A long video understanding method based on iterative hierarchical
key frame selection comprises the following steps: firstly, carrying out hierarchical frame sampling on an input video to obtain hierarchical visual features, and then carrying out a
key frame query module on the Nth-layer visual features of a video frame and an input problem text to obtain a
key frame query result; video key frame query is carried out in combination with context
semantics to generate query vectors, whether the query vectors are enough to generate answers to the input questions is predicted, if not, the query key frames are updated in the (N + 1) th layer of visual features with the higher
frame rate, and the input question texts are combined with the context
semantics to carry out iterative query of the key frames again; and inputting the inquired key frame and the instruction or the question into a multi-mode
large model to generate an understanding result. According to the method, the video frames are queried and the associated frames are screened out based on the
user input problem, so that the performance and efficiency of long video understanding are improved, and the method has wide application prospects in scenes such as entertainment, security and education.