Abstract:
The present invention discloses a method for sampling optic disc data. The method includes the following steps. First, a first sync tag signal and a data signal are provided, and the previous first sync tag signal is saved as a second sync tag signal. Then, it is checked and determined whether the value of the first sync tag signal and the second sync tag signal is true or false so as to divide the data signal. Since the neighboring sync tag signals are detected simultaneously, and the timing for sampling the data in the frame is determined according to whether the two contiguous sync tag signals are true or false, the present invention can improve the disadvantages of the prior art.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims the priority benefit of Taiwan application serial no. 93110814, filed on Apr. 19, 2004. All disclosure of the Taiwan application is incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a method for reading optic disc data, and more particularly, to a method for sampling optic disc data.  
         [0004]     2. Description of the Related Art  
         [0005]     Among different types of storage media, the optic disc is commonly used in various fields due to its characteristic of high capacity, low cost, and convenience in carrying. It is applied in storing data, listening music, and watching movies. In order to adapt to the characteristic of optic disc and to increase the reliability of the optic disc data reading, during the data is being stored into the optic disc, the current burning status in optic disc is changed when the data value is 1, and the current burning status in optic disc is not changed when the data value is 0.  
         [0006]     During the data is being stored into the optic disc, an eight to fourteen modulation (EFM) process and a Reed-Soloman code modulation process are performed on the data, and the sequence of data storing is interleaved messed up. The so-called EFM process means converting an 8 bits data into a 14 bits data in Compact Disk (CD) and converting an 8 bits data into a 16 bits data in Digital Versatile Disc (DVD), and the EFM processed data is stored into the optic disc.  
         [0007]     In order to read data from the optic disc, it is required to sense the laser light reflected by the optic disc for obtaining a radio frequency data (RF DATA) first, and then based on the RF DATA to generate a digital data signal DSEFM and a clock signal EFMCLK. The EFM data decoding are applied further onto these two data signals so as to perform a subsequent optic disc decoding process.  
         [0008]     Since the optic disc provides a high density for data storage, and the reading speed of the current optic disc drive is higher now, many techniques for improving the reading reliability (e.g. EFM technique mentioned above) have to be involved in order to accurately read the content of the optic disc. In addition, for every a predetermined length of the data stored in the optic disc, a sync pattern is inserted into the data for accurately reading the optic disc data. The session of the stored data with a predetermined length plus the sync pattern mentioned above is referred as a frame.  
         [0009]     However, the data read from the optic disc is a serial signal. In order to accurately read the serial signal, it is required to divide the serial signal based on an accurate clock signal. If the timing of dividing the serial signal is not correct, the data signal DSEFM obtained is missed read. In the prior art, a timing for detecting a sync pattern is used as a base for dividing data, and a counter is used to issue a data sampling tag signal when the clock signal EFMCLK counted by the counter reaches the length of the EFM data unit. As a result, the next stage circuit can accurately sample the data signal DSEFM according to the timing of the data sampling tag signal.  
         [0010]      FIG. 1A  is a schematic block diagram of a conventional optic disc data sampling apparatus.  FIG. 1B  is a timing diagram of the signals shown in the circuitry of  FIG. 1A . Referring to both  FIG. 1A and 1B , a sync detection circuitry  110  receives a clock signal EFMCLK and a data signal DSEFM, and detects a sync pattern “sync” from the data signal DSEFM based on the clock signal EFMCLK. Once the sync detection circuitry  110  detects the sync pattern “sync”, a sync tag signal “SyncTag” is issued. A counter  120  counts the number based on a timing (e.g. a timing of the clock signal EFMCLK) and generates a counting result “cnt”. The counter  120  resets the counting result “cnt” based on the sync tag signal “SyncTag” or a reset signal “reset” and recounts the number again. A comparator  130  receives the counting result “cnt” and compares it with a predetermined value “n”. Once the counting result “cnt” is accumulated to the predetermined value “n” , the comparator  130  issues a data sampling tag signal “DataTag” and the reset signal “reset”.  
         [0011]      FIG. 1B  schematically illustrates the relationship among the signals mentioned above. Under a normal situation, the counter  120  of the conventional optic disc data sampling apparatus automatically counts the number and regularly generates a data sampling tag signal “DataTag_N” (i.e. the data sampling tag signal “DataTag” shown in  FIG. 1A ). Ideally, the timing spacing of two neighboring data sampling tag signals “DataTag_N” should match to the timing of a single record data in the data signal DSEFM. However, errors occur in the timing of the physical data sampling tag signal “DataTag_N”, and the errors may be a lead or a lag error. As the reading data “Data” is increasing, the timing error of the data sampling tag signal “DataTag_N” gradually accumulates, which causes an error on the result of the dividing and sampling of the data signal DSEFM. The data sampling tag signal “DataTag_N” shown in the diagram is an example of a timing lag for explaining the error mentioned above, for example, the signal after the signal “An” is mildly lagged. In order to solve this problem, the prior art uses a sync tag signal “SyncTag” to control the counter  120  for recounting, thus the timing of the data sampling tag signal “DataTag_N” has to be tuned at the right timing. For example, the signal “Bn” shown in the diagram is a signal tuned by the signal “STb” to the right timing.  
