Abstract:
A method for playing back multiple kinds of optical discs includes making a decision as to whether a played back optical disc is classified into a digital video disc (DVD) or compact disc (CD) class, detecting the synchronization pattern of the identified disc class, reading a data stream from the optical disc by controlling the voltage controlled oscillation and the constant linear speed of the disc according to the identified disc class, decoding the data stream into the identified disc class according to the detected synchronization pattern, and transferring the decoded data stream to an audio/video decoder or a ROM decoder.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a device for playing back an optical disc, and more particularly to a device for selectively playing back multiple kinds of optical discs. 
     The present invention is based on Korean Patent Application No. 21581/1996, which is incorporated by reference herein for all purposes. 
     2. Description of the Related Art 
     Generally a digital video disc (DVD) is one type of digital moving picture disc media, which is a popular type of multimedia memory for recording high image qualities and tones. More specifically, the digital video disc is a next generation recording medium for storing more than two hours of digital images according to the Moving Picture Experts Group 2 (MPEG-2) standard. Because the digital video disc and a conventional compact disc (CD) have an optical system in common, they are very similar to each other with respect to writing and reading a signal. Nevertheless each disc system uses its own play back system which is different from the other. Accordingly, inefficient utilization of resources and an economical burden on users results from these differences. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a method for selectively playing back multiple kinds of optical discs. 
     Another object of the present invention is to provide an apparatus for selectively playing back multiple kinds of optical discs. 
     According to an embodiment of the present invention, a method for playing back multiple kinds of optical discs is provided to achieve the above objects, in which the method comprises identifying a disc class in which a played back optical disc is classified, wherein the class is one of a digital video disc (DVD) class and a compact disc (CD) class; detecting a synchronization pattern of the identified disc class; reading a data stream from the played back optical disc by controlling a voltage controlled oscillation and a constant linear speed of the played back optical disc according to the detected synchronization pattern; decoding the data stream according to the identified disc class based on the synchronization pattern thereby generating a decoded data stream; and transferring the decoded data stream to at least one of first and second decoders. 
     In order to achieve the other object there is provided a system decoder for playing back multiple kinds of optical discs employed in an apparatus having a disc drive controller for driving an optical disc and at least one of an audio/video decoder and a read-only memory (ROM) decoder, the system decoder comprising: a microcomputer for generating a disc identification signal to indicate the type of a played back optical disc, operation control signals for driving play back of the optical disc and processing data played back from the optical disc in response to the disc identification signal, and a data transmission signal upon receiving a data transmission start signal from the one of the audio/video decoder and ROM decoder; first data processing unit for demodulating, correcting errors on and descrambling a digital video disc data according to the disc identification signal; second data processing unit for demodulating and correcting errors in a compact disc data according to the disc identification signal; a switching unit for selectively transmitting the data stream played back from the optical disc to the first and second data processing unit according to the disc identification signal; synchronization detection unit for generating a synchronization detection signal for detecting various synchronization patterns of relevant types of discs according the disc identification signal; a memory used by both the first and second data processing unit for correcting errors and buffering data; a memory controller for controlling access to the memory to read data stored in the memory in response to one of the transmission control signal and operation of the one of the first and second data processing unit according to the disc identification signal; and interfacing unit for transmitting the data read from the memory to the audio/video decoder or the ROM decoder according to the disc identification signal. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete appreciation of this invention, and many of the attendant advantages thereof, will be readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings, in which like reference symbols indicate the same or similar components, wherein: 
     FIG. 1 is a block diagram for illustrating a preferred configuration of a device for selectively playing back multiple kinds of optical discs according to the present invention; and 
     FIG. 2 is a block diagram for illustrating a preferred configuration of a system decoder shown in FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A preferred embodiment of a method for playing back multiple kinds of optical discs according to the present invention is described below in detail with reference to the accompanying drawings. 
     It is noted that the same elements are given the same reference number even in different figures, and some specified description such as configuration of circuits and elements are provided only for general understanding. So it will be evident that people having common knowledge of the field will understand the present invention to be executed without being limited by the specified description provided here. A detailed description of related conventional functions and configurations is omitted in order to avoid confusion with the essence of the present invention. 
     Referring to FIG. 1, a disc  100  is rotated at a specific speed by a disc motor  160 , and disc information recorded on the disc is converted into a radio frequency RF analog signal which is output from an optical pick-up device having a head  120 . A data stream, modulated by eight-to-sixteen modulation or eight-to-fourteen modulation (ESM/EFM) and shaped as a pulse wave, is transferred to a system decoder  200  which outputs control signals Sf 1  and Sf 2  to a phase locked loop (hereinafter referred to as a ‘PLL’)  300 . The system decoder  200  consists of a DVD processing means for processing data read from a digital video disc (DVD) and a digital video ROM disc (hereinafter referred to as DVD system) and a CD processing means for processing data read from a compact disc (CD) (hereinafter referred to as a ‘CD system’). A microcomputer  500  is a controller device for controlling the overall operation of the system for playing back multiple kinds of optical discs so as to perform optimal control according to each kind of optical disc by setting a prescribed register as set forth in Table 1 below, and generating a transmission control signal by receiving a data transmission operation signal from an audio/video decoder  600 . 
     
