Patent Publication Number: US-7593622-B2

Title: Information recording medium, information recoding/reproduction system apparatus, and information recording/reproduction method

Description:
This is a continuation of commonly assigned application Ser. No. 09/603,776, filed on Jun. 26, 2000 now U.S. Pat. No. 6,788,876. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an information recording medium, an information recording/reproduction system apparatus and an information recording/reproduction method for managing AV (audio/video) data by using a file structure. 
   2. Description of the Related Art 
   An optical disk is a type of information recording medium which has a sector structure. In recent years, the recording density and the capacity of an optical disk have been increased, and optical disks usable in multimedia applications have been developed. Accordingly, it has become important to increase the access speed so that it is possible to interactively reproduce data using a plurality of data sets. A DVD-video disk has been developed as an optical disk capable of interactively reproducing video titles. A DVD-video disk contains AV data which includes a plurality of MPEG program streams and control data which is used for controlling the reproduction of the AV data. 
   Referring to a directory structure illustrated in  FIG. 9  and a data structure illustrated in  FIG. 10 , the structure of directories recorded on a DVD-video disk and the relationship between the AV data and the control data will now be described by way of an example. A DVD-video file  908  is recorded using a predetermined file name under a predetermined directory so that a DVD player can easily access data. In particular, a video directory  902  is created under a root directory  901 . 
   The DVD-video file  908  includes AV data  907  and control data  906 . The AV data  907  and the control data  906  are recorded under the video directory  902 . In particular, the AV data  907  is recorded as a file  904  named “Video.AVD”, and the control data  906  therefor is recorded as a file  903  named “Video.IFO”. A file  905  named “File-A.DAT”, which is used in personal computers, and the like, is recorded in a location other than under the video directory  902 . Therefore, the DVD player will not erroneously reproduce PC data. 
   Typically, the AV data  907  includes a plurality of video objects (hereinafter, referred to as “VOBs”). In the example illustrated in  FIG. 10 , the AV data  907  includes VOB  1009  and VOB  1010 . The VOB  1009  and the VOB  1010  are both VOBs but differ from each other in terms of the conditions under which video data and audio data represented by the VOBs are compressed or encoded. For example, the VOB  1009  may be AV data of a news program which has been compressed by the MPEG1 data compression scheme, while the VOB  1010  may be AV data of a live baseball program which has been compressed by the MPEG2 data compression scheme. The control data  906  includes a program  1011  for controlling the reproduction of the AV data  907  and VOB management information  1012  which is used for managing the information of each VOB. The program  1011  includes a program  1001  for controlling the reproduction of the VOB  1009  and a program  1002  for controlling the reproduction of the VOB  1010 . The programs  1001  and  1002  each specify a reproduction start address  1005  and a reproduction end address  1006  of the VOB. The reproduction start address  1005  and the reproduction end address  1006  are specified, respectively, by identification information of each of the VOBs  1009  and  1010  of the AV data  907  and the number of relative bytes with respect to the leading address of each of the VOBs  1009  and  1010 . In the example illustrated in  FIG. 10 , the programs  1001  and  1002  are registered. The program  1001  is programmed to reproduce a portion  1007  of the VOB  1009 , and the program  1002  is programmed to reproduce a portion  1008  of the VOB  1010 . Thus, program data (a VOB) can be partially reproduced by specifying the reproduction start address and the reproduction end address of the VOB. VOB management information  1012  includes VOB management information  1003  for managing the information of the VOB  1009  and VOB management information  1004  for managing the information of the VOB  1010 . Each of the VOB management information  1003  and  1004  includes various information for the VOB such as the type of TV broadcasting system, the resolution, the number of channels for audio data, the compression schemes for video data and audio data, information used for performing a search by specifying the time of AV data, information used for managing location information by GOPs (groups of pictures) defined in MPEG, and the data size of the VOB. A DVD-video disk having recorded thereon information which has the directory structure illustrated in  FIG. 9  and the data structure illustrated in  FIG. 10  is reproduced as follows. Application software can read out the control data  906  and interactively reproduce a plurality of VOBs by using a predefined program. 
   Referring to  FIGS. 7A and 7B , the relationship between the physical structure of a DVD-RAM disk  700 , which is a rewritable optical disk, and the logical volume space thereof will now be described.  FIG. 7A  illustrates the physical structure of the DVD-RAM disk  700 . The DVD-RAM disk  700  includes a lead-in area  701 , a DMA (defect management area)  702  for managing defects on the disk  700 , a data area  718 , and a lead-out area  716  which are arranged in this order from the inner periphery to the outer periphery of the DVD-RAM disk  700 . Digital data is recorded in each of these areas, and the digital data is managed by a unit called a “sector”. The data area  718  includes a spare area  703  used for replacing defective sectors and an area  719  including a plurality of zones numbered from zone  0  to zone  47 . In each zone, data is recorded in blocks of 2048-byte physical sectors. 
   Referring to  FIG. 7B , the physical sectors are numbered with physical sector numbers (PSNs) starting from the inner periphery of the disk  700 . Physical spaces  717  of the disk  700  are specified by PSNs. On the other hand, the space in which user data can be recorded is defined as a volume space  720  which includes a plurality of sectors which are numbered with logical sector numbers (LSNs). In other words, the volume space  720  is equal to the physical space  717  minus the lead-in area  701 , the DMA  702 , the spare area  703 , a defective sector  711 , a guard area  715  provided between two adjacent zones, and the lead-out area  716 . The defective sectors  711  are sectors which have been detected as being defective by a certification operation performed during an initialization of the disk  700 . The PSNs of the defective sectors  711  are registered and managed in a PDL (primary defect list) (not shown) provided in the DMA  702 . A defective sector  721  which have been detected as being defective while recording data onto the disk  700  are replaced with spare sectors from the spare area  703  by a linear replacement method and registered in an SDL (secondary defect list) (not shown) provided in the DMA  702 . 
