Abstract:
A discrimination method of an optical storage medium is provided. The method scans a plurality of data recording points, and obtains a channel bit rage according to the scanned data recording points. After obtaining the channel bit rate, the channel bit rate is compared with a predetermined value, and the optical storage medium used for storing the data recording points is discriminated by checking the channel bit rate.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application is a continuation-in-part of a prior application Ser. No. 10/693,052, filed on Oct. 23, 2003, now pending, which claims the priority benefit of Taiwan application serial no. 91124661, filed on Oct. 24, 2002. All disclosures are incorporated herewith by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a discrimination method of the optical storage medium, and more particularly, to a method for discriminating an optical storage medium with various storage formats according to a channel bit rate of the optical storage medium.  
         [0004]     2. Description of the Related Art  
         [0005]     Along with the diversity of technology development, new optical storage mediums are continuously being launched into the market. Currently, the optical storage medium is roughly classified into two categories: Digital Versatile Disk (DVD) and Optical Disk (CD). Since both of the optical storage mediums are widely utilized in the current market, in order to facilitate the user&#39;s operations, many vendors start to develop and manufacture the optical reading apparatus that is capable of reading various types of optical storage medium. However, since such two optical storage mediums are essentially different in both physical specification and data storage format, inevitably, the optical reading apparatus capable of reading two types of storage medium must have a capability of discriminating one type of the optical storage medium from the other.  
         [0006]     For example, the optical reading apparatus may first assume that the optical storage medium to be read is a DVD, and uses the parameters required for reading the DVD to drive the pick-up head to read data recorded on the DVD. Once the correct data cannot be obtained by such assumption, the optical reading apparatus is reconfigured to read the CD, and the parameters required for reading the CD is used to drive the pick-up head to read data recorded on the CD. However, whether the assumption is correct or not is only certain at the moment when the data is being read, and requires performing the processes such as light source switching, focusing, and tracking before reading the data. Accordingly, a great amount of time is required to perform the reconfiguration in case the assumption is incorrect. In addition, it is very hard to control the time spent on discrimination of the optical storage medium and the time can be varied in a wide range. Accordingly, the user may misjudge the apparatus is malfunction or the system is failed due to the great variance of the operation time required for discriminating the optical storage medium by the optical reading apparatus.  
       SUMMARY OF THE INVENTION  
       [0007]     Therefore, it is an object of the present invention to provide a discrimination method of the optical storage medium, such method can easily discriminate the type of the currently used optical storage medium.  
         [0008]     The present invention provides a discrimination method of the optical storage medium. The method scans a plurality of data recording points at 1× speed, and obtains a channel bit rate according to the scanned data recording points. After obtaining the channel bit rate, the channel bit rate is compared with a predetermined value, and the optical storage medium used for storing the data recording points is discriminated by checking the channel bit rate.  
         [0009]     The present invention identifies the optical storage medium according to the channel bit rate that is coexisted but varies greatly between the DVD and CD, thus, the present invention can effectively determine which type of the currently used optical storage medium is. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a portion of this specification. The drawings illustrate embodiments of the invention, and together with the description, serve to explain the principles of the invention.  
         [0011]      FIG. 1  schematically shows a diagram illustrating a reading method and the data storage format of a compact disk (CD).  
         [0012]      FIG. 2  schematically shows a flow chart illustrating a discrimination method of the optical storage medium according to an embodiment of the present invention.  
         [0013]      FIG. 3  schematically shows a flow chart illustrating a discrimination method of the optical storage medium according to another embodiment of the present invention.  
     
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0014]     For one of the ordinary skills in the art to easily understand the spirit of the present invention, the reading method and the data storage format of the optical storage medium is described hereinafter.  FIG. 1  schematically shows a diagram illustrating a reading method and the data storage format of a compact disk (CD). Data is burned on the CD as the pits a 1 , a 3 , and a 5  and the lands a 2  and a 4  as shown in  FIG. 1  after converted by an eight to fourteen (8-14) modulation (EFM) process. The pits and lands that form the tracks on the disc are together referred to as the data recording points. When reading the CD, the data represented by the data recording points is read out after the processes of turning on the light source, spinning the CD, focusing, and tracking, are performed.  
         [0015]     When reading the data, the light is emitted on the tracks and reflected onto the pick-up head. Compared to the lands, the pits are essentially the grooves in the disc. As shown in  FIG. 1 , since the lightness of the reflected light beam on different locations is not the same, the lightness of the pits is lower than the lightness of the lands. Then, the lightness obtained by the pick-up head is digitalized to a corresponding logic value, and a waveform formed by the logic values is read based on a variable frequency clock PLL, and further converted to a digital data by using the EFM encoding method.  
