Abstract:
Even if a write operation onto a storage media on an external storage device is interrupted, consistency of management information on the storage media is improved. An image file transfer device includes a transferor which transfers an image file stored on a storage media to an external device, a retriever which obtains management information in relation to a file system from a storage media included in the external device, before the transfer of the image file by the transferor, a non-volatile storage which stores the management information obtained by the retriever, and a deleter which deletes the management information stored in the non-volatile storage in response to a completion of the transfer of the image file by the transferor.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority from Japanese Patent Application No. JP2008-174162 filed on Jul. 3, 2008, and the disclosure thereof, including its specification, its drawings, and its claims, is hereby incorporated by reference in its entirety for all purposes. 
     BACKGROUND 
     This disclosure relates to technology for storing files stored in an electronic device onto a media on an external device connected to the device. 
     Technology to transfer data between a plurality of storage media is widely used in general. For example, in Japanese Unexamined Patent Application Publication No. 2002-369121, an electronic camera which transfers image data from a memory card to a hard disk is disclosed. In detail, this electronic camera is configured to transfer all the image data recorded in the memory card to the hard disk, when the remaining capacity of the memory card reaches a predetermined value. Due to this, this electronic camera reduces a repetition frequency of start/stop of a rotating drive unit for rotating the hard disk, thereby minimizing power consumption. 
     However, the above-mentioned Publication does not mention a case where a transfer of image data is interrupted. If a transfer of image data is interrupted, inconsistency between the content of management information on a destination storage media and the content of image data actually stored on the destination storage media may occur. In such case, the content of management information on the destination storage media and/or the content of image data actually stored on the destination storage media must be changed to ensure consistency. As a prerequisite for this, whether a transfer of image data has been aborted or not needs to be detected. 
     SUMMARY 
     The present invention aims at providing an image file transfer device which can detect with relative ease whether a transfer of image data to an external device has been aborted or not. 
     In accordance with an embodiment of the present invention, an image file transfer device includes a transferor which transfers an image file stored on a storage media to an external device, a retriever which obtains management information in relation to a file system from a storage media included in the external device before the transfer of the image file by the transferor, a non-volatile storage which stores the management information obtained by the retriever, and a deleter which deletes the management information stored in the non-volatile storage in response to a completion of the transfer of the image file by the transferor. 
     In accordance with another embodiment, the image file transfer device may further include a recorder which records a backup of the management information stored on the storage media included in the external device onto the storage media included in the external device before the transfer of the image file by the transferor. 
     In accordance with another embodiment, the image file transfer device may further include a detector which detects whether the management information exists or dose not exist in the non-volatile storage, before the transfer of the image file by the transferor, a determiner which determines whether the storage media included in the external device is or is not identical with the storage media onto which the image file was transferred the previous time based on the detected management information, if the detector has detected the management information, and a display which displays a message if the determiner has determined that it is not identical. 
     In accordance with the present invention, an image file transfer device which can detect with relative ease whether a transfer of image data to an external device has been aborted or not can be provided. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram schematically illustrating an embodiment of a system in which the teaching of the present invention is embodied. 
         FIG. 2  is a block diagram illustrating details of a structure of a video camera. 
         FIG. 3  is a schematic diagram of a file system complying with AVCHD standard, which may be used with the system. 
         FIG. 4  is a flowchart illustrating a process of a file transfer. 
         FIG. 5  is a diagram illustrating a data flow in a file transfer shown in the flowchart of  FIG. 4 . 
         FIG. 6  is a flowchart illustrating a process of recovery of a file system. 
         FIG. 7  is a figure illustrating an example of a message for media replacement. 
         FIG. 8  is a diagram illustrating a relationship between content management information and the content. 
         FIG. 9  is a figure illustrating an example of a message which informs the user that a copy operation was not completed normally. 
         FIG. 10  is a schematic diagram of a non-volatile storage in accordance with another embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Definitions 
     The definitions of terms used to explain example embodiments are described below. 
     A “file transfer system” includes a device which sends a file and a device which receives the file. A file transfer system also includes a communication link which couples these devices. A device which sends a file may be any of, but is not limited to, a video camera, a hard disk drive (HDD) recorder, a Blu-ray recorder, a digital audio player, etc. A device which receives a file may be any of, but is not limited to, a DVD (Digital Versatile Disc) writer (also referred to as a DVD burner), a memory card writer, etc. Such a device which receives a file is also referred to as an “external device” in this specification. In this specification, a file is typically an A/V file, which will be described later. 
