Encoding and decoding methods and apparatuses

A method for decoding an intra-frame prediction mode, comprising:

• obtaining a first flag bit from a code stream, wherein the first flag bit indicates whether an intra-frame prediction mode of a current intra-frame decoding block is the same as a reference prediction mode, and when the first flag bit indicates that the intra-frame prediction mode of the current intra-frame decoding block is different from reference prediction modes, obtaining mode encoded bits from the code stream according to a fixed number of bits, wherein the intra-frame prediction mode is a prediction mode adopted when the intra-frame decoding block is pixel-decoded;
• obtaining a prediction mode encoding value according to the mode encoded bits;
• obtaining reference prediction modes of the intra-frame prediction block, wherein the reference prediction modes are intra-frame prediction modes of available adjacent blocks of the current intra-frame decoding block or prediction modes in a preset backup reference mode set;
• and
• obtaining the intra-frame prediction mode of the current intra-frame decoding block according to a size relationship between the prediction mode encoding value and values of the reference prediction modes.

An encoding apparatus, comprising:

• a prediction module, configured to obtain an intra-frame prediction mode of a current intra-frame encoding block from a preset prediction mode set, and obtain reference prediction modes of the current intra-frame encoding block, wherein the reference prediction modes are intra-frame prediction modes of available adjacent blocks of the current intra-frame encoding block or prediction modes in a preset backup reference mode set, wherein all prediction modes in the preset backup reference mode set belong to the preset prediction mode set;
• a flag module, configured to write a first flag bit into a code stream according to the reference prediction modes and the intra-frame prediction mode, wherein the first flag bit indicates whether the intra-frame prediction mode is the same as one of the reference prediction modes;
• and
• a prediction mode encoding module, configured to:
• when the intra-frame prediction mode of the encoding block is different from all the reference prediction modes, obtain a prediction mode encoding value according to a size relationship between a value of the intra-frame prediction mode and values of the reference prediction modes, and encode the prediction mode encoding value.

A decoding apparatus, comprising:

• a code stream reading module, configured to obtain a first flag bit from a code stream, wherein the first flag bit indicates whether an intra-frame prediction mode of a current intra-frame decoding block is the same as a reference prediction mode, and when the first flag bit indicates that the intra-frame prediction mode of the current intra-frame decoding block is different from reference prediction modes, obtain mode encoded bits from the code stream according to the fixed number of bits, wherein the intra-frame prediction mode is a prediction mode adopted when the intra-frame decoding block is pixel-decoded;
• a reference prediction mode obtaining module, configured to obtain reference prediction modes of the intra-frame prediction block, wherein the reference prediction modes are intra-frame prediction modes of available adjacent blocks of the current intra-frame decoding block or prediction modes in a preset backup reference mode set;
• and
• a decoding module, configured to obtain a prediction mode encoding value according to the mode encoded bits, obtain the intra-frame prediction mode of the current intra-frame decoding block according to a size relationship between the prediction mode encoding value and values of the reference prediction modes, and decode the current intra-frame decoding block according to the intra-frame prediction mode.