Abstract:
A video data processing apparatus includes a reading unit reading video data from a video data file recorded on a randomly accessible storage medium in response to a first control signal, and reading position data indicating a frame position of the video data in the video data file from the video data file recorded on the storage medium in response to a second control signal, a memory storing the position data read by the reading unit, and a controller controlling the reading unit by outputting the second control signal before the outputting of the first control signal, and controlling the reading unit by outputting the first control signal with a designation of particular video data to be read indicated by the position data stored in the memory, in response to a request to execute a process to the video data file.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2008-235141, filed Sep. 12, 2008, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a video data processing apparatus and video data processing method for reproducing video data recorded on an attachable/detachable semiconductor storage medium. 
     2. Description of the Related Art 
     Heretofore, as for a video data processing apparatus for commercial use employed in a broadcasting station or the like, a system in which video data is recorded on a tape has been the main stream. In the video data processing apparatus of this kind, it is necessary to record video data in sequence from the leading head of a tape. Accordingly, in order to reproduce the recorded data, it is necessary to acquire a desired reproduction position by carrying out fast-forwarding or the like of the tape. Thus, a lot of time has been required to start reproduction. 
     In recent years, a semiconductor storage medium such as a flash memory has become to be used in place of the tape (for example, Jpn. Pat. Appln. KOKAI Publication No. 2002-184159 and Jpn. Pat. Appln. KOKAI Publication No. 2004-104337). The semiconductor storage medium is randomly accessible, and hence in a video data processing apparatus in which a semiconductor storage medium is used, if video data is subjected to reproduction or the like from an arbitrary position, a far higher-speed operation than that of the tape system is enabled. 
     However, even in the video data processing apparatus in which a semiconductor storage medium is used, in the case where video data of high image quality and large volume is reproduced, although an instruction to start reproduction is issued, it takes some time to actually start a reproduction operation. Thus, in order to improve the operability of the user, a further higher-speed operation is demanded. 
     BRIEF SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a video data processing apparatus and video data processing method capable of quickly starting a reproduction operation of video data. 
     According to an aspect of the present invention, there is provide a video data processing apparatus comprising: a reading unit for reading video data from a video data file recorded on a randomly accessible storage medium in response to a first control signal, and for reading position data indicating a frame position of the video data in the video data file from the video data file recorded on the storage medium in response to a second control signal; a memory for storing the position data read by the reading unit; and a controller for controlling the reading unit by outputting the second control signal before the outputting of the first control signal, and for controlling the reading unit by outputting the first control signal with a designation of particular video data to be read indicated by the position data stored in the memory, in response to a request to execute a process to the video data file. 
     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 of a video data processing apparatus according to a first embodiment of the present invention. 
         FIG. 2  is a view showing the structure of a video data file recorded on the storage medium shown in  FIG. 1 . 
         FIG. 3  is a block diagram showing the structure of the video data processing apparatus of  FIG. 1 . 
         FIG. 4  is a view showing the read rate in the case where the interface unit shown in  FIG. 3  reads data from a removable storage medium. 
         FIG. 5  is a flowchart showing a processing operation to be performed when the controller of  FIG. 3  stores index data in a RAM. 
         FIG. 6  is a view showing a position information table of index data stored in a storage area of a RAM by the processing operation shown in  FIG. 5 . 
         FIG. 7  is a flowchart showing a processing operation of the controller to be performed when the video data processing apparatus shown in  FIG. 1  receives an instruction to start reproduction. 
         FIG. 8  is a flowchart showing a processing operation to be performed when the controller of the video data processing apparatus according to a second embodiment of the present invention stores index data in the RAM. 
         FIG. 9  is a view showing position information tables of index data to be stored in the storage areas of the RAM by the processing operation shown in  FIG. 8 . 
         FIG. 10  is a flowchart showing a processing operation of the controller to be performed when the video data processing apparatus according to a second embodiment receives an instruction to start reproduction. 
         FIG. 11  is a view showing index data to be stored in the storage areas of the RAM at the time of the reproduction processing shown in  FIG. 10 . 