       
         
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 disc2 
                 disc1 
                 disc0 
                 Type of disc 
               
               
                   
               
             
             
               
                 1 
                 0 
                 0 
                 DVD 
               
               
                 1 
                 1 
                 0 
                 DVD-ROM 
               
               
                 0 
                 0 
                 0 
                 CD-DA 
               
               
                 0 
                 0 
                 1 
                 V-CD 
               
               
                 0 
                 1 
                 0 
                 CD-ROM 
               
               
                 0 
                 1 
                 1 
                 CD-G 
               
               
                   
               
             
          
         
       
     
     Here, DVD is a digital video disc, DVD-ROM is a digital video ROM disc, CD-DA is a compact disc-digital audio disc, V-CD is a video compact disc, CD-ROM is a compact disc read-only memory, and a CD-G is a compact disc graphics disc. 
     A digital phase synchronization loop, comprising a phase comparison circuit, a voltage controlled oscillator and a frequency demultiplier, generates, a first clock synchronized with a signal played back from any type of optical disc. A disc drive controller  400  controls the disc rotation to a constant linear speed and controls disc related operations by considering frequency servo signals and phase servo signals according to a frame synchronization signal Sf provided from a synchronization detector  220  in the system decoder  200 . An audio/video decoder  600  classifies data from the system decoder  200  into audio and video data, and restores the original audio source data and video source data, respectively. The audio/video data demodulated by the audio/video decoder  600  is transferred to an NTSC or PAL encoder  700  and a digital/analog converter  800  and is output to a monitor  960  and a speaker  970 , respectively. ROM decoder  950  built into a host, such as personal computer, is operated by the computer and transfers data from the system decoder  200  to the host via an interface. 
     Referring to FIG. 2, a memory  280  preferably is a dynamic RAM which is used as a buffer for compensating for differences in disc input/output rates and in correcting DVD data errors. 
     A switch  297  provides for separate DVD and CD processing according to first disc identification signal disc 2  provided by the microcomputer (micro)  500 . For example, in the register setting operation described above, a play back signal is transmitted to a first demodulator  250  if the disc is a DVD in the case of first disc identification signal disc 2  being ‘1’ and the play back signal is transmitted to a second demodulator  255  if the disc is a CD in the case of disc 2  being ‘0’. 
     The first demodulator  250  demodulates the ESM input data stream in units of a symbol comprised of a prescribed number of bits. That is, the first demodulator  250  transfers the ESM data stream to a 32 bit shift register  211 , and selects and transfers the upper or lower 16 bits of the 32 bits output from the 32 bit shift register  211  to a 16-8 demodulator  212 . The 16-8 demodulator  212  converts the input 16 bits of data into a symbol of 8 bits and transfers it, since the data is modulated by eight-to- sixteen modulation (ESM) when written on disc  100 . 
     The second demodulator  255  transfers the EFM data stream to a 23 bit shift register  215 , and selects and transfers the upper or lower 14 bits of the 23 bits output from the 23 bit shift register  215  to a 14-8 demodulator  214 . The 14-8 demodulator  214  converts the input 14 bit data into a symbol of 8 bits and transfers it, since the data is modulated by eight-to-fourteen modulation (EFM) when written on disc  100 . 
     A synchronization detector  220  generates signals Sf, Sid, Se for detecting synchronization patterns such as a frame synchronization of a standard clock used in controlling rotation of disc  100 , a sector synchronization for classifying sectors and an error correction synchronization for reading data in an error correction block when correcting errors. Also it establishes a window for recognizing if synchronization, detected within a restricted range, is valid and forces generation of a detection signal in case of no synchronization. 
     An interface  295  interfaces the micro  500  and the system decoder  200 . 
     A memory controller  270  generates a row address signal, a column address signal and other address signals necessary for correcting errors in or buffering data played back from the relevant disc according to first through third disc identification signals disc 2 -disc 0 , and prevents overflow and underflow. The memory controller  270  also controls operations for reading data from memory  280  to transfer it to the audio/video decoder  600  or ROM decoder  950 . 
     A first error corrector  230  vertically and horizontally corrects errors in an error correction block of data read from a DVD system disc. For convenience&#39;s sake, it is assumed that the horizontal and vertical directions are 182-172-11 and 208-192-17. In other words, the length of the code words are 182 and 208 bits, the main data bits (except for parity bits) are 172 and 192 bits in length, and the intervals between code words are 11 and 17 bits, respectively. During error correction, the memory  280  forms the error correction block by storing ID data and main data in units of a block. The error correction block comprises 16 sectors of data. 
