Patent Publication Number: US-6341112-B1

Title: Multi-rate optical disc recording and reproducing apparatus

Description:
This application is a continuation-in-part of application Ser. No. 08/752,037 filed on Nov. 19, 1996 now U.S. Pat. No. 5,982,726, the entire contents of which are hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to an optical disc recording and reproducing apparatus that optically accesses the optical disc, and more particularly recording method and apparatus of a multi-rate optical disc wherein the optical disc can be adaptively driven based on a transfer rate of data to be recorded. 
     2. Description of the Prior Art 
     In a conventional optical disc recording and reproducing apparatus, light beams are irradiated onto the optical disc such as Compact Disc(CD) and Digital Versatile (or Video) disc (DVD) in order to access data. Such optical discs record binary data representing audio signals, video signals, text information, etc. 
     Digital signals recorded onto the optical disc and reproduced therefrom include various recording signals such as a video signal, an audio signal, digital data or a digital broadcasting program including a combination of all of said signals, etc. Each of these signals has a different data quantity, for example digital bit quantity per second, respectively. Also, in the same broadcasting program, the data quantity is different according to the attribute of a broadcasted program. Specifically, the data quantity is about 6 to 7 Mbps in the case of a sports program, whereas the data quantity is generally about 3 to 4 Mbps in the case of a movie program. Moreover, the data quantity may differ according to the number of pixels of a program being provided. Specifically, the data quantity is about 5 to 6 Mbps in the case of the existed NTST and PAL signals having an array of about 720×480 pixels (normal video signal hereinafter), whereas the data quantity is generally about 10 to 15 Mbps in the case of a high density signal having an array of 1024×1024 pixels (high resolution signal hereinafter). Optical disc apparatuses must therefore be capable of recording and reproducing digital programs having such various data quantities. 
     However, a conventional optical disc has only a single-rate recording means. The following is a description of an example of a conventional optical disc recording and reproducing apparatus, which records and reproduces the normal video signal of 5 Mbps and the high resolution signal of 10 Mbps to/from a conventional optical disc. The conventional optical disc recording and reproducing apparatus drives the optical disc at a transfer rate of 10 Mbps on the optical disc. Consequently, when recording the high resolution video signal of 10 Mbps in a real time, the conventional optical disc recording and reproducing apparatus can exploit the entire recording area of the optical disc, that is, 100% of recording area in the optical disc. By contrast, when recording the normal video signal of 5 Mbps in real time, the conventional optical disc recording and reproducing apparatus wastes half the record area, that is, 50% of record area in the optical disc unnecessarily. Such a conventional optical disc recording and reproducing apparatus also wastes the recording area unnecessarily when recording the audio signal and the text signal with different transfer rates. 
     For reference, the following describes the process in which the high resolution video signal and the normal video signal are recorded respectively, using the optical disc recording and reproducing apparatus. 
     FIG. 1 is a time chart for explaining the process in which the high resolution video signal of 10 Mbps is recorded by the optical disc recording and reproducing apparatus. The frame dividing signal FDS shown in FIG. 1 assigns odd number and even number frames of the video signal. The high logic region and the low logic region of the frame dividing signal FDS represent the odd number frames and the even number frames, respectively. The high resolution video data divided into frame units according to this frame dividing signal is inputted to optical disc recording and reproducing apparatus at a rate of 10 Mbps. Then, the optical disc recording and reproducing apparatus formats the high resolution video signal HVD in a certain form required by an optical disc, and records on the optical disc. At this time, the optical disc is rotated at a constant velocity by the optical disc recording and reproducing apparatus like DSS shown in FIG.  1 . As a result of this, an information pit train IPT is formed on the information track of the optical disc having frame video data pits arranged continuously, as shown in FIG.  1 . 
     FIG. 2 is a time chart for explaining the process in which the normal resolution video signal of 5 Mbps is recorded by the optical disc recording and reproducing apparatus. In FIG. 2, the normal video data NVD are divided into frame units by the frame dividing signal FDS. This normal video data is inputted to the optical disc recording and reproducing apparatus at a transfer rate of 5 Mbps, and formatted, like FNVD in FIG. 2, by the optical disc recording and reproducing apparatus. The formatted normal video data FNVD consists of compressed frame video data and null data inserted between the compressed frame video data. These null data are generated because the normal video data NVD of 5 Mbps is temporally compressed into ½ by the optical disc recording and reproducing apparatus operating at a rate of 10 Mbps. In turn, the formatted normal video data FNVD are recorded on the optical disc using the optical recording and reproducing apparatus. At this time, the optical disc rotates at the same velocity used to record the high resolution video data. As a result of this, an information pit train IPT is formed on the information track of optical disc in which video data pit regions, and null data pit regions are arranged alternately. 
     As described above, the conventional optical disc recording and reproducing apparatus causes the null data to be recorded on optical disc because it records data on the optical disc at a fixed transfer rate, regardless of the transfer rate of data. The conventional optical disc recording and reproducing apparatus therefore wastes the recording area of the optical disc unnecessarily. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide multi-rate optical disc recording method and apparatus which can prevent the unnecessary waste of the storage area of optical disc by recording data on the optical disc in response to the transfer rate of data. 
