Abstract:
A reproducing apparatus comprises: a read unit for reading an information data file storing information data and an index file relating to the information data file, from a recording medium; a communication unit for transmitting the data file read by the read unit to an external apparatus for processing the data file in accordance with a predetermined file system; a conversion unit for converting the index file into a structure corresponding to the predetermined file system and generating conversion index information; and a control unit for controlling the communication unit to transmit the conversion index information in response to a data transmission request from the external apparatus.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an information processing apparatus, and more particularly to an apparatus for processing information data files by using index files. 
     2. Related Background Art 
     There are conventional apparatuses which manage data such as video data and audio data in the form of files. 
     Among these apparatuses, there is an apparatus which manages a plurality of information data files by using index files storing index information for identifying the contents of each data file stored on a recording medium (e.g., refer to Japanese Patent Application Laid-Open No. 2002-278996, corresponding U.S. Publication No. 2003182279). In the apparatus described in Japanese Patent Application Laid-Open No. 2002-278996, a layout of information data files recorded on a recording medium is displayed on a display by using index files. A user designates a desired file by referring to the displayed index files and instructs to reproduce the desired file. 
     For example, an index film may be a file (title file) storing collection of character trains each added to an information file to feature the contents thereof. 
     The apparatus described in Japanese Patent Application Laid-Open No. 2002-278996 can manage a plurality of information data files stored on a recording medium by classifying them into common elements (virtual folders) such as record dates, travel locations and events. 
     It is considered to make part of property information in an index file have information defining attribute information (flag) (e.g., refer to Japanese Patent Application Laid-Open No. 2003-50811, corresponding U.S. Publication No. 2004047597). In this case, it is possible to retrieve and sort files on a recording medium at high speed and to judge at high speed whether a file is to be erased. 
     The above-described structures of prior art are, however, associated with the following problems. 
     For example, there is a case that video data or the like recorded on a recording medium is transferred to an external apparatus such as a personal computer to edit and view it. 
     In this case, even if video data is transferred to the external apparatus, information such as a virtual holder structure and titles cannot be confirmed on the external apparatus, because property information, title information and the like of an index file are lacking. 
     There arises therefore a problem that a user feels difficulty in processing data transferred from the recording apparatus to the external apparatus. 
     It can therefore be considered that data as well as the index file is transferred to the external apparatus. 
     However, also in this case, if the external apparatus does not have a dedicated application for understanding the structure of the index file, information such as the virtual holder structure and titles cannot be confirmed on the external apparatus. 
     There arises therefore a problem that a user feels difficulty in processing data transferred from the recording apparatus on the external apparatus. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to solve the above-described problems. 
     Another object of the present invention is to allow an external apparatus to easily process an externally received data file even if the external apparatus does not have a dedicated application for understanding the structure of an index file. 
     In order to solve the above-described problems and achieve the above-described objects, the present invention provides a reproducing apparatus comprising: read means for reading an information data file storing information data and an index file relating to the information data file, from a recording medium; communication means for transmitting the information data file read by the read means to an external apparatus for processing the information data file in accordance with a predetermined file system; conversion means for converting the index file into a structure corresponding to the predetermined file system and generating conversion index information; and control means for controlling the communication means to transmit the conversion index information in response to a data transmission request from the external apparatus. 
     Other objects and advantages of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram showing an example of the structure of a video camera and a personal computer PC according to an embodiment of the present invention. 
         FIG. 2  is a diagram showing an example of directories of a file system. 
         FIG. 3  is a diagram showing an example of a property file. 
         FIG. 4  is a diagram showing an example of real data of a property entry. 
         FIG. 5  is a diagram showing an example of a title file. 
         FIG. 6  is a diagram showing a correspondence between a virtual file structure of index data and a directory structure of a file system. 
         FIG. 7  is a diagram showing an example of information on property entries according to an embodiment. 
         FIG. 8  is a diagram showing an example of information on title entries according to an embodiment. 
         FIG. 9  is a diagram showing an example of a volume structure and a file structure in a disk. 
         FIG. 10  is a diagram showing an example of virtual directory information. 