   Next,  FIG. 8  illustrates an example of a data structure which would result when the various files as mentioned above are recorded on the rewritable disk  700  by using a volume file structure  800  as defined in the ECMA 167 standard. The upper portion and the lower portion of  FIG. 8  correspond to the inner periphery and the outer periphery of the disk  700 , respectively. Sectors in the volume space  720  are numbered with the logical sector numbers (LSNs) starting from the leading sector of the volume space  720 . A volume structure area  801  includes recorded therein information which is used for logically handling the disk  700  as a volume, as well as location information of a space bit map  821 , and location information of a file entry  822  of the root directory. While the file set descriptor is defined as a file structure according to the ECMA 167 standard, the file set descriptor is treated herein as a volume structure for the sake of simplicity. It is also assumed herein that files are accessed by using their logical sector numbers for the sake of simplicity, though they are typically accessed by using their logical block numbers. 
   A file structure area  802  is an area in which a descriptor for defining the file structure is recorded. The file structure area may be recorded in a distributed manner in the volume space  720 . The space bit map  821  is a bit map which is used for managing, by blocks of sectors, free areas in the volume space  720  to which a file structure or data can be allocated. The space bit map  821  includes location information of unallocated areas  805  and  807 . The file entry  822  includes a descriptor tag  851  indicating that the descriptor is a file entry, attribute information  852  which specifies attribute information of the file used by the file system, e.g., the recording date, and an allocation descriptor  853  for managing the recording location information of a file or a directory. The allocation descriptor  853  has the same data structure as that shown for an allocation descriptor  834 . A series of continuous areas in which data is recorded is called an “extent”. An extent is specified by a length  865  thereof and a start location  866  thereof. A directory includes one or more file identifier descriptors, and a file identifier descriptor is recorded for every sub-directory or file which is registered in the directory. A file identifier descriptor  823  includes a descriptor tag  854  indicating that the descriptor is a file identifier descriptor, a file name  855  which specifies a file or a directory, and location information  856  of the file entry. Since the root directory  901  ( FIG. 9 ) includes the video directory  902  and the File-A.DAT file  905 , the file identifier descriptors  823  and  824  are recorded for the video directory  902  and the File-A.DAT file  905 , respectively. Similarly, other directories and files are managed by file identifier descriptors and file entries  825  to  830 . 
   Next, a method for managing the AV data  907  will be described. Typically, AV data has a large data size and is divided into a plurality of portions which are recorded in a plurality of areas on the disk in a distributed manner. For example, when AV data having an average data rate of 5 Mbps (megabits/sec) is recorded for one hour, the size of the recorded data will be 2 GB (gigabytes). Moreover, after repeatedly editing, deleting and adding data, the free areas are typically scattered on the disk. On such a disk whose free areas have been scattered, new AV data is recorded in a distributed manner in a plurality of extents. In  FIG. 8 , the AV data is recorded in a distributed manner in extents  837 ,  839 ,  841  and  842 . In such a case, since the volume file structure  800  does not manage the contents of the data to be recorded, a portion of a VOB  881  and a portion of a VOB  882  near the boundary therebetween will be recorded in the same extent (extent  841 ). The location information of these extents  837 ,  839 ,  841  and  842  is recorded in an allocation information area  803  by using allocation descriptors. Since an AV file, as compared to other files, requires a larger number of allocation descriptors to be registered, it may not be possible to register all the allocation descriptors in the file entry  830  which is limited to a size of 1 sector or less. Therefore, location information of the new allocation information area  803  is registered in the location information  862  of the allocation information area in the file entry  830 . The allocation information area  803  has an allocation extent descriptor  831  in the leading position therein, followed by allocation descriptors  832 ,  833 ,  834  and  835  which are continuously registered immediately after the allocation extent descriptor  831 . The allocation extent descriptor  831  has a descriptor tag  863  indicating that the descriptor is an allocation extent descriptor and a length  864  of the allocation descriptor which is registered immediately after the allocation extent descriptor  831 . The allocation descriptors  832 ,  833 ,  834  and  835  specify the respective extents  837 ,  839 ,  841  and  842  of the AV data  907  by the length  865  and the start location  866  thereof. 
   Next, a method for reproducing the AV data  907  based on the programs  1001  and  1002  of the control data  906  will be described. The programs  1001  and  1002  specify the reproduction start address  1005  and the reproduction end address  1006  of the VOB by the relative address of the AV data  907  with respect to the leading address of the AV data  907 . Therefore, in order to find the recording location of the AV data to be actually reproduced, the allocation descriptor in the allocation information area  803  is read out and the logical sector number is calculated therefrom. The reproduction start location is obtained by adding together the lengths  865  of the extents which are registered in the allocation descriptors sequentially starting from the allocation descriptor  832 . In particular, when the accumulated length equals the reproduction start location in the AV data, the logical sector number at that time represents the reproduction start location on the disk. The AV data is reproduced by using the allocation descriptor which corresponds to the logical sector number thus obtained. The reproduction end location is calculated in a manner similar to that for the reproduction start location. The reproduction of the AV data ends when the accumulated length of the extents  837 ,  839 ,  841  and  842  equals the reproduction end address. 
   However, with the above-described volume file structure  800 , the reproduction of AV data may be discontinuous when the AV data is edited because the data rate information of the recorded areas is not managed. If a table for managing the data rate is created for every recorded area, the size of the table information will be large such that it cannot be managed by a consumer product whose memory size is limited. 
   SUMMARY OF THE INVENTION 