     In order to obtain the above object, a multi-rate optical disc recording method according to one aspect of the present invention comprises steps of detecting a transfer rate of the digital signal, controlling a rotation velocity of the optical disc in accordance with the transfer rate of the digital signal, and recording the digital signal on the optical disc. 
     A multi-rate optical disc recording method according to another aspect of the invention comprises steps of setting a recording speed of the digital signal, controlling a rotation velocity of the optical disc in accordance with the recording speed, converting a transfer rate of the digital signal in accordance with said recording speed, and recording the converted digital signal on the optical disc. 
     A multi-rate optical disc recording method according to another aspect of the invention, in an optical disc recording apparatus for accessing an optical disc optically, comprises steps of detecting a transfer rate of a first digital signal generated from a digital signal source, rotating the optical disc at a speed corresponding to the transfer rate of the first digital signal, deciding whether a second digital signal was recorded on the optical disc or not, and recording the first digital signal from a final position of the second digital signal in the optical disc. 
     A multi-rate optical disc recording method according to still another aspect of the invention, in an optical disc recording apparatus including an optical pick-up for accessing a spiral information track on an optical disc optically, comprises steps of detecting a transfer rate of a first digital signal generated from a digital signal source, rotating the optical disc at a speed corresponding to a transfer rate of the first digital signal, deciding whether a second digital signal was recorded on the optical disc or not, comparing whether a transfer rate of the second digital signal is identical to that of the first digital signal, changing a rotation velocity of the optical disc into a speed corresponding to the transfer rate of the second digital signal, detecting a final position of the second digital signal on the information track and information about the final position, changing the rotation velocity of the optical disc into the speed corresponding to the transfer rate of said first digital signal, waiting until the rotation velocity of the optical disc arrives at the speed corresponding to the transfer rate of the first digital signal, jumping reversely the optical pick-up into a position prior to the final position of the second digital signal, and applying the first digital signal to the optical pick-up to record it on the optical disc. 
     Further, a multi-rate optical disc recording apparatus according to one aspect of the present invention comprises means for detecting a transfer rate of a digital signal from a digital signal source, optical disc driving means for rotating the optical disc in response to the transfer rate of the digital signal detected by the transfer rate detecting means, and means for recording the digital signal on the optical disc at the transfer rate detected by the transfer rate detecting means. 
     A multi-rate optical disc recording apparatus according to other aspect of the present invention comprises means for recording a digital signal from a digital signal source on an optical disc, record mode determining means for a recording speed of the digital signal, and means for controlling a rotation velocity of the optical disc in response to the recording speed determined by the record mode determining means. 
     A multi-rate optical disc recording apparatus according to another aspect of the present invention comprises means for detecting a transfer rate of a digital signal from a digital signal source, optical disc driving means for rotating the optical disc in response to the transfer rate of the digital signal detected by the transfer rate detecting means, and means for recording the digital signal on the optical disc at the transfer rate detected by the transfer rate detecting means. 
     A multi-rate optical disc recording apparatus according to still another aspect of the present invention comprises means for detecting a transfer rate of a digital signal from a digital signal source, buffer means for storing the digital signal from the digital signal source temporarily, variable clock generating means for generating a clock signal of variable frequency, disc driving means for rotating the optical disc, means for recording a digital signal stored in the buffer means on the optical disc in response to the clock signal from the variable clock generating means, and means for controlling the variable clock generating means and the disc driving means in response to the transfer rate detected by the transfer rate detecting means to control a frequency of the clock signal and a rotation velocity of the optical disc. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects of the invention will become apparent from the following detailed description of the embodiments of the present invention with reference to the accompanying drawings, in which: 
     FIG. 1 shows a timing chart for explaining the process in which the high resolution video data are recorded on the optical disc by the conventional optical disc recording and reproducing apparatus. 
     FIG. 2 shows a timing chart for explaining the process in which the normal video data are recorded on the optical disc by the conventional optical disc recording and reproducing apparatus. 
     FIG. 3 is a block diagram of an optical disc recording and reproducing apparatus according to the preferred embodiment of the present invention. 
     FIG. 4 shows output waveforms corresponding to parts of the optical disc recording and reproducing apparatus in FIG.  3 . 
     FIG. 5 provides a detailed illustration of the data format of the frame video data shown in FIG.  4 . 
     FIG. 6 is a flow chart for explaining a multi-rate recording method according to the first embodiment of the present invention. 
     FIG. 7 is a flow chart for explaining a multi-rate recording method according to the second embodiment of the present invention. 
     FIG. 8 is a diagram for explaining a recording start position of the optical disc and a pattern of the frame data pit train according to the multi-rate recording method in the second embodiment of the invention. 
     FIG. 9 is a flow chart for explaining a multi-rate recording method according to the third embodiment of the present invention. 
