Patent Publication Number: US-8121007-B2

Title: Pseudo-overwriting data on write-once discs

Description:
The present application is a §371 of PCT/JP05/08821, filed May 9, 2005, which claims priority to U.S. Provisional Application Nos. 60/569,537, filed May 10, 2004; 60/577,616, filed Jun. 7, 2004; 60/605,488, filed Aug. 31, 2004; and 60/668,237, filed Apr. 4, 2005. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a recording method for a write-once disc using a logical-overwritable mechanism and a semiconductor integrated circuit for use in a recording apparatus and/or a reproduction apparatus. 
     BACKGROUND ART 
     File systems for optical discs have made advances through various activities to develop UDF (Universal Disk Format®) specifications published from OSTA (Optical Storage Technology Association). 
     For write-once discs, the recording method has improved from multi-session recording to file-by-file recording using VAT (Virtual Allocation Table). 
     On the other hand, for rewritable discs, a volume and file structure has improved from the structure using non-sequential recording defined in ECMA 167, which is the international standard, to the structure using Metadata Partition specified in UDF Revision 2.5 (hereinafter UDF 2.5). The merits to use Metadata Partition are the improvement in the performance to retrieve metadata, such as file entries/directories, and to increase the robustness from media damage. 
     However, Metadata Partition cannot be used for data appending usage on a write-once disc. This is because it is not allowed in UDF 2.5 to use Metadata Partition with VAT, due to the difficulty to implement this combination. 
     Typically, it is also difficult to develop a new recording method for a write-once disc. This comes from the physical characteristics such as that the data written at once can not be overwritten, hence it would be required to study from the several aspects, to be consistent with computer architecture, the possibility of implementation for drive apparatus, the restrictions due to the dedicated resource of consumer appliances, etc. 
     The present invention has been made in view of the above subjects and includes an objective of providing the merits of Metadata Partition to the data recording usage on a write-once disc. 
     DISCLOSURE OF THE INVENTION 
     A recording method for instructing a drive apparatus having a pseudo-overwrite function to write data on a write-once disc according to the present invention includes: (a) receiving a write request which specifies at least data for a file to be written; (b) instructing the drive apparatus to read metadata for managing the file from a location in the write-once disc, so as to obtain the metadata; (c) querying a next writable address indicating a location at which data is to be written next to the drive apparatus, so as to obtain the next writable address; (d) updating the metadata to reflect the writing of the data specified by the write request; (e) instructing the drive apparatus to write the data specified by the write request to a location indicated by the next writable address in the write-once disc; and (f) instructing the drive apparatus to write at least a part of the updated metadata to the location from which the metadata is read in the step (b) in the write-once disc. 
     In one embodiment of the present invention, the steps (e) and (f) are performed using the same write instruction. 
     In one embodiment of the present invention, the step (f) is performed after the step (e) is performed. 
     In one embodiment of the present invention, the updated metadata includes a file entry of a directory under which the file is recorded. 
     In one embodiment of the present invention, the updated metadata includes a file entry of the file. 
     According to another aspect of the present invention, a system controller is provided for instructing a drive apparatus having a pseudo-overwrite function to write data on a write-once disc, the system controller including a controller for controlling the drive apparatus, wherein the controller is configured to perform a process including the steps of: (a) receiving a write request which specifies at least data for a file to be written; (b) instructing the drive apparatus to read metadata for managing the file from a location in the write-once disc, so as to obtain the metadata; (c) querying a next writable address indicating a location at which data is to be written next to the drive apparatus, so as to obtain the next writable address; (d) updating the metadata to reflect the writing of the data specified by the write request; (e) instructing the drive apparatus to write the data specified by the write request to a location indicated by the next writable address in the write-once disc; and (f) instructing the drive apparatus to write at least a part of the updated metadata to the location from which the metadata is read in the step (b) in the write-once disc. 
     In one embodiment of the present invention, the controller includes a semiconductor integrated circuit. 
     According to another aspect of the present invention a program is provided for use in a system controller for instructing a drive apparatus having a pseudo-overwrite function to write data on a write-once disc, wherein the program is configured to perform a process including the steps of: (a) receiving a write request which specifies at least data for a file to be written; (b) instructing the drive apparatus to read metadata for managing the file from a location in the write-once disc, so as to obtain the metadata; (c) querying a next writable address indicating a location at which data is to be written next to the drive apparatus, so as to obtain the next writable address; (d) updating the metadata to reflect the writing of the data specified by the write request; (e) instructing the drive apparatus to write the data specified by the write request to a location indicated by the next writable address in the write-once disc; and (f) instructing the drive apparatus to write at least a part of the updated metadata to the location from which the metadata is read in the step (b) in the write-once disc. 
     These and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram illustrating a configuration of areas when a file is recorded. 
         FIG. 2  is a diagram illustrating a configuration of areas when a Data-A file is recorded in a root directory of a disc having the state as shown  FIG. 1 . 
         FIG. 3  is a diagram illustrating a configuration of areas when a Data-A file is recorded in a root directory on a disc which having a larger spare area. 
         FIG. 4  is a flowchart illustrating a procedure for recording a file. 
         FIG. 5  is a diagram illustrating an optical disc information recording/reproduction system. 
         FIG. 6  is a diagram illustrating transfer of commands between a drive apparatus and a system controller. 
         FIGS. 7A-7D  each comprise a diagram illustrating the blocks in a user data area, when the data is remapped for a rewritable disc case and write-once disc case. 
         FIGS. 8A and 8B  each comprise a diagram illustrating the blocks in a user data area, when the data is written to NWA. 
         FIG. 9  is a diagram illustrating the data structure of the remapping table. 
         FIG. 10  is a diagram illustrating a configuration of areas to explain a pseudo-overwrite method. 
         FIGS. 11A and 11B  each comprise a flowchart illustrating a procedure to write the data by an optical disc information recording/reproduction system. 
         FIG. 12  is a diagram illustrating an optical disc information recording/reproduction system which is a part of consumer video recorder or consumer video player. 
         FIG. 13  is a flowchart illustrating a procedure to write the data on a write-once optical disc by the recording/reproduction system explained in  FIG. 12 . 
         FIG. 14  is a flowchart illustrating a procedure to read the data from a write-once optical disc by the recording/reproduction system explained in  FIGS. 5 and 12 . 
         FIG. 15A-15D  each comprise a diagram illustrating the blocks in a user data area, when the data is written using a pseudo-overwrite method. 
         FIGS. 16A-16C  each comprise an example of track layouts after logical format, and after some files are recorded. 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     An overwritable function for a write-once disc performed by drive apparatus has been studied. However, it was difficult to put it in practice, because the drive apparatus cannot know how much data will be overwritten and where the data will be overwritten. 
