WO2020073969A1

WO2020073969A1 - An image processing device and method for performing deblocking

Info

Publication number: WO2020073969A1
Application number: PCT/CN2019/110446
Authority: WO
Inventors: Haitao Yang; Jianle Chen; Huanbang CHEN
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2018-10-10
Filing date: 2019-10-10
Publication date: 2020-04-16
Anticipated expiration: 2021-04-10

Abstract

Methods and apparatuses for deblocking sub-block edges between sub-blocks are provided. A deblocking filter includes an edge locating unit for determining sub-block edges between sub-blocks of a current block which is predicted using a sub-block inter prediction mode, the sub-block edges comprising a sub-block edge between a first sub-block and a second sub-block, a deblocking determination unit for determining whether the current block has residual data and whether a reference block of the first sub-block and a reference block of the second sub-block are continuous, and a deblocking filtering unit for applying a deblocking filter to values of samples in a vicinity of the sub-block edge between the first sub-block and the second sub-block, when the current block has no residual data and the reference block of the first sub-block and the reference block of the second sub-block are discontinuous.

Description

AN IMAGE PROCESSING DEVICE AND METHOD FOR PERFORMING DEBLOCKING

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No. 62/744,114, filed on October 10, 2018, the disclosure of which is hereby incorporated by reference in its entirety for all purposes.

TECHNICAL FIELD

Embodiments of the present invention relate to the field of picture processing, for example, still picture and/or video picture coding. In particularly, the invention relates to improvements of the deblocking filter.

BACKGROUND

Image coding (encoding and decoding) is used in a wide range of digital image applications, for example broadcast digital TV, video transmission over internet and mobile networks, real-time conversational applications such as video chat, video conferencing, DVD and Blu-ray discs, video content acquisition and editing systems, and camcorders of security applications.

Since the development of the block-based hybrid video coding approach in the H. 261 standard in 1990, new video coding techniques and tools were developed and formed the basis for new video coding standards. One of the goals of most of the video coding standards is to achieve a bit rate reduction compared to its predecessor without sacrificing picture quality. Further video coding standards comprise MPEG-1 video, MPEG-2 video, ITU-T H. 262/MPEG-2, ITU-T H. 263, ITU-T H. 264/MPEG-4, Part 10, Advanced Video Coding (AVC) , ITU-T H. 265, High Efficiency Video Coding (HEVC) , ITU-T H. 266/Versatile video coding (VVC) and extensions, e.g. scalability and/or three-dimensional (3D) extensions, of these standards. Block-based image coding schemes have in common that along the block edges, edge artifacts can appear. These artifacts are due to the independent coding of the coding blocks. These edge artifacts are often readily visible to a user. A goal in block-based image coding is to reduce edge artifacts below a visibility threshold. This is done by performing deblocking filtering. Such a deblocking filtering is on the one hand performed at the decoder side in order to remove the visible edge artifacts, but also at the encoder side, in order to prevent the edge artifacts from being encoded into the image at all. Especially for small code block sizes, the deblocking filtering can be challenging.

BRIEF SUMMARY OF THE INVENTION

In view of the above-mentioned challenges, the present invention aims to improve the conventional deblocking filtering. The present invention has the objective to provide an image processing device that can perform deblocking filtering in an efficient manner.

Numerous benefits and technical advantages are achieved by way of the present invention over conventional techniques. For example, embodiments of the present invention utilize sub-block motion prediction mode to predict sub-block edges between sub-blocks of a current block and determine whether the current block has residual data or not and determine whether a reference block of a first sub-block and a reference block of a second sub-block or continuous. Based on the results of the determination, a deblocking filter is then applied to values of samples in the vicinity of the sub-block edges. This approach allows for an accurate and efficient deblocking.

Embodiments of the invention are defined by the features of the independent claims, and further advantageous implementations of the embodiments are provided by the features of the dependent claims.

According to a first aspect of the invention, a deblocking filter apparatus is provided. The deblocking filter apparatus is utilized in an image encoder and/or an image decoder. The technical advantages of the deblocking filter apparatus are its applicability a large variety of devices, such as wireless handsets, video encoders, video decoders, computer animated pictures, etc. The deblocking filter apparatus includes an edge locating unit configured to determine sub-block edges (sub-block boundaries) between sub-blocks of a current block, which is predicted using a sub-block based inter prediction mode (namely, a sub-block inter prediction mode or sub-block motion prediction mode) . The sub-block edges include a sub-block edge between a first sub-block P and a second sub-block Q.

The deblocking filter apparatus also includes a deblocking determination unit configured to determine whether the current block has residual data or not, and/or whether a reference block of the first sub-block and a reference block of the second sub-block are continuous, and a deblocking filtering unit configured to apply the deblocking filter to values of samples near the sub-block edge (e.g. values of samples in a vicinity of the sub-block edge) between the first sub-block P and the second sub-block Q, when the current block has no residual data and the reference block of the first sub-block and the reference block of the second sub-block are discontinuous.

It allows the use of sub-block motion prediction mode to predict sub-block edges between sub-blocks of a current block and determine whether the current block has residual data or not and/or determine whether a reference block of a first sub-block and a reference block of a second sub-block or continuous. Based on the results of the determination, a deblocking filter is then applied to values of samples in the vicinity of the sub-block edges. This approach allows for an accurate and efficient deblocking.

In a possible implementation form of the method according to the first aspect as such, , the deblocking determination unit is configured to determine that, when a value of a first flag (such as a coded_block_flag) parsed from a bitstream is equal to a first value (such as 0) , the current block has no residual data; or when the value of the first flag (such as a coded_block_flag) parsed from the bitstream is equal to a second value (such as 1) different from the first value, the current block has residual data.

In a possible implementation form of the method according to any preceding implementation of the first aspect or the first aspect as such, the deblocking determination unit is configured to determine that, when a reference index of the first sub-block and a reference index of the second sub-block are different, a reference block of the first sub-block and a reference block of the second sub-block are discontinuous; or

when the reference index of the first sub-block and the reference index of the second sub-block are the same, and a motion vector difference between a motion vector of the first sub-block and a motion vector of the second sub-block is larger than a threshold (such as predefined pixel or pixels) , a reference block of the first sub-block and a reference block of the second sub-block are discontinuous; or

when the motion vector difference between the motion vector of the first sub-block and the motion vector of the second sub-block is larger than the threshold, the reference block of the first sub-block and the reference block of the second sub-block are discontinuous.

In a possible implementation form of the method according to any preceding implementation of the first aspect or the first aspect as such, wherein each of the sub-blocks of the current block has its own motion information, the deblocking determination unit is configured to perform inter prediction based on the motion information of each of the sub-blocks to obtain a predictor (i.e. prediction block or predicted value) of each of the sub-blocks (orcorresponding to each of the sub-blocks) .

In a possible implementation form of the method according to any preceding implementation of the first aspect or the first aspect as such, wherein the sub-block inter prediction mode comprises one of the following modes: advanced temporal motion vector prediction (ATMVP) mode, spatial-temporal motion vector prediction (STMVP) mode, affine prediction mode, and planar motion vector prediction mode.

In a possible implementation form of the method according to any preceding implementation of the first aspect or the first aspect as such, wherein the first sub-block comprises motion information including a motion vector and a reference index (a pair of motion vectors and a pair of reference indices) of the first sub-block, and the reference block of the first sub-block is pointed by the motion vector in a reference picture corresponding to the reference index of the first sub-block; and

the second sub-block comprises motion information including a motion vector and a reference index (a pair of motion vectors and a pair of reference indices) of the second sub-block, and the reference block of the second sub-block is pointed by the motion vector in a reference picture corresponding to the reference index of the second sub-block.

In a possible implementation form of the method according to any preceding implementation of the first aspect or the first aspect as such, wherein the sub-block edges comprise horizontal sub-block boundaries on a 8*8 grid and/or vertical sub-block boundaries on a 8*8 grid; or the sub-block edges comprise horizontal sub-block boundaries on a 4*4 grid and/or vertical sub-block boundaries on a 4*4 grid.

In a possible implementation form of the method according to any preceding implementation of the first aspect or the first aspect as such, wherein each of the sub-blocks has a block size being M×M or N×N, M and N being an even integer equal to or larger than 4.

According to a second aspect, a deblocking filter apparatus is provided. The deblocking filter apparatus is utilized in an image encoder and/or an image decoder. The deblocking filter apparatus includes an edge locating unit configured to determine sub-block edges (sub-block boundaries) between sub-blocks of a current block which is predicted using sub-block based inter prediction mode (namely sub-block inter prediction mode, or sub-block motion prediction mode) . The sub-block edges includes a sub-block edge between a first sub-block and a second sub-block.

The deblocking filter apparatus also includes a deblocking determination unit configured to determine whether the sub-block edge is to be filtered by applying a deblocking filter according to a first determination result and/or a second determination result. The first determination result indicates whether the current block has residual data or not, and the second determination result indicates whether a reference block of the first sub-block and a reference block of the second sub-block are continuous.

The deblocking filter apparatus also includes a deblocking filtering unit configured to apply the deblocking filter to values of samples near the sub-block edge (such as the samples which are in a line perpendicular to and adjacent to the sub-block edge) between the first sub-block P and the second sub-block Q, when it is determined the sub-block edge is to be filtered by applying the deblocking filter according to the first determination result and/or the second determination result.

According to a third aspect of the invention, a video encoding apparatus for encoding a picture of a video stream is provided. The video encoding apparatus (100) comprises: a reconstruction unit (114) configured to reconstruct the picture; and a filter apparatus (120) as previously described for processing the reconstructed picture into a filtered reconstructed picture. This allows for a very efficient and accurate encoding of an image.

According to a fourth aspect of the invention, a video decoding apparatus (200) for decoding a picture of an encoded video stream (303) is provided. The video decoding apparatus (200) comprises: a reconstruction unit (214) configured to reconstruct the picture; and a loop filter apparatus (220) as previously described which is configured to process the reconstructed picture into a filtered reconstructed picture. This allows for an accurate and efficient decoding of an image.

A fifth aspect the invention relates to a deblocking method for use in an image encoding and/or an image decoding. The method includes determining sub-block edges (sub-block boundaries) between sub-blocks of a current block which is predicted using sub-block based inter prediction mode (namely, sub-block inter prediction mode or sub-block motion prediction mode) . The sub-block edges comprises a sub-block edge between a first sub-block P and a second sub-block Q. The method also includes determining whether the current block has residual data or not, and/or whether a reference block of the first sub-block and a reference block of the second sub-block are continuous; and applying the deblocking filter to values of samples near the sub-block edge between the first sub-block P and the second sub-block Q, when the current block has no residual data and the reference block of the first sub-block and the reference block of the second sub-block are discontinuous. This allows for an accurate and efficient deblocking.

In an example, the method includes determining sub-block edges between sub-blocks of a current block which is predicted using a sub-block inter prediction mode, the sub-block edges comprising a sub-block edge between a first sub-block and a second sub-block; determining whether the current block has residual data;

The method also includes when the current block does not residual data:

determining whether a reference block of the first sub-block and a reference block of the second sub-block are continuous;

when the reference block of the first sub-block and a reference block of the second sub-block are not continuous: applying a deblocking filter to values of samples near the sub-block edge between the first sub-block and the second sub-block; and

when the current block has residual data or when the reference block of the first sub-block and the reference block of the second sub-block are continuous:

terminating deblocking.

In a possible implementation form of the method according to any preceding implementation of the fifth aspect, the step of determining whether the current block has residual data or not includes:

determining that the current block has no residual data when a value of a first flag (such as a coded_block_flag) parsed from a bitstream is equal to a first value (such as 0) ; or

determining that the current block has residual data when the value of the first flag (such as a coded_block_flag) parsed from the bitstream is equal to a second value (such as 1) .

In a possible implementation form of the method according to any preceding implementation of the fifth aspect or the fifth aspect as such, wherein the step of determining whether a reference block of the first sub-block and a reference block of the second sub-block are continuous, comprising:

when a reference index of the first sub-block and a reference index of the second sub-block are different, a reference block of the first sub-block and a reference block of the second sub-block are discontinuous; or

when a reference index of the first sub-block and a reference index of the second sub-block are same and the motion vector difference between a motion vector of the first sub-block and a motion vector of the second sub-block is larger than a threshold (predefined pixel or pixels) , a reference block of the first sub-block and a reference block of the second sub-block are discontinuous; or

when the motion vector difference between a motion vector of the first sub-block and a motion vector of the second sub-block is larger than a threshold, a reference block of the first sub-block and a reference block of the second sub-block are discontinuous.

In an example, the determining whether the reference block of the first sub-block and the reference block of the second sub-block are continuous includes:

determining whether a reference index of the first sub-block and a reference index of the second sub-block are different:

when the reference index of the first sub-block and the reference index of the second sub-block are different, determining that the reference block of the first sub-block and the reference block of the second sub-block are discontinuous; or

when the reference index of the first sub-block and the reference index of the second sub-block are not different, and a motion vector difference between a motion vector of the first sub-block and a motion vector of the second sub-block is larger than a threshold, determining that the reference block of the first sub-block and the reference block of the second sub-block are discontinuous; or

when the motion vector difference between the motion vector of the first sub-block and the motion vector of the second sub-block is larger than the threshold, determining that the reference block of the first sub-block and the reference block of the second sub-block are discontinuous.

In a possible implementation form of the method according to any preceding implementation of the fifth aspect or the fifth aspect as such, , each of the sub-blocks of the current block has its own motion information, the method further comprising: performing inter prediction based on the motion information of each of the sub-blocks to obtain a predictor (e.g. prediction block or predicted value) of each of the sub-blocks (or associated with each of the sub-blocks) .

In a possible implementation form of the method according to any preceding implementation of the fifth aspect or the fifth aspect as such, wherein the sub-block inter prediction mode comprises one of the following modes:

advanced temporal motion vector prediction (ATMVP) mode;

spatial-temporal motion vector prediction (STMVP) mode;

affine prediction mode; and

planar motion vector prediction mode.

In a possible implementation form of the method according to any preceding implementation of the fifth aspect or the fifth aspect as such, wherein:

the first sub-block comprises motion information including a motion vector and a reference index of the first sub-block, and the reference block of the first sub-block is pointed by the motion vector in a reference picture corresponding to the reference index of the first sub-block; the second sub-block comprises motion information including a motion vector and a reference index of the second sub-block, and the reference block of the second sub-block is pointed by the motion vector in a reference picture corresponding to the reference index of the second sub-block.

