To provide a code conversion apparatus capable of reducing a file size before conversion with an identity of a file content preserved.

A code conversion apparatus 1000 inputs therein a codestream 1001 of a target file, and outputs a codestream 1002 converted from the codestream. The code conversion apparatus includes a BOX decomposing unit 1003 for extracting BOX information from an input codestream, a sharing/referencing determining unit 1004 for determining whether sharing process or referencing process is to be performed on the BOX information, and sharing/referencing processing unit 1005 for performing the sharing process or the referencing process on the BOX information based on a determination result from the sharing/referencing determining unit. The sharing/referencing processing unit 1005 can specify a logical set of codes on a referenced side as a unit of reference for referencing an incremental codestream.

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