A bi-directional inter prediction decoding method, wherein the decoding method comprises: obtaining a first identifier from a bitstream, wherein when the value of the first identifier is a first preset value, the first identifier indicates that a first reference picture index and a second reference picture index of the current block are obtained without parsing the bitstream, and determined through derivation, the derivation comprising: determining a reference picture index i 1 of a first reference picture list as the first reference picture index that corresponds to a current block and that is of the first reference picture list, wherein a picture order count, POC corresponding to the reference picture index i 1 is less than a POC of a current picture, a difference obtained by subtracting the POC corresponding to the reference picture index i 1 from the POC of the current picture is less than a difference obtained by subtracting a POC corresponding to a reference picture index i x from the POC of the current picture, the reference picture index i x is any reference picture index other than the reference picture index i 1 in reference picture indices of the first reference picture list, and the POC corresponding to the reference picture index i x is less than the POC of the current picture; and determining a reference picture index i 2 of a second reference picture list as the second reference picture index that corresponds to the current block and that is of the second reference picture list, wherein a POC corresponding to the reference picture index i 2 is greater than the POC of the current picture, a difference obtained by subtracting the POC corresponding to the reference picture index i 2 from the POC of the current picture is greater than a difference obtained by subtracting a POC corresponding to a reference picture index i y from the POC of the current picture, the reference picture index i y is any reference picture index other than the reference picture index i 2 in the reference picture indices of the second reference picture list, and the POC corresponding to the reference picture index i y is greater than the POC of the current picture; wherein when the value of the first identifier is a second preset value, which is different from the first preset value, the first identifier indicates that the bitstream needs to be parsed to obtain the first reference picture index and the second reference picture index of the current block; predicting the current block based on the first reference picture index and the second reference picture index, wherein the current picture comprises the current block. determining a reference picture index i 1 of a first reference picture list as the first reference picture index that corresponds to a current block and that is of the first reference picture list, wherein a picture order count, POC corresponding to the reference picture index i 1 is less than a POC of a current picture, a difference obtained by subtracting the POC corresponding to the reference picture index i 1 from the POC of the current picture is less than a difference obtained by subtracting a POC corresponding to a reference picture index i x from the POC of the current picture, the reference picture index i x is any reference picture index other than the reference picture index i 1 in reference picture indices of the first reference picture list, and the POC corresponding to the reference picture index i x is less than the POC of the current picture; and determining a reference picture index i 2 of a second reference picture list as the second reference picture index that corresponds to the current block and that is of the second reference picture list, wherein a POC corresponding to the reference picture index i 2 is greater than the POC of the current picture, a difference obtained by subtracting the POC corresponding to the reference picture index i 2 from the POC of the current picture is greater than a difference obtained by subtracting a POC corresponding to a reference picture index i y from the POC of the current picture, the reference picture index i y is any reference picture index other than the reference picture index i 2 in the reference picture indices of the second reference picture list, and the POC corresponding to the reference picture index i y is greater than the POC of the current picture; wherein when the value of the first identifier is a second preset value, which is different from the first preset value, the first identifier indicates that the bitstream needs to be parsed to obtain the first reference picture index and the second reference picture index of the current block; predicting the current block based on the first reference picture index and the second reference picture index, wherein the current picture comprises the current block.