WO2019124226A1

WO2019124226A1 - Systems and methods for applying deblocking filters to reconstructed video data at picture partition boundaries

Info

Publication number: WO2019124226A1
Application number: PCT/JP2018/045958
Authority: WO
Inventors: Michael Horowitz; Kiran Mukesh MISRA; Sachin G. Deshpande; Weijia Zhu; Christopher Andrew Segall
Original assignee: Sharp Kabushiki Kaisha
Priority date: 2017-12-20
Filing date: 2018-12-13
Publication date: 2019-06-27

Abstract

A method of filtering reconstructed video data is disclosed. The method comprises : receiving an array of sample values including adjacent reconstructed video blocks for a component of video data, wherein the array of sample values coincides with a picture partitioning boundary; determining one or more offset values associated with the picture partitioning boundary; selecting a filter based on the determined offset values; and modifying sample values in the adjacent reconstructed video blocks based on the selected filter.

Description

SYSTEMS AND METHODS FOR APPLYING DEBLOCKING FILTERS TO RECONSTRUCTED VIDEO DATA AT PICTURE PARTITION BOUNDARIES

This disclosure relates to video coding and more particularly to techniques for performing deblocking of reconstructed video data.

Digital video capabilities can be incorporated into a wide range of devices, including digital televisions, laptop or desktop computers, tablet computers, digital recording devices, digital media players, video gaming devices, cellular telephones, including so-called smartphones, medical imaging devices, and the like. Digital video may be coded according to a video coding standard. Video coding standards may incorporate video compression techniques. Examples of video coding standards include ISO/IEC MPEG-4 Visual and ITU-T H.264 (also known as ISO/IEC MPEG-4 AVC) and High-Efficiency Video Coding (HEVC). HEVC is described in High Efficiency Video Coding (HEVC), Rec. ITU-T H.265, December 2016, which is incorporated by reference, and referred to herein as ITU-T H.265. Extensions and improvements for ITU-T H.265 are currently being considered for the development of next generation video coding standards. For example, the ITU-T Video Coding Experts Group (VCEG) and ISO/IEC (Moving Picture Experts Group (MPEG) (collectively referred to as the Joint Video Exploration Team (JVET)) are studying the potential need for standardization of future video coding technology with a compression capability that significantly exceeds that of the current HEVC standard. The Joint Exploration Model 7 (JEM 7), Algorithm Description of Joint Exploration Test Model 7 (JEM 7), ISO/IEC JTC1/SC29/WG11 Document: JVET-G1001, July 2017, Torino, IT, which is incorporated by reference herein, describes the coding features that are under coordinated test model study by the JVET as potentially enhancing video coding technology beyond the capabilities of ITU-T H.265. It should be noted that the coding features of JEM 7 are implemented in JEM reference software. As used herein, the term JEM may collectively refer to algorithms included in JEM 7 and implementations of JEM reference software.

Video compression techniques reduce data requirements for storing and transmitting video data by exploiting the inherent redundancies in a video sequence. Video compression techniques may sub-divide a video sequence into successively smaller portions (i.e., groups of frames within a video sequence, a frame within a group of frames, slices within a frame, coding tree units (e.g., macroblocks) within a slice, coding blocks within a coding tree unit, etc.). Intra prediction coding techniques (e.g., intra-picture (spatial)) and inter prediction techniques (i.e., inter-picture (temporal)) may be used to generate difference values between a unit of video data to be coded and a reference unit of video data. The difference values may be referred to as residual data. Residual data may be coded as quantized transform coefficients. Syntax elements may relate residual data and a reference coding unit (e.g., intra-prediction mode indices, motion vectors, and block vectors). Residual data and syntax elements may be entropy coded. Entropy encoded residual data and syntax elements may be included in a compliant bitstream. Compliant bitstreams and associated metadata may be formatted according to data structures.

In general, this disclosure describes various techniques for coding video data. In particular, this disclosure describes techniques for performing deblocking of reconstructed video data. As described in further detail below, a picture may be partitioned into slices and tiles. It should be noted that as used herein the term tile structure may refer to a particular partitioning of a picture into tiles. Tile structures in some examples may include overlapping tiles. According to the techniques described herein, various controls for deblocking reconstructed video data at slice and/or tile boundaries may be implemented in a video coding device. It should be noted that although techniques of this disclosure are described with respect to ITU-T H.264, ITU-T H.265, and JEM, the techniques of this disclosure are generally applicable to video coding. For example, the coding techniques described herein may be incorporated into video coding systems, (including video coding systems based on future video coding standards) including block structures, intra prediction techniques, inter prediction techniques, transform techniques, filtering techniques, and/or entropy coding techniques other than those included in ITU-T H.265. Thus, reference to ITU-T H.264, ITU-T H.265 and JEM is for descriptive purposes and should not be construed to limit the scope of the techniques described herein. Further, it should be noted that incorporation by reference of documents herein should not be construed to limit or create ambiguity with respect to terms used herein. For example, in the case where an incorporated reference provides a different definition of a term than another incorporated reference and/or as the term is used herein, the term should be interpreted in a manner that broadly includes each respective definition and/or in a manner that includes each of the particular definitions in the alternative.

In one example, a method of filtering reconstructed video data comprises receiving an array of sample values including adjacent reconstructed video blocks for a component of video data, wherein the array of sample values coincides with a picture partitioning boundary, determining one or more offset values associated with the picture partitioning boundary, selecting a filter based on the determined offset values and modifying sample values in the adjacent reconstructed video blocks based on the selected filter.

FIG. 1 is a block diagram illustrating an example of a system that may be configured to encode and decode video data according to one or more techniques of this this disclosure. FIG. 2A is conceptual diagrams illustrating blocks of video data including a deblocking boundary in accordance with one or more techniques of this disclosure. FIG. 2B is conceptual diagrams illustrating blocks of video data including a deblocking boundary in accordance with one or more techniques of this disclosure. FIG. 3 is an example of a table that may be used to determine deblocking parameters in accordance with one or more techniques of this disclosure. FIG. 4A is a conceptual diagrams illustrating coded video data and corresponding partitioning structures according to one or more techniques of this this disclosure. FIG. 4B is a conceptual diagrams illustrating coded video data and corresponding partitioning structures according to one or more techniques of this this disclosure. FIG. 5 is a conceptual diagram illustrating a data structure encapsulating coded video data and corresponding metadata according to one or more techniques of this this disclosure. FIG. 6 is a conceptual drawing illustrating an example of components that may be included in an implementation of a system that may be configured to encode and decode video data according to one or more techniques of this this disclosure. FIG. 7 is a block diagram illustrating an example of a video encoder that may be configured to encode video data according to one or more techniques of this disclosure. FIG. 8 is a block diagram illustrating an example of a video decoder that may be configured to decode video data according to one or more techniques of this disclosure.

In one example, a device for video coding comprises one or more processors configured to receive an array of sample values including adjacent reconstructed video blocks for a component of video data, wherein the array of sample values coincides with a picture partitioning boundary, determining one or more offset values associated with the picture partitioning boundary, select a filter based on the determined offset values and modify sample values in the adjacent reconstructed video blocks based on the selected filter.

In one example, a non-transitory computer-readable storage medium comprises instructions stored thereon that, when executed, cause one or more processors of a device to receive an array of sample values including adjacent reconstructed video blocks for a component of video data, wherein the array of sample values coincides with a picture partitioning boundary, determining one or more offset values associated with the picture partitioning boundary, select a filter based on the determined offset values and modify sample values in the adjacent reconstructed video blocks based on the selected filter.

In one example, an apparatus comprises means for receiving an array of sample values including adjacent reconstructed video blocks for a component of video data, wherein the array of sample values coincides with a picture partitioning boundary, means for determining one or more offset values associated with the picture partitioning boundary, means for selecting a filter based on the determined offset values and means for modifying sample values in the adjacent reconstructed video blocks based on the selected filter.

