Patent Document

CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2007-305076, filed Nov. 26, 2007, the entire contents of which are incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to content data recording apparatus and method for recording content data such as audio and video data using a nonvolatile memory, for example. 
         [0004]    2. Description of the Related Art 
         [0005]    A content data recording apparatus such as digital camera and video camera acquires content data such as video and audio data, and then, records the content data in a storage unit. A flash memory has come to wide use because it has a large capacity and is obtained at a low price. 
         [0006]    The content data recording apparatus has the following problem. Specifically, when content data is recorded, a write error may occur. In this case, input data sequentially changes; for this reason, the content data when an error occurs is lost. In general, the content data recording apparatus performs the following operation to prevent data loss when an error occurs. Specifically, error detection is made when data is written to a flash memory. If an error is detected, the data is again written to the flash memory. 
         [0007]    However, even if the error is not detected in a write operation, there may be a case where data can not be read correctly in fact from the flash memory in a read operation due to a property of the flash memory. Considering the foregoing circumstances, a conventional content data recording apparatus needs to perform the following operation. Namely, the user recognizes recording data by making the chase reproduction during data recording or by reproducing the data after recorded, and thereafter, must detect an error. 
         [0008]    According to a conventional error detection method, if the same input signal is again obtained, rewrite is possible; therefore, the lost data can be compensated for. However, if the same Input signal is not again obtained, for example, rewrite is impossible during collection of information in news. Thus, it is impossible to compensate for the data loss. 
         [0009]    A method for effectively using of a memory area of the flash-type electrically erasable and programmable ROM (EEPROM) has been proposed (e.g., see Jpn. Pat. Appln. KOKAI publication No. H6-131895). In this proposal, error correction data required for error correction is written to a redundancy area of a flash-type EEPROM. 
       BRIEF SUMMARY OF THE INVENTION 
       [0010]    An object of the invention is to provide content data recording apparatus and method for securely detecting an error in a write operation to record content data. 
         [0011]    According to one aspect of the present invention, there is provided a content data recording apparatus comprising: a code addition unit adding an error correction code to an input content data; a data storing unit successively receiving the content data added with the error correction code, and temporarily storing the content data, and thereafter, outputting it; a plurality of nonvolatile memories that enable writing/reading of the content data; an address generator generating a write address when the content data successively output from the data storing unit is written to the nonvolatile memories and generating a read address when the content data is read from the nonvolatile memories; a read buffer temporarily storing the content data read from the nonvolatile memories, and outputting the read content data; an error correction unit correcting an error of the content data output from the read buffer based on the error correction code added to the content data, and giving correction impossible notification when the error is not corrected by the error correction code; and a controller carrying out a read control for reading content data from the nonvolatile memories when content data write to the nonvolatile memories is completed, and carrying out a first rewrite control for controlling the data storing unit so that the data storing unit again outputs content data when receiving the correction impossible notification from the error correction unit, and writing the content data again output to a new write address of the nonvolatile memories. 
         [0012]    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 
         [0013]    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. 
           [0014]      FIG. 1  is a block diagram showing the configuration of a content data recording apparatus according to a first embodiment of the present invention; 
           [0015]      FIG. 2  is a schematic view to explain the relationship between processing time of a storage unit and an error correction unit shown in  FIG. 1  and transfer time of content data; 
           [0016]      FIG. 3  is a flowchart to explain the rewrite procedure by a CPU of  FIG. 1 ; and 
           [0017]      FIG. 4  is a block diagram showing the configuration of a content data recording apparatus according to a second embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    Various embodiments of the present invention will be hereinafter described with reference to the accompanying drawings. 
       First Embodiment 
       [0019]      FIG. 1  is a block diagram showing the configuration of a content data recording apparatus according to a first embodiment of the present invention. In  FIG. 1 , input and output are independently shown to easily understand an operation inclusive of the case where a bus of this embodiment is a bidirectional bus. 