     An “internal media” may be any storage media, which is volatile, non-volatile, removable, or non-removable, provided in a device which sends a file. Examples of such an internal media include a HDD and a RAM (Random Access Memory). 
     An “external media” may be any storage media, which is volatile, non-volatile, removable, or non-removable, provided in a device which receives a file. Typically, an external media may be any of, but is not limited to, a DVD, a BD (Blu-ray Disc), etc. 
     “Management information” may typically include, but is not limited to, content management information, file system management information, and latest storage information. As an alternative, management information may include other management information in addition to the information mentioned above. 
     “Content management information” is information required for initialization of applications, and includes, for example, a name of content, content generation time information, content size information, content playback time information, etc. This content management information may include information needed for generating a list of content which is stored in a main storage of a device (e.g., a buffer memory of a video camera, etc.). 
     “File system management information (FS management information)” is information to manage an file system. FS management information may include, but is not limited to, a file name, a file size, file property information, an address where a file is located on an external media, and the capacity of a storage media. Typically, FS management information associates a directory structure, described later referring to  FIG. 3 , with a storage location on a media. 
     “Latest storage information” is a part of FS management information. If a system uses UDF (Universal Disk Format) as a file system, latest storage information is an LVID (Logical Volume Integrity Descriptor). An LVID is a descriptor which should be written each time the content of a logical volume associated with it is changed. For example, an LVID describes the last date and time (timestamp) when a change is made in the logical volume, a file size, etc. An LVID includes data “Integrity Type.” An Integrity Type represents either one of OPEN (a file write operation is in progress) and CLOSE (a file write operation has been completed). Therefore, the Integrity Type is changed to an OPEN state when a write operation to a media is started. The Integrity Type is returned to an CLOSE state when a write operation to a media is finished. 
     An “A/V file” is an electronic file, including at least one of data representing audio and data representing video. For example, such an A/V file may comply with standards such as MPEG-2, H.264, etc. 
     In this specification, an expression of “to record” or “to store” information means that the information is saved on a media. Such a media may be a disk media (e.g., a DVD, a BD, etc.), which is a rotating media, or may be a semiconductor media (e.g., a flash memory, etc.), which is a non-rotating media (also referred to as a solid state media). 
     Flowcharts in this specification illustrate processes to perform desired data processing. Such processes typically include a plurality of elements (i.e., steps). In this specification, the term “block” refers to one in which each step has been specifically realized (or a specific implementation). Therefore, a “block” in this specification corresponds to an act to implement a process. Such a “block” is typically implemented by software. Alternatively, a block may be implemented by hardware or a combination of software and hardware. 
     Now, example embodiments of a file transfer device will be described below in detail with reference to the drawings. The same or similar components in the drawings are indicated with same reference symbols. 
     (Overview) 
       FIG. 1  is a diagram illustrating a system  100  in accordance with an example embodiment of the present invention. The system  100  includes a video camera  110  (serves as a file transfer device) and a DVD (Digital Versatile Disc) writer  120  (serves as an external storage device). The system  100  is one example of a “file transfer system” described above. The video camera  110  is one example of a “device which sends a file.” The DVD writer  120  is one example of a “device which receives a file” described above. 
     A user of the system  100  may transfer an A/V (audio/video) file obtained with the video camera  110  to the DVD writer  120 , and store it on a DVD  125 . In such case, the video camera  110  is connected with the DVD writer  120  using a USB cable  130 . 
     The video camera  110  may alternatively be any device which outputs content such as image information, audio information, etc. to the DVD writer  120 . For example, instead of the video camera  110 , a digital still camera, a HDD (Hard Disk Drive) recorder, an IC (Integrated Circuit) recorder, etc. may be used. 
     The DVD writer  120  stores an electronic file on the DVD  125 , which is an external storage media (also referred to as simply a media). Instead of the DVD  125 , for example, a BD (Blu-ray Disc), a semiconductor memory card, etc. may be used. In such case, instead of the DVD writer  120 , any storage device compatible with an alternative media  125  (a BD writer, a memory card writer, etc.) may be used. The DVD  125  is one example of an “external media” described above. 
