the encoding efficiency of video encoder200. As such, motion estimation unit222may determine a plurality of processing areas in a unit in the current picture having sizes, wherein that an average size of all of the plurality of processing areas in the unit is greater than or equal to a parameter N. Such processing areas may, for example, be MERs.

A unit in the current picture may be the current picture itself, a slice, a tile, a coding tree unit (CTU), or a partition block of size 2*N. In one example, the parameter N may be defined as the number of samples included in a processing area, and exemplary values for the parameter N may be, for example, 32, 64, 128, 256, and the like.

Motion estimation unit222or other components of video encoder200may determine the value of parameter N based on a video codec of the video data or via any other suitable techniques. For example, motion estimation unit222may determine the value of parameter N based on the number of partition blocks in the unit, the sizes of partition blocks in the unit, and the like as well as factors such as encoder performance, coding efficiency, and the like. In one example, if a unit is a CTU, then the CTU's size may be 2*N, so that the value of parameter N may be half the size of the CTU. In some examples, motion estimation unit222may determine different values for parameter N for different video data, different pictures of the same video data, different video codecs, and the like.

As long as the average area size of processing areas within a unit of the video data is greater than or equal to the parameter N, individual processing areas that follow such a constraint within the unit may have different sizes and different shapes from each other. For example, in cases when size of a processing area does not fit the partitioning of blocks, a processing area can be defined larger than the desired area size defined by the parameter N, and the next processing area can be defined as being smaller than the desired area size. By applying such a constraint to processing areas in a unit, the average size of processing areas in a unit is not increased, and motion estimation unit222is able to maintain its parallel processing capability to process blocks that are within the same processing area.

In some examples, processing areas within the unit may include square-shaped processing areas, non-square shaped processing areas, or a combination of square processing areas and non-square (i.e., rectangular) processing areas. Further, processing areas within the unit may have a mix of sizes that are greater than, less than, or equal to the parameter N. By constraining the processing areas within a unit in such a fashion, motion estimation unit222may ensure that its capabilities to independently process partition blocks within individual processing areas, such as processing partition blocks in the same processing area in parallel, do not decrease due to such non-standard sized processing areas.

As part of determining the plurality of processing areas in the unit, motion estimation unit222may, based define a processing area of the plurality of processing areas that has a size that fits two or more adjacent partition blocks of the plurality of partition blocks. As discussed above, motion estimation unit222may determine, based at least in part on factors such as the partition blocks in the unit, the number of processing areas in the unit as well as the sizes and shapes of the processing areas in the unit. Motion estimation unit222may therefore determine whether the processing areas in the unit fit the partition boundaries of the partition blocks and to merge two or more adjacent partition blocks into a processing area so that the processing area fits the boundaries of the merged two or more adjacent partition blocks. For example, the processing area may be square or non-square and may be the same size and shape as the total size of the two or more adjacent partition blocks that are merged into the processing area, so that the two or more adjacent partition blocks of the plurality of partition blocks fits the size of the processing area.

Motion estimation unit222may independently encode coding units (CUs) within the processing area having the merged two or more adjacent partition blocks. Independently encoding CUs within the processing area may include motion estimation unit222being able to encode individual CUs within the processing area without depending on the result of decoding other CUs in the same processing area, such that motion estimation unit222is able to encode adjacent individual CUs at the same time. This is opposed to examples where, without use of a MER, the coding of motion parameters for a CU cannot occur at the same time as that of a neighboring CU because coding the motion parameters for the CU depends on the result of coding motion parameters for the neighboring CU. For example, because blocks within the same processing area are not merge candidates for other blocks in the same processing area, motion estimation unit222is able to determine the motion parameters for a CU in the processing area, such as a merge candidate list for the CU, as part of encoding the motion parameters for the CU without having to wait for the motion data for an adjacent CU to be determined.

In this way, motion estimation unit222may be able to encode CUs within the same processing area in parallel. For example, motion estimation unit222may be able to determine motion parameters for each of the CUs within the same processing area in parallel. In some examples, motion estimation unit222may use a shared merge candidate list for all CUs within the same processing area to determine motion parameters for the CUs in parallel. By using a shared merge candidate list for all CUs within the same processing area, each CU in the same processing area may use the same merge candidate list for determining motion parameters instead of determining different merge candidate lists used by different CUs in the same processing area. Thus, using a shared merge candidate list for all CUs within the same processing area may reduce the processing that may be required to determine motion parameters for CUs in the same processing area, thereby improving coding efficiency of video encoder200. Similarly, in other examples, motion estimation unit222may perform advanced motion vector prediction (AMVP) or affine motion prediction for CUs within the same processing area in parallel to determine motion parameters for the CUs within the same processing area in parallel.

