Methods and devices for high precision intra prediction

An apparatus, comprising:

• one or more processors;
• and
• a memory configured to store instructions executable by the one or more processors;
• wherein the one or more processors, upon execution of the instructions, are configured to:
• obtain a first control flag signaled at a specified level that comprises one of following levels:
• a Transform Block (TB) level, a Coding Block (CB) level, a slice level, a picture level, or a sequence level, wherein the first control flag indicates whether a Decoder-side High Precision Intra Mode Derivation (DHI) mode is enabled, and
• in response to determining that the DHI mode is enabled, derive, using a predefined method, a high precision intra mode under a predefined condition, wherein the predefined condition comprises one of following conditions:
• specific modes, or
• specific block sizes, or
• the DHI mode is used at the specified level.

A non-transitory computer readable storage medium storing a bitstream and instructions that when executed by at least one processor cause the at least one processor to perform acts comprising:

• obtaining a first control flag signaled at a specified level that comprises one of following levels:
• a Transform Block (TB) level, a Coding Block (CB) level, a slice level, a picture level, or a sequence level, wherein the first control flag indicates whether a Decoder-side High Precision Intra Mode Derivation (DHI) mode is enabled, and
• in response to determining that the DHI mode is enabled, deriving, using a predefined method, a high precision intra mode under a predefined condition, wherein the predefined condition comprises one of following conditions:
• specific modes, or
• specific block sizes, or
• the DHI mode is used at the specified level.