         [0012]     However, it is well known that the optic disc which is a round plate make of a plastic material is easily scratched. When reading a defective area caused by a scratch or other reason, the sync pattern “sync” cannot be normally detected (i.e. it is not possible to generate the sync tag signal “SyncTag” at the right timing based on the assumption of the sync tag signal “STb” is has not happened). In the prior art, during the reading of the defective area, the sync tag signal “SyncTag” generated by the previous good data area (e.g. the sync tag signal “STa” as shown in the diagram) is used as a base timing to control the counter to continuously count the number, and to continuously generate a data sampling tag signal “DataTag_W” accordingly until next sync tag signal “SyncTag” is appeared (e.g. the sync tag signal “STc” as shown in the diagram). After comparing the data sampling tag signal “DataTag_N” generated under a normal situation with the data sampling tag signal “DataTag_W” which is not accurately tuned in time, it is known that the timing error of the signal “Bw” is continuously accumulated due to the fact that the signal “STb” does not appeared in time. Finally, the signal “Cw” cannot accurately divide the data “Data” (originally, the signal “Cw” should have the same timing as the signal “Cn” has).  
         [0013]     In summary, in the prior art, when sampling the data read from the optic disc, the clocks are counted for providing a data sampling tag signal “DataTag” at a right time, and the sync tag signal “SyncTag” is used to correct the timing of the data sampling tag signal “DataTag” in time. When reading the defective area caused by a scratch or other reason, usually it is not possible to generate the sync tag signal “SyncTag” at the right time. In such a case, the prior art uses a sync tag signal “SyncTag” generated by the previous good data area as its base timing to control the counter to continuously count the number, and to continuously generate the data sampling tag signal “DataTag” accordingly until next sync tag signal “SyncTag” appears.  
       SUMMARY OF THE INVENTION  
       [0014]     In order to avoid the disadvantages in the prior art, the present invention provides a method for sampling optic disc data. The method can accurately sample the data read from the optic disc&#39;s defective area caused by a scratch or other reason. As a result, the accuracy and the reliability of data reading from an optic disc are improved.  
         [0015]     The present invention further provides an optic disc data sampling apparatus. Based on the same reason mentioned above, the apparatus can accurately sample the data read from the optic disc&#39;s defective area caused by a scratch or other reason and not be impacted by the missing of the sync tag signal. As a result, the accuracy and the reliability of data reading from optic disc are improved.  
         [0016]     The present invention provides a method for sampling optic disc data, and the method includes the following steps. First, a first sync tag signal and a data signal are provided, and the previous first sync tag signal is saved as a second sync tag signal. Thereafter, it is checked and determined whether the value of the first sync tag signal and the second sync tag signal is true or false. Finally, the data signal is divided according to the determining result of whether the value of the first sync tag signal and the second sync tag signal is true or false. In accordance with the preferred embodiment of the present invention, wherein the step of dividing the data signal according to the determining result of whether the value of the first sync tag signal and the second sync tag signal is true or false further includes: if only the first sync tag signal is true, using a timing of the first sync tag signal as a base to backwardly divide the data signal in accordance with the data length unit; and if only the second sync tag signal is true, using a timing of the second sync tag signal as a base to forwardly divide the data signal in accordance with the data length unit. The so-called “backwardly” means the timing is counted from the base back to a past time, and the so-called “forwardly” means the timing is counted from the base to a future time.  
         [0017]     In addition, in accordance with an embodiment of the present invention, the step of dividing the data signal according to the determining result of whether the value of the first sync tag signal and the second sync tag signal is true or false further includes a step, which is optionally selected from following three steps. If both the first sync tag signal and the second sync tag signal are true, respectively using a timing of the first sync tag signal and a timing of the second sync tag signal as its base to simultaneously backwardly and forwardly divide the data signal in accordance with the data length unit. If both the first sync tag signal and the second sync tag signal are true, using a timing of the first sync tag signal as its base to backwardly divide the data signal in accordance with the data length unit. If both the first sync tag signal and the second sync tag signal are true, using a timing of the second sync tag signal as its base to forwardly divide the data signal in accordance with the data length unit.  
