Abstract:
A system includes a reading unit reading first management information including a first item specifying video data and the video data from a storage medium, a storage unit recording second management information including the first item obtained from the first management information and the video data transferred from the reading unit, a memory storing third management information including the first item and a second item specifying a transfer or no transfer of the video data, and a controller transferring the first management information to the memory from the reading unit, updating the second item of the third management information in response to the transfer of the video data, and controlling the transfer of the video data in the video content which is designated by a read request from one of the reading unit and the storage unit to the outside based on the second item of the third management information.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a divisional of application Ser. No. 12/507,927, filed Jul. 23, 2009, which is incorporated herein by reference. 
    
    
     This application is based upon and claims the benefit of priority from prior Japanese Patent Applications No. 2008-236967, filed Sep. 16, 2008; and No. 2009-142119, filed Jun. 15, 2009, the entire contents of both of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a system for processing video data, a video server, a gateway server, and a method for managing and processing video data. 
     2. Description of the Related Art 
     In the conventional video data processing system, a video content of video contents are supplied from a video tape recorder (VTR) on which a moving picture and audio signals output from a video camera are recorded as the video content, are encoded and converted into a video file, and are recorded on a storage medium of a video server. When non-linear editing is carried out, an editing unit accesses the video server of the video data processing system, and reads a video file from the storage medium of the video server. Further, the editing unit carries out non-linear editing of the read video file. For this reason, in order to carry out non-linear editing, the imaged image must be encoded, and must wait until it is recorded on the storage medium of the video server. 
     Incidentally, in recent years, the storage medium of the video camera has been switched from a tape to a randomly accessible medium such as a hard disk, a semiconductor memory, and the like. When a semiconductor memory or the like is used as the storage medium of the video camera, it becomes possible to directly record a video signal from the video camera on the storage medium as a video file. As a result of this, it becomes unnecessary to subject the video signal from the VTR to encoding processing, and hence it becomes possible to shorten the waiting time up to the starting of the non-linear editing. However, the time for transferring the video file that has been imaged to the storage medium of the video server, and recording the video file is not resolved yet. 
     It should be noted that in order to shorten the time for transferring the video file to the video server, there is proposed, in Jpn. Pat. Appin. KOKAI Publication No. 2005-51491, a technique wherein an image signal, i.e., video data with low resolution and a small amount of data is transferred, editing work is then carried out, and then only data conforming to the editing content is transferred is proposed. However, although the waiting time is shortened by transferring data of low resolution, the waiting time is not eliminated. Further, using this method poses a problem that it is difficult to confirm the video data at the original image quality at the editing time. 
     BRIEF SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a system for processing video data, a video server, a gateway server, and a method capable of starting non-linear editing of an acquired video file without waiting time. 
     According to an aspect of the present invention, there is provided a system for reading a video content from a storage medium, the video content being recorded in preset units of video data in the storage medium, the system comprising: a reading unit which is connected to the storage medium to generate a setting signal, and reads first management information including a first item specifying the units of video data in response to the setting signal and the unit or units of video data in the video content from the storage medium; a storage unit which records second management information including the first item obtained from the first management information and the unit or units of video data in the video content transferred from the reading unit; a memory which stores third management information including the first item and a second item specifying a transfer or no transfer of the unit or units of video data from the reading unit to the storage unit; and a controller which transfers the first management information to the memory from the reading unit in response to the setting signal to update the third management information, updates the second item of the third management information in response to the transfer of the unit or units of video data from the reading unit to the storage unit, and controls the transfer of the unit or units of video data in the video content which is designated by a read request from the outside of the system from one of the reading unit and the storage unit to the outside of the system in accordance to the second item of the third management information. 
     Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
       The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention, and together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention. 
         FIG. 1  is a view showing the configuration of a video data processing system according to a first embodiment of the present invention. 
         FIG. 2  is a view showing an example of a file management table stored in a memory shown in  FIG. 1 . 
         FIG. 3  is a view showing an example of a block management table stored in a memory shown in  FIG. 1 . 
         FIG. 4  is a view showing an example of video data written to a logical block in a removable storage medium and a storage unit shown in  FIG. 1 . 
         FIG. 5  is a sequence diagram of a case where the video data processing system of  FIG. 1  prepares to transfer a video file recorded on a removable storage medium to a storage unit, and prepares to carry out non-linear editing of the video file by using a non-linear editing unit. 
         FIG. 6A  is a view showing the states of the removable storage medium in the case where the processing of  FIG. 5  is carried out. 
         FIG. 6B  is a view showing the states of the memory in the case where the processing of  FIG. 5  is carried out. 
         FIG. 6C  is a view showing the states of the storage unit in the case where the processing of  FIG. 5  is carried out. 
         FIG. 7  is a sequence diagram of a case where after the processing of  FIG. 5  is completed, a video file is transferred from the removable storage medium to the storage unit in the background. 
         FIG. 8A  is a view showing the states of the removable storage medium in the case where the processing of  FIG. 7  is carried out. 
         FIG. 8B  is a view showing the states of the memory in the case where the processing of  FIG. 7  is carried out. 
         FIG. 8C  is a view showing the states of the storage unit in the case where the processing of  FIG. 7  is carried out. 
         FIG. 9  is a sequence diagram of a case where after the preparation of  FIG. 5  is completed, a request to read a video file recorded on the removable storage medium is received from the non-linear editing unit. 
         FIG. 10A  is a view showing the states of the removable storage medium in the case where the processing of  FIG. 9  is carried out. 
         FIG. 10B  is a view showing the states of the memory in the case where the processing of  FIG. 9  is carried out. 
         FIG. 10C  is a view showing the states of the storage unit in the case where the processing of  FIG. 9  is carried out. 
         FIG. 11  is a sequence diagram of a case where after the preparation of  FIG. 5  is completed, a request to write a video file that has already been edited is received from the non-linear editing unit. 
         FIG. 12A  is a view showing the states of the removable storage medium in the case where the processing of  FIG. 11  is carried out. 
         FIG. 12B  is a view showing the states of the memory in the case where the processing of  FIG. 11  is carried out. 
         FIG. 12C  is a view showing the states of the storage unit in the case where the processing of  FIG. 11  is carried out. 
         FIG. 13  is a sequence diagram of a case where a video file is transferred from the removable storage medium to the storage unit in the background in the procedure different from the transfer processing shown in the sequence diagram of  FIG. 7 . 