         FIG. 11  is a flow chart illustrating a read operation of a logical block to be executed by a control microcomputer. 
         FIG. 12  is a diagram showing an example of the structure of a file transferred to a file system of PC. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Embodiments of the present invention will be described with reference to the accompanying drawings. 
       FIG. 1  is a block diagram showing an example of the structure of a system connecting a video camera  100  and a PC  130  according to an embodiment of the present invention. 
     First, description will be made on a photographing operation by the video camera  100 . 
     When power is supplied by using a user interface (I/F)  113  including a power switch, a record switch and the like, a control microcomputer  112  controls each component of the video camera, and an image photographed by an image pickup unit  101  is displayed on a display  116 . 
     In this state, upon instruction of a record start, the control microcomputer  112  controls a video encoder  103  to encode moving image data output from the image pickup unit  101  to compress its information amount. The control microcomputer  112  also controls an audio encoder  104  to encode audio data output from a microphone  102  to compress its information amount. 
     In this embodiment, the video encoder  103  and audio encoder  104  encode moving image data and audio data in accordance with an MPEG scheme. Each output from the video encoder  103  and audio encoder  104  is called an elementary stream. 
     MPEG elementary streams output from the video encoder  103  and audio encoder  104  are added with necessary data such as sync data and then multiplexed by a multiplexer  105 . A stream multiplexed by the multiplexer  105  is temporarily stored in a memory  107  via a memory controller  106 , as MPEG2-PS (program stream). 
     When the memory controller  106  is requested by the control microcomputer  112  to write data on a disk media  115 , it reads MPEG2-PS data from the memory  107 . The control microcomputer  112  stores various data generated during execution of programs into the memory  107  via the memory controller  106 . 
     The disk controller  114  writes the MPEG2-PS data read from the memory  107  onto the disk media  115 . In this embodiment, a set of MPEG2-PS data generated during a period from record start instruction to record stop instruction is recorded on the disk media  115  as one MPEG file. In this embodiment, an optical disk such as a DVD-RAM is used as the disk media. 
     The disk controller  114  controls read/write of various data and files as to the disk media  115  and controls the format thereof. In managing files on a recording media such as the disk media  115 , generally a file system such as FAT (File Allocation Table) and UDF (Universal Disk Format) is used. 
     For example, UDF is defined so as to establish compatibility of information data files between various computer OSes. UDF has been adopted as a file system of DVD-Video and rewritable disks such as DVD-RAM, and is expected to be adopted further by a variety of platforms. 
     In this embodiment, UDF is used as the file system for managing files on the disk media  115 . UDF is defined on the basis of ISO/IEC 13346 (Volume and file structure of write-once and rewritable media using non-sequential recording for information interchange). 
     Next, description will be made on a reproduction operation by the video camera  100 . 
     Upon reproduction instruction from the user I/F  113  after the MPEG file recorded on the disk media  115  is designated, the control microcomputer  112  instructs the disk controller  114  to read the designated MPEG film from the disk media  115 . In accordance with the instruction from the control microcomputer  112 , the disk controller  114  reads the designated MPEG file from the disk media  115 , and extracts MPEG2-PS data and outputs it to the memory controller  106 . 
     The MPEG2-PS data output from the disk media  115  is stored in the memory  107  via the memory controller  106 . In response to a request from the control microcomputer  112 , the MPEG2-PS data stored in the memory  107  is output to a demultiplexer  109  via the memory controller  106 . 
     In order to continuously reproduce moving image data and audio data, the control microcomputer  112  controls the memory controller  106  and disk controller  114  in such a manner that the memory  107  does not overflows or underflows, by monitoring the amount of MPEG2-PS data read from the disk media  115  and stored in the memory  107  and the amount of data read from the memory  107  and supplied to the demultiplexer  109 . 
     In this manner, the control microcomputer  112  intermittently reads data from the disk media  115 . Under the control of the control microcomputer  112 , the demultiplexer  109  demultiplexes the MPEG2-PS data into a video elementary stream and an audio elementary stream. 
     The video elementary stream is supplied to a video decoder  110 . The video decoder  110  decodes the reproduced video elementary stream and outputs it to the display  116  and an output unit  108 . The display  116  displays the reproduced moving image data. 