     For example, the data to be overwritten is stored in the other location as a write-once disc, and the information to specify the original location and the replacement location have to be handled in the drive apparatus. When the amount of overwritten data increases, it takes a longer time to search where it is replaced. Hence, such a drive apparatus could not read/write with enough performance due to its small resources (e.g. CPU speed and memory). 
     It is believed the new file system should distinguish the data to be overwritten and the data to be newly written, and the new file system can match with the drive apparatus which has an overwritable function. Then, the possibility to apply Metadata Partition for data appending usage on a write-once disc, without using VAT is found. 
     The strategic importance of this idea includes; by having the device handle the overwriting of existing blocks, the file system does not need to implement the logic. This reduces the complexity of the file system driver. 
     In the following embodiments, the investigations based on this idea are shown in detail. 
     Embodiment 1 
     The amount of the overwritten data can be reduced by optimizing the procedure in the file system. In this embodiment, the basic read/write operation is explained in accordance with the new recording method for the drive apparatus with the overwritable function of a write-once disc. 
     Hereinafter, embodiments of the present invention will be described with reference to the drawings. 
       FIGS. 1 and 2  are diagrams showing a configuration of areas.  FIG. 4  is a flowchart showing a procedure for recording a file.  FIG. 1  shows the state where a file has been recorded after a logical format operation.  FIG. 2  shows the state where a Data-A file has been recorded in a root directory on a disc having the state of  FIG. 1 . 
     Firstly,  FIG. 1  will be described. 
     The data area includes the areas such as a Lead-in area, a volume space and a Lead-out area, (wherein the Lead-in area and the Lead-out area are managed by a physical layer). The physical sector is an addressable unit in the data area and the physical sector number is assigned in ascending sequence to each physical sector. The volume space consists of logical sectors and a logical sector number is assigned in ascending sequence to each logical sector. Each logical sector corresponds to the physical sector uniquely in advance. For example, the logical sector with a logical sector number 0 corresponds to the physical sector with physical sector number 10000 and the start address of the volume space is stored in the Lead-in area. 
     The defect Management Area (DMA) is an area, in which information indicating the correspondence between the address of a block to be replaced and the address of a replaced block in a replacement operation, is recorded as a defect list. 
     Temporary DMA (TDMA) is an area, in which a temporary defect list is recorded in an incremental write operation. When a disc is finalized to prohibit incremental write operations, a temporary defect list is registered as a defect list in DMA. DMA is provided in two portions of a disc, i.e., at an inner portion and at an outer portion. Thus, a defect list is recorded in different areas twice. In DMA, disc information, such as track information, positional information of a spare area, and the like, are recorded. 
     The spare area is a replacement area, in which data is recorded by a replacement operation, which is equivalent to a linear replacement method. The spare area is assigned outside a volume space which is handled by a file system. In this example, data has been recorded in a portion of the spare area. Addresses in the spare area are inherently specified by using physical addresses. To simplify the explanation, relative addresses in the spare area are indicated by SA&#39;s (Spare area Address). Sectors on and after SA #m are in the unrecorded state. 
     In the present invention, the linear replacement algorithm which is generally used for defect management is applied to overwriting performed by the drive apparatus. 
     The volume space consists of three tracks. A track is an area in which the data is recorded sequentially from the beginning of the track on a write-once disc. The end of recorded area in a track is managed by a drive apparatus. Track Status (Close and Open) indicates a status of a track. “Close” indicates that all sectors in a track have been used for data recording. “Open” indicates that there is a sector(s), which has not been used for data recording. In other words, data can be incrementally written into an open track. 
     (Volume Structure) 
     The volume and file structure complies with UDF 2.5. A volume structure, which is located at an area having a smaller logical sector number, includes Anchor Volume Descriptor Pointer, Volume Recognition Sequence, Volume Descriptor Sequence, and Logical Volume Integrity Sequence. A volume structure, which is located at an area having a larger logical sector number, includes Anchor Volume Descriptor Pointer and Volume Descriptor Sequence. The Logical Volume Integrity Sequence, in which a Logical Volume Integrity Descriptor is recorded, is a part of a volume structure. However, for convenience of explanation in this example, the Logical Volume Integrity Descriptor is explicitly described under the volume structure. Since the volume structure has been previously recorded, Tracks # 1  and # 3  are in the close state. The area described as Track # 2  is assigned as a partition specified by UDF. The Metadata file is also called a Metadata partition. To distinguish it from the Metadata partition, Track # 2  area is called a physical partition. In the Metadata file, an unused area is recorded in advance. Track # 2  is an area for recording file data. Therefore, an area following the recorded area is in the unrecorded state. 
     (File Structure) 
     Metadata Bitmap FE (Metadata Bitmap file File Entry) is a file entry for organizing the areas allocated for a Metadata Bitmap. Metadata Bitmap is a bitmap for specifying available sectors which are ready for use in a Metadata file. Not only unrecorded areas, but also an area which becomes an unused area by deleting a file entry or a directory, are registered in the bitmap as available areas. Metadata file FE (Metadata file File Entry) is a file entry for organizing the areas allocated for a Metadata file. In a Metadata file, file entries and directories are recorded. In UDF, a File Set Descriptor is also recorded, which is not shown in the figure. 
     Root directory FE (root directory file entry) is a file entry for organizing the areas allocated for the root directory. A root directory FE is recorded in MA #i. A root directory is recorded in MA #i+1. Though not shown, the root directory FE and the root directory are actually stored physically in sectors in the spare area. Information indicating which sector in the spare area replaces a root directory FE and a root directory is recorded in TDMA. MA (Metadata file Address) indicates a relative address within a Metadata file. Since a file(s) have been previously recorded, areas on and after MA #k are available. 
     (File Recording Procedure) 
     An exemplary procedure for recording a Data-A file onto the write-once disc of  FIG. 1  will be described with reference to  FIGS. 2 and 4 . 
     In step S 101 , the Metadata Bitmap is read into a memory and is updated in the memory to obtain a recording area in the Metadata file. 
     In step S 102 , a directory, under which a file is to be registered, is read into the memory, and is updated in the memory. In this example, the root directory is read out, and the Data-A file is registered. 
     In step S 103 , the file entry of the directory is read into the memory, and information (e.g., size and update time, etc.) of the directory is updated. 
     In step S 104 , the Data-A file data is recorded from the beginning of the unrecorded area in Track # 2 . 
     In step S 105 , in order to register the positional information of the recorded data, the file entry of the file is generated in the memory. 