The details of one or more examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims.

Video content typically includes video sequences comprised of a series of frames. A series of frames may also be referred to as a group of pictures (GOP). Each video frame or picture may include a plurality of slices or tiles, where a slice or tile includes a plurality of video blocks. As used herein, the term video block may generally refer to an area of a picture or may more specifically refer to the largest array of sample values that may be predictively coded, sub-divisions thereof, and/or corresponding structures. Further, the term current video block may refer to an area of a picture being encoded or decoded. A video block may be defined as an array of sample values that may be predictively coded. It should be noted that in some cases pixel values may be described as including sample values of respective components of video data, which may also be referred to as color components, (e.g., luma (Y) and chroma (Cb and Cr) components or red, green, and blue components). It should be noted that in some cases, the terms pixel values and sample values are used interchangeably. Video blocks may be ordered within a picture according to a scan pattern (e.g., a raster scan). A video encoder may perform predictive encoding on video blocks and sub-divisions thereof. Video blocks and sub-divisions thereof may be referred to as nodes.

ITU-T H.264 specifies a macroblock structure including 16x16 luma samples. That is, in ITU-T H.264, a picture is segmented into macroblocks. ITU-T H.265 specifies an analogous Coding Tree Unit (CTU) structure, which may also be referred to as a largest coding unit (LCU). In ITU-T H.265, pictures are segmented into CTUs. In ITU-T H.265, for a picture, a CTU size may be set as including 16x16, 32x32, or 64x64 luma samples. In ITU-T H.265, a CTU is composed of respective Coding Tree Blocks (CTB) for each component of video data (e.g., luma (Y) and chroma (Cb and Cr)). Further, in ITU-T H.265, a CTU may be partitioned according to a quadtree (QT) partitioning structure, which results in the CTBs of the CTU being partitioned into Coding Blocks (CB). That is, in ITU-T H.265, a CTU may be partitioned into quadtree leaf nodes. According to ITU-T H.265, one luma CB together with two corresponding chroma CBs and associated syntax elements are referred to as a coding unit (CU). In ITU-T H.265, a minimum allowed size of a CB may be signaled. In ITU-T H.265, the smallest minimum allowed size of a luma CB is 8x8 luma samples. In ITU-T H.265, the decision to code a picture area using intra prediction or inter prediction is made at the CU level. As illustrated in FIG. 4A, a picture included in a GOP may include slices, where each slice includes a sequence of CTUs and each CTU may be partitioned according to a QT or QTBT structure.

In ITU-T H.265, a CU is associated with a prediction unit (PU) structure having its root at the CU. In ITU-T H.265, PU structures allow luma and chroma CBs to be split for purposes of generating corresponding reference samples. That is, in ITU-T H.265, luma and chroma CBs may be split into respect luma and chroma prediction blocks (PBs), where a PB includes a block of sample values for which the same prediction is applied. In ITU-T H.265, a CB may be partitioned into 1, 2, or 4 PBs. ITU-T H.265 supports PB sizes from 64x64 samples down to 4x4 samples. In ITU-T H.265, square PBs are supported for intra prediction, where a CB may form the PB or the CB may be split into four square PBs (i.e., intra prediction PB size types include MxM or M/2xM/2, where M is the height and width of the square CB). In ITU-T H.265, in addition to the square PBs, rectangular PBs are supported for inter prediction, where a CB may by halved vertically or horizontally to form PBs (i.e., inter prediction PB types include MxM, M/2xM/2, M/2xM, or MxM/2). Further, it should be noted that in ITU-T H.265, for inter prediction, four asymmetric PB partitions are supported, where the CB is partitioned into two PBs at one quarter of the height (at the top or the bottom) or width (at the left or the right) of the CB (i.e., asymmetric partitions include M/4xM left, M/4xM right, MxM/4 top, and MxM/4 bottom). Intra prediction data (e.g., intra prediction mode syntax elements) or inter prediction data (e.g., motion data syntax elements) corresponding to a PB is used to produce reference and/or predicted sample values for the PB.

JEM specifies a CTU having a maximum size of 256x256 luma samples. JEM specifies a quadtree plus binary tree (QTBT) block structure. In JEM, the QTBT structure enables quadtree leaf nodes to be further partitioned by a binary tree (BT) structure. That is, in JEM, the binary tree structure enables quadtree leaf nodes to be recursively divided vertically or horizontally. Thus, the binary tree structure in JEM enables square and rectangular leaf nodes, where each leaf node includes a CB. In JEM, CBs are used for prediction without any further partitioning. That is, in JEM, a CB may be a block of sample values on which the same prediction is applied. Thus, a JEM QTBT leaf node may be analogous a PB in ITU-T H.265.

Intra prediction data (e.g., intra prediction mode syntax elements) or inter prediction data (e.g., motion data syntax elements) may associate PUs, or the like, with corresponding reference samples. Residual data may include respective arrays of difference values, corresponding to each component of video data for a current video block and reference samples. Residual data may be in the pixel domain. A transform, such as, a discrete cosine transform (DCT), a discrete sine transform (DST), an integer transform, a wavelet transform, or a conceptually similar transform, may be applied to pixel difference values to generate transform coefficients. It should be noted that in ITU-T H.265, CUs may be further sub-divided into Transform Units (TUs). That is, an array of pixel difference values may be sub-divided for purposes of generating transform coefficients (e.g., four 8x8 transforms may be applied to a 16x16 array of residual values corresponding to a 16x16 luma CB), such sub-divisions may be referred to as Transform Blocks (TBs). It should be noted that in ITU-T H.265, TBs are not necessarily aligned with PBs. Further, it should be noted that in JEM, residual values corresponding to a CB are used to generate transform coefficients without further partitioning. That is, in JEM a QTBT leaf node may be analogous to both a PB and a TB in ITU-T H.265. It should be noted that in JEM, a core transform and a subsequent secondary transforms may be applied (in the video encoder) to generate transform coefficients. For a video decoder, the order of transforms is reversed. Further, in JEM, whether a secondary transform is applied to generate transform coefficients may be dependent on a prediction mode.

Transform coefficients may be quantized according to a quantization parameter (QP). Quantized transform coefficients (which may be referred to as level values) may be entropy coded according to an entropy encoding technique (e.g., content adaptive variable length coding (CAVLC), context adaptive binary arithmetic coding (CABAC), probability interval partitioning entropy coding (PIPE), etc.). Further, syntax elements, such as, a syntax element indicating a prediction mode, may also be entropy coded. Entropy encoded quantized transform coefficients and corresponding entropy encoded syntax elements may form a compliant bitstream that can be used to reproduce video data. A binarization process may be performed on syntax elements as part of an entropy coding process. Binarization refers to the process of converting a syntax value into a series of one or more bits. These bits may be referred to as “bins.”

With respect to the equations used herein, the following arithmetic operators may be used:

Further, the following mathematical functions may be used:

With respect to the example syntax used herein, the following definitions of logical operators may be applied:

Further, the following relational operators may be applied:

Further, it should be noted that in the syntax descriptors used herein, the following descriptors may be applied:

As described above, intra prediction data or inter prediction data may associate an area of a picture (e.g., a PB or a CB) with corresponding reference samples. For intra prediction coding, an intra prediction mode may specify the location of reference samples within a picture. In ITU-T H.265, defined possible intra prediction modes include a planar (i.e., surface fitting) prediction mode (predMode: 0), a DC (i.e., flat overall averaging) prediction mode (predMode: 1), and 33 angular prediction modes (predMode: 2-34). In JEM, defined possible intra-prediction modes include a planar prediction mode (predMode: 0), a DC prediction mode (predMode: 1), and 65 angular prediction modes (predMode: 2-66). It should be noted that planar and DC prediction modes may be referred to as non-directional prediction modes and that angular prediction modes may be referred to as directional prediction modes. It should be noted that the techniques described herein may be generally applicable regardless of the number of defined possible prediction modes.