         FIG. 14A  is a view showing the states of the removable storage medium in the case where the processing of  FIG. 13  is carried out. 
         FIG. 14B  is a view showing the states of the memory in the case where the processing of  FIG. 13  is carried out. 
         FIG. 14C  is a view showing the states of the storage unit in the case where the processing of  FIG. 13  is carried out. 
         FIG. 15  is a view showing the configuration of a video data processing system according to a second embodiment of the present invention. 
         FIG. 16  is a sequence diagram of a case where the video data processing system of  FIG. 15  prepares to transfer a video file recorded on a removable storage medium to a video server, and prepares to carry out non-linear editing of the video file by using a non-linear editing unit. 
         FIG. 17A  is a view showing the states of the removable storage medium in the case where the processing of  FIG. 16  is carried out. 
         FIG. 17B  is a view showing the states of the gateway server in the case where the processing of  FIG. 16  is carried out. 
         FIG. 17C  is a view showing the states of the video server in the case where the processing of  FIG. 16  is carried out. 
         FIG. 18  is a sequence diagram of a case where after the processing of  FIG. 16  is completed, a video file is transferred from the removable storage medium to the video server in the background. 
         FIG. 19A  is a view showing the states of the removable storage medium in the case where the processing of  FIG. 18  is carried out. 
         FIG. 19B  is a view showing the states of the gateway server in the case where the processing of  FIG. 18  is carried out. 
         FIG. 19C  is a view showing the states of the video server in the case where the processing of  FIG. 18  is carried out. 
         FIG. 20  is a sequence diagram of a case where after the preparation of  FIG. 16  is completed, a request to read a video file recorded on the removable storage medium is received from a non-linear editing unit. 
         FIG. 21A  is a view showing the states of the removable storage medium in the case where the processing of  FIG. 20  is carried out. 
         FIG. 21B  is a view showing the states of the gateway server in the case where the processing of  FIG. 20  is carried out. 
         FIG. 21C  is a view showing the states of the video server in the case where the processing of  FIG. 20  is carried out. 
         FIG. 22  is a sequence diagram of a case where after the preparation of  FIG. 16  is completed, a request to write a video file that has already been edited is received from the non-linear editing unit. 
         FIG. 23A  is a view showing the states of the removable storage medium in the case where the processing of  FIG. 22  is carried out. 
         FIG. 23B  is a view showing the states of the gateway server in the case where the processing of  FIG. 22  is carried out. 
         FIG. 23C  is a view showing the states of the video server in the case where the processing of  FIG. 22  is carried out. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments of the present invention will be described below in detail while referring to the accompanying drawings. 
     First Embodiment 
       FIG. 1  is a schematic view showing the configuration of a video data processing system  10  according to a first embodiment of the present invention. The video data processing system  10  is provided with a reading unit  11 , and a video server  12 . The reading unit  11  has an insertion opening through which a removable storage medium  20  is inserted into the reading unit  11  and can be randomly accessed to the reading unit  11 . A non-linear editing unit  30  is connected to the video server  12 . 
     A video image or picture image taken by a camera  40  is converted into a video file, and is recorded on a removable storage medium  20 . On the removable storage medium  20 , a file management table for managing the recorded video file, and block management table for managing the recording state of the storage medium are recorded in advance, and if a video file is recorded thereon, these tables are updated in accordance with the recorded video file. It should be noted that the file management table and the block management table stored in the removable storage medium  20  have same structures as file management tables and block management tables stored in a storage unit  121  and a memory  122  in the video server  12 . The structures of the file management tables and the block management tables will be described later in detail. 
     The removable storage medium  20  is constituted of, for example, a semiconductor storage medium such as a flash memory and the like, or a hard disk or the like, and is set in the reading unit  11  through the insertion opening. The video file recorded on the removable storage medium  20  is read by the reading unit  11 , and is transferred to the video server  12 . 
     The video server  12  is provided with a storage unit  121 , a memory  122 , and a processing unit  123 . The storage unit  121  is a storage medium constituted of a semiconductor storage medium such as a flash memory and the like, or a hard disk or the like. As the memory  122 , for example, a random access memory (RAM) is used. The processing unit  123  is embodied as a controller for controlling the units in the video server  12 , and is configured by a microprocessor such as a central processing unit (CPU) or the like. 
     When the removable storage medium  20  is connected to the reading unit  11 , the processing unit  123  updates the file management table and the block management table recorded in advance in each of the storage unit  121  and memory  122 , prepares to transfer a video file recorded on the removable storage medium  20  to the storage unit  121 , and prepares to carry out non-linear editing of the video file by using the non-linear editing unit  30 . 
     If the preparation for transfer of the video file recorded on the removable storage medium  20  is completed, the processing unit  123  transfers the video file to the storage unit  121 , and updates the file management tables and block management tables of the memory  122  and storage unit  121 . 
     If the processing unit  123  receives a request to read the video file from the non-linear editing unit  30 , the unit  123  outputs the requested video file to the non-linear editing unit  30  by referring to the file management tables and block management tables recorded on removable storage medium  20 , memory  122 , and storage unit  121 . 
     If the processing unit  123  receives a request to write the video file from the non-linear editing unit  30 , the unit  123  records the video file in the storage unit  121 , and updates the file management tables and block management tables of the storage unit  121  and memory  122 . 
     The non-linear editing unit  30  is a device for carrying out non-linear editing of the video file. The non-linear editing unit  30  accesses the video server  12 , and requests the video server  12  to read a video file desired to be edited. Further, the non-linear editing unit  30  requests the video server  12  to write the video file that has already been edited. 
     Next, the processing operation of the video data processing system  10  configured as described above will be described below in detail. Specific examples of the file management table and the block management table in this embodiment are shown in  FIGS. 2 and 3 , respectively.  FIG. 2  is a view showing an example of the file management table possessed by each of the removable storage medium  20 , storage unit  121 , and memory  122 , and  FIG. 3  is a view showing an example of the block management table possessed by each of the removable storage medium  20 , storage unit  121 , and memory  122 . In the file management table, a file ID of the video file, file name, and number of the logical blocks in which the video file is recorded are shown. It should be noted that the logical block indicates a minimum management unit of a storage area on the removable storage medium  20  and storage unit  121 , and the video file is written/read in units of a logical block. Further, in the block management table, a logical block No., usage state of the logical block, ID of a device to which the logical block belongs, and physical address of the logical block are shown. It should be noted that in this embodiment, a device ID: D001 indicates a removable storage medium  20 , and device ID: D002 indicates a storage unit  121 . Further, video data is written to the logical blocks of the removable storage medium  20  and storage unit  121  as shown in, for example,  FIG. 4 . 
