Abstract:
Disclosed is a method for detecting synchronous information adapted to decode information recorded on a burst cutting area (BCA) on the surface of a recording medium, which method is capable of decoding the recorded information, based on only the detection of resync bytes recorded on the BCA and adapted to provide a synchronization for information recorded on the BCA following them, even when no sync byte recorded on the BCA to indicate the start point of the burst cutting area is detected. The method involves a resync byte detecting step for sequentially detecting the resync bytes following the sync byte when the sync byte is not detected, a detected information checking step for checking whether or not the resync bytes are sequentially detected in accordance with a predetermined order, and an information decoding step for reproducing and storing the information following the resync bytes when it is determined that the resync bytes are sequentially detected in accordance with the predetermined order, and decoding the stored information.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an optical disc drive system, and more particularly to a method for detecting synchronous information adapted to decode information recorded on a burst cutting area (BCA) on the surface of an optical disc. 
     2. Description of the Related Art 
     A BCA is an area arranged on the inner periphery of an optical disc, for example, a DVD (Digital Versatile Disc)-ROM disc. Such a BCA is formed on a disc using a laser cutting process in accordance with a manufacturer&#39;s option after the fabrication of the disc. Thus, the manufacturer can record, on the disc, desired information, for example, the serial number of the disc and anti-duplication information after the fabrication of the disc. 
     Typically, information including a sync byte and resync bytes are recorded on the BCA of a disc. The sync byte is adapted to indicate the start point of the BCA. Only one sync byte exists in the entire portion of the BCA. Each resync byte consists of a sync pattern and a sync code. When it is impossible to normally detect sync codes due to a defect involved in the sync byte, the start point of the BCA cannot be detected. In this case, the information recorded on the BCA cannot be decoded by an optical disk drive. 
     SUMMARY OF THE INVENTION 
     Therefore, an object of the invention is to provide a method for detecting synchronous information contained in resync bytes, where the synchronous information enables decoding of information recorded on a BCA on the surface of a recording medium, based solely on the detection of resync bytes recorded on the BCA, even when the sync byte is not detected. 
     In accordance with the present invention, this object is accomplished by providing a method for detecting sync information recorded on a burst cutting area of an optical disc, the burst cutting area being recorded with a sync byte that indicates the start point of the burst cutting area, and a plurality of resync bytes that provide synchronization for information recorded on the burst cutting area following the resync bytes, respectively, where each of the resync bytes consists of a sync pattern and a sync code. The information following the resync bytes is decoded based on the result of the detection of the sync information contained in the resync bytes, the method comprising: a resync byte detecting step for sequentially detecting the resync bytes following the sync byte when the sync byte is not detected; a detected information checking step for checking whether or not the resync bytes are sequentially detected in accordance with a predetermined order; and an information decoding step for reproducing and storing the information following the resync bytes when it is determined that the resync bytes are sequentially detected in accordance with the predetermined order, and decoding the stored information. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing and other objects, features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which: 
     FIG. 1 is a block diagram illustrating a DVD-ROM drive to which the present invention is applied; 
     FIGS. 2A-2B illustrate the recorded information state of a BCA on the inner periphery of a DVD-ROM disc; and 
     FIG. 3 is a flow chart illustrating a method for detecting sync information in accordance with an embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Reference will now be made in greater detail to the preferred embodiments of the present invention. 
     FIG. 1 is a block diagram illustrating a DVD-ROM drive to which the present invention is applied. Referring to FIG. 1, information recorded on the surface of an optical disc  10  is reproduced by an optical pickup  14 . The optical pickup  14  optically picks up the information recorded on a data recording surface of the optical disc  10  rotating in accordance with a drive force from the spindle motor  12  and then converts the picked-up information into an electrical signal, namely, an RF signal. The RF signal from the optical pickup  14  is applied to an RF amplifier unit  20 . The optical pickup  14  moves radially between the inner and outer peripheries of the surface of the optical disc  10  in accordance with a drive force from a feeding motor  26 . The RF amplifier unit  20  amplifies the RF signal from the optical pickup  14 , and removes noise and distortion from the amplified signal through a waveform equalization circuit, thereby outputting a shaped RF signal. The shaped RF signal from the RF amplifier unit  20  is applied to a data processor  30 . The RF amplifier unit  20  also sends signals for focus and tracking servos, that is, a focus error signal FE and a tracking error signal TE, to a servo signal processing unit  22 . The servo signal processing unit  22  applies control signals to a servo drive unit  24  for controlling a focus servo and a tracking servo, based on the focus error signal FE and tracking error signal TE, respectively. The servo drive unit  24  generates the drive voltages required to move the optical pickup  14 , as well as to drive the tracking and focus servos, and applies the respective drive voltages to the optical pickup  14  and feeding motor  26 , where the servos are located. 
