Key frame extracting method for compression domain video stream

The invention discloses a method for extracting a key frame of a video stream in a compressed domain. The method comprises the following steps: the video stream of the compressed domain is input; the video stream of the compressed domain is subjected to variable length entropy decoding, and correlative characteristics of a coding macroblock in the video stream of the compressed domain are extracted; the correlative characteristics of the coding macroblock in the video stream are utilized to carry out time-domain partitioning on the video stream of the compressed domain to obtain a plurality of lens segments; the plurality of the lens segments obtained by the correlative characteristics of the coding macroblock in the video stream are utilized to carry out lens sorting and are divided into a static lens segment, a person and object motion lens segment and a camera motion lens segment; and after lens sorting, each lens segment is subjected to extraction of the corresponding key frame according to classification to obtain the key frame of the lens segment. The method has good extraction effect and keeps good consistency with human vision.