1. Field of the Invention
The present invention relates to a recording medium, a recording method of a recording medium, a recording apparatus of a recording medium, a playback method of a recording medium, a playback apparatus of a recording medium, and a data determination method. In particular, the present invention relates to a recording medium in which data encoded with error correction coding is recorded, a recording method of the recording medium, a recording apparatus of the recording medium, a playback method of the recording medium, a playback apparatus of the recording medium, and a data determination method for determining data encoded with error correction coding.
2. Description of the Related Art
Optical discs such as CDs (Compact Discs) having music data recorded therein (hereinafter referred to as “CD-DA (Compact Disc Digital Audio)”) and CD-ROM (Compact Disc Read-Only Memory) discs are widely accepted as data recording media because such discs are easy to handle and inexpensive. Recently, CD-R (Compact Disc Recordable) discs capable of recording data or CD-RW (Compact Disc ReWritable) discs capable of rewriting data have been commercially available, and users can easily record data in such optical discs. Optical discs complying with the CD standards, including CD-DA, CD-ROM, CD-R, and CD-RW discs, have become dominant in the field of data recording media. In recent years, it has been accomplished to compress audio data in the format of MP3 (MPEG1 Audio Layer-3) or ATRAC3 (Adaptive TRansform Acoustic Coding 3) (trademark) and to record the compressed data in discs such as CD-ROM, CD-R, and CD-RW discs.
However, with the advent of CD-R or CD-RW discs, data recorded in CD-DA or CD-ROM discs has been able to be easily copied, and the demands for copyright protection have been increasingly required. Therefore, it is necessary to take some action for copyright protection of content data when the content data is recorded in a CD-DA or CD-ROM disc.
One method for protecting content data recorded in a CD-DA or CD-ROM disc is to encode the content data before the data is recorded in the disc. The content data encoded before being recorded in a disc cannot be decoded unless data decoding key for decoding the content data is obtained, so that the content data can be protected. Another method is to add DRM (Digital Rights Management) data which indicates copyright protection information of content data so as to establish a playback and copy restriction system of the content data.
Initially, a system employing CD discs was a playback-only recording medium, and is therefore difficult to achieve effective copyright protection. In particular, some existing CD-R or CD-RW drives have a disc-copy function. Such drives enables data in one disc to be copied to another disc. The disc-copy function would allow copying content data even if the content data is encoded or has DRM data recorded therein.
In order to address illegal copying of content data by a disc copy, a method is required for determining whether data recorded in a disc is original data or copied data.
For example, one method for determining whether data recorded in a CD-ROM disc is original data or copied data utilizes the characteristics of CD-ROM data encoded with error correction coding. CD-ROM data is encoded with CIRC (cross-interleaved Reed-Solomon code) error correction coding, and is error corrected in order to increase the error correction performance. In a known method, an error correction code, a sync pattern, a header, a scrambled signal, etc., are intended to be corrupted in CD-ROM (CD-ROM mode 1) and, based on whether or not the corrupted error correction code, sync pattern, header, scrambled signal, etc., are present, it is determined whether or not the disc is an original disc.
However, some recent CD-R or CD-RW drives are able to generate this type of error, and application software for making a disc copy using such a method may be commercially available. Thus, this method may be no longer useful for determining whether data recorded in a CD disc is original data or copied data.