     The data processor  30  decodes the RF signal received from the RF amplifier unit  20  and conducts an error correction for the resultant decoded data. The resultant signal from the data processor  30  is then applied to an interface unit  34 . The data processor  30  also outputs a drive control signal to a spindle motor drive unit  28 . Based on the drive control signal from the data processor  30 , the spindle motor drive unit  28  drives the spindle motor  12 . That is, the data processor  30  preferably includes a PLL circuit, an error correction circuit (ECC), a synchronization detecting unit, and data decoder in order to conduct its intrinsic operations as mentioned above. 
     The interface unit  34  interfaces a variety of control signals between the DVD-ROM drive and a host computer such as a personal computer. The interface unit  34  also outputs data received from the data processor  30  to the host computer. DRAMs  32  and  36  are used as an error correction memory for the data processor  30  and a transfer data buffer memory for the interface unit  34 , respectively. 
     A microcomputer  40  is coupled to both the data processor  30  and interface unit  34 . The microcomputer  40  is coupled to a memory  42 , which has a ROM stored with control programs adapted to execute a variety of operations, and a RAM for temporarily storing a variety of data generated during those operations, in order to control the entire operation of the drive. Coupled to the microcomputer  40  are a display unit  52  for displaying the operation state of the drive and a key button unit  50  for inputting operation commands. 
     FIGS. 2A and 2B illustrate tables of the recorded information state of the BCA on the inner periphery of the DVD-ROM disc  10 . FIG. 3 is a flow chart illustrating a method for detecting sync information in accordance with an embodiment of the present invention. 
     Recorded on the BCA are a sync byte, resync bytes, and a variety of information. In FIGS. 2A and 2B, the sync byte is denoted by SCBCA whereas each resync byte is denoted by RSBCA. FIG. 2A illustrates the configuration of the BCA. As shown, each piece of information recorded on the BCA is denoted by I, and C denotes an ECC parity. In FIG. 2B, data structures of the sync byte and resync bytes, each of which consists of a fixed sync pattern and a sync code, are illustrated. In FIG.  2 A, the BCA has blocks each consisting of 16 information bytes designated as I. The BCA may have a maximum of 13 blocks. Each block of the BCA includes sub-blocks each containing 4 bytes of information. Every sub-block follows a resync byte. Accordingly, one information block consists of 4 resync bytes and 16 information bytes. 
     The sync byte is the first sync information indicative of the start position of the BCA. Accordingly, only one sync byte exists in the BCA. On the other hand, the resync byte is the second sync information adapted to provide a synchronization for 4 information bytes, for example, I 0 , I 1 , I 2 , and I 3 . As shown in FIG. 2B, such a resync byte consists of a fixed sync pattern having a size of 8 channel bits and a sync code having a size of 4 data bits. The fixed sync pattern is a particular pattern which is configured not to be detected from the general information area, but to be detected only from the sync and resync area. The sync code of each resync byte is a serial number allocated to an associated information block and adapted to distinguish the information block from other information blocks. 
     Now, the sync information detecting method, which is carried out in the data processor  30  of FIG. 1, will be described in detail in conjunction with FIG.  3 . 
