Disclosed are an inter prediction method, encoder/decoder, and storage medium. The method includes: determining a prediction mode parameter of a current block; when the parameter indicates that a GPM is used for determining an inter prediction value of the current block, determining an angle and a distance corresponding to a dividing line in the current block, setting an angle index value and a distance index value to index serial numbers corresponding to the angle and the distance in a preset mapping table respectively; determining a value of shifting direction indicator of the current block, which is used for indicating shifting directions of different dividing lines of the current block at the angle, by using a preset model based on size information and the angle index value of the current block; performing inter prediction on the current block based on the value of shifting direction indicator and the distance index value.