     The USB cable  130  complies with an interface standard of USB (Universal Serial Bus) standard. Instead of the USB cable  130 , interface technology based on HDMI (High-Definition Multimedia Interface), a wireless interface (e.g., an IEEE 802.11-compliant interface), etc. may be used. 
     The video camera  110  has a HDD therein. The HDD stores captured video on a hard disk as A/V (Audio/Video) data. The video camera  110  can obtain the time period allowed for storage based on the remaining capacity of the hard disk. 
     (Details of Video Camera) 
       FIG. 2  is a block diagram illustrating details of a structure of a video camera  110 . 
     The video camera  110  captures an object image formed by an optical system  210 , by an imaging device  221 . Image data generated by the imaging device  221  receives various image processing operations in an image processing section  240 . Audio data captured by a microphone  250  receives various audio processing operations in an audio processing section  251 . 
     Image data processed in the image processing section  240  and audio data processed in the audio processing section  251  receive system encoding in a system encoder  255 , and are stored on a hard disk drive  263 . Of an A/V file stored on the hard disk drive  263  etc., video data can be displayed in a liquid crystal display (LCD) monitor  264 , and audio data can be output through a speaker  265 . 
     The optical system  210  includes an objective lens  211 , a zoom lens  212 , a stop  213 , an OIS (Optical Image Stabilization) unit  214 , and a focusing lens  215 . The optical system  210  collects light from the object, and forms an object image. A drive system  216  drives each optical element in the optical system  210 . 
     The imaging device  221  captures the object image formed in the optical system  210 , and generates image data. The imaging device  221  is, for example, a CCD (Charge Coupled Device) image sensor or a CMOS (Complementary Metal Oxide Semiconductor) image sensor. A timing generator  222  generates a timing signal to drive the imaging device  221 . The imaging device  221  performs various operations of exposure, transfer, an electronic shutter, etc. according to the timing signal generated by the timing generator  222 . An AD (Analog-to-Digital) converter  231  converts the image data generated by the imaging device  221  to a digital signal. 
     The image processing section  240  performs various processing operations on the image data converted by the AD converter  231 . The image processing section  240  generates image data to be input to the system encoder  255 , or generates image data to be displayed in the LCD monitor  264 . Also, the image processing section  240  performs image processing operations on image data output from a system decoder  256 , and generates image data to be displayed in the LCD monitor  264 , or generates image data to be input again to the system encoder  255 . The image processing section  240  can be implemented with a DSP (Digital Signal Processor), a microcomputer, etc. 
     An image preprocessing section  241  performs various image processing operations such as gamma correction, white balance correction, artifact correction, etc. on the image data converted by the AD converter  231 . 
     An image compression section  242  compresses image data by performing DCT (Discrete Cosine Transform), Huffman encoding, etc. The image compression section  242  compresses image data by a compression format complying with, for example, MPEG (Motion Picture Experts Group)-2 or H.264 standard. Note that the system  100  may handle any data without limitation to data having a format complying with MPEG-2 or H.264. 
     In cases where compressed image data output from the system decoder  256  is reproduced in the LCD monitor  264 , etc., an image expansion section  243  decodes this image data to a non-compressed state. 
     The microphone  250  captures sound and generates audio data. In order to support an input of stereo audio or multi-channel audio, the microphone  250  may include a plurality of microphone units. 
     The audio processing section  251  performs various processing operations on the audio data from the microphone  250 . The audio processing section  251  generates audio data to be input to the system encoder  255 , or generates audio data to be output to the speaker  265 . The audio processing section  251  performs audio processing operations on audio data output from the system decoder  256 , and generates audio data to be output to the speaker  265 , or generates audio data to be input again to the system encoder  255 . The audio processing section  251  can be implemented with a DSP, a microcomputer, etc. 
     An audio preprocessing section  252  converts analog audio data captured by the microphone  250 , and generates audio data of a digital signal. The audio preprocessing section  252  may perform various audio processing operations such as generation of stereo audio and multi-channel audio, etc. 
     An audio compression section  253  compresses audio data by a compression format complying with, for example, MP3 (MPEG-1 Audio Layer-3), AAC (Advanced Audio Coding), etc. Note that the system  100  may handle audio data of any suitable compression format, without limitation to audio data complying with MP3 or AAC. 