         [0018]     The present invention provides an optic disc data sampling apparatus in accordance with the method mentioned above. The sampling apparatus comprises a sync detection circuitry, a latch, a sample tag generating circuitry, and a memory. The sync detection circuitry receives a clock signal and a data signal, and generates a first sync tag signal by using the clock signal to detect the data signal. An input terminal of the latch receives the first sync tag signal, and an output terminal of the latch outputs a second sync tag signal. The sample tag generating circuitry receives the first sync tag signal and the second sync tag signal, and generates a data sampling tag signal based on the result of whether these two signals are true or false. The memory stores the data signal, and the optic disc sampling apparatus outputs the data signal in accordance with the timing of the data sampling tag signal from the memory.  
         [0019]     In accordance with the optic disc sampling apparatus of an embodiment according to the present invention, the capacity of the memory mentioned above must at least big enough to store an entire frame of data. In addition, the sample tag generating circuitry mentioned above may be implemented in accordance with the embodiment of the present invention and includes a counting-start position detection circuitry, a counter, and a comparator. The counting-start position detection circuitry determines a timing for starting to sample the data signal according to the result of whether the first sync tag signal and the second sync tag signal are true or false, and provides a third sync tag signal according to the sampling-start timing. The counter accumulates a counting value started from an initial value based on a predetermined timing, and obtains and outputs the counting value, wherein, the counter resets the counting value to the initial value according to the reset signal or the third sync tag signal. The comparator receives the counting value and compares it with a predetermined value. When the counting value reaches the predetermined value, the reset signal and the data sampling tag signal are propagated. The principle for determining the sampling-start timing by the counting-start detection circuitry is the principle for determining whether the first and the second sync tag signals are true or false as mentioned above.  
         [0020]     Since the neighboring sync tag signals are detected simultaneously, and the timing for sampling the data in the frame is determined according to the true-false relation of two contiguous sync tag signals, the present invention can avoid the disadvantages of the prior art.  
         [0021]     One or part or all of these and other features and advantages of the present invention will become readily apparent to those skilled in this art from the following description wherein there is shown and described a preferred embodiment of this invention, simply by way of illustration of one of the modes best suited to carry out the invention. As it will be realized, the invention is capable of different embodiments, and its several details are capable of modifications in various, obvious aspects all without departing from the invention. Accordingly, the drawings and descriptions will be regarded as illustrative in nature and not as restrictive. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]     The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention, and together with the description, serve to explain the principles of the invention.  
         [0023]      FIG. 1A  is a schematic block diagram of a conventional optic disc data sampling apparatus.  
         [0024]      FIG. 1B  is a timing diagram of the signals shown in the circuitry of  FIG. 1A .  
         [0025]      FIG. 2  is a flow chart illustrating a method for sampling optic disc data according to an embodiment of the present invention.  
         [0026]      FIG. 3  is a timing diagram of the signals for sampling optic disc data according to an embodiment of the present invention.  
         [0027]      FIG. 4  is a schematic block diagram of an optic disc data sampling apparatus according to an embodiment of the present invention.  
         [0028]      FIG. 5  is a signal timing diagram of the optic disc sampling apparatus shown in  FIG. 4 . 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0029]     To facilitate the explanation of the present invention and each embodiment, the so-called “backwardly” refers to the timing is counted from a certain base to a past time, and the so-called “forwardly” refers the timing is counted from a certain base to a future time hereinafter.  
         [0030]      FIG. 2  is a flow chart illustrating a method for sampling optic disc data according to an embodiment of the present invention. Referring to  FIG. 2 , a sync tag signal “SyncTagO” appeared in the previous time is saved in step S 21 . Then both the sync tag signal “SyncTag” and the data signal “DSEFM” most recently appeared are received in step S 22 , wherein, the sync tag signal “SyncTagO” and the sync tag signal “SyncTag” are two signals appeared contiguously. The sync tag signal “SyncTagO” and the sync tag signal “SyncTag” are further detected in step S 23 , and step S 24  is performed after the detection is completed. The true-false relation of these two signals mentioned above is determined in step S 24 , and if only the sync tag signal “SyncTagO” is true, step S 25  is performed. If it is determined in step S 24  that only the sync tag signal ”SyncTag” is true, step S 26  is performed. If the comparison result indicates that both SyncTag and SyncTagO signals are true, step S 27  is performed. However, it will be apparent to one of the ordinary skill in the art that if both the sync tag signal “SyncTag” and the sync tag signal “SyncTagO” are true, besides performing step S 27 , either step S 25  or step S 26  is optionally performed, and the result of the implementation is within the scope of the present invention.  