         FIG. 12  is a flowchart showing a processing operation of the controller to be performed when the video data processing apparatus according to a second embodiment receives an instruction to start reproduction. 
         FIG. 13  is a view showing index data to be stored in the storage areas of the RAM at the time of the reproduction processing shown in  FIG. 12 . 
         FIG. 14  is a view showing position information tables stored in the RAM shown in  FIG. 3 . 
         FIG. 15  is a flowchart showing a processing operation to be performed when the controller of the video data processing apparatus according to a third embodiment of the present invention stores index data in the RAM. 
         FIG. 16  is a view showing a display example of thumbnail images of the display unit of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments of a video data processing apparatus according to the present invention will be described below in detail while referring to the accompanying drawings. 
     First Embodiment 
       FIG. 1  is an outline view of a video data processing apparatus  10  according to a first embodiment of the present invention. A camera  20  is connected to the video data processing apparatus  10  in  FIG. 1 . A video image or picture image taken by the camera  20  is captured in the video data processing apparatus  10 . The captured image is recorded on a removable storage medium  30  or a built-in storage medium  12  as a video data file. The storage medium  30  is inserted into an insertion opening  11 . The storage medium  12  is incorporated in the apparatus main body. 
     As the storage media  12  and  30 , a nonvolatile semiconductor memory, hard disk and the like which are randomly accessible are used. The nonvolatile semiconductor memory is, for example, a flash memory or the like. The flash memory is provided with the advantage of rewritability and high random accessibility. Further as the flash memory is provided with no mechanical moving part unlike a tape and optical disk drive, the flash memory is excellent in resistance against vibration and the like. 
     A display unit  14 , a video operation unit  15 , and a screen operation unit  16  are provided on a main body front panel of the video data processing apparatus  10 . 
     The display unit  14  is constituted of, for example, a Liquid Crystal Display (LCD). The display unit  14  displays, for example, setup information of the video data processing apparatus  10 . 
     The video operation unit  15  is provided with various buttons and a dial. The user can input an instruction to start reproduction or instruction to stop reproduction of a video data file recorded on the storage medium  12  or  30  by operating these buttons. Further, the user can carry out adjustment or the like of the reproduction speed by operating the dial. 
     The screen operation unit  16  is provided with various buttons. The user can input an instruction to start reproduction of the video data file recorded on the storage medium  12  or  30  by operating these buttons. 
       FIG. 2  is a schematic view showing the structure of the video data file recorded on the storage medium  30 . The video data file in  FIG. 2  is provided with a header part, video data part, index part, and footer part. The header part stores therein attribute data such as a format type and the like of the video data file. The video data part stores therein a video data main body, and is divided into data items in units of frames. At this time, the data length of each video data item differs from each other. The index part stores therein data lengths a, b, c, d . . . from the head position of the file to the head positions of the respective video data items as index data. The footer part indicates the end of the video data file. 
       FIG. 3  is a view showing the functional configuration of the video data processing apparatus  10  according to the embodiment of the present invention. The video data processing apparatus  10  is provided with a controller  17  constituted of a Central Processing Unit (CPU) such as a microprocessor or the like. The controller  17  is connected to an interface unit  18  for the storage medium  30 , interface unit  19  for the storage medium  12 , encoder  110 , decoder  111 , input unit  112 , output unit  113 , and display unit  14  through a bus. Further, the video operation unit  15 , screen operation unit  16 , and a Random Access Memory (RAM)  114  are connected to the controller  17 . The storage medium  30  is connected to the interface unit  18 , and storage unit  12  is connected to the interface unit  19 . A video data file is recorded on the storage medium  30 . 
     The interface unit  18  reads index data and video data of the video data file recorded on the storage medium  30  in accordance with an instruction from the controller  17 . 
       FIG. 4  is a view showing the read rate in the case where the interface unit  18  reads data from the storage medium  30 . As shown in  FIG. 4 , when the one readout volume is equal to the volume α a or larger, the read rate is saturated at substantially a fixed value. As a result of this, when the data is read at a readout volume smaller than the readout volume α, the read rate is lower than the saturated value, and it can be seen that the reading is inefficient. Conversely, when the readout volume is made equal to or larger than the readout volume α, it is possible to read the data efficiently. The interface unit  18  according to this embodiment reads index data of the volume α from the storage medium  30  by one readout operation. 