     In step S 106 , the data updated or generated in the memory is recorded. In the example of  FIG. 2 , a drive apparatus is instructed to record the Metadata Bitmap file in the same place. Since the specified area is an already-recorded area, the drive apparatus records data at SA #m, which is the beginning of the unrecorded area in the spare area. It is instructed that the root directory is recorded at MA #k. Therefore, the root directory recorded at MA #i+1 becomes invalid, and the sector at MA #i+1 becomes an available sector in a logical space. Even if it is instructed that data is recorded into an available area in the Metadata file, the data cannot be recorded into the area, since the all area in the Metadata file is already recorded in advance. Therefore, the data of the root directory is recorded into SA #m+1 in the spare area by a replacement operation. 
     The replacement operation is a pseudo-overwrite operation of the present invention. As used herein, the term “pseudo-overwrite operation” refers to a logical overwrite operation, in which the mechanism of a replacement operation is used to write the data into the unrecorded area in response to an instruction to write the data into an already recorded area. 
     It is instructed that the file entry of the root directory is written into MA #i. In this case, MA #i is an already-recorded area. Therefore, the data is stored into SA #m+2 in the spare area by a pseudo-overwrite operation. It is instructed that the file entry of the Data-A file is written into MA #k+1. The data is stored into SA #m+3 by a pseudo-overwrite operation. 
     In step S 107 , it is instructed that the Logical Volume Integrity Descriptor is updated to indicate the integrity state of the file structure. The data is stored into SA #m+4 by a pseudo-overwrite operation. 
     As described in step S 106 , by recording a plurality of pieces of data together so that as many of the pieces of data as possible are recorded in the same ECC block (recording timing) by using a cache, it is possible to effectively utilize an unrecorded area in the spare area. Particularly, a Metadata Bitmap or a Logical Volume Integrity Descriptor may not be updated every time a file is recorded. By recording the Metadata Bitmap or the Logical Volume Integrity Descriptor after a plurality of files have been recorded, it is possible to effectively use an unrecorded area of the spare area. 
       FIG. 5  shows an optical disc information recording/reproduction system  500  according to the present invention. The information recording/reproduction system  500  includes a system controller  510 , a drive apparatus  520  for reading and writing information from and onto an optical disc, and an input/output bus  530 . 
     Between the system controller  510  and the drive apparatus  520 , instructions and responses using a command set and transfer of the read/write data are performed through the input/output bus  530 . 
     The system controller  510  includes a controller  511  and a memory  512 . The system controller  510  may be a personal computer. The controller  511  may be, for example, a semiconductor integrated circuit such as a CPU (Central Processing Unit) and performs the method described in the embodiments of the present inventions. 
     Further, a program for causing the controller  511  to perform the method described in the embodiments is stored in the memory  512 . In the controller  511 , a file system, a utility program, or a device driver may be performed. 
     The drive apparatus  520  includes a system LSI  521 , a memory  522  and a drive mechanism  523 . A program for causing the system LSI  521  to perform the method described in the embodiments of the present inventions may be stored in the memory  522 . The system LSI  521  may be formed on a semiconductor chip and may include a micro processor. 
     The drive mechanism  523  includes a mechanism for loading an optical disc, a pickup  524  for writing/reading the data from/onto a disc, a traverse mechanism for moving the pickup  524 . The drive mechanism  523  is controlled by the system LSI  521 . 
     As explained above, the data of a file can be recorded without being overwritten, some of metadata can be recorded using pseudo-overwrite. Typically, the size of metadata needed to update a file is smaller than the data size of the file, and then the size of data to be overwritten can be reduced. The size of a file entry is 2048 bytes, and the size of a directory depends on the number of files and the length of the file name. As an example, if each file name is 12 characters and 39 files are recorded in the directory, the directory information can be recorded within a sector of 2048 bytes. Therefore, the read/write operation can be realized basically for a write-once disc by combining the new recording method and the drive apparatus with the overwritten function. 
     Embodiment 2 
     This embodiment describes a further recording method to write a file onto a write-once disc on which the state is explained in embodiment 1 as  FIG. 2 . 
     In  FIG. 2 , the unrecorded area is only 2 sectors of SA #m+5 and #m+6, therefore, if the Metadata Bitmap and the root directory are written in the spare area, a file entry of the root directory, and a file entry of the file can not be written any more. Thus, an additional file can not be recorded, even if the Metadata Bitmap indicates available areas in the Metadata file, because the unrecorded area in the spare area is used up. 
     So, hereinafter a recording method to record the file with checking the size of unrecorded areas in the spare area is described. 
       FIG. 3  is a diagram illustrating a configuration of areas on the disc on which the same data as shown in  FIG. 2  is written. In  FIG. 3 , as a spare area with the larger size has been provided by a logical formatting operation, the spare area has a larger unrecorded area than that of  FIG. 2 . 
       FIG. 6  is a diagram illustrating data transfer with commands between a drive apparatus and a system controller. Specific commands can be applied to standards defined by ANSI (American National Standards Institute) or Multi-Media Command Set Standards defined by the INCITS (Inter National Committee for Information Technology Standards) T10. 
     Steps S 601 , S 603 , S 605 , and S 607  indicate procedures performed by the system controller. Steps S 602 , S 604 , S 606 , and S 608  indicate procedures of the drive apparatus. 
     In step S 601 , the type of a medium loaded into the drive apparatus is requested from the system controller and the system controller recognizes the media is the write-once pseudo-overwritable disc and recognizes that the drive apparatus supports the pseudo-overwrite function. 
     In step S 602 , the drive apparatus reads out information of the type of the loaded disc. The drive apparatus also determines whether or not the pseudo-overwrite function is supported with respect to the disc. The drive apparatus informs the system controller of these pieces of information. 
     In step S 603 , by requesting the track information of a write-once disc, the system controller obtains the information from the drive apparatus. Specifically, the size of an unrecorded area in Track # 2 , and the next writable address in the track or the last recorded address in the track are requested. In order to write the data of the file, it is necessary to get the above-described information in advance, and it is checked whether or not the unrecorded area has a prescribed size or more. Since in Track # 2  additional Metadata file may be allocated, for example, the prescribed size may be 128 MB for the disc of a whole capacity with 23 GB. If the size of the unrecorded area is less than the prescribed size, the disc is used as a read-only disc. If the size is equal to or greater than a prescribed size, the procedure goes to the next step. The size of a file entry is 2 KB. When only file entries are recorded in an available area of 128 MB, file entries corresponding to 65,536 files at most can be recorded. 
