WO2018180841A1 - Systèmes et procédés de filtrage de données vidéo reconstruites à l'aide de techniques de filtrage bilatéral - Google Patents

Systèmes et procédés de filtrage de données vidéo reconstruites à l'aide de techniques de filtrage bilatéral Download PDF

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WO2018180841A1
WO2018180841A1 PCT/JP2018/011293 JP2018011293W WO2018180841A1 WO 2018180841 A1 WO2018180841 A1 WO 2018180841A1 JP 2018011293 W JP2018011293 W JP 2018011293W WO 2018180841 A1 WO2018180841 A1 WO 2018180841A1
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video
bilateral
coding
bilateral filter
video data
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PCT/JP2018/011293
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Kiran Mukesh MISRA
Jie Zhao
Christopher Andrew Segall
Philip Cowan
Tomohiro Ikai
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Sharp Kabushiki Kaisha
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/80—Details of filtering operations specially adapted for video compression, e.g. for pixel interpolation
    • H04N19/82—Details of filtering operations specially adapted for video compression, e.g. for pixel interpolation involving filtering within a prediction loop
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/102—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or selection affected or controlled by the adaptive coding
    • H04N19/117—Filters, e.g. for pre-processing or post-processing
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/46—Embedding additional information in the video signal during the compression process
    • H04N19/463—Embedding additional information in the video signal during the compression process by compressing encoding parameters before transmission
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/85—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using pre-processing or post-processing specially adapted for video compression
    • H04N19/86—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using pre-processing or post-processing specially adapted for video compression involving reduction of coding artifacts, e.g. of blockiness
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/102—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or selection affected or controlled by the adaptive coding
    • H04N19/119—Adaptive subdivision aspects, e.g. subdivision of a picture into rectangular or non-rectangular coding blocks
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/102—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or selection affected or controlled by the adaptive coding
    • H04N19/124—Quantisation

Definitions

  • This disclosure relates to video coding and more particularly to techniques for filtering 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 April 2015, which is incorporated by reference, and referred to herein as ITU-T H.265.
  • ITU-T H.265 Extensions and improvements for ITU-T H.265 are currently being considered for development of next generation video coding standards.
  • ITU-T Video Coding Experts Group (VCEG) and ISO/IEC (Moving Picture Experts Group (MPEG) 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.
  • JVET Joint Video Exploration Team
  • JEM 3 Joint Exploration Model 3
  • JEM 3 Algorithm Description of Joint Exploration Test Model 3
  • JEM 3 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.
  • the coding features of JEM 3 are implemented in JEM reference software maintained by the Fraunhofer research organization.
  • JEM 3.0 the updated JEM reference software version 3 (JEM 3.0) is available.
  • JEM is used to collectively refer to algorithms included in JEM 3 and implementations of JEM reference software.
  • Video compression techniques enable data requirements for storing and transmitting video data to be reduced. Video compression techniques may reduce data requirements 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.
  • Intra prediction coding techniques e.g., intra-picture (spatial)
  • inter prediction techniques i.e., inter-picture (temporal)
  • 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.
  • this disclosure describes various techniques for coding video data.
  • this disclosure describes techniques for filtering reconstructed video data.
  • this disclosure describes techniques of this disclosure with respect to ITU-T H.264, ITU-T H.265, and JEM, the techniques of this disclosure are generally applicable to video coding.
  • 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 and JEM.
  • ITU-T H.264, ITU-T H.265, and/or JEM is for descriptive purposes and should not be construed to limit the scope of the techniques described herein.
  • incorporation by reference of documents herein is for descriptive purposes and should not be construed to limit or create ambiguity with respect to terms 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.
  • a method of coding of video data comprises receiving an array of sample values for a component of video data, determining whether to apply a bilateral filter to the array of sample values based on one or more bilateral filter control parameters, and outputting an array of modified samples values, wherein the array of samples are modified based according to an applied bilateral filter.
  • a device for coding video data comprises one or more processors configured to receive an array of sample values for a component of video data, determine whether to apply a bilateral filter to the array of sample values based on one or more bilateral filter control parameters, and output an array of modified samples values, wherein the array of samples are modified based according to an applied bilateral filter.
  • 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 for a component of video data, determine whether to apply a bilateral filter to the array of sample values based on one or more bilateral filter control parameters, and output an array of modified samples values, wherein the array of samples are modified based according to an applied bilateral filter.
  • FIG. 1 is a conceptual diagram illustrating an example of a group of pictures coded according to a quad tree binary tree partitioning in accordance with one or more techniques of this disclosure.
  • FIG. 2 is a conceptual diagram illustrating an example of a video component sampling format in accordance with one or more techniques of this disclosure.
  • FIG. 3 is a conceptual diagram illustrating possible coding structures for a block of video data according to one or more techniques of this disclosure.
  • FIG. 4A is a conceptual diagram illustrating an example of coding a block of video data in accordance with one or more techniques of this disclosure.
  • FIG. 4B is a conceptual diagram illustrating an example of coding a block of video data in accordance with one or more techniques of this disclosure.
  • FIG. 1 is a conceptual diagram illustrating an example of a group of pictures coded according to a quad tree binary tree partitioning in accordance with one or more techniques of this disclosure.
  • FIG. 2 is a conceptual diagram illustrating an example of a video component sampling format in accordance with one or more techniques of
  • FIG. 5 is a conceptual diagram illustrating an example of bilateral filtering of video data in accordance with one or more techniques of this disclosure.
  • FIG. 6 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 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.
  • FIG. 9 is a block diagram illustrating an example of a filter unit that may be configured to modify reconstructed video data according to one or more techniques of this disclosure.