     The RAM  114  is provided with a storage area of the volume α. The RAM  114  stores the index data read by the interface unit  18  in the storage area. Further, the RAM  114  outputs the index data stored in the storage area to the controller  17  in accordance with an instruction from the controller  17 . 
     The decoder  111  decodes the video data read by the interface unit  18 , and outputs the decoded video data to the output unit  113 . An external monitor is connected to the output unit  113 , and the decoded signal is output to the external monitor through the output unit  113 . 
     When the storage medium  30  is connected to the video data processing apparatus  10 , the controller  17  issues an instruction to read the index data of the video data file from the storage medium  30  to the interface unit  18 . The read index data is stored in the RAM  114 . 
     When a reproduction start instruction is input from the video operation unit  15  or screen operation unit  16 , the controller  17  reads one index data item from the storage area of the RAM  114 . Further, the controller  17  issues an instruction to read video data indicated by the index data from the storage medium  30  to the interface unit  18 . The read video data is output to the decoder  111 . 
     The processing operation of the controller  17  of the video data processing apparatus  10  configured as described above will be described below in detail.  FIG. 5  is a flowchart showing the processing operation to be carried out when the controller  17  stores the index data in the RAM  114 . 
     First, the controller determines whether or not the storage medium  30  has been connected to the apparatus  10  (step  5   a ). When the storage medium  30  has been connected to the apparatus  10  (Yes in step  5   a ), the controller  17  issues an instruction to read the index data from the storage medium  30  to the interface unit  18  (step  5   b ). The controller  17  causes the RAM  114  to store the read index data in the storage area thereof (step  5   c ), and terminates the processing. 
       FIG. 6  is a view showing a position information table of the index data stored in the storage area of the RAM by the processing operation shown in  FIG. 5 . In the storage area, n index data items corresponding to the volume α are stored. In the position information table, the numbers 1 to n of frames from the leading head position of the video data file, and the data lengths (byte numbers) from the leading head position to the head positions of the individual video data items are made to correspond to each other. 
       FIG. 7  is a flowchart showing the processing operation of the controller  17  to be carried out when the video data processing apparatus  10  receives a reproduction start instruction. 
     First, the controller  17  determines whether or not a reproduction start instruction has been issued from the video operation unit  15  or screen operation unit  16  (step  7   a ). When the reproduction start instruction has been issued (Yes in step  7   a ), the controller  17  reads one index data item stored in the RAM  114  (step  7   b ). Further, the controller  17  issues an instruction to read video data of one frame indicated by the read index data item to the interface unit  18  (step  7   c ). The read video data is output to the decoder  111 . 
     Subsequently, the controller  17  determines whether or not all the index data items of the volume α stored in the RAM  114  have been read (step  7   d ). When all the index data items of the volume α stored in the RAM  114  have been read (Yes in step  7   d ), the controller  17  issues an instruction to read index data which has not been stored to the interface unit  18 . Then, the controller  17  stores the read index data in the RAM  114  (step  7   e ). After step  7   e , the controller  17  moves the processing to step  7   b  to repeat the reproduction processing. Further, when not all the index data items stored in the RAM  114  have been read (No in step  7   d ), the controller moves the processing to step  7   b  to repeat the reproduction processing. This reproduction processing is stopped when the controller  17  receives a reproduction stop instruction from the video operation unit  15 . 
     As described above, the video data processing apparatus  10  according to the first embodiment stores in advance the index data of the video data file recorded on the storage medium  30  in the RAM  114  prior to reproduction of the video data. If the reproduction start instruction is input, the video data processing apparatus  10  reads the index data from the RAM  114 , and reproduces the video data designated by the index data. 