In some examples, a portion of a processing area may be outside the picture boundary of a picture of video data. Thus, to determine whether a block is a merge candidate, motion estimation unit222may determine whether the block is located outside the picture boundary of the picture and, if so, determine that the block is not available as a merge candidate.

For example, motion estimation unit222may determine a temporal motion vector prediction (TMVP) candidate based on a block of a reference picture that is collocated with a block at the right-bottom corner of a processing area. However, because a portion of a processing area can be located outside of a picture boundary, it may be the case that the block at the right-bottom corner of a processing area is not available for TMVP determination if it is located outside of the picture boundary. In this case, if motion estimation unit222determines that the right-bottom corner of the processing area is located outside the picture boundary, motion estimation unit222may determine that the block is not available for TMVP determination.

Instead, motion estimation unit222may determine if a block of a reference picture that is collocated with the center of the processing area is available to be used to derive the TMVP candidate. Motion estimation unit222may determine whether the center of the processing area is located within the picture boundary and, if so, may use the block of the reference picture that is collocated with the center of the processing area to derive the TMVP candidate. However, because it is also possible that the center of the processing area is located outside of the picture boundary, if motion estimation unit222determines that the center of the processing area is located outside of the picture boundary, then motion estimation unit222may determine that the center of the processing area is also not available for use to derive the TMVP candidate.

Video encoder200stores reconstructed blocks in DPB218. For instance, in examples where operations of filter unit216are not needed, reconstruction unit214may store reconstructed blocks to DPB218. In examples where operations of filter unit216are needed, filter unit216may store the filtered reconstructed blocks to DPB218. Motion estimation unit222and motion compensation unit224may retrieve a reference picture from DPB218, formed from the reconstructed (and potentially filtered) blocks, to inter-predict blocks of subsequently encoded pictures. In addition, intra-prediction unit226may use reconstructed blocks in DPB218of a current picture to intra-predict other blocks in the current picture.

Video encoder200represents an example of a device configured to encode video data including a memory configured to store video data, and one or more processing units implemented in circuitry and configured to determine a partitioning of a current picture of the video data into a plurality of partition blocks, determine a plurality of processing areas for a unit in the current picture having sizes that meet a constraint that an average size of all of the plurality of processing areas in the unit is greater than or equal to a parameter N, based on a processing area of the plurality of processing areas having a size not fitting one or more boundaries of the partition blocks, merge two or more adjacent partition blocks of the plurality of partition blocks into the processing area, and independently encode coding units (CUs) within the processing area having the merged two or more adjacent partition blocks.

In the example ofFIG. 4, video decoder300includes coded picture buffer (CPB) memory320, entropy decoding unit302, prediction processing unit304, inverse quantization unit306, inverse transform processing unit308, reconstruction unit310, filter unit312, and decoded picture buffer (DPB)314. Any or all of CPB memory320, entropy decoding unit302, prediction processing unit304, inverse quantization unit306, inverse transform processing unit308, reconstruction unit310, filter unit312, and DPB314may be implemented in one or more processors or in processing circuitry. For instance, the units of video decoder300may be implemented as one or more circuits or logic elements as part of hardware circuitry, or as part of a processor, ASIC, of FPGA. Moreover, video decoder300may include additional or alternative processors or processing circuitry to perform these and other functions.

Video decoder300may store the reconstructed blocks in DPB314. For instance, in examples where operations of filter unit312are not performed, reconstruction unit310may store reconstructed blocks to DPB314. In examples where operations of filter unit312are performed, filter unit312may store the filtered reconstructed blocks to DPB314. As discussed above, DPB314may provide reference information, such as samples of a current picture for intra-prediction and previously decoded pictures for subsequent motion compensation, to prediction processing unit304. Moreover, video decoder300may output decoded pictures (e.g., decoded video) from DPB314for subsequent presentation on a display device, such as display device118ofFIG. 1.

In this manner, video decoder300represents an example of a video decoding device including a memory configured to store video data, and one or more processing units implemented in circuitry and configured to decode a bitstream into video data.