  • FIG. 10A is a block diagram illustrating an example of a sample modification units that may be configured to filter video data according to one or more techniques of this disclosure.
  • FIG. 10B is a block diagram illustrating an example of a sample modification units that may be configured to filter video data according to one or more techniques of this disclosure.
  • FIG. 10C is a block diagram illustrating an example of a sample modification units that may be configured to filter video data according to one or more techniques of this disclosure.
  • Video content typically includes video sequences comprised of a series of frames (or pictures).
  • 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.
  • 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.
  • 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.
  • pixel values may be described as including sample values for 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. Further, it should be noted that sample values may be described as having an intensity or an amplitude.
  • 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 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. 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.
  • 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).
  • CTB Coding Tree Blocks
  • 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.
  • QT quadtree
  • ITU-T H.265 a CU is associated with a prediction unit (PU) structure having its root at the CU.
  • 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.
  • PBs chroma prediction blocks
  • 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.
  • 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 sizes type include MxM or M/2xM/2, where M is the height and width of the square CB).
  • intra prediction PB sizes type include MxM or M/2xM/2, where M is the height and width of the square CB.
  • 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).
  • ITU-T H.265 for inter prediction, four asymmetric PB partitions are supported, where the CB is partitioned to 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
  • inter prediction data e.g., motion data syntax elements
  • JEM specifies a CTU having a maximum size of 256x256 luma samples.
  • JEM specifies a quadtree plus binary tree (QTBT) block structure.
  • 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.
  • FIG. 1 illustrates an example of a CTU (e.g., a CTU having a size of 256x256 luma samples) being partitioned into quadtree leaf nodes and quadtree leaf nodes being further partitioned according to a binary tree. That is, in FIG.
  • 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 QTBT structure.
  • FIG. 1 illustrates an example of QTBT partitioning for one CTU included in a slice.
  • a QTBT is signaled by signaling QT split flag and BT split mode syntax elements.
  • luma and chroma components may have separate QTBT partitions. That is, in JEM, luma and chroma components may be partitioned independently by signaling respective QTBTs.
  • 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.
  • a JEM QTBT leaf node may be analogous a PB in ITU-T H.265.
  • a video sampling format which may also be referred to as a chroma format, may define the number of chroma samples included in a CU with respect to the number of luma samples included in a CU.
  • the sampling rate for the luma component is twice that of the chroma components for both the horizontal and vertical directions.
  • the width and height of an array of samples for the luma component are twice that of each array of samples for the chroma components.
  • FIG. 2 is a conceptual diagram illustrating an example of a coding unit formatted according to a 4:2:0 sample format.
  • a 16x16 CU formatted according to the 4:2:0 sample format includes 16x16 samples of luma components and 8x8 samples for each chroma component.
  • the relative position of chroma samples with respect to luma samples for video blocks neighboring the 16x16 CU are illustrated.
  • the width of an array of samples for the luma component is twice that of the width of an array of samples for each chroma component, but the height of the array of samples for the luma component is equal to the height of an array of samples for each chroma component.
  • an array of samples for the luma component has the same width and height as an array of samples for each chroma component.
  • intra prediction data or inter prediction data is used to produce reference sample values for a block of sample values.
  • the difference between sample values included in a current PB, or another type of picture area structure, and associated reference samples (e.g., those generated using a prediction) may be referred to as residual data.
  • 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.
  • an intra prediction mode may specify the location of reference samples within a picture.
  • 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).
  • 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.
  • a motion vector 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.
  • 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.
  • JEM supports advanced temporal motion vector prediction (ATMVP) and Spatial-temporal motion vector prediction (STMVP).
  • Residual data may include respective arrays of difference values corresponding to each component of video data. 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 an array of difference values to generate transform coefficients.
  • DCT discrete cosine transform
  • DST discrete sine transform
  • an integer transform e.g., a wavelet transform, or a conceptually similar transform
  • ITU-T H.265 a CU is associated with a transform unit (TU) structure having its root at the CU level. That is, in ITU-T H.265, an array of 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).
  • TBs Transform Blocks
  • ITU-T H.265 TBs are not necessarily aligned with PBs.
  • FIG. 3 illustrates examples of alternative PB and TB combinations that may be used for coding a particular CB.
  • 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.
  • a quantization process may be performed on transform coefficients. Quantization approximates transform coefficients by amplitudes restricted to a set of specified values. Coefficient scaling may be used in conjunction with quantization in order to vary the amount of data required to represent a group of transform coefficients. Quantization may be realized through division of transform coefficients by a quantization scaling factor and any associated rounding functions (e.g., rounding to the nearest integer). Quantized transform coefficients may be referred to as coefficient level values. Inverse quantization (or “dequantization”) may include multiplication of coefficient level values by the quantization scaling factor. It should be noted that as used herein the term quantization process in some instances may refer to division by a scaling factor to generate level values and multiplication by a scaling factor to recover transform coefficients in some instances.
  • a quantization process may refer to quantization in some cases and inverse quantization in some cases.
  • quantization processes are described with respect to arithmetic operations associated with decimal notation, such descriptions are for illustrative purposes and should not be construed as limiting.
  • the techniques described herein may be implemented in a device using binary operations and the like.
  • multiplication and division operations described herein may be implemented using bit shifting operations and the like.
  • FIGS. 4A-4B are conceptual diagrams illustrating examples of coding a block of video data.
  • a current block of video data e.g., a CB corresponding to a video component
  • the current block of video data is decoded 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 differ from the sample values of the current video block that is encoded. In this manner, coding may be said to be lossy. However, the difference in sample values may be considered acceptable to a viewer of the reconstructed video.
