Method and apparatus for deriving intra prediction mode

Thisreissueapplicationis for a reissue of U.S. Pat. No. 10,771,781, which issued on Sep. 8, 2020, from application Ser. No. 16/299,661 filed on Mar. 12, 2019, andclaims the benefit of Korean Patent Application Nos.10-2018-0028839, filed Mar. 12, 2018 and 10-2019-0026904, filed Mar. 8, 2019,10-2018-0028839 filed on Mar. 12, 2018, and 10-2019-0026904 filed on Mar. 8, 2019,which are hereby incorporated by reference in their entirety into this application.

The following embodiments relate generally to a video decoding method and apparatus and a video encoding method and apparatus, and more particularly, to a decoding method and apparatus and an encoding method and apparatus for deriving an intra prediction mode.

With the continuous development of the information and communication industries, broadcasting services supporting High-Definition (HD) resolution have been popularized all over the world. Through this popularization, a large number of users have become accustomed to high-resolution and high-definition images and/or videos.

To satisfy users' demand for high definition, many institutions have accelerated the development of next-generation imaging devices. Users' interest in UHD TVs, having resolution that is more than four times as high as that of Full HD (FHD) TVs, as well as High-Definition TVs (HDTV) and FHD TVs, has increased. As interest therein has increased, image encoding/decoding technology for images having higher resolution and higher definition is continually required.

An image encoding/decoding apparatus and method may use inter prediction technology, intra prediction technology, entropy-coding technology, etc. so as to perform encoding/decoding on a high-resolution and high-definition image. Inter prediction technology may be technology for predicting the value of a pixel included in a target picture using temporally previous pictures and/or temporally subsequent pictures. Intra prediction technology may be technology for predicting the value of a pixel included in a target picture using information about pixels in the target picture. Entropy-coding technology may be technology for assigning short code words to frequently occurring symbols and assigning long code words to rarely occurring symbols.

Various inter prediction technologies and intra prediction technologies have been developed for more accurate prediction.

An embodiment is intended to provide an encoding apparatus and method and a decoding apparatus and method, which perform intra prediction for a target block using a Most Probable Mode (MPM) list.

An embodiment is intended to provide an encoding apparatus and method and a decoding apparatus and method, which configure an MPM list using a temporal neighbor block of a target block.

An embodiment is intended to provide an encoding apparatus and method and a decoding apparatus and method, which configure an MPM list using the directionality of a neighbor block of a target block.

In accordance with an aspect, there is provided a decoding method, including deriving an intra prediction mode of a target block; and performing intra prediction for the target block that uses the derived intra prediction mode.

The intra prediction mode of the target block may be derived based on an intra prediction mode of a temporal neighbor block of the target block.

The temporal neighbor block may be determined based on a spatial neighbor block of the target block.

The temporal neighbor block may be determined based on motion information of a spatial neighbor block of the target block.

The intra prediction mode of the target block may be derived based on a block spatially adjacent to a temporal neighbor block of the target block.

The intra prediction mode of the target block may be derived based on a neighbor block of the target block.

The neighbor block may be selected based on a type of a target slice including the target block.

The intra prediction mode of the target block may be derived based on directionality of a neighbor block of the target block.

The intra prediction mode of the target block may be derived using a Most Probable Mode (MPM).

A number of candidate modes in an MPM list may be determined based on a coding parameter related to the target block.

The number of candidate modes may be determined based on at least one of a type of a target slice including the target block, a color component of the target block, a block size of the target block, and a shape of the target block.

The candidate modes may be determined based on an intra prediction mode derived for a neighbor block of the target block.

The neighbor block may be a block reconstructed via inter prediction.

One or more of intra prediction modes of neighbor blocks of the target block and one or more predefined intra prediction modes may be set as the candidate modes in the MPM list in a specific order.

Multiple intra prediction modes of multiple reference blocks may be used as the candidate modes in the MPM list.

The multiple reference blocks may be present in one or more reference pictures that are selected from among multiple reference pictures in ascending order of distance from a target picture including the target block.

The MPM list may be configured using an intra prediction mode of a reference block and an intra prediction mode of a spatial neighbor block of the reference block.

The MPM list may be configured based on an intra prediction mode of a spatial neighbor block of the target block.

When an intra prediction mode of the spatial neighbor block is not present, an intra prediction mode of a reference block may replace the intra prediction mode of the spatial neighbor block.

A location of the reference block in a reference picture may be identical to a location of the spatial neighbor block in a target picture.

The target picture may include the target block.

