Abstract:
An error correction apparatus comprises a buffer memory for successively storing ECC error correction blocks included in the reproducing signal read from the optical disk in units of a row including a corresponding inner code parity, and an error correction means for successively performing an error correction on the read row by reading the column of information data stored in a buffer memory and said inner code parity corresponding to the column from among the ECC error correction block and using the read inner code parity in parallel with processing for storing the remaining data forming the ECC error correction block at a timing before all of data constituting the ECC error correction block is stored in the buffer memory.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an error correction apparatus and an optical disk player using the same. 
     2. Description of the Related Art 
     In a digital versatile disk (DVD) player and the like, an analog signal read from the DVD is converted to a digital signal and the digital signal is subjected to an 8-16 conversion when reproducing a DVD. A single error correcting codes (ECC) block worth of digital signal obtained by the 8-16 conversion is stored in a buffer memory, an error correction is performed by reading the signal, and the error corrected digital signal is decoded. 
     The error correction is performed on the digital signal read from the DVD in units of the ECC. 
     FIG. 1 is a view for explaining the format of the ECC block. 
     Data B M,N  (0≦M≦191, 0≦N≦171) shown in FIG. 1 is information data composed of 16 sectors each having 172 bytes 12 rows. 
     Also, data B M,N  (0≦M≦207, 172≦N≦181) is an inner code parity of a Read-Solomon code. 
     Namely, the inner code parity (172≦N≦181) is an inner code parity of the information data B M,N  (0≦N≦171). 
     Also, the data B M,N  (192≦M≦207, 0≦N≦171) is an outer code parity of the Read-Solomon code. 
     Namely, the outer code parity B M,N  (192≦M≦207) is an outer code parity of the information data B M,N  (0≦M≦192). 
     Below, execution timing of processing for storing the ECC block worth of digital signal in the buffer memory and the processing for the error correction will be explained. 
     FIG. 2 is a view for explaining an execution timing of processing for storing one ECC block worth of the digital signal and an error correction. 
     In FIG. 2, the abscissa axis indicates time and the ordinates axis indicates a data amount. 
     As shown in FIG. 2, the one ECC block worth of digital signal is written in the buffer memory between the time “ 0 ” and “t 1 ”. Next, the one ECC block worth of digital signal written during the time between “ 0 ” and “t 1 ” is read and the error correction is performed between the time “t 1 ” and “t 2 ”. Also, the next one ECC block worth of the digital signal is written in the buffer memory during the time “t 1 ” and “t 2 ”. Next, the one ECC block worth of digital signal written in the buffer memory between the time “t 1 ” and “t 3 ” is read and the error correction is performed between the time “t 3 ” and “t 4 ”. 
     In this way, in the DVD player of the related art, one ECC block worth of digital signal is first stored in the buffer memory, and the error correction is performed by reading the digital signal from the buffer memory. Therefore, at least the time for “t 2 ” is required from the start of the writing to the buffer memory to the completion of the error correction. 
     Namely, the time from the start of writing the ECC block to the buffer memory to the completion of the error correction affects the access time or reproducing time of the DVD player. 
     Recently, there is a demand for a shorter accessing time or reproducing time of the DVD player, so it has been desired that the time from the start of writing the ECC block to the buffer memory to the completion of the error correction be shortened. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide an error correction apparatus and an optical disk reproducing apparatus which can shorten the access time of a DVD player by shortening the time from the start of writing the ECC block to a buffer memory to the completion of an error correction. 
     To attain the above object, the error correction apparatus of the present invention performs an error correction in units of an error correction code block composed of information data, an inner code parity indicating the error correction code for every row of the information data and an outer code parity indicating an error correction code for every column of the information data when a plurality of bit data forming the information data is arranged in matrix, and comprises: a memory means for storing the error correction code block included in a signal read from a memory medium by inputting the error correction code block as units of the row of the information data and the inner code parity corresponding to the row; and an error correction means for reading the row of the information data and the inner code parity corresponding to the row among the error correction code block stored in the memory means and performing an error correction of the read row of the information data by using the read inner code parity data at the timing before all of the data constituting the error correction code block has been stored in the memory means, in parallel with the operation of storing in the memory means the remaining data constituting the error correction code block. 
     In the error correction apparatus of the present invention, the error correction code block included in the reproducing signal read from the recording medium is successively stored in the memory means in units of a row including the corresponding inner code parity. 
     Then, in parallel with the storing processing, the row of the information data already stored in the memory means and the inner code parity corresponding to the row from among the error correction code block during being stored in the memory means are successively read, and an error correction of the read row is carried out by using the read inner code parity at the timing before all of the data constituting the error correction code block is stored in the memory means in the error correction means. 