In a possible implementation form of the method according to any preceding implementation of the fifth aspect or the fifth aspect as such, , wherein the sub-block edges comprise horizontal sub-block boundaries on a 8*8 grid and/or vertical sub-block boundaries on a 8*8 grid; or

the sub-block edges comprise horizontal sub-block boundaries on a 4*4 grid and/or vertical sub-block boundaries on a 4*4 grid.

In a possible implementation form of the method according to any preceding implementation of the fifth aspect or the fifth aspect as such, , wherein each of the sub-blocks has a block size being M×M or N×N, M and N being an even integer equal to or greater than 4.

A sixth aspect the invention relates to a deblocking method for use in an image encoding and/or an image decoding. The method includes determining sub-block edges (sub-block boundaries) between sub-blocks of a current block which is predicted using sub-block based inter prediction mode (sub-block motion prediction mode) . The sub-block edges includes a sub-block edge between a first sub-block P and a second sub-block Q. The method also includes determining whether the sub-block edge is to be filtered by applying a deblocking filter according to a first determination result and/or a second determination result; wherein the first determination result indicates whether the current block has residual data or not, and the second determination result indicates whether a reference block of the first sub-block P and a reference block of the second sub-block Q are continuous; and applying the deblocking filter to values of samples near the sub-block edge between the first sub-block P and the second sub-block Q, when it is determined the sub-block edge is to be filtered by applying the deblocking filter according to the first determination result and/or the second determination result.

This allows for an especially accurate and efficient deblocking.

A seventh aspect the invention relates to an encoding method for encoding an image (900, 1300) , which includes a previously disclosed deblocking method. This allows for a very efficient and accurate encoding of an image.

An eighth aspect the invention relates to a decoding method for decoding an image (900, 1300. The decoding method includes a previously shown deblocking method. This allows for a very efficient and accurate decoding of the image.

The method according to the fifth or sixth aspect of the invention can be performed by the apparatus according to the first aspect of the invention. Further features and implementation forms of the method according to the sixth or seventh aspect of the invention result directly from the functionality of the apparatus according to the first aspect of the invention and its different implementation forms.

The method according to the eighth aspect of the invention can be performed by the apparatus according to the second aspect of the invention. Further features and implementation forms of the method according to the eighth aspect of the invention result directly from the functionality of the apparatus according to the second aspect of the invention and its different implementation forms.

According to another aspect the invention relates to an apparatus for decoding a video stream includes a processor and a memory. The memory stores instructions that cause the processor to perform the previously described deblocking method.

Another aspect of the invention relates to an encoding apparatus for encoding a video stream. The encoding apparatus includes a processor and a memory. The memory is configured to store instructions that cause the processor to perform the previously described deblocking method.

Another aspect of the invention provides a computer-readable storage medium having stored thereon instructions that, when executed cause one or more processors to encode video data. The instructions cause the one or more processors to perform a previously described method.

Another aspect of the invention provides a computer program product including a program code for performing the previously described method when the computer program runs on a computer.

According to another aspect, an apparatus is provided, which comprises modules/units/components/circuits to perform at least a part of the steps of the above method according to any preceding implementation of the any preceding aspect or the any preceding aspects as such.

The apparatus according to the aspect can be extended into implementation forms corresponding to the implementation forms of a method according to the any preceding aspect. Hence, an implementation form of the apparatus comprises the feature (s) of the corresponding implementation form of the method according to the any preceding aspect.

The advantages of the apparatuses according to the any preceding aspect are the same as those for the corresponding implementation forms of the method according to the any preceding aspect.

Details of one or more embodiments are set forth in the accompanying drawings and the description below. To provide a thorough understanding of embodiments of the present invention, features, objects, and advantages of the present invention will be apparent from the detailed description, drawings, and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The following embodiments of the invention are described in detail with reference to the attached figures and drawings, in which:

FIG. 1 is a block diagram showing an example of a video encoder configured to implement embodiments of the invention;

FIG. 2 is a block diagram showing an example structure of a video decoder configured to implement embodiments of the invention;

FIG. 3 is a block diagram showing an example of a video coding system configured to implement embodiments of the invention;

FIG. 4 shows a 4-parameter affine model;

FIG. 5 shows motion vectors (affine MVF per sub-block) for a current block determined for each 4x4 sub-block based on the MVs of two control points;

FIG. 6 shows a 6-parameter affine model;

FIG. 7 shows a planar motion vector prediction process;

FIG. 8 shows ATMVP motion prediction for a CU;

FIG. 9 shows Example of one CU with four sub-blocks (A-D) and its neighbouring blocks (a–d) ;

FIG. 10 shows block artifacts may be created when adjacent sub-blocks are predicted from non-adjacent areas in the reference picture;

FIG. 11 shows a flow diagram depicting an exemplary deblocking method according to an embodiment;

FIG. 12A shows decisions for each four-sample segment of sub-block boundary;

FIG. 12B shows decisions for each four-sample segment of sub-block boundary;

FIG. 13 shows a block diagram depicting deblocking filter control information provided in the bitstream BTS output from the video encoder of FIG. 2 or provided to the video decoder of FIG. 3;

FIG. 14 shows Illustration of picture samples, horizontal and vertical sub-block boundaries on the 8*8 grid;

FIG. 15 shows a flow diagram depicting an exemplary deblocking method according to an embodiment;

FIG. 16 shows a flow diagram depicting a sub-block edge which divides the sub-blocks P and Q;

FIG. 17 shows an exemplary deblocking filter apparatus according to an embodiment of the present invention;

Fig. 18 shows an exemplary deblocking method according to an embodiment of the present invention;

Fig. 19 shows schematic diagram of an example coding device 1300 for video coding according to an embodiment of the present invention;

FIG. 20 shows schematic diagram of an example coding device 1400 for video coding according to an embodiment of the present invention;

FIG. 21 is a block diagram showing an example structure of a content supply system which provides a content delivery service.

FIG. 22 is a block diagram showing an example structure of a terminal device.

In the following, identical reference numerals refer to identical or at least functionally equivalent features. In part, different reference numerals referring to the same entities have been used in different figures.

DETAILED DESCRIPTION OF THE INVENTION

In the following description, reference is made to the accompanying figures, which form part of the disclosure, and which show, by way of illustration, specific aspects of embodiments of the invention or specific aspects in which embodiments of the present invention may be used. It is understood that embodiments of the invention may be used in other aspects and comprise structural or logical changes not depicted in the figures. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims.

For instance, it is understood that a disclosure in connection with a described method may also hold true for a corresponding device or system configured to perform the method and vice versa. For example, if one or more specific method steps are described, a corresponding device may include one or more functional units to perform the described one or more method steps (e.g. one unit performing the one or more steps, or a plurality of units each performing one or more of the plurality of steps) , even if such one or more units are not explicitly described or illustrated in the figures. On the other hand, if a specific apparatus is described based on one or more functional units, a corresponding method may include one step to perform the functionality of the one or more units (e.g. one step performing the functionality of the one or more units, or a plurality of steps each performing the functionality of one or more of the plurality of units) , even if such one or plurality of steps are not explicitly described or illustrated in the figures. Further, it is understood that the features of the various exemplary embodiments and/or aspects described herein may be combined with each other, unless specifically noted otherwise.

Video coding typically refers to the processing of a sequence of pictures, which form the video or video sequence. The terms “picture, ” “frame, ” and “image” may be used interchangeably in the field of video coding. Video coding comprises two parts, video encoding and video decoding. Video encoding is performed at the source side, and typically includes processing (e.g., by compression) the original video pictures to reduce the amount of data required for representing the video pictures (for more efficient storage and/or transmission) . Video decoding is performed at the destination side and typically includes the inverse processing relative to the encoder to reconstruct the video pictures. Embodiments referring to “coding” of video pictures (or pictures in general, as will be explained later) shall be understood to relate to both “encoding” and “decoding” of video pictures. The combination of the encoding part and the decoding part is also referred to as CODEC (COding and DECoding) .

In case of lossless video coding, the original video pictures can be reconstructed, i.e. the reconstructed video pictures have the same quality as the original video pictures (assuming no transmission loss or other data loss during storage or transmission) . In case of lossy video coding, further compression, e.g. by quantization, is performed, to reduce the amount of data representing the video pictures, which cannot be completely reconstructed at the decoder, i.e. the quality of the reconstructed video pictures is lower than or not as good as the quality of the original video pictures.

Several video coding standards since H. 261 belong to the group of “lossy hybrid video codecs” (i.e. combine spatial and temporal prediction in the sample domain and 2D transform coding for applying quantization in the transform domain) . Each picture of a video sequence is typically partitioned into a set of non-overlapping blocks and the coding is typically performed on a block level. In other words, at the encoder the video is typically processed, i.e. encoded, on a block (video block) level, e.g. by using spatial (intra picture) prediction and temporal (inter picture) prediction to generate a prediction block, subtracting the prediction block from the current block (block currently processed/to be processed) to obtain a residual block, transforming the residual block and quantizing the residual block in the transform domain to reduce the amount of data to be transmitted (compression) , whereas at the decoder the inverse processing relative to the encoder is applied to the encoded or compressed block to reconstruct the current block for representation. Furthermore, the encoder duplicates the decoder processing loop such that both will generate identical predictions (e.g. intra-and inter predictions) and/or re-constructions for processing, i.e. coding, the subsequent blocks.

Video picture processing (also referred to as moving picture processing) and still picture processing share many concepts and technologies or tools. In the following the term “picture” is used to refer to a video picture of a video sequence (as explained above) and/or to a still picture to avoid unnecessary repetitions and distinctions between video (moving) pictures and still pictures. In case the description refers to still pictures (or still images) only, the term “still picture” will be used.

Embodiments of an encoder 100, a decoder 200 and a coding system 300 are described with reference to FIGS. 1 to 3. Embodiments of the invention are described in more detail with reference to FIGS. 4 to 14.

FIG. 3 is a conceptual or schematic block diagram illustrating an embodiment of a coding system 300, e.g. a picture coding system 300. The coding system 300 comprises a source device 310 configured to provide encoded data 330, e.g. an encoded picture 330, e.g. to a destination device 320 for decoding the encoded data 330.

The source device 310 comprises an encoder 100 or encoding unit 100, and may additionally, i.e. optionally, comprise a picture source 312, a pre-processing unit 314, e.g. a picture pre-processing unit 314, and a communication interface or communication unit 318.

The picture source 312 may comprise or be any kind of picture capturing device, for example for capturing a real-world picture, and/or any kind of a picture generating device, for example a computer-graphics processor for generating a computer animated picture, or any kind of device for obtaining and/or providing a real-world picture, a computer animated picture (e.g. a screen content, a virtual reality (VR) picture) and/or any combination thereof (e.g. an augmented reality (AR) picture) . In the following, all these kinds of pictures and any other kind of picture will be referred to as “picture” or “image” , unless specifically described otherwise, while the previous explanations with regard to the term “picture” covering “video pictures” and “still pictures” still hold true, unless explicitly specified differently.

A (digital) picture is or can be regarded as a two-dimensional array or matrix of samples with intensity values. A sample in the array may also be referred to as pixel (short form of picture element) or a pel. The number of samples in horizontal and vertical direction (or axis) of the array or picture define the size and/or resolution of the picture. For representation of color, typically three color components are employed, i.e. the picture may be represented or include three sample arrays. In RGB format or color space a picture comprises a corresponding red, green and blue sample array. However, in video coding each pixel is typically represented in a luminance/chrominance format or color space, e.g. YCbCr, which comprises a luminance component denoted as Y (sometimes also L is used instead) and two chrominance components denoted as Cb and Cr. The luminance (or luma) component Y represents the brightness or grey level intensity (e.g. like in a grey-scale picture) , while the two chrominance (or chroma) components Cb and Cr represent the chromaticity or color information components. Accordingly, a picture in YCbCr format comprises a luminance sample array of luminance sample values (Y) , and two chrominance sample arrays of chrominance values (Cb and Cr) . Pictures in RGB format may be converted or transformed into YCbCr format and vice versa, the process is also known as color transformation or conversion. If a picture is monochrome, the picture may include only a luminance sample array.

The picture source 312 may be, for example a camera for capturing a picture, a memory, e.g. a picture memory, comprising or storing a previously captured or generated picture, and/or any kind of interface (internal or external) to obtain or receive a picture. The camera may be, for example, a local or integrated camera integrated in the source device, the memory may be a local or integrated memory, e.g. integrated in the source device. The interface may be, for example, an external interface to receive a picture from an external video source, for example an external picture capturing device like a camera, an external memory, or an external picture generating device, for example an external computer-graphics processor, computer or server. The interface can be any kind of interface, e.g. a wired or wireless interface, an optical interface, according to any proprietary or standardized interface protocol. The interface for obtaining the picture data 312 may be the same interface as or a part of the communication interface 318.

In distinction to the pre-processing unit 314 and the processing performed by the pre-processing unit 314, the picture or picture data 313 may also be referred to as raw picture or raw picture data 313.

Pre-processing unit 314 is configured to receive the (raw) picture data 313 and to perform pre-processing on the picture data 313 to obtain a pre-processed picture 315 or pre-processed picture data 315. Pre-processing performed by the pre-processing unit 314 may, e.g., comprise trimming, color format conversion (e.g. from RGB to YCbCr) , color correction, or de-noising.

The encoder 100 is configured to receive the pre-processed picture data 315 and provide encoded picture data 171 (further details will be described with reference to FIG. 1) .

Communication interface 318 of the source device 310 may be configured to receive the encoded picture data 171 and to directly transmit the encoded picture data 171 to another device, e.g. the destination device 320 or any other device, for storage or direct reconstruction, or to process the encoded picture data 171 before storing the encoded data 330 and/or transmitting the encoded data 330 to another device, e.g. the destination device 320 or any other device for decoding or storing.

The destination device 320 includes a decoder 200 or decoding unit 200, and may additionally include a communication interface or communication unit 322, a post-processing unit 326 and a display device 328.