  • an array of scaling factors is generated by selecting a scaling matrix and multiplying each entry in the scaling matrix by a quantization scaling factor.
  • a scaling matrix is selected based on a prediction mode and a color component, where scaling matrices of the following sizes are defined: 4x4, 8x8, 16x16, and 32x32. It should be noted that in some examples, a scaling matrix may provide the same value for each entry (i.e., all coefficients are scaled according to a single value).
  • the value of a quantization scaling factor may be determined by a quantization parameter, QP.
  • 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%.
  • a QP value for a set of transform coefficients may be derived using a predictive quantization parameter value (which may be referred to as a predictive QP value or a QP predictive value) and an optionally signaled quantization parameter delta value (which may be referred to as a QP delta value or a delta QP value).
  • a quantization parameter may be updated for each CU and a quantization parameter may be derived for each of luma (Y) and chroma (Cb and Cr) components.
  • a predictive QP value is inherited for the CU (i.e., a QP signaled at the slice level or a QP from a previous CU) and a delta QP value may be optionally signaled for each TU within the CU.
  • the QP for each luma TB is the sum of the predictive QP value and any signaled delta QP value.
  • the chroma QP is a function of the QP determined for the luma component and chroma QP offsets signaled in a slice header and/or chroma QP offsets signaled a picture parameter set (PPS).
  • PPS picture parameter set
  • Quantized transform coefficients are coded into a bitstream.
  • Quantized transform coefficients and syntax elements may be entropy coded according to an entropy coding technique.
  • entropy coding techniques include content adaptive variable length coding (CAVLC), context adaptive binary arithmetic coding (CABAC), probability interval partitioning entropy coding (PIPE), and the like.
  • Entropy encoded quantized transform coefficients and corresponding entropy encoded syntax elements may form a compliant bitstream that can be used to reproduce video data at a video decoder.
  • An entropy coding process may include performing a binarization on syntax elements.
  • Binarization refers to the process of converting a value of a syntax value into a series of one or more bits. These bits may be referred to as “bins.” Binarization is a lossless process and may include one or a combination of the following coding techniques: fixed length coding, unary coding, truncated unary coding, truncated Rice coding, Golomb coding, k-th order exponential Golomb coding, and Golomb-Rice coding. For example, binarization may include representing the integer value of 5 for a syntax element as 00000101 using an 8-bit fixed length binarization technique or representing the integer value of 5 as 11110 using a unary coding binarization technique.
  • each of the terms fixed length coding, unary coding, truncated unary coding, truncated Rice coding, Golomb coding, k-th order exponential Golomb coding, and Golomb-Rice coding may refer to general implementations of these techniques and/or more specific implementations of these coding techniques.
  • a Golomb-Rice coding implementation may be specifically defined according to a video coding standard, for example, ITU-T H.265.
  • An entropy coding process further includes coding bin values using lossless data compression algorithms.
  • a context model may be selected from a set of available context models associated with the bin.
  • a context model may be selected based on a previous bin and/or values of previous syntax elements.
  • a context model may identify the probability of a bin having a particular value. For instance, a context model may indicate a 0.7 probability of coding a 0-valued bin and a 0.3 probability of coding a 1-valued bin. It should be noted that in some cases the probability of coding a 0-valued bin and probability of coding a 1-valued bin may not sum to 1.
  • a CABAC entropy encoder may arithmetically code a bin based on the identified context model. The context model may be updated based on the value of a coded bin.
  • the context model may be updated based on an associated variable stored with the context, e.g., adaptation window size, number of bins coded using the context.
  • an associated variable stored with the context e.g., adaptation window size, number of bins coded using the context.
  • a CABAC entropy encoder may be implemented, such that some syntax elements may be entropy encoded using arithmetic encoding without the usage of an explicitly assigned context model, such coding may be referred to as bypass coding.
  • the sample values of a reconstructed block may differ from the sample values of the current video block that is encoded.
  • coding video data on a block-by-block basis may result in artifacts, e.g., so-called blocking artifacts.
  • blocking artifacts may cause coding block boundaries of reconstructed video data to be visually perceptible to a user.
  • reconstructed sample values may be modified to minimize the difference between the sample values of the current video block that is encoded and/or minimize artifacts (e.g., blocking artifacts) introduced by the video coding process.
  • Such modifications may general be referred to as filtering.
  • filtering may occur as part of an in-loop filtering process or a post-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 video encoder and subsequent decoding at a video decoder).
  • 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, referring to FIG.
  • the sample values resulting from filtering the reconstructed block would be used for subsequent decoding (e.g., stored to a reference buffer) and would be output (e.g., to a display).
  • the reconstructed block 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 or applying a deblocking filter refers to the process of smoothing the boundaries of 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.
  • video blocks P and Q are used to refer to adjacent video blocks having a block boundary.
  • the manner in which sample values are modified may be based on defined filters, where pi and qi represent respective sample values in a column for a vertical boundary and sample values in a row for a horizontal boundary and pi’ and qi’ represent modified sample values.
  • 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.
  • Simplified definitions of equations for the Strong Filter and Weak Filter in ITU-T H.265 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, however, reference is made to ITU-T H.265, which provides the complete definitions.
  • ITU-T H.265 includes one type of filter that may be used for modifying chroma samples: Normal Filter. Simplified definitions of equations for the Normal Filter in ITU-T H.265 for modifying chroma sample values are provided below.
  • ITU-T H.265 provides where Sample Adaptive Offset (SAO) filtering may be applied in the in-loop filtering process.