     In cases where compressed audio data output from the system decoder  256  is output through the speaker  265 , an audio expansion section  254  decodes this audio data to a non-compressed state. 
     The system encoder  255  generates an A/V file to be stored on the hard disk drive  263 , from compressed image data which the image processing section  240  outputs, and from compressed audio data which the audio processing section  251  outputs. 
     The system decoder  256  decodes an A/V file stored on the hard disk drive  263 , and generates compressed image data and compressed audio data. The system decoder  256  outputs the generated compressed image data to the image expansion section  243 , and the generated compressed audio data to the audio expansion section  254 , respectively. 
     A controller  260  controls the entire video camera  110 . The controller  260  can be implemented by hardware, software, or a combination of hardware and software. The controller  260  manages and controls various functions of the video camera  110 . 
     A buffer memory  261  serves as a work memory for the controller  260  and the image processing section  240 . The buffer memory  261  can be implemented by, for example, a DRAM (Dynamic Random Access Memory), etc. 
     A non-volatile memory  290  stores information which needs to be held even after powering off. The non-volatile memory  290  may be, for example, a flash memory, a ferroelectric memory, etc. 
     A hard disk drive (HDD) control section  262  controls a data write operation onto the nard disk drive  263  and a data read operation from the hard disk drive  263 . In the system  100 , the video camera  110  integrates the hard disk drive  263  in a non-removable manner. However, the video camera  110  is not limited to such a configuration, but may use a removable semiconductor memory card, a removable hard disk, etc. as an internal media. The hard disk drive  263  is one example of an “internal media” described above included in the video camera  110 . 
     The LCD monitor  264  can display image data generated by the imaging device  221  and image data in an A/V file read from the hard disk drive  263 , etc. Also, the LCD monitor  264  can display various configuration information of the video camera  210 , the time of image capturing, etc. 
     The speaker  265  can output audio data captured by the microphone  250  and audio data in an A/V file read from the hard disk drive  263 , etc. 
     A manipulation section  270  may include various input devices. The manipulation section  270  generates an input signal corresponding to a user instruction, and outputs the input signal to the controller  260 . 
     A communication section  280  communicates with an external storage device (typically, the DVD writer  120 ). In other words, the communication section  280  serves as a transmitter and a receiver to send/receive data to/from the video camera  110 . The communication section  280  may be implemented by, for example, a USB communication unit. Instead of a USB communication unit, the communication section  280  may be an HDMI communication unit, etc. 
     (File System) 
       FIG. 3  is a schematic diagram of a file system  300  complying with AVCHD (Advanced Video Codec High Definition) standard, which may be used with the system  100 . AVCHD is a standard for storing high-definition video using a video camera. In AVCHD, H.264/MPEG-4 AVC technology is adopted for video encoding, and Dolby Digital (AC-3) technology is adopted for audio encoding. Note that a file system which may be used with the system  100  is not limited to AVCHD-compliant one. Other suitable file systems, including AVCHD Lite-compliant ones, may be used with the system  100 . 
     The file system  300  has two directories: BDMV and AVCHDTN. The directory BDMV has two files INDEX.BDM and MOVIEOBJ.BDM, and three subdirectories PLAYLIST, CLIPINF, and STREAM. 
     Under the subdirectory PLAYLIST, an MPL file (xxxxx.MPL) is created for each day of image capturing. Under the subdirectory CLIPINF, a CPI file (xxxxx.CPI) corresponding to one captured scene is created. A CPI file manages an MTS file of the same number (xxxxx). A CPI file has a file size on the order of several KBs. 
     Under the subdirectory STREAM, an MTS file (xxxxx.MTS) corresponding to one captured scene is created. An MTS file includes captured A/V data, and is created each time one scene is captured. An MTS file may have a file size up to 4 GB. The subdirectory STREAM may include up to 4,000 MTS files. Under the directory AVCHDTN, thumbnail files are created. 
     A file system (FS) management information described below associates the elements (directories, subdirectories, files, etc.) constituting the file system  300  with the locations of these elements on a media. In other words, FS management information describes a directory structure. 