     The reproduced audio elementary stream is supplied to an audio decoder  111 . The audio decoder  111  decodes the reproduced audio elementary stream and outputs it to the output unit  108 . The output unit  108  converts the reproduced moving image data and audio data into the form suitable for outputting the data to an external TV monitor or the like, and outputs the converted data. 
     Next, description will be made on processes to be executed after the video camera  100  and personal computer (PC)  130  of the embodiment are connected via a transmission line (interface cable)  120 . 
     An external I/F  118  of the video camera  100  is used for connecting an external apparatus such as PC  130  to the video camera  100 . In this embodiment, although interfaces such as USB, IEEE1394, wireless LAN and the like are used, other interfaces may also be used. 
     PC  130  processes various information data files recorded in a built-in HDD or the like, by using a file system  140 . In this embodiment, the file system uses UDF similarly to the file system of the disk media  115 . 
     The file system  140  of PC  130  requests a particular sector of the disk media  115  from the control microcomputer  112  via the transmission line  120  and external I/F  180 . It is therefore possible to recognize the volume structure and file structure of the disk media  115 . 
     With reference to  FIGS. 2 to 8 , detailed description will be made on how the file system manages an MPEG file photographed with the video camera  100 . 
       FIG. 2  is a diagram showing an example of the structure of the MPEG file photographed with the video camera  100 . 
     Four MPEG files are stored under a Root directory  200 , the MPEG files including “ABCD0001.mpg”  204 , “ABCD002.mpg”  205 ,  4 , “ABCD003.mpg”  206  and “ABCD004.mpg”  207  in the order of photographing. 
     A property file  202  and a title file  203  which are index files are stored under an Index directory  201 . 
     The property file  202  is a set of property entries indicating attributes of MPEG files. The title file  203  is a set of title entries indicating title attributes of MPEG files. 
       FIG. 3  is a diagram showing an example of the property file  202 . 
     Referring to  FIG. 3 , the property file  202  is a table showing data lengths L_PR 1 , L_PR 2 , L_PR 3 , . . . , L_PRn and start byte positions  0 , L_PR 1 , L_PR 1 +L_PR 2 , . . . , L_PR 1 +L_PR 2 + . . . +L_PRn−1, respectively of a property entry # 1 , a property entry # 2 , a property entry # 3 , . . . , a property entry #n indicating the attributes of the MPEG files  204  to  207 . A data length is represented, for example, by a byte unit. 
     Similarly,  FIG. 5  is a diagram showing an example of the title file  203 . 
     Referring to  FIG. 5 , the title file  203  is a table showing data lengths L_TL 1 , L_TL 2 , L_TL 3 , . . . , L_TLn and start byte positions  0 , L_TL 1 , L_TL 1 +L_TL 2 , . . . , L_TL 1 +L_TL 2 + . . . +L_TLn−1, respectively of a title entry # 1 , a title entry # 2 , a title entry # 3 , . . . , a title entry #n indicating the attributes of the MPEG files. A data length is represented, for example, by the byte. 
       FIG. 4  is a diagram showing an example of the structure of actual data of a property entry. 
     Referring to  FIG. 4 , real data of a property entry is constituted of a type, a property length, a property entry number, a title entry number, a parent entry number and a file identifier. 
     The type indicates whether the property entry is an upper most level folder, i.e., a root holder, another holder, or a file corresponding to video data (MPEG file). The type is one byte data having the start byte address at a 0-th byte position. 
     The property data length shows the data length of the property entry in bytes. The property data length is one byte data having the start byte address at a 1-st byte position. 
     The property entry number starts from # 1  and is a unique number assigned to each property entry, i.e., an identifier for identifying each property entry. The property entry number is two-byte data having the start byte address at a 2-nd byte position. 
     The title entry number indicates a title entry ( FIG. 5 ) corresponding to title information of the property entry. The title entry number is two-byte data having the start byte address at a 4-th byte position. 
     The parent entry number is a property entry number of a folder to which the property entry belongs. The parent entry number is two-byte data having the start byte address at a 6-th byte position. The parent entry number of the root holder is # 0 . 