     FIG. 10 is a diagram for explaining a recording start position of the optical disc and a pattern of the frame data pit train according to the multi-rate recording method in the third embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 3, there is shown an optical disc recording and reproducing apparatus according to the preferred embodiment of the present invention which comprises a transfer rate detector  10  and a buffer  12  commonly connected to an input/output line  11 . The input/output line  11  is connected to a data source (not shown) in order to transfer the video data VDS from the data source into the buffer  12  or to transfer the video data VDS from the buffer  12  into the data source. This video data VDS is transferred in the shape of a frame unit, as shown in FIG. 5 according to the frame dividing signal FDS. The frame video data consists of only data portions including information about pixels, or of both identification code portions including information about a transfer rate and data portions including information about pixels. The video data is classified into high resolution video data HVD and normal video data NVD in accordance with the number of pixels. The high resolution video data HVD is formed by formatting an array of 1024×1024 pixel data to one frame and making a moving picture compression of the formatted frame video data, which are transferred at a transfer rate of 10 Mbps. The normal video data NVD is formed by formatting an array of 325×525 pixel data to one frame, which is transferred at a transfer rate of 5 Mbps. The transfer rate detector  10  detects a transfer rate value of video data VDS from the identification portion included in the video data VDS from the input/output line  11 . The transfer rate value is detected by the transfer rate detector  10  only when the identification code portion is included in the video data VDS. The buffer  12  temporarily stores the video data VDS inputted from the input/output line  11  and the reproduced video data to be transferred toward the input/output line  11 . The buffer  12  has enough storage capacity to store two frame video data. 
     The optical disc recording and reproducing apparatus further comprises a key input portion  14  for sending an instruction assigned by a user via the first node  13  to microcomputer  16 , a clock frequency change portion  18  connected to the microcomputer  16 , and a rotational velocity control portion  20 . The key input portion  14  inputs recording, reproducing and retrieval instructions from a user as well as virtual addresses intended to record and reproduce, and supplies the inputted instructions and addresses to the microcomputer  16  via the first node  13 . Also, during recording, the key input portion  14  inputs a transfer rate value related to the data to be recorded, and supplies the transfer rate value to the microcomputer  16 . For this purpose, the key input portion  14  includes key switches (not shown) and/or a keyboard. 
     In the recording mode, the microcomputer  16  generates clock frequency data and rotational velocity data in accordance with a transfer rate value inputted via the second node  15  from the transfer rate detector  10 . Also, the microcomputer  16  generates the clock frequency data and the rotational velocity data corresponding to the transfer rate value from the key input portion  14  when the transfer rate value is not detected by the transfer rate detector  10 . The clock frequency data is supplied to the clock frequency change portion  18  via the third node  17 , and the rotational velocity data is supplied to the rotation velocity control portion  20  via the fourth node  19 . 
     The clock frequency change portion  18  varies the frequency of the clock signal generated at a clock generator  22  in accordance with a logic value of the clock frequency data applied via the third node  17  from the microcomputer  16 . The clock generator  22  generates the first clock signal FCS or the second clock signal SCS under control of the clock frequency change portion  18 . The first clock signal FCS is generated when the video data VDS is inputted to the input/output line  11  at a transfer rate of 5 Mbps, which has a frequency of 5 MHz. For this, the clock generator  2  includes a voltage controlled oscillator (not shown), and the clock frequency change portion  18  includes a decoder (not shown) such as a digital-to-analog converter. 
     On the other hand, the rotational velocity control portion  20  rotates a spindle motor  14  at a speed corresponding to the rotational velocity data inputted via the fourth node  19  from the microcomputer  16 . For example, the rotational velocity control portion  20 , like DSV in FIG. 4, rotates the spindle motor  24  at a speed of 100 rps when the high resolution video data HVD of 10 Mbps is inputted to the input/output line  11 . By contrast, rotational velocity control portion  20  rotates the spindle motor  24  at a speed of 50 rps when the normal video data NVD is inputted to the input/output line  11 . In response to rotation of the spindle motor  24 , the optical disc D is subject to rotate at a same velocity as the spindle motor  24 . 
     Furthermore, the optical disc recording and reproducing apparatus comprises a formatter  26  connected in serial with the buffer  12 , a digital signal processor  28  (DSP hereinafter), and a channel modem  30 . The formatter  26  formats the video data VDS from the buffer  12  into a pattern required by an optical disc D and, at the same time, applies the formatted video data to the buffer  12 . Also, the formatter  26  reversely formats the reproduced video data from the DSP  28  into the original pattern and applies the reversely formatted video data to the buffer  12 . The formatter  26  inputs the video data VDS stored in the buffer  12  at a rate of 10 Mbps or 5 Mbps in accordance with the clock signal from the clock generator  22 . Specifically, the formatter  26  inputs the video data VDS from the buffer  12  at a rate of 10 Mbps when the first clock signal FCS is applied from the clock generator  22 , while it inputs the video data VDS from the buffer  12  at a rate of 5 Mbps when the second clock signal SCS is applied from the clock generator  22 . 