For inter prediction coding, a motion vector (MV) identifies reference samples in a picture other than the picture of a video block to be coded and thereby exploits temporal redundancy in video. For example, a current video block may be predicted from reference block(s) located in previously coded frame(s) and a motion vector may be used to indicate the location of the reference block. A motion vector and associated data may describe, for example, a horizontal component of the motion vector, a vertical component of the motion vector, a resolution for the motion vector (e.g., one-quarter pixel precision, one-half pixel precision, one-pixel precision, two-pixel precision, four-pixel precision), a prediction direction and/or a reference picture index value. Further, a coding standard, such as, for example ITU-T H.265, may support motion vector prediction. Motion vector prediction enables a motion vector to be specified using motion vectors of neighboring blocks. Examples of motion vector prediction include advanced motion vector prediction (AMVP), temporal motion vector prediction (TMVP), so-called “merge” mode, and “skip” and “direct” motion inference. Further, JEM supports advanced temporal motion vector prediction (ATMVP), Spatial-temporal motion vector prediction (STMVP), Pattern matched motion vector derivation (PMMVD) mode, which is a special merge mode based on Frame-Rate Up Conversion (FRUC) techniques, and affine transform motion compensation prediction techniques.

As described above, a quantization process may be performed on transform coefficients. Quantization approximates transform coefficients by amplitudes restricted to a set of specified values. Quantization may be used in order to vary the amount of data required to represent a group of transform coefficients. Quantization may be generally described as being realized through division of transform coefficients by a scaling factor and any associated rounding functions (e.g., rounding to the nearest integer). Thus, inverse quantization (or “dequantization”) may include multiplication of coefficient level values by the scaling factor. It should be noted that as used herein the term quantization process in some instances may generally refer to division by a scaling factor to generate level values or multiplication by a scaling factor to recover transform coefficients in some instances. That is, a quantization process may refer to quantization in some cases and inverse quantization in some cases. A current block of video data is reconstructed by performing inverse quantization on level values, performing an inverse transform, and adding a set of prediction values to the resulting residual. The sample values of the reconstructed block may differ from the sample values of the current video block that were input into an encoding process. In this manner, coding may be said to be lossy. However, it should be noted that the difference in sample values may be considered acceptable to a viewer of the reconstructed video. Further, it should be noted that in some cases, coding video data on a block-by-block basis may result in artifacts (e.g., so-called blocking artifacts, banding artifacts, etc.)
As described above, quantization may be realized through division of transform coefficients by a scaling factor and further may be used in order to vary the amount of data required to represent a group of transform coefficients. That is, increasing the scaling factor (or degree of quantization) reduces the amount of data required to represent a group coefficients. In ITU-T H.265, the degree of quantization may be determined by a quantization parameter, QP. In ITU-T H.265, for a bit-depth of 8-bits, the QP can take 52 values from 0 to 51 and a change of 1 for QP generally corresponds to a change in the value of the quantization scaling factor by approximately 12%. It should be noted that more generally, in ITU-T H.265, the valid range of QP values for a source bit-depth is: -6*(bitdepth-8) to +51 (inclusive). Thus, for example, in the case where the bit-depth is 10-bits, QP can take 64 values from -12 to 51, which may be mapped to values 0 to 63 during dequantization. In ITU-T H.265, a quantization parameter may be updated for each CU and a respective quantization parameter may be derived for each of luma and chroma components. It should be noted that as the degree of quantization increases (e.g., transform coefficients are divided by a larger scaling factor value), the amount of distortion may be increased (e.g., reconstructed video data may appear more “blocky” to a user).

In some cases, blocking artifacts may cause coding block boundaries of reconstructed video data to be visually perceptible to a user. In order to reduce blocking artifacts, reconstructed sample values may be modified to minimize artifacts introduced by the video coding process. Such modifications may generally be referred to as filtering. It should be noted that filtering may occur as part of an in-loop filtering process or a post-loop filtering process. For an in-loop filtering process, the resulting sample values of a filtering process may be used for predictive video blocks (e.g., stored to a reference frame buffer for subsequent encoding at a video encoder and subsequent decoding at a video decoder). For a post-loop filtering process the resulting sample values of a filtering process are merely output as part of the decoding process (e.g., not used for subsequent coding). For example, for an in-loop filtering process, the sample values resulting from filtering a reconstructed block would be used for subsequent decoding (e.g., stored to a reference buffer) and would be output (e.g., to a display). For a post-loop filtering process, the reconstructed block without modification would be used for subsequent decoding and the sample values resulting from filtering the reconstructed block would be output.

Deblocking (or de-blocking), deblock filtering, performing deblocking, or applying a deblocking filter refers to the process of smoothing video block boundaries with neighboring reconstructed video blocks (i.e., making boundaries less perceptible to a viewer). Smoothing the boundaries of neighboring reconstructed video blocks may include modifying sample values included in rows or columns adjacent to a boundary. ITU-T H.265 provides where a deblocking filter is applied to reconstructed sample values as part of an in-loop filtering process. ITU-T H.265 includes two types deblocking filters that may be used for modifying luma samples: a Strong Filter which modifies sample values in the three adjacent rows or columns to a boundary and a Weak Filter which modifies sample values in the immediately adjacent row or column to a boundary and conditionally modifies sample values in the second row or column from the boundary. Further, ITU-T H.265 includes one type of filter that may be used for modifying chroma samples, i.e., a Normal Filter.

FIGS. 2A-2B illustrate sample values included in video blocks P and Q having a boundary. As used herein, video blocks P and Q are used to refer to adjacent video blocks having a block boundary at which deblocking may be applied. The manner in which sample values are modified may be based on defined filters, where p_i and q_i represent respective sample values in a column for a vertical boundary and sample values in a row for a horizontal boundary and p_i’ and q_i’ represent modified sample values. ITU-T H.265 includes two types of filters that may be used for modifying luma samples: a Strong Filter which modifies sample values in the three adjacent rows or columns to a boundary and a Weak Filter which modifies sample values in the immediately adjacent row or column to a boundary and conditionally modifies sample values in the second row or column from the boundary. Simplified definitions of the Strong Filter and Weak Filter equations for modifying luma sample values are provided below. The definitions are simplified in that they do not include clipping operations provided in ITU-T H.265 (i.e., in ITU-T H.265, filtered values are clipped based on a value t_C, described below), however, reference is made to Section 8.7.2.5.7 of ITU-T H.265, which provides the complete definitions.

Further, ITU-T H.265 includes one type of filter that may be used for modifying chroma samples: Normal Filter. Simplified definitions for the Normal Filter equations for modifying chroma sample values are provided below.

Deblocking may be performed based on a deblocking granularity. ITU-T H.265 provides an 8x8 deblocking granularity. That is, in ITU-T H.265 for an area of a picture, each edge lying on the 8x8 grid is evaluated to determine if a boundary exists. Further, in ITU-T H.265, a boundary strength (Bs) is determined for each boundary. In ITU-T H.265, Bs is determined as follows:

In ITU-T H.265, based on the QP used for coding the CBs including video blocks P and Q (which may be referred to as QP_P and QP_Q), variables t_C’ and β’ are determined. FIG. 3 provides a table for determining t_C’ and β’. In ITU-T H.265, the index Q is determined as follows:

ITU-T H.265, variables β and t_C are derived as follows:

ITU-T H.265, defines a variable d, where d is determined based on luma sample values as follows:

Further, in ITU-T H.265 a variable dpq is set to a value based on the values of d and β. Finally, in ITU-T H.265, each of Bs, t_C, β, and d are used to determine which filter type to apply (e.g., Strong Filter or Weak Filter). Further, in ITU-T H.265, for the chroma component, the Normal Filter is applied only when Bs equals 2. That is, in ITU-T H.265, deblocking only occurs for the chroma component if one the blocks P or Q is generated using an intra prediction mode.

