1. A data processing apparatus for processing coded data having decoding information used for decoding in predetermined units, said data processing apparatus comprising: tap generation means for generating a tap used for a predetermined process by extracting said decoded data in a predetermined positional relationship with subject data of interest within the decoded data such that said coded data is decoded and by extracting said decoding information in predetermined units according to the position of said subject data in said predetermined units; and processing means for performing a predetermined process by using said tap.