Image encoding method and apparatus, and image decoding method and apparatus

An image encoding method, performed by an encoding end, the method comprising:

• obtaining a maximum code length of a block to be encoded, wherein the maximum code length is a maximum code stream length allowed to be cached in a code stream buffer;
• pre-coding the block to be encoded based on a first mode to obtain a first code length of the block to be encoded, wherein the first mode is one of a plurality of prediction modes at the encoding end, and the first code length is a length of a code stream obtained after encoding the block to be encoded;
• and
• in response to the first code length being greater than or equal to the maximum code length, adopting a fallback mode to encode the block to be encoded, wherein a code length obtained by encoding the block to be encoded based on the fallback mode is less than or equal to the maximum code length.

An image decoding method, performed by a decoding end, the method comprising:

• determining whether a fallback mode is adopted for an image block corresponding to a block to be decoded during decoding based on a code stream of the block to be decoded, wherein a code length obtained by decoding the image block based on the fallback mode is greater than or equal to a minimum code length of the block to be decoded, wherein the minimum code length is a minimum code stream length allowed to be cached in a code stream buffer;
• in response to the fallback mode being adopted for the image block corresponding to the block to be decoded during decoding, obtaining a first fixed code length based on the code stream, wherein the first fixed code length is a code length of a sub-block to be decoded, and the block to be decoded comprises one or more sub-blocks to be decoded;
• and
• parsing the code stream based on the first fixed code length to decode the block to be decoded.