1. Field of the Invention
The present invention relates to a recording method and a recording apparatus for recording data to a disc shaped rewritable record medium having a large record capacity. The present invention also relates to such a record medium.
2. Description of the Related Art
In recent years, high density optical discs such as a DVD (Digital Versatile Disc) have been developed and standardized. A logical format referred to as UDF (Universal Disc Format) has been proposed. For a DVD-RAM (DVD-Random Access Memory), the UDF is used. The UDF can be also applied to a CD-R that is a writable disc of a CD-ROM (Compact Disc Read Only Memory) and a CD-RW that is a rewritable disc thereof.
In the UDF, a hierarchical file system is used. Corresponding to information stored in the root directory, a sub directory and a substantial file thereof are referenced. Corresponding to information stored in the sub directory, another sub directory and a substantial file thereof are referenced.
Next, the hierarchical file system of the UDF will be described in detail. In the record area of the disc, data is accessed sector by sector. In the DVD-RAM, the record area is accessed from the inner periphery to the outer periphery of the disc. A volume information area is formed from the innermost periphery of the disc to the lead-in area thereof. The volume information area is referred to as system area. The system area represents the position of a file entry (FE) of the root directory. The FE is composed of an allocation descriptor (AD). The AD is information represents the address and length of a root directory, a sub directory, or a file.
The AD of the FE of the root directory represents the logical address and length of the root directory as a substance. The root directory contains at least one file identifier descriptor (FID). The FID references the FE of a sub directory contained in the root directory and the FE of a file contained in the sub directory. These FEs reference respective substances of the sub directory and the file. The substance of the sub directory contains at least one FID. In other words, in the UDF, except for the root directory, corresponding to FIDs and FEs as pointers, FIDs, FEs, and substances are successively accessed.
In the UDF, the above-described FIDs, FEs, and substances can be written in any recordable area. Even if information of sub directories and files are related, their FIDs, FEs, and substances can be written to different addresses. The addresses of the FIDs, FEs, and substances may be assigned regardless of the access order.
FIG. 1 shows an example of a data assignment on a disc corresponding to the conventional UDF. Referring to FIG. 1, a lead-in area 201 is formed on the innermost periphery of a disc 200. A system area 202 is formed outside the lead-in area 201. For example, a substance 203 of a root directory is formed outside the system area 202.
Next, as an example, the case of which a file is accessed from the root directory through a sub directory will be described. Corresponding to the FID of the substance 203 of the root directory, an FE 204 of a sub directory at an address that is physically apart from the substance 203 of the root directory is referenced. Corresponding to an AD of the FE 204 of the sub directory, a substance 205 of a sub directory at an address that is physically apart from the FE 204 of the sub directory is referenced. Likewise, an FID of the substance 205 of the sub directory is referenced. An FE 206 of a file at an address that is physically apart form the substance 205 of the sub directory is referenced. Corresponding to the AD of the FE 206 of the file, a substance 207 of a file at an address that is physically apart from the FE 206 of the file is referenced.
As another example, in the case of which a file is directly referenced from the root directory, the FID of the substance 203 of the root directory is referenced. An FE 208 of a file at an address that is physically apart from the substance 203 of the root directory is referenced. Corresponding to an AD of the FE 208, a substance 209 of a file at an address that is physically apart from the FE 208 of the file is referenced.
Conventionally, when information of directories and files is scattered on a disc, the information cannot be quickly read.
In other words, when one file is accessed with reference to pointers at different addresses, the disc seek time becomes long. In other words, information on the disc cannot be quickly accessed. In particular, this problem is serious in a disc shaped record medium whose access time is longer than a hard disk or the like.
To solve such a problem, pointer information such as FIDs and FEs may be recorded together in a predetermined area. However, in such a case, when a file is deleted from a disc, since an FE thereof is deleted, another file may be written to a blank address for the FE. In such a situation, the pointer information recorded in the predetermined area may be separated. As a result, the above-described problem will take place.