     Under control of the microcomputer  16 , DSP  28  converts the video data from the formatter  26  into the form of a data bit stream or restores the video data from the reproduced data bit stream. Specifically, in the recording mode, DSP  28  detects a synchronous pattern and an address from a support signal demodulated from the channel modem  30 , and supplies the detected synchronous pattern and address to the microcomputer  16 . Also, DSP  28  converts the formatted video data from the formatter  26  into the form of a data bit stream. This data bit stream is to be added by an error correction code, an address and a synchronous pattern besides the video data, which is supplied to the channel modem  30 . The support signal is a signal which is preformatted on the track in the optical disc, and includes a synchronous pattern indicating the rotational velocity of the optical disc D and an address indicating the physical position of the storage area. 
     In the reproduction mode, DSP  28  separates video data, an error correction code, a synchronous pattern and an address from the reproduced data bit stream from the channel modem  30 , and corrects an error generated in the video data by the error correction code. Also, DSP  28  applies the error corrected video data to the formatter  26  and supplies the synchronous pattern and the address to the microcomputer  16 . 
     In the recording mode, the channel modem  30  channel-codes a data bit stream to be recorded from the DSP  28 , and channel-decodes a support signal reproduced from the optical disc D and received through reproducing portion  36  and optical pick-up  32 . The channel-decoded support signal is applied to the DSP  28 . In the reproduction mode, the channel modem  30  channel-decodes a data bit stream reproduced from the optical disc and supplies the channel-decoded data bit stream to DSP  28 . 
     The optical disc recording and reproducing apparatus further comprises an optical pick-up device  32  for accessing the optical disc D optically, and a recording portion  34  and a reproducing portion  36 , which are connected between the channel modem  30  and the optical pick-up device  32 . Under control of the microcomputer  16 , the optical pick-up device  32  moves back and forth in a radial direction of the optical disc to record data on the track in the optical disc D or pick-up information recorded on the track in the optical disc D. For this purpose, the optical pick-up device  32  irradiates a relatively large energy of light beam onto the surface of the optical disc D in the recording mode. By contrast, it radiates a relatively small energy of light beam onto the surface of the optical disc D in the reproduction mode. 
     The recording portion  34  allows a light beam irradiated on the track in the optical disc D to be switched by controlling the optical pick-up device  32  in accordance with the data bit stream from the channel modem  30 . As a result, a data pit train WDP indicating “1” or “0” in accordance with the data bit stream is formed in such a manner that a spiral track is shaped in the optical disc D. 
     In this data pit train WDP, HVDP represents the data pit train relative to one frame of high resolution video data and NVDP does the data pit train relative to one frame of normal video data. 
     The reproducing portion  36  processes a high frequency signal from the optical pick-up device  32  to generate a support signal and a data bit stream from the high frequency signal. The support signal and the data bit stream generated at the reproducing portion  36  are supplied to the channel modem  30 . 
     FIG. 6 is a flow chart for explaining a multi-rate recording method according to the first embodiment of the present invention. The process in FIG. 6 is performed by the microcomputer  16  (shown in FIG.  3 ). 
     Referring now to FIG. 6, in step  40 , the microcomputer  16  waits until a record instruction is inputted from the key input portion  14 . If the record instruction is inputted in step  40 , then the microcomputer  16  sets a record mode flag assigned in a part of register therein, and inputs a transfer rate value of video data from the transfer rate detector  10  (step  42 ). 
     In step  44 , the microcomputer  16  decides, based on the transfer rate value, if the video data VDS on the input/output line is high resolution video data HVD or normal video data NVD. When the transfer rate value is 10 Mbps, the microcomputer  16  decides that the high resolution video data HVD is being applied to the input/output line  11 . When the transfer rate value is 5 Mbps, the microcomputer  16  decides that the normal video data NVD is being applied to the input/output line  11 . 
     If it is decided that the high resolution video data HVD is applied to the input/output line  11  in step  44 , then the microcomputer  16  allows the clock generator  22  to generate the first clock signal FCS of 10 MHz by controlling the clock generator  22  via the clock frequency change portion  18  (step  46 ). At this time, the formatter  26  inputs the high resolution video data HVD in the buffer  12  at a rate of 10 Mbps, by means of the first clock signal from the clock generator  22 . As a result, the high resolution video data HVD recorded on the optical disc D is transferred at a rate of 10 Mbps by way of the formatter  26 , the DSP  28 , the channel modem  30 , the recording portion  34  and the optical pick-up device  32 . Subsequently, the microcomputer  16  allows the rotational velocity controller  20  to rotate the spindle motor  24  at a speed of 100 rps by controlling the rotational velocity controller  20  (step  48 ). In response to a rotation of the spindle motor  24  at the speed of 100 rps, the optical disc D also is subject to rotate at a speed of 100 rps. 