     Preferably, in the error correction apparatus of the present invention, the error correction means terminates the operation of the error correction using the inner code parity on the error correction code block at the timing approximately matching to a timing when all of the data constituting the error correction code block data is stored in the memory means. 
     Preferably, in the error correction apparatus of the present invention, the error correction means starts the operation of the error correction at the timing after a first row of the information data and the inner code parity corresponding to the first row is stored in the memory means. 
     Preferably, in the optical disc reproduction apparatus of the present invention, the error correction means terminates the operation of the error correction using the inner code parity on the error correction code block at the timing approximately matching to a timing when all of the data constituting the error correction code block data is stored in the memory means. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects and features of the present invention will become clearer from the following description of the preferred embodiments given with reference to the accompanying drawings, in which: 
     FIG. 1 is a view for explaining the format of one ECC block worth of a digital signal read from a DVD; 
     FIG. 2 is a view for explaining an execution timing of processing for storing one ECC block worth of the digital signal and an error correction; 
     FIG. 3 is a view of the configuration of a DVD player according to an embodiment of the present invention; 
     FIG. 4 is a flow chart for explaining processing of an error correction apparatus and the buffer memory by control of the controller shown in FIG. 3; and 
     FIG. 5 is a view for explaining an execution timing of processing for storing one ECC block worth of the digital signal and an error correction in the DVD player shown in FIG.  3 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Below, a DVD player according to preferred embodiments of the present invention will be described with reference to the accompanying drawings. 
     FIG. 3 is a view of the configuration of a DVD player  1  of the present invention. 
     As shown in FIG. 3, the DVD player  1  comprises a spindle motor  10 , a forwarding motor  11 , a servo controller  12 , an optical pick-up  13  as a reading means, a wave shaping unit  14 , an analog/digital (AD) converter  15 , an 8-16 converter  16 , an error correction unit  17  as an error correction means, a buffer memory  18  as a memory means, a controller  19 , a stream divider  20 , a sub-picture decoder  21 , a moving picture experts group (MPEG) decoder  22  as a decoding means, an audio decoder  23 , a national television system committee (NTSC) encoder  24 , digital/analog (DA) converters  25  and  26 , a reference clock generator  27  and a video mixer  28 . 
     The servo controller  12  controls the position of an objective lens of the optical pick-up  13  as well as the spindle motor  10  and the forwarding motor  11 . 
     The spindle motor  10  drives the rotation of a DVD  2  based on a control from the servo controller  12 . 
     The forwarding motor  11  drives the movement of the optical pick-up  13  in the diameter direction of the DVD  2  based on a control from the servo controller  12 . 
     The optical pick-up  13  emits a laser light on the surface of the DVD  2  via an objective lens, receives the reflected light and outputs a reproducing signal in accordance with the results of the light reception to the wave shaping unit  14 . 
     The wave shaping unit  14  carries out a wave shaping of the reproducing signal from the optical pick-up  13  and outputs the same as a reproducing signal S 14  to the AD converter  15 . 
     The AD converter  15  converts the reproducing signal S 15  in an analog mode to a reproducing signal S 15  in a digital mode and outputs the same to the 8-16 converter  16 . 
     The 8-16 converter  16  generates a reproducing signal S 17  by converting an 8-bit pattern included in the reproducing signal S 15  to a 16-bit pattern and outputs the same to the error correction unit  17 . 
     The buffer memory  18  has a memory capacity for storing at least an ECC block worth of the reproducing signal S 16  as a single error correction code block from the 8-16 converter  16  based on a control from the controller  19 , and outputs the stored reproducing signal to the error correction unit  17 . 
     The error correction unit  17  performs an inner code error correction and an outer code error correction of the reproducing signal read from the buffer memory  18  in units of one block shown in FIG. 1, and outputs the reproducing signal S 17  after being subjected to the correction to the stream divider  20 . As error correction code, for example, a Reed Solomon code is used. 
     Processing in the error correction unit  17  and the buffer memory  18  will be explained in detail later on. 
     The reproducing signal S 17  is a data stream at the time of pre-mastering. 
     The stream divider  20  divides a sub-picture signal S 20   a , a video signal S 20   b  and an audio signal S 20   c  from the reproducing signal S 17  and outputs the same respectively to the sub-picture decoder  21 , the MPEG decoder  22  and the audio decoder  23 . 
     The sub-picture decoder  21  decodes the sub-picture signal S 20   a  and outputs the decoded sub-picture signal S 21  to the video mixer  28 . 
     The MPEG decoder  22  decodes the video signal S 20   b  in an MPEG format and outputs the decoded video signal S 22  to the video mixer  28 . 
