PATENT ABSTRACT
An input signal is quantized into a quantization-resultant signal. The quantization-resultant signal is compressed into a compression-resultant signal. The compression-resultant signal is formatted into a formatting-resultant signal corresponding to a predetermined format for a digital recording disc. The formatting-resultant signal includes segments corresponding to user data areas prescribed in the predetermined format. The compression-resultant signal is placed in the segments of the formatting-resultant signal. The formatting-resultant signal is encoded into an encoding-resultant signal of a CD format. The encoding-resultant signal is recorded on a recording medium.

PATENT DESCRIPTION
CROSS REFERENCE TO RELATED APPLICATION 
   This application is a Continuation of U.S. application Ser. No. 10/795,297, filed Mar. 9, 2004; which is a Divisional of U.S. application Ser. No. 09/985,048, filed Nov. 1, 2001, which is a Divisional of U.S. application Ser. No. 09/655,046, filed Sep. 5, 2000, now U.S. Pat. No. 6,393,203, issued May 21, 2002, which is a Division of U.S. application Ser. No. 08/887,216, filed Jul. 2, 1997, now U.S. Pat. No. 6,151,442, issued Nov. 21, 2000, and for which priority is claimed under 35 U.S.C. §120; and this application claims priority to Application No. 8-197000 filed in Japan on Jul. 8, 1996, under 35 U.S.C. §119; the entire contents of all are hereby incorporated by reference. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to a signal compressing apparatus such as an audio signal compressing apparatus. Also, this invention relates to a signal recording apparatus such as an audio signal recording apparatus. Furthermore, this invention relates to a recording medium. In addition, this invention relates to an apparatus for an optical disc such as a CD-DA (Compact Disc Digital Audio), a CD-ROM (Compact Disc Read Only Memory), a video-CD, a DVD (Digital Video Disc), a DVD-ROM (Digital Video Disc Read Only Memory), a DVD-WO (Digital Video Disc Write Once), or a DVD-RAM (Digital Video Disc Random Access Memory). 
   2. Description of the Related Art 
   The CD (Compact Disc) standards prescribe that the sampling frequency fs should be 44.1 kHz, and the quantization bit number should be 16. There are optical recording discs on which digital signals representing audio information, digital signals representing video information, or digital signals representing both audio information and video information are recorded. Examples of such optical recording discs are a CD-DA (Compact Disc Digital Audio), a CD-ROM (Compact Disc Read Only Memory), a video-CD, and a DVD (Digital Video Disc). 
   Audio data conforming to the CD-DA standards can not be recorded as audio data of the CD-ROM format for the following reason. The CD-ROM format has headers containing sync information, address information, and mode information. Accordingly, a recording capacity of a CD-ROM which can be used for audio information is smaller than the audio-information recording capacity of a CD-DA. 
   SUMMARY OF THE INVENTION 
   It is a first object of this invention to provide an improved signal compressing apparatus. 
   It is a second object of this invention to provide an improved signal recording apparatus. 
   It is a third object of this invention to provide an improved recording medium. 
   It is a fourth object of this invention to provide an improved apparatus for an optical disc. 
   A first aspect of this invention provides a signal recording apparatus comprising means for quantizing an input signal into a quantization-resultant signal; means for compressing the quantization-resultant signal into a compression-resultant signal; means for formatting the compression-resultant signal into a formatting-resultant signal corresponding to a predetermined format for a digital recording discs the formatting-resultant signal including segments corresponding to user data areas prescribed in the predetermined format, the compression-resultant signal being placed in the segments of the formatting-resultant signal; means for encoding the formatting-resultant signal into an encoding-resultant signal of a CD format; and means for recording the encoding-resultant signal on a recording medium. 
   A second aspect of this invention is based on the first aspect thereof, and provides a signal recording apparatus wherein the input signal comprises an audio signal. 
   A third aspect of this invention is based on the first aspect thereof, and provides a signal recording apparatus wherein the predetermined format for the digital recording disc is equal to a predetermined format for a CD-ROM. 
   A fourth aspect of this invention is based on the first aspect thereof, and provides a signal recording apparatus wherein the predetermined format for the digital recording disc is equal to a predetermined format for a DVD. 
   A fifth aspect of this invention is based on the first aspect thereof, and provides a signal recording apparatus wherein the compressing means comprises means for subjecting the quantization-resultant signal to orthogonal transform. 
   A sixth aspect of this invention is based on the fifth aspect thereof, and provides a signal recording apparatus wherein the compressing means comprises means for subjecting the quantization-resultant signal to a Huffman encoding process. 
   A seventh aspect of this invention is based on the first aspect thereof, and provides a signal recording apparatus wherein the compressing means comprises means for dividing the quantization-resultant signal into components corresponding to divided frequency bands respectively, and means for compressing the components according to frequency-band-dependent compression characteristics depending on a predetermined auditory sensation model. 
   An eighth aspect of this invention provides a signal compressing apparatus comprising means for quantizing an input signal into a quantization-resultant signal; means for compressing the quantization-resultant signal into a compression-resultant signal; and means for formatting the compression-resultant signal into a formatting-resultant signal corresponding to a predetermined format for a digital recording disc, the formatting-resultant signal including segments corresponding to user data areas prescribed in the predetermined format, the compression-resultant signal being placed in the segments of the formatting-resultant signal. 
   A ninth aspect of this invention is based on the eighth aspect thereof, and provides a signal compressing apparatus wherein the input signal comprises an audio signal. 
   A tenth aspect of this invention is based on the eighth aspect thereof, and provides a signal compressing apparatus wherein the predetermined format for the digital recording disc is equal to a predetermined format for a CD-ROM. 
   An eleventh aspect of this invention is based on the eighth aspect thereof, and provides a signal compressing apparatus wherein the predetermined format for the digital recording disc is equal to a predetermined format for a DVD. 
   A twelfth aspect of this invention is based on the eighth aspect thereof, and provides a signal compressing apparatus wherein the compressing means comprises means for subjecting the quantization-resultant signal to orthogonal transform. 
   A thirteenth aspect of this invention is based on the twelfth aspect thereof, and provides a signal compressing apparatus wherein the compressing means comprises means for subjecting the quantization-resultant signal to a Huffman encoding process. 
   A fourteenth aspect of this invention is based on the eighth aspect thereof, and provides a signal compressing apparatus wherein the compressing means comprises means for dividing the quantization-resultant signal into components corresponding to divided frequency bands respectively, and means for compressing the components according to frequency-band-dependent compression characteristics depending on a predetermined auditory sensation model. 
   A fifteenth aspect of this invention provides a recording medium storing an encoding-resultant signal which is recorded on the recording medium by the steps of quantizing an input signal into a quantization-resultant signal; compressing the quantization-resultant signal into a compression-resultant signal; formatting the compression-resultant signal into a formatting-resultant signal corresponding to a predetermined format for a digital recording disc, the formatting-resultant signal including segments corresponding to user data areas prescribed in the predetermined format, the compression-resultant signal being placed in the segments of the formatting-resultant signal; encoding the formatting-resultant signal into an encoding-resultant signal of a CD format; and recording the encoding-resultant signal on the recording medium. 
   A sixteenth aspect of this invention provides an apparatus for an optical disc, comprising a CD-DA decoder; a CD-ROM decoder; a signal expansion decoder; means for reading out a signal from the optical disc; means for deciding which of a CD-DA, a CD-ROM, and a CD-ROM-audio the optical disc agrees with; means for, when the optical disc agrees with a CD-DA, selecting the CD-DA decoder from among the CD-DA decoder, the CD-ROM decoder, and the signal expansion decoder and using the CD-DA decoder to process the signal read out from the optical disc into a recovered signal; means for, when the optical disc agrees with a CD-ROM, selecting the CD-DA decoder and the CD-ROM decoder from among the CD-DA decoder, the CD-ROM decoder, and the signal expansion decoder and using the CD-DA decoder and the CD-ROM decoder to process the signal read out from the optical disc into a recovered signal; and means for, when the optical disc agrees with a CD-ROM-audio, using the CD-DA decoder, the CD-ROM decoder, and the signal expansion decoder to process the signal read out from the optical disc into a recovered signal. 
   A seventeenth aspect of this invention provides an apparatus for an optical disc, comprising a CD-DA decoder; a CD-ROM decoder; a signal expansion decoder; an MPEG decoder; means for reading out a signal from the optical disc; means for deciding which of a CD-DA, a CD-ROM-audio, and a video-CD the optical disc agrees with; means for, when the optical disc agrees with a CD-DA, selecting the CD-DA decoder from among the CD-DA decoder, the CD-ROM decoder, the signal expansion decoder, and the MPEG decoder and using the CD-DA decoder to process the signal read out from the optical disc into a recovered signal; means for, when the optical disc agrees with a CD-ROM-audio, selecting the CD-DA decoder, the CD-ROM decoder, and the signal expansion decoder from among the CD-DA decoder, the CD-ROM decoder, the signal expansion decoder, and the MPEG decoder and using the CD-DA decoder, the CD-ROM decoder, and the signal expansion decoder to process the signal read out from the optical disc into a recovered signal; and means for, when the optical disc agrees with a video-CD, selecting the CD-DA decoder, the CD-ROM decoder, and the MPEG from among the CD-DA decoder, the CD-ROM decoder, the signal expansion decoder, and the MPEG decoder and using the CD-DA decoder, the CD-ROM decoder, and the MPEG decoder to process the signal read out from the optical disc into a recovered signal. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a block diagram of a signal compressing apparatus according to a first embodiment of this invention. 
       FIG. 2  is a diagram of a first format of a 1-sector-corresponding segment of a digital signal generated by a CD-ROM encoding circuit in  FIG. 1 . 
       FIG. 3  is a diagram of a second format of a 1-sector-corresponding segment of a digital signal generated by the CD-ROM encoding circuit in  FIG. 1 . 
       FIG. 4  is a diagram of a format of a 1-pack-corresponding segment of a digital signal generated by a DVD encoding circuit in  FIG. 1 . 
       FIG. 5  is a diagram of a drive apparatus and a CD-WO (a compact disc write once). 
       FIG. 6  is a block diagram of a signal compressing apparatus according to a second embodiment of this invention. 
       FIG. 7  is a block diagram of a signal compressing apparatus according to a third embodiment of this invention. 
       FIG. 8  is a flow diagram of operation of a signal processing circuit in  FIG. 7 . 
       FIG. 9  is a flowchart of a segment of a program related to operation of the signal processing circuit in  FIG. 7 . 
       FIG. 10  is a frequency-domain diagram of an example of a signal power, a scale factor, a standard noise level, and an original noise level. 
       FIG. 11  is a block diagram of a signal compressing apparatus according to a fourth embodiment of this invention. 
       FIG. 12  is a flowchart of a first segment of a program related to operation of a signal processing circuit in  FIG. 11 . 
       FIG. 13  is a diagram of the relation between a code amount adjustment value Adj and a deviation Δ. 
       FIG. 14  is a flowchart of a second segment of the program related to operation of the signal processing circuit in  FIG. 11 . 
       FIG. 15  is a block diagram of an apparatus for an optical disc according to a fifth embodiment of this invention. 
       FIG. 16  is a flowchart of a segment of a program related to operation of a CPU in  FIG. 15 . 
       FIG. 17  is a block diagram of an apparatus for an optical disc according to a sixth embodiment of this invention. 
       FIG. 18  is a flowchart of a segment of a program related to operation of a CPU in  FIG. 17 . 
       FIG. 19  is a block diagram of an apparatus for an optical disc according to a seventh embodiment of this invention. 
       FIG. 20  is a block diagram of an apparatus for an optical disc according to an eighth embodiment of this invention. 
       FIG. 21  is a block diagram of an apparatus for an optical disc according to a ninth embodiment of this invention. 
       FIG. 22  is a block diagram of an apparatus for an optical disc according to a tenth embodiment of this invention. 
       FIG. 23  is a block diagram of an apparatus for an optical disc according to an eleventh embodiment of this invention. 
       FIG. 24  is a block diagram of a compression encoder in  FIG. 23 . 
       FIG. 25  is a block diagram of an expansion decoder in  FIG. 23 . 
       FIG. 26  is a flowchart of a segment of a program related to operation of a CPU in  FIG. 23 . 
       FIG. 27  is a block diagram of an apparatus for an optical disc according to a twelfth embodiment of this invention. 
       FIG. 28  is a flowchart of a segment of a program related to operation of a CPU in  FIG. 27 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   First Embodiment 
   With reference to  FIG. 1 , a signal compressing apparatus has an input terminal  1 A connected to the input side of an A/D converter  1 . The output side of the A/D converter  1  is connected to the input side of a signal processing circuit  2 . 
   A switch  4 B has a movable contact and first and second fixed contacts. The movable contact of the switch  4 B is selectively connected to either the first fixed contact or the second fixed contact thereof. The movable contact of the switch  4 B is connected to the output side of the signal processing circuit  2 . The first fixed contact of the switch  4 B leads to the input side of a CD-ROM encoding circuit  4 A. The second fixed contact of the switch  4 B leads to the input side of a DVD encoding circuit  6 . 
   A switch  4 C has a movable contact and first and second fixed contacts. The movable contact of the switch  4 C is selectively connected to either the first fixed contact or the second fixed contact thereof. The first fixed contact of the switch  4 C is connected to the output side of the CD-ROM encoding circuit  4 A. The second fixed contact of the switch  4 C is connected to the output side of the DVD encoding circuit  6 . The movable contact of the switch  4 C leads to an apparatus output terminal  4 D. Also, the movable contact of the switch  4 C leads to the input side of a CD encoding circuit (a CD-DA encoding circuit)  5 . The output side of the CD encoding circuit  5  is connected to an apparatus output terminal  5 A. 
   The switches  4 B and  4 C cooperate to select either the CD-ROM encoding circuit  4 A or the DVD encoding circuit  6  as an effective circuit. 
   A signal generator  3 A outputs a clock signal having a frequency of 44.1 kHz. A signal generator  3 B outputs a clock signal having a frequency of 48 kHz. A signal generator  3 C outputs a clock signal having a frequency of 88.2 kHz. A signal generator  3 D outputs a clock signal having a frequency 96 kHz. 
   A switch  1 B has a movable contact, and first, second, third, and fourth fixed contacts. The movable contact of the switch  1 B is selectively connected to one of the first, second, third, and fourth fixed contacts thereof. The movable contact of the switch  1 B leads to a clock input terminal of the A/D converter  1 . The first, the second, third, and fourth fixed contacts of the switch  1 B are connected to the output terminals of the signal generators  3 A,  3 B,  3 C, and  3 D, respectively. The switch  1 B selects one of the output signals of the signal generators  3 A,  3 B,  3 C, and  3 D, and transmits the selected signal to the A/D converter  1  as a sampling clock signal. 
   A switch  7 A has a movable contact, and first, second, third, fourth, fifth, and sixth fixed contacts. The movable contact of the switch  7 A is selectively connected to one of the first, second, third, fourth, fifth, and sixth fixed contacts thereof. The movable contact of the switch  7 A leads the CD-ROM encoding circuit  4 A. The first second, third, fourth, fifth, and sixth fixed contacts of the switch  7 A are connected to taps or nodes in a series resistor combination  7 B, respectively. The series resistor combination  7 B is connected across a fixed-dc-voltage source  7 C. The switch  7 A selects one of six different voltages available in the series resistor combination  7 B, and feeds the selected voltage to the CD-ROM encoding circuit  4 A. 
   For example, the switch  7 A can be operated by a user. Operation of the signal compressing apparatus of  FIG. 1  can be changed among six different modes. The six different levels of the voltage signal fed via the switch  7 A to the CD-ROM encoding circuit  4 A are assigned to the six different modes of operation of the apparatus of  FIG. 1 , respectively. Accordingly, the switch  7 A serves as a operation-mode selecting switch, and the voltage signal fed via the switch  7 A to the CD-ROM encoding circuit  4 A represents an apparatus operation mode desired and selected by the user. Thus, the voltage signal fed via the switch  7 A to the CD-ROM encoding circuit  4 A is also referred to as the mode signal. As will be made clear later, the switches  1 B,  4 B, and  4 C are linked to the switch  7 A. 
   An analog audio signal is inputted to the A/D converter  1  via the apparatus input terminal  1 A. The A/D converter  1  changes the input analog audio signal into a corresponding digital audio signal in response to the sampling clock signal fed via the switch  1 B. Specifically, the A/D converter  1  periodically samples the input analog audio signal at a sampling frequency decided by the frequency of the sampling clock signal. The A/D converter  1  changes or quantizes every sample of the input analog audio signal into a corresponding digital audio signal segment (a corresponding audio data piece) with a predetermined quantization bit number. The predetermined quantization bit number is equal to, for example, 16 or 20. The A/D converter  1  outputs the resultant digital audio signal (referred to as the first digital audio signal) to the signal processing circuit  2 . 
   Generally, the input analog audio signal is composed of 2-channel signals. The input analog audio signal may be composed of 4-channel signals, or 6-channel signals. 
   The signal processing circuit  2  includes a DSP (digital signal processor), a microcomputer, or a similar device having a combination of an input/output port, a processing section, a ROM, and a RAM. The signal processing circuit  2  operates in accordance with a program stored in the ROM. 
