Abstract:
A method and apparatus for controlling reproduction speed of an optical disk are provided. The method for controlling reproduction speed of an optical disk includes checking whether a read command has been received, and examining whether the received read command is intended for performance evaluation based on the number of backward track jumps of a laser beam irradiated on the optical disk. The method and apparatus for controlling reproduction speed of an optical disk provide designed read performance when an external host executes a performance test.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The invention relates to a method and apparatus for controlling reproduction speed of an optical disk.  
         [0003]     2. Background of the Related Art  
         [0004]     For read-out of information recorded on an optical disk, such as compact disc (CD) or digital versatile disc (DVD), an optical disk reproducing apparatus irradiates a laser beam onto the optical disk through an objective lens and collects the reflected beam while rotating the optical disk at an appropriate speed using a spindle motor. The rotational speed of the optical disk determines the data reproduction speed, which is controlled by a servo control circuit that provides drive voltage to the spindle motor.  
         [0005]     With the advancement of servo technology, the access speed of an optical disk reproducing apparatus has improved rapidly. As a result, data recorded on an optical disk can be retrieved more rapidly than the normal 1× speed.  
         [0006]     Maximum-speed data reproduction requires maximum-speed rotation of the optical disk, which entails more vibration and noise generated by the rotation mechanism. If a host computer that requested data read-out from an optical disk does not take the data temporarily stored in a buffer on time, the optical disk reproducing apparatus should conduct backward track jumps, in which case the benefit of the maximum-speed rotation disappears.  
         [0007]     The optical disk reproducing apparatus, therefore, performs data read-out not with the maximum rotational speed but with a rather lower speed with a view to decreasing noise. For example, an optical disk reproducing apparatus with maximum rotational speeds approximately ˜24×-52× (rotational speed expressed in terms of CLV speed) in the CAV mode rotates the optical disk with ˜20×-48× speeds, ˜4× lower than the maximum speed at each location, as shown in  FIG. 1 .  
         [0008]     Users sometimes execute a test program, such as a Landmark test (bench mark) program, to measure the performance of their optical disk drives installed in their PCs. When executed, the test program issues disk read commands to the optical disk drive for measuring data read performance. The optical disk drive responsive to the commands performs data read-out at a speed rather lower than the maximum speed. Because the optical disk drive with maximum CAV speeds of ˜24×-52× performs data read-out with speeds of ˜20×-48×, the performance index obtained by the test program does not reflect the actual maximum performance of the optical disk drive.  
         [0009]     The performance index obtained by the test program, which is lower than the expected value, makes users doubt the performance of their disk drives, which may lead to unnecessary requests for repair service.  
       SUMMARY OF THE INVENTION  
       [0010]     An object of the invention is to solve at least the above problems and/or disadvantages and to provide at least the advantages described hereinafter.  
         [0011]     To achieve at least the above objects, in whole or in part, and in accordance with the purposes of the invention, as embodied and broadly described herein, there is provided a method for controlling reproduction speed of an optical disk in accordance with an embodiment of the invention that includes (a) checking whether a read command has been received and (b) examining whether the received read command is intended for performance evaluation based on the number of backward track jumps of a laser beam irradiated on the optical disk.  
         [0012]     To further achieve at least the above objects, in whole or in part, and in accordance with the purposes of the invention, as embodied and broadly described herein, there is provided a method for controlling reproduction speed of an optical disk in accordance with another embodiment of the invention that includes (a) checking whether a read command has been received sequentially more than a predefined number of times, and (b) reproducing data recorded on the optical disk with a maximum rotational speed depending on the checking result.  
         [0013]     To further achieve at least the above objects, in whole or in part, and in accordance with the purposes of the invention, as embodied and broadly described herein, a method for controlling reproduction speed of an optical disk in accordance with another embodiment of the invention is provided that includes (a) examining whether a received read command is intended for performance evaluation based on how many times the read command has been received sequentially, (b) examining whether the received read command is intended for performance evaluation based on a number of backward track jumps of a laser beam irradiated on the optical disk, and (c) reproducing data recorded on the optical disk with a maximum rotational speed if both step (a) and step (b) confirm that the received read command is intended for performance evaluation.  
         [0014]     To further achieve at least the above objects, in whole or in part, and in accordance with the purposes of the invention, as embodied and broadly described herein, there is provided an apparatus for reproducing an optical disk in accordance with an embodiment of the invention that includes a motor configured to rotate the optical disk, a reader configured to read signals recorded on the optical disk, a servo unit configured to control the reader and drive the motor, a signal processor configured to demodulate the signals read by the reader into digital data, and a controller configured to check whether a read command has been received sequentially more than a predefined number of times and reproduce data recorded on the optical disk with a maximum rotational speed by controlling the servo unit depending on the checking result.  