       FIG. 5  is a sequence diagram of a case where the video data processing system  10  according to the first embodiment of the present invention prepares to transfer a video file recorded on the removable storage medium  20  to the storage unit  121 , and prepares to carry out non-linear editing of the video file by using the non-linear editing unit  30 . Further,  FIG. 6  is a schematic view showing the states of the removable storage medium  20 , memory  122 , and storage unit  121  in the case where the video data processing system  10  carries out the processing shown in  FIG. 5 .  FIG. 6A  shows the states of the removable storage medium  20 .  FIG. 6B  shows the states of the memory  122 .  FIG. 6C  shows the states of the storage unit  121 . 
     In  FIG. 5 , when the removable storage medium  20  is set, the reading unit  11  notifies the processing unit  123  that the removable storage medium  20  is set. On receiving the notification indicating that the removable storage medium  20  is set, the processing unit  123  causes the reading unit  11  to read information about the file management table. The reading unit  11  outputs the information about the file management table of the removable storage medium  20  to the processing unit  123 . 
     The processing unit  123  updates the file management table of the memory  122  on the basis of the information about the file management table (S 51 ). As a result of this, the information of the file management table of the removable storage medium  20  is written to the file management table of the memory  122 . 
     Subsequently, the processing unit  123  calculates a storage area necessary for recording video contents  1  to  3  on the storage unit  121 , and secures a logical block of the storage unit  121  on the basis of the calculated storage area (S 52 ). As a result of this, in the storage unit  121 , logical block Nos.: L105 and L106 for recording the video content  1  are secured, logical block Nos.: L107 to L109 for recording the video content  2  are secured, and logical block Nos.: L120 to L122 for recording the video content  3  are secured. On completing securing the storage area in the storage unit  121 , the processing unit  123  notifies the completion to the reading unit  11 , which, as a result, outputs information about the block management table of the removable storage medium  20  to the processing unit  123 . The processing unit  123  updates the block management table of the memory  122  on the basis of the information about the block management table (S 53 ). 
     When the removable storage medium  20  is set at the reading unit  11  as described above, the video data processing system  10  updates the file management table and the block management table of the memory  122  on the basis of the file management table and the block management table of the removable storage medium  20 . As a result of this, in the memory  122 , the management tables of the removable storage medium  20  are managed. That is, it can be considered that the video file recorded on the removable storage medium  20  is virtually recorded on the video server  12 . 
     Processing to be performed after the preparation for transfer of the video file recorded on the removable storage medium  20  to the storage unit  121 , and the preparation for non-linear editing of the video file by using the non-linear editing unit  30  have been completed by the processing shown in  FIG. 5  will be described below. 
     First, the case where after the processing shown in  FIG. 5  is completed, the video file is transferred from the removable storage medium  20  to the storage unit  121  in the background will be described below.  FIG. 7  is a sequence diagram at the time. Further,  FIG. 8  is a schematic view showing the states of the removable storage medium  20 , memory  122 , and storage unit  121  in the case where the video data processing system  10  carries out the processing shown in  FIG. 7 .  FIG. 8A  shows the states of the removable storage medium  20 .  FIG. 8B  shows the states of the memory  122 .  FIG. 8C  shows the states of the storage unit  121 . 
     In  FIG. 7 , the processing unit  123  gives an instruction to transfer the video content  1  which is the video file recorded on the removable storage medium  20  to the reading unit  11 . On receiving the instruction, the reading unit  11  transfers the video content  1  to the video server  12  in units of video data. The processing unit  123  records the video data transferred from the removable storage medium  20  on an unassigned address: h00000004 of the storage unit  121  (S 71 ). The processing unit  123  updates the block management table of the memory  122  on the basis of the write location of the video data in the storage unit  121 , sets the device ID of the logical block No.: L001 to D002, and sets the physical address to h00000004 (S 72 ). 
     When the block management table of the memory  122  is updated, the processing unit  123  gives the reading unit  11  an instruction to transfer the next video data. The reading unit  11  reads the next video data from the removable storage medium  20 , and transfers the video data to the video server  12 . The processing unit  123  records the video data transferred from the removable storage medium  20  on an unassigned address: h00000005 of the storage unit  121  (S 73 ). When the recording of the video data is completed, the processing unit  123  updates the block management table of the memory  122  on the basis of the write location of the video data in the storage unit  121 , sets the device ID of the logical block No.: L002 to D002, and sets the physical address to h00000005 (S 74 ). As a result of this, the video content  1  is transferred from the removable storage medium  20  to the storage unit  121 . 
     The video data processing system  10  repeats the processing of S 71  to S 74  to transfer the video contents  2  and  3  which are video files recorded on the removable storage medium  20  to the storage unit  121 . Further, on completing the transfer of the video files recorded on the removable storage medium  20 , the reading unit  11  notifies the video server  12  that the transfer of the video files recorded on the removable storage medium  20  has been completed. On receiving the notification indicating that the transfer has been completed, the processing unit  123  updates the block management table of the storage unit  121  on the basis of the block management table of the memory  122  (S 75 ). That is, the device IDs and physical addresses of the logical block Nos.: L105 to L109, and L120 to L122 in the storage unit  121  are rewritten to be changed to the device IDs and physical addresses of the logical block Nos.: L001 to L005, and L010 to L012 in the memory  122 , and the states of the logical block Nos.: L105 to L109, and L120 to L122 in the storage unit  121  are rewritten to be changed to busy (in use). Subsequently, the processing unit  123  updates the file management table of the storage unit  121  on the basis of the file management table of the memory  122 . That is, the video contents  1  to  3  transferred from the removable storage medium  20  are written to the file management table of the storage unit  121  (S 76 ). As a result of this, the transfer processing is completed. 