     In general, it is known that reading of data stored at a predetermined position of the RAM  114  enables higher-speed reading than reading of data stored in the storage medium as a file. That is, in the video data processing apparatus  10  according to this embodiment, the system in which the index data is read from the RAM  114  is employed, whereby the time to read the index data is made shorter than in the conventional apparatus when the video data is reproduced. This makes it possible to quickly read desired video data from the storage medium. As a result of this, for example, if the reproduction system is switched from the forward reproduction to the reverse reproduction, it is possible to quickly read the corresponding video data from the storage medium, and hence it becomes possible to shorten the time necessary for switching of the reproduction system. Further, if the reproduction system is switched from the one-time reproduction to the fast-forward reproduction too, it becomes possible to shorten the time necessary for the switching. That is, the video data processing apparatus  10  can improve the response to the reproduction operation. 
     If the removable storage medium  30  of the attachable/detachable type is connected to the video data processing apparatus  10 , the apparatus  10  reads the index data of the video data file recorded on the storage medium  30 . Then the apparatus  10  stores the index data in the RAM  114 . As a result of this, it becomes unnecessary for the video data processing apparatus  10 , unlike the conventional apparatus, to read the index data from the file recorded on the storage medium  30  after a reproduction start instruction is input by the user. This enables the video data processing apparatus  10  to shorten the time from the reproduction start instruction to the start of the reproduction operation. 
     The interface unit  18  of the video data processing apparatus  10  according to the embodiment reads the index data of the volume α by one readout operation on the basis of the relationship between the read rate and readout volume. Further, the storage area of the RAM  114  is provided with the capacity of the same size as the readout volume α. As a result of this, it becomes possible for the video data processing apparatus  10  to efficiently read the index data from the removable storage medium  30 . By virtue of these facts, it is possible for the video data processing apparatus  10  according to the present invention to quickly start the reproduction operation of the video data. 
     It should be noted that in the case where the video data file which becomes an object of the reproduction is selected, it is also possible to quickly start the reproduction operation of the video data by reading the index data of the video data in the vicinity of the leading head in advance, and reading the remaining index data when the reproduction start instruction is input. 
     Second Embodiment 
     In a second embodiment, the description will be given of the case where a removable storage medium  30  stores therein one video data file or a plurality of video data files, and a RAM  114  is provided with a plurality of storage areas each of which is provided with the capacity α. A controller  17  stores index data read from the removable storage medium  30  in the respective storage areas of the RAM  114 . 
       FIG. 8  is a flowchart showing the processing operation to be carried out when the controller  17  stores the index data in the RAM  114 . 
     First, the controller  17  determines whether or not the removable storage medium  30  has been connected to the video data processing apparatus  10  (step  8   a ). When the storage medium  30  has been connected to the apparatus  10  (Yes in step  8   a ), the controller  17  issues an instruction to read index data of the volume α from the storage medium  30  to an interface unit  18  (step  8   b ). 
     When the index data is read from the storage medium  30 , the controller  17  stores the index data in the storage area of the RAM  114  (step  8   c ), and determines whether or not there is any empty space in the plurality of storage areas of the RAM  20  (step  8   d ). When there is an empty space in the storage areas of the RAM  20  (Yes in step  8   d ), the controller moves the processing to step  8   b , and repeats the processing of step  8   b  and step  8   c  until the empty space is eliminated from the RAM  20 . 
     When there is no empty space in the storage areas of the RAM  20  (No in step  8   d ), the processing is terminated. It should be noted if all the index data items in the video data file have already been read, the processing is terminated even if there is an empty space in the storage areas. 
       FIG. 9  is a view showing position information tables of the index data to be stored in the respective storage areas of the RAM  114  by the processing operation shown in  FIG. 8 . The RAM  114  is provided with the storage areas 1 to N. In each of the storage areas 1 to N, n index data items corresponding to the volume α are stored. In each of the position information tables, the number of frames 1 to n, n+1 to  2   n , . . . , or x+1 to x+n from the leading head position of the video data file, and the data lengths (byte numbers) from the leading head position of the video data file to the head positions of the individual video data items are made to correspond to each other. It should be noted that it is possible for the RAM  114  to store therein all the index data items in the file if the video data file is a file of a small volume. 
       FIGS. 10 and 12  are flowcharts each showing the processing operation of the controller  17  to be carried out when the video data processing apparatus  10  receives a reproduction start instruction. Here, if a plurality of storage areas are present in the RAM  114 , the processing of storing index data in the RAM  114  during the reproduction processing differs depending on the reproduction system of the video data.  FIG. 10  shows the case where the reproduction system of the video data is compatible only with the forward reproduction. 