   According to one aspect of this invention, there is provided an information recording medium in which data is recorded by using a data structure, the data structure including a file structure area and a data area. The data includes first AV data having a first attribute and second AV data having a second attribute which is different from the first attribute. The data area has continuous areas. At least one of the continuous areas includes a first extent in which at least a portion of the first AV data is recorded and a second extent in which at least a portion of the second AV data is recorded. 
   In one embodiment of the invention, the file structure area includes an allocation information area in which a first allocation descriptor and a second allocation descriptor are recorded, the first allocation descriptor and the second allocation descriptor respectively representing locations of the first extent and the second extent in which the first AV data and the second AV data are recorded. 
   In one embodiment of the invention, each of the first AV data and the second AV data, which are recorded/reproduced by blocks of sectors, is recorded as a file by using the file structure. 
   In one embodiment of the invention, a file entry is recorded in the file structure area, the file entry representing information which specifies the first and second allocation descriptors. 
   In one embodiment of the invention, the first allocation descriptor includes information representing a length of the first extent and information representing a start location of the first extent. The second allocation descriptor includes information representing a length of the second extent and information representing a start location of the second extent. 
   In one embodiment of the invention, each of the first AV data and the second AV data has pack header and packet data for every sector. 
   In one embodiment of the invention, a difference between first time information and second time information recorded in a leading sector and a last sector, respectively, of the extent and a data size of AV data recorded in the extent represent an average data rate which is required for a transfer of the AV data recorded in the extent. 
   In one embodiment of the invention, the pack header includes time information representing a time relating to a transfer of the packet data. 
   According to another aspect of this invention, there is provided a data recording method for recording data on an information recording medium in which the data is recorded by using a data structure, the data structure including a file structure area and a data area. The data includes first AV data having a first attribute and second AV data having a second attribute which is different from the first attribute. The data area has continuous areas. At least one of the continuous areas includes a first extent in which at least a portion of the first AV data is recorded and a second extent in which at least a portion of the second AV data is recorded. The file structure area includes an allocation information area in which a first allocation descriptor and a second allocation descriptor are recorded, the first allocation descriptor and the second allocation descriptor respectively representing locations of the first extent and the second extent in which the first AV data and the second AV data are recorded. The data recording method includes: a first step of recording the first AV data and the second AV data in the first extent and the second extent, respectively; a second step of creating the first allocation descriptor and the second allocation descriptor; and a third step of recording the first allocation descriptor and the second allocation descriptor in the allocation information area. 
   According to still another aspect of this invention, there is provided a data editing method using an information recording medium in which data is recorded. The data includes AV data which is recorded/reproduced by blocks of sectors and includes a plurality of AV data portions, the AV data portions each corresponding to one of the sectors and having time information. The data area includes first and second continuous areas, each of the first area and the second area including a plurality of the sectors for recording a plurality of the AV data portions. The data editing method includes: a first step of reading out a leading sector and a last sector of each of the continuous areas so as to obtain first time information corresponding to the leading sector and second time information corresponding to the last sector; a second step of reading out an edition point sector corresponding to a predetermined edition point so as to obtain third time information corresponding to the edition point sector; and a third step of determining whether or not the AV data is continuously reproducible based on a size of the first and second continuous areas, the first time information, the second time information, and the third time information. 
   In one embodiment of the invention, the data editing method uses a data structure, the data structure including a file structure area and a data area. The file structure area includes an allocation information area in which a first allocation descriptor and a second allocation descriptor are recorded, the first allocation descriptor and the second allocation descriptor respectively representing locations of a first extent and a second extent, the first extent and the second extent corresponding respective to the first and second continuous areas in which the AV data is recorded. The third step determines whether or not the AV data is continuously reproducible based on the first allocation descriptor, the second allocation descriptor, the first time information, the second time information, and the third time information, the first and second allocation descriptors representing location information of the first and second extents, respectively. 
   In one embodiment of the invention, the data area includes an area in which information representing locations of the first and second continuous areas is recorded as a portion of control data. The third step comprises the step of obtaining the information representing the locations of the first and second continuous areas based on the control data. 
   In one embodiment of the invention, the file structure area includes an area in which a file entry is recorded, the file entry representing the locations of the first extent and the second extent. The third step comprises a step of obtaining information representing the locations of the first extent and the second extent based on the file entry. 
   In one embodiment of the invention, the data area includes an area in which control data is recorded, the control data including information representing the locations of the first extent and the second extent. The third step comprises a step of obtaining information representing the locations of the first extent and the second extent based on the control data. 