  • SAO is a process that modifies the deblocked sample values in a region by conditionally adding an offset value.
  • ITU-T H.265 provides two types of SAO filters that may be applied to a CTB: band offset or edge offset. For each of band offset and edge offset, four offset values are included in a bitstream. For band offset, the offset which is applied depends on the amplitude of a sample value (e.g., amplitudes are mapped to bands which are mapped to the four signaled offsets). For edge offset, the offset which is applied depends on a CTB having one of a horizontal, vertical, first diagonal, or second diagonal edge classification (e.g., classifications are mapped to the four signaled offsets).
  • ALF adaptive loop filter
  • a bilateral filter filters an area of an image by replacing each sample value in the area with a weighted average of sample values from nearby samples, where the weight is based on the spatial closeness of sample values and difference (i.e., amplitude or intensity difference) of sample values.
  • difference i.e., amplitude or intensity difference
  • a sample located at (i, j) will be filtered using its neighboring sample located at (k, l).
  • the weight ⁇ (i, j, k, l) is the weight assigned for sample (k, l) to filter the sample (i, j), and it may be defined as provided in Equation 2a or Equation 2b as:
  • I(i, j) and I(k, l) may be the original reconstructed intensity value of samples (i, j) and (k,l) respectively.
  • ⁇ d is the spatial parameter
  • ⁇ ⁇ is the range parameter.
  • the properties of a bilateral filter based on Equation 2a and 2b are controlled by the spatial and the range parameters. As illustrated in Equation 2a and 2b, samples located closer to the sample to be filtered and samples having smaller intensity difference to the sample to be filtered, will have a larger weight than samples further away and with larger intensity difference.
  • Equation 3 min(x,y), returns x, if x less than or equal to y, else returns y. It should be noted in Equation 4, max(x,y), returns x, if x greater than or equal to y, else returns y. That is, the filter has a plus sign shaped filter aperture centered at the sample to be filtered.
  • FIG. 5 is a conceptual diagram illustrating an example bilateral filtering of video data in accordance with one or more techniques of this disclosure.
  • the filtered value, C F of a current sample to be filtered, C, is illustrated as the weighted sum of the left (L), above (A), below (B), and right (R) neighboring samples, wherein w L , w A , w B , and w R are the respective weights calculated based on the values and distance of L, A, B, and R, for example, as provided in Equation 2 above.
  • FIG. 6 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 perform video coding using one or more of the techniques described herein.
  • system 100 includes source device 102, communications medium 110, and destination device 120.
  • 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 set top boxes, digital video recorders, televisions, desktop, laptop, or tablet computers, gaming consoles, mobile devices, including, for example, “smart” phones, cellular telephones, personal gaming devices, and medical imagining 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.
  • 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.
  • DVD Digital Video Broadcasting
  • ATSC Advanced Television Systems Committee
  • ISDB Integrated Services Digital Broadcasting
  • DOCSIS Data Over Cable Service Interface Specification
  • GSM Global System Mobile Communications
  • CDMA code division multiple access
  • 3GPP 3rd Generation Partnership Project
  • ETSI European Telecommunications Standards Institute
  • IP Internet Protocol
  • WAP Wireless Application Protocol
  • IEEE Institute of Electrical and Electronics Engineers
  • 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.
  • 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
  • source device 102 includes video source 104, video encoder 106, and interface 108.
  • Video source 104 may include any device configured to capture and/or store video data.
  • 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.
  • video encoder 106 may compress video data. Compression may be lossy (discernible or indiscernible) or lossless.
  • Interface 108 may include any device configured to receive a compliant video bitstream and transmit and/or store the compliant video bitstream 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.
  • interface 108 may include a computer system interface that may enable a compliant video bitstream to be stored on a storage device.
  • 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, I 2 C, or any other logical and physical structure that may be used to interconnect peer devices.
  • PCI Peripheral Component Interconnect
  • PCIe Peripheral Component Interconnect Express
  • USB Universal Serial Bus
  • destination device 120 includes interface 122, video decoder 124, and display 126.
  • Interface 122 may include any device configured to receive a compliant video bitstream from 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 receive and/or send information.
  • interface 122 may include a computer system interface enabling a compliant video bitstream to be retrieved from a storage device.
  • interface 122 may include a chipset supporting PCI and PCIe bus protocols, proprietary bus protocols, USB protocols, I 2 C, or any other logical and physical structure that may be used to interconnect peer devices.
  • Video decoder 124 may include any device configured to receive a compliant 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. 6, 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. 7 is a block diagram illustrating an example of video encoder 200 that may implement the techniques for encoding video data described herein. It should be noted that although example video encoder 200 is illustrated as having distinct functional blocks, such an illustration is for descriptive purposes and does not limit video encoder 200 and/or sub-components thereof to a particular hardware or software architecture. Functions of video encoder 200 may be realized using any combination of hardware, firmware, and/or software implementations. In one example, video encoder 200 may be configured to encode video data according to the techniques described herein. Video encoder 200 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.
  • video encoder 200 receives source video blocks and outputs a bitstream.
  • source video blocks may include areas of picture that has been divided according to a coding structure.
  • source video data may include macroblocks, CTUs, CBs, sub-divisions thereof, and/or another equivalent coding unit.
  • video encoder 200 may be configured to perform additional sub-divisions of source video blocks. It should be noted that some techniques described herein may be generally applicable to video coding, regardless of how source video data is partitioned prior to and/or during encoding.