The communication interface 322 of the destination device 320 is configured to receive the encoded picture data 171 or the encoded data 330, e.g. directly from the source device 310 or from any other source, e.g. a memory, e.g. an encoded picture data memory.

The communication interface 318 and the communication interface 322 may be configured to transmit and receive respectively the encoded picture data 171 or encoded data 330 via a direct communication link between the source device 310 and the destination device 320, e.g. a direct wired or wireless connection, or via any kind of network, e.g. a wired or wireless network or any combination thereof, or any kind of private and public network, or any combination thereof.

The communication interface 318 may be, e.g., configured to package the encoded picture data 171 into an appropriate format, e.g. packets, for transmission over a communication link or communication network, and may further comprise data loss protection and data loss recovery.

The communication interface 322, forming the counterpart of the communication interface 318, may be, e.g., configured to de-package the encoded data 330 to obtain the encoded picture data 171 and may further be configured to perform data loss protection and data loss recovery, e.g., error concealment.

Both communication interface 318 and communication interface 322 may be configured as unidirectional communication interfaces as indicated by the arrow for the encoded picture data 330 in FIG. 3 pointing from the source device 310 to the destination device 320, or bi-directional communication interfaces, and may be configured, e.g. to send and receive messages, e.g. to set up a connection, to acknowledge and/or re-send lost or delayed data including picture data, and exchange any other information related to the communication link and/or data transmission, e.g. encoded picture data transmission.

The decoder 200 is configured to receive the encoded picture data 171 and provide decoded picture data 231 or a decoded picture 231 (further details will be described with reference to FIG. 2) .

The post-processor 326 of destination device 320 is configured to post-process the decoded picture data 231, e.g. the decoded picture 231, to obtain post-processed picture data 327, e.g. a post-processed picture 327. The post-processing performed by the post-processing unit 326 may comprise, e.g. color format conversion (e.g. from YCbCr to RGB) , color correction, trimming, or re-sampling, or any other processing, e.g. for preparing the decoded picture data 231 for display, e.g. by display device 328.

The display device 328 of the destination device 320 is configured to receive the post-processed picture data 327 for displaying the picture, e.g. to a user or viewer. The display device 328 may be or comprise any kind of display for representing the reconstructed picture, e.g. an integrated or external display or monitor. The displays may, e.g. comprise cathode ray tubes (CRT) , liquid crystal displays (LCD) , plasma displays, organic light emitting diodes (OLED) displays or any kind of other display …beamer, hologram (3D) , …

Although FIG. 3 depicts the source device 310 and the destination device 320 as separate devices, embodiments of devices may also comprise both or both functionalities, the source device 310 or corresponding functionality and the destination device 320 or corresponding functionality. In such embodiments the source device 310 or corresponding functionality and the destination device 320 or corresponding functionality may be implemented using the same hardware and/or software or by separate hardware and/or software or any combination thereof.

As will be apparent to a skilled person in the art based on the description, the existence and (exact) split of functionalities of the different units or functionalities within the source device 310 and/or destination device 320 as shown in FIG. 3 may vary depending on the actual device and application.

Therefore, the source device 310 and the destination device 320 as shown in FIG. 3 are just example embodiments of the invention and embodiments of the invention are not limited to those shown in FIG. 3.

Source device 310 and destination device 320 may comprise any of a wide range of devices, including any kind of handheld or stationary devices, e.g. notebook or laptop computers, mobile phones, smart phones, tablets or tablet computers, cameras, desktop computers, set-top boxes, televisions, display devices, digital media players, video gaming consoles, video streaming devices, broadcast receiver device, or the like. (also servers and work-stations for large scale professional encoding/decoding, e.g. network entities) and may use no or any kind of operating system.

FIG. 1 shows a schematic/conceptual block diagram of an embodiment of an encoder 100, e.g. a picture encoder 100, which comprises an input 102, a residual calculation unit 104, a transformation unit 106, a quantization unit 108, an inverse quantization unit 110, and inverse transformation unit 112, a reconstruction unit 114, a buffer 116, a loop filter 120, a decoded picture buffer (DPB) 130, a prediction unit 160 including an inter estimation unit 142, an inter prediction unit 144, an intra-estimation unit 152, an intra-prediction unit 154, a mode selection unit 162, an entropy encoding unit 170, and an output 172. A video encoder 100 as shown in FIG. 1 may also be referred to as hybrid video encoder or a video encoder according to a hybrid video codec.

For example, the residual calculation unit 104, the transformation unit 106, the quantization unit 108, and the entropy encoding unit 170 form a forward signal path of the encoder 100, whereas, for example, the inverse quantization unit 110, the inverse transformation unit 112, the reconstruction unit 114, the buffer 116, the loop filter 120, the decoded picture buffer (DPB) 130, the inter prediction unit 144, and the intra-prediction unit 154 form a backward signal path of the encoder, wherein the backward signal path of the encoder corresponds to the signal path of the decoder (see decoder 200 in Fig. 2) .

The encoder is configured to receive, e.g. by input 102, a picture 101 or a picture block 103 of the picture 101, e.g. picture of a sequence of pictures forming a video or video sequence. The picture block 103 may also be referred to as current picture block or picture block to be coded, and the picture 101 as current picture or picture to be coded (in particular in video coding to distinguish the current picture from other pictures, e.g. previously encoded and/or decoded pictures of the same video sequence, i.e. the video sequence which also comprises the current picture) .

Embodiments of the encoder 100 may include a partitioning unit (not depicted in FIG. 1) , e.g., which may also be referred to as picture partitioning unit, configured to partition the picture 101 into a plurality of blocks, e.g., blocks like block 103, typically into a plurality of non-overlapping blocks. The partitioning unit may be configured to use the same block size for all pictures of a video sequence and the corresponding grid defining the block size, or to change the block size between pictures or subsets or groups of pictures, and partition each picture into the corresponding blocks.

Like the picture 101, the block 103 again is or can be regarded as a two-dimensional array or matrix of samples with intensity values (sample values) , although of smaller dimension than the picture 101. In other words, the block 103 may comprise, e.g., one sample array (e.g. a luma array in case of a monochrome picture 101) or three sample arrays (e.g. a luma and two chroma arrays in case of a color picture 101) or any other number and/or kind of arrays depending on the color format applied. The number of samples in horizontal and vertical direction (or axis) of the block 103 define the size of block 103.

Encoder 100 as shown in FIG. 1 is configured to encode the picture 101 block by block, e.g. the encoding and prediction is performed per block 103.

The residual calculation unit 104 is configured to calculate a residual block 105 based on the picture block 103 and a prediction block 165 (further details about the prediction block 165 are provided later) , e.g. by subtracting sample values of the prediction block 165 from sample values of the picture block 103, sample by sample (pixel by pixel) to obtain the residual block 105 in the sample domain.

The transformation unit 106 is configured to apply a transformation, e.g. a spatial frequency transform or a linear spatial transform, e.g. a discrete cosine transform (DCT) or discrete sine transform (DST) , on the sample values of the residual block 105 to obtain transformed coefficients 107 in a transform domain. The transformed coefficients 107 may also be referred to as transformed residual coefficients and represent the residual block 105 in the transform domain.

The transformation unit 106 may be configured to apply integer approximations of DCT/DST, such as the core transforms specified for HEVC/H. 265. Compared to an orthonormal DCT transform, such integer approximations are typically scaled by a certain factor. In order to preserve the norm of the residual block which is processed by forward and inverse transforms, additional scaling factors are applied as part of the transform process. The scaling factors are typically chosen based on certain constraints like scaling factors being a power of two for shift operation, bit depth of the transformed coefficients, tradeoff between accuracy and implementation costs, etc. Specific scaling factors are, for example, specified for the inverse transform, e.g. by inverse transformation unit 212, at a decoder 200 (and the corresponding inverse transform, e.g. by inverse transformation unit 112 at an encoder 100) and corresponding scaling factors for the forward transform, e.g. by transformation unit 106, at an encoder 100 may be specified accordingly.

The quantization unit 108 is configured to quantize the transformed coefficients 107 to obtain quantized coefficients 109, e.g. by applying scalar quantization or vector quantization. The quantized coefficients 109 may also be referred to as quantized residual coefficients 109. For example for scalar quantization, different scaling may be applied to achieve finer or coarser quantization. Smaller quantization step sizes correspond to finer quantization, whereas larger quantization step sizes correspond to coarser quantization. The applicable quantization step size may be indicated by a quantization parameter (QP) . The quantization parameter may for example be an index to a predefined set of applicable quantization step sizes. For example, small quantization parameters may correspond to fine quantization (small quantization step sizes) and large quantization parameters may correspond to coarse quantization (large quantization step sizes) or vice versa. The quantization may include division by a quantization step size and corresponding or inverse de-quantization, e.g. by inverse quantization 110, may include multiplication by the quantization step size.

Embodiments according to HEVC, may be configured to use a quantization parameter to determine the quantization step size. Generally, the quantization step size may be calculated based on a quantization parameter using a fixed point approximation of an equation including division. Additional scaling factors may be introduced for quantization and de-quantization to restore the norm of the residual block, which might be modified because of the scaling used in the fixed point approximation of the equation for quantization step size and quantization parameter. In one example implementation, the scaling of the inverse transform and de-quantization might be combined. Alternatively, customized quantization tables may be used and signaled from an encoder to a decoder, e.g. in a bit-stream. The quantization is a lossy operation, wherein the loss increases with increasing quantization step sizes.

Embodiments of the encoder 100 (or respectively of the quantization unit 108) may be configured to output the quantization scheme and quantization step size, e.g. by means of the corresponding quantization parameter, so that a decoder 200 may receive and apply the corresponding inverse quantization. Embodiments of the encoder 100 (or quantization unit 108) may be configured to output the quantization scheme and quantization step size, e.g. directly or entropy encoded via the entropy encoding unit 170 or any other entropy coding unit.

The inverse quantization unit 110 is configured to apply the inverse quantization of the quantization unit 108 on the quantized coefficients to obtain de-quantized coefficients 111, e.g. by applying the inverse of the quantization scheme applied by the quantization unit 108 based on or using the same quantization step size as the quantization unit 108. The de-quantized coefficients 111 may also be referred to as de-quantized residual coefficients 111 and correspond -although typically not identical to the transformed coefficients due to the loss by quantization -to the transformed coefficients 108.

The inverse transformation unit 112 is configured to apply the inverse transformation of the transformation applied by the transformation unit 106, e.g. an inverse discrete cosine transform (DCT) or inverse discrete sine transform (DST) , to obtain an inverse transformed block 113 in the sample domain. The inverse transformed block 113 may also be referred to as inverse transformed de-quantized block 113 or inverse transformed residual block 113.

The reconstruction unit 114 is configured to combine the inverse transformed block 113 and the prediction block 165 to obtain a reconstructed block 115 in the sample domain, e.g. by sample wise adding the sample values of the decoded residual block 113 and the sample values of the prediction block 165.

The buffer unit 116 (or “buffer, ” “line buffer” 116) is configured to buffer or store the reconstructed block and the respective sample values, for example for intra estimation and/or intra prediction. In further embodiments, the encoder may be configured to use unfiltered reconstructed blocks and/or the respective sample values stored in buffer unit 116 for any kind of estimation and/or prediction.

Embodiments of the encoder 100 may be configured such that, e.g. the buffer unit 116 is not only used for storing the reconstructed blocks 115 for intra estimation 152 and/or intra prediction 154 but also for the loop filter unit 120, and/or such that, e.g. the buffer unit 116 and the decoded picture buffer unit 130 form one buffer. Further embodiments may be configured to use filtered blocks 121 and/or blocks or samples from the decoded picture buffer 130 as input or basis for intra estimation 152 and/or intra prediction 154.

The loop filter unit 120 (also referred to as “loop filter” 120) is configured to filter the reconstructed block 115 to obtain a filtered block 121, e.g. by applying a de-blocking sample-adaptive offset (SAO) filter or other filters, e.g. sharpening or smoothing filters or collaborative filters. The filtered block 121 may also be referred to as filtered reconstructed block 121. The loop filter 120 is in the following also referred to as deblocking filter. Further details of the loop filter unit 120 will be described below, e.g., based on Fig. 17 or FIG. 10.

Embodiments of the loop filter unit 120 may comprise a filter analysis unit and the actual filter unit (not shown in FIG. 1) . The filter analysis unit is configured to determine loop filter parameters for the actual filter. The filter analysis unit may be configured to apply fixed pre-determined filter parameters to the actual loop filter, adaptively select filter parameters from a set of predetermined filter parameters or adaptively calculate filter parameters for the actual loop filter.

Embodiments of the loop filter unit 120 may comprise one or a plurality of filters (loop filter components/subfilters) (not shown in FIG. 1) , e.g., one or more of different kinds or types of filters, e.g. connected in series or in parallel or in any combination thereof, wherein each of the filters may comprise individually or jointly with other filters of the plurality of filters a filter analysis unit to determine the respective loop filter parameters, e.g. as described in the previous paragraph.

Embodiments of the encoder 100 (respectively loop filter unit 120) may be configured to output the loop filter parameters, e.g., directly or entropy encoded via the entropy encoding unit 170 or any other entropy coding unit, so that, e.g., a decoder 200 may receive and apply the same loop filter parameters for decoding.

The decoded picture buffer (DPB) 130 is configured to receive and store the filtered block 121. The decoded picture buffer 130 may be further configured to store other previously filtered blocks, e.g. previously reconstructed and filtered blocks 121, of the same current picture or of different pictures, e.g. previously reconstructed pictures, and may provide complete previously reconstructed, i.e. decoded, pictures (and corresponding reference blocks and samples) and/or a partially reconstructed current picture (and corresponding reference blocks and samples) , for example for inter estimation and/or inter prediction.

Further embodiments of the invention may also be configured to use the previously filtered blocks and corresponding filtered sample values of the decoded picture buffer 130 for any kind of estimation or prediction, e.g. intra and inter estimation and prediction.

The prediction unit 160, also referred to as block prediction unit 160, is configured to receive or obtain the picture block 103 (current picture block 103 of the current picture 101) and decoded or at least reconstructed picture data, e.g. reference samples of the same (current) picture from buffer 116 and/or decoded picture data 231 from one or a plurality of previously decoded pictures from decoded picture buffer 130, and to process such data for prediction, i.e. to provide a prediction block 165, which may be an inter-predicted block 145 or an intra-predicted block 155.

