Patent Publication Number: US-7916866-B2

Title: Apparatus for descrambling a data retrieved from an optical storage medium, and method therefor

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an apparatus for descrambling a data retrieved from an optical storage medium and a method therefor; more specifically, relates to an apparatus and method for descrambling a data retrieved from an optical storage medium by activating an linear feedback shift register (LFSR) according to address information that is stored in a memory. 
     2. Descriptions of the Related Art 
     To retrieve a data that is recorded on an optical storage medium, an optical access system is required. As shown in  FIG. 1 , an optical access system  1  of the prior art comprises a servo interface  101 , a decoder  103 , a memory  105 , a firmware  107 , and an interface  109 . The servo interface  101  receives a data  102  that is recorded on an optical storage medium, such as an optical disc, and transmits the data  102  to the decoder  103 . The decoder  103  generates a decoded data  104  by performing, for example, error correction and error detection code (EDC) calculation on the data  102 . The decoded data  104  is transmitted to the memory  105  to be temporarily stored. The interface  109  comprises a linear feedback shift register (LFSR) for descrambling the decoded data  104  to generate a digital data  106  which is recognizable for a host to be proceeded. The firmware  107  is configured to generate an initial value  108  to initialize the LFSR before the interface  109  descrambles the decoded data  104 . 
     For BDs (blu-ray discs), recorded data are arranged in clusters each of which comprises 32 data frames and protected by 2 kinds of error correction mechanism, long distance code (LDC) and burst indicator subcode (BIS). The LDC comprises (248, 216, 33) Reed-Solomon codewords, and is used to correct random errors and burst errors. The BIS comprises (62, 30, 33) Reed-Solomon codewords, and is used to indicate long burst errors. Each data frame comprises 2052-byte data and a 4-byte EDC. Both of the 2052-byte data and the EDC are descrambled by the LFSR. To initialize the LFSR, some shift registers of the LFSR are required to be preset with the initial value  108  derived from physical sector numbers associated with data frames. Besides, the initial value  108  should be used for all 32 data frames in the same cluster. 
     For HDDVDs, one data frame comprises 2048-byte data and a 4-byte EDC. Both of the 2048-byte data and the EDC are descrambled by the LFSR. Similarly, some shift registers of the LFSR are required to be preset with the initial value  108  when the LFSR is initialized. The same initial value  108  is used for 16 consecutive data frames. 
     The firmware  107  is required to be set before data descrambling and decoding begin. Once the data decoding is interrupted by, for example, reading a replacement for a defect from an optical storage medium, the firmware  107  must re-count to re-initialize the LFSR. This seriously influences the processing speed. Accordingly, a solution to avoid re-initializing the LFSR is desired in the industrial field. 
     SUMMARY OF THE INVENTION 
     One object of this invention is to provide an apparatus for descrambling a data retrieved from an optical storage medium. The apparatus comprises a decoder, a memory, and a descramble engine. The decoder decodes the data and generates address information corresponding to an address on the optical storage medium, wherein the address responds to a part of the data having been decoded. The memory stores the address information and the part of the data. The descramble engine continues descrambling the part of the data by retrieving the address information after the data decoding is interrupted. 
     Another object of this invention is to provide a system for processing a data retrieved from an optical storage medium. The system comprises a servo interface, a decoder, a memory, and an interface. The servo interface inputs the data. The decoder decodes the data and generates address information corresponding to an address on the optical storage medium, wherein the address responds to a part of the data having been decoded. The memory stores the address information and the part of the data. The interface comprises a descramble engine for continuing descrambling the part of the data by retrieving the address information after the data decoding is interrupted, and outputs the descrambled data. 
     Another object of this invention is to provide a method for descrambling a data retrieved from an optical storage medium. The method comprises the following steps: decoding the data; generating address information corresponding to an address on the optical storage medium; storing the address information and a part of the data having been decoded; and descrambling the part of the data continuously by retrieving the address information after the data decoding is interrupted. 
     After the data decoding is interrupted, the present invention may activate the LFSR in response to the address information that is stored in the memory. When the part of the data continues descrambling, the LFSR does not have to be re-initialized by a firmware. 
