A data processor that reads and writes data from/on a storage medium. The storage medium has stored thereon a first data stream being represented by a video signal that has been encoded by a first encoding process. The data processor includes: a controller, which acquires first playlist information to manage playback of the first data stream; a stream generating section for generating a second data stream by encoding the video signal by a second encoding process, which is different from the first encoding process; and a management section for producing second playlist information based on the second data stream and the first playlist information so as to manage an order in which the second data stream is played back.