   According to still another aspect of this invention, there is provided an information recording system apparatus for recording data on an information recording medium in which data is recorded by using a data structure, the data structure including a file structure area and a data area. The data includes first AV data having a first attribute and second AV data having a second attribute which is different from the first attribute. The data area has continuous areas. At least one of the continuous areas includes a first extent in which at least a portion of the first AV data is recorded and a second extent in which at least a portion of the second AV data is recorded. The file structure area includes an allocation information area in which a first allocation descriptor and a second allocation descriptor are recorded, the first allocation descriptor and the second allocation descriptor respectively representing locations of the first extent and the second extent in which the first AV data and the second AV data are recorded, the information recording system apparatus comprising a data recording section for recording the first AV data and the second AV data in the data area. The information recording system apparatus includes: a data recording section for recording the first AV data and the second AV data in the data area; an AV file structure processing section for creating a file entry which is used for managing the first AV data and the second AV data and recording the file entry in the file structure area; and an AV allocation structure processing section for creating the first allocation descriptor and the second allocation descriptor and recording the first allocation descriptor and the second allocation descriptor in the allocation information area. 
   According to still another aspect of this invention, there is provided an information recording system apparatus for editing data by using an information recording medium in which the data is recorded by using a data structure, the data structure including a file structure area and a data area. The data includes AV data which is recorded/reproduced by blocks of sectors and includes a plurality of AV data portions, the AV data portions each corresponding to one of the sectors and having time information. The data area includes a first extent and a second extent, each of the first extent and the second extent including a plurality of the sectors for recording a plurality of the AV data portions. The file structure area includes an allocation information area in which a first allocation descriptor and a second allocation descriptor are recorded, the first allocation descriptor and the second allocation descriptor respectively representing locations of the first extent and the second extent. The information recording system apparatus includes: an AV file structure processing section for reading out the first allocation descriptor and the second allocation descriptor from the allocation information area so as to obtain location information of the first extent and the second extent; and an AV allocation structure processing section for reading out a leading sector and a last sector of each extent so as to obtain first time information corresponding to the leading sector and second time information corresponding to the last sector. The AV allocation structure processing section reads out an edition point sector corresponding to a predetermined edition point so as to obtain third time information corresponding to the edition point sector. The AV allocation structure processing section determines whether or not the AV data is continuously reproducible based on the first allocation descriptor, the second allocation descriptor, the first time information, the second time information, and the third time information. 
   According to still another aspect of this invention, there is provided an information recording medium in which data is recorded by using a data structure, the data structure including a file structure area and a data area, wherein the data area has physically continuous areas, AV data being recorded in at least some of the physically continuous areas. 
   In one embodiment of the invention, the file structure area includes an allocation information area in which an allocation descriptor indicating a location of an extent is recorded, the extent being one of the physically continuous areas in which the AV data is recorded. 
   According to still another aspect of this invention, there is provided a data recording method for recording data on an information recording medium in which the data is recorded by using a data structure, the data structure including a file structure area and a data area, wherein the data area has physically continuous areas. The data recording method includes the steps of: recording AV data in the physically continuous areas; creating an allocation descriptor indicating a location of an extent, the extent being one of the physically continuous areas in which the AV data is recorded; and recording the allocation descriptor in the allocation information area. 
   According to still another aspect of this invention, there is provided an information recording system apparatus for recording data on an information recording medium in which data is recorded by using a data structure, the data structure including a file structure area and a data area, wherein the data area has physically continuous areas. The information recording system apparatus includes: a section for recording AV data in the physically continuous areas; a section for creating an allocation descriptor indicating a location of an extent, the extent being one of the physically continuous areas in which the AV data is recorded; and a section for recording the allocation descriptor in the allocation information area. 
   Thus, the invention described herein makes possible the advantages of providing an information recording medium, an information recording/reproduction method, and an information recording/reproduction system apparatus, which is capable of managing the data rate for every area in which AV data is recorded and with which it is possible to efficiently edit the AV data while ensuring continuous reproduction of the AV data. 
   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 block diagram illustrating a configuration of an information recording/reproduction system apparatus according to one embodiment of the present invention; 
       FIG. 2  is a flow chart illustrating a recording operation performed by using an information recording/reproduction system apparatus according to one embodiment of the present invention; 
       FIG. 3  is a data structure diagram illustrating the area configuration according to one embodiment of the present invention; 
       FIG. 4  illustrates a simulation result illustrating changes in the state of a track buffer during the reproduction of the AV data recorded on the information recording medium of the present invention; 
       FIG. 5  is a flow chart illustrating an editing operation performed by using an information recording/reproduction system apparatus according to one embodiment of the present invention; 
       FIG. 6  illustrates another simulation result illustrating changes in the state of a track buffer during the reproduction of the AV data recorded on the information recording medium according to one embodiment of the present invention; 
       FIGS. 7A and 7B  are diagrams illustrating a physical structure of a conventional information recording medium; 
       FIG. 8  is a data structure diagram illustrating the area configuration of a conventional information recording medium; 
       FIG. 9  is a diagram illustrating a conventional file directory structure; and 