     In response to a start command from the microcomputer  40  for an operation of decoding information recorded on the BCA, the data processor  30  generates a clock in sync with a reproduced signal in order to detect information from the reproduced signal. Based on the generated clock, the data processor  30  detects the start position of the BCA in accordance with the following sync information detecting method. First, the data processor  30  monitors the reproduced signal at step  60  in order to check whether or not a fixed sync pattern is detected. When it is determined at step  60  that a fixed sync pattern is detected, the control procedure carried out by the data processor  30  proceeds to step  62 . At step  62 , it is determined whether or not a sync code detected following the detected sync pattern has a value of 0. Where the detected sync code has a value of 0, the detected sync pattern is that of the first sync information, namely, the sync byte. On the other hand, where the detected sync code has not a value of 0, the detected sync pattern is that of the second sync information, namely, the resync byte. Accordingly, when it is determined at step  62  that the detected sync code has a value of 0, the data processor  30  sequentially executes steps  64  and  66  in order to perform again a detection for a fixed sync pattern and a sync code following the fixed sync pattern. Where a fixed sync pattern is detected at step  64 , and the sync code detected following the detected sync pattern at step  66  has a value of 1, the control procedure proceeds to step  84  in order to execute a general BCA information decoding operation because the detected sync pattern is that of a second sync information just following the first sync information. Here, the general BCA information means information I following the detected second sync information. Also, the general BCA information decoding operation means an operation for detecting and decoding successive second sync information and BCA information following the sync code having a value of 1. 
     Where no sync pattern is detected at step  64  or where the value of the detected sync code is not 1, the control procedure proceeds to step  68 . At step  68 , it is checked whether or not a predetermined period of time has elapsed. Where a predetermined period of time has elapsed, the control procedure is ended. If not, the control procedure returns to step  60 . The reason why the control procedure is completed when a predetermined period of time has elapsed is to switch the operation mode of the data processor  30  to a standby mode unless a sync information is detected within the predetermined period of time. This is because the sync information detecting method according to the illustrated embodiment of the present invention is adapted to be executed in the procedure for initializing the drive. 
     Now, a procedure carried out when no first sync information is detected will be described. Even when no first sync information is detected, second sync information may be detected. Where it is determined at step  60  that a fixed sync pattern is detected, and at step  70  that the sync code detected following the detected sync pattern has a value of 1, the control procedure carried out by the data processor  30  proceeds to step  72 . At step  72 , Sync_C is set to 0. The Sync_C represents the number of detected sync codes. The reason why the number of detected sync codes is to be counted is to check whether not all second sync information of each information block consisting of 4 items of second sync information, namely, 4 resync bytes, are completely detected. An incomplete detection of the successive second sync information of the information block may result in a loss of information. When the information detection for an information block is achieved from the second, third, or fourth resync byte of the information block, 4, 8 or 12 bytes may be lost, respectively. 
     After setting the number of detected sync codes, Sync_C, to 0, as mentioned above, the control procedure of the data processor  30  proceeds to step  74 . At step  74 , the data processor  30  decodes BCA information following the detected resync byte and stores the decoded information. Thereafter, the control procedure proceeds to step  76 . At step  76 , the data processor  30  checks whether or not another sync pattern is detected. Where it is determined at step  76  that another sync pattern is detected, it is then checked at step  78  whether or not the sync code detected following the detected sync pattern has a value of 1. When it is determined at step  78  that the detected sync code has a value of 1, at step  80 , the number of detected sync codes is incremented by one. Thereafter, the control procedure proceeds to step  82 . At step  82 , it is checked whether or not the number of detected sync codes, Sync_C, is more than 3. Where the number of detected sync codes, Sync_C, is not more than 3, the data processor  30  repeatedly executes steps  74  to  82  until the number of detected sync codes, Sync_C is more than 3. Subsequently, the control procedure of the data processor  30  proceeds to step  84 . At step  84 , the general BCA information decoding operation for the block associated with the detected sync codes is executed. Thus, the decoding operation for one block containing 4 second sync information is completed. 
     Although not shown, the data processor  30  then repeatedly executes steps  60  to  84  until the decoding operation for BCA information of all blocks is completed. 
     Therefore, in accordance with the present invention, decoding of BCA information can be achieved, based only on the detection of the second sync information, even when no first sync information indicating the start position of the BCA is detected. 
     As apparent from the above description, the present invention provides an advantage in that information recorded on a BCA on the surface of a recording medium can be decoded, based on only the detection of resync bytes recorded on the BCA, even when a sync byte recorded on the BCA is not detected due to a defect involved in the sync byte. 
     While this invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiment, but, on the contrary, it is intended to cover various modifications within the spirit and scope of the appended claims.