     The file identifier indicates an MPEG file name if the type of the property entry is a file, and is variable length data having the start byte address at an 8-th byte position. Real data of the title entry contains character trains, character codes and the like. 
     Next, description will be made on a specific example of a virtual holder structure of the property file  202  and title file  203  which are index files. 
     It is assumed that the disk media  115  records the four MPEG files managed on the file system as shown in  FIG. 2 . 
     It is also assumed that the MPEG files are classified by the virtual folder structure and title names  301  to  309  shown in  FIG. 6 . Reference numerals  301 ,  302 ,  304 ,  305  and  308  represent virtual folders, and reference numerals  303 ,  306 ,  307  and  309  represent virtual files. 
     Namely, the ABCD0001.mpg file  204  corresponds to a file  309  having a title name “bus stop”, and is stored in a folder  308  having a title name “town” under a folder  304  having a title name “travel”. 
     The ABCD0002.mpg file  205  corresponds to a file  307  having a title name “surfing”, and is stored in a folder  305  having a title name “island” under the folder  304  having the title name “travel”. 
     The ABCD0003.mpg file  206  corresponds to a file  306  having a title name “sandy beach”, and is stored in the folder  305  having the title name “island” under the folder  304  having the title name “travel”. 
     The ABCD0004.mpg file  207  corresponds to a file  303  having a title name “field day”, and is stored in a folder  302  having a title name “child”. 
       FIG. 7  is a diagram showing property entries of the property file  202  when the MPEG files are classified by the virtual folder structure and title names shown in  FIG. 6 . 
       FIG. 8  is a diagram showing title entries of the title file  203  when the MPEG files are classified by the virtual folder structure and title names shown in  FIG. 6 . 
     In  FIG. 7 , the property entry number # 1  is a root holder having no title entry, a parent entry  0 , and no file identifier. The property entry number # 2  is a folder having the title name “child”, a title entry number # 1  as seen from  FIG. 8 , a parent entry number # 1  because it belongs to the root holder, and no file identifier. 
     The property entry number # 3  is a file having the title name “field day”, a title entry number # 2  as seen from  FIG. 8 , a parent entry number # 2  because it belongs to the “child” folder, and a file identifier “ABCD0004.mpg”. The property entry number # 4  is a folder having the title name “travel”, a title entry number # 3  as seen from  FIG. 8 , the parent entry number # 1  because it belongs to the root folder, and no file identifier. 
     The property entry number # 5  is a folder having the title name “island”, a title entry number # 4  as seen from  FIG. 8 , a parent entry number # 4  because it belongs to the “travel” folder, and no file identifier. 
     The property entry number # 6  is a file having the title name “sandy beach”, a title entry number # 5  as seen from  FIG. 8 , a parent entry number # 5  because it belongs to the “island” folder, and a file identifier “ABCD0003.mpg”. The property entry number # 7  is a file having the title name “surfing”, a title entry number # 6  as seen from  FIG. 8 , the parent entry number # 5  because it belongs to the “island” folder, and a file identifier “ABCD0002.mpg”. 
     The property entry number # 8  is a folder having the title name “town”, a title entry number # 7  as seen from  FIG. 8 , the parent entry number # 4  because it belongs to the “travel” folder, and no file identifier. The property entry number # 9  is a file having the title name “bus stop”, a title entry number # 8  as seen from  FIG. 8 , a parent entry number # 8  because it belongs to the “town” folder, and a file identifier “ABCD0001.mpg”. 
     The control microcomputer  112  analyzes these index files, i.e., the property film  202  and title file  203 , and displays the virtual folder structure and title names  301  to  309  on the display  116 . 
       FIG. 9  is a diagram showing an example of a volume structure and a file structure of UDF configured on the disk media  115 . 
     In order to handle the disk media  115  as a logical volume, the storage area of the disk media  115  is divided into units called sectors, and logical sector numbers (hereinafter called LSN) from # 0  to the last LSN are assigned to sectors. A length of a logical sector is 2048 bytes equal to a length of a physical sector of the disk media  115 . A logical sector number # 0  is assigned to a sector having a physical sector number 031000h where h denotes a hexadecimal number. 
