EP-4738816-A1 - PREDICTION DEVICE, ENCODING DEVICE, DECODING DEVICE, AND PROGRAM

EP4738816A1EP 4738816 A1EP4738816 A1EP 4738816A1EP-4738816-A1

Abstract

A prediction device includes: evaluation means configured to apply a predetermined encoding tool to a target block of prediction, and calculate an evaluation value for each candidate prediction mode by an algorithm common to an encoding side and a decoding side using an adjacent decoded area adjacent to the target block; and determination means configured to determine at least one prediction mode to be used for the prediction from among the candidate prediction modes according to the evaluation value. The candidate prediction modes include an additional prediction mode added to basic prediction modes when the predetermined encoding tool is applied. The evaluation means controls the number of additional prediction modes to be added between basic prediction modes according to at least one of a size of the target block and a shape of the target block.

Inventors

NEMOTO, Shimpei
KUSAKABE, YUICHI
IWAMURA, Shunsuke
ICHIGAYA, ATSURO

Assignees

Nippon Hoso Kyokai

Dates

Publication Date: 20260506
Application Date: 20240628

Claims (11)

A prediction device configured to perform prediction in block units obtained by dividing an image, the prediction device comprising: evaluation means configured to apply a predetermined encoding tool to a target block of the prediction, and calculate an evaluation value for each candidate prediction mode by an algorithm common to an encoding side and a decoding side using an adjacent decoded area adjacent to the target block; and determination means configured to determine at least one prediction mode to be used for the prediction from among the candidate prediction modes according to the evaluation value calculated by the evaluation means, wherein the candidate prediction modes include an additional prediction mode added to basic prediction modes when the predetermined encoding tool is applied, and the evaluation means includes control means configured to control the number of the additional prediction modes to be added between the basic prediction modes according to at least one of a size of the target block and a shape of the target block.
The prediction device according to claim 1, wherein the prediction is intra prediction, the basic prediction modes are basic directional prediction modes, the additional prediction mode is an additional directional prediction mode, and the control means controls an additional mode density indicating the number of the additional directional prediction modes to be added between the basic directional prediction modes having consecutive mode numbers, according to at least one of the size of the target block and the shape of the target block.
The prediction device according to claim 2, wherein the control means sets the additional mode density to a first density in response to the size of the target block being a first size, and sets the additional mode density to a second density higher than the first density in response to the size of the target block being a second size larger than the first size.
The prediction device according to claim 2, wherein the control means sets the additional mode density to be uniform in response to the target block being a square, and sets the additional mode density to be non-uniform in response to the target block being a non-square.
The prediction device according to claim 2, wherein the control means sets a higher additional mode density for all or a part of upward prediction modes, which are the basic directional prediction modes referring only to reference pixels in an upward direction, as compared with other basic directional prediction modes, in response to the target block having a horizontally long shape in which a width is larger than a height.
The prediction device according to claim 2, wherein the control means sets a higher additional mode density for all or a part of leftward prediction modes, which are the basic directional prediction modes referring only to reference pixels in a leftward direction, as compared with other basic directional prediction modes, in response to the target block having a vertically long shape in which a height is larger than a width.
The prediction device according to claim 2, wherein the control means controls the additional mode density according to at least one of the size of the target block and the shape of the target block, and an angular range of the directional prediction.
The prediction device according to claim 7, wherein the control means sets the additional mode density corresponding to a horizontal prediction mode and a vertical prediction mode among the basic directional prediction modes lower than the additional mode density corresponding to other basic directional prediction modes.
An encoding device comprising the prediction device according to any one of claims 1 to 8.
A decoding device comprising the prediction device according to any one of claims 1 to 8.
A program for causing a computer to function as the prediction device according to any one of claims 1 to 8.

Description

TECHNICAL FIELD The present disclosure relates to a prediction device, an encoding device, a decoding device, and a program. BACKGROUND ART In video encoding schemes such as HEVC (High Efficiency Video Codec) and VVC (Versatile Video Coding), an encoding device generates a prediction block, which is a prediction image for a coding block (CU: Coding Unit) obtained by dividing an original image into block units, and transmits the difference between the coding block of the original image and the prediction block after performing transform, quantization, and entropy encoding. As methods for generating a prediction image, inter prediction using correlation between frames and intra prediction using correlation within a frame are prepared. As intra prediction methods, in addition to Planar prediction and DC prediction, directional prediction which is linear prediction can be selected from 33 directions in HEVC and 65 directions in VVC. In intra prediction, a technology is being studied in which a prediction trial is performed using a decoded area around a block to be encoded as a prediction trial area (also referred to as a "template") to derive an intra prediction mode used for intra prediction (for example, see Non Patent Literature 1). Such a technology utilizes the fact that evaluation of intra prediction in the prediction trial area matches between an encoding side and a decoding side. According to such a technology, for example, it is possible to reduce the overhead of signaling of the intra prediction mode, and it is possible to derive an additional directional prediction which subdivides intervals between conventional prediction directions (also referred to as "basic directional prediction modes") to form new prediction directions. CITATION LIST NON PATENT LITERATURE Non Patent Literature 1: JVET-C0061 "Decoder-side intra mode derivation" DISCLOSURE OF INVENTION A prediction device according to a first aspect is a device configured to perform prediction in block units obtained by dividing an image. The prediction device includes: evaluation means configured to apply a predetermined encoding tool to a target block of the prediction, and calculate an evaluation value for each candidate prediction mode by an algorithm common to an encoding side and a decoding side using an adjacent decoded area adjacent to the target block; and determination means configured to determine at least one prediction mode to be used for the prediction from among the candidate prediction modes according to the evaluation value calculated by the evaluation means. The candidate prediction modes include an additional prediction mode added to basic prediction modes when the predetermined encoding tool is applied. The evaluation means has control means configured to control the number of the additional prediction modes to be added between the basic prediction modes according to at least one of a size of the target block and a shape of the target block. An encoding device according to a second aspect includes the prediction device according to the first aspect. A decoding device according to a third aspect includes the prediction device according to the first aspect. A program according to a fourth aspect causes a computer to function as the prediction device according to the first aspect. BRIEF DESCRIPTION OF DRAWINGS Fig. 1 is a diagram illustrating a configuration of an encoding device according to an embodiment.Fig. 2 is a diagram for explaining an example of an intra prediction mode according to the embodiment.Fig. 3 is a diagram for explaining an example of a predetermined encoding tool using a template in intra prediction according to the embodiment.Fig. 4 is a diagram for explaining TIMD according to the embodiment.Fig. 5 is a diagram for explaining DIMD according to the embodiment.Fig. 6 is a diagram illustrating a configuration of an intra predictor on an encoding side according to the embodiment.Fig. 7 is a diagram for explaining a basic directional prediction mode according to the embodiment.Fig. 8 is a diagram for explaining additional mode control according to a block size according to the embodiment.Fig. 9 is a diagram for explaining additional mode control according to a block shape according to the embodiment.Fig. 10 is a diagram for explaining additional mode control according to an angular range of directional prediction according to the embodiment.Fig. 11 is a diagram illustrating a configuration of a decoding device according to the embodiment.Fig. 12 is a diagram illustrating a configuration of an intra predictor on a decoding side according to the embodiment.Fig. 13 is a diagram illustrating an operation example of the intra predictor according to the embodiment. DESCRIPTION OF EMBODIMENTS In the conventional technology, the number of additional directional prediction modes added between basic directional prediction modes having consecutive mode numbers is always one. That is, the density of the additional direction