     The controller  17  determines whether or not a reproduction start instruction has been issued from the video operation unit  15  or screen operation unit  16  (step  10   a ). When the reproduction start instruction has been issued (Yes in step  10   a ), the controller  17  reads one index data item stored in the storage area  1  of the RAM  114  (step  10   b ). Further, the controller  17  issues an instruction to read video data of one frame indicated by the read index data item to the interface unit  18  (step  10   c ). The read video data is output to a decoder  111 . 
     Subsequently, the controller  17  determines whether or not all the index data items of the volume α stored in the storage area  1  of the RAM  114  have been read (step  10   d ). If all the index data items of the volume α stored in the storage area  1  have been read (Yes in step  10   d ), the controller  17  refers to the index data of the storage area  2  to carry out reproduction processing, and simultaneously causes the interface unit  18  to read index data which has not been stored yet, the index data being in the video data file that is now being reproduced. Then the controller  17  stores the read index data in the storage area  1  of the RAM  114  (step  10   e ). After completion of step  10   e , the controller  17  moves the processing to step  10   b  to repeat the reproduction processing. In step  10   d , if not all the index data items stored in the storage area  1  have been read (No in step  10   d ), the controller  17  moves the processing to step  10   b  to repeat the reproduction processing. This reproduction processing is stopped when the controller  17  receives a reproduction stop instruction from the video operation unit  15 . 
       FIG. 11  is a view showing the index data items stored in the storage areas of the RAM  114  at the time of the reproduction processing shown in  FIG. 10 . If the video data is reproduced by referring to the index data of the number of frames n in the storage area  1 , the controller  17  refers to the index data of the number of frames n+1 in the storage area  2  to reproduce the video data. When the controller  17  moves to the storage area  2 , the controller  17  stores index data which has not been stored yet, the index data being in the video data file that is now being reproduced, in the storage area  1 . This causes index data which are ahead of the current reproduction position to be always stored in the RAM  114 . It should be noted that the controller  17  refers to the index data stored in each of the storage areas 1 to N to reproduce the video data until the controller  17  receives a reproduction stop instruction. 
       FIG. 12  is a flowchart showing the processing operation of the controller  17  to be carried out when the video data processing apparatus  10  receives a reproduction start instruction in the case where the reproduction system of the video data is compatible with both the forward reproduction and reverse reproduction. It should be noted that in  FIG. 12 , the same processing flows as  FIG. 10  are denoted by the same step numbers as  FIG. 10 . 
     In step  10   e , the controller  17  determines whether or not all the index data items of the volume α stored in the storage area of the RAM  114  have been read. If all the index data items stored in the storage area have been read (Yes in step  10   e ), the controller  17  refers to the index data in the next storage area to carry out reproduction processing, simultaneously causes the interface unit  18  to read index data which has not been stored yet, the index data being in the video data file that is now being reproduced. Then the controller  17  stores the index data in the predetermined storage area (step  12   a ). 
       FIG. 13  is a view showing the index data items stored in the storage areas of the RAM  114  at the time of the reproduction processing shown in  FIG. 12 . 
     In the case where the reproduction system of the video data processing apparatus is the forward reproduction, when the video data is reproduced by referring to the index data of the number of frames k+n in the storage area K, the controller  17  refers to the index data of the number of frames l+1 in the storage area K+1 to reproduce the video data. When the controller moves to the storage area K+1, the controller  17  stores, in the storage area  1 , index data which has not been stored yet, the index data being in the video data file that is now being reproduced. 
     In the case where the reproduction system of the video data processing apparatus is the reverse reproduction, when the video data is reproduced by referring to the index data of the number of frames k+1 in the storage area K, the controller  17  refers to the index data of the number of frames j+n in the storage area K−1 to reproduce the video data. When the controller moves to the storage area K−1, the controller  17  stores, in the storage area N, index data which has not been stored yet, the index data being in the video data file that is now being reproduced. 