  • video encoder 200 includes summer 202, transform coefficient generator 204, coefficient quantization unit 206, inverse quantization/transform processing unit 208, summer 210, intra prediction processing unit 212, inter prediction processing unit 214, filter unit 216, and entropy encoding unit 218.
  • Video encoder 200 may generate residual data by subtracting a predictive video block from a source video block.
  • Summer 202 represents a component configured to perform this subtraction operation.
  • Transform coefficient generator 204 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 8 x 8 transforms may be applied to a 16 x 16 array of residual values) to produce a set of transform coefficients.
  • Transform coefficient generator 204 may be configured to perform any and all combinations of the transforms included in the family of discrete trigonometric transforms. As described above, in ITU-T H.265, TBs are restricted to the following sizes 4x4, 8x8, 16x16, and 32x32.
  • transform coefficient generator 204 may be configured to perform transformations according to arrays having sizes of 4x4, 8x8, 16x16, and 32x32. In one example, transform coefficient generator 204 may be further configured to perform transformations according to arrays having other dimensions. Transform coefficient generator 204 may output transform coefficients to coefficient quantization unit 206.
  • Coefficient quantization unit 206 may be configured to perform quantization of the transform coefficients.
  • Coefficient quantization unit 206 may be configured to determine quantization parameters and output QP data (e.g., data used to determine a quantization group size and/or delta QP values) that may be used by a video decoder to reconstruct a quantization parameter to perform inverse quantization during video decoding.
  • QP data e.g., data used to determine a quantization group size and/or delta QP values
  • the degree of quantization may be modulated on a CU-by-CU basis by adjusting a quantization parameter using a delta QP value.
  • quantized transform coefficients are output to inverse quantization/transform processing unit 208.
  • Inverse quantization/transform processing unit 208 may be configured to apply an inverse quantization and an inverse transformation to generate reconstructed residual data.
  • reconstructed residual data may be added to a predictive video block.
  • Video encoder 200 may be configured to perform multiple coding passes (e.g., perform encoding while varying one or more of a prediction, transformation parameters, and quantization parameters). The rate-distortion of a bitstream or other system parameters may be optimized based on the evaluation of reconstructed video blocks. Further, reconstructed video blocks may be stored and used as reference for predicting subsequent blocks.
  • a video block may be coded using an intra prediction.
  • Intra prediction processing unit 212 may be configured to select an intra prediction mode for a video block to be coded.
  • Intra prediction processing unit 212 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.
  • intra prediction processing unit 212 outputs intra prediction data (e.g., syntax elements) to entropy encoding unit 218 and transform coefficient generator 204.
  • intra prediction data e.g., syntax elements
  • a transform performed on residual data may be mode dependent.
  • possible intra prediction modes may include planar prediction modes, DC prediction modes, and angular prediction modes.
  • a prediction for a chroma component may be inferred from an intra prediction for a luma prediction mode.
  • Inter prediction processing unit 214 may be configured to perform inter prediction coding for a current video block.
  • Inter prediction processing unit 214 may be configured to receive source video blocks and calculate a motion vector for PUs of a video block.
  • a motion vector may indicate the displacement of a PU (or similar coding structure) 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 214 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.
  • SAD sum of absolute difference
  • SSD sum of square difference
  • Inter prediction processing unit 214 may be configured to perform motion vector prediction, as described above.
  • Inter prediction processing unit 214 may be configured to generate a predictive block using the motion prediction data. For example, inter prediction processing unit 214 may locate a predictive video block within a frame buffer (not shown in FIG. 7). It should be noted that inter prediction processing unit 214 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 214 may output motion prediction data for a calculated motion vector to entropy encoding unit 218.
  • inter prediction processing unit 214 may receive reconstructed video block via filter unit 216.
  • Filter unit 216 may be configured to perform deblocking, SAO filtering, ALF, and/or bilateral filtering according to one or more of techniques describe herein. Examples of deblocking, SAO filtering, ALF, and/or bilateral filtering are described above. Further, examples of deblocking, SAO filtering, ALF, and/or bilateral filtering are described further below with respect to FIGS. 9-10C.
  • video encoder 200 represents an example of a device configured to receive an array of sample values for a component of video data, determine whether to apply a bilateral filter to the array of sample values based on one or more bilateral filter control parameters, and output an array of modified samples values, wherein the array of samples are modified based according to an applied bilateral filter according to one or more of the techniques described herein.
  • entropy encoding unit 218 receives quantized transform coefficients and predictive syntax data (i.e., intra prediction data, motion prediction data, QP data, etc.). It should be noted that in some examples, coefficient quantization unit 206 may perform a scan of a matrix including quantized transform coefficients before the coefficients are output to entropy encoding unit 218. In other examples, entropy encoding unit 218 may perform a scan. Entropy encoding unit 218 may be configured to perform entropy encoding according to one or more of the techniques described herein. Entropy encoding unit 218 may be configured to output a compliant bitstream, i.e., a bitstream that a video decoder can receive and reproduce video data therefrom.
  • a compliant bitstream i.e., a bitstream that a video decoder can receive and reproduce video data therefrom.
  • 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.
  • video decoder 300 may be configured to reconstruct video data based on one or more of the techniques described above. That is, video decoder 300 may operate in a reciprocal manner to video encoder 200 described above.
  • Video decoder 300 may be configured to perform intra prediction decoding and inter prediction decoding and, as such, may be referred to as a hybrid decoder.
  • video decoder 300 includes an entropy decoding unit 302, inverse quantization unit 304, inverse transformation processing unit 306, intra prediction processing unit 308, inter prediction processing unit 310, summer 312, filter unit 314, and reference buffer 316.