     The audio decoder  23  decodes the audio signal S 20   c  and outputs the decoded audio signal S 23  to the DA converter  26 . 
     The DA converter  26  converts the audio signal S 23  in an analog mode to an audio signal S 26  in a digital mode and outputs the same to a speaker  31 . 
     The video mixer  28  combines the video signal S 22  and the sub-picture signal S 21  to generate a video signal S 28  and outputs the same to the NTSC encoder  24 . 
     The NTSC encoder  24  decodes the video signal S 28  in an NTSC format and outputs the decoded video signal S 24  to the DA converter  25 . 
     The DA converter  25  converts the video signal S 24  to a video signal S 25  in an analog mode and outputs the same to a display  30 . 
     Below, processing of the error correction unit  17  and the buffer memory  18  by a control of the controller  19  will be explained in detail. 
     FIG. 4 is a flow chart for explaining the processing of the error correction unit  17  and the buffer memory  18  by control from the controller  19 . 
     Step S 1 : The controller  19  shown in FIG. 3 controls the 8-16 converter  16  and the buffer memory  18  and starts writing one ECC block worth of reproducing signal S 16  from the 8-16 converter  16  to the buffer memory  18 . 
     The writing of the reproducing signal S 16  from the 8-16 converter  16  to the buffer memory  18  is carried out in units of the ECC block shown in FIG.  1 . First, data B 0,0  to B 0,181 , shown in FIG. 1 is written, then, data B 1.0  to B 1,181  is written. Subsequently, data B 2,0  to B 2,181 , data B 3,0  to B 3,181 , . . . , data B 11,0  to B 11,181 , data B 192,0  to B 192,181  is written. 
     Then, the writing operation is carried out in the same pattern to write data B 168,0  to B 168,181 , . . . B 179,0  to B 179,181 , B 206,0  to B 206,181 , B 180,0  to B 180,181 , . . . , B 191,0  to B 191,181 , data B 207,0  to B 207,181 , and the writing operation of one ECC block worth of data completes. 
     Here, one frame is composed of data BH M,0  to B M,171  and one sector is composed of 13 frames. Further, one ECC block is composed of 16 sectors. 
     Step S 2 : The controller  19  judges whether or not the “1/A” times of one ECC block worth of reproducing signal S 16  is written in the buffer memory  18 . When judged it is not written, the controller  19  repeats the judgement operation until it is judged to be written, then performs the processing in Step S 3 . 
     Here, as shown in FIG. 5, “A” is decided so that the correction of the inner code error will be finished at the timing when one ECC block worth of reproducing signal S 16  is finished to be written from the 8-16 converter  16  to the error correction unit  17 . Namely, at the time “t 10 ” shown in FIG. 5, the “1/A” times of one ECC block worth of the reproducing signal S 16  is written to the buffer memory  18 , and the error correction unit  17  starts the correction of the inner code error. 
     Step S 3 : When “1/A” times of one ECC block worth of reproducing signal S 16  is written to the buffer memory  18 , the controller  19  reads the reproducing signal from the buffer memory  18  to the error correction unit  17  in a written order in parallel with the writing processing, and performs a first correction of the inner codes error on the read reproducing signal. The result of the correction of the inner code error is written back to the buffer memory  18 . At this time, the correction of the inner code error is performed in units of a sector. 
     Specifically, the data B 0,0  to B 0,181  shown in FIG. 1 is read, then the data B 1,0  to B 1,181  is read. Then, one ECC block worth of data is read in an order of data B 2,0  to B 2,181 , data B 3,0  to B 3,181  . . . , data B 207,0  to B 207,181 , from the buffer memory  18  to the error correction unit  17  first 
     Step S 4 : The controller  19  judges whether or not the writing of one ECC block worth of reproducing signal S 16  to the buffer memory  18  is finished. When it is judged it is finished, the controller  19  stops the processing, while it is not, the controller  19  repeats the judgement. 
     Here, since the “A” in Step S 2  is defined as above, at the time “t 1 ” when the writing of one ECC block worth of reproducing signal S 16  to the buffer memory  18  is finished, the first correction of the inner code error by the error correction unit  17  is also finished, as shown in FIG.  5 . 
     Step S 5 : The controller  19  performs the correction of an outer code error by reading the result of the first correction of the inner code error from the buffer memory  18  to the error correction unit  17 , and writes back the result of correction of the outer code error to the buffer memory  18 . 
     At this time, the correction of the outer code error is performed for every column shown in FIG.  1 . Namely, the correction of the outer code error correction is performed in units of data B 0,M  to B 207,M . 
