Patent ID: 8369689

Claim:
An information recording/reproduction device having a recording portion recording image data, comprising: a portion for generating first class information and second class information, the first class information including reference information indicating at least a part of the image data and the second class information including reference information indicating the first class information; a class information recording portion for recording the first class information and the second class information; and a portion for obtaining reference information on the first class information from the second class information, wherein the second class information includes validity information indicating validity/invalidity of the first class information and position information indicating a recording position of the first class information as being the reference information on the first class information, and the class information recording portion defrags the first class information based on the validity information and position information on the first class information being obtained from the second class information by making a temporary list file, processing reference information such that valid reference information is copied onto the temporary list file and invalid reference information makes no reference to any file, and replacing an original list file with the temporary list file.