As described above, according to ITU-T H.265, each video frame or picture may be partitioned to include one or more slices and further partitioned to include one or more tiles. FIGS. 4A-4B are conceptual diagrams illustrating an example of a group of pictures including slices and further partitioning pictures into tiles. In the example illustrated in FIG. 4A, Pic₄is illustrated as including two slices (i.e., Slice₁ and Slice₂) where each slice includes a sequence of CTUs (e.g., in raster scan order). In the example illustrated in FIG. 4B, Pic₄is illustrated as including six tiles (i.e., Tile₁ to Tile₆), where each tile is rectangular and includes a sequence of CTUs. It should be noted that in ITU-T H.265, a tile may consist of coding tree units contained in more than one slice and a slice may consist of coding tree units contained in more than one tile. However, ITU-T H.265 provides that one or both of the following conditions shall be fulfilled: (1) All coding tree units in a slice belong to the same tile; and (2) All coding tree units in a tile belong to the same slice. Thus, for example, with respect to FIG. 4B, all of the tiles may belong to a single slice or the tiles may belong to multiple slices (e.g., Tile₁ to Tile₃may belong to Slice₁ and Tile₄ to Tile₆may belong to Slice₂).

Further, as illustrated in FIG. 4B, tiles may form tile sets (i.e., Tile₂ and Tile₃ form a tile set). Tiles and tile sets may be used to define boundaries for coding dependencies (e.g., intra-prediction dependencies, entropy encoding dependencies, etc.,) and as such, may enable parallelism in coding and region-of-interest coding. For example, if the video sequence in the example illustrated in FIG. 4B corresponds to a nightly news program, the tile set formed by Tile₂ and Tile₃ may correspond to a visual region-of-interest including a news anchor reading the news. ITU-T H.265 defines signaling that enables motion-constrained tile sets (MCTS). A motion-constrained tile set may include a tile set for which inter-picture prediction dependencies are limited to the collocated tile sets in reference pictures. Thus, it is possible to perform motion compensation for a given MCTS independent of the decoding of other tile sets outside the MCTS. For example, referring to FIG. 4B, if the tile set formed by Tile₂ and Tile₃ is a MCTS and each of Pic₁to Pic₃include collocated tile sets, motion compensation may be performed on Tile₂ and Tile₃ independent of coding Tile₁, Tile₄, Tile₅, and Tile₆ in Pic₄ and tiles collocated with tiles Tile₁, Tile₄, Tile₅, and Tile₆ in each of Pic₁to Pic₃. Coding video data according to MCTS may be useful for video applications including omnidirectional video presentations.

In ITU-T H.265, a coded video sequence (CVS) may be encapsulated (or structured) as a sequence of access units, where each access unit includes video data structured as network abstraction layer (NAL) units. In ITU-T H.265, a bitstream is described as including a sequence of NAL units forming one or more CVSs. It should be noted that ITU-T H.265 supports multi-layer extensions, including format range extensions (RExt), scalability (SHVC), multi-view (MV-HEVC), and 3-D (3D-HEVC). Multi-layer extensions enable a video presentation to include a base layer and one or more additional enhancement layers. For example, a base layer may enable a video presentation having a basic level of quality (e.g., High Definition rendering) to be presented and an enhancement layer may enable a video presentation having an enhanced level of quality (e.g., an Ultra High Definition rendering) to be presented. In ITU-T H.265, an enhancement layer may be coded by referencing a base layer. That is, for example, a picture in an enhancement layer may be coded (e.g., using inter prediction techniques) by referencing one or more pictures (including scaled versions thereof) in a base layer. In ITU-T H.265, each NAL unit may include an identifier indicating a layer of video data the NAL unit is associated with. Referring to the example illustrated in FIG. 4A, each slice of video data included in Pic₄ (i.e., Slice₁ and Slice₂) is illustrated as being encapsulated in a NAL unit. Further, in ITU-T H.265 each of a video sequence, a GOP, a picture, a slice, and CTU may be associated with metadata that describes video coding properties. ITU-T H.265 defines parameters sets that may be used to describe video data and/or video coding properties. In ITU-T H.265, parameter sets may be encapsulated as a special type of NAL unit or may be signaled as a message. NAL units including coded video data (e.g., a slice) may be referred to as VCL (Video Coding Layer) NAL units and NAL units including metadata (e.g., parameter sets) may be referred to as non-VCL NAL units. Further, ITU-T H.265 enables supplemental enhancement information (SEI) messages to be signaled. In ITU-T H.265, SEI messages assist in processes related to decoding, display or other purposes, however, SEI messages may not be required for constructing the luma or chroma samples by the decoding process. In ITU-T H.265, SEI messages may be signaled in a bitstream using non-VCL NAL units. Further, SEI messages may be conveyed by some means other than by being present in the bitstream (i.e., signaled out-of-band).

FIG. 5 illustrates an example of a bitstream including multiple CVSs, where a CVS is represented by NAL units included in a respective access unit. In the example, illustrated in FIG. 5, non-VCL NAL units include respective parameter set units (i.e., Video Parameter Sets (VPS), Sequence Parameter Sets (SPS), and Picture Parameter Set (PPS) units) and an access unit delimiter NAL unit. It should be noted that ITU-T H.265 defines NAL unit header semantics that specify the type of Raw Byte Sequence Payload (RBSP) data structure included in the NAL unit.

As described above, in ITU-T H.265, the deblocking filter may be applied differently to CTU boundaries that coincide with slice and tile boundaries compared with CTU boundaries that do not coincide with slice and tile boundaries. Specifically, ITU-T H.265 specifies a flag, slice_loop_filter_across_slices_enabled_flag, present in a slice segment header that enables/disables the deblocking filter across CTU boundaries that coincide with top and left slice boundaries. ITU-T H.265 provides the following definition for slice_loop_filter_across_slices_enabled_flag:

Similarly, a flag, loop_filter_across_tiles_enabled_flag, present in a PPS enables/disables the deblocking filter across CTU boundaries that coincide with tile boundaries. ITU-T H.265 provides the following definition for loop_filter_across_tiles_enabled_flag:

As described above, for deblocking, the index Q is determined based on slice_beta_offset_div2 and slice_tc_offset_div2. In ITU-T H.265, the values of slice_beta_offset_div2 and slice_tc_offset_div2 may be included in a slice segment header and have the following definitions:

It should be noted that the slice and tile deblocking filter controls in ITU-T H.265 are binary (i.e., may either be enabled or disabled). Binary slice and tile deblocking filter controls may be less than ideal.

FIG. 1 is a block diagram illustrating an example of a system that may be configured to code (i.e., encode and/or decode) video data according to one or more techniques of this disclosure. System 100 represents an example of a system that may encapsulate video data according to one or more techniques of this disclosure. As illustrated in FIG. 1, system 100 includes source device 102, communications medium 110, and destination device 120. In the example illustrated in FIG. 1, source device 102 may include any device configured to encode video data and transmit encoded video data to communications medium 110. Destination device 120 may include any device configured to receive encoded video data via communications medium 110 and to decode encoded video data. Source device 102 and/or destination device 120 may include computing devices equipped for wired and/or wireless communications and may include, for example, set top boxes, digital video recorders, televisions, desktop, laptop or tablet computers, gaming consoles, medical imagining devices, and mobile devices, including, for example, smartphones, cellular telephones, personal gaming devices.