     (File Transfer) 
     When an object is imaged using the video camera  110 , the imaging device  221  captures an object image formed by the optical system  210  and generates image data. The AD converter  231  converts the image data generated by the imaging device  221  to a digital signal. The image preprocessing section  241  performs gamma correction, white balance correction, etc. on the digital signal, and the image compression section  242  compresses the image data. The microphone  250  captures sound and generates audio data. The audio preprocessing section  252  converts the audio data generated by the microphone  250  to a digital signal, the audio compression section  253  compresses the digital audio data. The system encoder  255  generates an A/V file from compressed image data and audio data. The HDD control section  262  controls the hard disk drive  263 , thereby stores the generated A/V file on the hard disk drive  263 . 
       FIG. 4  is a flowchart illustrating a process  400  of a file transfer. Specifically, in the process  400 , an A/V file on the hard disk drive  263  of the video camera  110  is transferred to the DVD writer  120 , and stored on the DVD  125  (i.e., copied onto the DVD  125 ). 
       FIG. 5  is a diagram illustrating a data flow in a file transfer shown in the flowchart of  FIG. 4 . The DVD  125  has an FS management information area  502 , an LVID area  504 , an LVID backup area  506 , and an A/V file area  508 . The buffer memory  261  has an FS management information area  512 , an LVID area  514 , and an A/V file area  518 . The non-volatile memory  290  has an FS management information area  522  and an LVID area  524 . 
     Referring to  FIGS. 4 and 5 , the process  400  of a file transfer in the system  100  is described below in detail. 
     At block  401 , the video camera  110  is powered on. At block  402 , the controller  260  detects, via the communication section  280 , that the video camera  110  has been connected to the DVD writer  120 . 
     At block  404 , the controller  260  determines whether management information is stored in the non-volatile memory  290  or not. Management information which may be stored in the non-volatile memory  290  includes FS management information and latest storage information (e.g., LVID). 
     If management information exists in the non-volatile memory  290  (if the determination at block  404  is YES), it is determined that the previous copy operation to the DVD writer  120  was not completed normally. In such case, the process proceeds to block  601  shown in  FIG. 6 , and the management information on the DVD  125  is recovered as described below. Examples of such case where a copy operation to the DVD writer  120  is not completed normally include a case where the USB cable  130  connecting between the video camera  110  and the DVD writer  120  is unplugged during a copy operation, and a case where the power supply of the DVD writer  120  has been interrupted, etc. 
     If management information does not exist in the non-volatile memory  290  (if the determination at block  404  is NO), it is determined that the previous copy operation to the DVD writer  120  has been completed normally. Accordingly, the process proceeds to block  406 , and the intention of the user to start copying is confirmed. 
     At block  406 , it is determined whether to start copying or not based on an input of the user. If the determination at block  406  is NO, then the procedure terminates. If the determination at block  406  is YES, then the process proceeds to block  408 , and a copy operation is started. 
     At block  408 , FS management information read from the FS management information area  502  on the DVD  125  is stored in the FS management information area  512  in the buffer memory  261 . An LVID read from the LVID area  504  on the DVD  125  is stored in the LVID area  514  in the buffer memory  261 . 
     At block  410 , the Integrity Type in the LVID is changed from CLOSE to OPEN in the buffer memory  261 . At block  412 , the LVID is stored in the backup area  506  on the DVD  125 . 
     At block  414 , the LVID stored in the buffer memory  261  is stored in the non-volatile memory  290 . At block  416 , the LVID in the buffer memory  261  (Integrity Type=OPEN) is stored in the LVID area  504  on the DVD  125 . Therefore, both the LVID in the buffer memory  261  and the LVID on the DVD  125  represent that Integrity Type=OPEN. At this stage, the LVID stored in the backup area  506  and the LVID stored in the non-volatile memory  290  have the same contents. 
     At block  418 , the FS management information in the buffer memory  261  is updated. For example, an entry of 00002.CPI is added to the FS management information area  512 . Update operations of the FS management information is not limited to this, but may be deletion of an entry. 
     At block  420 , an A/V file in the buffer memory  261  is stored in the A/V file area  508  on the DVD  125 . 
     At block  422 , it is determined whether all the A/V files have been copied or not. If YES, then the process proceeds to block  424 . If NO, then the process returns to block  418 . Blocks  418  and  420  are executed for each A/V file. For example, if four A/V files captured on a same day are stored on the DVD  125 , blocks  418 ,  420 , and  422  are repeated four times. 
