# US 12,771,870 B2 · Image encoding/decoding methods and apparatuses

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- Number: US 12,771,870 B2
- Document ID: US12771870B2
- Status: Granted
- Kind: B2
- Application number: 19/253,655
- Filed: 2025-06-27
- Published: 2025-10-16
- Granted: 2026-10-20
- Earliest claimed: 2018-10-12
- Assignees: Dolby International AB
- Applicants: Dolby International AB
- Inventors: Bae Keun Lee; Dong San Jun
- Web page: https://patentgrep.com/patent/US12771870B2

## CPC

- H04N 19/593: involving spatial prediction techniques
- 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 19/11: among a plurality of spatial predictive coding modes
- H04N 19/119: Adaptive subdivision aspects, e.g. subdivision of a picture into rectangular or non-rectangular coding blocks
- H04N 19/122: Selection of transform size, e.g. 8x8 or 2x4x8 DCT; Selection of sub-band transforms of varying structure or type
- H04N 19/132: Sampling, masking or truncation of coding units, e.g. adaptive resampling, frame skipping, frame interpolation or high-frequency transform coefficient masking
- H04N 19/176: the region being a block, e.g. a macroblock
- H04N 19/129: Scanning of coding units, e.g. zig-zag scan of transform coefficients or flexible macroblock ordering [FMO]
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

Image encoding/decoding methods and apparatuses according to the present invention may generate a prediction block of a current block based on a pre-defined prediction mode, generate a transform block of the current block through predetermined transformation, and reconstruct the current block based on the prediction block and the transform block.

## Claims

### Claim 1

A method of decoding an image, the method comprising:
determining a current block by partitioning a coding block in the image based on a tree-based block division;
determining an intra prediction mode of the current block based on a syntax element obtained from a bitstream;
generating a prediction block of the current block by performing intra prediction of the current block based on the intra prediction mode; and
reconstructing the current block based on the prediction block,
wherein the syntax element comprises a flag indicating whether a pre-defined default mode is used for the intra prediction of the current block,
wherein, in response to the flag indicating that the default mode is used for the intra prediction of the current block, the intra prediction mode is set to the default mode,
wherein, in response to the flag indicating that the default mode is not used for the intra prediction of the current block, the intra prediction mode is derived from a candidate group including a plurality of most probable mode (MPM) candidates, and
wherein the default mode is representative of a Planar mode.

### Claim 2 (depends on 1)

The method of claim 1, wherein the default mode is not included in the candidate group.

### Claim 3 (depends on 2)

The method of claim 2, wherein the plurality of MPM candidates comprises at least one of an intra prediction mode of a surrounding block (candIntraPredMode), candIntraPredMode−N, or candIntraPredMode+N, and
wherein N is equal to 2.

### Claim 4 (depends on 2)

The method of claim 2, wherein the plurality of MPM candidates comprises at least one of a DC mode, a vertical mode, a horizontal mode, (a vertical mode−M) or (a vertical mode+M), and
wherein M is equal to 4.

### Claim 5 (depends on 1)

The method of claim 1, wherein, in response to the intra prediction mode being a directional mode, the intra prediction mode is modified by adding or subtracting a predetermined offset,
wherein the intra prediction is performed using the modified intra prediction mode, and
wherein the modification of the intra prediction mode is selectively performed based on at least one of a size, a shape, partition information, a value of the intra prediction mode, or a component type of the current block.

### Claim 6 (depends on 1)

The method of claim 1, wherein performing the intra prediction comprises:
partitioning the current block into a plurality of sub-blocks by using a vertical line or a horizontal line; and
sequentially performing the intra prediction in units of the sub-blocks,
wherein a number of the sub-blocks belonging to the current block is variably determined based on at least one of a size or a shape of the current block.

### Claim 7 (depends on 1)

The method of claim 1, wherein performing the intra prediction comprising:
modifying a prediction value, generated by performing the intra prediction, based on a predetermined reference sample and a weight.

### Claim 8 (depends on 7)

The method of claim 7, wherein each of the reference sample and the weight is determined based on at least one of a size of the current block, a position of a current sample to be modified, or the intra prediction mode of the current block.

### Claim 9 (depends on 1)

The method of claim 1, wherein, in response to a case where the default mode is used for the intra prediction of the current block, an intra reference line for the intra prediction is restricted to be determined as only a reference line adjacent to the current block among a plurality of reference lines.

### Claim 10

A method of encoding an image, the method comprising:
determining a current block by partitioning a coding block in the image based on a tree-based block division;
determining an intra prediction mode of the current block;
generating a prediction block of the current block by performing intra prediction of the current block; and
obtaining a residual block of the current block based on the prediction block,
wherein a prediction block of the current block is generated by performing the intra prediction based on the determined intra prediction mode,
wherein a flag indicating whether a pre-defined default mode is used for the intra prediction of the current block is encoded into a bitstream,
wherein, in response to a case where the default mode is used for the intra prediction of the current block, the intra prediction mode is determined to be the default mode,
wherein, in response to a case where the default mode is not used for the intra prediction of the current block, the intra prediction mode is determined from a candidate group including a plurality of most probable mode (MPM) candidates, and
wherein the default mode is representative of a Planar mode.

### Claim 11

A non-transitory computer-readable storage medium for storing a bitstream generated by an image encoding method,
the image encoding method comprising:
determining a current block by partitioning a coding block based on a tree-based block division;
determining an intra prediction mode of the current block;
generating a prediction block of the current block by performing intra prediction of the current block; and
obtaining a residual block of the current block based on the prediction block,
wherein a prediction block of the current block is generated by performing the intra prediction based on the determined intra prediction mode,
wherein a flag indicating whether a pre-defined default mode is used for the intra prediction of the current block is encoded into a bitstream,
wherein, in response to a case where the default mode is used for the intra prediction of the current block, the intra prediction mode is determined to be the default mode,
wherein, in response to a case where the default mode is not used for the intra prediction of the current block, the intra prediction mode is determined from a candidate group including a plurality of MPM candidates, and
wherein the default mode is representative of a Planar mode.