Communications medium 110 may include any combination of wireless and wired communication media, and/or storage devices. Communications medium 110 may include coaxial cables, fiber optic cables, twisted pair cables, wireless transmitters and receivers, routers, switches, repeaters, base stations, or any other equipment that may be useful to facilitate communications between various devices and sites. Communications medium 110 may include one or more networks. For example, communications medium 110 may include a network configured to enable access to the World Wide Web, for example, the Internet. A network may operate according to a combination of one or more telecommunication protocols. Telecommunications protocols may include proprietary aspects and/or may include standardized telecommunication protocols. Examples of standardized telecommunications protocols include Digital Video Broadcasting (DVB) standards, Advanced Television Systems Committee (ATSC) standards, Integrated Services Digital Broadcasting (ISDB) standards, Data Over Cable Service Interface Specification (DOCSIS) standards, Global System Mobile Communications (GSM) standards, code division multiple access (CDMA) standards, 3rd Generation Partnership Project (3GPP) standards, European Telecommunications Standards Institute (ETSI) standards, Internet Protocol (IP) standards, Wireless Application Protocol (WAP) standards, and Institute of Electrical and Electronics Engineers (IEEE) standards.

Storage devices may include any type of device or storage medium capable of storing data. A storage medium may include a tangible or non-transitory computer-readable media. A computer readable medium may include optical discs, flash memory, magnetic memory, or any other suitable digital storage media. In some examples, a memory device or portions thereof may be described as non-volatile memory and in other examples portions of memory devices may be described as volatile memory. Examples of volatile memories may include random access memories (RAM), dynamic random access memories (DRAM), and static random access memories (SRAM). Examples of non-volatile memories may include magnetic hard discs, optical discs, floppy discs, flash memories, or forms of electrically programmable memories (EPROM) or electrically erasable and programmable (EEPROM) memories. Storage device(s) may include memory cards (e.g., a Secure Digital (SD) memory card), internal/external hard disk drives, and/or internal/external solid state drives. Data may be stored on a storage device according to a defined file format.

FIG. 6 is a conceptual drawing illustrating an example of components that may be included in an implementation of system 100. In the example implementation illustrated in FIG. 6, system 100 includes one or more computing devices 602A-602N, television service network 604, television service provider site 606, wide area network 608, local area network 610, and one or more content provider sites 612A-612N. The implementation illustrated in FIG. 6 represents an example of a system that may be configured to allow digital media content, such as, for example, a movie, a live sporting event, etc., and data and applications and media presentations associated therewith to be distributed to and accessed by a plurality of computing devices, such as computing devices 602A-602N. In the example illustrated in FIG. 6, computing devices 602A-602N may include any device configured to receive data from one or more of television service network 604, wide area network 608, and/or local area network 610. For example, computing devices 602A-602N may be equipped for wired and/or wireless communications and may be configured to receive services through one or more data channels and may include televisions, including so-called smart televisions, set top boxes, and digital video recorders. Further, computing devices 602A-602N may include desktop, laptop, or tablet computers, gaming consoles, mobile devices, including, for example, “smart” phones, cellular telephones, and personal gaming devices.

Television service network 604 is an example of a network configured to enable digital media content, which may include television services, to be distributed. For example, television service network 604 may include public over-the-air television networks, public or subscription-based satellite television service provider networks, and public or subscription-based cable television provider networks and/or over the top or Internet service providers. It should be noted that although in some examples television service network 604 may primarily be used to enable television services to be provided, television service network 604 may also enable other types of data and services to be provided according to any combination of the telecommunication protocols described herein. Further, it should be noted that in some examples, television service network 604 may enable two-way communications between television service provider site 406 and one or more of computing devices 602A-602N. Television service network 604 may comprise any combination of wireless and/or wired communication media. Television service network 604 may include coaxial cables, fiber optic cables, twisted pair cables, wireless transmitters and receivers, routers, switches, repeaters, base stations, or any other equipment that may be useful to facilitate communications between various devices and sites. Television service network 604 may operate according to a combination of one or more telecommunication protocols. Telecommunications protocols may include proprietary aspects and/or may include standardized telecommunication protocols. Examples of standardized telecommunications protocols include DVB standards, ATSC standards, and ISDB standards.

Referring again to FIG. 6, television service provider site 606 may be configured to distribute television service via television service network 604. For example, television service provider site 606 may include one or more broadcast stations, a cable television provider, or a satellite television provider, or an Internet-based television provider. For example, television service provider site 606 may be configured to receive a transmission including television programming through a satellite uplink/downlink. Further, as illustrated in FIG. 6, television service provider site 606 may be in communication with wide area network 608 and may be configured to receive data from content provider sites 612A-612N. It should be noted that in some examples, television service provider site 606 may include a television studio and content may originate therefrom.

Wide area network 608 may include a packet based network and operate according to a combination of one or more telecommunication protocols. Telecommunications protocols may include proprietary aspects and/or may include standardized telecommunication protocols. Examples of standardized telecommunications protocols include Global System Mobile Communications (GSM) standards, code division multiple access (CDMA) standards, 3^rd Generation Partnership Project (3GPP) standards, European Telecommunications Standards Institute (ETSI) standards, European standards (EN), IP standards, Wireless Application Protocol (WAP) standards, and Institute of Electrical and Electronics Engineers (IEEE) standards, such as, for example, one or more of the IEEE 802 standards (e.g., Wi-Fi). Wide area network 608 may comprise any combination of wireless and/or wired communication media. Wide area network 608 may include coaxial cables, fiber optic cables, twisted pair cables, Ethernet cables, wireless transmitters and receivers, routers, switches, repeaters, base stations, or any other equipment that may be useful to facilitate communications between various devices and sites. In one example, wide area network 608 may include the Internet. Local area network 610 may include a packet based network and operate according to a combination of one or more telecommunication protocols. Local area network 610 may be distinguished from wide area network 608 based on levels of access and/or physical infrastructure. For example, local area network 410 may include a secure home network.

Referring again to FIG. 6, content provider sites 612A-612N represent examples of sites that may provide multimedia content to television service provider site 606 and/or computing devices 602A-602N. For example, a content provider site may include a studio having one or more studio content servers configured to provide multimedia files and/or streams to television service provider site 606. In one example, content provider sites 612A-612N may be configured to provide multimedia content using the IP suite. For example, a content provider site may be configured to provide multimedia content to a receiver device according to Real Time Streaming Protocol (RTSP), or the like. Further, content provider sites 612A-612N may be configured to provide data, including hypertext based content, and the like, to one or more of receiver devices computing devices 602A-602N and/or television service provider site 606 through wide area network 608. Content provider sites 612A-612N may include one or more web servers. Data provided by data provider site 612A-612N may be defined according to data formats.

Referring again to FIG. 1, source device 102 includes video source 104, video encoder 106, data encapsulator 107, and interface 108. Video source 104 may include any device configured to capture and/or store video data. For example, video source 104 may include a video camera and a storage device operably coupled thereto. Video encoder 106 may include any device configured to receive video data and generate a compliant bitstream representing the video data. A compliant bitstream may refer to a bitstream that a video decoder can receive and reproduce video data therefrom. Aspects of a compliant bitstream may be defined according to a video coding standard. When generating a compliant bitstream video encoder 106 may compress video data. Compression may be lossy (discernible or indiscernible to a viewer) or lossless.