       FIG. 10  is a diagram illustrating conventional data structures for control data and AV data. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Embodiments of the present invention will now be described with reference to the figures. 
   Embodiment 1 
   One embodiment of the present invention will now be described. This embodiment is directed to an information recording/reproduction system apparatus for recording/reproducing files to/from an information recording medium such as a DVD-RAM disk in which data is recorded by blocks of sectors, wherein the files are managed by using the file structure as defined in the ECMA 167 standard. The data structure of such an information recording medium will also be discussed below. 
     FIG. 1  is a block diagram illustrating the configuration of an information recording/reproduction system apparatus  400  according to the present embodiment. The information recording/reproduction system apparatus  400  includes a system control section  401 , an optical disk drive unit  407 , an encoder  408  and a decoder  409  which are connected together via an I/O bus  406 . An AV signal is input from a tuner  410  and compressed by the encoder  408  into MPEG program stream data (hereinafter, referred to as “AV data”). After being subjected to a predetermined process in the system control section  401 , the compressed data is recorded onto the disk  700  which has been loaded into the optical disk drive unit  407 . In an AV data reproduction, data of interest is read out from the disk  700  in the optical disk drive unit  407  under the control of the system control section  401 . The read AV data is converted by the decoder  409  into an AV signal, and the decoded images and sounds are reproduced by a TV  411 . The system control section  401  is implemented by a microprocessor including a control program and an arithmetic memory. The system control section  401  further includes a control data processing section  402  for processing the control data  906  ( FIGS. 9 and 10 ) which is used for controlling the reproduction of the AV data, a control data memory  403  for storing the control information, a file system processing section  404  for processing file structure information, and a file system memory  405  for storing the processed information. The memories  403  and  405  may be provided by dividing one memory circuit into two sections. The control data  906  has a data structure as described earlier with reference to  FIG. 10 . The control data processing section  402  includes a program processing section  421  for processing a program and a VOB information processing section  422  for processing information of VOBs. The control data memory  403  includes a program memory  431  and a VOB information memory  432 . The file system processing section  404  includes a file structure processing sections  441  and  442 , an AV file structure processing section  443 , an AV allocation structure processing section  444 , a data recording section  445 , and a data read section  446 . In order to store information processed through these sections, the file system memory  405  includes a file structure memory  451 , an AV allocation structure memory  452 , and a track buffer  453 . 
   A recording operation using the information recording/reproduction system apparatus  400  for recording the AV data  907  and the associated control data  906  onto an information recording medium in which only the File-A.DAT file has been recorded under the root directory  901  in the directory structure diagram illustrated in  FIG. 9  will be described below. 
     FIG. 3  illustrates a data structure  100  after the video directory  902 , the Video.IFO file  903  and the Video.AVD file  904  have been recorded under the root directory  901  (as shown in  FIG. 9 ) in a manner as shown in the recording operation flow chart of  FIG. 2 .  FIG. 3  illustrates a physical space in order to clearly show physically continuous areas for reproducing AV data. 
   When the disk  700  is inserted into the optical disk drive unit  407  and the user instructs system control section  401  to record AV data, the file system processing section  404  is activated. First, an instruction is made to read out a volume structure area  101  from the disk  700  to the optical disk drive unit  407  by using the data read section  446 , and the read information is stored in the file structure memory  451 . The file structure processing section  441  analyzes the volume structure and successively reads out information in a file structure area  102  to the file structure memory  451  starting from the information of a space bit map  121 . At this time, the file structure processing section  441  inquires of the optical disk drive  407  location information of the defective sectors  711 ,  721  registered in PDLs or SDLs and location information of the guard area  715  between two adjacent zones as non-data area information which cannot be seen from the volume space of the disk inserted in the optical disk drive  407 . The non-data area information obtained from the optical disk drive  407  is read out to the program memory  431  (“start-up” step: S 501  in  FIG. 2 ). 
   In order to continuously reproduce AV data  183 , the AV allocation structure processing section  444  searches for a free area having a predetermined size, e.g., equal to or greater than 5 MB, based on the information of the space bit map  121  and registers AV data areas  105 ,  107 ,  109  and  110  in the AV allocation structure memory  452  as AV recordable areas. At this time, the AV recordable area is divided along this boundary if the AV recordable area includes any non-data areas which are physically managed even if the AV recordable area has continuous logical sector numbers (“search for AV allocation area” step: S 502  in  FIG. 2 ). 
   Although not shown, when the user instructs the system control section  401  to start recording AV data, the AV data is transmitted from the tuner  410  via the encoder  408  and recorded in the previously found AV recordable areas (the AV data areas  105 ,  107 ,  109  and  110 ). In particular, a VOB  181  is recorded in extents  137 ,  139  and  141 . The VOB  181  includes a program stream, and therefore has a pack header  170  and packet data  171  for every logical sector. In the pack header  170 , a SCR (system clock reference) is recorded as information representing the amount of time required for a transfer of the packet data  171  to the decoder  409 . During reproduction, each sector is transferred to the decoder  409  within the amount of time indicated by the SCR so as to ensure continuous decoding of AV data (“record VOB data” step: S 503  in  FIG. 1 ). 
   The VOB information processing section  422  stores in the VOB information memory  432  parameters for the compression of AV data, the data size of each GOP as defined in MPEG, and the reproduction time information, which have been output from the encoder  408 , and creates the information of the control data of the VOB  181  (“create VOB information” step: S 504  in  FIG. 1 ). 
   The AV allocation structure processing section  444  creates an allocation extent descriptor  131  and allocation descriptors  132 ,  133  and  134  corresponding to the extents  137 ,  139  and  141 , respectively (“create AV allocation structure” step: S 505  in  FIG. 1 ). 
