One example of a conventional indexing method for storage, display and search of video data is described in Patent Document 1. With this conventional method, a determination is made whether telop characters are displayed for each frame of input video data, a character area is extracted from the frame whose telop characters are displayed so that a process for recognizing the telop characters is executed. Further, an index file which includes the recognized result of the telop characters and ID information at the time of displaying the telop characters is generated. The ID information is ID information at the time of inputting the frame to be recognized. Further, the Patent Document 1 discloses that the ID information is occasionally the input time information of the frame.
Patent Document 1: Japanese Patent Application Laid-Open No. 11-167583 (JP-A 11-167583) (paragraph 0002 and FIG. 2)