     If it is determined that all the A/V files have been copied at block  422 , then at block  424 , the FS management information is stored in the non-volatile memory  290 . At block  426 , the latest FS management information (i.e., FS management information including the entries 00000.CPI-00002.CPI) is stored on the DVD  125 . If the copy operation was not completed normally, then the non-volatile memory  290  continues to hold the FS management information. In other words, the FS management information in the non-volatile memory  290  is only deleted when a copy operation has been completed normally. This allows to determine whether the previous copy operation has been completed normally or not, without additionally using a special flag, etc. Such configuration has advantages of simplification of operations, reduction in memory usage, etc. 
     In an embodiment, block  424 , in which FS management information is stored in the non-volatile memory  290 , is executed after all the A/V files have been copied. The time required for storing the FS management information in the non-volatile memory  290  is significantly shorter compared with the time required for copying the A/V files. Therefore, considering the probability that a copy operation of an A/V file is interrupted, block  424  is preferably executed after block  422 . This increases the possibility that the FS management information stored in the non-volatile memory  290  reflects the actual structure of a file system correctly. In this specification, a condition that the FS management information reflects the actual structure of the file system correctly is referred to as “the FS management information maintains consistency.” 
     At block  428 , the Integrity Type in the LVID is changed to CLOSE in the buffer memory  261 . At block  430 , the LVID in the buffer memory  261  is stored on the DVD  125 . At block  432 , the FS management information and the LVID in the non-volatile memory  290  are deleted. At block  434 , a copy operation of the files is completed. 
     As described above, at block  432 , the FS management information and the LVID in the non-volatile memory  290  are deleted. Therefore, if a transfer of an image file is aborted, an LVID is stored in the non-volatile memory  290 . Now, a situation where a transfer of an image file is once again performed after a transfer of the image file has been aborted is considered. In this case, the controller  260  can determine whether the previous transfer of an image file has been aborted or not by checking whether an LVID or FS management information is stored in the non-volatile memory  290  or not. 
     (Recovery of File System) 
       FIG. 6  is a flowchart illustrating a process  600  of recovery of a file system. At block  601 , the process  600  starts. 
     At block  602 , it is determined whether the LVID on the DVD  125  is identical with the LVID in the non-volatile memory  290  or not. An LVID describes a timestamp of the last change, a file size, etc. Therefore, if these two LVIDs are identical, it is assumed that the same media as the one on which the copy operation was not completed normally has been inserted in the DVD writer  120 . If the determination at block  602  is YES, then the process proceeds to block  606 , and the file system is recovered. In this embodiment, the LVID in the non-volatile memory  290  is compared with the LVID which has been read from the LVID area  506 . 
     Here, this LVID backup area  506  is provided in a fixed location on the DVD  125 . This backup area  506  is arranged in an area which is not usually used in a file system adopted on the DVD  125 . In other words, even if a copy operation is interrupted and aborted as a violation of the standard, an LVID is expected to be read from this backup area  506 . 
     If the determination at block  602  is NO, then the process proceeds to block  604 , and prompts the user to replace the storage media. In this case, it is assumed that a different media from the one on which the copy operation was not completed normally is now inserted in the DVD writer  120 . 
       FIG. 7  is a figure illustrating an example of a message for media replacement. At block  604 , the LCD monitor  264  displays, for example, a message  702  which prompts the user to replace the media. A message for the user is not limited to a display on the LCD monitor  264 , but may be in another manner, such as a method by sound, etc. The user, prompted by such a message, is expected to insert the media on which the copy operation was not completed normally to the DVD writer  120 . 
     At block  606 , it is determined whether FS management information is stored in the non-volatile memory  290  or not. If the determination at block  606  is NO, then the process proceeds to block  608 , and the Integrity Type in the LVID stored on the DVD  125  is changed to CLOSE. The process proceeds from block  608  to block  610 , and the LVID stored in the non-volatile memory  290  is deleted. The process proceeds from block  610  to block  612 , and content recovery is performed as necessary. 
     If the determination at block  606  is YES, then the process proceeds to block  614 . At block  614 , the FS management information stored in the non-volatile memory  290  is recorded on the DVD  125 . That is, the FS management information on the DVD  125  is recovered. With this operation, even if a copy operation to the DVD  125  is aborted, the FS management information is recovered so that a read operation of a file will be possible, thereby allowing for content recovery. 