     On the other hand, if it is decided that the normal video data NVD is applied to the input/output line  11  in step  44 , then the microcomputer  16  allows the clock generator  22  to generate the second clock signal SCS of 5 MHz by controlling the clock generator  22  via the clock frequency change portion  18  (step  50 ). At this time, the formatter  26  inputs the normal video data NVD in the buffer  12  at a rate of 5 Mbps, by means of the second clock signal from the clock generator  22 . As a result, the normal video data NVD recorded on the optical disc D is transferred at a rate of 5 Mbps by way of the formatter  26 , the DSP  28 , the channel modem  30 , the recording portion  34  and the optical pick-up device  32 . Subsequently, the microcomputer  16  allows the rotational velocity controller  20  to rotate the spindle motor  24  at a speed of 50 rps by controlling the rotational velocity controller  20  (step  52 ). In response to a rotation of the spindle motor  24  at the speed of 50 rps, the optical disc D also is subject to rotate at a speed of 50 rps. 
     After performing the above steps  46 - 48  or  50 - 52 , the microcomputer  16  controls the optical pick-up device  32  by allowing the optical pick-up device  32  to record the data bit stream from the channel modem  30  on the optical disc D (step  54 ). As a result, an appropriate frame data pit train, such as HVDP or NVDP in FIG. 4, is generated in the optical disc D. Herein, HVDP represents a data pit train relative to one frame of high resolution video data, and NVDP represents a data pit train relative to one frame of normal video data. 
     FIG. 7 is a flow chart for explaining a multi-rate recording method according to the second embodiment of the present invention. The process in FIG. 7 is performed by the microcomputer  16  (shown in FIG.  3 ). 
     Referring now to FIG. 7, in step  56 , the microcomputer  16  waits until a record instruction is inputted from the key input portion  14 . If the record instruction is inputted in step  56 , then the microcomputer  16  sets a record mode flag assigned in a part of register therein, and inputs a transfer rate value of video data from the transfer rate detector  10  (step  58 ). 
     In step  60 , the microcomputer  16  decides, based on the transfer rate value, if the video data VDS on the input/output line  11  is high resolution video data HVD or normal video data NVD. When the transfer rate value is 10 Mbps, the microcomputer  16  decides that the high resolution video data HVD is being applied to the input/output line  11 . When the transfer rate value is 5 Mbps the microcomputer  16  decides that the normal video data NVD is being applied to the input/output line  11 . 
     If it is decided that the high resolution video data HVD is applied to the input/output line  11  in step  60 , then the microcomputer  16  sets the first recording speed mode flag assigned in a part of register therein, specifying that the data is to be recorded at a rate of 10 Mbps (step  62 ). On the other hand, if it is decided that the normal video data NVD is applied to the input/output line  11  in step  60 , then the microcomputer  16  sets the second recording speed mode flag assigned in a part of register therein instead of the first recording speed mode flag, specifying that the data is to be recorded at a rate of 5 Mbps (step  64 ). 
     After performing the above step  62  or  64 , the microcomputer  16  controls the spindle motor  24  via the rotational velocity controller  20  such that the spindle motor  24  rotates at a rate corresponding to the recording speed mode set in step  62  or  64 . At the same time, the microcomputer  16  retrieves a table on the lead-in area of optical disc D inputted by way of the optical pick-up device  32 , the recording portion  36 , channel modem  30  and the DSP  28 , and decides whether there are a previously recorded video data or not (step  66 ). When a start address and an end address exist in the table, the microcomputer  16  decides that previously recorded data exists in the optical disc D. Otherwise, when an start address and an end address data do not exist in the retrieved table, the microcomputer  16  decides that previously recorded data does not exist in the optical disc D. The spindle motor  24  rotates at a rate of 100 rps when the first recording speed mode is set in step  62  while rotating at a rate of 50 rps when the second recording speed mode is set in step  64 . 
     In step  66 , if there is data recorded previously in the optical disc, then the microcomputer  16  compares a logical value of the recording speed mode flag with that of the transfer speed mode flag on the table, and decides whether the recording speed mode of the previously recorded data is identical to that of the data to be recorded (step  68 ). If the logical value of the recording speed mode flag is not identical to that of the transfer speed mode flag, it is judged that the recording speed mode of the previously recorded data is different from that of the video data to be recorded. 