   The signal processing circuit  2  is programmed to compress the first digital audio signal into a second digital audio signal according to a predetermined signal-compression technique including an orthogonal transform process. The predetermined signal-compression technique may also include a Huffman encoding process. In this case, the orthogonal transform process may be omitted from the predetermined signal-compression technique. For example, the predetermined signal-compression technique is selected from among known signal-compression techniques. The signal processing circuit  2  outputs the second digital audio signal (the compression-resultant digital audio signal) to the CD-ROM encoding circuit  4 A or the DVD encoding circuit  6  via the switch  4 B. 
   The CD-ROM encoding circuit  4 A generates auxiliary information signals (sub information signals) in response to the mode signal. The auxiliary information signals includes a sync signal and a header signal. Specifically, the CD-ROM encoding circuit  4 A generates at least a sync signal and a header signal for every sector with respect to a recording medium (a CD-ROM). When the CD-ROM encoding circuit  4 A is selected by the switch  4 B, the CD-ROM encoding circuit  4 A receives the second digital audio signal from the signal processing circuit  2 . The CD-ROM encoding circuit  4 A combines the sync signal, the header signal, and the second digital audio signal in response to the mode signal on a time-division multiplexing basis for every sector with respect to a recording medium (a CD-ROM). The combination-resultant digital audio signal is of a predetermined format equal to one of the CD-ROM signal formats. The combination-resultant digital audio signal is also referred to as the composite digital audio signal. During combining the signals, the CD-ROM encoding circuit  4 A places the second digital audio signal in a time range corresponding to a user data area in every sector with respect to a recording medium (a CD-ROM). When the CD-ROM encoding circuit  44  is selected by the switch  4 C, the CD-ROM encoding circuit  4 A outputs the combination-resultant digital audio signal (the composite digital audio signal) to the apparatus output terminal  4 D and the CD encoding circuit  5 . 
   The DVD encoding circuit  6  generates a header signal for every pack. When the DVD encoding circuit  6  is selected by the switch  4 B, the DVD encoding circuit  6  receives the second digital audio signal from the signal processing circuit  2 . The DVD encoding circuit  6  combines the header signal and the second digital audio signal on a time-division multiplexing basis for every pack. The combination-resultant digital audio signal is of a predetermined format equal to the DVD signal format. The combination-resultant digital audio signal is also referred to as the composite digital audio signal. During combining the signals, the DVD encoding circuit  6  places the second digital audio signal in a time range corresponding to a user data area or a packet area in every pack. When the DVD encoding circuit  6  is selected by the switch  4 C, the DVD encoding circuit  6  outputs the combination-resultant digital audio signal (the composite digital audio signal) to the apparatus output terminal  4 D and the CD encoding circuit  5 . 
   The CD encoding circuit  5  converts the output signal of the CD-ROM encoding circuit  4 A or the output signal of the DVD encoding circuit  6  into a digital audio signal of a predetermined format equal to the CD-WO (compact disc write once) format or the CD-DA format. The CD encoding circuit  5  feeds the digital audio signal of the CD-WO format or the CD-DA format to the apparatus output terminal  5 A. 
   For example, the CD encoding circuit  5  subjects the output signal of the CD-ROM encoding circuit  4 A or the output signal of the DVD encoding circuit  6  to a CIRC (Cross Interleave Reed-Solomon Code) encoding process according to the CD-WO standards or the CD-DA standards. The CD encoding circuit  5  outputs the encoding-resultant digital audio signal to the apparatus output terminal  5 A. Specifically, the CD encoding circuit  5  generates an error correction signal in response to the output signal of the CD-ROM encoding circuit  4 A or the output signal of the DVD encoding circuit  6 , and adds the error correction signal to the output signal of the CD-ROM encoding circuit  4 A or the output signal of the DVD encoding circuit  6 . The error correction signal uses a cross interleave Reed-Solomon code. The CD encoding circuit  5  feeds the addition-resultant signal to the apparatus output terminal  5 A. 
   Operation of the signal compressing apparatus of  FIG. 1  can be changed among six different modes. During the first mode of operation, the switch  1 B selects the output signal of the signal generator  3 A which has a frequency of 44.1 kHz. The switch  1 B transmits the selected signal to the A/D converter  1  as a sampling clock signal. Accordingly, during the first mode of operation, the frequency of the signal sampling by the A/D converter  1  is equal to 44.1 kHz. During the first mode of operation, the switches  4 B and  4 C select the CD-ROM encoding circuit  4 A. In this case, the CD-ROM encoding circuit  4 A generates a sequence of a sync signal, a header signal, a sub header signal, a user data block, and an EDC signal in response to the mode signal and the second digital audio signal for every sector with respect to a recording medium (a CD-ROM). The user data block contains the second digital audio signal. During the first mode of operation, a 1-sector-corresponding segment of the composite digital audio signal generated by the CD-ROM encoding circuit  4 A has a form such as shown in  FIG. 2 . The user data block has 2,324 bytes. 
   During the second mode of operation, the switch  1 B selects the output signal of the signal generator  3 C which has a frequency of 88.2 kHz. The switch  1 B transmits the selected signal to the A/D converter  1  as a sampling clock signal. Accordingly, during the second mode of operation, the frequency of the signal sampling by the A/D converter  1  is equal to 88.2 kHz. During the second mode of operation, the switches  4 B and  4 C select the CD-ROM encoding circuit  4 A. In this case, the CD-ROM encoding circuit  4 A generates a sequence of a sync signal, a header signal, a sub header signal, a user data block, and an EDC signal in response to the mode signal and the second digital audio signal for every sector with respect to a recording medium (a CD-ROM). The user data block contains the second digital audio signal. During the second mode of operation, a 1-sector-corresponding segment of the composite digital audio signal generated by the CD-ROM encoding circuit  4 A has a form such as shown in  FIG. 2 . The user data block has 2,324 bytes. 
   During the third mode of operation, the switch  1 B selects the output signal of the signal generator  3 A which has a frequency of 44.1 kHz. The switch  1 B transmits the selected signal to the A/D converter  1  as a sampling clock signal. Accordingly, during the third mode of operation, the frequency of the signal sampling by the A/D converter  1  is equal to 44.1 kHz. During the third mode of operation, the switches  4 B and  4 C select the CD-ROM encoding circuit  4 A. In this case, the CD-ROM encoding circuit  4 A generates a sequence of a sync signal, a header signal, and a user data block in response to the mode signal and the second digital audio signal for every sector with respect to a recording medium (a CD-ROM). The user data block contains the second digital audio signal. During the third mode of operation, a 1-sector-corresponding segment of the composite digital audio signal generated by the CD-ROM encoding circuit  4 A has a form such as shown in  FIG. 3 . The user data block has 2,336 bytes. 
   During the fourth mode of operation, the switch  1 B selects the output signal of the signal generator  3 C which has a frequency of 88.2 kHz. The switch  1 B transmits the selected signal to the A/D converter  1  as a sampling clock signal. Accordingly, during the fourth mode of operation, the frequency of the signal sampling by the A/D converter  1  is equal to 88.2 kHz. During the fourth mode of operation, the switches  4 B and  4 C select the CD-ROM encoding circuit  4 A. In this case, the CD-ROM encoding circuit  4 A generates a sequence of a sync signal, a header signal, and a user data block in response to the mode signal and the second digital audio signal for every sector with respect to a recording medium (a CD-ROM). The user data block contains the second digital audio signal. During the fourth mode of operation, a 1-sector-corresponding segment of the composite digital audio signal generated by the CD-ROM encoding circuit  4 A has a form such as shown in  FIG. 3 . The user data block has 2,336 bytes. 
   During the fifth mode of operation, the switch  1 B selects the output signal of the signal generator  3 B which has a frequency of 48 kHz. The switch  1 B transmits the selected signal to the A/D converter  1  as a sampling clock signal. Accordingly, during the fifth mode of operation, the frequency of the signal sampling by the A/D converter  1  is equal to 48 kHz. During the fifth mode of operation, the switches  4 B and  4 C select the DVD encoding circuit  6 . In this case, the DVD encoding circuit  6  generates a sequence of a header signal and a user data block (a packet or packets) in response to the second digital audio signal for every pack. The user data block (the pack or packets) contains the second digital audio signal. During the fifth mode of operation, a 1-pack-corresponding segment of the composite digital audio signal generated by the DVD encoding circuit  6  has a form such as shown in  FIG. 4 . The user data block has 2,034 bytes. 
   It should be noted that in this specification, a DVD may be another disc in a DVD family such as a DVD-ROM, a DVD-WO, and a DVD-RAM. 
   During the sixth mode of operation, the switch  1 B selects the output signal of the signal generator  3 D which has a frequency of 96 kHz. The switch  1 B transmits the selected signal to the A/D converter  1  as a sampling clock signal. Accordingly, during the sixth mode of operation, the frequency of the signal sampling by the A/D converter  1  is equal to 96 kHz. During the sixth mode of operation, the switches  4 B and  4 C select the DVD encoding circuit  6 . In this case, the DVD encoding circuit  6  generates a sequence of a header signal and a user data block (a packet or packets) in response to the second digital audio signal for every pack. The user data block (the pack or packets) contains the second digital audio signal. During the sixth mode of operation, a 1-pack-corresponding segment of the composite digital audio signal generated by the DVD encoding circuit  6  has a form such as shown in  FIG. 4 . The user data block has 2,034 bytes. 
   The apparatus output terminal  4 D can be connected to a transmission line in, for example, a communication network. In this case, the output signal of the CD-ROM encoding circuit  4 A or the DVD encoding circuit  6  can be fed to the transmission line before being transmitted therealong. 
   The apparatus output terminal  4 D can be connected to a pre-mastering apparatus or a mastering apparatus for a CD-ROM or a DVD. In this case, the output signal of the CD-ROM encoding circuit  4 A or the DVD encoding circuit  6  can be fed to the pre-mastering apparatus or the mastering apparatus before being recorded thereby on a pre-master disc or a master disc for a CD-ROM or a DVD. 
   The apparatus output terminal  4 D can be connected to a recording apparatus. In this case, the output signal of the CD-ROM encoding circuit  4 A or the DVD encoding circuit  6  can be fed to the recording apparatus before being recorded thereby on a recording medium such as a magnetic tape or a magnetic disc. 
     FIG. 5  shows a drive apparatus  8  for a CD-WO  9 . The drive apparatus  8  can be connected to the output terminal  5 A in  FIG. 1 . In this case, the output signal of the CD encoding circuit  5  can be fed to the drive apparatus  8  before being recorded thereby on the CD-WO  9 . 
   Second Embodiment 
     FIG. 6  shows a second embodiment of this invention which is similar to the embodiment of  FIGS. 1-5  except for the following design change. The embodiment of  FIG. 6  uses a signal processing circuit  2 A instead of the signal processing circuit  2  in  FIG. 1 . 
   An analog audio signal inputted to the A/D converter  1  is composed of 2-channel signals. The input analog audio signal may be composed of 4-channel signals, or 6-channel signals. 
   The signal processing circuit  2 A includes a DSP (digital signal processor), a microcomputer, or a similar device having a combination of an input/output port, a processing section, a ROM, and a RAM. The signal processing circuit  2 A operates in accordance with a program stored in the ROM. 
   The signal processing circuit  2 A receives the first digital audio signal from the A/D converter  1 . The signal processing circuit  2 A is programmed to process the first digital audio signal into a second digital audio signal according to a predetermined signal-compression technique including an orthogonal transform process. The predetermined signal-compression technique may also include a Huffman encoding process. In this case, the orthogonal transform process may be omitted from the predetermined signal-compression technique. The signal processing by the signal processing circuit  2 A is implemented block by block. Here, “block” corresponds to a predetermined number “2 m ” of data pieces of the first digital audio signal per channel. 
   Specifically, the signal processing circuit  2 A subjects a set of 2 m  data pieces of the first digital audio signal to orthogonal transform, thereby generating a signal representing the frequency spectrum of the first digital audio signal. The signal processing circuit  2 A divides the resultant frequency-spectrum signal into signals in different frequency bands by a filtering process. The signal processing circuit  2 A normalizes and quantizes each of the frequency-band signals. The signal processing circuit  2 A generates helper information representing the conditions of the normalization (for example, the normalization level or the normalization bit number) and the conditions of the quantization. The signal processing circuit  2 A combines the normalization/quantization-resultant signals and the helper information. The signal processing circuit  2 A subjects the combination-resultant signal to an allocation process. The signal processing circuit  2 A outputs the allocation-resultant signal to the switch  4 B. 
   The signal processing circuit  2 A may subject the combination-resultant signal to a Huffman encoding process. In this case, the signal processing circuit  2 A subjects the encoding-resultant signal to an allocation process. The signal processing circuit  2 A outputs the allocation-resultant signal to the switch  4 B. 
   Third Embodiment 
     FIG. 7  shows a third embodiment of this invention which is similar to the embodiment of  FIGS. 1-5  except for the following design change. The embodiment of  FIG. 7  uses a signal processing circuit  2 B instead of the signal processing circuit  2  in  FIG. 1 . 
   The signal processing circuit  2 B includes a DSP (digital signal processor), a microcomputer, or a similar device having a combination of an input/output port, a processing section, a ROM, and a RAM. The signal processing circuit  2 B operates in accordance with a program stored in the ROM. 
   The signal processing circuit  213  receives the first digital audio signal from the A/D converter  1 . The signal processing circuit  2 B is programmed to process the first digital audio signal into a second digital audio signal according to a predetermined signal-compression technique. 
     FIG. 8  shows a flow of operation of the signal processing circuit  2 B. It should be noted that  FIG. 8  does not show the hardware structure of the signal processing circuit  2 B. With reference to  FIG. 8 , a block  22  subjects an input signal (that is, the first digital audio signal from the A/D converter  1 ) to a windowing process and an orthogonal transform process. Preferably, the orthogonal transform process is of the MDCT (modified discrete cosine transform) type. The resultant data representing orthogonal transform coefficients are divided by the block  22  into coefficient-representing data pieces corresponding to different frequency bands respectively. 
   A block  23  following the block  22  decides scale factors for the coefficient-representing data pieces corresponding to the frequency bands respectively. The block  23  normalizes the coefficient-representing data pieces in response to the decided scale factors respectively. The block  23  informs a block  27  of the decided scale factors. 
   A block  24  following the block  23  quantizes the normalization-resultant data pieces in response to variable quantization factors (variable quantization steps). The bock  24  may implement the quantization-resultant data pieces to entropy encoding. 
   A block  25  following the block  23  calculates desired code amounts (desired bit numbers) from the normalization-resultant data pieces for the frequency bands respectively. The minimum audible limit characteristics and the masking effects of a predetermined auditory sensation model are used in calculating the desired code amounts. 
   A block  26  following the block  25  calculates desired quantization factors (desired quantization steps) from the desired code amounts for the frequency bands respectively. The block  26  informs the block  24  of the desired quantization factors (the desired quantization steps). The block  24  quantizes the normalization-resultant data pieces in response to quantization factors equal to the desired quantization factors. The block  26  informs the block  27  of the desired quantization factors as actual quantization factors used by the block  24 . 
   The block  27  follows the block  24 . The block  27  generates helper information such as header information. The block  27  combines the quantization-resultant data pieces, the information of the scale factors, the information of the quantization factors, and the helper information into a bit stream which is an output signal of the signal processing circuit  2 B. 
     FIG. 9  is a flowchart of a segment of the program which corresponds to the blocks  24 ,  25 , and  26  in  FIG. 8 . Signal processing by the blocks  24 ,  25 , and  26  is implemented frame by frame. Here, “frame” is a predetermined time interval. As shown in  FIG. 9 , a first step S 1  of the program segment decides first quantization bit numbers (first quantization factors) for the frequency bands respectively. Regarding the normalization-resultant data pieces, the step S 1  estimates generated bit numbers in response to the decided first quantization bit numbers for the frequency bands respectively. The step S 1  calculates a total bit number which equals the sum of the estimated bit numbers. 
   A step S 2  following the step S 1  calculates an available bit number in the current frame. A step S 3  following the step S 2  compares the calculated total bit number and the calculated available bit number to decide whether or not a code amount is insufficient. When the total bit number is greater than the available bit number, that is, when a code amount is insufficient, the program advances from the step S 3  to a step S 4 . Otherwise, the program advances from the step S 3  to a step S 8 . 
   The step S 4  calculates band powers p[i] which are equal to the square of the scale factors for the frequency bands respectively. Here, “i” denotes a variable integer for identifying the frequency bands. The step S 4  calculates masking curves m[i] from the calculated band powers p[i] in accordance with the minimum audible limit characteristic and the masking effects of a predetermined auditory sensation model. Specifically, the masking curves m[i] are given by the convolution of model-based reference curves r[i] and the band powers p[i]. 
   A step S 5  following the step S 4  calculates standard noise levels N[i] from the minimum audible limits abs[i] and the masking curves m[i] for the frequency bands respectively. For example, the calculation of the standard noise levels N[i] uses an equation given as:
 