     In step S 604 , the drive apparatus reads the information related with the number of tracks, the positional information and the open/close state of each track, or the last recorded address information, from the lead-in area, DMA, or TDMA of the loaded disc. The system controller is informed of these pieces of information. 
     In step S 605 , the drive apparatus is instructed to read the Metadata Bitmap area. As a result, the system controller obtains the Metadata Bitmap, and it is checked whether or not there are available sectors. When there are available sectors, the procedure goes to the next step. When there are no available sectors, an additional area for a Metadata file is assigned in the unrecorded area of Track # 2  to reserve the available sectors. In this checking, the system controller may determine whether the additional area for a Metadata file is reserved or not, by using the prescribed size for the available sectors, for example, the prescribed size may be 128 KB. 
     In step S 606 , the drive apparatus reads data from the specified area, and transfers the data to the system controller. 
     In step S 607 , by requesting spare area information to the drive apparatus, the system controller obtains the information and checks whether or not there is an unrecorded area in the spare area having a prescribed size or more. 
     For example, when the size of the unrecorded area is equal to or greater than 8 MB, the disc is usable as a recordable disc. When the size is less than 8 MB, the disc is used as a read-only disc. The spare area is used not only for pseudo-overwrite, but also for defect management. Therefore, an additional unrecorded area is needed to recover defective sectors on the disc. 
     In step S 608 , the drive apparatus reads the number of spare areas, the size of spare areas, and the size of an unrecorded area in each spare area, from the lead-in area, DMA, or TDMA of the loaded disc. The system controller is informed of these pieces of information. 
     As described above, the data is recorded in the unrecorded area in the spare area by pseudo-overwrite or defect management. The write-once disc drive apparatus of the present invention has a function to send the free area information as well as the type information of a medium to a system controller, because the drive apparatus stores the data at some location which may be different from the location the file system expects. By requesting this free area information whenever a file is recorded, the system controller decides whether the file can be recorded or not, as a result, the system controller can record a file correctly with the related data in the Metadata file. 
     Embodiment 3 
     In the previous embodiment 2, the spare area with sufficient size has to be assigned at the time of formatting on a write-once disc. However, a user cannot know how many files and the size of the files that will be recorded on the disc, therefore, it is difficult to decide the appropriate size of the spare area at the time of formatting. If all of the spare area is used, no file can be recorded on the disc, even if the unrecorded area remains in the user data area. On the other hand, if a larger spare area is assigned, after all of the user data area is used, unrecorded area may remain in the spare area. 
     Further, a file system driver has to check the size of the unrecorded area in the spare area each time when a file is recorded, hence the space management becomes difficult to implement. This is not suitable for the implementation of file system driver of computer systems. 
     So, hereinafter a recording method in which the direction to replace the data not only within the spare area but also within the user data area is explained. 
     At first, an idea of the present invention is described: 
     Devices handle the overwriting of existing data by writing the new data to the next writable block and creating an entry in a remapping table stored by the drive apparatus. The file system continues to use the same logical block number, and the drive apparatus remaps the request to the new location based on the entry in the table. In order to reduce the size of this table, the file system does not reuse blocks after they are freed. That is, the file system has to be aware that it is using write-once media, and adjust its behavior accordingly. 
     The device uses the normal volume space to store the remapped data. That is, it is writing to the next writable location within the same track that the original block exists. The file system queries the device for the next writable block whenever it needs to allocate new space. So both the file system and the device are sharing the same space for writes. 
     Secondly, the effectiveness of the above idea is described using  FIGS. 7A-7D ,  8 A- 8 B and  9 : 
       FIGS. 7A-7D  and  8 A- 8 B show the blocks in a user data area. Herein, the block is used rather than the sector to explain the idea generally. The user data area is recognized as a volume space by the file system. For each block, a Physical Block Address (hereafter described as PBA) and a Logical Block Address (hereafter described as LBA) are assigned so that the correspondence between PBA and LBA are decided in advance, wherein as an example, PBA is assigned from the number 100 and LBA is assigned from the number 0. 
       FIG. 9  shows the data structure of the remapping table stored by the drive apparatus. The table has entries, each of which specify the original address and remapping address. This data structure may be the common data structure with the defect list which is used for defect management for rewritable discs. 
     Typically, it had seemed that the above idea was not effective, because there are contradictions when applied for rewritable discs. 
     As shown in  FIG. 7A , a rewritable disc has a spare area, in which a PBA is assigned form the number  200 , for example. In a usual case for a rewritable disc, if the data are written to the blocks of LBA  2  and  5  and these blocks are defective, these data are stored into the blocks PBA  200  and  201  in the spare area using a linear replacement algorithm. This means LBA  2  and  5  is re-assigned to PBA  200  and  201 . Thus, when some block in the volume space becomes an unusable block due to defect, it is compensated with a good block in the spare area. 
     If the above idea would be applied to a rewritable disc, as shown in  FIG. 7B , the data to write LBA  2  and  5  are stored into the blocks in a user data area, for example, PBA  103  and  107 . However, these remapped blocks of PBA  103  and  107  cannot be used to store the data requested to LBA  3  and  7 , as these blocks are replaced as LBA  2  and  5 . This situation breaks the assumption to provide a defect free logical space, in which the assumption that the data capacity on the rewritable disc shall not be reduced, when any data is recorded by the file system. Further, in this situation, the drive apparatus could not decide the location to remap the data, because the file system may write the data randomly and only the file system handles the space bitmap which specifies the available area for recording. 
     As explained embodiment 1, the linear replacement algorithm can also be applied to write-once discs. As shown in  FIG. 7C , the spare area is assigned for the write-once disc in advance. If the block is overwritten or can not be written due to a defect, the block is compensated with the block in the spare area. As examples, when the data D 1  is written to LBA  2 , if the block is defective, the block is compensated with the block of PBA  200 . When LBA  5  is written by the data D 2 , even if the PBA  105  is already recorded, the data is stored into PBA  201 . 
     It is supposed that a block to be overwritten and a defective block should be compensated with another block which belongs to outside of the volume space. This idea seems to be a contradiction not only for rewritable discs, but also for write-once discs. 