The mode selection unit 162 may be configured to select a prediction mode (e.g. an intra or inter prediction mode) and/or a

corresponding prediction block

145 or 155 to be used as prediction block 165 for the calculation of the residual block 105 and for the reconstruction of the reconstructed block 115.

Embodiments of the mode selection unit 162 may be configured to select the prediction mode (e.g. from those supported by prediction unit 160) , which provides the best match or in other words the minimum residual (minimum residual means better compression for transmission or storage) , or a minimum signaling overhead (minimum signaling overhead means better compression for transmission or storage) , or which considers or balances both. The mode selection unit 162 may be configured to determine the prediction mode based on rate distortion optimization (RDO) , i.e. select the prediction mode which provides a minimum rate distortion optimization or which associated rate distortion at least fulfills a prediction mode selection criterion.

The prediction processing (e.g., prediction unit 160) and mode selection (e.g. by mode selection unit 162) performed by an example encoder 100 will be explained in more detail below.

As described above, encoder 100 is configured to determine or select the best or an optimum prediction mode from a set of (pre-determined) prediction modes. The set of prediction modes may comprise, e.g., intra-prediction modes and/or inter-prediction modes.

The set of intra-prediction modes may comprise 32 different intra-prediction modes, e.g. non-directional modes like DC (or mean) mode and planar mode, or directional modes, e.g. as defined in H. 264, or may comprise 65 different intra-prediction modes, e.g. non-directional modes like DC (or mean) mode and planar mode, or directional modes, e.g. as defined in H. 265.

The set of (or possible) inter-prediction modes depend on the available reference pictures (i.e. previous at least partially decoded pictures, e.g. stored in DBP 230) and other inter-prediction parameters, e.g. whether the whole reference picture or only a part, e.g. a search window area around the area of the current block, of the reference picture is used for searching for a best matching reference block, and/or e.g. whether pixel interpolation is applied, e.g. half/semi-pel and/or quarter-pel interpolation, or not.

Additionally to the above prediction modes, skip mode and/or direct mode may be applied.

The prediction unit 160 may be further configured to partition the block 103 into smaller block partitions or sub-blocks, e.g. iteratively using quad-tree partitioning (QT) , binary partitioning (BT) or triple-tree partitioning (TT) or any combination thereof, and to perform, e.g. the prediction for each of the block partitions or sub-blocks, wherein the mode selection comprises the selection of the tree-structure of the partitioned block 103 and the prediction modes applied to each of the block partitions or sub-blocks.

The inter estimation unit 142, also referred to as inter picture estimation unit 142, is configured to receive or obtain the picture block 103 (current picture block 103 of the current picture 101) and a decoded picture 231, or at least one or a plurality of previously reconstructed blocks, e.g., reconstructed blocks of one or a plurality of other/different previously decoded pictures 231, for inter estimation (or “inter picture estimation” ) . For example, a video sequence may comprise the current picture and the previously decoded pictures 231, or in other words, the current picture and the previously decoded pictures 231 may be part of or form a sequence of pictures forming a video sequence.

The encoder 100 may be configured to select a reference block from a plurality of reference blocks of the same or different pictures of the plurality of other pictures and provide a reference picture (or reference picture index, …) and/or an offset (spatial offset) between the position (x, y coordinates) of the reference block and the position of the current block as inter estimation parameters 143 to the inter prediction unit 144. This offset is also called motion vector (MV) . The inter estimation is also referred to as motion estimation (ME) and the inter prediction also motion prediction (MP) .

The inter prediction unit 144 is configured to obtain, e.g. receive, an inter prediction parameter 143 and to perform inter prediction based on or using the inter prediction parameter 143 to obtain an inter prediction block 145.

Although FIG. 1 shows two distinct units (or steps) for the inter-coding, namely inter estimation 142 and inter prediction 144, both functionalities may be performed as one (inter estimation) and include calculating the inter prediction block, i.e., the inter prediction 144) , e.g., by testing all possible or a predetermined subset of possible inter-prediction modes iteratively while storing the currently best inter prediction mode and respective inter prediction block, and using the currently best inter prediction mode and respective inter prediction block as the (final) inter prediction parameter 143 and inter prediction block 145 without performing another time the inter prediction 144.

The intra estimation unit 152 is configured to obtain, e.g. receive, the picture block 103 (current picture block) and one or a plurality of previously reconstructed blocks, e.g., reconstructed neighbor blocks, of the same picture for intra estimation. The encoder 100 may, e.g., be configured to select an intra prediction mode from a plurality of (predetermined) intra prediction modes and provide it as intra estimation parameter 153 to the intra prediction unit 154.

Embodiments of the encoder 100 may be configured to select the intra-prediction mode based on an optimization criterion, e.g., minimum residual (e.g. the intra-prediction mode providing the prediction block 155 most similar to the current picture block 103) or minimum rate distortion.

The intra prediction unit 154 is configured to determine based on the intra prediction parameter 153, e.g., using the selected intra prediction mode 154 to obtain the intra prediction block 155.

Although FIG. 1 shows two distinct units (or steps) for the intra-coding, namely intra estimation 152 and intra prediction 154, both functionalities may be performed as one (intra estimation) and include calculating the intra prediction block, i.e., the intra prediction 154) , e.g. by testing all possible or a predetermined subset of possible intra-prediction modes iteratively while storing the currently best intra prediction mode and respective intra prediction block, and using the currently best intra prediction mode and respective intra prediction block as the (final) intra prediction parameter 153 and intra prediction block 155 without performing another time the intra prediction 154.

The entropy encoding unit 170 is configured to apply an entropy encoding algorithm or scheme (e.g. a variable length coding (VLC) scheme, an context adaptive VLC scheme (CALVC) , an arithmetic coding scheme, a context adaptive binary arithmetic coding (CABAC) ) on the quantized residual coefficients 109, inter prediction parameters 143, intra prediction parameter 153, and/or loop filter parameters, individually or jointly (or not at all) to obtain encoded picture data 171 which can be output by the output 172, e.g. in the form of an encoded bit-stream 171.

Other structural variations of the video encoder 100 can be used to encode the video stream. For example, a non-transform based encoder 100 can quantize the residual signal directly without the transform processing unit for certain blocks or frames. In another implementation, an encoder 100 can have the quantization unit and the inverse quantization unit combined into a single unit.

FIG. 2 shows an exemplary video decoder 200 configured to receive encoded picture data (e.g. encoded bit-stream) 171, e.g. encoded by encoder 100, to obtain a decoded picture 231.

The decoder 200 comprises an input 202, an entropy decoding unit 204, an inverse quantization unit 210, an inverse transformation unit 212, a reconstruction unit 214, a buffer 216, a loop filter 220, a decoded picture buffer 230, a prediction unit 260, an inter prediction unit 244, an intra prediction unit 254, a mode selection unit 260 and an output 232.

The entropy decoding unit 204 is configured to perform entropy decoding to the encoded picture data 171 to obtain, e.g., quantized coefficients 209 and/or decoded coding parameters (not shown in Fig. 2) , e.g. (decoded) any or all of inter prediction parameters 143, intra prediction parameter 153, and/or loop filter parameters.

In embodiments of the decoder 200, the inverse quantization unit 210, the inverse transformation unit 212, the reconstruction unit 214, the buffer 216, the loop filter 220, the decoded picture buffer 230, the prediction unit 260 and the mode selection unit 262 are configured to perform the inverse processing of the encoder 100 (and the respective functional units) to decode the encoded picture data 171.

In particular, the inverse quantization unit 210 may be identical in function to the inverse quantization unit 110, the inverse transformation unit 212 may be identical in function to the inverse transformation unit 112, the reconstruction unit 214 may be identical in function reconstruction unit 114, the buffer 216 may be identical in function to the buffer 116, the loop filter 220 may be identical in function to the loop filter 220 (with regard to the actual loop filter as the loop filter 220 typically does not comprise a filter analysis unit to determine the filter parameters based on the original image 101 or block 103 but receives (explicitly or implicitly) or obtains the filter parameters used for encoding, e.g. from entropy decoding unit 204) , and the decoded picture buffer 230 may be identical in function to the decoded picture buffer 130.

The prediction unit 260 may comprise an inter prediction unit 244 and an intra prediction unit 254, where the inter prediction unit 244 may be identical in function to the inter prediction unit 144, and the intra prediction unit 254 may be identical in function to the intra prediction unit 154. The prediction unit 260 and the mode selection unit 262 are typically configured to perform the block prediction and/or obtain the predicted block 265 from the encoded data 171 only (without any further information about the original image 101) and to receive or obtain (explicitly or implicitly) the prediction parameters 143 or 153 and/or the information about the selected prediction mode, e.g. from the entropy decoding unit 204.

The decoder 200 is configured to output the decoded picture 231, e.g., via output 232, for presentation or viewing to a user.

Although embodiments of the invention have been primarily described based on video coding, it should be noted that embodiments of the encoder 100 and decoder 200 (and correspondingly the system 300) may also be configured for still picture processing or coding, i.e. the processing or coding of an individual picture independent of any preceding or consecutive picture as in video coding. In general only inter-estimation 142, inter-prediction 144, 242 are not available in case the picture processing coding is limited to a single picture 101. Most if not all other functionalities (also referred to as tools or technologies) of the video encoder 100 and video decoder 200 may equally be used for still pictures, e.g. partitioning, transformation (scaling) 106, quantization 108, inverse quantization 110, inverse transformation 112, intra-estimation 142,

intra-prediction

154, 254 and/or

loop filtering

120, 220, and entropy coding 170 and entropy decoding 204.

The present invention relates to the inner workings of the deblocking filter, also referred to as

loop filter

120, 220 in FIG. 1 and FIG. 2. Further details of the

loop filter unit

120, 220 will be described below with reference to FIG. 17, FIG. 7 or FIG. 10 to FIG. 12A and FIG. 12B.

Video coding schemes such as H. 264/AVC and HEVC are designed along the successful principle of block-based hybrid video coding. Using this principle a picture is first partitioned into blocks and then each block is predicted by using intra-picture or inter-picture prediction. These blocks are coded relatively from the neighboring blocks and approximate the original signal with some degree of similarity. Since coded blocks only approximate the original signal, the difference between the approximations may cause discontinuities at the prediction and transform block boundaries. These discontinuities are attenuated by the deblocking filter. HEVC replaces the macroblock structure of H. 264/AVC with the concept of coding tree unit (CTU) of maximum size 64x64 pixels. The CTU can further be partitioned into a quadtree-decomposition scheme into smaller coding units (CU) , which can be subdivided down to a minimum size of 8 x 8 pixels. HEVC also introduces the concepts of prediction blocks (PB) and Transform blocks (TB) .

In HEVC two filters are defined in deblocking filter: the normal filter and the strong filter. The normal filter modifies at most two samples on both sides of an edge. In strong filter three additional checking between the samples along the edge and some pre-defined threshold are evaluated. When all of those checking are true then the strong filter is applied. The strong filter has a more intensive smoothing effect for samples along the edge and can modify at most three samples on both sides of an edge.

ITU-T VCEG (Q6/16) and ISO/IEC MPEG (JTC 1/SC 29/WG 11) are studying the next generation video codec: Versatile Video Coding (VVC) . This new video codec standard aims a compression capability that significantly exceeds that of the current HEVC standard (including its current extensions and near-term extensions for screen content coding and high-dynamic-range coding) . The groups are working together on this exploration activity in a joint collaboration effort known as the Joint Video Exploration Team (JVET) to evaluate compression technology designs proposed by their experts in this area.

The VVC Test Model (VTM) describes the features that are under coordinated test model study by the Joint Video Exploration Team (JVET) of ITU-T VCEG and ISO/IEC MPEG as potential enhanced video coding technology beyond the capabilities of HEVC.

VTM software uses a new partitioning block structure scheme referred to as Quadtree plus binary tree plus triple tree (QTBTTT) .

The QTBTTT structure removes the concepts of multiple partition types i.e., it removes the separation of coding units (CU) , prediction units (PU) and transform units (TU) . Therefore CU = PU = TU.

QTBTTT supports more flexible CU partition shapes wherein a CU can have either square or rectangular shape. The minimum width and height of a CU can be 4 samples and the sizes of the CU can also be 4 x N or N x 4 where N can take values in the range [4, 8, 16, 32] . Furthermore, the largest CTU size has been increased to 128x128 pixels, which is 4 times larger than the CTU size in HEVC.

For rectangle CUs, the distortion close to the shorter edge can be obvious which results in block artifact even when the HEVC strong filter is applied. The block artifact can also be observed along the edge of large CUs, where distortion are significant due to larger prediction and transform operations.

Additional Sub-PU tools like Affine, STMVP and ATMVP have now been adopted to the VVC standard. Sub-PU tools like planar motion vector prediction mode may be adopted to the VVC standard in the future.

The sub-block based inter prediction mode (sub-block motion prediction mode) may include: any one of the following modes:

Advanced temporal motion vector prediction (ATMVP) mode,

Spatial-temporal motion vector prediction (STMVP) mode,

Affine prediction mode, and

Planar motion vector prediction mode.

Affine prediction mode:

In HEVC, only translation motion model is applied for motion compensation prediction (MCP) . While in the real world, there are many kinds of motion, e.g. zoom in/out, rotation, perspective motions and the other irregular motions. Hence, affine model using 4 parameters (referred to as 4-parameter affine) and affine model using 6 parameters (referred to as 6-parameter affine) are proposed.

4-parameter affine

Referring to FIG. 4, the affine motion field of the block is described by two control point motion vectors.

The motion vector field (MVF) of a block at a sample location (x, y) is described by the following equation:

where (v _0x, v _0y) is motion vector of the top-left corner control point, and (v _1x, v _1y) is motion vector of the top-right corner control point.

In order to further simplify the motion compensation prediction, sub-block based affine transform prediction is applied. The sub-block size M×N is derived as in Equation (2) , where MvPre is the motion vector fraction accuracy, (v _2x, v _2y) is motion vector of the bottom-left control point, calculated according to Equation 1.

After derived by Equation 2, M and N should be adjusted downward if necessary to make it a divisor of w and h, respectively.