FIG. 7 is a block diagram illustrating an example of video encoder 700 that may implement the techniques for encoding video data described herein. It should be noted that although example video encoder 700 is illustrated as having distinct functional blocks, such an illustration is for descriptive purposes and does not limit video encoder 700 and/or sub-components thereof to a particular hardware or software architecture. Functions of video encoder 700 may be realized using any combination of hardware, firmware, and/or software implementations. In one example, video encoder 700 may be configured to encode video data according to the techniques described herein. Video encoder 700 may perform intra prediction coding and inter prediction coding of picture areas, and, as such, may be referred to as a hybrid video encoder. In the example illustrated in FIG. 7, video encoder 700 receives source video blocks. In some examples, source video blocks may include areas of picture that has been divided according to a coding structure. For example, source video data may include macroblocks, CTUs, CBs, sub-divisions thereof, and/or another equivalent coding unit. In some examples, video encoder may be configured to perform additional sub-divisions of source video blocks. It should be noted that the techniques described herein are generally applicable to video coding, regardless of how source video data is partitioned prior to and/or during encoding. In the example illustrated in FIG. 7, video encoder 700 includes summer 702, transform coefficient generator 704, coefficient quantization unit 706, inverse quantization/transform processing unit 708, summer 710, intra prediction processing unit 712, inter prediction processing unit 714, filter unit 716, and entropy encoding unit 718. As illustrated in FIG. 7, video encoder 700 receives source video blocks and outputs a bitstream.

In the example illustrated in FIG. 7, video encoder 700 may generate residual data by subtracting a predictive video block from a source video block. Summer 702 represents a component configured to perform this subtraction operation. In one example, the subtraction of video blocks occurs in the pixel domain. Transform coefficient generator 704 applies a transform, such as a discrete cosine transform (DCT), a discrete sine transform (DST), or a conceptually similar transform, to the residual block or sub-divisions thereof (e.g., four 8x8 transforms may be applied to a 16x16 array of residual values) to produce a set of residual transform coefficients. Transform coefficient generator 704 may be configured to perform any and all combinations of the transforms included in the family of discrete trigonometric transforms. Transform coefficient generator 704 may output transform coefficients to coefficient quantization unit 706.

Coefficient quantization unit 706 may be configured to perform quantization of the transform coefficients. As described above, the degree of quantization may be modified by adjusting a quantization scaling factor which may be determined by quantization parameters. Coefficient quantization unit 706 may be further configured to determine quantization values and output QP data that may be used by a video decoder to reconstruct a quantization parameter to perform inverse quantization during video decoding. For example, signaled QP data may include QP delta values. In ITU-T H.265, the degree of quantization applied to a set of transform coefficients may depend on slice level parameters, parameters inherited from a previous coding unit, and/or optionally signaled CU level delta values.

As illustrated in FIG. 7, quantized transform coefficients are output to inverse quantization/transform processing unit 708. Inverse quantization/transform processing unit 708 may be configured to apply an inverse quantization and/or an inverse transformation to generate reconstructed residual data. As illustrated in FIG. 7, at summer 710, reconstructed residual data may be added to a predictive video block. In this manner, an encoded video block may be reconstructed and the resulting reconstructed video block may be used to evaluate the encoding quality for a given quality for a given prediction, transformation type, and/or level of quantization. Video encoder 700 may be configured to perform multiple coding passes (e.g., perform encoding while varying one or more coding parameters). The rate-distortion of a bitstream or other system parameters may be optimized based on evaluation of reconstructed video blocks. Further, reconstructed video blocks may be stored and used as reference for predicting subsequent blocks.

As described above, a video block may be coded using an intra prediction. Intra prediction processing unit 712 may be configured to select an intra prediction mode for a video block to be coded. Intra prediction processing unit 712 may be configured to evaluate a frame and/or an area thereof and determine an intra prediction mode to use to encode a current block. As illustrated in FIG. 7, intra prediction processing unit 712 outputs intra prediction data (e.g., syntax elements) to filter unit 716 and entropy encoding unit 718.

Inter prediction processing unit 714 may be configured to perform inter prediction coding for a current video block. Inter prediction processing unit 714 may be configured to receive source video blocks and calculate a motion vector for PUs, or the like, of a video block. A motion vector may indicate the displacement of a PU, or the like, of a video block within a current video frame relative to a predictive block within a reference frame. Inter prediction coding may use one or more reference pictures. Further, motion prediction may be uni-predictive (use one motion vector) or bi-predictive (use two motion vectors). Inter prediction processing unit 714 may be configured to select a predictive block by calculating a pixel difference determined by, for example, sum of absolute difference (SAD), sum of square difference (SSD), or other difference metrics. A motion vector and associated data may describe, for example, a horizontal component of the motion vector, a vertical component of the motion vector, a resolution for the motion vector (e.g., one-quarter pixel precision), a prediction direction and/or a reference picture index value. Further, a coding standard, such as, for example ITU-T H.265, may support motion vector prediction. Motion vector prediction enables a motion vector to be specified using motion vectors of neighboring blocks. Examples of motion vector prediction include advanced motion vector prediction (AMVP), temporal motion vector prediction (TMVP), so-called “merge” mode, and “skip” and “direct” motion inference. Inter prediction processing unit 714 may be configured to perform motion vector prediction according to one or more of the techniques described above. Inter prediction processing unit 714 may be configured to generate a predictive block using the motion prediction data. For example, inter prediction processing unit 714 may locate a predictive video block within a frame buffer (not shown in FIG. 8). It should be noted that inter prediction processing unit 714 may further be configured to apply one or more interpolation filters to a reconstructed residual block to calculate sub-integer pixel values for use in motion estimation. Inter prediction processing unit 714 may output motion prediction data for a calculated motion vector to filter unit 716 and entropy encoding unit 718.

As described above, deblocking refers to the process of smoothing the boundaries of reconstructed video blocks. As illustrated in FIG. 7, filter unit 716 receives reconstructed video blocks and coding parameters (e.g., intra prediction data, inter prediction data, and QP data) and outputs modified reconstructed video data. Filter unit 716 may be configured to perform deblocking and/or Sample Adaptive Offset (SAO) filtering. SAO filtering is a non-linear amplitude mapping that may be used to improve reconstruction by adding an offset to reconstructed video data. It should be noted that as illustrated in FIG. 7, intra prediction processing unit 712 and inter prediction processing unit 714 may receive modified reconstructed video block via filter unit 716. That is, in some cases, deblocking may occur in-loop, i.e., predictive video blocks stored in a reference buffer may be filtered. In some cases, deblocking may occur post-loop, i.e., after video data has been reconstructed and prior to being output to a display, for example. The techniques described herein may be applicable in-loop deblocking, post-loop deblocking, and/or combinations thereof.

As described above, ITU-T H.265 includes slice and tile deblocking filter controls that are binary and thus less than ideal. According to the techniques described herein, a video encoder and/or video decoder and/or a filter unit thereof may be configured to adjust how deblocking is applied for video block boundaries that coincide with slice and tile boundaries. For example, CTU boundaries that coincide with top and left slice boundaries and tile boundaries may benefit from different filter strengths compared with CTU boundaries that do not coincide with slice or tile boundaries. According to the techniques described herein, new parameters may be introduced and the derivation of the index value, Q, to control deblocking filter strength may be modified for CTU boundaries that coincide with the top and left slice boundaries and tile boundaries.

In one example, according to the techniques described herein, the derivation of Q for CTU boundaries that coincide with top and left slice boundaries and tile boundaries may be as follows:

In one example, pps_beta_offset_stb_div2 and pps_tc_offset_stb_div2 are syntax elements included in a PPS and may be based on the following example definition:

In one example, pps_beta_offset_stb_div2 and pps_tc_offset_stb_div2 may be included in a PPS immediately following syntax elements pps_beta_offset_div2 and pps_tc_offset_div2.

It should be noted that, in one example, in the case where tiles overlap one another, the derivation of Q described above may be applied to CTU boundaries coinciding with the tile boundaries prior to any boundary extension, where the extension of the tile boundaries creates overlap.