N[i]=max[m[i],abs[i]]
 
where “max” denotes an operator for selecting the greater of the values in the brackets.
 
   A step S 6  subsequent to the step S 5  distributes deleted bits (that is, bits to be deleted) to the frequency bands according to the following rules. First one of the deleted bits is allocated to the frequency band having the highest standard noise level. Then, the standard noise level corresponding to this frequency band is reduced by a predetermined level. Subsequently, second one of the deleted bits is allocated to the frequency band having the highest standard noise level. Then, the standard noise level corresponding to this frequency band is reduced by the predetermined level. These processes are iteratively executed until a final one of the deleted bits is allocated. 
   In other words, first one of the deleted bits is allocated to the frequency band having the highest standard noise level. Second one of the deleted bits is allocated to the frequency band having the second highest standard noise level. Third one of the deleted bits is allocated to the frequency band having the third highest standard noise level. These processes are iteratively executed until a final one of the deleted bits is allocated. During these processes, when one of the deleted bits is allocated to a frequency band, the standard noise level corresponding to this frequency band is decreased by a predetermined level. 
   Generally, the shape of the distribution of the deleted bits is similar to the shape formed by the standard noise levels N[i]. The block S 6  corrects the first quantization bit numbers (the first quantization factors) into second quantization bit numbers (second quantization factors) in response to the distribution of the deleted bits to the frequency bands respectively. After the step S 6 , the program advances to a step S 7 . 
   The step S 8  allocates surplus bits to the frequency bands. The step S 8  sets second quantization bit numbers (second quantization factors) equal to the first quantization bit numbers (the first quantization factors) for the frequency bands respectively. After the step S 8 , the program advances to the step S 7 . 
   The step S 7  quantizes the normalization-resultant data pieces in response to the second quantization factors (the second quantization bit numbers) of the frequency bands respectively. After the step S 7 , the current execution cycle of the program segment ends. 
   As shown in  FIG. 10 , the standard noise level varies frequency-band to frequency-band even in the case where the noise level of the original signal is fixed independent of the frequency bands. The stepwise line formed by the standard noise levels is shaped according to the auditory sensation model. The deleted bits are distributed to the frequency bands according to the standard noise levels. Therefore, it is possible to effectively suppress a decrease in tone quality in auditory sensation which would be caused by the quantization. 
   Fourth Embodiment 
     FIG. 11  shows a fourth embodiment of this invention which is similar to the embodiment of  FIGS. 7-10  except for design changes indicated hereinafter. The embodiment of  FIG. 11  uses a signal processing circuit  2 C instead of the signal processing circuit  2 B in  FIG. 7 . 
   The signal processing circuit  2 C includes a DSP (digital signal processor), a microcomputer, or a similar device having a combination of an input/output port, a processing section, a ROM, and a RAM. The signal processing circuit  2 C operates in accordance with a program stored in the ROM. 
   The signal processing circuit  2 C receives the first digital audio signal from the A/D converter  1 . The signal processing circuit  2 C is programmed to process the first digital audio signal into a second digital audio signal according to a predetermined signal-compression technique. 
     FIG. 12  is a flowchart of a segment of the program in the signal processing circuit  2 C. Generally, the program segment in  FIG. 12  is iteratively executed. As shown in  FIG. 12 , a first step S 11  of the program segment fetches information of used code amounts in all time intervals composing an object term. For example, the object term corresponds to the time length of a tune represented by an input audio signal or the sum of the time lengths of all tunes for one disc. The step S 11  calculates a mean code amount Tm among the used code amounts. The step S 11  fetches information of a desired code amount Td. 
   A step S 12  following the step S 11  compares the mean code amount Tm and the desired code amount Td to decide whether an insufficient condition or a surplus condition occurs in code amount. When the mean code amount Tm is greater than the desired code amount Td, that is, when a surplus condition occurs, the program advances from the step S 12  to a step S 13 . Otherwise, the program advances from the step S 12  to a step S 19 . 
   The step S 13  calculates the deviation (the difference) Δ which is equal to the used code amount minus the desired code amount Td for each of the time intervals. The step S 13  quantizes the deviation-Δ-representing data piece in response to a predetermined quantization step width (a predetermined quantization step size) St for each of the time intervals. The quantization step width (the quantization step size) St is expressed in bit number. The step S 13  generates a histogram related to the deviations Δ. 
   A step S 14  following the step S 13  calculates the deviation sum Sm in negative ranges of the histogram and the deviation sum Sp in positive ranges of the histogram according to equations given as: 
           Sm   =       ∑     i   =   min       -   1       ⁢           ⁢       histogram   ⁡     [   i   ]       ·        i        ·   St                   Sp   =       ∑     i   =   1     max     ⁢       histogram   ⁡     [   i   ]       ·   i   ·   St             
where “i” denotes an index of the histogram, and “min” and “max” denote an index minimum limit and an index maximum limit respectively.
 
   A step S 15  subsequent to the step S 14  calculates the ratio “Sm/(Sm+Sp)”. The step S 15  compares the calculated ratio with a predetermined value Bd equal to, for example, 0.33. When the calculated ratio is equal to or greater than the predetermined value Bd, the program advances from the step S 15  to a step S 16 . Otherwise, the program advances from the step S 15  to a step S 17 . 
   The step S 16  sets an offset value Ofs of the histogram to “0”. After the step S 16 , the program advances to a step S 18 . 
   The step S 17  sets the offset value Ofs so that the ratio “Sm/(Sm+Sp)” will be equal to or greater than the predetermined value Bd. After the step S 17 , the program advances to the step S 18 . 
   For each of the time intervals, the step S 18  compares the deviation Δ with the product of the offset value Ofs and the quantization step width St. When the deviation Δ is equal to or smaller than the product “Ofs·St”, the step S 18  calculates a code amount adjustment value (a code amount corrective value) Adj from the offset value Ofs and the quantization step width St according to the following equation.
 
 Adj=−Ofs·St  
 
When the deviation Δ is greater than the product “Ofs·St”, the step S 18  calculates the code amount adjustment value (the code amount corrective value) Adj according to the following equation.
 
 Adj=−Ofs·St −{( Sp−Sm )/ Sp }·(Δ− Ofs·St )
 
The step S 18  calculates the code amount adjustment value (the code amount corrective value) Adj for each of the time intervals. After the step S 18 , the current execution cycle of the program segment ends.
 
   For each of the time intervals, the step S 19  calculates the code amount adjustment value (the code amount corrective value) Adj from the mean code amount Tm and the desired code amount Td according to the following equation.
 
 Adj=Td−Tm  
 
After the step S 19 , the current execution cycle of the program segment ends.
 