To derive motion vector of each M×N sub-block, the motion vector of the center sample of each sub-block, as shown in FIG. 5, is calculated according to Equation 1. Then the motion compensation interpolation filters are applied to generate the prediction of each sub-block with derived motion vector.

6-parameter affine

When the 6-parameter affine model is applied, the current block is divided into sub-blocks in the same way as for the 4-parameter affine model. The motion vector mv= [mv ^x,mv ^y] at a location (x, y) in W×H block can be derived from the MVs of the three control points (mv ₀, mv ₁, and mv ₂) as follows

Planar Motion Vector Prediction

To generate a smooth fine granularity motion field, FIG. 7 provides a conceptual description of the planar motion vector prediction process.

Planar motion vector prediction is achieved by averaging a horizontal and vertical linear interpolation on 4x4 block basis as follows.

P (x, y) = (H×P _h (x, y) +W×P _v (x, y) +H×W) / (2×H×W)

W and H denote the width and the height of the block. (x, y) is the coordinates of current sub-block relative to the above left corner sub-block. All the distances are denoted by the pixel distances divided by 4. P (x, y) is the motion vector of current sub-block.

The horizontal prediction P _h (x, y) and the vertical prediction P _v (x, y) for location (x, y) are calculated as follows:

P _h (x, y) = (W-1-x) ×L (-1, y) + (x+1) ×R (W, y) (6)

P _v (x, y) = (H-1-y) ×A (x, -1) + (y+1) ×B (x, H) (7)

where L (-1, y) and R (W, y) are the motion vectors of the 4x4 blocks to (7) the left and right of the current block. A (x, -1) and B (x, H) are the motion vectors of the 4x4 blocks to the above and bottom of the current block.

The reference motion information of the left column and above row neighbour blocks are derived from the spatial neighbour blocks of current block.

The reference motion information of the right column and bottom row neighbour blocks are derived as follows.

1) Derive the motion information of the bottom right temporal neighbour 4x4 block

2) Compute the motion vectors of the right column neighbour 4x4 blocks, using the derived motion information of the bottom right neighbour 4x4 block along with the motion information of the above right neighbour 4x4 block, as described in Equation (8) .

3) Compute the motion vectors of the bottom row neighbour 4x4 blocks, using the derived motion information of the bottom right neighbour 4x4 block along with the motion information of the bottom left neighbour 4x4 block, as described in Equation (9) .

R (W, y) = ( (H-y-1) ×AR + (y+1) ×BR) /H (8)

B (x, H) = ( (W-x-1) ×BL+ (x+1) ×BR) /W (9)

where AR is the motion vector of the above right spatial neighbour 4x4 block, BR is the motion vector of the bottom right temporal neighbour 4x4 block, and BL is the motion vector of the bottom left spatial neighbour 4x4 block.

The motion information obtained from the neighbouring blocks for each list is scaled to the first reference picture for a given list.

Advanced temporal motion vector prediction (ATMVP)

Advanced temporal motion vector prediction (ATMVP) method allows each CU to fetch multiple sets of motion information from multiple blocks smaller than the current CU in the collocated reference picture. In spatial-temporal motion vector prediction (STMVP) method motion vectors of the sub-CUs are derived recursively by using the temporal motion vector predictor and spatial neighbouring motion vector.

Advanced temporal motion vector prediction

In the advanced temporal motion vector prediction (ATMVP) method, the motion vectors temporal motion vector prediction (TMVP) is modified by fetching multiple sets of motion information (including motion vectors and reference indices) from blocks smaller than the current CU. As shown in FIG. 8, the sub-CUs are square N×N blocks (N is set to 4 by default) .

ATMVP predicts the motion vectors of the sub-CUs within a CU in two steps. The first step is to identify the corresponding block in a reference picture with a so-called temporal vector. The reference picture is called the motion source picture. The second step is to split the current CU into sub-CUs and obtain the motion vectors as well as the reference indices of each sub-CU from the block corresponding to each sub-CU, as shown in FIG. 8.

In the first step, a reference picture and the corresponding block is determined by the motion information of the spatial neighbouring blocks of the current CU. To avoid the repetitive scanning process of neighbouring blocks, the first merge candidate in the merge candidate list of the current CU is used. The first available motion vector as well as its associated reference index are set to be the temporal vector and the index to the motion source picture. This way, in ATMVP, the corresponding block may be more accurately identified, compared with TMVP, wherein the corresponding block (sometimes called collocated block) is always in a bottom-right or center position relative to the current CU.

In the second step, a corresponding block of the sub-CU is identified by the temporal vector in the motion source picture, by adding to the coordinate of the current CU the temporal vector. For each sub-CU, the motion information of its corresponding block (the smallest motion grid that covers the center sample) is used to derive the motion information for the sub-CU. After the motion information of a corresponding N×N block is identified, it is converted to the motion vectors and reference indices of the current sub-CU, in the same way as TMVP of HEVC, wherein motion scaling and other procedures apply. For example, the decoder checks whether the low-delay condition (i.e. the POCs of all reference pictures of the current picture are smaller than the POC of the current picture) is fulfilled and possibly uses motion vector MV _x (the motion vector corresponding to reference picture list X) to predict motion vector MV _y (with X being equal to 0 or 1 and Y being equal to 1-X) for each sub-CU.

Spatial-temporal motion vector prediction (STMVP)

In this method, the motion vectors of the sub-CUs are derived recursively, following raster scan order. FIG. 9 illustrates this concept. Let us consider an 8×8 CU which contains four 4×4 sub-CUs A, B, C, and D. The neighbouring 4×4 blocks in the current frame are labelled as a, b, c, and d.

The motion derivation for sub-CU A starts by identifying its two spatial neighbours. The first neighbour is the N×N block above sub-CU A (block c) . If this block c is not available or is intra coded the other N×N blocks above sub-CU A are checked (from left to right, starting at block c) . The second neighbour is a block to the left of the sub-CU A (block b) . If block b is not available or is intra coded other blocks to the left of sub-CU A are checked (from top to bottom, starting at block b) . The motion information obtained from the neighbouring blocks for each list is scaled to the first reference frame for a given list. Next, temporal motion vector predictor (TMVP) of sub-block A is derived by following the same procedure of TMVP derivation as specified in HEVC. The motion information of the collocated block at location D is fetched and scaled accordingly. Finally, after retrieving and scaling the motion information, all available motion vectors (up to 3) are averaged separately for each reference list. The averaged motion vector is assigned as the motion vector of the current sub-CU.

As illustrated in FIG. 10, block artifact may be created when adjacent sub-blocks are predicted from non-adjacent areas in the reference picture. The transform coding is whole-block-based while the motion prediction is sub-block-based. The size of motion predicted sub-blocks varies from 4x4, 4x8, 8x4 and 8x8 to 64x64 luma samples, while the size of block transforms and intra-predicted blocks varies from 4x4 to 128x128 samples. These sub-blocks are coded relatively independently from their neighboring sub-blocks and approximate the original signal with some degree of similarity. Since coded sub-blocks only approximate the original signal, the difference between the approximations may cause discontinuities at the prediction and transform block boundaries. For example, motion prediction of the adjacent sub-blocks may come from the non-adjacent areas of a reference picture (see Fig. 10) or even from different reference pictures.

Embodiments of the invention provide deblocking of sub-block boundaries between sub-blocks of a current block which is predicted using sub-block based motion prediction mode.

For sub-PU tools, such as ATMVP, Spatial-temporal motion vector prediction, Affine motion compensation prediction or Planar Motion Vector Prediction, deblocking may be selectively or conditionally performed for the sub-pu boundaries which overlap with an 8 x 8 grid or a 4x4 grid.

Deblocking filter is applied on the sub-block edge between two sub-blocks (such as a first sub-block and a second sub-block) when the current block has no residual data and the reference block of the first sub-block and the reference block of the second sub-block are discontinuous. Deblocking filter may not be applied on the sub-block edge between two sub-blocks when the current block has residual data. Deblocking filter might be applied or not applied on the sub-block edge between two sub-blocks when the current block has no residual data.

Embodiments of the invention may be applied to the Deblocking Determination Unit 604 in FIG. 17, which determines whether a block edge applies deblocking filtering, and when the deblocking determination unit 604 determines that deblocking filtering will be applied to the block edge, the deblocking determination unit 604 also determines the type (normal, strong) of the filtering.

It is noted that the invention is not limited to a specific deblocking filter implementation and that the HEVC deblocking filter is only one of the deblocking filter implementations. The invention modifies the filter application determination process by taking into account whether or not the current block has residual data, and/or whether a reference block of the first sub-block and a reference block of the second sub-block are continuous.

FIG. 11 is a block diagram illustrating an exemplary deblocking method according to the techniques described in this disclosure (further details will be described below) .

Referring to FIG. 11, an embodiment of the deblocking method for use in an image encoding and/or an image decoding is shown. The deblocking method includes:

In step 1101: determining sub-block edges (sub-block boundaries) between sub-blocks of a current block which is predicted using sub-block based inter prediction mode (sub-block motion prediction mode) , the sub-block edges comprise a sub-block edge between a first sub-block P and a second sub-block Q;

In step 1103, determining whether or not the current block has residual data. When the current block has residual data, the method is terminated, i.e., the sub-block edge is not to be filtered by applying a deblocking filter, when the first determination result indicates residual data of the current block; otherwise, the method jump to the step 1105;

In step 1105: determining whether a reference block of the first sub-block and a reference block of the second sub-block are continuous. When the current block has no residual data and the reference block of the first sub-block and the reference block of the second sub-block are discontinuous or discontinuities, the method proceeds to step 1107; otherwise, the method is terminated.

In step 1107: applying the deblocking filter to values of samples near the sub-block edge between the first sub-block P and the second sub-block Q.

FIG. 12A shows decisions for each four-sample segment of sub-block boundary for a 4x4 motion compensation unit.

FIG. 12B shows decisions for each four-sample segment of sub-block boundary for an 8x8 motion compensation unit.

The deblocking filtering decisions for a sub-block boundary including the decisions between the strong and the normal filtering are summarized in a flowchart in FIG. 11.

FIG. 13 is a block diagram depicting a first flag 1301, such as coded_block_flag provided in the bitstream BTS output from the video encoder of FIG. 2 or provided to the video decoder of FIG. 3

In an implementation of the embodiment of the present disclosure, as illustrated in FIG. 11, wherein the step of determining whether the current block has residual data or not includes:

when the value of a first flag 1301 (such as a coded_block_flag) parsed from a bitstream is equal to a first value (such as 0) , the current block has no residual data; or

when the value of a first flag 1301 (such as a coded_block_flag) parsed from a bitstream is equal to a second value (such as 1) , the current block has residual data.

In an implementation of the embodiment of the present disclosure, wherein the step of determining whether a reference block of the first sub-block and a reference block of the second sub-block are continuous, comprising:

when a reference index of the first sub-block and a reference index of the second sub-block are same and the motion vector difference between a motion vector of the first sub-block and a motion vector of the second sub-block is larger than a threshold (predefined pixel or pixels, such as one pixel) , a reference block of the first sub-block and a reference block of the second sub-block are discontinuous; or

In an implementation of the embodiment of the present disclosure, wherein each sub-block of the current block has the own motion information, inter prediction (motion compensation) is performed based on the motion information of each sub-block to obtain the predictor (prediction block) of each sub-block.

In an example, each sub-block of the current block (such as a CU) is a motion compensation block or a motion compensation unit.

It is assumed that a size of the motion compensation unit is MxN (M is less than or equal to the width W of the current encoding block, N is less than or equal to the height H of the current encoding block, where M, N, W, and H are positive integers, and usually a power of 2, for example, 4, 8, 16, 32, 64, and 128. FIG. 12A shows a motion compensation unit of 4x4, and FIG. 12B illustrates an 8x8 motion compensation unit, where a center point of a corresponding motion compensation unit is represented by a triangle.

In an implementation of the embodiment of the present disclosure, the sub-block based inter prediction mode (sub-block motion prediction mode) includes one of the following modes: Advanced temporal motion vector prediction (ATMVP) mode,

Spatial-temporal motion vector prediction (STMVP) mode,

Affine prediction mode, and

Planar motion vector prediction mode.

In an implementation of the embodiment of the present disclosure, motion information of the first sub-block includes a motion vector and a reference index (a pair of motion vectors and a pair of reference indices) of the first sub-block and the reference block of the first sub-block is pointed by the motion vector in a reference picture corresponding to the reference index of the first sub-block;

motion information of the second sub-block includes a motion vector and a reference index (a pair of motion vectors and a pair of reference indices) of the second sub-block, and the reference block of the second sub-block is pointed by the motion vector in a reference picture corresponding to the reference index of the second sub-block.

Referring to FIG. 14, the sub-block edges includes horizontal sub-block boundaries on a 8x8 grid and/or vertical sub-block boundaries on a 8x8 grid; or the sub-block edges includes horizontal sub-block boundaries on a 4x4 grid and/or vertical sub-block boundaries on a 4x4 grid.

Referring to FIG. 12A or FIG. 12B, each sub-block has a block size being M×M or N×N or M×N and M or N being an even integer equal to 4 or larger than 4.

The invention is directed to efficient determination of sub-block edges for deblocking such that the sub-edges that require deblocking are determined more accurately. As a result visible blocking artifacts in the picture are removed and over-smoothing and blurring of the image is avoided.

If the current coding unit use sub-PU tools like Affine or ATMVP, basically a coding unit can use inter prediction. In inter prediction, there are several different tools which the coding unit may use. Affine and ATMVP are two sub-pu tools. Sub-pu tools means a give coding unit will further use smaller prediction units (sub-PUs) and motion compensation is done separately for each of the sub-PUs. For example, we have a coding unit of size 16 x 4, then, affine tool uses 2 sub-PUs of size 8 x 4 or 16 sub-PUs of size 4 x 4. Each of these sub-PUs or sub-blocks uses separate motion vectors.

Therefore for the current coding unit which uses Sub-PU tools, only a maximum of three samples are modified.

Generally, the deblocking filter process may include three steps: boundary/edge detection, filtering decision (Filter On/Off decision) , and filtering process for vertical and horizontal sub-block edges.

HEVC strong filter may be considered for the sub-block edge. Therefore a maximum of 3 samples on a side of the sub-block edge are modified in sub-block P, and a maximum of 3 samples on another side of the sub-block edge are modified in sub-block Q. Table 1 lists the filter coefficients.