     When the recording speed mode of the previously recorded data is different from that of the video data to be recorded in step  68 , the microcomputer  16  allows the spindle motor  24  to be rotated at a speed corresponding to the recording speed mode of the previously recorded data by controlling the spindle motor  24  via the rotation velocity controller  20 . The final portion of the recording region is then sought based on whether data is inputted from the DSP  28 , making a track jump of the optical pick-up device  32  if necessary (step  70 ). At this time, if the first recording speed mode was set in step  62 , the spindle motor  24  rotates at a speed of 50 rps; whereas if the second recording speed mode was set in step  64 , the spindle motor  24  rotates at a speed of 100 rps. Further, the microcomputer  16  allows the clock generator  22  to supply a clock signal to the formatter  26  having a frequency corresponding to the recording speed mode by controlling the clock generator  22  via the clock frequency change portion  18  (step  72 ). For example, when the first recording speed mode is set in step  62 , the clock generator  22  applies the first clock signal FCS to the formatter  26 . Accordingly, the high resolution video data on the input/output line  11  is delivered to the optical pick-up device  32  at a transfer rate of 10 Mbps via the buffer  12 , the formatter  26 , the DSP  28 , the channel modem  30  and the recording portion  34  in turn. Otherwise, when the second recording speed mode is set in step  64 , the clock generator  22  applies the second clock signal SCS to the formatter  26 . Thus, the normal video data NVD on the input/output line  11  is transferred at a transfer rate of 5 Mbps via the buffer  12 , the formatter  26 , the DSP  28 , the channel modem  30  and the recording portion  34  in turn into the optical pick-up device  32 . The microcomputer  16  allows the spindle motor  24  to rotate at a speed corresponding to the recording speed mode set in step  62  or  64  by controlling the spindle motor  24  via the rotation velocity controller  20  (step  74 ), and then it waits until the rotation speed of the spindle motor  24  maintains a speed corresponding to the recording speed mode set in step  62  or  64  stabbly (step  76 ). 
     On the other hand, if the recording speed mode of the previously recorded data is identical to that of the video data to be recorded in step  68 , then the microcomputer  16  seeks the final portion of the previously recorded region based on whether data is inputted from the DSP  28 , making a track jump of the optical pick-up device  32  if necessary (step  78 ). Further, the microcomputer  16  allows the clock generator  22  to supply a clock signal having a frequency corresponding to the recording speed mode with the formatter  26  (step  80 ). 
     Moreover, if the optical disc D does not appear to contain previously recorded data in step  66 , then the microcomputer  16  allows the clock generator  22  to supply a clock signal having a frequency corresponding to the recording speed mode to formatter  26  by controlling the clock generator  22  via the clock frequency change portion  18  (step  118 ). 
     After performing the above step  76 ,  80  or  118 , the microcomputer  16  allows the optical pick-up device  32  to irradiate a relatively large energy of light beam switched under control of the recording portion  34  on the surface of the optical disc D by controlling the optical pick-up device  32 , such that the video data VDS is recorded on the optical disc D (step  84 ). 
     FIG. 8 explains a recorded state of the high resolution video data HVD in the first recording speed mode and the normal video data NVD in the second recording speed mode, when those video data are recorded on the optical disc D by the second embodiment of the present invention. In FIG. 8, a speed DSV of the spindle motor  22  remains at 100 rps until first time t 1 , at which time the final portion of the high resolution video data HVD in the first recording speed mode recorded on the optical disc D is retrieved. At time t 1 , the optical pick-up device  32  is disposed on the first position p 1 , which is the final portion of the high resolution video data in the first recording speed mode. 
     Beginning at the first time t 1 , the rotation speed of the spindle motor  22  decreases slowly until a speed of 50 rps is achieved at second time t 2 . At the second time t 2 , the optical pick-up device  32  moves from the first position p 1 , which is the final portion of the high resolution video data in the first recording speed mode, to the second position p 2  spaced by a certain distance s e  from the first position p 1 . The optical pick-up device  32  records the normal video data NVD in the second recording speed mode from the second position p 2  on the track. Thus, a non-recorded region having a length equal to the movement distance s e  occurs during a rotation speed stabilization period t 1 -t 2  of the spindle motor  22  between the high resolution video data HVD in the first recording speed mode and the normal video data NVD in the second recording speed mode. 
     FIG. 9 is a flow chart for explaining a multi-rate recording method according to the third embodiment of the present invention. The process in FIG. 9 is performed by the microcomputer  16  (shown in FIG.  3 ). 
     Referring now to FIG. 9, in step  86 , the microcomputer  16  waits until a record instruction is inputted from the key input portion  14 . If the record instruction is inputted in step  86 , then the microcomputer  16  sets a record mode flag assigned in a part of register therein, and inputs a transfer rate value of video data from the transfer rate detector  10  (step  88 ). 
     In step  90 , the microcomputer  16  decides based on the transfer rate value whether the video data VDS on the input/output line  11  corresponds to high resolution video data HVD or normal video data NVD. When the transfer rate value is 10 Mbps, the microcomputer  16  decides that the high resolution video data HVD is being applied to the input/output line  11 . When the transfer rate value is 5 Mbps, the microcomputer  16  decides that the normal video data NVD is being applied to the input/output line  11 . If it is decided that the high resolution video data HVD is applied to the input/output line  11  in step  90 , then the microcomputer  16  sets the first recording speed mode flag assigned in a part of register therein, specifying that the data is to be recorded at a rate of 10 Mbps (step  92 ). On the other hand, if it is decided that the normal video data NVD is applied to the input/output line  11  in step  90 , then the microcomputer  16  sets the second recording speed mode flag assigned in a part of register therein instead of the first recording speed mode flag, specifying that the data is to be recorded at a rate of 5 Mbps (step  94 ). 