  • Video decoder 300 may be configured to decode video data in a manner consistent with a video encoding system, which may implement one or more aspects of a video coding standard. It should be noted that although example video decoder 300 is illustrated as having distinct functional blocks, such an illustration is for descriptive purposes and does not limit video decoder 300 and/or sub-components thereof to a particular hardware or software architecture. Functions of video decoder 300 may be realized using any combination of hardware, firmware, and/or software implementations.
  • entropy decoding unit 302 receives an entropy encoded bitstream.
  • Entropy decoding unit 302 may be configured to decode quantized syntax elements and quantized coefficients from the bitstream according to a process reciprocal to an entropy encoding process.
  • Entropy decoding unit 302 may be configured to perform entropy decoding according any of the entropy coding techniques described above.
  • Entropy decoding unit 302 may parse an encoded bitstream in a manner consistent with a video coding standard.
  • Video decoder 300 may be configured to parse an encoded bitstream where the encoded bitstream is generated based on the techniques described above.
  • inverse quantization unit 304 receives quantized transform coefficients (i.e., level values) and quantization parameter data from entropy decoding unit 302.
  • Quantization parameter data may include any and all combinations of delta QP values and/or quantization group size values and the like described above.
  • Video decoder 300 and/or inverse quantization unit 304 may be configured to determine QP values used for inverse quantization based on values signaled by a video encoder and/or through video properties and/or coding parameters. That is, inverse quantization unit 304 may operate in a reciprocal manner to coefficient quantization unit 206 described above.
  • Inverse quantization unit 304 may be configured to apply an inverse quantization.
  • Inverse transform processing unit 306 may be configured to perform an inverse transformation to generate reconstructed residual data.
  • the techniques respectively performed by inverse quantization unit 304 and inverse transform processing unit 306 may be similar to techniques performed by inverse quantization/transform processing unit 208 described above.
  • Inverse transform processing unit 306 may be configured to apply an inverse DCT, an inverse DST, an inverse integer transform, Non-Separable Secondary Transform (NSST), or a conceptually similar inverse transform processes to the transform coefficients in order to produce residual blocks in the pixel domain. Further, as described above, whether a particular transform (or type of particular transform) is performed may be dependent on an intra prediction mode. As illustrated in FIG. 8, reconstructed residual data may be provided to summer 312. Summer 312 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 308 may be configured to receive intra prediction syntax elements and retrieve a predictive video block from reference buffer 316.
  • Reference buffer 316 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.
  • intra prediction processing unit 308 may reconstruct a video block using according to one or more of the intra prediction coding techniques described herein.
  • Inter prediction processing unit 310 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 316.
  • Inter prediction processing unit 310 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 310 may use interpolation filters to calculate interpolated values for sub-integer pixels of a reference block.
  • Filter unit 314 may be configured to perform filtering on reconstructed video data.
  • filter unit 314 may be configured to perform deblocking, SAO filtering, ALF filtering, and/or bilateral filter, according to one or more of the techniques described herein.
  • FIG. 9 is a block diagram illustrating an example of a filter unit that may be configured to modify reconstructed video data according to one or more techniques of this disclosure.
  • filter unit 400 includes filter determination 402 and sample modification unit 404.
  • Filter determination unit 402 may be configured to determine whether one or more defined filters is applied to a reconstructed video block.
  • filter determination unit 402 may determine which of deblocking, SAO filtering, ALF filtering, and/or bilateral filtering should be applied to a reconstructed video block. As illustrated, in FIG. 9, filter determination unit 402 receives coding parameters (e.g., QP values, prediction modes, etc.) and a reconstructed video block, as such, filter determination unit 402 may determine whether one or more defined filters is applied to a reconstructed video block based on one or more coding parameters and/or sample values of reconstructed video blocks.
  • Sample modification unit 404 may be configured to receive reconstructed video blocks and output modified reconstructed video block based on one or more filters that are defined. Further, as illustrated in FIG. 9, modified reconstructed video blocks may be sent to an output (e.g., post-loop) and/or a reference picture buffer (e.g., in-loop).
  • an output e.g., post-loop
  • a reference picture buffer e.g., in-loop
  • FIGS. 10A-10C are block diagrams illustrating examples of a sample modification units that may be configured to filter video data according to one or more techniques of this disclosure.
  • sample modification unit 500 includes a bilateral filter unit 502 and additional filter(s) unit 504.
  • Bilateral filter unit 502 may be configured to perform bilateral filtering according to one or more of the techniques described herein.
  • bilateral filtering unit 502 may be configured to approximate the calculation of weight values by integer operations (e.g. bitshifts, integer multiplication, integer division, integer modulo, clip to integer bounds).
  • bilateral filtering unit 502 may determine weight values using one or more lookup tables.
  • a lookup value may be based on intensity distance and/or spatial distance.
  • Additional filter(s) unit 504 may be configured to perform deblocking, SAO filtering, and/or ALF filtering according to one or more of the techniques described herein.
  • bilateral filtering may be performed in-loop or post-loop and may be applied prior to or subsequent to one or more of deblocking, SAO filtering, and/or ALF.
  • samples (k, l) may include samples for a specified range of k and l (e.g., -2 to 2).
  • bilateral filter unit 502 may perform bilateral filtering according to other filter aperture shapes (e.g., a 5x5 diamond, etc.).
  • a neighboring sample value e.g., L, A, B, R
  • a neighboring sample value may be included in neighboring video block. In some cases, the neighboring video block and thus, a neighboring sample value may not be available.
  • a block of samples considered for bilateral filtering may include a CU, a PU, a TU, a CTU, a picture, a set of samples within a slice, a tile, a wave front, and/or a dependent slice.