Table 1

The details for determining whether the HEVC strong filter condition should be satisfied is shown in FIG. 15. FIG. 15 is a flowchart illustrating the deblocking filtering decisions for a sub-block boundary including the decisions between the strong and the normal filtering.

The method includes:

At first step 1500: checking whether the currently filtered sub-block edge is aligned with an 8 x 8 encoding sample grid. In the case that the currently filtered sub-block edge is aligned with an 8 x 8 encoding sample grid, the method proceeds to step 1501: checking whether the sub-block edge to be filtered is a boundary between prediction units or transform units. In the case that the sub-block edge to be filtered is a boundary between prediction units or transform units, the method proceeds to step 1502: checking whether a condition A is true.

Condition A is used to check if deblocking filtering is applied to a sub-block boundary or not, which is described in FIG. 11.

If this condition A is not met, or any of the checking in

steps

1500, 1501 and 1502 are not fulfilled, the method proceeds to step 1503 that determines no filtering is performed (step 1504) .

In step 1503, the method includes checking whether the sub-block size of any of the two sub-blocks, surrounding the edge to be filtered, is four. In the case that the sub-block size of any of the two sub-blocks, surrounding the edge to be filtered, is not four, the method proceeds to step 1505, and checks whether further conditions B, C, and D are met.

ondition B checks that there are no significant signal variations at the sides of the sub-block boundary. Condition C verifies that the signal on both sides is flat. Condition D ensures that the step between the sample values at the sides of the sub-block boundary is small.

If all of these conditions are true, in step 1506, a strong filtering is performed. If this is not the case, in step 1507 the method determines that a normal filtering is performed.

This solution enforces part of a deblocking flow chart, so that only one sample modification is performed.

In HEVC video coding standard, the boundary strength parameter bS [xDi] [yDj] , which is used in the determination of application of deblocking filtering is derived according to the following processing steps. The details are described as follows in the format of the specification.

Derivation process of boundary filtering strength

The variable bS [xDi] [yDj] is derived as follows:

- If the sample p0 or q0 is in the luma sub-block of a coding unit coded with intra prediction mode, bS [xDi] [yDj] is set equal to 2.

– Otherwise, if the block edge is also a transform block edge and the sample p0 or q0 is in a luma transform block which contains one or more non-zero transform coefficient levels, bS [xDi] [yDj] is set equal to 1.

– Otherwise, if the block edge is an internal sub-block edge and the sample p0 or q0 is in a luma transform block which not contains non-zero transform coefficient levels, and one or more the following conditions are true, bS [xDi] [yDj] is set equal to 1:

1. For the prediction of the luma prediction block containing the sample p0 different reference pictures or a different number of motion vectors are used than for the prediction of the luma prediction block containing the sample q0. NOTE 1 –The determination of whether the reference pictures used for the two luma prediction blocks are the same or different is based only on which pictures are referenced, without regard to whether a prediction is formed using an index into reference picture list 0 or an index into reference picture list 1, and also without regard to whether the index position within a reference picture list is different. NOTE 2 –The number of motion vectors that are used for the prediction of a luma prediction block with top-left luma sample covering (xPb, yPb) , is equal to PredFlagL0 [xPb] [yPb] + PredFlagL1 [xPb] [yPb] .

2. One motion vector is used to predict the luma prediction block containing the sample p0 and one motion vector is used to predict the luma prediction block containing the sample q0, and the absolute difference between the horizontal or vertical component of the motion vectors used is greater than or equal to 16 in units of 1/16 luma samples.

3. Two motion vectors and two different reference pictures are used to predict the luma prediction block containing the sample p0, two motion vectors for the same two reference pictures are used to predict the luma prediction block containing the sample q0 and the absolute difference between the horizontal or vertical component of the two motion vectors used in the prediction of the two luma prediction blocks for the same reference picture is greater than or equal to 16 in units of 1/16 luma samples.

4. Two motion vectors for the same reference picture are used to predict the luma prediction block containing the sample p0, two motion vectors for the same reference picture are used to predict the luma prediction block containing the sample q0 and both of the following conditions are true:

The absolute difference between the horizontal or vertical component of list 0 motion vectors used in the prediction of the two luma prediction blocks is greater than or equal to 16 in 1/16 luma samples, or the absolute difference between the horizontal or vertical component of the list 1 motion vectors used in the prediction of the two luma prediction blocks is greater than or equal to 16 in units of 1/16 luma samples.

The absolute difference between the horizontal or vertical component of list 0 motion vector used in the prediction of the luma prediction block containing the sample p0 and the list 1 motion vector used in the prediction of the luma prediction block containing the sample q0 is greater than or equal to 16 in units of 1/16 luma samples, or the absolute difference between the horizontal or vertical component of the list 1 motion vector used in the prediction of the luma prediction block containing the sample p0 and list 0 motion vector used in the prediction of the luma prediction block containing the sample q0 is greater than or equal to 16 in units of 1/16 luma samples.

– Otherwise, the variable bS [xDi] [yDj] is set equal to 0.

According to the invention, the determination whether the current block has residual data is used in the determination of the boundary strength parameter, which is in turn used in the determination of the deblocking filtering determination process.

In summary, the technical solutions of the present invention can ensure that deblocking operations can be performed and therefore improves subjective and objective quality of the video coding.

This approach is also shown in FIG. 16. FIG. 16 shows a flow diagram depicting a sub-block edge which divides the sub-blocks P and Q. Referring to FIG. 16, a current block 500 comprising two

sub-blocks

501, 502 is shown. A sub-block edge 504 divides the sub-blocks 501 and 502. According to the first embodiment of the invention, on opposite sides of the sub-block edge 504, two consecutive sample values are used as filter input values. The invention applies conditionally to sub-block types for application of a deblocking filter, the invention works for both vertical and horizontal edges.

FIG. 17 is a block diagram illustrating an exemplary deblocking filter apparatus 600 (also referred to as deblocking filter 600) according to the techniques described in this disclosure. In an example, the apparatus 600 may be corresponding to the loop filter 120 in FIG. 1. In another example, the apparatus 600 may be corresponding to the loop filter 220 in FIG. 2. The deblocking filter apparatus 600 may be configured to perform deblocking techniques in accordance with various examples described in the present disclosure. In general, either or both of loop filter 120 from FIG. 1 and loop filter 220 from FIG. 2 may include components substantially similar to those of deblocking filter 600. Other video coding devices, such as video encoders, video decoders, video encoder/decoders (CODECs) , and the like may also include components substantially similar to deblocking filter 600. Deblocking filter 600 may be implemented in hardware, software, or firmware, or any combination thereof. When implemented in software or firmware, corresponding hardware (such as one or more processors or processing units and memory for storing instructions for the software or firmware) may also be provided.

Referring to FIG. 17, deblocking filter 600 includes deblocking determination unit 604, support definitions unit 602 stored in memory, deblocking filtering unit 606, deblocking filter parameters 608 stored in memory, edge locating unit 603, and edge locations data structure 605. Any or all of the components of deblocking filter 600 may be functionally integrated. The components of deblocking filter 600 are illustrated separately only for purposes of illustration. In general, deblocking filter 600 receives data for decoded blocks, e.g., from a summation component that combines prediction data with residual data for the blocks. The data may further include an indication of how the blocks have been predicted. In the example described below, deblocking filter 600 is configured to receive data including a decoded video block associated with a LCU and a CU quadtree for the LCU, where the CU quadtree describes how the LCU is partitioned into CUs and prediction modes for PUs and TUs of leaf-node CUs.

Deblocking filter 600 may maintain edge locations data structure 605 in a memory disposed in deblocking filter 600, or in an external memory provided by a corresponding video coding device. In some embodiments, edge locating unit 603 may receive a CU quadtree corresponding to an LCU that indicates how the LCU is partitioned into CUs. Edge locating unit 603 may then analyze the CU quadtree to determine edges between decoded video blocks associated with TUs and PUs of CUs in the LCU that are candidates for deblocking.

Edge locations data structure 605 may comprise an array having a horizontal dimension, a vertical dimension, and a dimension representative of horizontal edges and vertical edges. In general, edges between video blocks may occur between two video blocks associated with smallest-sized CUs of the LCU, or TUs and PUs of the CUs. Assuming that the LCU has a size of N×N, and assuming that the smallest-sized CU of the LCU is of size M×M, the array may comprise a size of [N/M] × [N/M] ×2, where “2” represents the two possible directions of edges between CUs (horizontal and vertical) . For example, assuming that an LCU has 64×64 pixels and a 8×8 smallest-sized CU, the array may comprise [8] × [8] × [2] entries.

Each entry may generally correspond to a possible edge between two video blocks. Edges might not in fact exist at each of the positions within the LCU corresponding to each of the entries of edge locations data structure 605. Accordingly, values of the data structure may be initialized to false. In general, edge locating unit 603 may analyze the CU quadtree to determine locations of edges between two video blocks associated with TUs and PUs of CUs of the LCU and set corresponding values in edge locations data structure 605 to true.

In general, the entries of the array may describe whether a corresponding edge exists in the LCU as a candidate for deblocking. That is, when edge locating unit 603 determines that an edge between two neighboring video blocks associated with TUs and PUs of CUs of the LCU exists, edge locating unit 603 may set a value of the corresponding entry in edge locations data structure 605 to indicate that the edge exists (e.g., to a value of “true” ) .

Deblocking determination unit 604 generally determines whether, for two neighboring blocks, an edge between the two blocks should be deblocked. Deblocking determination unit 604 may determine locations of edges using edge locations data structure 605. When a value of edge locations data structure 605 has a Boolean value, deblocking determination unit 604 may determine that a “true” value indicates the presence of an edge, and a “false” value indicates that no edge is present, in some examples.

In general, deblocking determination unit 604 is configured with one or more deblocking determination functions. The functions may include a plurality of coefficients applied to lines of pixels that cross the edge between the blocks. For example, the functions may be applied to a line of eight pixels that is perpendicular to the edge, where four of the pixels are in one of the two blocks and the other four pixels are in the other of the two blocks. Support definitions 602 define support for the functions. In general, the “support” corresponds to the pixels to which the functions are applied.

Deblocking determination unit 604 may be configured to apply one or more deblocking determination functions to one or more sets of support, as defined by support definitions 602, to determine whether a particular edge between two blocks of video data should be deblocked. The dashed line originating from deblocking determination unit 604 represents data for blocks being output without being filtered. In cases where deblocking determination unit 604 determines that an edge between two blocks should not be filtered, deblocking filter 600 may output the data for the blocks without altering the data. That is, the data may bypass deblocking filtering unit 606. On the other hand, when deblocking determination unit 604 determines that an edge should be deblocked, deblocking determination unit 604 may cause deblocking filtering unit 606 to filter values for pixels near the edge in order to deblock the edge.

Deblocking filtering unit 606 retrieves definitions of deblocking filters from deblocking filter parameters 608 for edges to be deblocked, as indicated by deblocking determination unit 604. In general, filtering of an edge uses values of pixels from the neighborhood of a current edge to be deblocked. Therefore, both deblocking decision functions and deblocking filters may have a certain support region on both sides of an edge. By applying a deblocking filter to pixels in the neighborhood of an edge, deblocking filtering unit 606 may smooth the values of the pixels such that high frequency transitions near the edge are dampened. In this manner, application of deblocking filters to pixels near an edge may reduce blockiness artifacts near the edge.

FIG. 18 is a block diagram illustrating an exemplary deblocking method according to the techniques described in this disclosure (further details will be described below) . Referring to FIG. 18, the deblocking method is shown as including:

Step 1801: determining sub-block edges (sub-block boundaries) between sub-blocks of a current block which is predicted using sub-block based inter prediction mode (sub-block motion prediction mode) , the sub-block edges include a sub-block edge between a first sub-block P and a second sub-block Q;

Step 1802: determining whether the sub-block edge is to be filtered by applying a deblocking filter according to a first determination result and/or a second determination result. The first determination result indicates whether the current block has residual data or not, and the second determination result indicates whether a reference block of the first sub-block and a reference block of the second sub-block are continuous.

In an example embodiment, the first determination result is obtained by determining whether the current block has residual data or not, and the second determination result is obtained by determining whether a reference block of the first sub-block and a reference block of the second sub-block are continuous.

Step 1803: applying the deblocking filter to values of samples near the sub-block edge between the first sub-block P and the second sub-block Q, when it is determined the sub-block edge is to be filtered by applying the deblocking filter according to the first determination result and/or the second determination result.

It should be noted that the filter input values are consecutive values perpendicular to the sub-block edge beginning at the sub-block edge. Also, the filter output values are consecutive values perpendicular to the sub-block edge, beginning at the sub-block edge. Each sub-block of the current block has the own motion information, inter prediction (motion compensation) is performed based on the motion information of each sub-block to obtain the predictor (prediction block) of said each sub-block.

The sub-block based inter prediction mode (sub-block motion prediction mode) includes any one of the following modes:

Advanced temporal motion vector prediction (ATMVP) mode,

Spatial-temporal motion vector prediction (STMVP) mode,

Affine prediction mode, and

Planar motion vector prediction mode.

In an embodiment, the steps of determining whether the sub-block edge is to be filtered by applying a deblocking filter according to a first determination result and/or a second determination result includes:

it is determined that the sub-block edge is to be filtered by applying a deblocking filter, when the first determination result indicates no residual data of the current block and the second determination result indicates the reference block of the first sub-block and the reference block of the second sub-block are discontinuous; or

it is determined that the sub-block edge is not to be filtered by applying a deblocking filter, when the first determination result indicates no residual data of the current block and the second determination result indicates the reference block of the first sub-block and the reference block of the second sub-block are continuous; or

it is determined that the sub-block edge is not to be filtered by applying a deblocking filter, when the first determination result indicates residual data of the current block.

wherein motion information of the first sub-block includes a motion vector and a reference index (a pair of motion vectors and a pair of reference indices) of the first sub-block and the reference block of the first sub-block is pointed by the motion vector in a reference picture corresponding to the reference index of the first sub-block;

The second determination result indicates a reference block of the first sub-block and a reference block of the second sub-block are discontinuous when a reference index of the first sub-block and a reference index of the second sub-block are different; or

the second determination result indicates a reference block of the first sub-block and a reference block of the second sub-block are discontinuous when a reference index of the first sub-block and a reference index of the second sub-block are same and the motion vector difference between a motion vector of the first sub-block and a motion vector of the second sub-block is larger than a threshold (predefined pixels) ; or

the second determination result indicates a reference block of the first sub-block and a reference block of the second sub-block are discontinuous when the motion vector difference between a motion vector of the first sub-block and a motion vector of the second sub-block is larger than a threshold.