     However, according to the present invention, write-once discs may not guarantee to provide defect free logical space like rewritable discs, because if a block on a write-once disc is written once, it is not possible to change the data in the block. And the new file system for write-once discs would write the data using sequential recording. On this point, this idea is effective for a write-once disc as shown in  FIG. 7D . The data D 1 , D 2  and D 3  are written to LBA  0 ,  1  and  2 , sequentially, at this time if the block PBA  102  is defective, then the data may be written to the next block PBA  103 . Further, the data D 4 , D 5  and D 6  are written to LBA  4 ,  5  and  6 , sequentially, and then the updated data D 5 ′ may be overwritten to LBA  5 . On this overwrite, the data is stored into the block PBA  107  which is the next writable location. Thus, this idea does not require changing the assignment of a logical block number, because whenever the overwritten is needed, the data can be written to next writable location until the user data area is used up. In case of a rewritable disc, the data can not be recorded into the block used for remapping, but there is no problem for the present invention of a write-once disc. For example, the data may be recorded further into the block of LBA  7 . In this case, the data is stored in PBA  108  and the entry to specify this remapping from the original address of PBA  107  to the remapping address of PBA  108  is added in the remapping table. 
     As explained above, according to the present invention, even if the Logical Block Address is double booking, the drive apparatus can record the data by assigning a new Physical Block Address to NWA. 
     Another important point to be practical to the above idea is to save the entries stored in the remapping table by querying the next writable address from the file system to the drive apparatus.  FIGS. 8A and 8B  show the mechanism to reduce the size of the table. In this figure, blocks PBA  100  to  105  are recorded in advance. As shown in  FIG. 8A , when the data D 1  is written to LBA  1 , the data is stored in next writable location PBA  106  and one entry is added to specify PBA  101  is remapped to PBA  106 . At this moment, the file system does not know where the data is remapped. If file system instructs to write the new data D 2  to the previous next writable location LBA  6 , the data is stored to the next block PBA  107  and one entry is added. In the present invention, the file system checks the updated next writable address before any data is recorded barring overwrite, and instruct to write the data at the updated next writable address, of which is LBA  7  in  FIG. 8B . Thus, an additional entry is not needed. The file system will not also reallocate the data to the deleted file area, barring the requirement to overwrite for the same reason. 
     Furthermore, the space management by the file system can be simplified, because the file system uses only NWA in each track to allocate the new area for recording. This means the file system may not be checked in the spare area, and may not record the space bitmap, especially the Metadata Bitmap. 
     The unit to remap the area may be an ECC block which consists of plural physical sectors. When a physical sector is remapped, all of the physical sectors in the ECC block in which the physical sector belongs to are remapped. In this case, the original address and remapping address in the entry of the remapping table are specified by the physical address of the start sector of each ECC block. As an addressable unit, the physical block and the logical block may be the physical sector and the logical sector. Even if one sector is newly written, one ECC block including the sector is written, then the NWA is moved to the start sector of the next ECC block. Therefore, when several data are written, these data are allocated so that these data are written with the same ECC block. 
     By the present invention, the merits to use the Metadata Partition can be provided for the use on the write-once disc. At first, the data to be overwritten is remapped within the track for metadata writing, then the access to retrieve the metadata can be localized and the performance is improved. As usual, the overwritten data is stored in the same track as long as the track has unrecorded sectors. When the track is used up by data recording, the overwritten data may be stored into the other track, as it is given the priority to write the data to the other unrecorded physical block in the same track. Secondly, a Metadata Mirror File can be recorded to improve the robustness, when an additional track for a Metadata Mirror File is assigned. 
     Herein, the potential for overwriting is estimated for the example case that the capacity of the disc is 23 GB (=23×1024^3 bytes), the ECC block consists of 32 sectors, and the sector size is 2 KB (=2×1024 bytes). If the average size of the files recorded on the disc is 128 KB and 10 files are stored in the directory on average, about 188,000 files and 18,800 directories can be recorded on the disc. When the file system clusters the file entries to be updated into an ECC block, about 6,400 entries are needed in the remapping table. The size of the table becomes about 50 KB when the size of the entry is 8 bytes. When the drive apparatus can handle 256 KB of the remapping table as the maximum size, 188,000 files and 18,800 directories would be written randomly. Thus, this invention is also practical for the next generation write-once optical discs using blue laser technology. 
     An example applying the above idea to a new file system based on UDF and the next generation write-once disc is described. 
       FIG. 10  is a diagram illustrating a configuration of areas to explain the above mentioned remapping. The area layout explained in the embodiment 1 is also used in this embodiment. 
     Defect Management Area (DMA) is an area in which the defect list is recorded and Temporary DMA (TDMA) is an area, in which a temporary defect list is recorded. The remapping table may be recorded in DMA and TDMA with the defect list and the temporary defect list. Herein, the defect list and the temporary defect list may be used to specify both the replacement information by defect management and the remapping information using the same data structure. It will help to simplify the implementation of the drive apparatus, because the interpretation of the entry is common for defect management and for pseudo-overwrite. When the entry specifies the remapping information, the entry in the table indicates the correspondence between the address of a block to be remapped and the address of a remapped block. 
     Spare areas are assigned out of a volume space, and the addresses in the spare area are indicated by SA&#39;s (Spare area Address). 
     The volume space comprises three tracks, in each of which the data is recorded sequentially. The start address of the unrecorded area in the track is managed as Next Writable Address (NWA). The status of a track is described by new terms: “Used” and “Reserved” in order to indicate the data in these tracks can be overwritten and the data may be remapped within the reserved track. The used track means that all sectors in a track have been used for data recording. The reserved track means that there is a sector(s), which has not been recorded. In other words, the data can be incrementally written into the reserved track. Since the volume structure has been previously recorded, Tracks # 1  is a used track. Track # 2  is a reserved track assigned for metadata recording. Track # 3  is a reserved track assigned for user data recording. 
     An exemplary procedure for updating Data-A file and recording Data-B file onto the write-once optical disc is described. 
     At first, the Metadata file FE is read to obtain the area allocated for the Metadata file, wherein MA (Metadata file Address) indicates a relative address within a Metadata file. 
     When the file system updates the Data-A file, the file entry is read in the memory and the file entry is updated in order to register the information to specify the location where the updated data will be written and the related information (e.g., size and updated time, etc) in the memory. The file system instructs the drive apparatus to overwrite the data of Data-A file logically. Then the drive apparatus stores the data (Data-A′) physically to the NWA, as the corresponding physical sector is already recorded and the drive apparatus adds the entry to the defect list. If the file system instructs to write the data to NWA after querying the drive apparatus, it is not required to add the entry in the defect list. In this invention, this manner to save the entry is recommended, because the location of the data can be registered in the file entry. However, when a part of the large file has to be updated, the data to be updated may be overwritten instead of writing the whole data of the file. After the data is written on the disc, the file system instructs to overwrite the file entry (Data-A′ FE) logically in order to specify the location of the written data and the updated time. Then the drive apparatus writes the data physically into the sector shown at MA #k+1 and stores the entry into the defect list. 
