Prediction mode selection method, apparatus and device

A video coding device, comprising:

• one or more processors;
• and
• a memory in which one or more programs are stored, wherein the one or more programs are configured to be executed by the one or more processors and comprise instructions for executing the following operations of:
• selecting, for a current prediction unit, a first group of candidate intra-frame chromaticity prediction modes from N intra-frame prediction modes, wherein N is a positive integer;
• performing a prediction residual cost calculation on each candidate intra-frame chromaticity prediction mode in the first group to obtain a difference evaluation value;
• selecting a second group of candidate intra-frame chromaticity prediction modes from the first group of candidate intra-frame chromaticity prediction modes according to the difference evaluation values, wherein the second group of candidate intra-frame chromaticity prediction modes is a proper subset of the first group of candidate intra-frame chromaticity prediction modes;
• performing a coding cost calculation on each candidate intra-frame chromaticity prediction mode in the second group to obtain a coding cost value;
• and
• determining, according to the coding cost values, one of the candidate intra-frame chromaticity prediction modes in the second group that has a lowest coding cost, as an intra-frame chromaticity prediction mode of the current prediction unit;
• wherein the one or more programs further include instructions for executing the following operations of:
• sequencing the first group of candidate intra-frame chromaticity prediction modes in an ascending order of the difference evaluation values to obtain n1 sequenced candidate intra-frame chromaticity prediction modes;
• determining whether first n2 prediction modes in the n1 sequenced candidate intra-frame chromaticity prediction modes include an intra-frame brightness prediction mode of the current prediction unit, wherein n2 is smaller than n1;
• selecting the first n2 prediction modes as the second group of candidate intra-frame chromaticity prediction modes if the first n2 prediction modes in the n1 sequenced candidate intra-frame chromaticity prediction modes include the intra-frame brightness prediction mode of the current prediction unit;
• selecting the first n2 prediction modes and the intra-frame brightness prediction mode as the second group of candidate intra-frame chromaticity prediction modes if the first n2 prediction modes in the n1 sequenced candidate intra-frame chromaticity prediction modes do not include the intra-frame brightness prediction mode of the current prediction unit.

A non-transitory computer-readable storage medium having stored therein instructions that, when executed by a processor of a video coding device, cause the video coding device to perform a prediction mode selection method, the method comprising:

• selecting, for a current prediction unit, a first group of candidate intra-frame chromaticity prediction modes from N intra-frame prediction modes, wherein N is a positive integer;
• performing a prediction residual cost calculation on each candidate intra-frame chromaticity prediction mode in the first group to obtain a difference evaluation value;
• selecting a second group of candidate intra-frame chromaticity prediction modes from the first group of candidate intra-frame chromaticity prediction modes according to the difference evaluation values, wherein the second group of candidate intra-frame chromaticity prediction modes is a proper subset of the first group of candidate intra-frame chromaticity prediction modes;
• performing a coding cost calculation on each candidate intra-frame chromaticity prediction mode in the second group to obtain a coding cost value;
• and
• determining, according to the coding cost values, one of the candidate intra-frame chromaticity prediction modes in the second group that has a lowest coding cost, as an intra-frame chromaticity prediction mode of the current prediction unit;
• wherein selecting the second group of candidate intra-frame chromaticity prediction modes from the first group of candidate intra-frame chromaticity prediction modes according to the difference evaluation values comprises:
• sequencing the first group of candidate intra-frame chromaticity prediction modes in an ascending order of the difference evaluation values to obtain n1 sequenced candidate intra-frame chromaticity prediction modes;
• determining whether first n2 prediction modes in the n1 sequenced candidate intra-frame chromaticity prediction modes include an intra-frame brightness prediction mode of the current prediction unit, wherein n2 is smaller than n1;
• selecting the first n2 prediction modes as the second group of candidate intra-frame chromaticity prediction modes if the first n2 prediction modes in the n1 sequenced candidate intra-frame chromaticity prediction modes include the intra-frame brightness prediction mode of the current prediction unit;
• selecting the first n2 prediction modes and the intra-frame brightness prediction mode as the second group of candidate intra-frame chromaticity prediction modes if the first n2 prediction modes in the n1 sequenced candidate intra-frame chromaticity prediction modes do not include the intra-frame brightness prediction mode of the current prediction unit.