In an approach for detecting key messages for a video, a processor builds a role model based on data from one or more data sources, with an identification feature of each role in a video. A processor samples a plurality of frames of the video. A processor identifies a key object presented in the plurality of frames. The key object is a role in the video. A processor recognizes a movement scenario associated with the role. A processor dynamically updates the role model based on the movement scenario. A processor identifies a role name based on the movement scenario. A processor generates a description script associated with the movement scenario for the role. A processor outputs the description script.