   With reference to  FIG. 13 , the code amount adjustment value (the code amount corrective value) Adj varies as a function of the deviation Δ. Specifically, in a range where the deviation Δ is positive, the code amount adjustment value (the code amount corrective value) Adj increases as the deviation Δ increases. 
     FIG. 14  is a flowchart of another segment of the program in the signal processing circuit  2 C. The program segment in  FIG. 14  is executed frame by frame. As shown in  FIG. 14 , a first step S 21  of the program segment decides first quantization bit numbers (first quantization factors) for the frequency bands respectively. Regarding the normalization-resultant data pieces, the step S 21  estimates generated bit numbers in response to the decided first quantization bit numbers for the frequency bands respectively. The step S 21  calculates a total bit number which equals the sum of the estimated bit numbers. 
   A step S 22  following the step S 21  fetches information of the code amount adjustment value (the code amount corrective value) Adj for the current frame. 
   A step S 23  subsequent to the step S 22  decides whether or not the code amount adjustment value (the code amount corrective value) Adj is negative. When the code amount adjustment value (the code amount corrective value) Adj is negative, the program advances from the step S 23  to a step S 24 . Otherwise, the program advances from the step S 23  to a step S 28 . 
   The step S 24  calculates band powers p[i] which are equal to the square of the scale factors for the frequency bands respectively. Here, “i” denotes a variable integer for identifying the frequency bands. The step S 24  calculates masking curves m[i] from the calculated band powers p[i] in accordance with the minimum audible limit characteristic and the masking effects of a predetermined auditory sensation model. Specifically, the masking curves m[i] are given by the convolution of model-based reference curves r[i] and the band powers p[i]. 
   A step S 25  following the step S 24  calculates standard noise levels N[i] from the minimum audible limits abs[i] and the masking curves m[i] for the frequency bands respectively. For example, the calculation of the standard noise levels N[i] uses an equation given as:
 
N[i]=max[m[i],abs[i]]
 
where “max” denotes an operator for selecting the greater of the values in the brackets.
 