FIGS. 5A-5Bare conceptual diagrams illustrating determining processing areas for partition blocks generated from quad-tree splitting. As shown inFIGS. 5A and 5B, partition322, such as a CTU, may be a unit in a picture, and is split according to a quad-tree splitting into partition blocks324A-324D. When the size of partition322is 2*N, the four partition blocks324A-324D may each have a size of N/2. Accordingly, a video coder such as video encoder200or video decoder300may determine the size of processing areas for partition blocks324A-324D to be N.

In the example ofFIG. 5A, the video coder may determine the processing areas326A and326B for partition blocks324A-324D to be rectangular areas that each includes two horizontally adjacent sub-partitions of partition322. For example, processing area326A may include horizontally adjacent partition blocks324A and324B, and processing area326B may include horizontally adjacent partition blocks324C and324D. Because processing area326A and processing area326B each has a size N, the average size of all of the plurality of processing areas in the unit that corresponds to partition322is also N, which meets the constraint of the average size of all of the plurality of processing areas in the unit being greater than or equal to N.

In the example ofFIG. 5B, the video coder may determine the processing areas326C and326D for partition blocks324A-324D to be rectangular areas that each includes two vertically adjacent sub-partitions of partition322. For example, processing area326C may include horizontally adjacent partition blocks324A and324C, and processing area326D may include horizontally adjacent partition blocks324B and324D. Because processing area326C and processing area326D each has a size N, the average size of all of the plurality of processing areas in the unit that corresponds to partition322is also N, which meets the constraint of the average size of all of the plurality of processing areas in the unit being greater than or equal to N.

FIGS. 6A-6Bare conceptual diagrams illustrating determining processing areas for partition blocks generated from horizontal ternary-tree splitting. As shown inFIGS. 6A and 6B, partition328, such as a CTU, may be a unit in a picture, and is split according to a horizontal ternary-tree splitting into partition blocks330A-330C. The size of partition328may be 2*N. The size of partition block330A may be N/2, the size of partition block330B may be N, and the size of partition block330C may be N/2.

In the example ofFIG. 6A, the video coder may determine the processing areas332A and332B for partition blocks330A-330C to be rectangular areas that are different in size from each other. Processing area332A may be of size 1/2N and include partition block330A, while processing area332B may be of size 3N/2 and include partition blocks330B and330C. Because two processing areas332A and332B together fit the boundaries of partition328of size 2*N, the average size of the two processing areas332A and332B in the unit that corresponds to partition328is N, which meets the constraint of the average size of all processing areas in the unit being greater than or equal to N.

In the example ofFIG. 6B, the video coder may determine the processing areas332C and332D for partition blocks330A-330C to be rectangular areas that are different in size from each other. Processing area332C may be of size 3/2N and include partition blocks330A and330B, while processing area332D may be of size N/2 and include partition block330C. Because two processing areas332C and332D together fit the boundaries of partition328of size 2*N, the average size of the two processing areas332C and332D in the unit that corresponds to partition328is N, which meets the constraint of the average size of all processing areas in the unit being greater than or equal to N.

FIGS. 7A-7Bare conceptual diagrams illustrating determining processing areas for partition blocks generated from vertical ternary-tree splitting. As shown inFIGS. 7A and 7B, partition334, such as a CTU, may be a unit in a picture, and is split according to a vertical ternary-tree splitting into partition blocks336A-336C. The size of partition334may be 2*N. The size of partition block336A may be N/2, the size of partition block336B may be N, and the size of partition block336C may be N/2.

In the example ofFIG. 7A, the video coder may determine the processing areas338A and338B for partition blocks336A-336C to be rectangular areas that are different in size from each other. Processing area338A may be of size 1/2N and include partition block336A, while processing area338B may be of size 3N/2 and include partition blocks336B and336C. Because two processing areas338A and338B together fit the boundaries of partition334of size 2*N, the average size of the two processing areas338A and338B in the unit that corresponds to partition334is N, which meets the constraint of the average size of all processing areas in the unit being greater than or equal to N.

In the example ofFIG. 7B, the video coder may determine the processing areas338C and338D for partition blocks336A-336C to be rectangular areas that are different in size from each other. Processing area338C may be of size 3/2N and include partition blocks336A and336B, while processing area338D may be of size N/2 and include partition block336C. Because two processing areas338C and338D together fit the boundaries of partition334of size 2*N, the average size of the two processing areas338C and338D in the unit that corresponds to partition334is N, which meets the constraint of the average size of all processing areas in the unit being greater than or equal to N.

