Patent ID: 7848193

Claim:
A disc device for reading and reproducing information recorded on a disc type recording medium, the device comprising: an acquiring means for externally acquiring complementary information for complementing information recorded in a damaged portion from which information on the recording medium cannot be normally read; a storage means formed with a storage area for saving the complementary information; and a control means for reproducing the information recorded on the recording medium while complementing the information recorded in the damaged portion of the recording medium with the complementary information saved in the storage area, wherein when a capacity of a free space not saving the information in the storage area is less than a capacity necessary for saving the new complementary information acquired by the acquiring means, the control means evaluates usefulness of the complementary information based on time elapsed from last referenced time, a reference count, and an acquisition required expense for the complementary information saved in the storage area, deletes the complementary information from the storage area in order of lower usefulness to enlarge the free space, and saves the new complementary information in the free space when the capacity of the free space becomes greater than or equal to the necessary capacity.