   A step S 26  subsequent to the step S 25  distributes deleted bits (that is, bits to be deleted) to the frequency bands according to the following rules. First one of the deleted bits is allocated to the frequency band having the highest standard noise level. Then, the standard noise level corresponding to this frequency band is reduced by a predetermined level. Subsequently, second one of the deleted bits is allocated to the frequency band having the highest standard noise level. Then, the standard noise level corresponding to this frequency band is reduced by the predetermined level. These processes are iteratively executed until a final one of the deleted bits is allocated. 
   In other words, first one of the deleted bits is allocated to the frequency band having the highest standard noise level. Second one of the deleted bits is allocated to the frequency band having the second highest standard noise level. Third one of the deleted bits is allocated to the frequency band having the third highest standard noise level. These processes are iteratively executed until a final one of the deleted bits is allocated. During these processes, when one of the deleted bits is allocated to a frequency band, the standard noise level corresponding to this frequency band is decreased by a predetermined level. 
   Generally, the shape of the distribution of the deleted bits is similar to the shape formed by the standard noise levels N[i]. The block S 26  corrects the first quantization bit numbers (the first quantization factors) into second quantization bit numbers (second quantization factors) in response to the distribution of the deleted bits to the frequency bands respectively. After the step S 26 , the program advances to a step S 27 . 
   The step S 28  allocates surplus bits to the frequency bands. The step S 28  sets second quantization bit numbers (second quantization factors) equal to the first quantization bit numbers (the first quantization factors) for the frequency bands respectively. After the step S 28 , the program advances to the step S 27 . 
   The step S 27  quantizes the normalization-resultant data pieces in response to the second quantization factors (the second quantization bit numbers) of the frequency bands respectively. After the step S 27 , the current execution cycle of the program segment ends. 
   Fifth Embodiment 
     FIG. 15  shows an apparatus for an optical disc  101  which can be selected from among various discs such as a CD-DA, a CD-ROM, and a CD-ROM-audio. The apparatus of  FIG. 15  includes a spindle motor  102 , an optical head  103 , a spindle motor servo section  104 , a focusing tracking servo section  105 , and a servo control circuit  106 . The spindle motor servo section  104  is connected between the spindle motor  102  and the servo control circuit  106 . The focusing tracking servo section  105  is connected between the optical head  103  and the servo control circuit  106 . 
   The optical disc  101  can be placed into and out of a normal position within the apparatus of  FIG. 15 . The spindle motor  102  serves to rotate the optical disc  101  placed in the normal position. The spindle motor servo section  104  controls the spindle motor  104  in response to an output signal of the servo control circuit  106  to implement control of the rotational speed of the optical disc  101 . The focusing tracking servo section  105  controls the optical head  103  in response to output signals of the servo control circuit  106  to implement focusing control of the optical head  103  and tracking control of the optical head  103 . 
   The optical head  103  is electrically connected to an RF amplifier  107  followed by a reproducing decoder  108 . During a playback mode of operation of the apparatus of  FIG. 15 , the optical head  103  reads out information from the optical disc  101 , and outputs an RF signal representing the read-out information. The output signal of the optical head  103  is amplified by the RF amplifier  107 . The amplification-resultant signal is outputted from the RF amplifier  107  to the reproducing decoder  108 . The reproducing decoder  108  subjects the output signal of the RF amplifier  107  to EFM demodulation, thereby recovering data corresponding to the information recorded on the optical disc  101 . 
   The optical head  103  is electrically connected to a laser drive section  109  following a recording encoder  110 . During a recording mode of operation of the apparatus of  FIG. 15 , the recording encoder  110  subjects recorded data (data to be recorded) to EFM modulation. The recording encoder  110  outputs the modulation-resultant signal to the laser drive section  109 . The optical head  103  generates a laser light beam. The optical head  103  applies the laser light beam to the optical disc  101 . The laser drive section  109  controls the power or the intensity of the laser light beam in response to the output signal of the recording encoder  110  so that information corresponding to the recorded data can be recorded on the optical disc  101 . 
   The servo control circuit  106  is connected to the reproducing decoder  108 , the recording encoder  110 , and a CPU  117 . The servo control circuit  106  adjusts the spindle motor servo section  104  and the focusing tracking servo section  105  in response to output signals of the reproducing decoder  108 , the recording encoder  110 , and the CPU  117 . 
   A signal processing circuit  111  is connected to the reproducing decoder  108  and the recording encoder  110 . The signal processing circuit  111  is connected to apparatus output terminals  112 A and  112 B via an output circuit  112 . An apparatus input terminal  113 A is connected to the signal processing circuit  111  via an input circuit  113 . 
   During the playback mode of operation of the apparatus of  FIG. 15 , the reproducing decoder  108  outputs the recovered data to the signal processing circuit  111 . The signal processing circuit  111  processes the recovered data. The signal processing circuit  111  outputs the processing-resultant data to the output circuit  112 . The output circuit  112  has a section which separates the processing-resultant data into audio data and video data. The output circuit  112  has a first D/A converter which changes the audio data into a corresponding analog audio signal. The output circuit  112  feeds the analog audio signal to the apparatus output terminal  112 A. The output circuit  112  has a second D/A converter which changes the video data into a corresponding analog video signal. The output circuit  112  feeds the analog video signal to the apparatus output terminal  112 B. 
   During the recording mode of operation of the apparatus of  FIG. 15 , an input analog audio signal to be recorded travels to the input circuit  113  via the apparatus input terminal  113 A. The input circuit  113  has an A/D converter which changes the input analog audio signal into a corresponding digital audio signal. The input circuit  113  feeds the digital audio signal to the signal processing circuit  111 . The signal processing circuit  111  processes the digital audio signal into recorded data (data to be recorded). The signal processing circuit  111  outputs the recorded data to the recording encoder  110 . 
   As previously explained, the CPU  117  is connected to the servo control circuit  106 . The CPU  117  is also connected to a CPU  114 , an operation unit  115 , and a display unit  116 . Operation of the apparatus of  FIG. 15  is changeable among different modes including the playback mode and the recording mode. The operation unit  115  has keys for selecting and designating one out of the different modes of operation of the apparatus of  FIG. 15 . The keys in the operation unit  115  can be operated by a user. The operation unit  115  informs the CPU  117  of the currently designated operation mode. 
   The operation unit  115  has a button for selecting and designating one out of different formats. The button in the operation unit  115  can be operated by the user. The operation unit  115  informs the CPU  117  of the currently designated format. 
   The CPU  117  has a combination of an input/output port, a processing section, a ROM, and a RAM. The CPU  117  operates in accordance with a program stored in the ROM. The CPU  117  is programmed to implement the following processes. The CPU  117  transfers the information of the currently designated operation mode and the information of the currently designated format to the CPU  114 . The CPU  117  communicates with the servo control circuit  106 . The CPU  117  communicates with the CPU  114 . The CPU  117  generates a display signal in response to the information from the operation unit  115 , information from the servo control circuit  106 , and information from the CPU  114 . The CPU  117  outputs the display signal to the display unit  116 . The display signal is indicated by the display unit  116 . 
   As previously indicated, the CPU  114  is connected to the CPU  117 . The CPU  114  is also connected to the signal processing circuit  111 . The CPU  114  has a combination of an input/output port, a processing section, a ROM, and a RAM. The CPU  114  operates in accordance with a program stored in the ROM. The CPU  114  is programmed to control the signal processing circuit  111  in response to information from the CPU  117 . 
   The signal processing circuit  111  includes a CD-DA encoder  120 A a CD-DA decoder  120 B, a CD-ROM encoder  121 , a CD-ROM decoder  122 , switches  123  and  124 , an orthogonal transform/Huffman encoder  125 , an orthogonal transform/Huffman decoder  126 , and switches  127  and  128 . 
   The input side of the CD-DA decoder  120 B is connected to the output side of the reproducing decoder  108 . The output side of the CD-DA decoder  120 B is connected to the input side of the CD-ROM decoder  122 . The output side of the CD-DA decoder  120 B is also connected to the CPU  114 . The switch  124  has a movable contact and fixed contacts “a” and “b”. The switch  124  has a control terminal. The switch  124  is changeable among three different states in response to a signal fed to the control terminal. When the switch  124  assumes a first state, the movable contact thereof connects with the fixed contact “a” thereof and disconnects from the fixed contact “b” thereof. When the switch  124  assumes a second state, the movable contact thereof connects with the fixed contact “b” thereof and disconnects from the fixed contact “a” thereof. When the switch  124  assumes a third state, the movable contact thereof connects with neither the fixed contact “a” thereof nor the fixed contact “b” thereof. The control terminal of the switch  124  is connected to the CPU  114 . The fixed contact “a” of the switch  124  leads from the output side of the CD-ROM decoder  122 . The fixed contact “b” of the switch  124  leads from the output side of the CD-DA decoder  120 B. The movable contact of the switch  124  leads to the input side of the orthogonal transform/Huffman decoder  126 . 
   The switch  128  has a movable contact and fixed contacts “c” and “d”. The switch  128  has a control terminal. The switch  128  is changeable among three different states in response to a signal fed to the control terminal. When the switch  128  assumes a first state, the movable contact thereof connects with the filed contact “c” thereof and disconnects from the fixed contact “d” thereof. When the switch  128  assumes a second state, the movable contact thereof connects with the fixed contact “d” thereof and disconnects from the fixed contact “c” thereof. When the switch  128  assumes a third state, the movable contact thereof connects with neither the fixed contact “c” thereof nor the fixed contact “d” thereof. The control terminal of the switch  128  is connected to the CPU  114 . The fixed contact “c” of the switch  128  leads from the output side of the orthogonal transform/Huffman decoder  126 . The fixed contact “d” of the switch  128  leads from the movable contact of the switch  124 . The movable contact of the switch  128  leads to the input side of the output circuit  112 . The output side of the orthogonal transform/Huffman decoder  126  is connected to the CPU  114 . 
   The switch  127  has a movable contact and fixed contacts “g” and “h”. The switch  127  has a control terminal. The switch  127  is changeable among three different states in response to a signal fed to the control terminal. When the switch  127  assumes a first state, the movable contact thereof connects with the fixed contact “g” thereof and disconnects from the fixed contact “h” thereof. When the switch  127  assumes a second state, the movable contact thereof connects with the fixed contact “h” thereof and disconnects from the fixed contact “g” thereof. When the switch  127  assumes a third state, the movable contact thereof connects with neither the fixed contact “g” thereof nor the fixed contact “h” thereof. The control terminal of the switch  127  is connected to the CPU  114 . The movable contact of the switch  127  leads from the output side of the input circuit  113 . The fixed contact “h” of the switch  127  leads to the input side of the orthogonal transform/Huffman encoder  125 . 
   The switch  123  has a movable contact and fixed contacts “e” and “f”. The switch  123  has a control terminal. The switch  123  is changeable among three different states in response to a signal fed to the control terminal. When the switch  123  assumes a first state, the movable contact thereof connects with the fixed contact “e” thereof and disconnects from the fixed contact “f” thereof. When the switch  123  assumes a second state, the movable contact thereof connects with the fixed contact “f” thereof and disconnects from the fixed contact “e” thereof. When the switch  123  assumes a third state, the movable contact thereof connects with neither the fixed contact “e” thereof nor the fixed contact “f” thereof. The control terminal of the switch  123  is connected to the CPU  114 . The movable contact of the switch  123  leads from the fixed contact “g” of the switch  127  and the output side of the orthogonal transform/Huffman encoder  125 . The fixed contact “e” of the switch  123  leads to the input side of the CD-DA encoder  120 A. The fixed contact “f” of the switch  123  leads to the input side of the CD-ROM encoder  121 . The output side of the CD-ROM encoder  121  is connected to the input side of the CD-DA encoder  120 A. The output side of the CD-DA encoder  120 A is connected to the input side of the recording encoder  110 . 
   The CPU  114  is programmed to control the switches  123 ,  124 ,  127 , and  128  in the signal processing circuit  111  as follows. It is assumed that the user designates the recording mode of operation of the apparatus of  FIG. 15  by actuating the operation unit  115 . In this case, the user also designates the format by actuating the operation unit  115 . Generally, the designated format corresponds to the standards of an optical disc  101  set in the normal position within the apparatus of  FIG. 15 . The operation unit  115  informs the CPU  117  that the recording mode of operation is currently designated. Also, the operation unit  115  informs the CPU  117  of the currently designated format. The CPU  117  transfers the information of the currently designated operation mode and the currently designated format to the CPU  114 . When the CPU  114  is informed that the recording mode of operation is currently designated, the CPU  114  sets the switches  124  and  128  in their third states. In this case, the movable contact of the switch  124  separates from both the fixed contacts “a” and “b” thereof while the movable contact of the switch  128  separates from both the fixed contacts “c” and “d” thereof. Therefore, none of the orthogonal transform/Huffman decoder  126 , the CD-ROM decoder  122 , and the CD-DA decoder  120 B is connected to the output circuit  112 . The CPU  114  recognizes the currently designated format. When the currently designated format agrees with the CD-DA format, the CPU  114  controls the switches  123  and  127  so that the movable contact of the switch  123  connects with the fixed contact “e” thereof and the movable contact of the switch  127  connects with the fixed contact “g” thereof. Therefore, the CD-DA encoder  120 A is connected to the input circuit  113  while the CD-ROM encoder  121  and the orthogonal transform/Huffman encoder  125  are disconnected from the input circuit  113 . When the currently designated format agrees with the CD-ROM format, the CPU  114  controls the switches  123  and  127  so that the movable contact of the switch  123  connects with the fixed contact “f” thereof and the movable contact of the switch  127  connects with the fixed contact “g” thereof. Therefore, the CD-ROM encoder  121  is connected to the input circuit  113  while the orthogonal transform/Huffman encoder  125  is disconnected from the input circuit  113 . When the currently designated format agrees with the CD-ROM-audio format, the CPU  114  controls the switches  123  and  127  so that the movable contact of the switch  123  connects with the fixed contact “f” thereof and the movable contact of the switch  127  connects with the fixed contact “h” thereof. Therefore, the orthogonal transform/Huffman encoder  125  is connected to the input circuit  113  while the CD-ROM encoder  121  is connected to the orthogonal transform/Huffman encoder  125 . 
   During the recording mode of operation of the apparatus of  FIG. 15 , the servo control circuit  106  adjusts the spindle servo section  104  to optimize the rotational speed of the spindle motor  102 , that is, the rotational speed of the optical disc  101 . In addition, the servo control circuit  106  adjusts the focusing tracking servo section  105  to optimize focusing and tracking conditions of the optical head  103  relative to the optical disc  101 . At a start of the recording mode of operation of the apparatus of  FIG. 15 , the CPU  117  informs the servo control circuit  106  of a desired initial position of the optical head  103  relative to the optical head  101 . The servo control circuit  106  adjusts the focusing tracking servo section  105  in response to the positional information from the CPU  117 , thereby setting the optical head  103  in a position equal to the desired initial position. During the recording mode of operation of the apparatus of  FIG. 15 , the servo control circuit  106  adjusts the focusing tracking servo section  105  to move the optical head  103  from the initial position to scan the optical disc  101 . 