     As described above, the processing unit  123  transfers the video data from the reading unit  11  to the storage unit  121 , and updates the block management table of the memory  122 . Further, if the transfer of the video data is completed, the processing unit  123  updates the file management table and the block management table of the storage unit  121  on the basis of the file management table and the block management table of the memory  122 . As a result of this, in the video data processing system, it becomes possible, after the completion of the video file transfer, to merge the file management table and the block management table of the memory  122  into the file management table and the block management table of the storage unit  121 . Accordingly, it becomes possible to improve the transfer efficiency of the video file. It should be noted that this transfer processing can be executed while the non-linear editing is executed by the non-linear editing unit  30 . 
     In the case where the storage media of the removable storage medium  20  and storage unit  121  are semiconductor storage media, it can be assumed that the storage unit  121  is higher than the reading unit  11  in the input/output performance of the video data. In this case, the video files with the stronger possibility of being accessed are transferred to the video server earlier, whereby it becomes possible to improve the response speed with respect to the editing operation. Specific examples of the above will be shown below. 
     The processing unit  123  may give a transfer instruction to the reading unit  11  in such a manner that video data of a plurality of consecutive logical blocks on which video files which become objects of read requests are recorded is preferentially transferred. As a result of this, it becomes possible to preferentially transfer video data with the stronger possibility of being accessed to the storage unit  121 . 
     The processing unit  123  may give a transfer instruction to the reading unit  11  in such a manner that a video file in which the creation time, update time or the like is close to that of the video file that has been requested to be read is preferentially transferred. 
     The processing unit  123  may give a transfer instruction to the reading unit  11  in such a manner that a video file in which the creation time is the latest is preferentially transferred. 
     The processing unit  123  may give a transfer instruction to the reading unit  11  in such a manner that video data of a logical block on which the leading head of the video file is recorded for the convenience of preview or the like is preferentially transferred. 
     An order determination unit for determining the transfer order of video data by predicting a video file which will become an object of a read request from the past tendency of access from the non-linear editing unit  30  is provided in the video server  12 . Further, the processing unit  123  may give a transfer instruction to the reading unit  11  in such a manner that the video data are transferred preferentially in accordance with the order determined by the order determination unit. 
     Next, the case where after the preparation of  FIG. 5  is completed, a request to read a video file recorded on the removable storage medium  20  is received from the non-linear editing unit  30  will be described below.  FIG. 9  is a sequence diagram at that time. 
     In  FIG. 9 , on receiving a request to read the video file from the non-linear editing unit  30 , the processing unit  123  refers to the file management table of the memory  122  to specify a logical block to be accessed. When the logical block to be accessed is specified, the processing unit  123  refers to the device ID and physical address shown in the block management table of the memory  122  to determine whether or not the video file which is requested to be read has already been transferred to the storage unit  121  (S 91 ). That is, the processing unit  123  determines whether the video data of the video file is recorded on one of the removable storage medium  20  or storage unit  121 . 
     When the video data of the video file is recorded on the storage unit  121 , the processing unit  123  transfers the read request to the storage unit  121 . On receiving the read request, the storage unit  121  outputs in sequence the video data of the video file which is requested to be read to the non-linear editing unit  30 . 
     In the case where the video data of the video file is recorded on the removable storage medium  20 , the processing unit  123  transfers the read request to the reading unit  11  (S 92 ). On receiving the read request, the reading unit  11  reads the video data of the video file which is requested to be read from the removable storage medium  20 . The processing unit  123  outputs in sequence the video data read by the reading unit  11  to the non-linear editing unit  30  (S 93 ). 
     When the processing unit  123  outputs the video data to the non-linear editing unit  30 , the unit  123  writes the video data to the storage unit  121  in sequence (S 94 ). On completing the recording of the video data on the storage unit  121 , the processing unit  123  updates the block management table of the memory  122  on the basis of the write location of the video data (S 95 ). Further, on completing the transfer of the video file to the storage unit  121 , the processing unit  123  updates the file management table and the block management table of the storage unit  121  on the basis of the file management table and the block management table of the memory  122  (S 96 ). 
     When the output of the video file requested by the non-linear editing unit  30  is completed, the processing unit  123  notifies the non-linear editing unit  30  that the output of the video file is completed. 
       FIG. 10  is a schematic view showing the states of the removable storage medium  20 , memory  122 , and storage unit  121  in the case where a request to read the video content  1  is input from the non-linear editing unit  30 .  FIG. 10A  shows the states of the removable storage medium  20 .  FIG. 10B  shows the states of the memory  122 .  FIG. 10C  shows the states of the storage unit  121 . 
     On receiving the read request of the video content  1  from the non-linear editing unit  30 , the processing unit  123  refers to the file management table and the block management table of the memory  122  to determine that the video content  1  is recorded on the removable storage medium  20  (S 91 ). The processing unit  123  transfers the read request of the video content  1  to the reading unit  11  (S 92 ). On receiving the read request, the reading unit  11  reads the video data of the video content  1  from the removable storage medium  20  (S 93 ). The processing unit  123  outputs the read video data to the non-linear editing unit  30  in sequence. 
     When the processing unit  123  outputs the video data of the video content  1  to the non-linear editing unit  30 , the unit  123  writes the video data in sequence to the video server  12  (S 94 ). As a result of this, the video data transferred from the removable storage medium  20  is recorded on the unassigned addresses: h00000004 and h00000005 of the storage unit  121 . When the processing unit  123  has written the video data to the logical block of the storage unit  121 , the unit  123  updates the block management table of the memory  122  on the basis of the write location thereof (S 95 ). As a result of this, the device IDs of the logical block Nos.: L001 and L002 of the memory  122  become D002, and the physical addresses become h00000004 and h00000005. Further, on completing the transfer of the video content  1 , the processing unit  123  updates the file management table and the block management table of the storage unit  121  on the basis of the file management table and the block management table of the memory  122  (S 96 ). 
     As described above, in the video data processing system  10 , if the read request of the video file is input from the non-linear editing unit  30 , the storage position of the video data of the requested video file is determined by referring to the file management table and the block management table of the memory  122 . Further, if the storage position of the video data is determined, the processing unit  123  outputs the video file to the non-linear editing unit  30  by reading the video data in sequence from the storage position of the video data. As a result of this, it becomes possible for the video data processing system  10  to output the video file to the non-linear editing unit  30 , even if the video file of the removable storage medium  20  has not been transferred to the storage unit  121 . That is, it is possible for the non-linear editing unit  30  to start non-linear editing of the video file even if the video file recorded on the removable storage medium  20  has not been transferred to the storage unit  121 . 