The first determination result indicates no residual data of the current block when a first flag (such as a coded_block_flag) parsed from a bitstream is equal to a first value (such as 0) . The first determination result indicates residual data of the current block when a first flag (a coded_block_flag) parsed from a bitstream is equal to a second value (such as 1) . The sub-block edges comprises horizontal sub-block boundaries on a 8*8 grid and/or vertical sub-block boundaries on a 8*8 grid; or the sub-block edges comprises horizontal sub-block boundaries on a 4*4 grid and/or vertical sub-block boundaries on a 4*4 grid. Each sub-block has a block size being M×M or N×N or M×N and M or N being an even integer equal to 4 or larger than 4.

FIG. 19 is a simplified block diagram of an apparatus 1300 that may be used as either or both of the source device 310 and the destination device 320 from FIG. 3 according to an exemplary embodiment. Apparatus 1300 can implement techniques of this present application. Apparatus 1300 can be in the form of a computing system including multiple computing devices, or in the form of a single computing device, for example, a mobile phone, a tablet computer, a laptop computer, a notebook computer, a desktop computer, and the like.

Processor 1302 of apparatus 1300 can be a central processing unit. Alternatively, processor 1302 can be any other type of device, or multiple devices, capable of manipulating or processing information now-existing or hereafter developed. Although the disclosed implementations can be practiced with a single processor as shown, e.g., processor 1302, advantages in speed and efficiency can be achieved using more than one processor.

Memory 1304 in the apparatus 1300 can be a read only memory (ROM) device or a random access memory (RAM) device in an implementation. Any other suitable type of storage device can be used as memory 1304. Memory 1304 may be used to store code and/or data 1306 that is accessed by processor 1302 using bus 1312. Memory 1304 can further be used to store operating system 1308 and application programs 1310. Application programs 1310 may include at least one program that permits processor 1302 to perform the methods described here. For example, application programs 1310 can include applications 1 through N, and further include a video coding application that performs the methods described here. Apparatus 1300 can also include additional memory in the form of secondary storage 1314, which can, for example, be a memory card used with a mobile computing device. Because the video communication sessions may contain a significant amount of information, they can be stored in whole or in part in storage 1314 and loaded into memory 1304 as needed for processing.

Apparatus 1300 can also include one or more output devices, such as display 1318. Display 1318 may be, in one example, a touch sensitive display that combines a display with a touch sensitive element operable to sense touch inputs. Display 1318 can be coupled to processor 1302 via bus 1312. Other output devices that permit a user to program or otherwise use apparatus 1300 can be provided in addition to or as an alternative to display 1318. When the output device is or includes a display, the display can be implemented in various ways, including by a liquid crystal display (LCD) , a cathode-ray tube (CRT) display, a plasma display or light emitting diode (LED) display, such as an organic LED (OLED) display.

Apparatus 1300 can also include or be in communication with image-sensing device 1320, for example a camera, or any other image-sensing device 1320 now existing or hereafter developed that can sense an image such as the image of a user operating apparatus 1300. Image-sensing device 1320 can be positioned such that it is directed toward the user operating apparatus 1300. In an example, the position and optical axis of image-sensing device 1320 can be configured such that the field of vision includes an area that is directly adjacent to display 1318 and from which display 1318 is visible.

Apparatus 1300 can also include or be in communication with sound-sensing device 1322, for example a microphone, or any other sound-sensing device now existing or hereafter developed that can sense sounds near apparatus 1300. Sound-sensing device 1322 can be positioned such that it is directed toward the user operating apparatus 1300 and can be configured to receive sounds, for example, speech or other utterances, made by the user while the user operates apparatus 1300.

Although FIG. 19 depicts processor 1302 and memory 1304 of apparatus 1300 as being integrated into a single device, other configurations can be utilized. The operations of processor 1302 can be distributed across multiple machines (each machine having one or more of processors) that can be coupled directly or across a local area or other network. Memory 1304 can be distributed across multiple machines such as a network-based memory or memory in multiple machines performing the operations of apparatus 1300. Although depicted here as a single bus, bus 1312 of apparatus 1300 may comprise multiple buses. Further, secondary storage 1314 can be directly coupled to the other components of apparatus 1300 or can be accessed via a network and can comprise a single integrated unit such as a memory card or multiple units such as multiple memory cards. Apparatus 1300 can thus be implemented in a wide variety of configurations.

FIG. 20 is a schematic diagram of an example coding device 1400 for video coding according to an embodiment of the disclosure. The coding device 1400 is suitable for implementing the disclosed embodiments as described herein. In an embodiment, the coding device 1400 may be a decoder such as video decoder 200 of FIG. 2 or an encoder such as video encoder 100 of FIG. 1. In an embodiment, the coding device 1400 may be one or more components of the video decoder 200 of FIG. 2 or the video encoder 100 of FIG. 1 as described above.

The coding device 1400 comprises ingress ports 1420 and receiver units (Rx) 1410 for receiving data; a processor, logic unit, or central processing unit (CPU) 1430 to process the data; transmitter units (Tx) 1440 and egress ports 1450 for transmitting the data; a memory 1460 for storing the data. The coding device 1400 may also comprise optical-to-electrical (OE) components and electrical-to-optical (EO) components coupled to the ingress ports 1420, the receiver units 1410, the transmitter units 1440, and the egress ports 1450 for egress or ingress of optical or electrical signals. The coding device 1400 may also include wireless transmitters and/or receivers in some examples.

The processor 1430 is implemented by hardware and software. The processor 1430 may be implemented as one or more CPU chips, cores (e.g., as a multi-core processor) , field-programmable gate arrays (FPGAs) , application specific integrated circuits (ASICs) , and digital signal processors (DSPs) . The processor 1430 is in communication with the ingress ports 1420, receiver units 1410, transmitter units 1440, egress ports 1450, and memory 1460. The processor 1430 comprises a coding module 1414. The coding module 1414 implements the disclosed embodiments described above. For instance, the coding module 1414 implements, processes, prepares, or provides the various coding operations. The inclusion of the coding module 1414 therefore provides a substantial improvement to the functionality of the computing device 1400 and effects a transformation of the computing device 1400 to a different state. Alternatively, the coding module 1414 is implemented as instructions stored in the memory 1460 and executed by the processor 1430 (e.g., as a computer program product stored on a non-transitory medium) .

The memory 1460 comprises one or more disks, tape drives, and solid-state drives and may be used as an over-flow data storage device, to store programs when such programs are selected for execution, and to store instructions and data that are read during program execution. The memory 1460 may be volatile and/or non-volatile and may be read-only memory (ROM) , random access memory (RAM) , ternary content-addressable memory (TCAM) , and/or static random-access memory (SRAM) . The computing device 1400 may also input/output (I/O) device for interacting with an end user. For example, the computing device 1400 may include a display, such as a monitor, for visual output, speakers for audio output, and a keyboard/mouse/trackball, etc. for user input.

Further embodiments of the present invention are provided in the following. The details of the following embodiments are not repeated again and have been described in conjunction with various embodiments herein.

According to other aspects of the invention, a deblocking method for use in an image encoding and/or an image decoding may include:

determining sub-block edges (sub-block boundaries) between sub-blocks of a current block which is predicted using sub-block based inter prediction mode (sub-block motion prediction mode) , the sub-block edges comprises a sub-block edge between a first sub-block P and a second sub-block Q;

determining whether the sub-block edge is to be filtered by applying a deblocking filter according to a first determination result and/or a second determination result; wherein a first determination result represents whether the current block has residual data or not, and a second determination result represents whether a reference block of the first sub-block and a reference block of the second sub-block are continuous; and

applying the deblocking filter to values of samples near the sub-block edge between the first sub-block P and the second sub-block Q, when it is determined the sub-block edge is to be filtered by applying the deblocking filter according to the first determination result and/or the second determination result.

According to one embodiment, each sub-block of the current block has its own motion information, inter prediction (motion compensation) is performed based on the motion information of each sub-block to obtain the predictor (prediction block) of said each sub-block.

According to one embodiment, the sub-block based inter prediction mode (sub-block motion prediction mode) includes one of the following modes: advanced temporal motion vector prediction (ATMVP) mode, spatial-temporal motion vector prediction (STMVP) mode, affine prediction mode, and planar motion vector prediction mode.

According to one embodiment, the determining whether the sub-block edge is to be filtered by applying a deblocking filter according to a first determination result and/or a second determination result includes:

According to one embodiment, motion information of the first sub-block includes a motion vector and a reference index (a pair of motion vectors and a pair of reference indices) of the first sub-block and the reference block of the first sub-block is pointed by the motion vector in a reference picture corresponding to the reference index of the first sub-block. Motion information of the second sub-block includes a motion vector and a reference index (a pair of motion vectors and a pair of reference indices) of the second sub-block, and the reference block of the second sub-block is pointed by the motion vector in a reference picture corresponding to the reference index of the second sub-block.

According to one embodiment, the second determination result indicates a reference block of the first sub-block and a reference block of the second sub-block are discontinuous when a reference index of the first sub-block and a reference index of the second sub-block are different; or

According to one embodiment, the first determination result indicates no residual data of the current block when a first flag (such as a coded_block_flag) parsed from a bitstream is equal to a first value (such as 0) ; the first determination result indicates residual data of the current block when a first flag (a coded_block_flag) parsed from a bitstream is equal to a second value (such as 1) .

According to one embodiment, the sub-block edges comprises horizontal sub-block boundaries on a 8*8 grid and/or vertical sub-block boundaries on a 8*8 grid; or the sub-block edges comprises horizontal sub-block boundaries on a 4*4 grid and/or vertical sub-block boundaries on a 4*4 grid.

According to one embodiment, each sub-block has a block size being M×M or N×N and M or N being an even integer equal to 4 or larger than 4.

According to other aspects of the invention, a deblocking filter apparatus for use in an image encoder and/or an image decoder includes:

an edge locating unit, configured to determine sub-block edges (sub-block boundaries) between sub-blocks of a current block which is predicted using sub-block based inter prediction mode (sub-block motion prediction mode) , the sub-block edges comprises a sub-block edge between a first sub-block and a second sub-block;

a deblocking determination unit, configured to determine whether the sub-block edge is to be filtered by applying a deblocking filter according to a first determination result and/or a second determination result; wherein a first determination result represents whether the current block has residual data or not, and a second determination result represents whether a reference block of the first sub-block and a reference block of the second sub-block are continuous; and a deblocking filtering unit, configured to apply the deblocking filter to values of samples near the sub-block edge between the first sub-block P and the second sub-block Q, when it is determined the sub-block edge is to be filtered by applying the deblocking filter according to the first determination result and/or the second determination result.

According to one embodiment, each sub-block of the current block has the own motion information, inter prediction (motion compensation) is performed based on the motion information of each sub-block to obtain the predictor (prediction block) of said each sub-block.

According to one embodiment, the deblocking determination unit is configured to: determine that the sub-block edge is to be filtered by applying a deblocking filter, when the first determination result indicates no residual data of the current block and the second determination result indicates the reference block of the first sub-block and the reference block of the second sub-block are discontinuous; or

determine the sub-block edge is not to be filtered by applying a deblocking filter, when the first determination result indicates no residual data of the current block and the second determination result indicates the reference block of the first sub-block and the reference block of the second sub-block are continuous; or

determine the sub-block edge is not to be filtered by applying a deblocking filter, when the first determination result indicates residual data of the current block.

According to one embodiment, the first determination result indicates no residual data of the current block when a first flag (such as a coded_block_flag) parsed from a bitstream is equal to a first value (such as 0) . The first determination result indicates residual data of the current block when a first flag (a coded_block_flag) parsed from a bitstream is equal to a second value (such as 1) .

According to one embodiment, the sub-block edges includes horizontal sub-block boundaries on a 8*8 grid and/or vertical sub-block boundaries on a 8*8 grid. Alternatively, the sub-block edges includes horizontal sub-block boundaries on a 4*4 grid and/or vertical sub-block boundaries on a 4*4 grid.

The invention has been described in conjunction with various embodiments herein. However, other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure and the appended claims. In the claims, the word “comprising “does not exclude other elements or steps and the indefinite article “a” or “an” does not exclude a plurality. A single processor or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in usually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. A computer program may be stored/distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the internet or other wired or wireless communication systems.

Wherever embodiments and the description refer to the term “memory” , the term “memory” shall be understood and/or shall comprise [listing of all possible memories] a magnetic disk, an optical disc, a read-only memory (Read-Only Memory, ROM) , or a random access memory (Random Access Memory, RAM) , …, unless explicitly stated otherwise.

Wherever embodiments and the description refer to the term “network” , the term “network” shall be understood and/or shall comprise [listing of all possible memories] …, unless explicitly stated otherwise.

The person skilled in the art will understand that the “blocks” ( “units” ) of the various figures (method and apparatus) represent or describe functionalities of embodiments of the invention (rather than necessarily individual “units” in hardware or software) and thus describe equally functions or features of apparatus embodiments as well as method embodiments (unit =step) .

The terminology of “units” is merely used for illustrative purposes of the functionality of embodiments of the encoder/decoder and are not intended to limiting the disclosure.

In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus, and method may be implemented in other manners. For example, the described apparatus embodiment is merely exemplary. For example, the unit division is merely logical function division and may be other division in actual implementation. For example, a plurality of units or components may be combined or integrated into another system, or some features may be ignored or not performed. In addition, the displayed or discussed mutual couplings or direct couplings or communication connections may be implemented by using some interfaces. The indirect couplings or communication connections between the apparatuses or units may be implemented in electronic, mechanical, or other forms.

The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one position, or may be distributed on a plurality of network units. Some or all of the units may be selected according to actual needs to achieve the objectives of the solutions of the embodiments.

In addition, functional units in the embodiments of the present invention may be integrated into one processing unit, or each of the units may exist alone physically, or two or more units are integrated into one unit.

