# US 12,225,228 B2 · Image coding method, image decoding method, image coding apparatus, and image decoding apparatus

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- Number: US 12,225,228 B2
- Document ID: US12225228B2
- Status: Granted
- Kind: B2
- Application number: 18/544,808
- Filed: 2023-12-19
- Published: 2024-04-11
- Granted: 2025-02-11
- Earliest claimed: 2011-10-28
- Assignees: Sun Patent Trust
- Applicants: Sun Patent Trust
- Inventors: Viktor Wahadaniah; Chong Soon Lim; Sue Mon Thet Naing; Hai Wei Sun; Takahiro Nishi; Hisao Sasai; Youji Shibahara; Kyoko Tanikawa; Toshiyasu Sugio; Kengo Terada; Toru Matsunobu
- Web page: https://patentgrep.com/patent/US12225228B2

## CPC

- H04N 19/527: Global motion vector estimation
- H04N 19/513: Processing of motion vectors
- H04N 19/52: by predictive encoding
- H04N 19/58: Motion compensation with long-term prediction, i.e. the reference frame for a current frame not being the temporally closest one (H04N19/23 takes precedence)
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

An image coding method includes: deriving a candidate for a motion vector of a current block from a co-located motion vector; adding the candidate to a list; selecting the motion vector of the current block from the list; and coding the current block, wherein the deriving includes: deriving the candidate by a first derivation scheme in the case of determining that each of a current reference picture and a co-located reference picture is a long-term reference picture; and deriving the candidate by a second derivation scheme in the case of determining that each of the current reference picture and the co-located reference picture is a short-term reference picture.

## Claims

### Claim 1

An image decoding method of decoding each block among blocks of pictures, the image decoding method comprising:
selecting a collocated picture from a plurality of referable reference pictures, the collocated picture being different from a current picture that includes a current block to be decoded;
deriving a candidate for motion vectors of the current block, from a first motion vector of a first block included in the collocated picture, the first block being located in the collocated picture at (i) a position corresponding to a position bottom right adjacent to the current block in the current picture or (ii) when the position bottom right is not available, a position corresponding to a position at a center of the current block in the current picture;
adding the derived candidate to a list of motion vector candidates;
selecting, based on an index, one candidate that includes a second motion vector from the list of motion vector candidates; and
decoding the current block using (i) the second motion vector included in the selected one candidate and (ii) a reference picture of the current block,
wherein the deriving includes:
determining whether a collocated reference picture of the first block is a long-term reference picture or a short-term reference picture, the collocated reference picture being a reference picture referred to by the first block included in the collocated picture;
determining whether the reference picture of the current block is a long-term reference picture or a short-term reference picture;
deriving the second motion vector so as to be the same as the first motion vector without scaling based on a temporal distance in the case of determining that (i) the collocated reference picture of the first block is a long-term reference picture and (ii) the reference picture of the current block is a long-term reference picture; and
deriving the second motion vector from the first motion vector by scaling based on a temporal distance in the case of determining that (i) the collocated reference picture of the first block is a short-term reference picture and (ii) the reference picture of the current block is a short-term reference picture,
wherein the scaling is based on a ratio of temporal distance calculated by using (i) a difference between a Picture Order Count (POC) assigned to the current picture and the POC assigned to the reference picture and (ii) a difference between the POC assigned to the collocated picture and the POC assigned to the collocated reference picture, and
wherein the POC is a sequential number assigned for each of the current picture, the reference picture, the collocated picture, and the collocated reference picture based on display order.