   During the recording mode of operation of the apparatus of  FIG. 15 , an input analog audio signal to be recorded travels to the input circuit  113  via the apparatus input terminal  113 A. The input circuit  113  changes the input analog audio signal into a corresponding digital audio signal. In the case where the currently designated format agrees with the CD-DA format, the digital audio signal is transmitted from the input circuit  113  to the CD-DA encoder  120 A. The CD-DA encoder  120 A subjects the digital audio signal to a CIRC (Cross Interleave Reed-Solomon Code) encoding process according to the CD-DA standards. The CD-DA encoder  120 A outputs the encoding-resultant digital audio signal to the recording encoder  110  as recorded data (data to be recorded) of the CD-DA format. Specifically, the CD-DA encoder  120 A generates an error correction signal in response to the digital audio signal, and adds the error correction signal to the digital audio signal. The error correction signal uses a cross interleave Reed-Solomon code. The CD-DA encoder  120 A outputs the addition-resultant signal to the recording encoder  110 . The recording encoder  110  subjects the recorded data of the CD-DA format to the EFM modulation. The recording encoder  110  outputs the modulation-resultant signal to the laser drive section  109 . The optical bead  103  generates a laser light beam. The optical head  103  applies the laser light beam to the optical disc  101 . The laser drive section  109  controls the power or the intensity of the laser light beam in response to the output signal of the recording encoder  110  so that information corresponding to the recorded data of the CD-DA format is recorded on the optical disc  101 . Furthermore, TOC information related to the recorded data is generated, and the TOC information is recorded on an inner area of the optical disc  101 . 
   During the recording mode of operation of the apparatus of  FIG. 15 , when the currently designated format agrees with the CD-ROM format, the digital audio signal is transmitted from the input circuit  113  to the CD-ROM encoder  121 . The CD-ROM encoder  121  subjects the digital audio signal to a CD-ROM encoding process including an interleaving process according to the CD-ROM (XA) standards. The CD-ROM encoder  121  outputs the process-resultant digital audio signal to the CD-DA encoder  120 A. The CD-DA encoder  120 A subjects the output signal of the CD-ROM encoder  121  to the CIRC encoding process. The CD-DA encoder  120 A outputs the encoding-resultant digital audio signal to the recording encoder  110  as recorded data (data to be recorded) of the CD-ROM format. The recording encoder  110  subjects the recorded data of the CD-ROM format to the EFM modulation. The recording encoder  110  outputs the modulation-resultant signal to the laser drive section  109 . The optical head  103  applies the laser light beam to the optical disc  101 . The laser drive section  109  controls the power or the intensity of the laser light beam in response to the output signal of the recording encoder  110  so that information corresponding to the recorded data of the CD-ROM format is recorded on the optical disc  101 . Furthermore, TOC information related to the recorded data is generated, and the TOC information is recorded on the inner area of the optical disc  101 . 
   During the recording mode of operation of the apparatus of  FIG. 15 , when the currently designated format agrees with the CD-ROM-audio format, the digital audio signal is transmitted from the input circuit  113  to the orthogonal transform/Huffman encoder  125 . The orthogonal transform/Huffman encoder  125  subjects the digital audio signal to orthogonal transform and a Huffman encoding process to compress the digital audio signal. The orthogonal transform/Huffman encoder  125  outputs the resultant digital audio signal to the CD-ROM encoder  121 . The CD-ROM encoder  121  subjects the output signal of the orthogonal transform/Huffman encoder  125  to the CD-ROM encoding process including the interleaving process. The CD-ROM encoder  121  outputs the process-resultant digital audio signal to the CD-DA encoder  120 A. The CD-DA encoder  120 A subjects the output signal of the CD-ROM encoder  121  to the CIRC encoding process. The CD-DA encoder  120 A outputs the encoding-resultant digital audio signal to the recording encoder  110  as recorded data (data to be recorded) of the CD-ROM-audio format. The recording encoder  110  subjects the recorded data of the CD-ROM-audio format to the EFM modulation. The recording encoder  110  outputs the modulation-resultant signal to the laser drive section  109 . The optical head  103  applies the laser light beam to the optical disc  101 . The laser drive section  109  controls the power or the intensity of the laser light beam in response to the output signal of the recording encoder  110  so that information corresponding to the recorded data of the CD-ROM-audio format is recorded on the optical disc  101 . Furthermore, TOC information related to the recorded data is generated, and the TOC information is recorded on the inner area of the optical disc  101 . 
   It is assumed that the user places an optical disc  101  in the normal position within the apparatus of  FIG. 15 , and then designates the playback mode of operation of the apparatus of  FIG. 15  by actuating the operation unit  115 . The operation control unit  115  informs the CPU  117  that the playback mode of operation is currently designated. In this case, the CPU  117  starts the apparatus of  FIG. 15  to operate in the playback mode. During the playback mode of operation of the apparatus of  FIG. 15 , the servo control circuit  106  adjusts the spindle servo section  104  to optimize the rotational speed of the spindle motor  102 , that is, the rotational speed of the optical disc  101 . In addition, the servo control circuit  106  adjusts the focusing tracking servo section  105  to optimize focusing and tracking conditions of the optical head  103  relative to the optical disc  101 . On the other hand, the optical head  103  reads out information from the optical disc  101 , and outputs an RF signal representing the read-out information. The output signal of the optical head  103  is amplified by the RF amplifier  107 . The amplification-resultant signal is outputted from the RF amplifier  107  to the reproducing decoder  108 . The reproducing decoder  108  subjects the output signal of the RF amplifier  107  to the EFM demodulation, thereby recovering data corresponding to the information recorded on the optical disc  101 . The reproducing decoder  108  outputs the recovered data to the CD-DA decoder  120 B. The CO-DA decoder  120 B subjects the output signal of the reproducing decoder  108  to a CIRC decoding process (an error correction process). The CD-DA decoder  120 B outputs the decoding-resultant signal to the CPU  114  and the CD-ROM decoder  122 . 
   At a start of the playback mode of operation of the apparatus of  FIG. 15 , the CPU  117  informs the servo control circuit  106  of a desired initial position of the optical head  103  relative to the optical head  101 . The servo control circuit  106  adjusts the focusing tracking servo section  105  in response to the positional information from the CPU  117 , thereby setting the optical head  103  in a position equal to the desired initial position. In this case, the desired initial position corresponds to a starting end of an inner area of the optical disc  101 . During the start of the recording mode of operation of the apparatus of  FIG. 15 , the servo control circuit  106  adjusts the focusing tracking servo section  105  to move the optical head  103  from the initial position to read out TOC information from the inner area of the optical disc  101 . The CD-DA decoder  120 B outputs reproduced TOC information to the CPU  114 . The CPU  114  transfers the TOC information to the RAM within the CPU  117 . 
   Generally, TOC information contains four control bits Q 1 , Q 2 , Q 3 , and Q 4 . Among them, the control bit Q 2  is used as an indication of the type of a related optical disc  101 . Specifically, the control bit Q 2  being “0” indicates that the related optical disc  101  agrees with a CD-DA. The control bit Q 2  being “1” indicates that the related optical disc  101  agrees with a CD-ROM or a CD-ROM-audio. 
   It should be noted that some of CD-ROM&#39;s are devoid of TOC information. Also, some of CD-ROM-audios are devoid of TOC information. 
     FIG. 16  is a flowchart of a segment of the program in the CPU  114 . The program segment in  FIG. 16  relates to the playback mode of operation of the apparatus of  FIG. 15 . As shown in  FIG. 16 , a first step S 101  of the program segment reads out TOC information from the RAM within the CPU  117 . 
   A step S 102  following the step S 101  decides whether or not the TOC information is present, that is, whether or not the TOC information has been successfully read out from the optical disc  101 . When the TOC information is present, that is, when the TOC information has been successfully read out from the optical disc  101 , the program advances from the step S 102  to a step S 103 . Otherwise, the program advances from the step S 102  to a step S 107 . 
   The step S 103  decides whether or not the control bit Q 2  in the TOC information is “1”. When the control bit Q 2  is “1”, the program advances from the step S 103  to the step S 107 . When the control bit Q 2  is “0”, the program advances from the step S 103  to a step S 105 . In this case, it is decided that the optical disc  101  agrees with a CD-DA. 
   Data recorded on a CD-ROM or a CD-ROM-audio has a sync signal of a first type. Data recorded on a CD-DA has a sync signal of a second type different from the first type. The step S 103  may decide whether or not a sync signal of the first type is present in reproduced data. In this case, when a sync signal of the first type is not present, it is decided that the optical disc  101  agrees with a CD-DA. 
   The step S 105  controls the switches  124  and  128  so that the movable contact of the switch  124  will connect with the fixed contact “b” thereof while the movable contact of the switch  128  will connect with the fixed contact “d” thereof. In this case, the CD-DA decoder  120 B is connected to the output circuit  112  while the CD-ROM decoder  122  and the orthogonal transform/Huffman decoder  126  are disconnected from the output circuit  112 . 
   A step S 106  following the step S 105  controls the CPU  117  so that information will be reproduced from first and later tracks on the optical disc  101 . In this case, the CD-DA decoder  120 B outputs reproduced data to the output circuit  112 . After the step S 106 , the current execution cycle of the program segment ends. 
   The step S 107  controls the CPU  117  so that information will be reproduced from the first track on the optical disc  101 . The step S 107  receives reproduced data from the CD-DA decoder  120 B which represents the first-track information. 
   When the optical disc  101  agrees with a CD-ROM-audio, the first-track information has CD-ROM-audio code words rather than CD-ROM code words. When the optical disc  101  agrees with a CD-ROM, the first-track information has CD-ROM code words rather than CD-ROM-audio code words. 
   A step S 108  subsequent to the step S 107  decides whether or not the first-track information has CD-ROM-audio code words. When the first-track information has CD-ROM-audio code words, the program advances from the step S 108  to a step S 109 . In this case, it is decided that the optical disc  101  agrees with a CD-ROM-audio. When the first-track information does not have any CD-ROM-audio code words, the program advances from the step S 108  to a step S 117 . 
   The step S 109  controls the switch  124  so that the movable contact of the switch  124  will connect with the fixed contact “a” thereof. In this case, the orthogonal transform/Huffman decoder  126  is connected to the CD-ROM decoder  122 . 
   A step S 111  following the step S 109  controls the CPU  117  so that check data will be read out from a given track on the optical disc  101 . In this case, the CD-DA decoder  120 B outputs reproduced check data to the CD-ROM decoder  122 . The CD-ROM decoder  122  subjects the reproduced check data to a CD-ROM decoding process including a de-interleaving process (an inverse interleaving process). The CD-ROM decoder  122  outputs the process-resultant data to the orthogonal transform/Huffman decoder  126 . The orthogonal transform/Huffman decoder  126  subjects the output signal of the CD-ROM decoder  122  to inverse orthogonal transform and a Huffman decoding process. The orthogonal transform/Huffman decoder  126  outputs the resultant data to the CPU  114  as decoding-resultant data corresponding to the reproduced check data. The step S 111  receives the decoding-resultant data from the orthogonal transform/Huffman decoder  126  which corresponds to the reproduced check data. 
   A step S 113  subsequent to the step S 111  decides whether or not the decoding-resultant data corresponding to the reproduced check data is normal. When the decoding-resultant data is normal, the program advances from the step S 113  to a step S 115 . Otherwise, the program advances from the step S 113  to a step S 126 . 
   The step S 115  controls the switch  128  so that the movable contact of the switch  128  will connect with the fixed contact “c” thereof. In this case, the orthogonal transform/Huffman decoder  126  is connected to the output circuit  112 . 
   A step S 116  following the step S 115  controls the CPU  117  so that information will be reproduced from second and later tracks on the optical disc  101 . In this case, the CD-DA decoder  120 B outputs reproduced data to the CD-ROM decoder  122 . The CD-ROM decoder  122  subjects the reproduced data to the CD-ROM decoding process including the de-interleaving process. The CD-ROM decoder  122  outputs the process-resultant data to the orthogonal transform/Huffman decoder  126 . The orthogonal transform/Huffman decoder  126  subjects the output signal of the CD-ROM decoder  122  to the inverse orthogonal transform and the Huffman decoding process. The orthogonal transform/Huffman decoder  126  outputs the resultant data to the output circuit  112 . After the step S 116 , the current execution cycle of the program segment ends. 
   The step S 117  decides whether or not the first-track information has CD-ROM code words. When the first-track information has CD-ROM code words, the program advances from the step S 117  to a step S 118 . In this case, it is decided that the optical disc  101  agrees with a CD-ROM. When the first-track information does not have any CD-ROM code words, the program advances from the step S 117  to the step S 126 . 
   The step S 118  controls the switches  124  and  128  so that the movable contact of the switch  124  will connect with the fixed contact “a” thereof while the movable contact of the switch  128  will connect with the fixed contact “d” thereof. In this case, the CD-ROM decoder  122  is connected to the output circuit  112  while the CD-DA decoder  120 B and the orthogonal transform/Huffman decoder  126  are disconnected from the output circuit  112 . 
   A step S 125  following the step S 118  controls the CPU  117  so that information will be reproduced from the first and later tracks on the optical disc  101 . In this case, the CD-DA decoder  120 B outputs reproduced data to the CD-ROM decoder  122 . The CD-ROM decoder  122  subjects the reproduced data to the CD-ROM decoding process including the de-interleaving process. The CD-ROM decoder  122  outputs the process-resultant data to the output circuit  112 . After the step S 125 , the current execution cycle of the program segment ends. 
   The step S 126  controls the CPU  117  so that the CPU  117  will output a given display signal to the display unit  116 . The given display signal is indicated by the display unit  116 . The given display signal represents that information can not be normally reproduced from the optical disc  101 . In other words, the given display signal represents a failure of the reproduction of information from the optical disc  101 . After the step S 126 , the current execution cycle of the program segment ends. 
   It should be noted that the CD-ROM encoder  121  and the CD-ROM decoder  122  may be replaced by a DVD encoder (a DVD packing encoder) and a DVD decoder (a DVD unpacking decoder), respectively. In this case, the step S 117  in  FIG. 16  is modified to refer to MPEG code words rather than CD-ROM code words. 
   Sixth Embodiment 
     FIG. 17  shows a sixth embodiment of this invention which is similar to the embodiment of  FIG. 15  except for the following design changes. The embodiment of  FIG. 17  includes a CPU  114 A instead of the CPU  114  in  FIG. 15 . The embodiment of  FIG. 17  includes a switch  128 A instead of the switch  128  in  FIG. 15 . The embodiment of  FIG. 17  includes an MPEG decoder  129 . The embodiment of  FIG. 17  includes an input circuit  113 B instead of the input circuit  113  in  FIG. 15 . The embodiment of  FIG. 17  is able to handle an optical disc  101  which can be selected from among various discs such as a CD-DA, a CD-ROM-audio, and a video-CD. 
   A first input side of the input circuit  113 B is connected to an apparatus input terminal  113 C. A second input side of the input circuit  113 B is connected to an apparatus input terminal  113 D. The output side of the input circuit  113 B is connected to the movable contact of the switch  127 . 
   During the recording mode of operation of the apparatus of  FIG. 17  for a video-CD, an input analog audio signal is fed to the input circuit  113 B via the apparatus input terminal  113 C. In addition, an input analog video signal is fed to the input circuit  113 B via the apparatus input terminal  113 D. The input circuit  113 B has a first A/D converter which changes the input analog audio signal into a corresponding digital audio signal. The input circuit  113 B has a second A/D converter which changes the input analog video signal into a corresponding digital video signal. The input circuit  113 B has a section which combines the digital audio signal and the digital video signal into a composite digital signal. The input circuit  113 B outputs the composite digital signal to the movable contact of the switch  127 . The CPU  114  controls the switches  123  and  127  so that the output signal of the input circuit  113 B will bypass the orthogonal transform/Huffman encoder  125  and will travel to the CD-ROM encoder  121 . 
   The switch  128 A has a movable contact and fixed contacts “c”, “d”, and “j”. The switch  128 A has a control terminal. The switch  128 A is changeable among four different states in response to a signal fed to the control terminal. When the switch  128 A assumes a first state, the movable contact thereof connects with the fixed contact “c” thereof and disconnects from the fixed contact “d” and “j” thereof. When the switch  128 A assumes a second state, the movable contact thereof connects with the fixed contact “d” thereof and disconnects from the fixed contacts “c” and “j” thereof. When the switch  128 A assumes a third state, the movable contact thereof connects with the fixed contact “j” thereof and disconnects from the fixed contacts “c” and “d” thereof. When the switch  128 A assumes a fourth state, the movable contact thereof connects with none of the fixed contacts “c”, “d”, and “j” thereof. The control terminal of the switch  128 A is connected to the CPU  114 A. The fixed contact “c” of the switch  128 A leads from the output side of the orthogonal transform/Huffman decoder  126 . The fixed contact “d” of the switch  128 A leads from the movable contact of the switch  124 . The fixed contact “j” of the switch  128 A leads from the output side of the MPEG decoder  129 . The movable contact of the switch  128 A leads to the input side of the output circuit  112 . The input side of the MPEG decoder  129  leads from the movable contact of the switch  124 . The output side of the MPEG decoder  129  is connected to the CPU  114 A. 