     A second error correction means  235  corrects errors in data read from a CD system disc by using a conventional Cross Interleave Reed Soloman code. The memory  280  buffers data and stores the corrected data generated between the two correctors. 
     A descrambler  240  restores received data to the original main data by descrambling the main data of the DVD system data stored in memory  280 , which is scrambled before being written on the disc, in which the main data is 2 kilobytes in length. 
     An error detector  260  detects an error contained in data transmitted from the descrambler  240 . The error provides information helpful in deciding whether repetition of error correction by the micro  500  is necessary. 
     A deinterleave unit  340  may be constructed to incorporate interleave rules, an address counter and an adder, so as to store data according to an original arrangement by restoring data interleaved in units of a frame by controlling the write/read address of the memory  280 . For example, in the present embodiment of the invention, the interleave unit  340  is shown to be arranged separately, but it can be contained in the physical circuit of the memory controller  270 , and error correction, descrambling and deinterleave operations are performed. 
     An ID error corrector  296  corrects errors in the ID data transferred from the 16-8 demodulator  212 . The corrected ID data, with an ID flag, is transferred to micro  500  and is used so as to let micro  500  control a DVD system disc  100  searching operation. The corrected ID data is stored in the relevant area of the memory  280 . The stored ID data having any uncorrected error in the main data is corrected again by the first error corrector  230  and replaced in the memory  280  with the corrected ID data and transferred to audio/video decoder  600  or interface  295  together with scrambled main data. The ID error corrector  296  performs error correction on an ID of a different source by properly dividing a sector synchronization period. For example, suppose that an ID correction type is a Reed-Solomon RS(6, 4, 3) type, where “6” is the codeword length, “4” is the main data, and 3 is the interval between codewords. A subcode detector  294  extracts subcode data P-W from the CD system demodulated data transferred from the 14-8 demodulator  214 . A first selector  291  transmits the corrected ID data from the ID error corrector  296  or a subcode Q bit and error flag from the subcode detector  294  through micro interface  295  to the micro  500 . The selection depends on the state of the first disc identification signal disc 2  which indicates whether the data is from a CD or DVD system. 
     An interface unit  290  performs interfacing between the system decoder  200  and the audio/video decoder  600 . The memory controller  270  reads and transmits descrambled DVD system data from memory  280  through the interface unit  290  to audio/video decoder  600  and ROM decoder  950  according to the system clock, under control of micro  500 . The interface unit  290  performs the operations of timing control, eliminating noise, changing signal arrangement and decoding addresses. The interface unit  290  comprises a switch  292  and a conventional CD-ROM decoder  293  for transmitting data read from a video compact disc (V-CD) to the CD-ROM decoder  293 . Typically, the audio/video decoder  600  does not include a CD-ROM decoder, and it may be omitted if not necessary. The switch  292  is connected to the CD-ROM decoder  293  in the case of first to third disc identification signals disc 2 -disc 0  having values 0,0,1, respectively. 
     Second selector  298  of the interface unit  290  selects V-CD data processed by the CD-ROM decoder  293 , DVD system data from the memory  280 , or CD system data or one of the subcodes R, S, T, U, V, and W (CD-G data) detected from the subcode detector  294 , and transmits ROM data (DVD ROM and CD-ROM) to ROM decoder  950  and other CD or DVD system data to the audio/video decoder  600  according to the first to third disc identification signals, disc 2 -disc 0 , output from micro  500 . 
     Thus, the play back system of the present invention has multiple functions of a CD system and DVD disc play back system, which are selectively chosen. While there have been illustrated and described what are considered to be preferred embodiments of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made, and equivalents may be substituted for elements thereof, without departing from the true scope of the present invention. In addition, many modifications may be made to adapt a particular situation to the teachings of the present invention without departing from the central scope thereof. Therefore, it is intended that the present invention not be limited to the particular embodiment disclosed herein as the best mode contemplated for carrying out the present invention, but that the present invention includes all embodiments falling within the scope of the appended claims. 
     Other modifications and variations to the invention will be apparent to those skilled in the art from the foregoing disclosure and teachings. Thus, while only certain embodiments of the invention have been specifically described herein, it will be apparent that numerous modifications may be made thereto without departing from the spirit and scope of the invention.