  • availability may refer to a sample outside these areas and that is not available.
  • Bilateral filter unit 502 may be configured to account for unavailable sample values.
  • unavailable sample values may be set to a default value.
  • default values may be fixed integer values.
  • default values may be based on available spatially neighboring sample values. For example, the value of a nearest spatial neighbor may be copied.
  • a symmetric extension of a block being considered may be used.
  • a symmetric extension may include mirroring values of a block being considered about a boundary. For example, referring to the notation in the deblocking equations provided above, an unavailable qi may be set to pi.
  • filter determination unit 402 may determine whether one or more defined filters is applied to a reconstructed video block based on one or more coding parameters and/or sample values of reconstructed video blocks.
  • filter determination unit 402 may be configured to enable and/or apply or not apply bilateral filtering.
  • filter determination unit 402 may selectively apply a bilateral filter based on an indicator received in the bitstream. For example, an indicator may be signaled at CU-level, PU-level, TU-level, CTU-level, slice-level, Tile-level, Wavefront-level, in a Picture Parameter Set (PPS), in Sequence Parameter Set (SPS) or along with any other collection of control parameters. In one example, the indicator may be a flag.
  • filter determination unit 402 may selectively enable and/or apply a bilateral filter based on one or more video coding parameters. That is, a filter determination unit 402 may selectively enable and/or apply a bilateral filter to a reconstructed video block based on how the reconstructed video block was generated.
  • filter determination unit 402 may be configured such that: (1) bilateral filtering is not applied to reconstructed blocks where dequantization/scaling was skipped (i.e., because such blocks may be coded losslessly); (2) bilateral filtering may or may not be applied based on a prediction mode used to generate a reconstructed video block; (3) bilateral filtering may be applied based on the use of position dependent intra prediction combination (PDPC) techniques to generate a reconstructed video block; (4) bilateral filtering may be applied based on use of Rotated Orthogonal Transform (ROT) techniques to generate a reconstructed video blocks; (5) bilateral filtering may be applied based on the use of overlapped block motion compensation (OBMC) techniques to generate a reconstructed video block; (6) bilateral filtering may be applied based on the use of affine motion compensation to generate a reconstructed video block; (7) bilateral filtering may be applied based on the use of frame rate up conversion (FRUC) techniques to generate a reconstructed video block; (8) bilateral filtering may be applied based based
  • bilateral filter unit 502 may be configured to calculate the spatial parameter, ⁇ d , and/or the range parameter, ⁇ r , according to any and all combinations of one or more bilateral filter control parameters.
  • ⁇ d and/or ⁇ r may be a linear function of one or more bilateral filter control parameters
  • ⁇ d and/or ⁇ r may be a non-linear function of one or more bilateral filter control parameters
  • ⁇ d and/or ⁇ r may be an affine function of one or more bilateral filter control parameters.
  • ⁇ d and/or ⁇ r may be upper bounded and/or lower bounded. In an example the bounds may be pre-determined.
  • the bounds may be derived based on one or more bilateral filter control parameters.
  • fixed offset addition may be used to determine ⁇ d and/or ⁇ r .
  • ⁇ d and/or ⁇ r may be determined according to any and all combinations of the functions described above.
  • bilateral filter unit 502 may be configured such that the support (as described above) of a bilateral filter is based on one or more of bilateral filter control parameters.
  • bilateral filter unit 502 may be configured such that intensity distance is calculated based on a set of sample values from each component. That is, for example, a luma sample (or chroma sample) may be filtered based on both nearby luma and chroma samples.
  • a spatial location (m,n) for a component corresponding set S of spatial location(s) may be determined in a subset (or all) of the components. Subset S may depend on chroma format of sequence.
  • the sample value locations corresponding to S may be determined using linear/affine transformation of the location of the sample being determined.
  • sample value of luma at location (m, n) three sample values are used when determining intensity distance: sample value of luma at location (m, n), sample value of first chroma component at location (m/2, n/2), and sample value of second chroma component at location (m/2, n/2).
  • filter unit 400 may be configured such that when a bilateral filter is enabled and/or applied, parameter and use of a deblocking filter, SAO, and/or ALF, may be adjusted. In one example, if a bilateral filter is enabled and/or applied, the deblocking filter strength may be reduced. In one example, if a bilateral filter is enabled and/or applied, the SAO edge offset may be related to whether the bilateral filter is used or not. In one example, if a bilateral filter is enabled and/or applied, the SAO edge offset may be related to whether bilateral filter is used or not.
  • filter determination unit 402 may be configured to selectively enable and/or apply bilateral filters using one or more sets of bilateral filters.
  • Respective bilateral filters in a set may be distinguished according to characteristics of bilateral filters described herein.
  • bilateral filters may be distinguished based on one or more of weight definitions, spatial parameter, ⁇ d , definitions, range parameter, ⁇ r , definitions, and/or aperture shapes/sizes.
  • selection of a bilateral filter from a defined set of bilateral filters may be signaled directly in bitstream (e.g., using an index value).
  • selection of a bilateral filter from a defined set of bilateral filters may be determined implicitly based on coding parameters, e.g., inferred based on information included in a bitstream (e.g., block-size, QP values, etc.).
  • selection of a bilateral filter from a defined set of bilateral filters, including whether bilateral filtering is disabled or not applied may be indicated using both direct and implicit indications. For example, an indication that bilateral filtering is enabled may be indicated directly in a bitstream (e.g., using a flag) and the selection of a bilateral filter from a defined set of bilateral filters may be determined implicitly based on coding parameters.