     In the case where a video file which will become an object of a read request is recorded on the removable storage medium  20 , the video data processing system  10  outputs the video data thereof to the non-linear editing unit  30 , and simultaneously writes the video data to the storage unit  121 . As a result of this, the transfer efficiency of the video file is improved. 
     Next, the case where after the preparation of  FIG. 5  is completed, a write request of an edited video file is received from the non-linear editing unit  30  will be described below.  FIG. 11  is a sequence diagram at that time. Further,  FIG. 12  is a schematic view showing the states of the removable storage medium  20 , memory  122 , and storage unit  121  in the case where a write request of the edited video  1  is input from the non-linear editing unit  30 .  FIG. 12A  shows the states of the removable storage medium  20 .  FIG. 12B  shows the states of the memory  122 .  FIG. 12C  shows the states of the storage unit  121 . 
     In  FIG. 11 , on receiving a write request of an edited video file: the edited video  1  from the non-linear editing unit  30 , the processing unit  123  transfers the write request to the storage unit  121  to write the edited video  1  to the storage unit  121  (S 111 ). As a result of this, the edited video  1  is written to the logical block (physical address: h00000004) of the storage unit  121 . Further, the processing unit  123  updates the file management table and the block management table of the storage unit  121  (S 112 ). The processing unit  123  updates the file management table and the block management table of the memory  122  on the basis of the write location of the video data in the storage unit  121  (S 113 ). 
     As described above, after recording the edited video file on the storage unit  121 , the processing unit  123  updates the file management table and the block management table of the memory  122  on the basis of the file management table and the block management table of the storage unit  121 . As a result of this, in the video data processing system, the edited video file is always recorded on the storage unit  121 , and the video file recorded on the storage unit  121  is also managed at the memory  122 . 
     From the above description, according to the video data processing system of the present invention, it is possible to start non-linear editing of the acquired video file without waiting time. 
     In the video data processing system according to this embodiment, in the file management table of each of the removable storage medium  20 , memory  122 , and storage unit  121 , a unique file ID is imparted to each video file. As a result of this, it becomes possible to limit transfer of video files with the same file ID by collating the file ID of a video file transferred from the removable storage medium  20  to the storage unit  121  and the file ID of a video file recorded on the storage unit  121  with each other. 
     It should be noted that the processing of the video data processing system according to this embodiment is not limited to the above-mentioned content. For example, the transfer of the video file does not necessarily conform to the sequence shown in  FIG. 7 , and can also be carried out in accordance with the sequence shown in  FIG. 13 .  FIG. 14  is a schematic view showing the states of the removable storage medium  20 , memory  122 , and storage unit  121  in the case where the video data processing system  10  carries out the processing shown in  FIG. 13 .  FIG. 14A  shows the states of the removable storage medium  20 .  FIG. 14B  shows the states of the memory  122 .  FIG. 14C  shows the states of the storage unit  121 . 
     That is, in  FIG. 13 , the processing unit  123  updates the block management table of the storage unit  121  on the basis of the block management table of the memory  122  (S 131 ). That is, the states of the logical block Nos.: L105 to L109 and L120 to L122 are rewritten to be changed to “busy (in use)”, the device ID is rewritten to be changed to D001, and the physical address is rewritten to be changed to the same physical address as the physical address of the memory  122 . Subsequently, the processing unit  123  updates the file management table of the storage unit  121  on the basis of the file management table of the memory  122  (S 132 ). That is, the video contents  1  to  3  recorded on the removable storage medium  20  are written to the file management table of the storage unit  121 . 
     When the file management table of the storage unit  121  is updated, the processing unit  123  gives an instruction to transfer the video content  1  which is a video file recorded on the removable storage medium  20  to the reading unit  11 . On receiving this instruction, the reading unit  11  transfers the video content  1  to the video server  12  in units of video data. The processing unit  123  records the video data transferred from the removable storage medium  20  on the unassigned address: h00000004 of the storage unit  121  (S 133 ). 
     The processing unit  123  updates the block management table of the memory  122  on the basis of the write location of the video data in the storage unit  121 , sets the device ID of the logical block No.: L001 to D002, and sets the physical address to h00000004 (S 134 ). Further, the processing unit  123  updates the block management table of the storage unit  121  on the basis of the write location of the video data in the storage unit  121 , sets the device ID of the logical block No.: L105 to D002, and sets the physical address to h00000004 (S 135 ). 
     Having updated the block management tables of the memory  122  and storage unit  121 , the processing unit  123  gives an instruction to transfer the next video data to the reading unit  11 . The reading unit  11  reads the next video data from the removable storage medium  20 , and transfers the video data to the video server  12  (S 136 ). The processing unit  123  records the video data transferred from the removable storage medium  20  on the unassigned address: h00000005 of the storage unit  121 . 
     The processing unit  123  updates the block management table of the memory  122  on the basis of the write location of the video data in the storage unit  121 , sets the device ID of the logical block No.: L002 to D002, and sets the physical address to h00000005 (S 137 ). Further, the processing unit  123  updates the block management table of the storage unit  121  on the basis of the write location of the video data in the storage unit  121 , sets the device ID of the logical block No.: L106 to D002, and sets the physical address to h00000005 (S 138 ). As a result of this, the video content  1  is transferred from the removable storage medium  20  to the storage unit  121 . 
     The video data processing system  10  repeats the processing of S 133  to S 138  to transfer the video contents  2  and  3  which have been written to the file management table and the block management table of the storage unit  121  by the processing of S 131  and S 132  from the removable storage medium  20  to the storage unit  121 . 
     As a result of this, even before the video file is transferred from the removable storage medium  20  to the storage unit  121 , the file management table and the block management table of the removable storage medium  20  are merged into the file management table and the block management table of the storage unit  121 . Thus, in the file management table and the block management table of the storage unit  121 , the video file recorded on the removable storage medium  20  is also managed. 
     In the video data processing system according to this embodiment, the transfer processing of the video file may be carried out in the following manner to improve the performance of the editing processing to be carried out by the non-linear editing unit  30 . 
