# US 2021/0344906 A1 · Encoder, decoder, encoding method, and decoding method

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- Number: US 2021/0344906 A1
- Document ID: US20210344906A1
- Status: Published application
- Kind: A1
- Application number: 17/374,085
- Filed: 2021-07-13
- Published: 2021-11-04
- Earliest claimed: 2017-06-05
- Assignees: Panasonic Intellectual Property Corporation of America
- Applicants: Panasonic Intellectual Property Corporation of America
- Inventors: Kiyofumi Abe; Takahiro Nishi; Tadamasa Toma; Ryuichi Kanoh
- Web page: https://patentgrep.com/patent/US20210344906A1

## CPC

- H04N 19/105: Selection of the reference unit for prediction within a chosen coding or prediction mode, e.g. adaptive choice of position and number of pixels used for prediction
- H04N 19/119: Adaptive subdivision aspects, e.g. subdivision of a picture into rectangular or non-rectangular coding blocks
- H04N 19/139: Analysis of motion vectors, e.g. their magnitude, direction, variance or reliability
- H04N 19/14: Coding unit complexity, e.g. amount of activity or edge presence estimation (H04N19/146 takes precedence)
- H04N 19/176: the region being a block, e.g. a macroblock
- H04N 19/52: by predictive encoding
- H04N 19/573: Motion compensation with multiple frame prediction using two or more reference frames in a given prediction direction
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

An encoder is disclosed which includes circuitry and memory. Using the memory, the circuitry, in a first operating mode, derives first motion vectors for a first block obtained by splitting a picture, and generates a prediction image corresponding to the first block, with a bi-directional optical flow flag settable to true, and by referring to spatial gradients of luminance generated based on the first motion vectors. Using the memory, the circuitry, in a second operating mode, derives second motion vectors for a sub-block obtained by splitting a second block, the second block being obtained by splitting the picture, and generates a prediction image corresponding to the sub-block, with the bi-directional optical flow flag set to false.

## Claims

### Claim 1

An encoder comprising:
circuitry; and
memory,
wherein, using the memory, the circuitry:
in a first operating mode,
derives first motion vectors for a first block obtained by splitting a picture, and
generates a prediction image corresponding to the first block, with a bi-directional optical flow flag set to true, by referring to spatial gradients of luminance generated based on the first motion vectors; and
in a second operating mode,
derives second motion vectors for a sub-block obtained by splitting a second block, the second block being obtained by splitting the picture, and
generates a prediction image corresponding to the sub-block, with the bi-directional optical flow flag set to false.

### Claim 2

An encoding method, comprising:
in a first operating mode,
deriving first motion vectors for a first block obtained by splitting a picture, and
generating a prediction image corresponding to the first block, with a bi-directional optical flow flag set to true, by referring to spatial gradients of luminance generated based on the first motion vectors; and
in a second operating mode,
deriving second motion vectors for a sub-block obtained by splitting a second block, the second block being obtained by splitting the picture, and
generating a prediction image corresponding to the sub-block, with the bi-directional optical flow flag set to false.

### Claim 3

A non-transitory computer readable medium storing a bitstream, the bitstream comprising:
information according to which a decoder derives first motion vectors or second motion vectors in a decoding process; and
a picture including a first block and a second block obtained by splitting the picture, wherein
in the decoding process:
in a first operating mode,
the first motion vectors are derived for the first block, and
a prediction image corresponding to the first block is generated, with a bi-directional optical flow flag set to true, by referring to spatial gradients of luminance generated based on the first motion vectors; and
in a second operating mode,
the second motion vectors are derived for a sub-block obtained by splitting the second block, and
a prediction image corresponding to the sub-block is generated, with the bi-directional optical flow flag set to false.