JPWO2020050685A5

JPWO2020050685A5 -

Info

Publication number: JPWO2020050685A5
Application number: JP2021537422A
Authority: JP
Publication date: 2022-09-15

Claims

determining a reference region for intra prediction of the current block;
deriving an intra-prediction mode for the current block based on a given set of MPM candidates;
performing intra prediction on the current block based on the reference region and the intra prediction mode;
The MPM candidate group is divided into a first group and a second group,
the first group includes default modes already defined in a decoding device, the second group includes intra-prediction modes of adjacent blocks adjacent to the current block;
The image decoding method, wherein the intra-prediction mode of the current block is derived selectively using either the first group or the second group.

The step of determining the reference region comprises:
selecting one of a plurality of pixel lines already defined in the decoding device;
determining the selected pixel line as the reference region;
The plurality of pre-defined pixel lines may be a first pixel line adjacent to the current block, a second pixel line adjacent to the first pixel line, a third pixel line adjacent to the second pixel line, or the 2. The image decoding method of claim 1, comprising at least one of the fourth pixel lines adjacent to the third pixel line.

the default mode consists only of a non-directional mode;
2. The image decoding method of claim 1, wherein the non-directional mode includes at least one of Planar mode and DC mode.

the second group further includes a mode derived by adding or subtracting an N value to the intra prediction mode of the neighboring block;
4. The image decoding method according to claim 3, wherein said N value is 1, 2 or 3.

further comprising obtaining a first flag from the bitstream;
the first flag indicates whether the intra prediction mode of the current block is derived from the first group;
if the value of the first flag is the first value, the intra prediction mode of the current block is set to MPM belonging to the first group;
3. The method of claim 2, wherein the intra-prediction mode of the current block is derived based on the second group and an MPM index when the value of the first flag is a second value.

6. The image decoding method of claim 5, wherein the first flag is signaled only if the reference area of the current block is the first pixel line.

further comprising dividing the current block into a plurality of sub-blocks;
The intra prediction is performed in units of the sub-blocks,
The image decoding method of claim 1, wherein the number of sub-blocks is variably determined based on the size or shape of the current block.

determining a reference region for intra prediction of the current block;
determining an intra-prediction mode for the current block;
performing intra prediction on the current block based on the reference region and the intra prediction mode;
encoding the intra-prediction mode based on a given set of MPM candidates;
The MPM candidate group is divided into a first group and a second group,
the first group includes default modes already defined in an encoding device, the second group includes intra-prediction modes of neighboring blocks adjacent to the current block;
An image coding method, wherein the intra prediction mode of the current block is coded by selectively using either the first group or the second group.

transmitting a bitstream generated by the image encoding method to an image decoding device;
The image encoding method comprises:
determining a reference region for intra prediction of the current block;
determining an intra-prediction mode for the current block;
performing intra prediction on the current block based on the reference region and the intra prediction mode;
encoding the intra-prediction mode based on a given set of MPM candidates;
The MPM candidate group is divided into a first group and a second group,
the first group includes default modes already defined in an encoding device, the second group includes intra-prediction modes of neighboring blocks adjacent to the current block;
The bitstream transmission method, wherein the intra-prediction mode of the current block is encoded by selectively using either the first group or the second group.