   The VOB information processing section  422  determines whether it is necessary to record another VOB (step: S 506  in  FIG. 1 ). If the VOB recording has been finished (“Yes” in S 506 ), the process proceeds to step S 507 . If it is necessary to record another VOB (“No” in S 506 ), the steps from S 503  to S 505  are performed. For example, when a live baseball program is to be output from the tuner  410  following a news program, the news program and the live baseball program are recorded as the VOB  181  and the VOB  182 , respectively (step of determining whether VOB data recording has been finished: S 506 ). 
   The VOB  182  is recorded as an extent  142  and an allocation descriptor  135  of the VOB  182  is created in a manner similar to that for the extents  137 ,  139  and  141 . The extents  141  and  142  are physically a single continuous area. However, this single continuous area is divided into the extents  141  and  142  along the boundary between the VOB  181  and the VOB  182  (S 503  to S 505 ). 
   The VOB information processing section  422  confirms the recording of the VOB  182 , after which the file system processing section  404  is activated. The AV allocation structure processing section  444  records the information of the AV allocation structure memory  452  in an AV allocation information area  103  (“record AV allocation structure”step: S 507  in  FIG. 2 ). 
   The AV file structure processing section  443  creates a file entry of an AV file in the file structure memory  451  so as to manage the AV data, and records the file entry in a file entry area  130  (“record AV file structure” step: S 508  in  FIG. 2 ). 
   The program processing section  421  creates, and stores in the program memory  431 , a program in which the user specifies a portion or portions of the recorded AV data to be reproduced or the order of reproduction for the portions to be reproduced (“create program information” step: S 509  in  FIG. 2 ). 
   The control data processing section  402  records the information of the program memory  431  and the VOB information memory  432  as control data  136  in a data area  104  (“record control data” step: S 510  in  FIG. 2 ). 
   In order to manage the control data  136  as the Video.IFO file data, the file structure processing section  442  creates a file entry on the file structure memory  451 , and records a file entry  129  in the file structure area  102 . Moreover, a directory for managing an AV file and the associated control file is recorded in the file structure area  102  as a sub-directory under the root directory, and a file identifier descriptor  123 , a file entry  126 , and file identifier descriptors  127  and  128  are recorded (“record main file structure” step: S 511  in  FIG. 2 ). 
   The AV allocation information area  103  may be recorded in the file entry area  130  if the file entry thereof is of a size less than or equal to 1 sector. 
   Next, a method for continuously reproducing AV data will be described with reference to  FIGS. 1 and 4 . Referring to  FIG. 1 , the data (an MPEG signal) read out from the disk  700  in the optical disk drive unit  407  is once stored in the track buffer  453 . Then, the MPEG signal is decompressed by the decoder  409  into a video signal which is in turn displayed as an image on the TV  411 . 
   Referring to  FIG. 4 , the AV data is read out from continuous areas of the disk  700  at a constant data rate Vr (data reading rate of the optical disk drive  407 ), and stored in the track buffer  453 . The AV data stored in the track buffer  453  is transferred to the decoder  409  at a AV data transfer rate Vo. Since the AV data transfer rate Vo is less than the data rate Vr, the AV data is stored in the track buffer  453  at a rate of Vr-Vo. When the optical disk drive  407  accesses an area other than the AV data areas  105 ,  107 ,  109  and  110 , the AV data transfer into the track buffer  453  discontinues. Therefore, the amount of the AV data in the track buffer  453  decreases at a rate of Vo. 
     FIG. 4  illustrates changes in the amount of data in the track buffer  453  during the reproduction of the AV data from the extents  137  to  142  illustrated in  FIG. 3 . The AV data transfer rate for each of the extents  137 ,  139 ,  141  and  142  can be obtained based on: the difference between the SCR recorded in the leading sector of each of the extents and the SCR recorded in the last sector of each of the extents; and the data size of the AV data recorded in each of the extents. 
   Since the contents of the AV data recorded in the extent  141  and the contents of the AV data recorded in the extent  142  are different from each other, the SCR recorded in the last sector of the extent  141  and the SCR recorded in the leading sector of the extent  142  are not related with each other. 
   The AV data transfer rate for the extent  137  is obtained based on SCR( 1 ) and SCR( 2 ) which are recorded in the leading sector and the last sector, respectively, of the extent  137 . The AV data transfer rate for the extent  139  is obtained based on SCR( 3 ) and SCR( 4 ) which are recorded in the leading sector and the last sector, respectively, of the extent  139 . The AV data transfer rate for the extent  141  is obtained based on SCR( 5 ) and SCR( 6 ) which are recorded in the leading sector and the last sector, respectively, of the extent  141 . The AV data transfer rate for the extent  142  is obtained based on SCR( 7 ) and SCR( 8 ) which are recorded in the leading sector and the last sector, respectively, of the extent  142 . 
   The AV data transfer rates for the extents  137 ,  139 ,  141  and  142  are hereinafter denoted as Vo( 1 ), Vo( 2 ), Vo( 3 ) and Vo( 4 ), respectively. 
   In a time period T 1  to T 2  during which the AV data is read out from the extent  137 , the AV data is stored in the track buffer  453  at a rate of Vr-Vo( 1 ). Then, in a time period T 2  to T 3  during which the drive  407  accesses an unallocated area  106 , the operation of reading out the AV data from the extents discontinues. Therefore, the AV data in the track buffer  453  is consumed at a rate of Vo( 1 ). Similarly, in a time period T 3  to T 4  during which the AV data is read out from the extent  139 , the AV data is stored in the track buffer  453  at a rate of Vr-Vo( 2 ). In a time period T 4  to T 5  during which the drive  407  accesses a data area  108 , the AV data in the track buffer  453  is consumed at a rate of Vo( 2 ). In time periods T 5  to T 6  and T 6  to T 7  during which the AV data is read out from the extents  141  and  142 , respectively, the AV data is stored in the track buffer  453  at a rate of Vr-Vo( 3 ) and at a rate of Vr-Vo( 4 ), respectively. Thus, it is possible to ensure the continuous reproduction of AV data as long as the amount of data in the track buffer  453  does not decrease to zero. 
   Next, specific criteria which are used for determining whether AV data recorded in two areas can be continuously reproduced will be discussed. 
   The minimum physically continuous extent length N_ecc required for continuous reproduction of AV data can be expressed as follows:
 