FIG. 8is a flowchart illustrating an example method for encoding a current block. The current block may comprise a current CU. Although described with respect to video encoder200(FIGS. 1 and 3), it should be understood that other devices may be configured to perform a method similar to that ofFIG. 8.

In this example, video encoder200initially predicts the current block (350). For example, video encoder200may form a prediction block for the current block. As part of forming the prediction block for the current block, video encoder200may determine motion parameters for the current block. To enable the motion parameters for the current block to be determined in parallel with other adjacent blocks, video encoder200may determine a plurality of processing areas in a unit in the current picture of video data having sizes, where the average size of all of the processing areas in the unit is greater than a parameter N, including defining a processing area that has a size that fits the current block and one or more adjacent blocks, thereby merging the current block and the one or more adjacent blocks into a processing area, such as a MER. Video encoder200may thereby determine motion parameters for each of the blocks merged into the processing area, including the current block, in parallel.

Video encoder200may then calculate a residual block for the current block (352). To calculate the residual block, video encoder200may calculate a difference between the original, unencoded block and the prediction block for the current block. Video encoder200may then transform and quantize transform coefficients of the residual block (354). Next, video encoder200may scan the quantized transform coefficients of the residual block (356). During the scan, or following the scan, video encoder200may entropy encode the transform coefficients (358). For example, video encoder200may encode the transform coefficients using CAVLC or CABAC. Video encoder200may then output the entropy encoded data of the block (360).

FIG. 9is a flowchart illustrating an example method for decoding a current block of video data. The current block may comprise a current CU. Although described with respect to video decoder300(FIGS. 1 and 4), it should be understood that other devices may be configured to perform a method similar to that ofFIG. 9.

Video decoder300may receive entropy encoded data for the current block, such as entropy encoded prediction information and entropy encoded data for transform coefficients of a residual block corresponding to the current block (370). Video decoder300may entropy decode the entropy encoded data to determine prediction information for the current block and to reproduce transform coefficients of the residual block (372). Video decoder300may predict the current block (374), e.g., using an intra- or inter-prediction mode as indicated by the prediction information for the current block, to calculate a prediction block for the current block. As part of using inter-prediction mode for the current block to calculate a prediction block for the current block, video decoder300may determine motion parameters for the current block. To enable the motion parameters for the current block to be determined in parallel with other adjacent blocks, video decoder300may determine a plurality of processing areas in a unit in the current picture of video data having sizes, where the average size of all of the processing areas in the unit is greater than a parameter N, including defining a processing area that has a size that fits the current block and one or more adjacent blocks, thereby merging the current block and the one or more adjacent blocks into a processing area, such as a MER. For example, the plurality of processing areas may be in the encoded entropy data. Video decoder300may thereby determine motion parameters for each of the blocks merged into the processing area, including the current block, in parallel.

Video decoder300may then inverse scan the reproduced transform coefficients (376), to create a block of quantized transform coefficients. Video decoder300may then inverse quantize and inverse transform the transform coefficients to produce a residual block (378). Video decoder300may ultimately decode the current block by combining the prediction block and the residual block (380).

FIG. 10is a flowchart illustrating an example method for deriving a processing area for parallel processing in video coding. As shown inFIG. 10, a video coder such as video encoder200or video decoder300, may determine a partitioning of a current picture of the video data into a plurality of partition blocks (500). For example, the video coder may partition a CTU into CUs and may, in some examples, determine the partitioning of the current picture according to one or more of: a ternary tree, a quad tree, or a binary tree.

The video coder may determine a plurality of processing areas in a unit in the current picture having sizes, where an average size of all of the plurality of processing areas in the unit is greater than or equal to a parameter N, and where determining the plurality of processing areas in the unit includes defining a processing area of the plurality of processing areas that has a size that fits two or more adjacent partition blocks of the plurality of partition blocks (502). For example, the video coder may determine, based on the number, size, and/or shape of partition blocks, the number, size, and/or shape of processing areas that covers the processing area, such as to reduce the sacrifice of rate-distortion performance as much as possible.

In some examples, the parameter N specifies the number of samples included in one processing area and, in some examples, the unit is one of: the current picture, a slice, a tile, a CTU, or a partition block of size 2*N.

Further, in some examples, the processing area is a first processing area of the plurality of processing areas, and a size of the first processing area of the plurality of processing areas is different from a size of a second processing area of the plurality of processing areas. For example, the size of the first processing area of the plurality of processing areas may be larger than the parameter N, and the size of the second processing area of the plurality of processing areas is smaller than the parameter N, such as shown in the examples ofFIGS. 6A, 6B, 7A, and 7B.