Embodiments of the invention may further comprise an apparatus, e.g. encoder and/or decoder, which comprises a processing circuitry configured to perform any of the methods and/or processes described herein.

Embodiments may be implemented as hardware, firmware, software or any combination thereof. For example, the functionality of the encoder/encoding or decoder/decoding may be performed by a processing circuitry with or without firmware or software, e.g. a processor, a microcontroller, a digital signal processor (DSP) , a field programmable gate array (FPGA) , an application-specific integrated circuit (ASIC) , or the like.

The functionality of the encoder 100 (and corresponding encoding method 100) and/or decoder 200 (and corresponding decoding method 200) may be implemented by program instructions stored on a computer readable medium. The program instructions, when executed, cause a processing circuitry, computer, processor or the like, to perform the steps of the encoding and/or decoding methods. The computer readable medium can be any medium, including non-transitory storage media, on which the program is stored such as a Bluray disc, DVD, CD, USB (flash) drive, hard disc, server storage available via a network, etc.

An embodiment of the invention comprises or is a computer program comprising program code for performing any of the methods described herein, when executed on a computer.

An embodiment of the invention comprises or is a computer readable medium comprising a program code that, when executed by a processor, causes a computer system to perform any of the methods described herein.

Following is an explanation of the applications of the encoding method as well as the decoding method as shown in the above-mentioned embodiments, and a system using them.

FIG. 21 is a block diagram showing a content supply system 3100 for realizing content distribution service. This content supply system 3100 includes capture device 3102, terminal device 3106, and optionally includes display 3126. The capture device 3102 communicates with the terminal device 3106 over communication link 3104. The communication link may include the communication channel 13 described above. The communication link 3104 includes but not limited to WIFI, Ethernet, Cable, wireless (3G/4G/5G) , USB, or any kind of combination thereof, or the like.

The capture device 3102 generates data, and may encode the data by the encoding method as shown in the above embodiments. Alternatively, the capture device 3102 may distribute the data to a streaming server (not shown in the Figures) , and the server encodes the data and transmits the encoded data to the terminal device 3106. The capture device 3102 includes but not limited to camera, smart phone or Pad, computer or laptop, video conference system, PDA, vehicle mounted device, or a combination of any of them, or the like. For example, the capture device 3102 may include the source device 12 as described above. When the data includes video, the video encoder 20 included in the capture device 3102 may actually perform video encoding processing. When the data includes audio (i.e., voice) , an audio encoder included in the capture device 3102 may actually perform audio encoding processing. For some practical scenarios, the capture device 3102 distributes the encoded video and audio data by multiplexing them together. For other practical scenarios, for example in the video conference system, the encoded audio data and the encoded video data are not multiplexed. Capture device 3102 distributes the encoded audio data and the encoded video data to the terminal device 3106 separately.

In the content supply system 3100, the terminal device 310 receives and reproduces the encoded data. The terminal device 3106 could be a device with data receiving and recovering capability, such as smart phone or Pad 3108, computer or laptop 3110, network video recorder (NVR) /digital video recorder (DVR) 3112, TV 3114, set top box (STB) 3116, video conference system 3118, video surveillance system 3120, personal digital assistant (PDA) 3122, vehicle mounted device 3124, or a combination of any of them, or the like capable of decoding the above-mentioned encoded data. For example, the terminal device 3106 may include the destination device 14 as described above. When the encoded data includes video, the video decoder 30 included in the terminal device is prioritized to perform video decoding. When the encoded data includes audio, an audio decoder included in the terminal device is prioritized to perform audio decoding processing.

For a terminal device with its display, for example, smart phone or Pad 3108, computer or laptop 3110, network video recorder (NVR) /digital video recorder (DVR) 3112, TV 3114, personal digital assistant (PDA) 3122, or vehicle mounted device 3124, the terminal device can feed the decoded data to its display. For a terminal device equipped with no display, for example, STB 3116, video conference system 3118, or video surveillance system 3120, an external display 3126 is contacted therein to receive and show the decoded data.

When each device in this system performs encoding or decoding, the picture encoding device or the picture decoding device, as shown in the above-mentioned embodiments, can be used.

FIG. 22 is a diagram showing a structure of an example of the terminal device 3106. After the terminal device 3106 receives stream from the capture device 3102, the protocol proceeding unit 3202 analyzes the transmission protocol of the stream. The protocol includes but not limited to Real Time Streaming Protocol (RTSP) , Hyper Text Transfer Protocol (HTTP) , HTTP Live streaming protocol (HLS) , MPEG-DASH, Real-time Transport protocol (RTP) , Real Time Messaging Protocol (RTMP) , or any kind of combination thereof, or the like.

After the protocol proceeding unit 3202 processes the stream, stream file is generated. The file is outputted to a demultiplexing unit 3204. The demultiplexing unit 3204 can separate the multiplexed data into the encoded audio data and the encoded video data. As described above, for some practical scenarios, for example in the video conference system, the encoded audio data and the encoded video data are not multiplexed. In this situation, the encoded data is transmitted to video decoder 3206 and audio decoder 3208 without through the demultiplexing unit 3204.

Via the demultiplexing processing, video elementary stream (ES) , audio ES, and optionally subtitle are generated. The video decoder 3206, which includes the video decoder 30 as explained in the above mentioned embodiments, decodes the video ES by the decoding method as shown in the above-mentioned embodiments to generate video frame, and feeds this data to the synchronous unit 3212. The audio decoder 3208, decodes the audio ES to generate audio frame, and feeds this data to the synchronous unit 3212. Alternatively, the video frame may store in a buffer (not shown in FIG. Y) before feeding it to the synchronous unit 3212. Similarly, the audio frame may store in a buffer (not shown in FIG. Y) before feeding it to the synchronous unit 3212.

The synchronous unit 3212 synchronizes the video frame and the audio frame, and supplies the video/audio to a video/audio display 3214. For example, the synchronous unit 3212 synchronizes the presentation of the video and audio information. Information may code in the syntax using time stamps concerning the presentation of coded audio and visual data and time stamps concerning the delivery of the data stream itself.

If subtitle is included in the stream, the subtitle decoder 3210 decodes the subtitle, and synchronizes it with the video frame and the audio frame, and supplies the video/audio/subtitle to a video/audio/subtitle display 3216.

The present invention is not limited to the above-mentioned system, and either the picture encoding device or the picture decoding device in the above-mentioned embodiments can be incorporated into other system, for example, a car system.

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.

While several embodiments have been provided in the present disclosure, it should be understood that the disclosed systems and methods might be embodied in many other specific forms without departing from the spirit or scope of the present disclosure. The present examples are to be considered as illustrative and not restrictive, and the intention is not to be limited to the details given herein. For example, the various elements or components may be combined or integrated in another system or certain features may be omitted, or not implemented.

In addition, techniques, systems, subsystems, and methods described and illustrated in the various embodiments as discrete or separate may be combined or integrated with other systems, modules, techniques, or methods without departing from the scope of the present disclosure. Other items shown or discussed as coupled or directly coupled or communicating with each other may be indirectly coupled or communicating through some interface, device, or intermediate component whether electrically, mechanically, or otherwise. Other examples of changes, substitutions, and alterations are ascertainable by one skilled in the art and could be made without departing from the spirit and scope disclosed herein.

Claims

A deblocking method for use in an image encoding and/or an image decoding, the method comprising:

determining sub-block edges between sub-blocks of a current block which is predicted using a sub-block inter prediction mode, the sub-block edges comprising a sub-block edge between a first sub-block and a second sub-block;

determining whether the current block has residual data or not, and/or whether a reference block of the first sub-block and a reference block of the second sub-block are continuous; and

applying a deblocking filter to values of samples in a vicinity of a sub-block edge between a first sub-block and a second sub-block, when the current block has no residual data and the reference block of the first sub-block and the reference block of the second sub-block are discontinuous.
The method of claim 1, wherein determining whether the current block has residual data or not comprises:

determining that the current block has no residual data when a value of a first flag parsed from a bitstream is equal to a first value; or

determining that the current block has residual data when the value of the first flag parsed from the bitstream is equal to a second value.
The method of any one of claims 1 and 2, wherein determining whether the reference block of the first sub-block and the reference block of the second sub-block are continuous comprises:

determining whether a reference index of the first sub-block and a reference index of the second sub-block are different:

when the reference index of the first sub-block and the reference index of the second sub-block are different, determining that the reference block of the first sub-block and the reference block of the second sub-block are discontinuous; or

when the reference index of the first sub-block and the reference index of the second sub-block are not different, and a motion vector difference between a motion vector of the first sub-block and a motion vector of the second sub-block is larger than a threshold, determining that the reference block of the first sub-block and the reference block of the second sub-block are discontinuous; or

when the motion vector difference between the motion vector of the first sub-block and the motion vector of the second sub-block is larger than the threshold, determining that the reference block of the first sub-block and the reference block of the second sub-block are discontinuous.
The method of any one of claims 1, 2, and 3, wherein each of the sub-blocks of the current block has its own motion information, the method comprising: performing inter prediction based on the motion information of each of the sub-blocks to obtain a predictor associated with each of the sub-blocks.
The method of any one of claims 1, 2, 3, and 4, wherein the sub-block inter prediction mode comprises one of the following modes:

advanced temporal motion vector prediction (ATMVP) mode;

spatial-temporal motion vector prediction (STMVP) mode;

affine prediction mode; and

planar motion vector prediction mode.
The method of any one of claims 1, 2, 3, 4, and 5, wherein:

the first sub-block comprises motion information including a motion vector and a reference index of the first sub-block, and the reference block of the first sub-block is pointed by the motion vector in a reference picture corresponding to the reference index of the first sub-block;

the second sub-block comprises motion information including a motion vector and a reference index of the second sub-block, and the reference block of the second sub-block is pointed by the motion vector in a reference picture corresponding to the reference index of the second sub-block.
The method of any one of claims 1, 2, 3, 4, 5, and 6, wherein the sub-block edges comprise horizontal sub-block boundaries on a 8*8 grid and/or vertical sub-block boundaries on a 8*8 grid; or

the sub-block edges comprise horizontal sub-block boundaries on a 4*4 grid and/or vertical sub-block boundaries on a 4*4 grid.
The method of any one of claims 1, 2, 3, 4, 5, 6, and 7, wherein each of the sub-blocks has a block size being M×M or N×N, M and N being an even integer equal to or greater than 4.
A deblocking filter apparatus for use in an image encoder and/or an image decoder, comprising:

an edge locating unit configured to determine sub-block edges between sub-blocks of a current block which is predicted using a sub-block inter prediction mode, the sub-block edges comprising a sub-block edge between a first sub-block and a second sub-block;

a deblocking determination unit configured to determine whether the current block has residual data or not, and/or whether a reference block of the first sub-block and a reference block of the second sub-block are continuous; and

a deblocking filtering unit configured to apply a deblocking filter to values of samples in a vicinity of the sub-block edge between the first sub-block and the second sub-block, when the current block has no residual data and the reference block of the first sub-block and the reference block of the second sub-block are discontinuous.
The apparatus of claim 9, wherein the deblocking determination unit is configured to determine that, when a value of a first flag parsed from a bitstream is equal to a first value, the current block has no residual data; or

when the value of the first flag parsed from the bitstream is equal to a second value different from the first value, the current block has residual data.
The apparatus of any one of the preceding of claims, wherein the deblocking determination unit is configured to determine that, when a reference index of the first sub-block and a reference index of the second sub-block are different, a reference block of the first sub-block and a reference block of the second sub-block are discontinuous; or

when the reference index of the first sub-block and the reference index of the second sub-block are the same, and a motion vector difference between a motion vector of the first sub-block and a motion vector of the second sub-block is larger than a threshold, a reference block of the first sub-block and a reference block of the second sub-block are discontinuous; or

when the motion vector difference between the motion vector of the first sub-block and the motion vector of the second sub-block is larger than the threshold, the reference block of the first sub-block and the reference block of the second sub-block are discontinuous.
The apparatus of any one of the preceding of claims, wherein each of the sub-blocks of the current block has its own motion information, the deblocking determination unit is configured to perform inter prediction based on the motion information of each of the sub-blocks to obtain a predictor corresponding to each of the sub-blocks.
The apparatus of any one of the preceding of claims, wherein the sub-block inter prediction mode comprises one of the following modes:

advanced temporal motion vector prediction (ATMVP) mode;

spatial-temporal motion vector prediction (STMVP) mode;

affine prediction mode; and

planar motion vector prediction mode.
The apparatus of any one of the preceding of claims , wherein the first sub-block comprises motion information including a motion vector and a reference index of the first sub-block, and the reference block of the first sub-block is pointed by the motion vector in a reference picture corresponding to the reference index of the first sub-block; and

the second sub-block comprises motion information including a motion vector and a reference index of the second sub-block, and the reference block of the second sub-block is pointed by the motion vector in a reference picture corresponding to the reference index of the second sub-block.
The apparatus of any one of the preceding of claims, wherein the sub-block edges comprise horizontal sub-block boundaries on a 8*8 grid and/or vertical sub-block boundaries on a 8*8 grid; or

the sub-block edges comprise horizontal sub-block boundaries on a 4*4 grid and/or vertical sub-block boundaries on a 4*4 grid.
The apparatus of any one of the preceding of claims, wherein each of the sub-blocks has a block size being M×M or N×N, M and N being an even integer equal to or larger than 4.
A video encoding apparatus (100) for encoding a picture of a video stream, comprising:

a reconstruction unit (114) configured to reconstruct the picture; and

a filter apparatus (120) according to any one of claims 9, 11 to 16 for processing the reconstructed picture into a filtered reconstructed picture.
A video decoding apparatus (200) for decoding a picture of an encoded video stream (303) , comprising:

a reconstruction unit (214) configured to reconstruct the picture; and

a loop filter apparatus (220) according to any one of claims 9 to 16 for processing the reconstructed picture into a filtered reconstructed picture.
An encoding method for encoding an image, comprising a deblocking method of any one of claims 1, 3 to 8.
A decoding method for decoding an image, comprising a deblocking method of any one of claims 1 to 8.
A non-transitory computer-readable media storing computer instructions that when executed by one or more processors, cause the one or more processors to perform the method according to any of the claims 1 to 8.