     That is, If the read request or write request is not input from the non-linear editing unit  30  for a predetermined time, the processing unit  123  may give a transfer instruction to the reading unit  11 . As a result of this, while the processing for the read request or write request from the non-linear editing unit  30  is carried out, the video data processing system  10  does not carry out transfer of the video file in the background. That is, it becomes possible for the video data processing system  10  to make the editing operation prior to the transfer of the video file. 
     The processing unit  123  may be provided with a cache for temporarily storing video data transferred from the removable storage medium  20  to the storage unit  121 , and may refer to the cache data to output the video data of the video file which has been requested to be read to the non-linear editing unit  30 . 
     Second Embodiment 
       FIG. 15  is a schematic view showing the configuration of a video data processing system  50  according to a second embodiment of the present invention. The video data processing system  50  is provided with a reading unit  11 , a gateway server  51 , and a video server  52 . A non-linear editing unit  30  is connected to the gateway server  51 . 
     A video file recorded on a removable storage medium  20  is read by the reading unit  11 , and is transferred to the video server  52  through the gateway server  51  to be recorded. 
     The video server  52  is provided with, for example, a semiconductor storage medium such as a flash memory and the like, or a storage medium such as a hard disk and the like, and records a video file transferred thereto. On the video server  52 , a file management table for managing the recorded video file, and a block management table for managing the recording state of the storage medium are recorded in advance. The video server  52  updates these tables in accordance with an instruction from the gateway server  51 . 
     The gateway server  51  is provided with a processing unit  511 , and a memory  512 . The processing unit  511  is embodied as a controller for controlling the memory  512  and the video server  52 , and is configured by a microprocessor such as a CPU or the like. As the memory  512 , for example, a RAM is used. 
     When the removable storage medium  20  is connected to the reading unit  11 , the processing unit  511  updates the file management table and the block management table recorded in advance on each of the memory  512  and video server  52 , prepares to transfer a video file recorded on the removable storage medium  20  to the video server  52 , and prepares to carry out non-linear editing of the video file by using the non-linear editing unit  30 . 
     If the preparation for transfer of the video file recorded on the removable storage medium  20  is completed, the processing unit  511  transfers the video file to the video server  52 , and updates the file management tables and block management tables of the memory  512  and video server  52 . 
     If the processing unit  511  receives a request to read the video file from the non-linear editing unit  30 , the unit  123  outputs the requested video file to the non-linear editing unit  30  by referring to the file management tables and block management tables recorded on the removable storage medium  20 , memory  512 , and video server  52 . 
     If the processing unit  511  receives a request to write the video file from the non-linear editing unit  30 , the unit  511  transfers the video file to the video server  52 , and causes the video server  52  to record the video file. Further, the processing unit  511  updates the file management tables and block management tables of the video server  52  and memory  512 . 
     The non-linear editing unit  30  accesses the gateway server  51 , and requests the gateway server  51  to read a video file desired to be edited. Further, the non-linear editing unit  30  requests the gateway server  51  to write the video file that has already been edited. 
     Next, the processing operation of the video data processing system  50  configured as described above will be described below. It should be noted that in this embodiment, a device ID: D001 indicates the removable storage medium  20 , and device ID: D002 indicates the video server  52 . 
       FIG. 16  is a sequence diagram of a case where the video data processing system  50  according to the second embodiment of the present invention prepares to transfer a video file recorded on the removable storage medium  20  to the video server  52 , and prepares to carry out non-linear editing of the video file by using the non-linear editing unit  30 . Further,  FIG. 17  is a schematic view showing the states of the removable storage medium  20 , gateway server  51 , and video server  52  in the case where the video data processing system  50  carries out the processing shown in  FIG. 16 .  FIG. 17A  shows the states of the removable storage medium  20 .  FIG. 17B  shows the states of the gateway server  51 .  FIG. 17C  shows the states of the video server  52 . 
     In  FIG. 16 , when the removable storage medium  20  is set, the reading unit  11  notifies the gateway server  51  that the removable storage medium  20  is set. On receiving the notification indicating that the removable storage medium  20  is set, the processing unit  511  requests the reading unit  11  to provide information about the file management table. The reading unit  11  outputs the information about the file management table of the removable storage medium  20  to the gateway server  51 . 
     The processing unit  511  updates the file management table of the memory  512  on the basis of the information about the file management table (S 161 ). As a result of this, the information of the file management table of the removable storage medium  20  is written to the file management table of the memory  512 . 
     Subsequently, the processing unit  511  calculates a storage area necessary for recording video contents  1  to  3  on the storage unit  121  (S 162 ), and issues an instruction to secure a logical block on the basis of the calculated storage area to the video server  52  (S 163 ). The video server  52  secures, on the basis of the calculated result, logical block Nos.: L105 and L106 to record the video content  1 , secures logical block Nos.: L107 to L109 to record the video content  2 , and secures logical block Nos.: L120 to L122 to record the video content  3 . The video server  52  notifies the processing unit  511  that securing the storage area is complete. On receiving the notification, the processing unit  511  transfers it to the reading unit  11 , which, as a result, outputs information about the block management table of the removable storage medium  20  to the processing unit  511 . The processing unit  511  updates the block management table of the memory  512  on the basis of the information about the block management table (S 164 ). 
     If the removable storage medium  20  is set at the reading unit  11  as described above, the video data processing system  50  updates the file management table and the block management table of the memory  512  on the basis of the file management table and the block management table of the removable storage medium  20 . That is, in the memory  512 , the management table of the removable storage medium  20  is managed. As a result of this, it can be considered that the video file recorded on the removable storage medium  20  is virtually recorded on the video server  52 . 
     Processing to be performed after the preparation for transfer of the video file recorded on the removable storage medium  20  to the video server  52 , and the preparation for non-linear editing of the video file by using the non-linear editing unit  30  have been completed by the processing shown in  FIG. 16  will be described below. 
     First, the case where after the processing shown in  FIG. 16  is completed, the video file is transferred from the removable storage medium  20  to the video server  52  in the background will be described below.  FIG. 18  is a sequence diagram at the time. Further,  FIG. 19  is a schematic view showing the states of the removable storage medium  20 , gateway server  51 , and video server  52  in the case where the video data processing system  50  carries out the processing shown in  FIG. 18 .  FIG. 19A  shows the states of the removable storage medium  20 .  FIG. 19B  shows the states of the gateway server  51 .  FIG. 19C  shows the states of the video server  52 . 