     After performing the above step  92  or  94 , the microcomputer  16  controls the spindle motor  24  via the rotational velocity controller  20  such that the spindle motor  24  rotates at a rate corresponding to the recording speed mode set in step  92  or  94 . At the same time, the microcomputer  16  retrieves a table on the lead-in area of optical disc D inputted by way of the optical pick-up device  32 , the recording portion  36 , channel modem  30  and the DSP  28 , and decides whether there exists previously recorded data or not (step  96 ). When a start address and an end address exist in the table, the microcomputer  16  decides that the data recorded previously exists in the optical disc D. Otherwise, when an start address and an end address do not exist in the table, the microcomputer  16  decides that previously recorded data does not exist in the optical disc D. The spindle motor  24  rotates at a rate of 100 rps when the first recording speed mode is set in step  92  while rotating at a rate of 50 rps when the second recording speed mode is set in step  94 . 
     In step  96 , if there is data recorded previously in the optical disc, then the microcomputer  16  compares a logical value of the recording speed mode flag with that of the transfer speed mode flag on the table, and decides whether the recording speed mode of the previously recorded data is identical to that of the data to be recorded (step  98 ). If the logical value of the transfer speed mode flag is not identical to that of the recording speed mode flag, it is judged that the recording speed mode of the previously recorded data is different from that of the video data to be recorded. 
     When the recording speed mode of the previously recorded data is different from that of the video data to be recorded in step  98 , the microcomputer  16  allows the spindle motor  24  to be rotated at a speed corresponding to the recording speed mode of the previously recorded data by controlling the spindle motor  24  via the rotation velocity controller  20 . The final portion of the recording region is then sought based on whether data is inputted from the DSP  28 , with making a track jump of the optical pick-up device  32  if necessary (step  100 ). At this time, if the first recording speed mode was set in step  92 , the spindle motor  24  rotates at a speed of 50 rps; whereas if the second recording speed mode was set in step  94 , the spindle motor  24  rotates at a speed of 100 rps. Further, the microcomputer  16  inputs an address relative to the final portion of the previously recorded region from the DSP  28  (step  102 ) , and thereafter allows the clock generator  22  to supply a clock signal having a frequency corresponding to the recording speed mode with the formatter  26  by controlling the clock generator  22  via the clock frequency change portion  18  (step  104 ). For example, when the first recording speed mode is set in step  92 , the clock generator  22  applies the first clock signal FCS to the formatter  26 . Accordingly, the high resolution video data on the input/output line  11  is delivered to the optical pick-up device  32  at a transfer rate of 10 Mbps via the buffer  12 , the formatter  26 , the DSP  28 , the channel modem  30  and the recording portion  34 . Otherwise, when the second recording speed mode is set in step  94 , the clock generator  22  applies the second clock signal SCS to the formatter  26 . Thus, the normal video data NVD on the input/output line  11  is transferred into the optical pick-up device  32  at a transfer rate of 5 Mbps via the buffer  12 , the formatter  26 , the DSP  28 , the channel modem  30  and the recording portion  34 . The microcomputer  16  allows the spindle motor  24  to rotate at a speed corresponding to the recording speed mode set in step  92  or  94  by controlling the spindle motor  24  via the rotation velocity controller  20  (step  106 ), and then it waits until the rotation speed of the spindle motor  24  maintains a speed corresponding to the recording speed mode set in step  92  or  94  stabbly (step  108 ). 
     In step  108 , when the rotation speed of the spindle motor  24  arrives at a speed corresponding to the recording speed mode set in step  92  or  94 , the microcomputer  16  moves the optical pick-up device  32  into the previous track of the optical disc D (step  110 ). Next, the microcomputer  16  waits until an address relative to the final portion of the recording region from the DSP  28  (step  112 ). 
     On the other hand, if the recording speed mode of the previously recorded data is identical to that of the video data to be recorded in step  98 , then the microcomputer  16  seeks the final portion of the previously recorded region based on whether data is inputted from the DSP  28 , making a track jump of the optical pick-up device  32  if necessary (step  114 ). Further, the microcomputer  16  allows the clock generator  22  to supply a clock signal having a frequency corresponding to the recording speed mode with the formatter  26  (step  116 ). 
     Moreover, if the optical disc D does not appear to contain previously recorded data in step  96 , then the microcomputer  16  allows the clock generator  22  to supply a clock signal having a frequency corresponding to the recording speed mode to formatter  26  by controlling the clock generator  22  via the clock frequency change portion  18  (step  118 ). 
     After performing the above step  112 ,  116  or  118 , the microcomputer  16  allows the optical pick-up device  32  to irradiate a relatively large energy of light beam, switched under control of the recording portion  34 , on the surface of the optical disc D by controlling the optical pick-up device  32 . As such, the video data VDS is recorded on the optical disc D (step  120 ). 
     FIG. 10 explains a recorded state of the high resolution video data HVD in the first recording speed mode and the normal video data NVD in the second recording speed mode, when those video data are recorded on the optical disc D by the third embodiment of the present invention. In FIG. 10, a speed DSV of the spindle motor  22  remains at 100 rps until first time t 1 , when the final portion of the high resolution video data HVD in the first recording speed mode recorded on the optical disc D is retrieved. At time t 1 , the optical pick-up device  32  is disposed on the position p 2 , which is the position of the final high resolution video data recorded in the first recording speed mode. 