 N   —   ecc≧Vo×Tj /((16×8×2048)×(1− Vo/Vr ))   (Expression 1)
 
where the minimum extent length N_ecc is the number of ECC (error correction code) blocks in the extent (assuming that a length of one ECC block equals 16 sectors), Vo is the average data rate (in Mbps) of the recorded AV data, Tj is the access time (in secs) from the inner periphery to the outer periphery of the disk  700 , and Vr is the constant data reading rate (in Mbps) at which a reproduction apparatus reads out data from a series of continuous areas.
 
   The access time of an optical disk drive is substantially constant for any distance to the data being accessed which is equal to or greater than a certain distance. Therefore, it is effective to employ the access time from the inner periphery to the outer periphery of the disk  700  as a common access time. 
   Based on actually recorded data, the average data rate Vo can be expressed as follows:
 
 Vo =( N _pack−1)×2048×8/(27000000/( SCR ( i )− SCR ( i− 1))   (Expression 2)
 
where N_pack is the number of logical sectors in an extent, SCR(i) is an SCR value recorded in the last logical sector of the extent (obtained by counting the number of 27 MHz clock signals), and SCR(i−1) is an SCR value recorded in the first logical sector in the extent.
 
   Where some small-sized access areas (unallocated areas, data areas) having no AV data therein are included between extents, the minimum extent length can be expressed as follows:
 
 Nt   —   ecc≧dN   —   ecc+Vo ×( Tj+Ts )/((16×8×2048)×(1− Vo/Vr )   (Expression 3)
 
where the minimum extent length Nt_ecc is the total length of the access areas (unallocated areas, data areas) (in units of the number of ECC blocks) included between extents, dN_ecc is the total length of each access area (in units of the number of ECC blocks), and Ts is the total amount of time for which each access area is accessed. This access time is defined as Nt_ecc×16×8×2048/Vr.
 
   Using Expression 3, it is possible to determine, for example, whether the amount of data in the track buffer  453  would decrease to zero when reading out AV data from the extents  137  and  139  where the unallocated area  106  having no AV data recorded thereon exists between the extents  137  and  139 . The average data rate Vo can be calculated as follows:
 
 Vo =( N _pack−2)×2048×8/(27000000/( SCR (2)− SCR (1)+ SCR (4)− SCR (3)))   (Expression 4)
 
where N_pack is the total number of sectors in the extents  137  and  139 .
 
   Generally, the average data rate Vo for a number k of extents can be calculated as follows:
 
 Vo =( N _pack− k )×2048×8/(27000000/Σ( SCR ( i )− SCR ( i− 1)))   (Expression 5)
 
where Σ(SCR(i)−SCR(i−1)) is a value obtained by adding together, for all the extents, the difference between the SCR value of the first sector of each extent and the SCR value of the last sector of the extent.
 
   Next, referring to the flow chart of  FIG. 5 , an operation of editing the AV data as illustrated in  FIG. 4  by using the information recording/reproduction system apparatus  400  of  FIG. 1  will be described. 
   When the user instructs the information recording/reproduction system apparatus  400  to edit the AV data, the file system processing section  404  is first activated to instruct the data read section  446  to read out the volume structure area  101  from the disk  700  to the optical disk drive  407 . The read information is stored in the file structure memory  451 . The file structure processing section  441  analyzes the volume structure and reads out the file structure area  102  to the file structure memory  451 . 
   Then, the file structure processing section  441  searches for the video directory  902 , the Video. IFO file  903  and the Video.AVD file  904  under the root directory  901 . Then, the file structure processing section  442  reads out the file entries  129  and  130  to the file structure memory  451 , analyzes the location information of the control data  136 , and reads out the control data  136  to the program memory  431 . Then, the AV file structure processing section  443  reads out the AV allocation information area  103  to the file structure memory  451  and obtains the location information of each extent (“read file” step: S 601  in  FIG. 5 ). 
   The AV allocation structure processing section  444  instructs the optical disk drive  407  to read out the SCR recorded in the pack header  170  of each extent. The information is read out to the AV allocation structure memory  452 , and the SCR values are stored in the AV allocation structure memory  452  (“obtain SCR” step: S 602  in  FIG. 5 ). 
   Then, if the user specifies an edition point  1  ( FIG. 4 ), the AV allocation structure processing section  444  instructs the optical disk drive  407  to read out the sector information corresponding to edition point  1 . The read information is read out to the AV allocation structure memory  452 , and the SCR value is stored as SCR( 9 ) in the AV allocation structure memory  452  (“obtain SCR at edition point” step: S 603  in  FIG. 5 ). 
   Then, the AV allocation structure processing section  444  determines Nt_ecc according to Expression 3. Based on Expression 5 Vo( 5 ) can be calculated as follows:
 