         [0015]     To further achieve at least the above objects, in whole or in part, and in accordance with the purposes of the invention, as embodied and broadly described herein, there is provided an apparatus for reproducing an optical disk in accordance with an embodiment of the invention that includes a motor configured to rotate the optical disk, a reader configured to read signals recorded on the optical disk, a servo unit configured to control the reader and drive the motor, a signal processor configured to demodulate the signals read by the reader into digital data, a controller configured to examine whether a received read command is intended for performance evaluation based on how many times the read command has been received sequentially, examine whether the received read command is intended for performance evaluation based on a number of backward track jumps of the reader, and reproduce data recorded on the optical disk with a maximum rotational speed by controlling the servo unit if both said examinations confirm that the received read command is intended for performance evaluation.  
         [0016]     Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]     The invention will be described in detail with reference to the following drawings in which like reference numerals refer to like elements wherein:  
         [0018]      FIG. 1  is a graph illustrating maximum reproduction speed and actual reproduction speed of an optical disk in a related art optical disk reproducing apparatus;  
         [0019]      FIG. 2  is a block diagram of an optical disk reproducing apparatus in accordance with an embodiment of the invention;  
         [0020]      FIG. 3  is a flowchart of a method of controlling reproduction speed of an optical disk in accordance with an embodiment of the invention;  
         [0021]      FIG. 4  is a detailed flowchart of a maximum speed reproduction mode in the method of  FIG. 3 ; and  
         [0022]      FIG. 5  illustrates an example showing the change of reproduction speed in accordance with embodiments of the invention. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0023]     Now, a method and apparatus for controlling reproduction speed of an optical disk in accordance with embodiments of the invention will now be described in detail with reference to the drawings, in which like reference numerals have been used to designate like elements.  
         [0024]      FIG. 2  is a block diagram of an optical disk reproducing apparatus in accordance with an embodiment of the invention. The optical disk reproducing apparatus of  FIG. 2  includes an optical pickup  12  for reproducing recorded signals from an optical disk  10 , an RF unit  14  for generating a binary signal conveying recorded data and focus/tracking error signals from the output of the optical pickup  12 , a DSP  15  for retrieving digital data from the binary signal, a memory  16  for temporarily storing the retrieved digital data, a buffer  17  for buffering data to be transferred to an external host, an interface unit  18  for exchanging data and commands with external devices, a servo control unit  20  for controlling the optical pickup  12 , a spindle motor M for rotating the optical disk  10 , and a microprocessor  26  for supervising the overall operation of the apparatus.  
         [0025]      FIGS. 3 and 4  are flowcharts of a method of controlling reproduction speed of an optical disk in accordance with an embodiment of the invention.  
         [0026]     If the optical disk  10  is loaded, in step S 10 , the microprocessor  26  initializes ‘seq_read_cnt’, which is a variable for storing the number of received sequential read commands, and ‘backjump_cnt, which is a variable for storing the number of backward track jumps, to 0, in step S 12 . The microprocessor  26  then waits for a command from an external host after performing initialization for servo control.  
         [0027]     After receiving a command for reading a particular area of the optical disk  10  from an external host through the interface unit  18 , the microprocessor  26  checks whether the command is for a sequential read operation, in step S 14 . The type of read command can be identified by the code thereof. If the received command is for other actions, such as random read, the microprocessor  26  performs the requested operation, in step S 15 . If the received command is a command for sequential read, the microprocessor  26  increments the variable ‘seq_read_cnt’, in step S 16 , and moves the optical pickup  12  to the area specified by the command through the servo control unit  20 , in step S 18 . The rotational speed of the optical disk  10  is not set to the maximum possible speed at the targeted area but a rather lower speed (for example, a speed ˜4× lower than the maximum possible speed).  
         [0028]     The signals read by the optical pickup  12  are converted into a binary signal by the RF unit  14  and then demodulated into digital data by the DSP  15 . The retrieved digital data is stored sequentially in the memory in order of demodulation, in step S 20 .  
         [0029]     The data stored in the memory  16  is moved to the buffer  17  by the microprocessor  26  and the data in the buffer  17  is transferred to the external host PC through the interface unit  18 . Each time the buffer  17  becomes empty, the microprocessor  26  loads the buffer  17  with the digital data stored in the memory  16 . The microprocessor  26  measures the elapsed time (RT) since the data read-out initiated by the first sequential read command using an internal timer.  
         [0030]     While executing the aforementioned steps, the microprocessor  26  checks whether the size of data stored in the memory  16  exceeds a predefined limit (for example, ˜80% of the memory size), in step S 22 . If the predefined limit is exceeded, the microprocessor  26  instructs the servo control unit  20  to perform a backward jump of the optical pickup  12 , in step S 24 , and increments the variable ‘backjump_cnt’, in step S 26 .  