     In  FIG. 18 , the processing unit  511  gives an instruction to transfer the video content  1  which is the video file recorded on the removable storage medium  20  to the reading unit  11 . On receiving the instruction, the reading unit  11  transfers the video content  1  to the video server  12  in units of video data (S 181 ). The video server  52  receives the video data transferred from the removable storage medium  20 , and records the video data on an unassigned address: h00000004. On completing the recording of the video data, the video server  52  notifies the gateway server  51  of the write location of the video data. The processing unit  511  updates the block management table of the memory  512  on the basis of the notified write location, sets the device ID of the logical block No.: L001 to D002, and sets the physical address to h00000004 (S 182 ). 
     When the block management table of the memory  512  is updated, the processing unit  511  gives the reading unit  11  an instruction to transfer the next video data. The reading unit  11  reads the next video data from the removable storage medium  20 , and transfers the video data to the video server  52  (S 183 ). The video server  52  receives the video data transferred from the removable storage medium  20 , and records the video data on an unassigned address: h00000005. When the recording of the video data is completed, the video server  52  notifies the gateway server  51  of the write location of the video data. The processing unit  511  updates the block management table of the memory  512  on the basis of the notified write location, sets the device ID of the logical block No.: L002 to D002, and sets the physical address to h00000005 (S 184 ). As a result of this, the video content  1  is transferred from the removable storage medium  20  to the video server  52 . 
     The video data processing system  50  repeats the processing of S 181  to S 184  to transfer the video contents  2  and  3  which are video files recorded on the removable storage medium  20  to the video server  52 . Further, on completing the transfer of the video files recorded on the removable storage medium  20 , the reading unit  11  notifies the gateway server  51  that the transfer of the video files recorded on the removable storage medium  20  has been completed. On receiving the notification indicating that the transfer has been completed, the processing unit  511  outputs information about the block management table of the memory  512  to the video server  52 . The video server  52  updates the block management table on the basis of the information supplied from the gateway server  51  (S 185 ). That is, the device IDs and physical addresses of the logical block Nos.: L105 to L109, and L120 to L122 in the video server  52  are rewritten to be changed to the device IDs and physical addresses of the logical block Nos.: L001 to L005, and L010 to L012 in the memory  512 , and the states of the logical block Nos.: L105 to L109, and L120 to L122 in the video server  52  are rewritten to be changed to “busy (in use)”. Subsequently, the processing unit  511  outputs information about the file management table of the memory  512  to the video server  52 . The video server  52  updates the file management table on the basis of the information supplied from the gateway server  51  (S 186 ). That is, the video contents  1  to  3  transferred from the removable storage medium  20  are written to the file management table of the video server  52 . As a result of this, the transfer processing is completed. 
     As described above, the processing unit  511  transfers the video data from the reading unit  11  to the video server  52 , and updates the block management table of the memory  512 . Further, if the transfer of the video data is completed, the processing unit  511  updates the file management table and the block management table of the video server  52  on the basis of the file management table and the block management table of the memory  512 . As a result of this, in the video data processing system  50 , it becomes possible, after the completion of the video file transfer, to merge the file management table and the block management table of the memory  512  into the file management table and the block management table of the video server  52 . Accordingly, it becomes possible to improve the transfer efficiency of the video file. It should be noted that this transfer processing can be executed while the non-linear editing is executed by the non-linear editing unit  30 . 
     The video files with the stronger possibility of being accessed are transferred to the video server earlier, whereby it becomes possible to improve the response speed with respect to the editing operation. Specific examples of the above will be shown below. 
     The processing unit  511  may give a transfer instruction to the reading unit  11  in such a manner that video data of a plurality of consecutive logical blocks on which video files which become objects of read requests are recorded is preferentially transferred. As a result of this, video data with the stronger possibility of being accessed is transferred to the video server  52 . 
     The processing unit  511  may give a transfer instruction to the reading unit  11  in such a manner that a video file in which the creation time, update time or the like is close to that of the video file that has been requested to be read is preferentially transferred. 
     The processing unit  511  may give a transfer instruction to the reading unit  11  in such a manner that a video file in which the creation time is the latest is preferentially transferred. 
     The processing unit  511  may give a transfer instruction to the reading unit  11  in such a manner that video data of a logical block on which the leading head of the video file is recorded for the convenience of preview or the like is preferentially transferred. 
     An order determination unit is further provided in the gateway server  51 . Further, the processing unit  511  may give a transfer instruction to the reading unit  11  in such a manner that the video data are transferred preferentially in accordance with the order determined by the order determination unit. 
     Next, the case where after the preparation of  FIG. 16  is completed, a request to read a video file recorded on the removable storage medium  20  is received from the non-linear editing unit  30  will be described below.  FIG. 20  is a sequence diagram at that time. 
     In  FIG. 20 , on receiving a request to read the video file from the non-linear editing unit  30 , the processing unit  511  refers to the file management table of the memory  512  to specify a logical block to be accessed. When the logical block to be accessed is specified, the processing unit  511  refers to the device ID and physical address shown in the block management table of the memory  512  to determine whether or not the video file which is requested to be read has already been transferred to the video server  52  (S 201 ). That is, the processing unit  511  determines whether the video data of the video file is recorded on one of the removable storage medium  20  or video server  52 . 
     When the video data of the video file is recorded on the video server  52 , the processing unit  511  transfers the read request to the video server  52 . On receiving the read request, the video server  52  outputs in sequence the video data of the video file which is requested to be read to the gateway server  51 . The processing unit  511  transfers in sequence the video data output from the video server  52  to the non-linear editing unit  30 . 
     In the case where the video data of the video file is recorded on the removable storage medium  20 , the processing unit  511  transfers the read request to the reading unit  11  (S 202 ). On receiving the read request, the reading unit  11  reads the video data of the video file which is requested to be read from the removable storage medium  20 . The processing unit  511  transfers in sequence the video data read by the reading unit  11  to the non-linear editing unit  30  (S 203 ). 
     When the processing unit  511  transfers the video data to the non-linear editing unit  30 , the unit  511  transfers the video data to the video server  52  in sequence (S 204 ). The video server  52  receives the video data transferred in sequence from the gateway server  51 , and records the video data on an unassigned address. On completing the recording of the video data, the video server  52  notifies the processing unit  511  of the write location of the video data. The processing unit  511  updates the block management table of the memory  512  on the basis of the notified write location (S 205 ). Further, on completing the transfer of the video file to the video server  52 , the processing unit  511  updates the file management table and the block management table of the video server  52  on the basis of the file management table and the block management table of the memory  512  (S 206 ). 