     FIG. 18  is a flowchart of a segment of a program in the CPU  114 A. The program segment in  FIG. 18  is similar to the program segment in  FIG. 16  except for the following design changes. With reference to  FIG. 18 , a step S 117 A which replaces the step S 117  in  FIG. 16  decides whether or not the first-track information has video-CD code words. When the first-track information has video-CD code words, the program advances from the step S 117 A to a step S 118 A. In this case, it is decided that the optical disc  101  agrees with a video-CD. When the first-track information does not have any video-CD code words, the program advances from the step S 117 A to the step S 126 . 
   The step S 118 A controls the switch  124  so that the movable contact of the switch  124  will connect with the fixed contact “a” thereof. In this case, the MPEG decoder  129  is connected to the CD-ROM decoder  122 . 
   A step S 120 A following the step S 118 A controls the CPU  117  so that information will be read out from a second track on the optical disc  101 . In this case, the CD-DA decoder  120 B outputs reproduced data to the CD-ROM decoder  122  which corresponds to the second-track information. The CD-ROM decoder  122  subjects the reproduced data to the CD-ROM decoding process including the de-interleaving process. The CD-ROM decoder  122  outputs the process-resultant data to the MPEG decoder  129 . The MPEG decoder  129  subjects the output signal of the CD-ROM decoder  122  to an MPEG decoding process. The MPEG decoder  129  outputs the decoding-resultant data to the CPU  114 A which corresponds to the second-track information. The step S 120 A receives the decoding-resultant data from the MPEG decoder  129  which corresponds to the second-track information. 
   A step S 122 A subsequent to the step S 120 A decides whether or not the decoding-resultant data corresponding to the second-track information is normal. When the decoding-resultant data is normal, the program advances from the step S 122 A to a step S 124 A. Otherwise, the program advances from the step S 122  to the step S 126 . 
   The step S 124 A controls the switch  128 A so that the movable contact of the switch  128 A will connect with the fixed contact “j” thereof. In this case, the MPEG decoder  129  is connected to the output circuit  112 . 
   A step S 125 A following the step S 124 A controls the CPU  117  so that information will be reproduced from second and later tracks on the optical disc  101 . In this case, the CD-DA decoder  120 B outputs reproduced data to the CD-ROM decoder  122 . The CD-ROM decoder  122  subjects the reproduced data to the CD-ROM decoding process including the de-interleaving process. The CD-ROM decoder  122  outputs the process-resultant data to the MPEG decoder  129 . The MPEG decoder  129  subjects the output signal of the CD-ROM decoder  122  to the MPEG decoding process. The MPEG decoder  129  outputs the decoding-resultant data to the output circuit  112 . After the step S 125 A, the current execution cycle of the program segment ends. 
   It should be noted that the CD-ROM encoder  121  and the CD-ROM decoder  122  may be replaced by a DVD encoder (a DVD packing encoder) and a DVD decoder (a DVD unpacking decoder), respectively. In this case, the step S 117 A in  FIG. 18  is modified to refer to MPEG code words rather than video-CD code words. 
   Seventh Embodiment 
     FIG. 19  shows a seventh embodiment of this invention which is similar to the embodiment of  FIG. 15  except for the following design changes. The embodiment of  FIG. 19  includes an orthogonal transform encoder  125 A instead of the orthogonal transform/Huffman encoder  125  in  FIG. 15 . The embodiment of  FIG. 19  includes an orthogonal transform decoder  126 A instead of the orthogonal transform/Huffman decoder  126  in  FIG. 15 . 
   The orthogonal transform encoder  125 A implements only orthogonal transform on received data. The orthogonal transform decoder  126 A implements only inverse orthogonal transform on received data. 
   It should be noted that the CD-ROM encoder  121  and the CD-ROM decoder  122  may be replaced by a DVD encoder (a DVD packing encoder) and a DVD decoder (a DVD unpacking decoder), respectively. 
   Eighth Embodiment 
     FIG. 20  shows an eighth embodiment of this invention which is similar to the embodiment of  FIG. 17  except for the following design changes. The embodiment of  FIG. 20  includes an orthogonal transform encoder  125 A instead of the orthogonal transform/Huffman encoder  125  in  FIG. 17 . The embodiment of  FIG. 20  includes an orthogonal transform decoder  126 A instead of the orthogonal transform/Huffman decoder  126  in  FIG. 17 . 
   The orthogonal transform encoder  125 A implements only orthogonal transform on received data. The orthogonal transform decoder  126 A implements only inverse orthogonal transform on received data. 
   It should be noted that the CD-ROM encoder  121  and the CD-ROM decoder  122  may be replaced by a DVD encoder (a DVD packing encoder) and a DVD decoder (a DVD unpacking decoder), respectively. 
   Ninth Embodiment 
     FIG. 21  shows a ninth embodiment of this invention which is similar to the embodiment of  FIG. 15  except for the following design changes. The embodiment of  FIG. 21  includes a Huffman encoder  125 B instead of the orthogonal transform/Huffman encoder  125  in  FIG. 15 . The embodiment of  FIG. 21  includes a Huffman decoder  126 B instead of the orthogonal transform/Huffman decoder  126  in  FIG. 15 . 
   The Huffman encoder  125 B implements only a Huffman encoding process on received data. The Huffman decoder  126 B implements only a Huffman decoding process on received data. 
   It should be noted that the CD-ROM encoder  121  and the CD-ROM decoder  122  may be replaced by a DVD encoder (a DVD packing encoder) and a DVD decoder (a DVD unpacking decoder), respectively. 
   Tenth Embodiment 
     FIG. 22  shows a tenth embodiment of this invention which is similar to the embodiment of  FIG. 17  except for the following design changes. The embodiment of  FIG. 22  includes a Huffman encoder  125 B instead of the orthogonal transform/Huffman encoder  125  in  FIG. 17 . The embodiment of  FIG. 22  includes a Huffman decoder  126 B instead of the orthogonal transform/Huffman decoder  126  in  FIG. 17 . 
   The Huffman encoder  125 B implements only a Huffman encoding process on received data. The Huffman decoder  126 B implements only a Huffman decoding process on received data. 
   The embodiment of  FIG. 22  includes a switch  127 A instead of the switch  127  in  FIG. 17 . The embodiment of  FIG. 22  includes a CPU  114 B instead of the CPU  114 A in  FIG. 17 . The embodiment of  FIG. 22  includes an MPEG decoder  130 . 
   The switch  127 A has a movable contact and fixed contacts “g”, “h”, and “k”. The switch  127 A has a control terminal. The switch  127 A is changeable among four different states in response to a signal fed to the control terminal. When the switch  127 A assumes a first state, the movable contact thereof connects with the fixed contact “g” thereof and disconnects from the fixed contacts “h” and “k” thereof. When the switch  127 A assumes a second state, the movable contact thereof connects with the fixed contact “h” thereof and disconnects from the fixed contacts “g” and “k” thereof. When the switch  127 A assumes a third state, the movable contact thereof connects with the fixed contact “k” thereof and disconnects from the fixed contacts “g” and “h” thereof. When the switch  127 A assumes a fourth state, the movable contact thereof connects with none of the fixed contacts “g”, “h”, and “k” thereof. The control terminal of the switch  127 A is connected to the CPU  114 B. The fixed contact “g” of the switch  127 A leads to the movable contact of the switch  123 . The fixed contact “h” of the switch  127 A leads to the input side of the Huffman encoder  125 B. The fixed contact “k” of the switch  127 A leads to the input side of the MPEG encoder  130 . The movable contact of the switch  127 A leads from the output side of the input circuit  113 B. The output side of the MPEG encoder  130  is connected to the movable contact of the switch  123 . 
   It is assumed that the user designates the recording mode of operation of the apparatus of  FIG. 22  by actuating the operation unit  115 . In this case, the user also designates the format by actuating the operation unit  115 . Generally, the designated format corresponds to the standards of an optical disc  101  set in the normal position within the apparatus of  FIG. 22 . The operation unit  115  informs the CPU  117  that the recording mode of operation is currently designated. Also, the operation unit  115  informs the CPU  117  of the currently designated format. The CPU  117  transfers the information of the currently designated operation mode and the currently designated format to the CPU  114 B. When the currently designated format agrees with the video-CD format, the CPU  114 B controls the switches  123  and  127 A so that the movable contact of the switch  123  connects with the fixed contact “f” thereof and the movable contact of the switch  127 A connects with the fixed contact “k” thereof. Therefore, the MPEG encoder  130  is connected to the input circuit  113 B while the Huffman encoder  125 B is disconnected from the input circuit  113 B. In this case, the digital signal is transmitted from the input circuit  113 B to the MPEG encoder  130 . The MPEG encoder  130  subjects the digital signal to an MPEG encoding process to compress the digital signal. The MPEG encoder  130  outputs the resultant digital signal to the CD-ROM encoder  121 . The CD-ROM encoder  121  subjects the output signal of the MPEG encoder  130  to the CD-ROM encoding process including the interleaving process. The CD-ROM encoder  121  outputs the process-resultant digital signal to the CD-DA encoder  120 A. The CD-DA encoder  120 A subjects the output signal of the CD-ROM encoder  121  to the CIRC encoding process. The CD-DA encoder  120 A outputs the encoding-resultant digital signal to the recording encoder  110  as recorded data (data to be recorded) of the video-CD format. The recording encoder  110  subjects the recorded data of the video-CD format to the EFM modulation. The recording encoder  110  outputs the modulation-resultant signal to the laser drive section  109 . The optical head  103  applies the laser light beam to the optical disc  101 . The laser drive section  109  controls the power or the intensity of the laser light beam in response to the output signal of the recording encoder  110  so that information corresponding to the recorded data of the video-CD format is recorded on the optical disc  101 . Furthermore, TOC information related to the recorded data is generated, and the TOC information is recorded on the inner area of the optical disc  101 . 
   It should be noted that the CD-ROM encoder  121  and the CD-ROM decoder  122  may be replaced by a DVD encoder (a DVD packing encoder) and a DVD decoder (a DVD unpacking decoder), respectively. 
   Eleventh Embodiment 
     FIG. 23  shows an eleventh embodiment of this invention which is similar to the embodiment of  FIG. 15  except for the following design changes. The embodiment of  FIG. 23  includes a CPU  114 D instead of the CPU  114  in  FIG. 15 . The CPU  114 D is connected to the CD-DA encoder  120 A. The embodiment of  FIG. 23  includes a compression encoder  125 C, an expansion decoder  126 C, and switches  127 B and  128 B. The embodiment of  FIG. 23  is able to handle an optical disc  101  which can be selected from among various discs such as a CD-DA and a CD-ROM-audio. 
   The switch  127 B has a movable contact and fixed contacts “g”, “h 1 ”, “h 2 ”, and “h 3 ”. The switch  127 B has a control terminal. The switch  127 B is changeable among five different states in response to a signal fed to the control terminal. When the switch  127 B assumes a first state, the movable contact thereof connects with the fixed contact “g” thereof and disconnects from the fixed contacts “h 1 ”, “h 2 ”, and “h 3 ” thereof. When the switch  127 B assumes a second state, the movable contact thereof connects with the fixed contact “h 1 ” thereof and disconnects from the fixed contacts “g”, “h 2 ”, and “h 3 ” thereof. When the switch  127 B assumes a third state, the movable contact thereof connects with the fixed contact “h 2 ” thereof and disconnects from the fixed contacts “g”, “h 1 ”, and “h 3 ” thereof. When the switch  127 B assumes a fourth state, the movable contact thereof connects with the fixed contact “h 3 ” thereof and disconnects from the fixed contacts “g”, “h 1 ”, and “h 2 ” thereof when the switch  127 B assumes a fifth state, the movable contact thereof connects with none of the fixed contacts “g”, “h 1 ”, “h 2 ”, and “h 3 ” thereof. The control terminal of the switch  127 B is connected to the CPU  114 D. The fixed contact “g” of the switch  127 B leads to the input side of the CD-ROM encoder  121 . The fixed contact “h 1 ” of the switch  127 B leads to a first input side of the compression encoder  125 C. The fixed contact “h 2 ” of the switch  127 B leads to a second input side of the compression encoder  125 C. The fixed contact “h 3 ” of the switch  127 B leads to a third input side of the compression encoder  125 C. The movable contact of the switch  127 B leads from the output side of the input circuit  113 . The output side of the compression encoder  125 C is connected to the input side of the CD-ROM encoder  121 . 
   The switch  128 B has a movable contact and fixed contacts “c 1 ”, “c 2 ”, “c 3 ”, and “d”. The switch  128 B has a control terminal. The switch  128 B is changeable among five different states in response to a signal fed to the control terminal. When the switch  128 B assumes a first state, the movable contact thereof connects with the fixed contact “c 1 ” thereof and disconnects from the fixed contact “c 2 ”, “c 3 ”, and “d” thereof. When the switch  128 B assumes a second state, the movable contact thereof connects with the fixed contact “c 2 ” thereof and disconnects from the fixed contacts “c 1 ”, “c 3 ”, and “d” thereof. When the switch  128 B assumes a third state, the movable contact thereof connects with the fixed contact “c 3 ” thereof and disconnects from the fixed contacts “c 1 ”, “c 2 ”, and “d” thereof. When the switch  128 B assumes a fourth state, the movable contact thereof connects with the fixed contact “d” thereof and disconnects from the fixed contacts “c 1 ”, “c 2 ”, and “c 3 ” thereof. When the switch  128 B assumes a fifth state, the movable contact thereof connects with none of the fixed contacts “c 1 ”, “c 2 ”, “c 3 ”, and “d” thereof. The control terminal of the switch  128 B is connected to the CPU  114 D. The fixed contact “c 1 ” of the switch  128 B leads from a first output side of the expansion decoder  126 C. The fixed contact “c 2 ” of the switch  128 B leads from a second output side of the expansion decoder  126 C. The fixed contact “c 3 ” of the switch  128 B leads from a third output side of the expansion decoder  126 C. The fixed contact “d” of the switch  128 B leads from the output side of the CD-ROM decoder  122 . The movable contact of the switch  128 B leads to the input side of the output circuit  112 . In addition, the movable contact of the switch  128 B is connected to the CPU  114 D. The input side of the compression decoder  126 C is connected to the output side of the CD-ROM decoder  122 . 
   As shown in  FIG. 24 , the compression encoder  125 C includes an orthogonal transform encoder  125 P, and Huffman encoders  125 Q and  125 R. The input side of the orthogonal transform encoder  125 P is connected to the fixed contact “h 1 ” of the switch  127 B. The output side of the orthogonal transform encoder  125 P is connected to the input side of the CD-ROM encoder  121 . The input side of the Huffman encoder  125 Q is connected to the fixed contact “h 2 ” of the switch  127 B. The output side of the Huffman encoder  125 Q is connected to the input side of the orthogonal transform encoder  125 P. The input side of the Huffman encoder  125 R is connected to the fixed contact “h 3 ” of the switch  127 B. The output side of the Huffman encoder  125 R is connected to the input side of the CD-ROM encoder  121 . 
   As shown in  FIG. 25 , the expansion decoder  126 C includes an orthogonal transform decoder  126 P, and Huffman decoders  126 Q and  126 R. The input side of the orthogonal transform decoder  126 P is connected to the output side of the CD-ROM decoder  122 . The output side of the orthogonal transform decoder  126 P is connected to the fixed contact “c 1 ” of the switch  128 B. The input side of the Huffman decoder  126 Q is connected to the output side of the orthogonal transform decoder  126 P. The output side of the Huffman decoder  126 Q is connected to the fixed contact “c 2 ” of the switch  128 B. The input side of the Huffman decoder  126 R is connected to the output side of the CD-ROM decoder  122 . The output side of the Huffman decoder  126 R is connected to the fixed contact “c 3 ” of the switch  128 B. 
   The button in the operation unit  115  can also be used in selecting and designating one out of three different signal processing types, that is, first, second, and third processing types. 
   It is assumed that the user designates the recording mode of operation of the apparatus of  FIG. 23  by actuating the operation unit  115 . In this case, the user also designates the format and the processing type by actuating the operation unit  115 . Generally, the designated format corresponds to the standards of an optical disc  101  set in the normal position within the apparatus of  FIG. 23 . The operation unit  115  informs the CPU  117  that the recording mode of operation is currently designated. Also, the operation unit  115  informs the CPU  117  of the currently designated format and the currently designated processing type. The CPU  117  transfers the information of the currently designated operation mode, the currently designated format, and the currently designated processing type to the CPU  114 D. When the currently designated format agrees with the CD-ROM format, the CPU  114 D controls the switch  127 B so that the movable contact of the switch  127 B connects with the fixed contact “g” thereof. Therefore, the CD-ROM encoder  121  is connected to the input circuit  113  while the compression encoder  125 C is disconnected from the input circuit  113 . In this case, the output signal of the input circuit  113  travels the CD-ROM encoder  121  while bypassing the compression encoder  125 C. The CD-ROM encoder  121  subjects the output signal of the input circuit  113  to the CD-ROM encoding process including the interleaving process. The CD-ROM encoder  121  outputs the process-resultant digital signal to the CD-DA encoder  120 A. The CD-DA encoder  120 A subjects the output signal of the CD-ROM encoder  121  to the CIRC encoding process. The CD-DA encoder  120 A outputs the encoding-resultant digital signal to the recording encoder  110  as recorded data (data to be recorded) of the CD-ROM format. The recording encoder  110  subjects the recorded data of the CD-ROM format to the EFM modulation. The recording encoder  110  outputs the modulation-resultant signal to the laser drive section  109 . The optical head  103  applies the laser light beam to the optical disc  101 . The laser drive section  109  controls the power or the intensity of the laser light beam in response to the output signal of the recording encoder  110  so that information corresponding to the recorded data of the CD-ROM format is recorded on the optical disc  101 . Furthermore, TOC information related to the recorded data is generated, and the TOC information is recorded on the inner area of the optical disc  101 . 