     By storing the index data in the storage areas of the RAM  114  in the manner described above, it becomes possible for the video data processing apparatus  10  to quickly cope with the forward reproduction and reverse reproduction of the video data. 
     Furthermore, in the case where a plurality of video data files are recorded on the storage medium  30 , and a video data file to be subjected to reproduction processing subsequently to the video data file which is now being reproduced is already determined, the controller  17  may store in advance the index data of the video data file to be reproduced next in the storage area of the RAM  114  as shown in  FIG. 14 . This becomes useful for reducing the reading processing, and improvement of the operation response when a plurality of reproduction systems such as fast-forward reproduction, reverse reproduction, and the like are applied to a plurality of files. 
     As described above, in the second embodiment, the RAM  114  includes a plurality of storage areas each of which is provided with the capacity α. Then the controller  17  stores the index data read from the video data file in each storage area. Further, if a reproduction start instruction is issued, the controller  17  reproduces video data indicated by the index data stored in the storage area. 
     If an instruction to change the reproduction system is input, the controller  17  refers also to the index data stored in the other storage area to cope with any change in the reproduction system. That is, the index data which is necessary for the reproduction operation and the change of the reproduction system is read not from the file recorded on the storage medium, but from the storage area of the RAM  114 . As a result of this, even if the read position of the video data is changed concomitantly with the change of the reproduction system such as a temporary halt of the reproduction operation, restart, change of the reproduction speed, jump of the reproduction position, and the like, it becomes possible to shorten the time to read the index data, and improve the responsivity to the operation. 
     Accordingly, it is possible for the video data processing apparatus according to the present invention to quickly cope with the processing operation such as the change of the reproduction system, and the like. 
     Third Embodiment 
     In a third embodiment, the case where a plurality of video data files, and a thumbnail image data file in which thumbnail images (representative images indicated by still images of head parts of images) of the video data files are stored are recorded on a removable storage medium  30  will be described. 
     At this time, a display unit  14  displays thumbnail images of the video data file recorded on the storage medium  30 , and a cursor used to select a thumbnail image. Further, a screen operation unit  16  receives an operation instruction of the cursor displayed on the display unit  14 , and selection instruction of the thumbnail image displayed on the display unit  14  from the user by means of various buttons provided thereon. 
     An interface unit  18  reads index data and video data of the video data file recorded on the storage medium  30  in accordance with an instruction from a controller  17 . Further, the interface unit  18  reads thumbnail image data of the thumbnail image data file in accordance with an instruction from the controller  17 . 
     A RAM  114  is provided with a storage area of the capacity α. Further, the RAM  114  stores the index data read by the interface unit  18  in the storage area. 
     A decoder  111  decodes the video data read by the interface unit  18 , and outputs the decoded video data to an output unit  113 . Further, the decoder  111  decodes the thumbnail image data read by the interface unit  18 , and outputs the decoded thumbnail image data to the display unit  14 . 
     When the storage medium  30  is connected to the apparatus  10 , the controller  17  issues an instruction to read the thumbnail image data of the thumbnail image data file from the storage medium  30  to the interface unit  18 . The controller  17  causes the interface unit  18  to output the read thumbnail image data to the decoder  111 . 
     When a selection instruction of the thumbnail image displayed on the display unit  14  is input from the screen operation unit  16 , the controller  17  issues an instruction to read the index data of the video data file of the thumbnail image from the storage medium  30  to the interface unit  18 . 
     When a reproduction start instruction is input from a video operation unit  15  or the screen operation unit  16 , the controller  17  reads one index data item from the RAM  114 . Further, the controller  17  issues an instruction to read video data indicated by the index data item from the storage medium  30  to the interface unit  18 . The controller  17  causes the interface unit  18  to output the read video data to the decoder  111 . 
     The processing operation of the controller  17  of the video data processing apparatus  10  configured as described above will be described below in detail.  FIG. 15  is a flowchart showing the processing operation to be carried out when the controller  17  stores the index data in the RAM  114 . 