     A physical sector number (hereinafter called PSN) is the sector number assigned to each sector of the disk media  115 , and is recorded in a header field of each sector data. By using this sector number, data is read from the disk media. 
     Referring to  FIG. 9 , a start volume descriptor pointer is recorded at the same LSN of all DVD disks. In order to improve reliability, the start volume descriptor pointer is recorded at two positions, LSN=256 and the last LSN. The start volume descriptor pointer records head LSNs and the number of data bytes of each of a main volume descriptor train and a reserved volume descriptor train. In order to improve reliability, the same data is recorded in both the main volume descriptor train and reserved volume descriptor train. 
     A partition descriptor and a logical volume descriptor are recorded in the main volume descriptor train or reserved volume descriptor train. A head LSN of the partition start sector is recorded in the partition descriptor. A start logical block number (LBN) and the number of data bytes of a file set descriptor train are recorded in the logical volume descriptor train. LBN is a serial number starting from # 0  at the partition head position. A sector position in each partition is represented by LBN. Therefore, the relation between LSN and LBN is expressed by:
 
 LSN =partition head  LSN+LBN.  
 
     By using this relation, the disk controller  114  converts LBN into LSN, and LSN into PSN to thereby determine the physical sector position of the disk media  115  to be accessed. Data is read from the determined position. 
     In  FIG. 9 , a spatial bit map descriptor is recorded at LBN=0 to 79. The spatial bit map descriptor has a spatial bit map indicating whether each logical block can be allocated. Each bit of the spatial bit map corresponds to each logical block. If the bit value is “1”, the logical block is still not allocated, whereas if the bit value is “0”, the logical block is already allocated. 
     A file set descriptor is recorded at LBN=80. The file set descriptor records block position information of a file entry of a root directory. A terminator descriptor is recorded at LBN=81. The file entry of the root directory is recorded at LBN=82. The file entry is used in order to store various attribute information unique to each file and information on a time stamp, a file record position (LBN) and a file size. 
     In  FIG. 9 , a file entry of the ABCD0001.mpg file is recorded at LBN=100, and its actual data is recorded at LBN=101 to 150. A file entry of the ABCD0002.mpg file is recorded at LBN=151, and its actual data is recorded at LBN=152 to 300. A file entry of the ABCD0003.mpg file is recorded at LBN=301, and its actual data is recorded at LBN=302 to 600. A file entry of the ABCD0004.mpg file is recorded at LBN=601, and its actual data is recorded at LBN=602 to 900. 
     LBN  901  to the last LBN are still not allocated and recorded, and data is not recorded. Therefore, the corresponding bit value of the spatial bit map descriptor is “1” indicating an unallocated state. 
     As described above, the UDF file system can know all the directory structures and file structures of the disk media  115  along a route starting from the file entry of each root directory. 
     In the embodiment, as PC  130  is connected to the video camera  100 , prior to a data read request from the file system  140  of PC  130 , the control microcomputer  112  controls the memory controller  106  to form a virtual logical block space on the memory  107  and store virtual directory information representative of the directory structures of the disk media  115 . 
     Similar to the logical block space of the disk media  115 , the virtual logical block space has one block capacity of 2048 bytes and a virtual LBN (hereinafter called VLBN) is assigned to each block. 
     The same LBN (VLBN=82) as that of the logical block of the disk media  115  is assigned to the file entry of the root directory. By referring to the property entries ( FIG. 7 ) and title entries ( FIG. 8 ) of the index files, the control microcomputer  112  generates virtual directory information for management by replacing the virtual folder structure and title names based on the index files shown in  FIG. 6  with the file structure and file names of UDF.  FIG. 10  is a diagram showing the virtual directory information generated in this way. 
     VLBN of logical blocks excepting the file entry of the root directory is assigned LBN (LBN=901 to the last LBN) in the unallocated state in the spatial bit map on the disk  115 . 