   A consideration will be given of the case where the user designates the recording mode of operation of the apparatus of  FIG. 23  and also designates the format and the processing type. When the designated format agrees with the CD-ROM-audio format and the designated processing type agrees with the first processing type, the CPU  114 D controls the switch  127 B so that the movable contact of the switch  127 B connects with the fixed contact “h 1 ” thereof. Therefore, the output signal of the input circuit  113  travels the compression encoder  125 C via the fixed contact “h 1 ” of the switch  127 B. In this case, the orthogonal transform encoder  125 P in the compression encoder  125 C subjects the output signal of the input circuit  113  to a data-compression encoding process using orthogonal transform. The orthogonal transform encoder  125 P in the compression encoder  125 C outputs the resultant signal to the CD-ROM encoder  121 . The CD-ROM encoder  121  subjects the output signal of the compression encoder  125 C to the CD-ROM encoding process including the interleaving process. The CD-ROM encoder  121  outputs the process-resultant digital signal to the CD-DA encoder  120 A. The CD-DA encoder  120 A subjects the output signal of the CD-ROM encoder  121  to the CIRC encoding process. The CD-DA encoder  120 A outputs the encoding-resultant digital signal to the recording encoder  110  as recorded data (data to be recorded) of the CD-ROM-audio format. The recording encoder  110  subjects the recorded data of the CD-ROM-audio format to the EFM modulation. The recording encoder  110  outputs the modulation-resultant signal to the laser drive section  109 . The optical head  103  applies the laser light beam to the optical disc  101 . The laser drive section  109  controls the power or the intensity of the laser light beam in response to the output signal of the recording encoder  110  so that information corresponding to the recorded data of the CD-ROM-audio format is recorded on the optical disc  101 . Furthermore, TOC information related to the recorded data is generated, and the TOC information is recorded on the inner area of the optical disc  101 . The CPU  114 D controls the CD-DA encoder  120 A so that an information piece representing the use of the first processing type will be added to the TOC information. 
   A further consideration will be given of the case where the user designates the recording mode of operation of the apparatus of  FIG. 23  and also designates the format and the processing type. When the designated format agrees with the CD-ROM-audio format and the designated processing type agrees with the second processing type, the CPU  114 D controls the switch  127 B so that the movable contact of the switch  127 B connects with the fixed contact “h 2 ” thereof. Therefore, the output signal of the input circuit  113  travels the compression encoder  125 C via the fixed contact “h 2 ” of the switch  127 B. In this case, the Huffman encoder  125 Q in the compression encoder  125 C subjects the output signal of the input circuit  113  to a Huffman encoding process. The Huffman encoder  125 Q outputs the resultant signal to the orthogonal transform encoder  125 P in the compression encoder  125 C. The orthogonal transform encoder  125 P subjects the output signal of the Huffman encoder  125 Q to the data-compression encoding process using the orthogonal transform. The orthogonal transform encoder  125 P in the compression encoder  125 C outputs the resultant signal to the CD-ROM encoder  121 . The CD-ROM encoder  121  subjects the output signal of the compression encoder  125 C to the CD-ROM encoding process including the interleaving process. The CD-ROM encoder  121  outputs the process-resultant digital signal to the CD-DA encoder  120 A. The CD-DA encoder  120 A subjects the output signal of the CD-ROM encoder  121  to the CIRC encoding process. The CD-DA encoder  120 A outputs the encoding-resultant digital signal to the recording encoder  110  as recorded data (data to be recorded) of the CD-ROM-audio format. The recording encoder  110  subjects the recorded data of the CD-ROM-audio format to the EFM modulation. The recording encoder  110  outputs the modulation-resultant signal to the laser drive section  109 . The optical head  103  applies the laser light beam to the optical disc  101 . The laser drive section  109  controls the power or the intensity of the laser light beam in response to the output signal of the recording encoder  110  so that information corresponding to the recorded data of the CD-ROM-audio format is recorded on the optical disc  101 . Furthermore, TOC information related to the recorded data is generated, and the TOC information is recorded on the inner area of the optical disc  101 . The CPU  114 D controls the CD-DA encoder  120 A so that an information piece representing the use of the second processing type will be added to the TOC information. 
   A still further consideration will be given of the case where the user designates the recording mode of operation of the apparatus of  FIG. 23  and also designates the format and the processing type. When the designated format agrees with the CD-ROM-audio format and the designated processing type agrees with the third processing type, the CPU  114 D controls the switch  127 B so that the movable contact of the switch  127 B connects with the fixed contact “h 3 ” thereof. Therefore, the output signal of the input circuit  113  travels the compression encoder  125 C via the fixed contact “h 3 ” of the switch  127 B. In this case, the Huffman encoder  125 R in the compression encoder  125 C subjects the output signal of the input circuit  113  to a Huffman encoding process. The Huffman encoder  125 R in the compression encoder  125 C outputs the resultant signal to the CD-ROM encoder  121 . The CD-ROM encoder  121  subjects the output signal of the compression encoder  125 C to the CD-ROM encoding process including the interleaving process. The CD-ROM, encoder  121  outputs the process-resultant digital signal to the CD-DA encoder  120 A. The CD-DA encoder  120 A subjects the output signal of the CD-ROM encoder  121  to the CIRC encoding process. The CD-DA encoder  120 A outputs the encoding-resultant digital signal to the recording encoder  110  as recorded data (data to be recorded) of the CD-ROM-audio format. The recording encoder  110  subjects the recorded data of the CD-ROM-audio format to the EFM modulation. The recording encoder  110  outputs the modulation-resultant signal to the laser drive section  109 . The optical head  103  applies the laser light beam to the optical disc  101 . The laser drive section  109  controls the power or the intensity of the laser light beam in response to the output signal of the recording encoder  110  so that information corresponding to the recorded data of the CD-ROM-audio format is recorded on the optical disc  101 . Furthermore, TOC information related to the recorded data is generated, and the TOC information is recorded on the inner area of the optical disc  101 . The CPU  114 D controls the CD-DA encoder  120 A so that an information piece representing the use of the third processing type will be added to the TOC information. 
     FIG. 26  is a flowchart of a segment of a program in the CPU  114 D. The program segment in  FIG. 26  relates to the playback mode of operation of the apparatus of  FIG. 23 . As shown in  FIG. 26 , a first step S 201  of the program segment reads out TOC information from the RAM within the CPU  117 . 
   A step S 207  following the step S 201  controls the CPU  117  so that information will be reproduced from the first track on the optical disc  101 . The step S 207  receives reproduced data from the CD-DA decoder  120 B which represents the first-track information. 
   A step S 208  subsequent to the step S 207  decides whether or not the first-track information has CD-ROM-audio code words. When the first-track information has CD-ROM-audio code words, the program advances from the step S 208  to a step S 250 . In this case, it is decided that the optical disc  101  agrees with a CD-ROM-audio. When the first-track information does not have any CD-ROM-audio code words, the program advances from the step S 208  to a step S 217 . 
   The step S 250  decides which of the first, second, and third processing types is used by referring to the TOC information. When the first processing type is used, the program advances from the step S 250  to a step S 251 A. When the second processing type is used, the program advances from the step S 250  to a step S 251 B. When the third processing type is used, the program advances from the step S 250  to a step S 251 C. 
   The step S 251 A controls the switch  128 B so that the movable contact of the switch  128 B will connect with the fixed contact “c 1 ”. The step S 251 B controls the switch  128 B so that the movable contact of the switch  128 B will connect with the fixed contact “c 2 ”. The step S 251 C controls the switch  128 B so that the movable contact of the switch  128 B will connect with the fixed contact “c 3 ”. 
   A step S 252  following the steps S 251 A, S 251 B, and S 251 C controls the CPU  117  so that information will be reproduced from second and later tracks on the optical disc  101 . In this case, the CD-DA decoder  120 B outputs reproduced data to the CD-ROM decoder  122 . The CD-ROM decoder  122  subjects the reproduced data to the CD-ROM decoding process including the de-interleaving process. The CD-ROM decoder  122  outputs the process-resultant data to the expansion decoder  126 C. The orthogonal transform decoder  126 P in the expansion decoder  126 C subjects the output signal of the CD-ROM decoder  122  to a data-expansion decoding process using inverse orthogonal transform. The orthogonal transform decoder  126 P in the expansion decoder  126 C outputs the resultant signal to the fixed contact “c 1 ” of the switch  128 B and also the Huffman decoder  126 Q in the expansion decoder  126 C. The Huffman decoder  126 Q in the expansion decoder  126 C subjects the output signal of the orthogonal transform decoder  126 P to a Huffman decoding process. The Huffman decoder  126 Q in the expansion decoder  126 C outputs the resultant signal to the fixed contact “c 2 ” of the switch  128 B. The Huffman decoder  126 R in the expansion decoder  126 C subjects the output signal of the CD-ROM decoder  122  to a Huffman decoding process. The Huffman decoder  126 R in the expansion decoder  126 C outputs the resultant signal to the fixed contact “c 3 ” of the switch  128 B. When the movable contact of the switch  128 B connects with the fixed contact “c 1 ” thereof, the output signal of the orthogonal transform decoder  126 P in the expansion decoder  126 C travels to the output circuit  112 . When the movable contact of the switch  128 B connects with the fixed contact “c 2 ” thereof, the output signal of the Huffman decoder  126 Q in the expansion decoder  126 C travels to the output circuit  112 . When the movable contact of the switch  128 B connects with the fixed contact “c 3 ” thereof, the output signal of the Huffman decoder  126 R in the expansion decoder  126 C travels to the output circuit  112 . After the step S 252 , the current execution cycle of the program segment ends. 
   The step S 217  decides whether or not the first-track information has CD-ROM code words. When the first-track information has CD-ROM code words, the program advances from the step S 217  to a step S 224 . In this case, it is decided that the optical disc  101  agrees with a CD-ROM. When the first-track information does not have any CD-ROM code words, the program advances from the step S 217  to the step S 226 . 
   The step S 224  controls the switch  128 B so that the movable contact of the switch  128 B will connect with the fixed contact “d” thereof. In this case, the CD-ROM decoder  122  is connected to the output circuit  112  while the expansion decoder  126 C is disconnected from the output circuit  112 . 
   A step S 225  following the step S 224  controls the CPU  117  so that information will be reproduced from the first and later tracks on the optical disc  101 . In this case, the CD-DA decoder  120 B outputs reproduced data to the CD-ROM decoder  122 . The CD-ROM decoder  122  subjects the reproduced data to the CD-ROM decoding process including the de-interleaving process. The CD-ROM decoder  122  outputs the process-resultant data to the output circuit  112 . After the step S 225 , the current execution cycle of the program segment ends. 
   The step S 226  controls the CPU  117  so that the CPU  117  will output a given display signal to the display unit  116 . The given display signal is indicated by the display unit  116 . The given display signal represents that information can not be normally reproduced from the optical disc  101 . In other words, the given display signal represents a failure of the reproduction of information from the optical disc  101 . After the step S 226 , the current execution cycle of the program segment ends. 
   It should be noted that the CD-ROM encoder  121  and the CD-ROM decoder  122  may be replaced by a DVD encoder (a DVD packing encoder) and a DVD decoder (a DVD unpacking decoder), respectively. In this case, the step S 217  in  FIG. 26  is modified to refer to MPEG code words rather than CD-ROM code words. 
   Twelfth Embodiment 
     FIG. 27  shows a twelfth embodiment of this invention which is similar to the embodiment of  FIG. 23  except for the following design changes. The embodiment of  FIG. 27  includes a CPU  114 E instead of the CPU  114 D in  FIG. 23 . The embodiment of  FIG. 27  includes a switch  128 D instead of the switch  128 B in  FIG. 23 . The embodiment of  FIG. 27  includes an MPEG decoder  129 . The embodiment of  FIG. 27  is able to handle an optical disc  101  which can be selected from among various discs such as a CD-ROM-audio and a video-CD. 
   The switch  128 D has a movable contact and fixed contacts “c 1 ”, “c 2 ”, “c 3 ”, “d”, and “i”. The switch  128 D has a control terminal. The switch  128 D is changeable among six different states in response to a signal fed to the control terminal. When the switch  128 D assumes a first state, the movable contact thereof connects with only the fixed contact “c 1 ” thereof. When the switch  128 D assumes a second state, the movable contact thereof connects with only the fixed contact “c 2 ” thereof. When the switch  128 D assumes a third state, the movable contact thereof connects with only the fixed contact “c 3 ” thereof. When the switch  128 D assumes a fourth state, the movable contact thereof connects with only the fixed contact “d” thereof. When the switch  128 D assumes a fifth state, the movable contact thereof connects with only the fixed contact “i” thereof. When the switch  128 B assumes a sixth states, the movable contact thereof connects with none of the fixed contacts “c 1 ”, “c 2 ”, “c 3 ”, “d”, and “i” thereof. The control terminal of the switch  128 D is connected to the CPU  114 E. The fixed contact “c 1 ” of the switch  128 D leads from the first output side of the expansion decoder  126 C. The fixed contact “c 2 ” of the switch  128 D leads from the second output side of the expansion decoder  126 C. The fixed contact “c 3 ” of the switch  128 D leads from the third output side of the expansion decoder  126 C. The fixed contact “d” of the switch  128 D leads from the output side of the CD-ROM decoder  122 . The fixed contact “i” of the switch  128 D leads from the output side of the MPEG decoder  129 . The movable contact of the switch  128 D leads to the input side of the output circuit  112 . The input side of the MPEG decoder  129  is connected to the output side of the CD-ROM decoder  122 . The output side of the MPEG decoder  129  is connected to the CPU  114 E. 
     FIG. 28  is a flowchart of a segment of a program in the CPU  114 E. The program segment in  FIG. 28  is similar to the program segment in  FIG. 26  except for the following design changes. With reference to  FIG. 28 , a step S 217 A which replaces the step S 217  in  FIG. 26  decides whether or not the first-track information has video-CD code words. When the first-track information has video-CD code words, the program advances from the step S 217 A to a step S 220 A. In this case, it is decided that the optical disc  101  agrees with a video-CD. When the first-track information does not have any video-CD code words, the program advances from the step S 217 A to the step S 226 . 
   The step S 220 A controls the CPU  117  so that information will be read out from a second track on the optical disc  101 . In this case, the CD-DA decoder  120 B outputs reproduced data to the CD-ROM decoder  122  which corresponds to the second-track information. The CD-ROM decoder  122  subjects the reproduced data to the CD-ROM decoding process including the de-interleaving process. The CD-ROM decoder  122  outputs the process-resultant data to the MPEG decoder  129 . The MPEG decoder  129  subjects the output signal of the CD-ROM decoder  122  to an MPEG decoding process. The MPEG decoder  129  outputs the decoding-resultant data to the CPU  114 E which corresponds to the second-track information. The step S 220 A receives the decoding-resultant data from the MPEG decoder  129  which corresponds to the second-track information. 
   A step S 222 A subsequent to the step S 220 A decides whether or not the decoding-resultant data corresponding to the second-track information is normal. When the decoding-resultant data is normal, the program advances from the step S 222 A to a step S 224 A. Otherwise, the program advances from the step S 222 A to the step S 226 . 
   The step S 224 A controls the switch  128 D so that the movable contact of the switch  128 D will connect with the fixed contact “i” thereof. In this case, the MPEG decoder  129  is connected to the output circuit  112 . 
   A step S 225 A following the step S 224  controls the CPU  117  so that information will be reproduced from second and later tracks on the optical disc  101 . In this case, the CD-DA decoder  120 B outputs reproduced data to the CD-ROM decoder  122 . The CD-ROM decoder  122  subjects the reproduced data to the CD-ROM decoding process including the de-interleaving process. The CD-ROM decoder  122  outputs the process-resultant data to the MPEG decoder  129 . The MPEG decoder  129  subjects the output signal of the CD-ROM decoder  122  to the MPEG decoding process. The MPEG decoder  129  outputs the decoding-resultant data to the output circuit  112 . After the step S 225 A, the current execution cycle of the program segment ends. 
   It should be noted that the CD-ROM encoder  121  and the CD-ROM decoder  122  may be replaced by a DVD encoder (a DVD packing encoder) and a DVD decoder (a DVD unpacking decoder), respectively. In this case, the step S 217 A in  FIG. 28  is modified to refer to MPEG code words rather than video-CD code words.