     First, the controller  17  determines whether or not the storage medium  30  has been connected to the apparatus  10  (step  15   a ). When the storage medium  30  has been connected to the apparatus  10  (Yes in step  15   a ), the controller  17  issues an instruction to read the thumbnail image data of the thumbnail image data file from the storage medium  30  to the interface unit  18  (step  15   b ). The read thumbnail image data is decoded by the decoder  111 , and is output to the display unit  14 . 
       FIG. 16  is a schematic view showing a display example of thumbnail images of the display unit  14  in the third embodiment of the present invention. An example in which six thumbnail images are displayed on the display unit  14 , and a cursor is positioned on a thumbnail image  5  is shown. 
     After completion of step  15   b , the controller  17  determines whether or not a selection instruction has been issued from the screen operation unit  16  with respect to the thumbnail images displayed on the display unit  14  (step  15   c ). When a selection instruction has been issued with respect to the thumbnail images (Yes in step  15   c ), the controller  17  issues an instruction to read index data of the video data file indicated by the thumbnail image to the interface unit  18  (step  15   d ). Further, the controller  17  stores the read index data in the RAM  114  (step  15   e ), and terminates the processing. 
     When no selection instruction has been issued with respect to the thumbnail images in step  15   c , the controller  17  determines whether or not the cursor on the display unit  14  stops at an arbitrary thumbnail image for a predetermined period of time or longer (step  15   f ). When the cursor on the display unit  14  does not stop at an arbitrary thumbnail image for a predetermined period of time or longer (No in step  15   f ), the controller moves the processing to step  15   c.    
     When the cursor on the display unit  14  stops at an arbitrary thumbnail image for a predetermined period of time or longer (Yes in step  15   f ), the controller  17  issues an instruction to read index data of the video data file of the thumbnail image at which the cursor stops to the interface unit  18  (step  15   g ). Further, the controller  17  causes the RAM  114  to store the read index data therein (step  15   h ). 
     Subsequently, the controller  17  determines whether or not the cursor has moved from the thumbnail image (step  15   i ). When the cursor has moved from the thumbnail image (Yes in step  15   i ), the controller  17  erases the index data stored in the RAM  114  (step  15   j ), and moves the processing to step  15   c . When the cursor has not moved from the thumbnail image (No in step  15   i ), the controller  17  terminates the processing. 
     As a result of this, from among the plurality of video data files recorded on the storage medium  30 , the index data of the video data file desired to be reproduced is stored in the RAM  114 . 
     When a reproduction instruction of the video data file is issued, the controller  17  carries out the reproduction processing shown in  FIG. 7 . 
     As described above, if the plurality of video data files are recorded on the storage medium  30 , the video data processing apparatus  10  according to the third embodiment displays the thumbnail images of the individual video data files on the display unit  14 . Further, the user is made to refer to the displayed thumbnail images, and select a video data file which is an object of the reproduction processing. At this time, when the cursor stops at an arbitrary thumbnail image on the display unit  14  for a predetermined period of time or more, the controller  17  reads the index data of the video data file, and stores the index data in the RAM  114 . As a result of this, it is not necessary to read the index data items of all the video data files in the storage medium  30 , and the reading operation of the index data is carried out before the reproduction start instruction is issued, whereby it becomes possible to realize a reproduction operation excellent in response to a reproduction start operation. 
     Accordingly, it is possible for the video data processing apparatus according to the present invention to quickly start a reproduction operation of video data. 
     Other Embodiments 
     It should be noted that the present invention is not limited to the above-mentioned embodiments. For example, in each of the above embodiments, an example in which video data is reproduced from a video data file recorded on the removable storage medium  30  has been described. However, even a case where sound data is reproduced from a sound data file recorded on the storage medium  30  is also practicable. 
     In each of the above embodiments, an example in which the recording position of the video data is expressed by the data length from the leading head of the video data file has been described. However, the expression of the recording position of the video data is not limited to the above method. For example, even a case where the recording position of the video data is expressed by a data length of each frame of the video data is also practicable. However, it is necessary to pay attention to the fact that data lengths must be cumulatively added up in order to confirm the recording position of the video data. 
     In the above embodiment, an example in which the video data and control signal are transmitted by a bus has been described. However, even a case where the video data and control signal are separately transmitted by different buses is also practicable. 
     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.