     When the file system newly records the Data-B file under the root directory, the directory is read into the memory and the directory is updated to add the new file (Data-B file) to this directory in the memory. Beforehand the file entry of the Data-B file is created in the memory, the data of Data-B file is written at the NWA in Track # 3 , and then the file entry (Data-B FE) and the root directory on the memory are written from the NWA shown as MA #k+2 in Track # 2 . To specify the new location of the root directory, the updated file entry for the directory is instructed to overwrite and the data is written at the NWA shown as MA #k+4. Thus, only the file entry of the directory among metadata is overwritten to save the entry, and the other metadata (the file entry of the file and the directory) and the data of the file are written without overwriting. 
     To indicate the integrity of the file structure, the updated Logical Volume Integrity Descriptor is instructed to overwrite, and the data is written at the sector SA #m in the spare area. 
     In the above pseudo-overwrite operation, the data to be overwritten may be stored within the spare area or the NWA in the reserved track in response to an instruction to write the data into an already recorded area. The destination to store the data may be decided by the drive apparatus. Similarly, the data may be replaced within the spare area or the NWA in the track by defect management, when the data can not recorded on the sector due to defect. 
     In case of rewritable discs, the file system reuses the available area. However, in the present invention the available area is not reused when the available area is used once. For example, in  FIG. 10 , although the logical sector at MA #i+1 in which the root directory was written became the available sector, the file system will not allocate any data at MA #i+1. If the data were written again into MA #i+1, the data would be remapped. In the case of the data being written on an ECC block basis, one ECC block is written, even if only one sector of the unrecorded ECC block is instructed to be written and the invalid data is recorded in the other sectors of the ECC block. The file system also will not reuse the area where the invalid data is recorded, for the same reason. 
     Hereinafter a write procedure of the present invention is described. This write procedure is performed by the optical disc information recording/reproduction system described in  FIG. 5 . 
       FIGS. 15A-15D  each comprise a diagram illustrating the blocks in a user data area, when the data is written using the pseudo-overwrite method. The user data area, PBA and LBA are the same definition as described in  FIG. 7 . 
     The procedure to update the file is described in  FIGS. 15A and 15B . As shown in  FIG. 15A , before the file is updated, the blocks PBA  100 ,  101 , and  102  are recorded. The file entry (D 3 ) of the file to be updated is stored in the block LBA  2 . As shown in  FIG. 15B , the file system; 
     1) instructs to read the file entry from LBA  2  in advance, 
     2) queries the NWA to the drive apparatus, 
     3) instructs to write the updated data (D 4 ) of the file into the NWA (LBA  3 ), so that the data is written without overwriting, and creates the file entry (D 3 ′) so that the positional information in the read file entry is changed to specify the area where the updated data is written, and then 
     4) instructs to write the updated file entry (D 3 ′) into LBA 2  so that the file entry is overwritten. 
     The procedure to record the file under the directory is described in  FIGS. 15C and 15D . As shown in  FIG. 15C , the blocks PBA  100 ,  101 ,  102 ,  108  and  109  are recorded, and two tracks are reserved. The file entry (D 1 ) of the directory and the directory (D 2 ) are stored in blocks LBA  0  and  1 . As shown in  FIG. 15D , the file system; 
     1) instructs to read the file entry of the directory and the directory from LBA  0 , 
     2) instructs to read the directory from LBA  1 , 
     3) queries the NWA of each track to the drive apparatus in order to decide the location to write the data without overwriting,
         3-1) creates the file&#39;s file entry (D 6 ) which has the positional information of the area allocated for the data of the file,   3-2) creates the directory (D 7 ) so that the new file is registered in the read directory (D 2 ) and   3-3) creates the file entry (D 1 ′) of the directory so that the positional information in the read file entry (D 1 ) is changed to specify the area where the updated directory is allocated,       

     4) instructs to write the data (D 5 ) of the file into NWA in Track # 2  (LBA  10 ), 
     5) instructs to write the file entry (D 6 ) of the file from the NWA in Track# 1  (LBA 3 ) 
     6) instructs to write the directory (D 7 ) to the next address so that the data is written continuously, and then 
     7) instructs to write the updated file entry (D 1 ′) into LBA 0  so that the file entry is overwritten. 
     Thus, before any data is written, the file system queries the NWA. This is because the NWA may be changed, as the drive apparatus would write the data with remapping on its own. Next, the file system provides an instruction to write the data from NWA so that the data is written without being overwritten. Then, the file system instructs that the updated data be written with overwriting. This order to write the data is important, to save the entry in the remapping table. 
     In the case of  FIG. 15B , if the write procedure was not in this order, namely the data D 3 ′ is overwritten before the data D 4  is written, the data D 3 ′ would be written into PBA  103  and the NWA is changed. This means the data D 4  would be written with overwriting into LBA  3 , but the data would be remapped into PBA  104 . In the case of  FIG. 15D , if the write procedure were not in this order, an additional entry would be added in the remapping table, as well. 
     In the case of rewritable discs, there are no such requirements. Typically, a different order is used for the rewritable disc cases to improve the reliability, considering the recovery when a write procedure may terminate accidentally. On the other hand, in the case of write-once disc such recovery is not important; rather, it is important to save the entry in the remapping table, because the previous state remains by the write-once feature. 
       FIGS. 11A and 11B  each comprise a flowchart illustrating a procedure to write the data on a write-once optical disc. This write procedure is performed by the optical disc information recording/reproduction system described in  FIG. 5 . 
     When the file is updated, the file system will instruct to write the data of the file so that the data is written without overwriting, and the file system will create the file entry by updating the written file entry and will instruct to write the file entry so that the file entry is overwritten. 
     When a new file is recorded under the directory, the file system creates the file entry of the file and creates the directory and the file entry of the directory by updating the written directory and it&#39;s file entry in the memory and instructs to write the data of the file, the file entry and the directory so that these data are written without overwriting. Then the file system will instruct to write the file entry of the directory so that the file entry is overwritten. 
       FIG. 11A  shows the steps involved in the procedure to write the data on a write-once optical disc. A program is used to implement the procedure and is executed by controller  511  contained in the system controller  510 . The system controller  510  instructs the drive apparatus  520  to write the data on a write-once optical disc. The controller  511  may include a semiconductor integrated circuit. The program is provided in various manners. For example the program may be provided in a form of a computer readable medium having the program recorded thereon. Alternatively, the program may be provided by downloading the program from a server via the internet. Once the program is installed into a computer, the computer functions as the system controller  510 . 
       FIG. 11B  shows the procedure performed by the drive apparatus  520 . 