The video coder may independently code CUs within the processing area having the merged two or more adjacent partition blocks (504). As discussed above, the video coder may be video encoder200or video decoder300. As such, in some examples, video encoder200may independently encode CUs within the processing area having the merged two or more adjacent partition blocks, and in other examples video decoder300may independently decode CUs within the processing area having the merged two or more adjacent partition blocks.

In some examples, the processing area is a merge estimation region, and the video coder independently coding the CUs within the processing area includes the video coder determining motion parameters for each of the CUs within the processing area in parallel. As discussed above, coding the CUs in parallel does not mean that CUs in the processing areas are coded at exactly the same time such that the video coder starts and ends coding of the CUs at the exact same time. Instead, coding the CUs in parallel includes video coders being able to perform the coding of the CUs at the same time.

In some examples, the processing area is a merge estimation region, and the video coder independently coding the CUs within the processing area includes the video coder using a shared merge candidate list for all CUs within the processing area to determine motion parameters for the CUs in parallel. By using a shared merged candidate list for all CUs within the same processing area, the video coder does not have to determine different merge candidate lists for different CUs in the same processing area, thereby improving the performance of the video coder in coding the CUs.

In some examples, the video coder independently coding the CUs within the processing area includes the video coder performing, in parallel, at least one of: advanced motion vector prediction (AMVP) for the CUs within the processing area, which sets certain constrains on the motion vector prediction candidates for the CUs based on the characteristics and availability of spatial motion prediction candidates, and/or affine motion prediction for the CUs within the processing area, which uses motion vectors of an affine motion model of neighboring block(s) to derive motion vector prediction candidates for a current block, to determine motion parameters for the CUs.

Illustrative examples of the disclosure include:

Example 1: A method of coding video data, the method comprising: determining a partitioning of a current picture of the video data into a plurality of partition blocks; based on a processing area having a standard size not fitting one or more boundaries of the partition blocks, merging two or more adjacent partition blocks of the plurality of partition blocks into the processing area; and coding units (CUs) within the processing area having the merged two or more adjacent partition blocks in parallel.

Example 2: A method according to Example 1, wherein the standard size is defined by a parameter N that specifies the number of samples to be included in the processing area.

Example 3: A method according to Example 2, wherein all processing areas of a unit have an average area greater than or equal to a parameter N.

Example 4: A method according to Example 3, wherein the unit is one of: the current picture, a slice, a tile, a coding tree unit (CTU), or a partition block of size 2*N.

Example 5: A method according to of any of Examples 1-4, wherein partitioning the block comprises partitioning the block according to a ternary tree.

Example 6: A method according to any of Examples 1-4, wherein partitioning the block comprises partitioning the block according to a quad tree.

Example 7: A method according to any of Examples 1-4, wherein partitioning the block comprises partitioning the block according to a binary tree.

Example 8: A method according to Examples 1-4, wherein the processing area is a merge estimation region and coding the CUs within the processing area in parallel comprises using a shared merge candidate list for all of the CUs within the processing area to determine motion parameters in parallel.

Example 9: A method according to any of Examples 1-8, wherein coding the CUs within the processing area in parallel comprises performing advanced motion vector prediction (AMVP) or affine motion prediction all of the CUs within the processing area to determine motion parameters in parallel.

Example 10: A method according to any of Examples 1-9, wherein coding comprises decoding.

Example 11: A method according to any of Examples 1-9, wherein coding comprises encoding.

Example 12: A device for coding video data, the device comprising one or more means for performing the method of any of Examples 1-11.

Example 13: A device according to Example 12, wherein the one or more means comprise one or more processors implemented in circuitry.

Example 14: A device according to any of Examples 12 and 13, further comprising a memory to store the video data.

Example 15: A device according to any of Examples 12-14, further comprising a display configured to display decoded video data.

Example 16: A device according to any of Examples 12-15, wherein the device comprises one or more of a camera, a computer, a mobile device, a broadcast receiver device, or a set-top box.

Example 17: A device according to of any of Examples 12-16, wherein the device comprises a video decoder.

Example 18: A device according to any of Examples 12-17, wherein the device comprises a video encoder.

Example 19: A computer-readable storage medium having stored thereon instructions that, when executed, cause one or more processors to perform the method of any of Examples 1-11.

Example 20: A device for encoding video data, the device comprising means for performing the methods of any of Examples 1-11.