The MPM list may be configured based on an intra prediction mode of a spatial neighbor block of the target block.

When an intra prediction mode of the spatial neighbor block is not present, an intra prediction mode of a reference block may replace the intra prediction mode of the spatial neighbor block.

The reference block may be a block corresponding to motion information of the spatial neighbor block.

An intra prediction mode to be added to the MPM list may be generated based on an intra prediction mode included in the MPM list.

The MPM list may be configured based on an intra prediction mode of a neighbor block of the target block.

The intra prediction mode of the neighbor block may be derived using directionality of the neighbor block.

The MPM list may be configured for the target block.

The MPM list may be used for each of multiple sub-blocks generated by dividing the target block.

In accordance with another aspect, there is provided an encoding method, including deriving an intra prediction mode of a target block; and performing intra prediction for the target block that uses the derived intra prediction intra prediction mode.

In accordance with a further aspect, there is provided an intra prediction method, including deriving an intra prediction mode of a target block; and performing intra prediction for the target block that uses the derived intra prediction mode.

The present invention may be variously changed, and may have various embodiments, and specific embodiments will be described in detail below with reference to the attached drawings. However, it should be understood that those embodiments are not intended to limit the present invention to specific disclosure forms, and that they include all changes, equivalents or modifications included in the spirit and scope of the present invention.

Detailed descriptions of the following exemplary embodiments will be made with reference to the attached drawings illustrating specific embodiments. These embodiments are described so that those having ordinary knowledge in the technical field to which the present disclosure pertains can easily practice the embodiments. It should be noted that the various embodiments are different from each other, but do not need to be mutually exclusive of each other. For example, specific shapes, structures, and characteristics described here may be implemented as other embodiments without departing from the spirit and scope of the embodiments in relation to an embodiment. Further, it should be understood that the locations or arrangement of individual components in each disclosed embodiment can be changed without departing from the spirit and scope of the embodiments. Therefore, the accompanying detailed description is not intended to restrict the scope of the disclosure, and the scope of the exemplary embodiments is limited only by the accompanying claims, along with equivalents thereof, as long as they are appropriately described.

In the drawings, similar reference numerals are used to designate the same or similar functions in various aspects. The shapes, sizes, etc. of components in the drawings may be exaggerated to make the description clear.

Terms such as “first” and “second” may be used to describe various components, but the components are not restricted by the terms. The terms are used only to distinguish one component from another component. For example, a first component may be named a second component without departing from the scope of the present specification. Likewise, a second component may be named a first component. The terms “and/or” may include combinations of a plurality of related described items or any of a plurality of related described items.

It will be understood that when a component is referred to as being “connected” or “coupled” to another component, the two components may be directly connected or coupled to each other, or intervening components may be present between the two components. It will be understood that when a component is referred to as being “directly connected or coupled”, no intervening components are present between the two components.

Also, components described in the embodiments are independently shown in order to indicate different characteristic functions, but this does not mean that each of the components is formed of a separate piece of hardware or software. That is, the components are arranged and included separately for convenience of description. For example, at least two of the components may be integrated into a single component. Conversely, one component may be divided into multiple components. An embodiment into which the components are integrated or an embodiment in which some components are separated is included in the scope of the present specification as long as it does not depart from the essence of the present specification.

Further, it should be noted that, in the exemplary embodiments, an expression describing that a component “comprises” a specific component means that additional components may be included within the scope of the practice or the technical spirit of exemplary embodiments, but does not preclude the presence of components other than the specific component.

The terms used in the present specification are merely used to describe specific embodiments and are not intended to limit the present invention. A singular expression includes a plural expression unless a description to the contrary is specifically pointed out in context. In the present specification, it should be understood that the terms such as “include” or “have” are merely intended to indicate that features, numbers, steps, operations, components, parts, or combinations thereof are present, and are not intended to exclude the possibility that one or more other features, numbers, steps, operations, components, parts, or combinations thereof will be present or added.

Embodiments will be described in detail below with reference to the accompanying drawings so that those having ordinary knowledge in the technical field to which the embodiments pertain can easily practice the embodiments. In the following description of the embodiments, detailed descriptions of known functions or configurations which are deemed to make the gist of the present specification obscure will be omitted. Further, the same reference numerals are used to designate the same components throughout the drawings, and repeated descriptions of the same components will be omitted.

Hereinafter, “image” may mean a single picture constituting a video, or may mean the video itself. For example, “encoding and/or decoding of an image” may mean “encoding and/or decoding of a video”, and may also mean “encoding and/or decoding of any one of images constituting the video”.