     In step S 1101 , the system controller  510  receives a write request which specifies at least data for a file to be written from the user. For example, the request is to replace Data-A file as new data or to copy Data-B file from the other media to under the root directory on this disc. The data to be written is transferred to the memory  512  in the system controller  510  and the destination to record the data is indicated by the pathname in the directory tree structure. 
     In step S 1102 , the controller  511  instructs the drive apparatus  520  to read the metadata for managing the directory or file which is requested by user. The metadata such as file entry and directory are read from the Metadata File. 
     In step S 1103 , the controller  511  queries a next writable address NWA, which indicates a location at which data is to be written next, to the drive apparatus  520  before it instructs the drive apparatus  520  to write the data, because there is a possibility that the drive apparatus  520  will move the NWA. The drive apparatus  520  sends the queried NWA to the system controller  510  and the system controller  510  sends the NWA to the controller  511 . 
     In step S 1104 , in response to the user write request, the controller  511  creates or updates at least a part of the metadata so that the data amount to be overwritten is minimized by distinguishing the type of the data to be written. As described in the explanation for  FIG. 10 , in the case of a file is updated, the file system creates the file entry to specify the location of the data to be written. This file entry is the data to be overwritten. In the case a new file is recorded under the directory, the file system creates the file entry of the new file and updates the directory to register the new file and the file entry of the directory. The file entry of the directory is the data to be overwritten and the other metadata is the data which can be written without being overwritten. As examples of the updated metadata, the updated metadata may include a file entry of a directory under which the file is recorded, or a file entry of the file 
     In step S 1105 , the controller  511  instructs the drive apparatus  520  to write the data, which is not needed to be overwritten, at a location indicated by the NWA. 
     In step S 1106 , the controller  511  instructs the drive apparatus  520  to write at least a part of the updated metadata at the location from which the metadata was read so that the data is overwritten on the logical sector. In step S 1105  and S 1106 , the same write command can be used to instruct to write the data, because the drive apparatus  520  can determine whether the data should be written with overwrite or without by checking the status of the logical sector in step S 1111 . In steps S 1105  and  51106  data is written to different addresses which are indicated in different manners, for example, step S 1105  writes the data specified by a user write request (step S 1101 ), while set S 1106  writes the metadata which has been read (step S 1102 ). To avoid possible errors step S 1106  is performed after step S 1105 . 
     In step S 1111 , the drive apparatus  520  receives the write command, which specifies at least a logical sector in which the data is to be written, from the controller  511  and determines whether the physical sector to which the logical sector corresponds in advance is recorded or not. In this check, the drive apparatus  520  judges the state of the physical sector using the logical sector number which is instructed to write by the controller  511 . When the logical sector number is smaller than the NWA, the physical sector is recorded, or else unrecorded. If the physical sector is unrecorded, go to S 1112 , else (if recorded) go to S 1113 . 
     In step S 1112 , the drive apparatus  520  writes the data to the physical sector that corresponds to the logical sector in advance. 
     In step S 1113 , the drive apparatus  520  writes the data to the other unrecorded physical sector. When the data is remapped on an ECC block basis, the other unrecorded physical sector is one of the sectors belonging to the ECC block which is the next writable block. For example, in case the ECC block consists of 32 sectors, the second sector in the ECC block is instructed to be overwritten, the data is physically written into the second sector in the next writable ECC block. Thus the relative address within the ECC block is kept for the remapped ECC block. 
     In step S 1114 , the drive apparatus  520  creates the entry as the remapping information to specify the original address related with the physical sector corresponding to the logical sector in advance and the remapping address related with the physical sector in which the data is written, and stores the remapping information to the defect list/remapping table. In case the ECC block consists of 32 sectors, the original address is the start address of the ECC block to which the original physical sector belongs and the remapped address is the start address of the ECC block to which the remapped physical sector belongs. 
     When this invention is applied to the recording/reproduction system such as a consumer video recorder or a consumer video player, the file system and the drive apparatus may be controlled by the common micro processor as shown in  FIG. 12 . In this case, the file system may not query the NWA to the drive apparatus, because the recording/reproduction system knows the NWA. At first, the NWA in each track is checked when the disc is loaded in the drive unit, then this system can manage the NWA after some data is written. 
       FIG. 12  shows an optical disc information recording/reproduction system  1200  which is a part of a consumer video recorder or a consumer video player. The information recording/reproduction system  1200  includes a controller  1211 , a memory  1212  and a drive mechanism  523  for reading and writing information from and onto an optical disc. The controller  1211  may be, for example, a semiconductor integrated circuit such as a CPU (Central Processing Unit) and performs the method described in the embodiments of the present inventions. Further, a program for causing the controller  1211  to perform the method described in the embodiments is stored in the memory  1212 . In the controller  1211 , a file system, a utility program, or a device driver may be performed. The drive mechanism  523  may be controlled by the controller  1211 . 
       FIG. 13  is a flowchart illustrating a procedure to write the data on a write-once optical disc by the recording/reproduction system explained in  FIG. 12 . 
     In step S 1301 , the controller  1211  receives the request from the user. For example, the request is to replace Data-A file as new data or to copy Data-B file form the other media to the root directory on this disc. The data to be written is transferred to the memory  1212  and the destination to record the data is indicated by the pathname in the directory tree structure. 
     In step S 1302 , the file system read the data to retrieve the directory or file which is requested by user. The metadata such as file entry and directory are read from the Metadata File. 
     In step S 1303 , the file system gets the NWA before writing the data. 
     In step S 1304 , in response to the user requests, the file system creates some of the metadata so that the data amount to be overwritten is minimized by distinguishing the type of the data to be written. As described in the explanation for  FIG. 10 , in the case of a file being updated, the file system creates the file entry to specify the location of the data to be written. This file entry is the data to be overwritten. In the case of a new file being recorded under the directory, the file system creates the file entry of the new file and updates the directory to register the new file and the file entry of the directory. The file entry of the directory is the data to be overwritten and the other data is the data which can be written without being overwritten. The data type is distinguished as type I: no need to be overwritten and type II: needs to be overwritten. 
     In step S 1305 , the file system instructs to write the type I data into the logical sector from the NWA. Then, go to step S 1311  which is the operation to write the data of type I. 
     In step S 1306 , the file system instructs to write the type II data into the logical sector. Then go to step S 1321  to perform the operation to overwrite the data in the logical sector. The write command instructed to write the data may be different for type I and II. 
     In step S 1311 , the data is written to the physical sector which corresponds to the logical sector in advance. 
     In step S 1321 , the data is logically overwritten in the logical sector and physically written into the other unrecorded physical sector, especially to the NWA. 