     VLBN=901 is a block of the root directory and is constituted of a plurality of file identifier descriptors. Main information contained in the file identifier descriptor is the file name and position information of the file entry. In this embodiment, the title name of a corresponding property entry is used as the file name, and the position information of the file entry is designated by VLBN. However, if the file identifier descriptor corresponds not to the directory but to the file, the file name is the title name of the corresponding property entry, added with a file identifier extension of the property entry. The position information of the file entry designates LBN of the file entry of the disk media  115 . 
     It can be seen from  FIG. 7  that the property entries having the root folder as a parent entry are # 2  and # 4  which are both not the file but the folder and that the corresponding title entry numbers are # 1  and # 3 . It can be seen from  FIG. 8  that there are a folder having the title name “child” and a folder having the title name “travel”, under the root folder. Therefore, the block of the root directory at VLBN=901 records: a file identifier descriptor (file entry VLBN=82) of the parent directory (in this embodiment, root directory) of the root directory; a file identifier descriptor (file entry VLBN=902) of the directory name “child”; and a file identifier descriptor (file entry VLBN=904) of the directory name “travel”. The directory name is the virtual folder name (the title name of the virtual holder). 
     VLBN=902 corresponds to the block of the file entry of the “child” directory, and this block records the block position (VLBN=903) of the “child” directory. It can be seen from  FIGS. 7 and 8  that the property entry number # 3  corresponds to a file under the “child” directory corresponding to the property entry number # 2 . Its entity is the file having the file name “ABCD004.mpg” and the title name “field day”. VLBN=903 corresponds to the block of the “child” directory, and this block records the file identifier descriptor (file entry VLBN=82) of the parent directory (root directory) of the “child” directory, and the file identifier descriptor (file entry VLBN=601) having a file name “field day.mpg” obtained by adding an entity file extension “.mpg” to the title name “field day”. 
     Since the file entry of the entity file ABCD0004.mpg” is allocated to LBN=601 of the disk media  115  (refer to  FIG. 9 ), the file entry of the “field day.mpg” is VLBN=601. 
     VLBN=904 corresponds to the block of the file entry of the “travel” directory, and this block records the block position (VLBN=905) of the “travel” directory. 
     VLBN=905 corresponds to the block of the “travel” directory, and as seen from  FIGS. 7 and 8  this block records the file identifier descriptor (file entry VLBN=82) of the parent directory (root directory) of the “travel” directory, the file identifier descriptor (file entry VLBN=906) of the “island” directory and the file identifier descriptor (file entry VLBN=908) of the “town” directory. 
     VLBN=906 corresponds to the block of the file entry of the “island” directory, and this block records the block position (VLBN=907) of the “island” directory. 
     VLBN=907 corresponds to the block of the “island” directory, and as seen from  FIGS. 7 and 8  this block records the file identifier descriptor (file entry VLBN=904) of the parent directory (“travel” directory) of the “island” directory, the file identifier descriptor (file entry VLBN=301) of the “sandy beach” file and the file identifier descriptor (file entry VLBN=151) of a “surfing.mpg” file. 
     VLBN=908 corresponds to the block of the file entry of the “town” directory, and this block records the block position (VLBN=909) of the “town” directory. 
     VLBN=909 corresponds to the block of the “town” directory, and as seen from  FIGS. 7 and 8  this block records the file identifier descriptor (file entry VLBN=904) of the parent directory (“travel” directory) of the “town” directory and the file identifier descriptor (file entry VLBN=100) of a “bus stop.mpg” file. 
     Next, with reference to the flow chart shown in  FIG. 11 , description will be made on the operation of the control microcomputer  112  to be executed upon a read request of data in the disk media  115  from the file system  140  of PC  130  after the virtual directory information is generated in the manner described above. 
     When a read request of data recorded in a logical block of LBN=X (X=0−the last LBN: X is an integer) of the disk media  115  is received from the file system  140  via the external I/F  118  (Step S 1101 ), the control microcomputer  112  judges whether the virtual disk information in the memory  107  contains the virtual logical block at VLBN=X (Step S 1102 ). If the block at VLBN=X is contained, the flow advances to Step S 1103  whereat data of the virtual logical block at VLBN=X is read from the memory  107  and then the flow advances to Step S 1105 . If the virtual logical block at VLBN=X is not contained, the disk controller  114  is instructed to read data of the logical block at LBN=X of the disk media  115  and then flow advances to Step S 1105  (Step S 1104 ). 