     Beginning at the first time ti, the rotation speed DSV of the spindle motor  22  decreases slowly until a speed of 50 rps is achieved at second time t 2 . Between first time t 1  and second time t 2 , the optical pick-up device  32  is moved from the position p 2 , which corresponds to the final position of the high resolution video data in the first recording speed mode, to the position p 1  spaced by a certain distance s e  from the position p 2 . Therefore, to avoid a null space between positions p 1  and p 2 , the optical pick-up device  31  is moved backward by a distance s e  corresponding to the movement experienced during the change in spindle motor speed. In this manner, the optical pick-up device  31  is returned from position p 2  to position p 1 . 
     If the optical pick-up device  32  delays recording the normal video data NVD in the second recording speed mode until the third time t 3 , the optical pick-up device  32  must also be moved by a certain distance s b  corresponding to the movement ordinarily experienced by the optical pick-up device  32  during that time delay, namely a track jump from the position p 2  on the track to the position p 3  preceding positions p 1  and p 2 . It is also possible to perform a single jump as shown in FIG. 10, corresponding to a combination of distances s c  and S b . 
     In the manner described above, in the second recording speed mode, the normal video data NVD is recorded after the final portion of the high resolution video data HVD such that a non-recorded null space region is avoided. 
     According to this second embodiment, null spaces can be avoided with a single jump, regardless of whether delays are experienced for speed changes. For instance, when delays are experienced for speed changes, the process is performed as described above. When such delays are not experienced, the same process is performed, but the jump corresponding to distance s e  is not necessary. 
     That is, in either case, to avoid null data regions, the present invention performs a reverse jump and a recording operation when the optical disc is rotated at the speed corresponding to the transfer rate of the high resolution video data which is higher than the normal video data. In other words, the present invention initially allows the rotation speed of the optical disc to be maintained at the speed corresponding to the transfer rate of the high resolution video data. The transfer rate of input video data to be recorded is detected using a transfer speed detector  10  (shown in FIG.  3 ). The input video data is identified as any one of the normal and high resolution video data according to the transfer rate of the input video data. If the transfer rate detected by the input  10  is the first transfer rate (i.e., the input video data is the normal video data), the pick-up is reversely jumped each time a constant amount of normal video data have been recorded on the optical disc. 
     In greater detail, the pick-up is positioned at the end point of previously recorded data (or the start point of the data area if no data has been previously recorded), and a constant amount of the normal video data is recorded on an otherwise null data region following the end point of the previously recorded data area by a constant distance. 
     After the constant amount of the normal video data has been recorded on the otherwise null data region, an amount of normal video data to be recorded next must be prepared before further recording can be performed. To provide time for the preparation of the this data without creating a null data region, the pick-up jumps reversely at least one track. This is demonstrated by FIG. 10, where a constant amount of normal video data is recorded on the otherwise null data region between positions p 1  and p 2 , and the pick-up thereafter jumps reversely to position p 3  to provide time for the preparation of additional normal video data to be recorded after position p 1 . The jump can be greater than the constant amount of normal video data being recorded, as shown, or less. While the pick-up moves from the new position (e.g., p 3 ) to a new start point (e.g., p 2 ) of the null data area, the next normal video data to be recorded is pre pared. The prepared normal video data is then recorded on the otherwise null data region following the new start point of the null data area. 
     In this manner, the present invention successively and repeatedly performs the reverse jumping and the recording operations when the normal video data having a low transfer data is recorded on the optical disc rotating at the speed corresponding to a high transfer rate, thereby preventing the generation of the null data on the optical disc. As a result, the present invention effectively uses the recording capacity of the optical disc. 
     As described above, according to a multi-rate recording method and apparatus of the present invention, the rotation velocity of the optical disc and the processing speed of data can be controlled in accordance with the transfer rate of the data to be recorded such that the unnecessary data is not recorded on the optical disc. As a result, the multi-rate recording method and apparatus according to the present invention provides an advantage in that it can improve recording efficiency of optical disc and the recording time thereof dramatically. 
     Although the present invention has been described by the preferred embodiments illustrated in drawings hereinbefore, it is apparent from the above description to those ordinarily skilled in the art that various changes and modifications of the invention are possible without departing from the spirit thereof. For instance, it may be suggested that the buffer shown in FIG. 3 is disposed between the formatter  26  and the DSP  28  or between the DSP  28  or the channel modem  30  to supply the clock signal generated at the clock generator  22  with the DSP  28  or the channel modem  30 , thereby controlling the processing speed of video data. Also, while the present invention has been described to be limited to the video data, it is to be understood that it may be applied to other data such as text data and packet data, etc. Accordingly, the scope of the invention should be determined not by the embodiments illustrated and described, but by the appended claims and their equivalents.