         [0020]    Content data is video and audio having a frame format. When recording is started, the content data is supplied to a write buffer  10 . The write buffer  10  temporarily holds the content data to take time matching with an error correction code addition unit  20 . The error correction code addition unit  20  adds an error correction code to the content data output from the buffer  10 . The content data added with the error correction code is distributed to two signals by a distributor  30 . One of two signals is supplied to a write buffer  40  while the other thereof is supplied to a write buffer  50 . 
         [0021]    The write buffer  40  has a capacity equivalent to two pages. The buffer  40  outputs content data equivalent to one page when the content data remains more than one page. 
         [0022]    The write buffer  50  has a capacity equivalent to two pages. The buffer  50  holds the same content data as the buffer  40 . When the capacity equivalent to two pages becomes full, both buffers  40  and  50  overwrite new data in the order from data held at first. The buffer  50  holds content data equivalent to one page therein according to hold instructions from a central processing unit (CPU)  60 , and then, inhibits an overwrite operation. When receiving output instructions from the CPU  60 , the buffer  50  outputs the held content data equivalent to one page. 
         [0023]    A switching unit  70  receives content data output from the buffers  40  and  50 , and selectively outputs one content data of the buffers  40  and  50  to a storage device  80 . Usually, the switching unit  70  outputs the content data from the buffer  40 . 
         [0024]    The storage device  80  includes a flash memory  81 , an address generator  82 , a state notification unit  83  and an error detector. The flash memory  81  can store content data written in units of pages. The address generator  82  generates write/read address in the flash memory  81 . The storage device  80  writes the output content data to the flash memory  81  according to a write address generated by the address generator  82 . 
         [0025]    When write to the flash memory  81  is started, the state notification unit  83  gives notification that the flash memory  81  is in a busy state to the CPU  60 . When write to the flash memory  81  is completed, the state notification unit  83  gives notification that the busy state ends to the CPU  60 . 
         [0026]    The error detector  84  detects an error in a write operation of content data to the flash memory  81 . When detecting a write error, the error detector  84  notifies the CPU  60  that the write error occurs. 
         [0027]    The content data written to the flash memory  81  is read according to instructions from the CPU  60 . A read buffer  90  temporarily holds the read content data to take time matching with an error correction unit  100 , and thereafter, outputs the read content data to the error correction unit  100 . 
         [0028]    The error correction unit  100  intactly passes the content data based on the error correction code added to the content data if no error occurs in a write operation. The error correction unit  100  corrects an error of the content data if an error occurs in a write operation. If the foregoing error is correctable by the error correction code, the error correction unit  100  outputs the corrected content data to a read buffer  110 . Conversely, if the error of the read content data is not correctable, the error correction unit  100  gives correction impossible notification to the CPU  60 . The content data output to the buffer  110  is temporarily held, and thereafter, output outside as reproduction data. 
         [0029]      FIG. 2  is a schematic view to explain the relationship between processing time of a storage device  80  and an error correction unit  100  according to a first embodiment of the present invention and processing time of processing continuously input content data every frame. In  FIG. 2 , the case where content data equivalent to one frame ranges a plurality of pages is given as one example. In order to realize the foregoing processing, a content data recording apparatus must be designed sufficiently considering write/read time to the flash memory  81  and error correction time in the error correction unit  100 . Specifically, the storage device  80  and the error correction unit  100  must be designed to satisfy the following condition so that time of rewriting content data having an error to the flash memory  81  is secured. According to the condition, the total time of write time, read time and error correction time of the content data is shortened more than time of processing content data equivalent to one page with respect to time of inputting one frame content data. The CPU  60  completes rewrite of the content data within a free time thus produced. 
         [0030]    The CPU  60  controls write/read of content data to the storage device  80  so that normal content data is stored in the storage device  80 .  FIG. 3  is a flowchart to explain the content data rewrite procedure by the CPU  60  according to the first embodiment of the present invention. 