  • the selection of a bilateral filter from a defined set of bilateral filters may be signaled directly in a bitstream (e.g., using an index value) and an indication whether the selected bilateral filter is enabled or applied may be based on coding parameters and/or one or more of the bilateral filter control parameters described above.
  • Selection of bilateral filters from a set of defined bilateral filters may occur at one or more levels of video, e.g., a CU-level, a PU-level, a TU-level, a CTU-level, a slice-level, a Tile-level, a Wavefront-level, Picture-level, a Sequence-level.
  • the selection of a bilateral filter from a defined set of bilateral filters may be indicated in a bitstream based on the selection of bilateral filters from a set for spatially/temporally neighboring blocks, including whether bilateral filtering is disabled or not applied for a neighboring block.
  • bilateral filters used for a set of spatially/temporally neighboring blocks may be used to create a candidate list and an index corresponding to a bilateral filter included in the list may be signaled.
  • a delta value from the identified entry in the list may be signaled, e.g., if the created list is incomplete or fixed length.
  • the selection of a bilateral filter from a defined set of bilateral filters may be inferred or indicated in a bitstream based on an intra prediction mode of a block.
  • any of the bilateral filters described herein including bilateral filters included in a set of bilateral filters spatial parameter, ⁇ d , definitions, and/or range parameter, ⁇ r , definitions may be based on coding parameters.
  • the range parameter, ⁇ r , and/or the spatial parameter, ⁇ d may be based on a QP value.
  • ⁇ r may be defined as: Where TH 0 is a threshold value In one example, TH 0 may be equal to 17
  • ⁇ r may be defined as: whereTH 0 is a threshold value In one example, TH 0 may be equal to 17
  • ⁇ ⁇ is a function of QP 2 and QP.
  • ⁇ d may be defined as: In one example, TH 0 may be equal to 17
  • ⁇ d is proportional to QP.
  • ⁇ d may be determined using a Look-up Table (LUT), which uses QP values and/or block dimensions (e.g., height and/or width) as indices.
  • LUT Look-up Table
  • the size and/or shape of a bilateral filter may depend on the value of ⁇ d . Further, in one example, the size and/or shape of a bilateral filter may depend on the value of QP. In one example, the larger sized square filters may correspond to relatively larger QP values and smaller sized square filters may correspond to relatively smaller QP values.
  • syntax elements may be entropy coded and entropy coding may include binarization and for a particular bin, selection of a context model from a set of available context models associated with the bin.
  • entropy coding of syntax element(s) indicating a bilateral filter from a defined set of bilateral filters may be based on the selection of bilateral filters from a set for spatially/temporally neighboring blocks.
  • the binarization of the syntax element(s) may be based on the bilateral filter selected for blocks included in a set of spatially/temporally neighboring blocks.
  • the context model of the syntax element(s) may be based on the bilateral filter selected for blocks included in a set of spatially/temporally neighboring blocks. Further, in one example, the context model of the syntax element(s) may be based on an intra prediction mode of a block. In one example, the context model of the syntax element(s) may be based on a position of the bin being coded. In one example, binarization and/or context model selection of the syntax elements may be based on one or more of the bilateral filter control parameter described above. As described above, entropy decoding may be performed according to reciprocal entropy coding processes.
  • a reconstructed video block may be output by video decoder 300.
  • video decoder 300 represents an example of a device configured to receive an array of sample values for a component of video data, determine whether to apply a bilateral filter to the array of sample values based on one or more bilateral filter control parameters, and output an array of modified samples values, wherein the array of samples are modified based according to an applied bilateral filter according to one or more of the techniques described herein.
  • 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.
  • 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.
  • 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.
  • any connection is properly termed a computer-readable medium.
  • 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.
  • DSL digital subscriber line
  • Disk and disc 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.
  • 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.
  • DSPs digital signal processors
  • ASICs application specific integrated circuits
  • FPGAs field programmable logic arrays
  • processors may refer to any of the foregoing structure or any other structure suitable for implementation of the techniques described herein.
  • 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).
  • IC integrated circuit
  • 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.
  • 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.

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  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Compression Or Coding Systems Of Tv Signals (AREA)

Abstract

L'invention concerne un dispositif de codage vidéo qui peut être configuré pour effectuer un codage vidéo selon une ou plusieurs des techniques décrites ici. Un procédé de codage vidéo consiste à : recevoir un réseau de valeurs d'échantillon pour un composant de données vidéo; déterminer s'il faut appliquer un filtre bilatéral au réseau de valeurs d'échantillon sur la base d'un ou plusieurs paramètres de commande de filtre bilatéral; et délivrer en sortie un réseau de valeurs d'échantillons modifiés, le réseau d'échantillons étant modifié selon un filtre bilatéral appliqué.
PCT/JP2018/011293 2017-03-29 2018-03-22 Systèmes et procédés de filtrage de données vidéo reconstruites à l'aide de techniques de filtrage bilatéral WO2018180841A1 (fr)

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WO2020228661A1 (fr) * 2019-05-11 2020-11-19 Beijing Bytedance Network Technology Co., Ltd. Filtre de déblocage destiné à un codage vidéo
CN114731398A (zh) * 2019-11-15 2022-07-08 高通股份有限公司 视频译码中的跨分量自适应环路滤波器
WO2021211370A1 (fr) * 2020-04-13 2021-10-21 Tencent America LLC Procédé et appareil de vidéocodage
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WO2022268184A1 (fr) * 2021-06-25 2022-12-29 Beijing Bytedance Network Technology Co., Ltd. Filtre bilatéral adaptatif en codage vidéo

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