 Vo =( N _pack−2)×2048×8/(27000000/( SCR (2)− SCR (1)+ SCR (9)− SCR (3)))   (Expression 6)
 
   If Nt_ecc satisfies the condition of Expression 3, the extents  139  and  141  can be continuously reproduced even if the remaining portion of the extent  139  following edition point  1  is cleared (step of determining whether the AV data is continuously reproducible: S 604  in  FIG. 5 ). 
   If the AV data is continuously reproducible (“Yes” in S 604 ), the AV allocation structure processing section  444  updates the allocation descriptor  133  of the extent  139  and record the updated allocation descriptor  133  in the AV allocation information area  103 . 
   Then, the file structure processing section  441  instructs the optical disk drive  407  to update the space bit map on the file structure memory  451  and to update the space bit map  121  on the disk  700  so that other data can be recorded in the cleared area of the extent  139  following edition point  1  (“editing process” step: S 605  in  FIG. 5 ). 
   If the user specifies edition point  2  as shown in  FIG. 6 , Expression 3 is calculated with the SCR ( 10 ) for edition point  2 , and it is determined in step S 604  that the condition of Expression 3 is not satisfied (“No” in S 604 ). Therefore, if the remaining portion of the extent  139  following edition point  2  is cleared, the amount of data in the track buffer  453  would decrease to zero. Thus, it would not be possible to continuously reproduce the AV data. Therefore, in such a case, the process is terminated without performing the editing process which if performed would delete the data from the remaining portion of the extent  139 . 
   As described above, according to the present embodiment, a plurality of extents are managed by a series of continuous SCRs, whereby the average data rate of the data recorded on the disk  700  can be correctly calculated. Therefore, whether continuous reproduction would be ensured after an edition can be correctly determined by reading out the first sector and the last sector of each extent without having to reproduce all the data. 
   As described above, by recording AV data having continuous parameters in each physically continuous area, it is possible to accurately calculate the average data rate of the recorded data for each area and thus to accurately determine the track buffer in a reproduction operation. 
   A plurality of different types of AV data may be recorded as a plurality of files in the video directory  902 . For example, different sets of AV data may be recorded based on the recording times and/or dates or a still image and a motion picture may be recorded separately as different VOBs. Alternatively, different sets of AV data may be recorded based on the titles thereof. 
   In the example described above, continuous areas in each of which data having the same attribute is recorded are managed as the extents  141  and  142 . However, the information of the data having the same attribute may be recorded in attribute information  162  of the file entry  130  as attribute information of an AV file, or the information of the data having the same attribute may be recorded as a named stream by using an extension file entry. 
   In the example shown above, continuous areas in each of which data having the same attribute is recorded are managed as the extents  141  and  142 , and the location information of the extent  141  and the location information of the extent  142  are managed by the allocation descriptors  134  and  135 , respectively. Alternatively, the information relating to the locations of the extents  141  and  142  may be recorded in the Video.IFO file as a portion of the control data  136 . For example, the length of each of the extents  141  and  142  may be recorded in a tabular form for each of the extents as a portion of the control data  136 . In such a case, an area which is managed by the allocation descriptors  134  and  135  does not have to be an area in which data having the same attribute is recorded. Thus, it is possible to simplify the file structure. When determining whether the AV data can be continuously reproduced around an edition point, the location information of each of the extents  141  and  142  can be known based on the allocation descriptors  134  and  135  and the lengths of the extents  141  and  142  which have been recorded as the control data  136 . Therefore, it is possible to easily determine whether the AV data can be continuously reproduced around the edition point. 
   In the information recording medium of the present invention, areas in which the AV data is recorded are managed as extents in the AV file structure. Therefore, it is possible to ensure the continuous reproduction of the recorded AV data. It is not necessary to read out all the sectors in which the AV data is recorded so as to examine whether the AV data can be continuously reproduced. It is only necessary to read out the leading sector and the last sector of each extent. Therefore, edition of AV data can be made efficiently. 
   Moreover, it is possible to ensure the continuous reproduction of the recorded AV data by managing the area in which AV data is recorded as divided extents taking into consideration a physical area in the AV file structure in which user data cannot be recorded and the continuity of the AV data. 
   Various other modifications will be apparent to and can be readily made by those skilled in the art without departing from the scope and spirit of this invention. Accordingly, it is not intended that the scope of the claims appended hereto be limited to the description as set forth herein, but rather that the claims be broadly construed.