In the example derivation of Q described above, the same parameters are used to derive Q for CTU boundaries coinciding with top and left slice and tile boundaries. In some cases, it may be advantageous to have separate filter strength control for tiles and slices. In one example, the derivation of Q for CTU boundaries that coincide with top and left slice boundaries may be derived as provided above and the derivation of Q for CTU boundaries that coincide with tile boundaries may be as follows:

In one example, pps_beta_offset_tile_div2 and pps_tc_offset_tile_div2 syntax elements may be included in a PPS and may be based on the following example definition:

It should be noted that in this example, the definitions of pps_beta_offset_stb_div2 and pps_tc_offset_stb_div2 may be modified to specify the slice deblocking parameter offsets for β and tC (divided by 2) for slices for which the PPS is active.

It should be noted that in some cases, a CTU may coincide with both a slice boundary and a tile boundary. In one example, in the case where separate filter strength controls are enabled for tiles and slices, in one example, in the case where a boundary is collocated with both a slice and tile boundary one of either the filter strength control for tiles or the filter strength control for slices is used to derive Q. For example, the filter strength control for tiles may be used. Alternatively, in one example, the filter strength control for tiles and the filter strength control for slices are both used to derive Q. For example, the filter strength control may be equal to the maximum of the tile filter strength control and slice filter strength control, the minimum of the tile filter strength control and slice filter strength control, the average of the tile filter strength control and slice filter strength control, or other combination. That is, in one example, in the case where the filter strength control is equal to the maximum of the tile filter strength control and slice filter strength control, the derivation of Q may be as follows:

In some example, parameters that indicate offset values may be included in the VPS or SPS. For example, syntax elements vps_beta_offset_stb_div2 and vps_tc_offset_stb_div2 may be included in a VPS and/or syntax elements sps_beta_offset_stb_div2 and sps_tc_offset_stb_div2 may be included in an SPS, where vps_beta_offset_stb_div2, vps_tc_offset_stb_div2, sps_beta_offset_stb_div2, and/or sps_tc_offset_stb_div2 are used to infer values for pps_beta_offset_stb_div2, pps_tc_offset_stb_div2. Similarly values for pps_beta_offset_tile_div2 and/or pps_tc_offset_tile_div2 may be inferred from vps_beta_offset_tile_div2, vps_tc_offset_tile_div2, sps_beta_offset_tile_div2, and/or sps_tc_offset_tile_div2.

As described above, a MCTS may include a tile set for which inter-picture prediction dependencies are limited to the collocated tile sets in reference pictures. In some cases, CTU boundaries that coincide with MCTS boundaries (or other tile set boundaries) may benefit from different filter strengths compared with CTU boundaries that do not coincide with MCTS boundaries. In one example, according to the techniques described herein, the derivation of Q for CTU boundaries that coincide with MCTS boundaries may be as follows:

In one example, pps_beta_offset_tile_set_div2 and pps_tc_offset_tile_set_div2 are syntax elements included in a PPS and may be based on the following example definition:

In some example, parameters that indicate tile set offset values may be included in the VPS or SPS. For example, syntax elements vps_beta_offset_tile_set_div2 and vps_tc_offset_tile_set_div2 may be included in a VPS and/or syntax elements sps_beta_offset_tile_set_div2 and sps_tc_offset_tile_set_div2 may be included in an SPS, where vps_beta_offset_tile_set_div2, vps_tc_offset_tile_set_div2, sps_beta_offset_tile_set_div2, and/or sps_tc_offset_tile_set_div2 are used to infer values for pps_beta_offset_tile_set_div2, and/or pps_tc_offset_tile_set_div2.

It should be noted that in the case in which tiles overlap one another, the deblocking filter strength derivation may be applied to CTU boundaries coinciding with the tile boundaries prior to any boundary extensions, where the extension of the tile boundaries creates overlap.

ITU-T H.265 provides a Screen content coding (SCC) extension profile. The deblocking filter strength in the SCC Profile differs from that in other profiles in that a modified clipping operation is used to avoid blurring high-contrast edges in the reconstructed picture. In one example, according to the techniques described herein, when text or graphics are detected for a region of a picture, the index Q calculation may be computed as follows:

It should be noted that although the index value Q is described herein as indexing values of β’ and tc’ according to the table illustrated in FIG. 3, the techniques described herein are equally applicable to values of Q, β’, and/or tc’ having different ranges and correspondence than those illustrated in FIG. 3.

Referring again to FIG. 7, entropy encoding unit 718 receives quantized transform coefficients and predictive syntax data (i.e., intra prediction data and motion prediction data). It should be noted that in some examples, coefficient quantization unit 706 may perform a scan of a matrix including quantized transform coefficients before the coefficients are output to entropy encoding unit 718. In other examples, entropy encoding unit 718 may perform a scan. Entropy encoding unit 718 may be configured to perform entropy encoding according to one or more of the techniques described herein. In this manner, video encoder 700 represents an example of a device configured to receive an array of sample values including adjacent reconstructed video blocks for a component of video data, wherein the array of sample values coincides with a picture partitioning boundary, determining one or more offset values associated with the picture partitioning boundary, select a filter based on the determined offset values and modify sample values in the adjacent reconstructed video blocks based on the selected filter.

Referring again to FIG. 1, data encapsulator 107 may receive encoded video data and generate a compliant bitstream, e.g., a sequence of NAL units according to a defined data structure. A device receiving a compliant bitstream can reproduce video data therefrom. Further, a device receiving a compliant bitstream may perform a sub-bitstream extraction process, where sub-bitstream extraction refers to a process where a device receiving a compliant bitstream forms a new compliant bitstream by discarding and/or modifying data in the received bitstream. It should be noted that the term conforming bitstream may be used in place of the term compliant bitstream.

Referring again to FIG. 1, interface 108 may include any device configured to receive data generated by data encapsulator 107 and transmit and/or store the data to a communications medium. Interface 108 may include a network interface card, such as an Ethernet card, and may include an optical transceiver, a radio frequency transceiver, or any other type of device that can send and/or receive information. Further, interface 108 may include a computer system interface that may enable a file to be stored on a storage device. For example, interface 108 may include a chipset supporting Peripheral Component Interconnect (PCI) and Peripheral Component Interconnect Express (PCIe) bus protocols, proprietary bus protocols, Universal Serial Bus (USB) protocols, I²C, or any other logical and physical structure that may be used to interconnect peer devices.

Referring again to FIG. 1, destination device 120 includes interface 122, data decapsulator 123, video decoder 124, and display 126. Interface 122 may include any device configured to receive data from a communications medium. Interface 122 may include a network interface card, such as an Ethernet card, and may include an optical transceiver, a radio frequency transceiver, or any other type of device that can receive and/or send information. Further, interface 122 may include a computer system interface enabling a compliant video bitstream to be retrieved from a storage device. For example, interface 122 may include a chipset supporting PCI and PCIe bus protocols, proprietary bus protocols, USB protocols, I²C, or any other logical and physical structure that may be used to interconnect peer devices. Data decapsulator 123 may be configured to receive and parse any of the example parameter sets described herein.

Video decoder 124 may include any device configured to receive a bitstream and/or acceptable variations thereof and reproduce video data therefrom. Display 126 may include any device configured to display video data. Display 126 may comprise one of a variety of display devices such as a liquid crystal display (LCD), a plasma display, an organic light emitting diode (OLED) display, or another type of display. Display 126 may include a High Definition display or an Ultra High Definition display. It should be noted that although in the example illustrated in FIG. 1, video decoder 124 is described as outputting data to display 126, video decoder 124 may be configured to output video data to various types of devices and/or sub-components thereof. For example, video decoder 124 may be configured to output video data to any communication medium, as described herein.