     Step S 6 : The controller  19  reads the result of the correction of the outer code error from the buffer memory  18  to the error correction unit  17  to perform a second error correction and outputs the result of the second correction to the stream divider  20  as a reproducing signal S 17 . 
     Next, the entire operation of the DVD player  1  will be explained with reference to FIG.  3 . 
     First, the DVD  2  rotates by the rotation drive from the spindle motor  10  based on the control of the servo controller  12 , and a reproducing signal is output from the optical pick-up  13  to the wave shaping unit  14 . The reproducing signal is subjected to a wave shaping in the wave shaping unit  14 , and the wave shaped reproducing signal S 14  is output to the AD converter  15 . 
     The reproducing signal S 14  is converted to a reproducing signal S 15  in a digital mode in the AD converter  15  and output as a reproducing signal S 15  to the 8-16 converter  16 . 
     The reproducing signal S 15  is subjected to the 8-16 conversion in the 8-16 converter  16 . Then, the converted reproducing signal S 16  is stored in the buffer memory  18  as explained above, and subjected to the error correction in the error correction unit  17  in the units of the ECC block. 
     Then, in the error correction unit  17 , the error corrected reproducing signal S 17  is output to the stream divider  20 , which divides the same into the sub-picture signal S 20   a , the video signal S 20   b  and the audio signal S 20   c  and outputs respectively to the sub-picture decoder  21 , the MPEG decoder  22  and the audio decoder  23 . 
     Next, the sub-picture signal S 20   a  is decoded in the sub-picture decoder  21  and the decoded sub-picture signal S 21  is output to the video mixer  28 . 
     The video signal S 20   b  is decoded in the MPEG decoder  22  and the decoded video signal S 22  is output to the video mixer  28 . 
     Also, the audio signal S 20   c  is decoded in the audio decoder  23  and the decoded audio signal S 23  is output to the DA converter  26 . 
     The sub-picture signal S 20   a  is combined with the video signal S 22  in the video mixer  28 , and the video signal S 28  as the combined result is output to the NTSC encoder  24 . 
     Then, the video signal S 28  is subjected to an NTSC decoding in the NTSC encoder  24 , and a video signal S 24  as the decoded result is output to the DA converter  25 . 
     The video signal S 24  is converted to a video signal S 25  in an analog mode in the DA converter  25  and the video signal S 25  is output to the display  30 . 
     Also, the audio signal S 23  is converted to an audio signal S 26  in an analog mode in the DA converter  26  and the audio signal S 26  is output to the speaker  31 . 
     As explained above, according to the DVD player of the present embodiment, as shown in FIG. 5, the first correction of the inner code error by the error correction unit  17  starts at the timing “t 10 ” which is the timing when the “1/A” times of one ECC block worth of the reproducing signal S 16  is written from the 8-16 converter  16  to the buffer memory  18 . Therefore, as shown in FIG. 5, the first correction of the inner code error can be finished at the timing of “t 1 ” when one ECC block worth of reproducing signal S 16  is written from the 8-16 converter  16  to the buffer memory  18 . Accordingly, comparing with the case of the related art shown in FIG. 2, the timing to finish the first correction of the inner code error can be shortened by the length of “t 2 ”. As a result, the access time, reproducing time, of the DVD player can be made shorter. 
     Note, for example, when a DRAM is used as a buffer memory  18 , an 8-page mode word accessing is performed and at a single-speed, the first correction of the inner code error starts at the time of finishing writing the “15 sectors plus 15 frames” worth of signals among the one ECC block from the 8-16 converter  16  to the buffer memory  18 . When at a double-speed, the first correction of the inner code error starts at the time of writing the “15 sectors plus 4 frames” worth of signals among the one ECC block from the 8-16 converter  16  to the buffer memory  18 . When at a triple-speed, the first correction of the inner code error starts at the time of writing the “14 sectors plus 194 frames” worth of signals among the one ECC block from the 8-16 converter  16  to the buffer memory  18 . 
     The present invention is not limited to the above embodiments. 
     For example, in the above embodiment, the correction of the inner code error started in the error correction unit  17  on the ECC block being written to the buffer memory  18  at the timing of “t 10 ” shown in FIG. 5, however, the starting timing is not limited as far as it is between “t 10 ” and “t 1 ” shown in FIG.  5 . 
     As explained above, according to the error correction apparatus of the present invention, the period of time from the start of writing the error correction code block to the memory means to the completion of the error correction can be made shorter. 
     Also, according to the optical disk reproducing apparatus of the present invention, the access time to the optical disk can be made shorter. 
     While the invention has been described with reference to specific embodiment chosen for purpose of illustration, it should be apparent that numerous modifications could be made thereto by those skilled in the art without departing from the basic concept and scope of the invention.