         [0031]    The content data from the buffer  40  is supplied to the storage device  80 , and then, written to the flash memory  81  according to a write address generated by the address generator  82 . When write is started, the state notification unit  83  gives notification that the flash memory  81  is in a busy state to the CPU  60  (block B 1 ). The CPU  60  determines whether or not notification that the busy state ends is given when the flash memory  81  is in the busy state (block B 2 ). If the notification that the busy state ends is given (Yes in block B 2 ), the CPU  60  determines whether or not notification that a write error is detected is supplied from the error detector  84  (block B 3 ). If there exist no notification that the write error is detected (No in block B 3 ), the CPU  60  determines that write to the flash memory  81  ends safely. Then, the CPU  60  reads the written content data (block B 4 ). The CPU  60  determines whether or not correction impossible notification from the error correction unit  100  is given (block B 5 ). If the notification is not given (No in block B 5 ), the CPU  60  ends the procedure because the content data is normally stored in the storage device  80 . 
         [0032]    Conversely, if the correction impossible notification from the error correction unit  100  is given (Yes in block B 5 ), the CPU  60  outputs save command to the buffer  50 , and holds the write address of the content data (block B 6 ). In this way, the same content data as the content data output to the storage device  80  from the buffer  40  is stored in the buffer  50 . Then, the CPU  60  determines whether or not the one-frame content data procedure ends (block B 7 ). If the one-frame content data procedure ends (Yes in block B 7 ), the CPU  60  gives instructions to the address generator  82  to generate a new address different from the write address of the flash memory  81  having an error (block B 8 ). When the new address is generated, the CPU  60  controls the switching unit  70  so that the switching unit  70  outputs the content data from the buffer  50  (block B 9 ), and thus, gives output instructions to the buffer  50  (block B 1 ). The content data output from the buffer  50  is stored in the storage device  80 . The CPU  60  transfers the procedure to the block  82  to confirm whether or not the content data is normally stored in the storage device  80 . 
         [0033]    In block B 2 , if there exists notification that the busy state is completed is not given (No in block B 2 ), the CPU  60  determines whether or not a state that the notification is not given continues for a predetermined time (block B 11 ). If the notification is not given after the predetermined time elapses (Yes in block B 11 ), the CPU  60  transfers the procedure to block B 6 . If the predetermined time does not elapse (No in block  811 ), the CPU  60  transfers the procedure to block B 2 . 
         [0034]    In block B 3 , if a write error occurs (Yes in block B 3 ), the CPU  60  transfers the procedure to the block B 6 . 
         [0035]    In this case, the CPU  60  completes a series of procedures (from block B 8  to block B 10 ) of outputting the content data from the buffer  50  and writing it to the flash memory  81  within a free time shown in  FIG. 2 . If the rewrite procedure is not completed from the reason why a write error again occurs in the content data from the buffer  50 , the CPU  60  takes the foregoing series of procedures within a free time generated after the next frame ends. In this case, there is a possibility that the capacity of the buffer  50  is short; therefore, preferably, the buffer capacity has two pages or more. 
         [0036]    Although no illustration in  FIG. 3 , when the rewrite procedure of  FIG. 3  ends, the CPU  60  controls the switching unit  70  so that the switching unit  70  selects the content data from the buffer  40 . In other words, usually, the content data from the buffer  40  is output via the switching unit  70 , and in a rewrite operation only, the content data from the buffer  50  is output via the switching unit  70 . 
         [0037]    According to the foregoing first embodiment, if the predetermined time elapses in a state that the CPU  60  does not receive the notification that the busy state ends from the state notification unit  83 , the CPU  60  determines that write of content data fails. Then, the CPU  60  gives instructions to save the same content data as the write-failed content data to the buffer  50 . Further, the CPU  60  saves the write address of the write-failed content data together with the save instructions. The CPU  60  controls the address generator  82  so that the address generator  82  generates a write address different from the write address of the flash memory having an error. Then, the buffer  50  outputs the saved content data, and rewrites the content data to the flash memory based on a new write address. In this way, even if content data write to the flash memory  81  is not completed, the content data recording apparatus can rewrite the content data to the flash memory  81 , and therefore, can record the content data to the flash memory  81  normally. 