     The detailed technology and preferred embodiments implemented for the subject invention are described in the following paragraphs accompanying the appended drawings for people skilled in this field to well appreciate the features of the claimed invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of an optical access system of the prior art; 
         FIG. 2  is a block diagram of a first embodiment of the present invention; and 
         FIG. 3  is a flow chart of a second embodiment of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A first embodiment of the present invention is a system for processing a data retrieved from an optical storage medium, wherein the optical storage medium may be an optical disc such as a CD, VCD, DVD, HDDVD, BD or the like. As shown in  FIG. 2 , the system  2  comprises a servo interface  201  and an apparatus  209 . The apparatus  209  comprises a decoder  203 , a memory  205 , and an interface  207 . The servo interface  201  receives a data  202  from the optical storage medium and transmits it to the apparatus  209 . The decoder  203  receives and decodes a part of the data  202  to generate the data  204  having been corrected and address information  206  corresponding to an address on the optical storage medium. The address information  206  records relative physical position information of the decoded data  204  on the optical storage medium. That is, the address responds to the data  204 . This means that the address information  206  carries the information of part of the data  202  which have been corrected by the decoder  203 . The memory  205  stores the address information  206  and the data  204 . The interface  207  comprises a descramble engine  2071  for descrambling the data  204 . After the descrambling, the interface  207  outputs the descrambled data  208  to a host. 
     The descramble engine  2071  further comprises an LFSR (not shown). When the descrambling is interrupted because, for example, a replacement for a defect is required to be read from a position other than the current position of the optical storage medium, the descramble engine  2071  is temporarily terminated. After the interruption, the descramble engine  2071  continues descrambling, and the address information  206  is retrieved to activate the LFSR to continue descrambling the decoded data  204 . More specifically, the address information  206  provides information of the address on the optical storage medium before the decoding is finished. Therefore, the descrambling is able to continue by retrieving the address information  206  without re-initializing the LFSR from the beginning. Moreover, the firmware  108  in  FIG. 1  is unnecessary in the first embodiment of the present invention. 
     If the optical storage medium is a BD, the decoder  203  decodes the data  202  in unit of clusters. If the optical storage medium is an HD-DVD, the decoder  203  decodes the data  202  in unit of sectors. 
     A second embodiment of the present invention is a method for descrambling a data retrieved from an optical storage medium, wherein the optical storage medium may be an optical disc such as a CD, VCD, DVD, HDDVD, BD or the like. As shown in  FIG. 3 , the method comprises the following steps. In step  301 , a decoder, such as the decoder  203 , decodes the data retrieved from the optical storage medium. Then step  303  is executed in which the decoder generates address information corresponding to an address on the optical storage medium. In step  305 , a memory, such as the memory  205 , stores the address information and a part of the data having been decoded. In step  307 , a descramble engine, such as the descramble engine  2071 , descrambles the part of the data continuously by retrieving the address information after the data decoding is interrupted. In step  309 , an interface, such as the interface  207 , outputs the descrambled data. 
     The method further comprises a step of provides an LFSR. In particular, the LFSR is embedded in the descramble engine. Step  307  further comprises a step of activating the LFSR in response to the address information. 
     Similarly, if the optical storage medium is a BD, step  301  decodes the data in unit of clusters. If the optical storage medium is a HD-DVD, step  301  decodes the data in unit of sectors. 
     In addition to the steps shown in  FIG. 3 , the second embodiment is able to execute all of the operations or functions recited in the first embodiment. 
     After the descrambling is interrupted because, for example, a replacement for a defect is required to be read from the optical storage medium, step  307  is executed to continue the descrambling. At this moment, the address information is retrieved to activate the LFSR to continue descrambling. More specifically, the address information provides information of the address on the optical storage medium before which the decoding is finished. Therefore, step  307  is able to be executed without re-initialing the LFSR from the beginning. 
     Accordingly, the present invention may re-activate the LFSR in response to the address information that is stored in the memory. When the descrambling continues after the decoding is interrupted, the LFSR does not have to be re-initialized. The processing speed of the systems or apparatuses in accordance with the present invention will not be sacrificed due to the re-initialization of the LFSR. 
     The above disclosure is related to the detailed technical contents and inventive features thereof. People skilled in this field may proceed with a variety of modifications and replacements based on the disclosures and suggestions of the invention as described without departing from the characteristics thereof. Nevertheless, although such modifications and replacements are not fully disclosed in the above descriptions, they have substantially been covered in the following claims as appended.