FIG. 8 is a block diagram illustrating an example of a video decoder that may be configured to decode video data according to one or more techniques of this disclosure. In one example, video decoder 800 may be configured to decode transform data and reconstruct residual data from transform coefficients based on decoded transform data. Video decoder 800 may be configured to perform intra prediction decoding and inter prediction decoding and, as such, may be referred to as a hybrid decoder. In the example illustrated in FIG. 8, video decoder 800 includes an entropy decoding unit 802, inverse quantization unit 804, inverse transform coefficient processing unit 806, intra prediction processing unit 808, inter prediction processing unit 810, summer 812, filter unit 814, and reference buffer 816. Video decoder 800 may be configured to decode video data in a manner consistent with a video coding system. It should be noted that although example video decoder 800 is illustrated as having distinct functional blocks, such an illustration is for descriptive purposes and does not limit video decoder 800 and/or sub-components thereof to a particular hardware or software architecture. Functions of video decoder 800 may be realized using any combination of hardware, firmware, and/or software implementations.

As illustrated in FIG. 8, entropy decoding unit 802 receives an entropy encoded bitstream. Entropy decoding unit 802 may be configured to decode syntax elements and quantized coefficients from the bitstream according to a process reciprocal to an entropy encoding process. Entropy decoding unit 802 may be configured to perform entropy decoding according any of the entropy coding techniques described above. Entropy decoding unit 802 may determine values for syntax elements in an encoded bitstream in a manner consistent with a video coding standard. As illustrated in FIG. 8, entropy decoding unit 802 may determine quantized coefficient values and predication data from a bitstream. In the example illustrated in FIG. 8, inverse quantization unit 804 receives quantized coefficient values and outputs transform coefficients. Inverse transform processing unit 806 receives transform coefficients and outputs reconstructed residual data.

Referring again to FIG. 8, reconstructed residual data may be provided to summer 812. Summer 812 may add reconstructed residual data to a predictive video block and generate reconstructed video data. A predictive video block may be determined according to a predictive video technique (i.e., intra prediction and inter frame prediction). Intra prediction processing unit 808 may be configured to receive intra prediction syntax elements and retrieve a predictive video block from reference buffer 816. Reference buffer 816 may include a memory device configured to store one or more frames of video data. Intra prediction syntax elements may identify an intra prediction mode, such as the intra prediction modes described above. Inter prediction processing unit 808 may receive inter prediction syntax elements and generate motion vectors to identify a prediction block in one or more reference frames stored in reference buffer 816. Inter prediction processing unit 810 may produce motion compensated blocks, possibly performing interpolation based on interpolation filters. Identifiers for interpolation filters to be used for motion estimation with sub-pixel precision may be included in the syntax elements. Inter prediction processing unit 810 may use interpolation filters to calculate interpolated values for sub-integer pixels of a reference block.

Filter unit 814 may be configured to perform filtering on reconstructed video data. For example, filter unit 814 may be configured to perform deblocking and/or Sample Adaptive Offset (SAO) filtering, e.g., based on parameters specified in a bitstream. Further, it should be noted that in some examples, filter unit 814 may be configured to perform proprietary discretionary filtering (e.g., visual enhancements, such as, mosquito noise reduction). Filter unit 814 may operate in a similar manner to filter unit 716. As described above, according to the techniques described herein, a filter unit may be configured to adjust how deblocking is applied for video block boundaries that coincide with slice and tile boundaries. As illustrated in FIG. 8, a reconstructed video block may be output by video decoder 800. In this manner, video decoder 800 may be configured to receive an array of sample values including adjacent reconstructed video blocks for a component of video data, wherein the array of sample values coincides with a picture partitioning boundary, determining one or more offset values associated with the picture partitioning boundary, select a filter based on the determined offset values and modify sample values in the adjacent reconstructed video blocks based on the selected filter.

In one or more examples, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium and executed by a hardware-based processing unit. Computer-readable media may include computer-readable storage media, which corresponds to a tangible medium such as data storage media, or communication media including any medium that facilitates transfer of a computer program from one place to another, e.g., according to a communication protocol. In this manner, computer-readable media generally may correspond to (1) tangible computer-readable storage media which is non-transitory or (2) a communication medium such as a signal or carrier wave. Data storage media may be any available media that can be accessed by one or more computers or one or more processors to retrieve instructions, code and/or data structures for implementation of the techniques described in this disclosure. A computer program product may include a computer-readable medium.

By way of example, and not limitation, such computer-readable storage media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage, or other magnetic storage devices, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer. Also, any connection is properly termed a computer-readable medium. For example, if instructions are transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. It should be understood, however, that computer-readable storage media and data storage media do not include connections, carrier waves, signals, or other transitory media, but are instead directed to non-transitory, tangible storage media. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.

Instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general purpose microprocessors, application specific integrated circuits (ASICs), field programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuitry. Accordingly, the term “processor,” as used herein may refer to any of the foregoing structure or any other structure suitable for implementation of the techniques described herein. In addition, in some aspects, the functionality described herein may be provided within dedicated hardware and/or software modules configured for encoding and decoding, or incorporated in a combined codec. Also, the techniques could be fully implemented in one or more circuits or logic elements.

The techniques of this disclosure may be implemented in a wide variety of devices or apparatuses, including a wireless handset, an integrated circuit (IC) or a set of ICs (e.g., a chip set). Various components, modules, or units are described in this disclosure to emphasize functional aspects of devices configured to perform the disclosed techniques, but do not necessarily require realization by different hardware units. Rather, as described above, various units may be combined in a codec hardware unit or provided by a collection of interoperative hardware units, including one or more processors as described above, in conjunction with suitable software and/or firmware.

Moreover, each functional block or various features of the base station device and the terminal device used in each of the aforementioned embodiments may be implemented or executed by a circuitry, which is typically an integrated circuit or a plurality of integrated circuits. The circuitry designed to execute the functions described in the present specification may comprise a general-purpose processor, a digital signal processor (DSP), an application specific or general application integrated circuit (ASIC), a field programmable gate array (FPGA), or other programmable logic devices, discrete gates or transistor logic, or a discrete hardware component, or a combination thereof. The general-purpose processor may be a microprocessor, or alternatively, the processor may be a conventional processor, a controller, a microcontroller or a state machine. The general-purpose processor or each circuit described above may be configured by a digital circuit or may be configured by an analogue circuit. Further, when a technology of making into an integrated circuit superseding integrated circuits at the present time appears due to advancement of a semiconductor technology, the integrated circuit by this technology is also able to be used.

Various examples have been described. These and other examples are within the scope of the following claims.

<Cross Reference>
This Nonprovisional application claims priority under 35 U.S.C. § 119 on provisional Application No. 62/608,525 on December 20, 2017 the entire contents of which are hereby incorporated by reference.

Claims

A method of filtering reconstructed video data, the method comprising:
receiving an array of sample values including adjacent reconstructed video blocks for a component of video data, wherein the array of sample values coincides with a picture partitioning boundary;
determining one or more offset values associated with the picture partitioning boundary;
selecting a filter based on the determined offset values; and
modifying sample values in the adjacent reconstructed video blocks based on the selected filter.
The method of claim 1, wherein a picture partitioning boundary includes a slice boundary or a tile boundary.
The method of any of claims 1 or 2, wherein selecting a filter based on the determined offset values includes selecting a deblocking filter based on the determined offset values.
The method of claim 3, wherein selecting a filter based on the determined offset values includes determining the strength of a deblocking filter.
The method of any of claims 1-4, further comprising signaling the one or more offsets value associated with the picture partitioning boundary in a parameter set.
The method of any of claims 1-4, further comprising receiving the one or more offsets value associated with the picture partitioning boundary in a parameter set.
A device for coding video data, the device comprising one or more processors configured to perform any and all combinations of the steps of claims 1-6.
The device of claim 7, wherein the device includes a video encoder.
The device of claim 7, wherein the device includes a video decoder.
A system comprising:
the device of claim 8; and
the device of claim 9.
An apparatus for coding video data, the apparatus comprising means for performing any and all combinations of the steps of claims 1-6.
A non-transitory computer-readable storage medium comprising instructions stored thereon that, when executed, cause one or more processors of a device for coding video data to perform any and all combinations of the steps of claims 1-6.