     At Step S 1105 , data read at Step S 1103  or S 1104  is transmitted (transferred) to the file system  140  of PC  130 . Thereafter, the flow returns to Step S 1101  to wait for a read request from the file system  140 . 
     For example, upon reception of a read request of LBN=82 from the file system  140 , the control microcomputer  112  sends the data at VLBN=82, i.e., the data of the file entry of the root directory, to the file system  140 . The file system  140  can know from this data that the logical block number (actually, the virtual logical block number) at which the file entry of the root directory is stored, is 901. The file system  140  requests transmission of the data at LBN=901. 
     By repeating these operations, the virtual directory information shown in  FIG. 10  is transmitted in response to the transmission request from the file system of PC  130 . 
     Therefore, when the MPEG files  204  to  207  of the disk media  115  having the virtual folder structure and title names shown in  FIG. 6  are to be transferred to PC  130 , the virtual folder structure and title names shown in  FIG. 6  are replaced with the file structure and file names in conformity with UDF as shown in  FIG. 12 . 
     Therefore, even if there is no dedicated application for recognizing the virtual directory structure shown in  FIG. 6 , the file structure and file names similar to the virtual folder structure and title names shown in  FIG. 6  can be displayed on PC  130 . 
     The file name has the title name added with an extension (.mpg) of video data. Namely, the file name is changed to a name obtained by adding the extension of MPEG data to the title name of each MPEG file, and this changed name is transmitted to the file system  140 . 
     As described above, according to the embodiment, upon reception of a transmission request of data in the disk media from PC  130 , virtual directory information on the directory structure, directory names and file names corresponding to the virtual folder structure, virtual folder names and file names on the disk media  115 , is generated. Upon reception of a read request of data on the disk media  115  from PC  130 , the virtual directory information is read and transmitted to PC  130 . 
     The virtual directory information contains the data of a block in which the file entry of the root directory of the disk media  115 , and the numbers of blocks in an unallocated state in the disk media  115  are assigned as the virtual logical block numbers, excepting the block in which the file entry of the root directory is recorded. 
     All directories and file entries under the root directory are described in the virtual directory information. The file entries of information data files and actual MPEG file data are not described in the virtual directory information. The file identifier descriptor representative of a MPEG file indicates the head logical block number at which the file entry of the MPEG file in the disk media  115  is recorded. 
     In this embodiment, although MPEG files are processed by the video camera  100  and PC  130 , the present invention is also applicable to other files such as still image files containing JPEG encoded still image data and audio files containing audio data. 
     As described above, according to the embodiment, when information data files recorded on a recording medium is to be transmitted to an external apparatus, index file information such as the virtual folder structure and title names is replaced with the structure in conformity with the file system of the external apparatus. 
     Therefore, even if the external apparatus does not have a dedicated application for understanding the structure of index files, the external apparatus can display the file structure and file names similar to the virtual folder structure and title names. It is therefore easy for users to handle information data files recorded on a disk media. 
     The embodiment can be realized by making the control microcomputer (computer)  112  execute a program for the processes shown in  FIG. 11 . Embodiments of the present invention may be applied to means for supplying a computer with the program, e.g., a computer readable storage media such as a CD-ROM storing the program, and a transmission media for transmitting the program such as the Internet. Embodiments of the present invention may also be applied to computer program products storing the program such as a computer readable recording medium. The above-described program, recording medium, transmission media and computer program products are considered to fall within the scope of the present invention. The recording medium may be a flexible disk, a hard disk, an optical disk, a magneto optical disk, a CD-ROM, a magnetic tape, a nonvolatile memory card, a ROM or the like. 
     The above-described embodiments are only illustrative for embodying the present invention and are not construed to limitatively analyze the technical scope of the present invention. Namely, the present invention can be reduced in practice in various forms without departing from the technical concept or main features of the present invention. 
     This application claims priority from Japanese Patent Application No. 2004-319524 filed on Nov. 2, 2004, which is hereby incorporated by reference herein.