     The process proceeds from block  614  to block  616 , and the Integrity Type in the LVID recorded on the DVD  125  is changed to CLOSE. The process proceeds from block  616  to block  618 , and the FS management information as well as the LVID stored in the non-volatile memory  290  is deleted. The process proceeds from block  618  to block  612 , and content recovery is performed as necessary. 
     (Recovery of Content) 
     Content recovery at block  612  is performed to ensure consistency of file names, contents of files, etc. Through the recovery process of a file system described above, controller  260  can obtain content management information such as a file name on a file system. This allows the controller  260  to recover the content on a media. 
       FIG. 8  is a diagram illustrating a relationship between content management information and the content. The controller  260  obtains content management information (CPI files) and A/V files (MTS files) on the DVD  125 , and performs a recovery operation of the content. The content management information  800  includes INDEX.BDM file. INDEX.BDM file includes a playlist reference table  802 . The playlist reference table  802  includes entry-mark reference tables  804  and  806  for each playlist (here, 00000.MPL and 00001.MPL). Based on a last playlist number of the entry-mark reference table  806  (here, 00006), the content of a most recently added playlist is identified. In  FIG. 8 , the files 00006.CPI and 00006. MTS have not been copied normally. Therefore, these files should be deleted. On the other hand, the files 0000.CPI-00005.CPI and 00000.MTS-00005.MTS have been copied normally. Therefore, latest storage information, content management information, and A/V information is updated on the DVD  125  so as to maintain consistency with these files which should remain on the DVD  125 . 
     In the above example, when a copy operation is interrupted, the A/V files which had been copied normally before the interruption are treated as valid A/V information. The present invention is not limited to such a particular process. For example, when a copy operation is interrupted, a recovery operation may be simplified by deleting all the A/V files which relates to the copy operation. This may allow a recovery operation to be completed in a shorter time. 
     In the embodiment described above, connection of the video camera  110  to the DVD writer  120  triggers a recovery operation to be performed. In another embodiment, the controller  260  may determine whether management information exists in the non-volatile memory  290  or not when, for example, the video camera  110  is powered on. The existence of management information in the non-volatile memory  290  indicates that a copy operation was not completed normally. The video camera  110  may indicate this to the user. 
       FIG. 9  is a figure illustrating an example of a message which informs the user that a copy operation was not completed normally. The LCD monitor  264  may display, for example, a message as shown in  FIG. 9  to the user notifying that the previous copy operation has failed, and thereby prompt to perform recovery. A message for the user is not limited to a display on the LCD monitor  264 , but may be in another manner, such as a method by sound, etc. 
       FIG. 10  is a schematic diagram of a non-volatile memory  1090  in accordance with another embodiment. The non-volatile memory  1090  corresponds to the non-volatile memory  290  described above. The non-volatile memory  1090  is different from the non-volatile memory  290  in that the non-volatile memory  1090  stores a plurality of sets of management information corresponding to a plurality of external media (DVDs, etc.). That is, the non-volatile memory  1090  may store management information corresponding to different media in a plurality of areas  1010 ,  1012 ,  1014 ,  1016 , and  1018 . The number of sets of storable management information is not limited to 5, but generally, n sets (where n is an integer greater than or equal to 1) of management information may be stored. 
     By using the non-volatile memory  1090 , at block  602 , the video camera  110  can determine whether the LVID of a media currently inserted is identical with one in any of n media on which write operations have recently been interrupted. In other words, instead of comparing an inserted disk with a single media on which a write operation has been interrupted ( 602 ) and performing warning indication ( 604 ), it is possible to compare an inserted disk with n media on which write operations have been interrupted ( 602 ), and to perform warning indication ( 604 ). 
     In summary, the system  100  can maintain consistency between a file stored on the DVD  125  and management information stored on the DVD  125  by writing back the management information (e.g., FS management information) stored in the non-volatile memory  290  to the DVD  125 , even if a write operation to the DVD  125  is interrupted. In other words, even if a write operation to the DVD  125  is interrupted, a file system on the DVD  125  can be recovered. As a result, even for the DVD  125  on which a write operation has been interrupted, at least a read/write operation with a media can be performed after recovery. Thereafter, the content may be recovered based on a file which can now be read from the DVD  125 . 
     A file transfer device of the present invention can improve consistency of management information on a storage media, even if a write operation to the storage media on an external storage device is interrupted. Therefore, it is useful on a data file transfer device which outputs content, such as image information, etc., to an external storage device.