         [0038]    If write to the flash memory  81  is completed, and there exists notification that a write error is detected output from the error detector  84 , the CPU  60  determines that write of the content data fails. Then, the CPU  60  saves the write-failed content data in the buffer  50  to rewrite the content data to the flash memory  81 . In this way, even if an error occurs in a write operation to the flash memory  81 , the content data recording apparatus can rewrite the content data to the flash memory  81 , and therefore, can record the content data to the flash memory  81  normally. 
         [0039]    If write to the flash memory  81  is completed, and there exists no notification that a write error is detected, the CPU  60  reads the data at the same time as the write completion. The error correction unit  100  corrects the read content data based on an error correction code added to the data. If correction is impossible, the error correction unit  100  gives correction impossible notification to the CPU  60 . When receiving the correction impossible notification, the CPU  60  saves the content data that is impossible to correct in the buffer  50  to rewrite the content data to the flash memory  81 . In this way, even if write to the flash memory  81  is completed, and a write error is not detected, it is possible to automatically confirm whether or not the content data is normally written. If write to the flash memory  81  fails, the content data is rewritten to the flash memory  81 . Therefore, it is possible to compensate for content data loss. 
         [0040]    The CPU  60  executes rewrite of the write-failed content data within a free time between one-frame transfer time of the content data and processing time of one-frame content data. This serves to execute rewrite without hindering write of continuously input content data to the flash memory  81 . 
         [0041]    The flash memory is generally capable of erasing data in units of blocks. Thus, the new write address of the flash memory is generated based on the units of blocks when the error that is impossible to correct occurs. A method to manage a continuity of the content data is adopted in generation of the new write address. As this method does not relate to this invention, the procedure of the generation of the new write address is omitted. 
         [0042]    According to the present invention, the content data recording apparatus securely detects a write error without hindering normal write of content data to the flash memory, and records the content data. 
         [0043]    The present invention is not limited to the foregoing first embodiment. For example, the content data recording apparatus is provided with two write buffers, and each capacity of the buffers  40  and  50  is two pages. However, the number of write buffers is not limited to two, and the capacity is not limited to two pages. 
       Second Embodiment 
       [0044]      FIG. 4  is a block diagram showing the configuration of a content data recording apparatus according to a second embodiment of the present invention. The same reference numbers are used to designate the same portions as  FIG. 1 , and the overlapping explanation is omitted. 
         [0045]    Content data output from an error correction code addition unit  20  is temporarily held in a ring buffer  120 , and then, output to a storage device  80 . 
         [0046]    The ring buffer  120  has a capacity equivalent to  16  pages. The ring buffer  120  successively writes input content data from the header address to the final address. When the content data is written to the final address of ring buffer  120 , the ring buffer  120  writes new content data to its header-address. When content data equivalent to one page is collected, the ring buffer  120  outputs the content data equivalent to one page. 
         [0047]    When determining that an error requiring rewrite occurs, a CPU  60  stores an address on the ring buffer  120  of data to be rewritten. When the ring buffer  120  receives instructions to output rewrite data from the CPU  60 , the ring buffer  120  outputs the stored content data equivalent to one page. 
         [0048]    According to the foregoing second embodiment, if write to a flash memory  81  of the storage device  80  fails, the write filed content data stored in the ring buffer  120  is again output to the storage device  80 . Thereafter, the content data is rewritten to the flash memory  81 . In this way, even if the ring buffer  120  is used, it is possible to automatically determine whether or not content data is normally written. In addition, it is possible to compensate for the loss of the write-failed content data. 
         [0049]    Therefore, the content data recording apparatus according to the present invention securely detects a write error without hindering normal write of content data to the flash memory, and records the content data. 
         [0050]    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.

Technology Category: 3