     When the output of the video file requested by the non-linear editing unit  30  is completed, the processing unit  511  notifies the non-linear editing unit  30  that the output of the video file is completed. 
       FIG. 21  is a schematic view showing the states of the removable storage medium  20 , gateway server  51 , and video server  52  in the case where a request to read the video content  1  is input from the non-linear editing unit  30 .  FIG. 21A  shows the states of the removable storage medium  20 .  FIG. 21B  shows the states of the gateway server  51 .  FIG. 21C  shows the states of the video server  52 . 
     On receiving the read request of the video content  1  from the non-linear editing unit  30 , the processing unit  511  refers to the file management table and the block management table of the memory  512  to determine that the video content  1  is recorded on the removable storage medium  20  (S 201 ). The processing unit  511  transfers the read request of the video content  1  to the reading unit  11  (S 202 ). On receiving the read request, the reading unit  11  reads the video data of the video content  1  from the removable storage medium  20 . The processing unit  511  transfers the read video data to the non-linear editing unit  30  in sequence (S 203 ). 
     When the processing unit  511  outputs the video data of the video content  1  to the non-linear editing unit  30 , the unit  511  transfers the video data in sequence to the video server  12  (S 204 ). The video server  52  receives the transferred video data, and records the video data in sequence on the unassigned addresses: h00000004 and h00000005. On completing the recording of the video data, the video server  52  notifies the processing unit  511  of the write location of the video data. The processing unit  511  updates the block management table of the memory  512  on the basis of the notified write location (S 205 ), sets the device IDs of the logical block Nos.: L001 and L002 of the memory  512  to D002, and sets the physical addresses to h00000004 and h00000005. Further, on completing the transfer of the video content  1 , the processing unit  511  updates the file management table and the block management table of the video server  52  on the basis of the file management table and the block management table of the memory  512  (S 206 ). 
     As described above, in the video data processing system  50 , if the read request of the video file is input from the non-linear editing unit  30 , the storage position of the video data of the requested video file is determined by referring to the management tables of the memory  512 . Further, if the storage position of the video data is determined, the processing unit  511  transfers the video data read from storage position in sequence to the non-linear editing unit  30 . As a result of this, it becomes possible for the video data processing system  50  to transfer the video file to the non-linear editing unit  30 , even if the video file of the removable storage medium  20  has not been transferred to the video server  52 . That is, it is possible for the non-linear editing unit  30  to start non-linear editing of the video file even if the video file recorded on the removable storage medium  20  has not been yet transferred to the video server  52 . 
     In the case where a video file which will become an object of a read request is recorded on the removable storage medium  20 , the video data processing system  50  outputs the video data thereof to the non-linear editing unit  30 , and simultaneously writes the video data to the video server  52 . As a result of this, the transfer efficiency of the video file is improved. 
     Next, the case where after the preparation of  FIG. 16  is completed, a write request of an edited video file is received from the non-linear editing unit  30  will be described below.  FIG. 22  is a sequence diagram at that time. Further,  FIG. 23  is a schematic view showing the states of the removable storage medium  20 , gateway server  51 , and video server  52  in the case where a write request of the edited video  1  is input from the non-linear editing unit  30 . 
     In  FIG. 22 , on receiving a write request of an edited video file: the edited video  1  from the non-linear editing unit  30 , the processing unit  511  transfers the write request to the video server  52 . On receiving the write request, the video server  52  writes the video data of the edited video  1  to the physical address: h00000004 (S 221 ). Further, on completing the writing of the video data, the video server  52  updates the file management table and the block management table (S 222 ), and notifies the gateway server  51  of the write location of the video data. The processing unit  511  updates the file management table and the block management table of the memory  512  on the basis of the notification of the write location from the video server  52  (S 223 ). 
     As described above, on receiving the write request of the edited video file, the gateway server  51  transfers the video file to the video server  52  to cause the video server  52  to record the video file. Further, after causing the video server  52  to record the video file, the gateway server  51  updates the file management table and the block management table of the memory  512  on the basis of the file management table and the block management table of the video server  52 . As a result of this, in the video data processing system  50 , the edited video file is also managed at the memory  512  of the gateway server  51 . 
     From the above description, according to the video data processing system of the present invention, it is possible to start non-linear editing of the acquired video file without waiting time. 
     Other Embodiments 
     It should be noted that the present invention is not limited to the embodiments described above. For example, in each of the above-mentioned embodiments, the case where the reading unit  11  reads the video file and management tables from the removable storage medium  20 , the video file and management tables being recorded on the inside of the medium  20 , has been described. However, the operation of the reading unit  11  is not limited to reading data from the removable storage medium  20 . For example, in the case where the camera is provided with an incorporated storage medium, the reading unit  11  may directly read the video file and management tables from the incorporated storage medium of the camera. 
     In each of the above embodiments, the example in which a semiconductor storage medium such as a flash memory and the like, or a storage medium such as a hard disk and the like is used is described. Here, in the case where a disk medium is used as the removable storage medium  20 , if a plurality of processing items are simultaneously executed, the processing changeover overhead is large because of the seek time. Accordingly, in the present invention, employing a semiconductor storage medium such as a flash memory and the like as the removable storage medium  20  makes it possible to efficiently carry out the processing if an access for the editing operation and transfer processing of video data are concurrently carried out. 
     In each of the above embodiments, the example in which a read request and write request concomitant with the editing processing carried out by the non-linear editing unit  30  are received has been described. However, the access from outside is not limited to the non-linear editing unit  30 . For example, a case where access processing is applied to the video server by a decoder device or the like is also practicable. 
     In each of the above embodiments, the example in which the terminal accessing from outside is only the non-linear editing unit  30  has been described. However, the external terminal is not limited to one. It should be noted that in the case where there are a plurality of external terminals, an order imparting unit for imparting the priority order to each of the external terminals may further be provided in the video server  12  or gateway server  51 . As a result of this, if read requests are received from the plurality of external terminals, it becomes possible for the video server  12  or gateway server  51  to preferentially transfer video data to external terminals to which high priority order is imparted by the order imparting unit. 
     Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.