     In step S 1322 , the entry as the remapping information is created to specify the original address of the physical sector corresponding to the logical sector in advance and the remapping address of the physical sector in which the data is written, and is stored to the defect list. 
     The reproduction procedure from the write-once disc on which disc the data is written using the above explained methods  FIGS. 11A ,  11 B and  13  is explained hereinafter.  FIG. 14  is a flowchart illustrating a procedure to read the data from a write-once optical disc by the recording/reproduction system explained in  FIGS. 5 and 12 . Wherein, the recording/reproduction system receives a read instruction which specifies at least a logical sector from which data is to be read. 
     In step S 1401 , the original addresses of all entries stored in the remapping table are searched. As the logical sector number to be read is instructed, the physical sector number which corresponds to the logical sector in advance is used to search the entry which indicates the physical sector is remapped. When the remapping is performed on an ECC block basis, the start address of the ECC block is registered in the entry. In this case, it is checked whether the physical sector number belongs to the remapped ECC block or not. This operation may be done by a drive apparatus in case of an Information recording/reproduction system as described in  FIG. 5 . 
     In step S 1402 , if the entry is found, go to step S 1403 , else step S 1404 . 
     In step S 1403 , the original address of the physical sector is replaced with the remapping address of the physical sector, which is indicated in the found entry. If the entry is not found in step S 1402 , then the address to be read is determined as the address of the physical sector corresponding to the logical sector specified by the read instruction. If the entry is found in S 1402 , then the address to be read is determined as the remapping address corresponding to the original address found in the remapping table. 
     In step S 1404 , the data is read at the determined address. 
     As explained above, when the address is not found, the data is read from the physical sector corresponding to the logical sector in advance, because the remapping table shows the data stored in the logical sector is not remapped to the other physical sector. 
     When the address is found, the data is read from the physical sector specified by the remapping address in the found remapping information, because the entry found in the remapping table shows the data stored in the logical sector is remapped. 
     If the data is remapped within the volume space, especially to the NWA in the track rather than into the spare area, the data can be read out more quickly. 
     As described in the above embodiments, this invention can be applied to the drive apparatus on the assumption that the file system minimizes the data amount to be overwritten and the file system instructs to write the data to unrecorded sector by querying the drive apparatus, when the data is written without being overwritten. 
     Embodiment 4 
     In this embodiment, as an example, guidelines and requirements are described for the UDF file system implementation. 
     (Benefits to Using A Pseudo-Overwrite Method) 
     In order to reduce complexity due to physical characteristics, new sequential recording media with overwritable features are introduced as pseudo-overwritable media. The pseudo-overwrite method is applied to this pseudo-overwritable media. The following sets forth some of the benefits of introducing the new sequential recording media: 
     1) An overwritable volume space and a defect free space are provided, similar to a rewritable media. In other words, compatibility due to write-once media is ensured by a drive unit which supports an overwritable mechanism and defect management. 
     2) Session close and Border close are not necessary, as a read-only drive unit supporting Pseudo-overwrite media has access to an unrecorded area. 
     3) Metadata Partition and its mirror can be used. 
     (Characteristics of Pseudo-Overwritable Media) 
     The physical characteristics of pseudo-overwritable media are described from the viewpoint of what is required by the file system driver. 
     Pseudo-overwritable media supports multi-track recording and an overwritable function for the logical sectors in a volume space. More than one track can be used to record. A new track can be assigned as a reserved track. A sequential recording mode is to be used within a track, to simplify the space management. The pointer to the recordable area is Next Writable Address (NWA), which is obtained through an inquiry of a drive apparatus. 
     When the data is intended to be recorded on the recorded logical sector, the data is recorded either within the Spare Area by a linear replacement algorithm, or to NWA within the volume space. As a benefit of remapping the data to NWA within the volume space, all available media capacity can be used, even if all of the Spare Area is recorded. A read modify write operation is also supported, therefore, each logical sector can be overwritten separately. 
     The address information where the data is replaced or remapped from the original address is stored as a defect list entry of volume space and managed by a drive apparatus. 
     (Write Strategy by the File System) 
     In general, a track can be assigned by considering the data type to be recorded; for example, metadata or specific data such as audio/visual data, still picture data, music data and so forth. On multi-track recording, when a reserved track is used up, a new track is assigned, adaptable to the amount of recorded data. The track for metadata recording is explicitly indicated as an extent of a Metadata File or a Metadata Mirror File. 
     If pseudo-overwrite media has the restriction that a new track can not be assigned after a track is assigned at the end of the volume space, multi-track recording is used in an intermediate state in which only one AVDP is recorded at LSN 256. According to ECMA 167 requirements, the AVDP shall be recorded in at least two of three locations (i.e. LSN 256, LSN—256 and Last LSN). In this example, the track is assigned to record AVDP at Last LSN—256 or Last LSN. 
     A Metadata Mirror File can be also used. It is recommended to create a Metadata Mirror File when the disc is stored for archiving. In case of online usage, the implementation is to record such that the contents recorded in a Metadata File and a Metadata Mirror File have the same offset in each file, although the offset of NWA in each track sometimes may not be the same due to the recording condition of each track. 
       FIG. 16A  shows an example of a track layout after a logical format. A first volume structure including AVDP at LSN 256 and the related file structure is recorded. Then, a track is assigned for metadata recording, and the metadata is recorded in the track. The remaining area in the volume space is used for file data recording. 
       FIG. 16B  shows an example of a track layout after some files are recorded. After the first track is used up, a new track is assigned. Thus, additional tracks may be assigned one after another. 
       FIG. 16C  shows another example of a track layout after some files are recorded. When the track for metadata recording is used up, an additional area for Metadata File may be allocated in the data track as an extent, not a track. 
     (Requirements for File System) 
     Requirements for pseudo-overwrite method are listed as follows: 
     1) Implementations are to recognize Pseudo-overwritable media by inquiring to the drive unit. 
     2) An Unallocated Space Bitmap and an Unallocated Space Table shall not be recorded. 
     3) A Metadata Bitmap File shall not be recorded. 
     4) Implementation should query for NWA in each track prior to writing additional data. If a write command is issued to an already-recorded area, the defect list entry is used. Therefore, this requirement is important to reduce an unnecessary defect list entry, as the size of defect list is limited. 
     5) Deleted blocks should not be reused to query NWA for the same reason. 
     6) The metadata to be overwritten should be minimized. It is recommended that only the directory File Entry should be overwritten. 
     INDUSTRIAL APPLICABILITY 
     The present invention is useful to provide a recording method for a write-once disc using a logical overwritable mechanism, and a semiconductor integrated circuit for use in the recording apparatus or the reproduction apparatus.