         [0016]     As shown in  FIG. 1 , the logic values are transited at the time points t 1 , t 2 , t 3 , t 4 , t 5  and t 6 . In the following description, the time points where the transition occurs are defined as the data transition points, and the interval between two adjacent data transition points is referred as a transition interval. In order to comply with the EFM encoding specification, the length of each transition interval should be equal to 3-11 periods of the clock PLL, and only the logic values at the data transition points are equal to the logic value 1, the rest of the logic values are equal to the logic value 0. Accordingly, as the data shown in  FIG. 1 , the EFM encoded value is 100100001000000100000000001001, and the length of the transition interval is 3, 5, 7, 11 and 3 from left to right, respectively.  
         [0017]     The Digital Versatile Disk (DVD) also uses similar encoding method as the CD. The difference is that the CD uses the 8-14 encoding method, but the DVD uses the 8-16 encoding method. Moreover, the encoding method used by the DVD has a limitation that the length of each transition interval must be from 3-14 periods of the clock PLL.  
         [0018]     However, the clock PLL of  FIG. 1  is generated after the plurality of data recording points has been read and calculated, and the frequency of the clock PLL is actually the channel bit rate of the optical storage medium. From the perspective of the current standard, the channel bit rate of the DVD when it is stably reading data at 1× speed is 26.16 Mbps, and the channel bit rate of the CD when it is stably reading data at 1× speed is 4.3218 Mbps.  
         [0019]     During the initialization, the computer system (or the optical reading apparatus) reads the synchronous data from the optical storage medium, and also sequentially defines the appropriate clock PLL while reading the synchronous data.  FIG. 2  schematically shows a flow chart illustrating a discrimination method of the optical storage medium according to an embodiment of the present invention. In the present embodiment, first the computer system reads the synchronous data from the optical storage medium at 1× speed (step S 200 ). Since multiple data recording points that are complying with the predetermined specification are contained in the synchronous data, after the synchronous data has been read, the computer system can determine the frequency of the clock PLL according to the length of the synchronous data interval (step S 202 ). If it is determined that the frequency of the clock PLL is essentially equal to 4.3218 Mbps, the optical storage medium is discriminated as a CD, otherwise, the optical storage medium is discriminated as a DVD (step S 204 ). Wherein, the “essentially” herein indicates that both values may be either totally the same or the error thereof is within an acceptable range.  
         [0020]     Alternatively, in the aforementioned step S 204 , if the frequency of the clock PLL is essentially equal to 26.16 Mbps, the optical storage medium is discriminated as a DVD, otherwise the optical storage medium is discriminated as a CD.  
         [0021]      FIG. 3  schematically shows a flow chart illustrating a discrimination method of the optical storage medium according to another embodiment of the present invention. In the present embodiment, the data recording points read by the computer system at 1× speed are not necessarily to be limited as the aforementioned synchronous data. Instead, it can be any data recording point (step S 300 ). Then, the computer system discriminates the most appropriate frequency for the clock PLL or the channel bit rate according to the length of the read data recording point interval or duration (step S 302 ).  
         [0022]     Although the maximum transition interval of the DVD is predefined as 14T and the maximum transition interval of the CD is predefined as 11T in the specification, actually, the length of the maximum transition interval of the DVD is lower than the length of the maximum transition interval of the CD. In other words, under the same 1× speed condition, the frequency (i.e. the channel bit rate) of the clock PLL when reading the DVD must be higher than the frequency in reading the CD. Accordingly, as long as an appropriate predetermined value between the DVD channel bit rate (26.16 Mbps) and the CD channel bit rate (4.3218 Mbps) is found, the type of the optical storage medium can be easily discriminated by comparing the frequency of the clock PLL with the predetermined value (step S 304 ). In other words, in a case where the predetermined value is 10 Mbps, the optical storage medium is discriminated as a CD if the frequency of the clock PLL is lower than the predetermined value (step S 306 ), and the optical storage medium is discriminated as a DVD if the frequency of the clock PLL is higher than the predetermined value (step S 308 ).  
         [0023]     In summary, in the discrimination method of the optical storage medium provided by the present invention, since the frequency (i.e. the channel bit rate) of the clock PLL generated by the 1X speed is the mandatory parameter before formally reading the data, the speed of discriminating the optical storage medium is effectively improved by using the channel bit rate as the base of the discrimination.  
         [0024]     Although the invention has been described with reference to a particular embodiment thereof, it will be apparent to one of the ordinary skills in the art that modifications to the described embodiment may be made without departing from the spirit of the invention. Accordingly, the scope of the invention will be defined by the attached claims not by the above detailed description.