         [0031]     The data signal “DSEFM” is forwardly divided in accordance with the unit of the optic disc data length (e.g. 16 bits) by using the sync tag signal “SyncTagO” as a base in step S 25 . The data signal “DSEFM” is backwardly divided in accordance with the unit of the optic disc data length by using the sync tag signal “SyncTag” as a base in step S 26 . The implementation of this step can eliminate the disadvantage of the prior art. Finally, the data signal “DSEFM” is backwardly and forwardly divided in accordance with the unit of the optic disc data length simultaneously by using the sync tag signal “SyncTag” and the sync tag signal “SyncTagO” as its base respectively in step S 27 .  
         [0032]     In order to explain the method of dividing data as shown in steps S 25 ˜S 27  of the present embodiment in greater details, a signal timing diagram is exemplified hereinafter for explanation.  FIG. 3  is a timing diagram of the signals for sampling optic disc data according to a preferred embodiment of the present invention. Referring to  FIG. 3 , the timing direction is from left to right. The data signal “DSEFM” comprises data “DATA” and a sync pattern “sync”, wherein both “DATA” and “sync” jointly constitute a frame “frame”. The sync tag signals (e.g. SyncTagO and SyncTag as shown in the diagram) are obtained from detecting the sync pattern “sync”. If the sync tag signal “SyncTagO” is true and the sync tag signal “SyncTag” is false, a data sampling tag signal “DataTag” is generated by using the sync tag signal “SyncTagO” as a base, along the forward direction A for a time distance in accordance with the time length of a data length unit  310  (e.g. 16 bits). Therefore, the data signal “DSEFM” can determine a data dividing point according to the data sampling tag signal “DataTag”. If the sync tag signal “SyncTagO” is false and the sync tag signal “SyncTag” is true, a data sampling tag signal “DataTag” is generated by using the sync tag signal “SyncTag” as a base, along the backward direction B for a time distance in accordance with the time length of a data length unit  310 . Therefore, the data signal “DSEFM” can determine a data dividing point according to the data sampling tag signal “DataTag”.  
         [0033]     If both the sync tag signal “SyncTagO” and the sync tag signal “SyncTag” are true, a data sampling tag signal “DataTag” is generated by using the sync tag signal “SyncTagO” as a base along the forward direction A for a time distance in accordance with the time length of a data length unit  310 , and a data sampling tag signal “DataTag” is generated by using the sync tag signal “SyncTag” as a base along the backward direction B for a time distance in accordance with the time length of a data length unit  310 . Therefore, the data signal “DSEFM” can determine a data dividing point according to the data sampling tag signal “DataTag”. If both the sync tag signal “SyncTagO” and the sync tag signal “SyncTag” are false, in the present embodiment, a position from a base point, which is a base point in the case where both signals are not false mentioned above, backwardly moving a space of a frame is used as a base point for dividing data. Alternatively, a position where each frame should appear under the condition of not modifying with the sync tag signal can be used as the base point position.  
         [0034]     The data sampling tag signal “DataTag” mentioned above is exemplified for explaining the auxiliary signal for dividing data and should not be not used to limit the application scope of the present invention.  
         [0035]     In summary of the method for sampling optic disc data mentioned above, the present invention further provides an optic disc data sampling apparatus. A preferred embodiment is exemplified for explaining the present invention hereinafter.  FIG. 4  is a schematic block diagram of an optic disc data sampling apparatus according to a preferred embodiment of the present invention. Referring to  FIG. 4 , a sync detection circuitry  410  receives a data signal “DSEFM” and a clock signal “EFMCLK” from a previous stage circuitry, and generates a sync tag signal “SyncTag” according to a sync pattern in the timing detection data signal “DSEFM” of the clock signal “EFMCLK”. A latch  420  maintains the sync tag signal “SyncTag” for a while and outputs it as a sync tag signal “SyncTagO” at the timing of next frame appears. The sync tag signal “SyncTagO” and the sync tag signal “SyncTag” are two sync tag signals appeared contiguously. A memory  440  stores the data signal “DSEFM” and generates a data signal “DSEFMO” under the control of the optic disc data sampling apparatus. The data signal “DSEFMO” and the data signal “DSEFM” are, for example, the data signals of two neighboring frames in the present embodiment. The capacity of the memory  440  in the present invention is, for example, the size of one frame&#39;s data signal “DSEFM”. A sample tag generating circuitry  430  receives the sync tag signal “SyncTag” and the sync tag signal “SyncTagO”, and generates a data sampling tag signal “DataTag” according to the result of whether these two signals are true of false.  
         [0036]     The sample tag generating circuitry  430  mentioned above may be implemented by referring to the present embodiment and includes a counting-start position detection circuitry  431 , a counter  432 , and a comparator  433 . The counting-start position detection circuitry  431  receives both the sync tag signal “SyncTagO” and the sync tag signal “SyncTag”, determines a sampling-start timing by detecting and determining whether these two signals are true or false, and generates a sync tag signal “SyncFnd”. The principle of determining the sampling-start timing mentioned above is as follows.  
         [0037]     If the sync tag signal “SyncTagO” is true and the sync tag signal “SyncTag” is false, the sync tag signal “SyncTagO” is used as a base in the present embodiment to generate the sync tag signal “SyncFnd”. If the sync tag signal “SyncTagO” is false and the sync tag signal “SyncTag” is true, the sync tag signal “SyncTag” is used as a base to backwardly count a length of one frame&#39;s time as its sampling-start timing, and generates the sync tag signal “SyncFnd”, wherein in the present embodiment, for example, the sync tag signal “SyncTag” is used as a base to generate the sync tag signal “SyncFnd”. If both the sync tag signal “SyncTagO” and the sync tag signal “SyncTag” are true, in the present embodiment, for example, the sync tag signal “SyncTagO” is used as a base to generate the sync tag signal “SyncFnd”. However, it will be apparent to one of the ordinary skill in the art that in the case of both the sync tag signal “SyncTagO” and the sync tag signal “SyncTag” are true, the sync tag signal “SyncTag” also can be used as a base to generate the sync tag signal “SyncFnd”, and the result is the same as the present embodiment.  
         [0038]     The counter  432  counts the number from an initial value in accordance with a predetermined timing. In the present embodiment, the predetermined timing mentioned above is, for example, the clock signal “EFMCLK”, and the initial value mentioned above is, for example, a value of 0. The counter  432  outputs a counting value “cnt”, and the counting value “cnt” is reset to the initial value and the number is recounted again by the sync tag signal “SyncFnd” or a reset signal “reset”. A comparator  433  receives the counting result “cnt” and compares it with a predetermined value “n”. Once the counting result “cnt” is equal to the predetermined value “n”, the comparator  433  issues the reset signal “reset” and the data sampling tag signal “DataTag”. In the present embodiment, the reset signal “reset” and the data sampling tag signal “DataTag” are, for example, the same signal.  
         [0039]     In order to explain the present embodiment in greater details, a signal timing diagram is exemplified hereinafter for explanation.  FIG. 5  is a signal timing diagram of the optic disc sampling apparatus shown in  FIG. 4 . Referring to both  FIG. 4  and  5 , in the present embodiment, the memory  440  and the latch  420  maintain the data signal “DSEFM” and the sync tag signal “SyncTag” in the memory  440  and the latch  420  for a while, and output the signals as the data signal “DSEFMO” and the sync tag signal “SyncTagO”, respectively after delaying it for a frame cycle. As shown in  FIG. 5 , the sync tag signal “Ao” and the data signal “Adata” are delayed for a frame cycle as mentioned above, thus the sync tag signals “A” (i.e. Ao in the diagram) and “B” on both sides of the frame can be detected simultaneously. The counting-start position circuitry  431  generates a sync tag signal “SFa” based on the sync tag signals “Ao” and “B”. If the sync tag signal “B” cannot be generated by the accurate timing detection due to a scratch of the optic disc or other reason, the counting-start position circuitry  431  generates the sync tag signal “SFa” by using the timing of the sync tag signal “Ao” as its base. When the wrong sync tag signal “B” is maintained for a frame cycle and output as a sync tag signal “Bo”, in the present embodiment, the counting-start position detection circuitry  431 , for example, uses a sync tag signal “C” as a base to generate a sync tag signal “SFb”, such that the disadvantages of the prior art is improved.  
         [0040]     The foregoing description of the preferred embodiment of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form or to exemplary embodiments disclosed. Accordingly, the foregoing description should be regarded as illustrative rather than restrictive. Obviously, many modifications and variations will be apparent to practitioners skilled in this art. The embodiments are chosen and described in order to best explain the principles of the invention and its best mode practical application, thereby to enable persons skilled in the art to understand the invention for various embodiments and with various modifications as are suited to the particular use or implementation contemplated. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents in which all terms are meant in their broadest reasonable sense unless otherwise indicated. It should be appreciated that variations may be made in the embodiments described by persons skilled in the art without departing from the scope of the present invention as defined by the following claims. Moreover, no element and component in the present disclosure is intended to be dedicated to the public regardless of whether the element or component is explicitly recited in the following claims.