         [0031]     If the elapsed time (RT) measured by the microprocessor  26  is within a predefined limit (for example, ˜5 seconds), the microprocessor  26  checks whether the sequential read of the data block requested by the read command has been completed, in step S 34 . If the requested sequential read operation has not been completed and no request to stop the data read operation has been received, in step S 36 , the microprocessor  26  repeats the aforementioned steps from step S 20  until the requested sequential read operation is completed or a request to stop the data read operation is received.  
         [0032]     If the sequential read of the requested data block has been completed, in step S 34 , the microprocessor  26  waits for a next command. If a next command is received and the command is not for a sequential read operation, the microprocessor performs the requested operation, in step S 15 , and initializes the variables ‘seq_read_cnt’ and ‘backjump_cnt’, in step S 12 . If the next command is for a sequential read operation, the microprocessor  26  leaves the variables ‘seq_read_cnt’ and ‘backjump_cnt’ unchanged and repeats the aforementioned steps from step S 16 .  
         [0033]     If the sequential read command is repeated several times and the elapsed time (RT) since the initial sequential read command exceeds a predefined duration (Tref), in step S 27 , the microprocessor  26  reads the content of the variable ‘seq_read_cnt’, in step S 28 . If the value stored therein is less than a predefined number (N), the microprocessor  26  continues the current sequential read operation; otherwise, the microprocessor  26  guesses that the repeated sequential read command is intended for performance evaluation and reads the content of the variable ‘backjump_cnt’, in step S 30 . If the value stored therein is less than a predefined number (M), the microprocessor  26  concludes the repeated sequential read command to be intended for performance evaluation; otherwise, the microprocessor  26  continues the current read operation.  
         [0034]     If the sequential read operation has been continued during the predefined period Tref, the sequential read command is probably intended for performance evaluation. Moreover, if the number of backward track jumps conducted during the sequential read operation is less than the predefined number M, it is almost certain that the read command is intended for performance evaluation because the data read from the optical disk is transferred to the external host through the buffer  17  sufficiently fast at the current rotational speed. Because read operations for evaluating performance simply repeat overwriting data blocks that were read sequentially from the optical disk on a same storing space without moving the read data blocks to another storage medium, interpreting or decoding of the read data blocks, the external host can focus only on the read operations and therefore the read throughput is usually very high.  
         [0035]     Theoretically, read operations intended for performance evaluation do not cause backward track jumps. In reality, however, backward jumps are sometimes required due to disk read errors resulting from disk defects. In the embodiments of the invention, therefore, the read operations are considered to be intended for performance evaluation if the number of backward track jumps conducted during the predefined period Tref is less than the predefined number M. If the number of sequential read commands received during the predefined period Tref exceeds N and the number of backward track jumps conducted during Tref is less than the predefined number M, the microprocessor  26  regards the situation as a performance evaluation operation and executes the maximum-speed data reproduction routine, in step S 32 .  
         [0036]      FIG. 4  is a detailed flowchart of the maximum-speed reproduction mode in the method of  FIG. 3 . Once the maximum-speed reproduction mode starts, the microprocessor  26  controls the servo control unit  20  to rotate the optical disk  10  with a maximum possible speed at the current position. In the example shown in  FIG. 5 , if the optical disk  10  has been rotated at ˜32× speed, the rotational speed is increased to ˜36× (vj in  FIG. 5 ).  
         [0037]     While reproducing the optical disk  10  with the maximum rotational speed, the microprocessor  26  does not examine the values of the variables (seq_read_cnt and backjump_cnt) and conducts backward track jumps only if needed, in steps S 323  and S 324 . If a command received during the maximum-speed reproduction operation is also for sequential read, in step S 328 , the microprocessor  26  moves the optical pickup  12  to the target position, in step S 329 , and continues the maximum-speed reproduction operation at the position, in step S 321 ; otherwise, the microprocessor  26  performs the requested operation, in step S 15 , and exits the maximum-speed reproduction routine. The microprocessor  26  then rotates the optical disk with a speed lower than the maximum rotational speed, in step S 18 , and determines whether to enter the maximum-speed reproduction mode as described before.  
         [0038]     The method and apparatus for controlling reproduction speed of an optical disk according to embodiments of the invention provide at least the following advantages.  
         [0039]     The method and apparatus for controlling reproduction speed of an optical disk according to embodiments of the invention are capable of coping with performance evaluation by adjusting the rotational speed of the optical disk. Further, the method and apparatus for controlling reproduction speed of an optical disk according to embodiments of the invention provide designed read performance when an external host executes a performance test.  
         [0040]     The foregoing embodiments and advantages are merely exemplary and are not to be construed as limiting the invention. The present teaching can be readily applied to other types of apparatuses. The description of the invention is intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures.