JP2004288365A - Optical disk, recording method, recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new system recording medium with which high tone quality is achieved allowing reproduction even in conventional reproducing devices. <P>SOLUTION: An optical disk is formed to the constitution of a plurality of layers in which a recording layer has at least a first and a second layer. The first layer records a first digital audio signal in which a quantized bit sampled by a sampling frequency of 44.1 KHz consists of 16 bits. The second layer records a second digital audio signal having the same program as that of the first digital audio signal in which a quantized bit sampled by 2.8224 MHz consists of 1 bit. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical disk capable of recording audio data in a novel data format, and a recording method and a recording apparatus corresponding to the optical disk.

At present, a CD (compact disk), which is widely used as a high-quality sound recording medium, records digital audio data having a sampling frequency fs = 44.1 KHz and a quantization bit number = 16 bits.
By the way, with the realization of various media having a large capacity and a high transfer rate in recent years, a system for realizing higher sound quality for such a CD (hereinafter, referred to as a first generation CD) has been studied. However, in order to achieve high sound quality, the first consideration is to increase the sampling frequency.

  That is, if the sampling frequency fs = 44.1 KHz as in the case of the first generation CD, the audio signal data is limited to components in a frequency band up to approximately 20 KHz. The purpose of the present invention is to enable recording of the above audio data components and to realize recording / reproduction of audio more faithful to natural sounds.

By the way, although it is possible to construct a new CD media system using a data format in which the sampling frequency is higher than that of the first generation CD, there are various problems in practical use.
Even if a new type of CD media system is realized, practically, compatibility with the first generation CD is required.

For example, a reproducing apparatus that supports a new format CD using a data format with a higher sampling frequency is required to be able to reproduce a first-generation CD.
Conversely, when viewed from a new format CD as a recording medium, it is required that the new format CD can be reproduced by a player corresponding to the first generation CD.

However, even if the sampling frequency is simply increased to achieve high sound quality, the new system CD cannot be reproduced by a first-generation CD-compatible player, of course, and is suitable as a new system. Absent.
A player corresponding to the new system CD can reproduce the first generation CD. In this case, a decoder and a D / A converter corresponding to the first generation CD and a player corresponding to the new system CD are used. Two systems of reproduction systems are required in the digital domain, such as a decoder and a D / A converter. Of course, a clock generator must also be provided independently for each circuit system. This leads to complication of the circuit configuration of the reproducing apparatus, an increase in size, an increase in cost, and the like, and cannot be said to be appropriate.

  In view of these problems, an object of the present invention is to provide a new type of optical disk, a recording method, and a recording device that can be reproduced even by a reproduction device corresponding to a first generation CD, that is, an optical disk.

  For this reason, the optical disc has a multi-layer structure in which the recording layer has at least a first layer and a second layer, and the first layer has a first bit of 16 bits, which is a quantized bit sampled at a sampling frequency of 44.1 KHz. A digital audio signal is recorded, and a second digital audio signal having the same program as the first digital audio signal whose quantization bit sampled at 2.8224 MHz is 1 bit is recorded in the second layer. It is characterized by.

  As a recording method, a 1-bit quantized bit obtained by sampling an input analog audio signal with a ΔΣ modulation 1-bit A / D converter at n × fs (Hz) (fs is a sampling frequency, n is a positive integer) is used. Converting the digital audio signal into a digital audio signal, adding an error correction code to the 1-bit digital audio signal in which the quantized bits sampled at the nx fs (Hz) and modulating the digital audio signal, Recording a 1-bit digital audio signal having one bit of quantized bits sampled at nx fs (Hz) subjected to code addition and modulation processing in a first layer of an optical disc having a plurality of layers; The quantized bits sampled at nx fs (Hz) down-sample a 1-bit digital audio signal and the quantized bits are changed from one bit to the first bit. Generating a second digital audio signal by converting the digital audio signal into one multi-bit, reducing the generated second digital audio signal to fewer quantized bits than the first multi-bit, Recording the second digital audio signal with the reduced number on a second layer different from the first layer of the optical disc having the plurality of layers.

  As a recording device, a ΔΣ modulation means for converting an input analog audio signal into a digital audio signal in which quantization bits sampled at n × fs (Hz) (fs is a sampling frequency, n is a positive integer) is 1 bit. Signal processing means for adding and modulating an error correction code to a 1-bit digital audio signal whose quantized bits sampled at n × fs (Hz); and an error correction code for the signal processing means. Recording a 1-bit first digital audio signal having 1-bit quantized bits sampled at nx fs (Hz) on which addition and modulation processing has been performed on a first layer of an optical disc having a plurality of layers And the downsampling of a 1-bit digital audio signal whose quantized bits sampled at n × fs (Hz) output from the ΔΣ modulation means Decimation filter means for converting the quantized bits from 1 bit to a first multi-bit, and the down-sampled quantized bits output from the decimation filter means for converting the first multi-bit digital audio signal A bit mapping means for reducing the number of quantization bits to less than the first multi-bits, and a digital audio signal whose quantization bits have been reduced by the bit mapping means being different from the first layer of the optical disk having a plurality of layers; And a second recording means for recording on the second layer.

  As described above, according to the present invention, the recording layer has a multi-layer structure having at least a first layer and a second layer, and the first layer records an audio data program in a first data format, and the second layer Record a voice data program in the second data format. The audio data programs recorded on the first layer and the second layer had the same contents. That is, data recorded in, for example, the first layer, which can be read by a reproducing apparatus corresponding to the first-generation recording medium, is set to the data format of the first-generation recording medium so that it can be reproduced by an old reproducing apparatus. This makes it possible to reproduce high-quality sound by reading data of the second layer in which data of a format with high-quality sound is recorded in a reproducing apparatus compatible with the new system. As described above, according to the present invention, it is possible to obtain an effect of realizing a medium having high sound quality as a recording medium of a new system, and realizing compatibility that the medium can be used even in a conventional reproducing apparatus.

In particular, the second data format is a data format in which the sampling frequency is an integer multiple of the sampling frequency of the first data format, so that both the first generation recording medium and the recording medium of the present invention are used. Can be simplified.
Further, the second data format is a signal that is 1-bit ΔΣ modulated, so that the sampling frequency can be easily increased remarkably, and sufficient sound quality can be realized.

Hereinafter, an optical disc (recording medium) as an embodiment of the present invention will be described with reference to FIGS.
Here, as a recording medium as an example of the embodiment, a recording medium realizing higher sound quality for a first-generation CD having a sampling frequency fs = 44.1 KHz and a quantization bit number of 16 bits is used. The frequency was set to 2.8224 MHz, which is 64 times that of the first generation CD (hereinafter, “fs” is 44.1 KHz, and 2.8224 MHz is described as “64 fs”). These are digital audio signals to be recorded. Such a recording medium (CD) is hereinafter referred to as a second generation CD.

As is well known, a 1-bit ΔΣ-modulated signal can have a significantly higher sampling frequency for a data capacity or data transfer rate than a conventional PCM-modulated signal. Therefore, in the present embodiment, the sampling frequency is set to 64 fs, and in principle, it is possible to record and reproduce even high frequency components up to 1.4 MHz as data. This provides a second-generation CD whose sound quality is dramatically improved as compared with the first-generation CD.
By setting the sampling frequency of the second-generation CD to be an integral multiple of the sampling frequency of the first-generation CD, consistency with the first-generation CD system is ensured, and inconvenience is maintained in maintaining compatibility. To prevent it from occurring.

However, the second generation CD, which is an example of the recording medium according to the embodiment, not only records audio data in the format of 64 fs sampling / 1 bit ΔΣ modulation, but also audio data in the same format as the first generation CD. It is to be recorded.
For discrimination in the description, audio data in the format of 64 fs sampling / 1 bit ΔΣ modulation is called “high sampling data”, and audio data in the format of the first generation CD, which is 44.1 KHz sampling / 16 bit quantization, is referred to as “high sampling data”. It is referred to as “normal data”.

FIG. 1 shows the recording layer structure of the disc 1 as the second generation CD.
As can be seen from FIG. 1 (a), the recording layer a pit is formed in the disc 1, is a two-layer structure with the first layer L ₁ and the second layer L _2.

In order to form the disk 1 having such a two-layer structure, as shown in more detail in FIG. 1B, for example, a pit P ₂ recorded as a second layer L ₂ by a stamper on a disk substrate K made of polycarbonate is formed. Form. There to give a semi-transparent film R ₂ of the dielectric by sputtering. The translucent film R ₂ is a reflective film as the second layer L _2.
Next, an ultraviolet curable resin is poured in a thickness of about 40 μm, and is hardened by irradiating ultraviolet rays while using a stamper for forming a pit P ₁ as the first layer L ₁ . Pit P ₁ is formed, as in the first generation CD, and Al (aluminum) reflective layer R ₁ by sputtering, give a protective film H with ultraviolet curable resin.
In this way, a two-layer disc 1 as shown in FIG. 1 is formed.

Here, it is assumed that the first layer L ₁ and the second layer L ₂ exactly same music program is recorded. For example the first layer L ₁ in the music A, B, After a data of three songs that C is recorded, the second layer L ₂ to be music A, B, and data of three songs that C is recorded.
However, data recorded on the first layer L _1, based on the digital audio data as normal data, and the data to be recorded on the second layer L ₂ are as those based on the digital audio data as the high sampling data Is done.

For data to be recorded first layer L ₁ and the second layer L ₂ In this second generation CD 2, it will be described in FIG. FIG. 2 is a block diagram of a part of a recording apparatus for producing a second generation CD.
An analog audio signal as an original audio signal from the master tape is input to the terminal 10. The frequency spectrum of the analog audio signal is as shown in FIG.

This analog audio signal is converted into digital data by the ΔΣ modulation 1-bit A / D converter 11. At this time, the sampling frequency is set to 64 fs, and a digital audio signal of 64 fs / 1 bit is output. FIG. 3B shows the frequency spectrum of the digital audio signal of 64 fs / 1 bit. That is, in principle, data in the frequency band up to 32 fs can be digitized, and almost all components of the analog audio signal shown in FIG. 3A are left as digital data.
In addition, due to the noise shaping function in the ΔΣ modulation, the quantization noise components are collected on the high frequency side on the frequency axis.

  The 64 fs / 1 bit digital audio signal is supplied to the recording signal processing unit 17 and is directly modulated into a recording signal. That is, a signal of 64 fs / 1 bit is used as it is as digital audio data to be recorded. The recording signal processing unit 17 performs, for example, a modulation process for recording such as addition of an error correction code or EFM modulation, and generates a signal corresponding to pit information actually formed on the disc as a recording signal.

The recording signal is a signal to be recorded on the second layer L ₂ in the disk 1. That is, a recording signal based on digital audio data as the high sampling data by the 64fs / 1-bit format is data which is recorded as a pit P _2.

  The 64 fs / 1 bit signal output from the ΔΣ modulation 1-bit A / D converter 11 is simultaneously supplied to the decimation filter 12 and converted into 2 fs (= 88.2 KHz) / 24-bit digital data. The frequency spectrum of the digital data of 2 fs / 24 bits is as shown in FIG. That is, since the sampling frequency is reduced to 2 fs, the data components in the frequency band up to the frequency fs remain.

  Further, the data is converted into digital data of fs (= 44.1 KHz) / 24 bits by the decimation filter 13. The frequency spectrum of the digital data of fs / 24 bits is as shown in FIG. 3D, and the data component of the frequency band up to (1/2) fs is left.

  The sampling frequency is reduced to 1/64 by the decimation filters 12 and 13. However, this is not a so-called sampling rate conversion but a fully synchronized digital filter that performs 64: 1 decimation. No elements occur.

The digital data of fs / 24 bits is converted into data having a quantization bit number of 16 bits by the bit mapping unit 14 and supplied to the recording signal processing unit 15. The recording signal processing unit generates a recording signal by performing required processing such as error correction code addition and EFM modulation on the digital audio signal of fs / 16 bits.
The recording signal is a signal to be recorded on the first layer L ₁ in the disk 1. That is, a recording signal based on digital audio data as normal data according to fs / 16-bit format is data which is recorded as a pit P _1.

Thus the disk 1 not only high-quality data as the second generation CD is recorded on the second layer L _2, data corresponding to the first generation CD is recorded on the first layer L _1. Moreover, data content (music contents) recorded first layer L ₁ and the second layer L ₂ are identical.
As a result, such a disk 1 as a second-generation CD can not only perform high-quality sound reproduction by a reproduction apparatus corresponding to the second-generation CD as described later, but also can reproduce a signal corresponding to the first-generation CD. The device can also reproduce with the sound quality of the first generation CD level.

  Further, since the sampling frequency of the high sampling data is set to an integral multiple of the normal data (= first generation CD), the data recorded on the first layer of the disc 1 has lower sound quality than the first generation CD. It does not happen. In other words, for the conversion of the sampling frequency, a filter process for performing decimation by 1/64 is sufficient, and the sampling rate converter is not required, so that the jitter accompanying the rate conversion does not occur. Sound quality equivalent to directly sampling at 44.1KHz can be achieved.

Next, a reproducing operation using the disc 1 as a second generation CD will be described.
FIG. 4 shows a case where the disc 1 is reproduced by a reproduction apparatus compatible with the second generation CD.
The disk 1 is driven to rotate by a spindle motor 26.
The spindle motor 26 is driven at a CLV (constant linear velocity) by a drive signal from the motor controller 25.

  Although the spindle servo operation for CLV control by the motor controller 25 will not be described in detail, the clock CK2 from the oscillator 23 is frequency-divided by the frequency divider 24 and a predetermined value corresponding to the disk rotation speed in the second generation CD system is used. A frequency reference clock CKs is obtained, and an error signal is generated by comparing the reference clock CKs with a PLL clock CKd synchronized with the reproduced data. Then, CLV servo is executed by applying electric power to the spindle motor 26 according to the error signal. The PLL system clock CKd is generated by, for example, injecting data extracted in the high sampling data decoder 29 into a PLL circuit.

As the disk 1 is rotated, the pickup 21 irradiates the recording surface of the disk 1 with a laser beam and detects the reflected light, whereby the information by the pits formed on the disk 1 is read.
At this time, the focus of the pickup 21 is set to be the second layer L _2, and the laser light from the pickup 21 is reflected by the translucent reflection film R ₂ shown in FIG. Wavelength.
Therefore, the information as pits P ₂ in the second layer L ₂ are read from the pickup 21.

  The information read by the pickup 21 is supplied to a high sampling data decoder 29. The high-sampling data decoder 29 is a part that decodes a 64 fs / 1 bit digital audio signal from the pit information.

The oscillator 23 generates a second generation CD, that is, a clock CK2 having a frequency used for decoding high-sampling data. The clock CK2 is supplied to the high-sampling data decoder 29 and the 1-bit D / A converter 33.
Second layer pit information L ₂ extracted by the pickup 21 by decode processing by the high sampling data decoder 29, 64fs / 1-bit digital audio signal is decoded. This 64 fs / 1-bit digital audio signal is supplied to the 1-bit D / A converter 33 and is converted into an analog audio signal.
With such an operation, a very high-quality reproduced sound as a second-generation CD can be obtained from the disk 1.

FIG. 5 shows a case where the disc 1 is reproduced by a reproduction apparatus compatible with the first generation CD.
The disk 1 is driven to rotate by a spindle motor 26, and the spindle motor 26 is driven at a CLV (constant linear velocity) by a drive signal from a motor controller 25.

  As a spindle servo operation for CLV control by the motor controller 25, the clock CK1 from the oscillator 35 is frequency-divided by the frequency divider 36, and a reference clock of a predetermined frequency corresponding to the disk rotation speed in the first generation CD system. Get CKs. Then, an error signal is generated by comparing the reference clock CKs with the PLL clock CKd synchronized with the reproduction data. Then, CLV servo is executed by applying electric power to the spindle motor 26 according to the error signal. The PLL clock CKd is generated by injecting data extracted in the normal data decoder 28 into a PLL circuit.

As the disk 1 is rotated, the pickup 39 irradiates the recording surface of the disk 1 with a laser beam and detects the reflected light, whereby information based on pits formed on the disk 1 is read. Here, in the pickup 39 in such a first generation CD compatible reproduction device, the laser beam has a wavelength which passes through the reflective film R ₂ translucent shown in FIG. 1 (b), thus reflecting film R It will be reflected by ₁ .
Thus from the pickup 39 so that the information as pits P ₁ in the first layer L ₁ is read.
The information read by the pickup 21 is supplied to a normal data decoder 28. The normal data decoder 28 is a part for decoding a digital audio signal of fs / 16 bits from pit information.

A first generation CD, that is, a clock CK1 of a frequency used for decoding normal data is generated from the oscillator 35, and is supplied to the normal data decoder 28 and the D / A converter 37.
The first layer pit information L ₁ extracted by the pickup 39 by decode processing by the normal data decoder 28, the digital audio signal of fs / 16-bit are decoded. The digital audio signal of fs / 16 bits is supplied to the D / A converter 37 and is converted into an analog audio signal.
As described above, the disc 1 as a second generation CD can be reproduced even by a reproducing apparatus corresponding to the first generation CD. The sound quality of the reproduced sound in this case is exactly the same as that of the first-generation CD, and the sound quality does not deteriorate.

FIG. 6 shows a case where reproduction is performed by a reproduction apparatus that supports both the first generation CD and the second generation CD.
While the disc 1 is shown as second generation CD having a two-layer structure, the first generation CD may also be mounted, and the first generation CD, one layer of only the recording layer corresponding to the first layer L ₁ It is a structure.
The spindle motor 26 that rotates the disk 1 is driven at a CLV (constant linear velocity) by a drive signal from the motor controller 25.

  As a spindle servo operation for CLV control by the motor controller 25, the clock CK2 from the oscillator 23 is frequency-divided by the frequency divider 24 to obtain a reference clock CKs of a predetermined frequency. An error signal is generated by comparing the synchronized PLL system clock CKd. Then, CLV servo is executed by applying electric power to the spindle motor 26 according to the error signal. The PLL system clock CKd is generated in the normal data decoder 28 or the high sampling data decoder 29 by injecting the extracted data into the PLL circuit.

As the disk 1 is rotated, the pickup 21 irradiates the recording surface of the disk 1 with a laser beam and detects the reflected light, whereby the information by the pits formed on the disk 1 is read.
At this time, focus focus of the pickup 21, the focus controller 38, a state F ₂ as the second layer L _2, can be variably set to a state F ₁ serving as the first layer L _1. Therefore, when the disk 1 is a disk of the second generation CD having a two-layer structure, as illustrated, also read the second layer pit information L ₂ in high-quality data, and the first layer L ₁ of the pit Information can also be read. When the disc 1 is a first-generation CD, it goes without saying that the pit data of the first layer is focused.

The information read by the pickup 21 is supplied to a high sampling data decoder 29 or a normal data decoder 28.
The clock CK2 from the oscillator 23 has a frequency for decoding high sampling data, and this clock CK2 is supplied to the high sampling data decoder 29.
The clock CK2 from the oscillator 23 is converted into a clock CK1 having a frequency used for decoding normal data by the frequency divider 27, and is supplied to the normal data decoder 28.
From the high sampling data decoder 29 is the sampling frequency 64fs, 1-bit digital audio signal is decoded output is supplied to a T ₂ terminal of the switch 32.

A 16-bit digital audio signal having a sampling frequency of fs is decoded and output from the normal data decoder 28, and is converted into a digital audio signal having a sampling frequency of 64fs and a 1-bit signal by the oversampling digital filter 30 and the ΔΣ modulation circuit 31. . And fed to a T ₁ terminal of switch 32.

  The output of the switch 32 is supplied to a 1-bit D / A converter 33 to be converted into an analog audio signal, which is output from a terminal 34. The 1-bit D / A converter 33 is supplied with the clock CK2 from the oscillator 23, that is, the same clock as the clock for the high sampling data decoder 29.

The disk determination unit 22 is a unit that determines whether the mounted disk 1 is a first-generation CD or a second-generation CD. This determination can be made by reading the TOC data recorded on the innermost peripheral side of the disk.
The disc discrimination unit 22 controls the switch 32, the frequency division ratio of the frequency divider 24, and the focus controller 38 according to the discrimination result.

In such a reproducing apparatus, first, consider a case where the disk 1 to be reproduced is a second-generation CD having a two-layer structure as shown in the figure.
First, when the disc discrimination unit 22 discriminates from the TOC data of the disc 1 that the disc is the second generation CD, the frequency division ratio in the frequency divider 24 is set to a value corresponding to the second generation CD. Also it connects the switch 32 to T ₂ terminal. Further by the focus controller 38, to a state F ₂ to set the focus to the second layer L _2.

By setting the frequency division ratio in the frequency divider 24 to a value corresponding to the second generation CD, the frequency of the reference clock CKs used for the CLV servo in the motor controller 25 becomes the frequency corresponding to the second generation CD. That is, the disk 1 is driven to rotate at a linear speed corresponding to the second generation CD.
Second layer pit information L ₂ extracted by this time the pickup 21 by decode processing by the high sampling data decoder 29, 64fs / 1-bit digital audio signal is decoded. At this time, the switch 32 because it is connected to T ₂ terminal, 64fs / 1-bit digital audio signal is supplied to a 1-bit D / A converter 33, it is an analog audio signal.

Next, consider the case where the disc 1 to be reproduced is a first generation CD.
First, when the disc discriminating unit 22 discriminates from the TOC data of the disc 1 that the disc is the first generation CD, the frequency division ratio in the frequency divider 24 is set to a value corresponding to the first generation CD. Also it connects the switch 32 to the T ₁ terminal. Further by the focus controller 38, to a state F ₁ to set the focus to the first layer L _1. However, since the second layer does not exist in the first-generation CD, it is sufficient to bring the first-generation CD into the focused state by the focus search / servo operation without any particular control.

  By setting the frequency division ratio in the frequency divider 24 to a value corresponding to the first generation CD, the frequency of the reference clock CKs used for the CLV servo in the motor controller 25 becomes the frequency corresponding to the first generation CD. That is, the disk 1 is driven to rotate at a linear speed corresponding to the first generation CD.

At this time, the pit information extracted by the pickup 21 is decoded by the normal data decoder 28, so that the digital audio signal of fs / 16 bits is decoded. The digital audio signal of fs / 16 bit is converted into a digital audio signal of 64 fs / 1 bit by the oversampling filter 30 and the ΔΣ modulation circuit 31 operated by the clock CK2. Then the switch 32 is connected to the T ₁ terminal, the 64fs / 1-bit digital audio signal is supplied to a 1-bit D / A converter 33, it is an analog audio signal.

Further in such a reproducing apparatus, even if the disc 1 loaded is determined to second generation CD having a two-layer structure, dare extracts pit data of the first layer L _1, also be adapted to the reproduction output it can.
In this case, set the division ratio of the frequency divider 24 to a value corresponding to the first generation CD, it can also connects the switch 32 to the T ₁ terminal. Is a state F ₁ further set the focus to the first layer L _1.

At this time, the pit information of the first layer read by the pickup 21 is decoded by the normal data decoder 28 to be a digital audio signal of fs / 16 bits, and is further converted by the oversampling filter 30 and the ΔΣ modulation circuit 31. The digital audio signal is 64 fs / 1 bit. And is supplied to the 1-bit D / A converter 33 via the T ₁ terminal of switch 32, to be output is an analog audio signal.

According to the reproducing apparatus of FIG. 6, such operation is possible as described above, by reproducing the second layer L ₂ of the data disks as a second generation CD, the playback of very high quality audio data by 64fs Can do it. The sampling frequency of the high sampling data recorded on the second layer L ₂ is, by being an integral multiple of the sampling frequency of the normal data recorded in the first layer L ₁ and the first generation CD, 6 As described above, it is possible to realize a reproducing apparatus having compatibility without having to make the clock system and the reproducing system so complicated.

  That is, first, regarding the clock system, the clock output from the oscillator 23 can be shared because the sampling frequency ratio between the high sampling data and the normal data is an integer ratio. That is, a clock having a required frequency can be easily generated by the frequency divider without providing a plurality of oscillators. Thus, there is no need to construct two independent master clock systems, and the circuit configuration of the clock system can be simplified.

In the reproduction system, the 1-bit D / A converter 33 can be used in common, so that the reproduction system circuit can have a simple configuration, and the sound quality does not deteriorate at that time. ing.
The 1-bit D / A converter 33 is a D / A converter that performs an operation corresponding to reproduced data as high sampling data. In order to use the D / A converter also as reproduced data as normal data, a normal data decoder is used. The fs / 16 bit data from 28 must be converted to 64 fs / 1 bit data. However, since the sampling frequency is an integer multiple, this can be dealt with only by oversampling 64 times by the oversampling filter 30 and converting it to 1 bit by the ΔΣ modulation circuit 31, and a sampling rate converter is not required. Since there is no cause of jitter, sound quality is not deteriorated even for reproduction data as normal data.

In the embodiment, the present CD system is a first-generation CD, and a second-generation CD that is compatible with the first-generation CD has been described. However, the present invention is not necessarily limited to a CD system and can be adopted.
For example, in a digital tape recorder system, a recording / reproducing system employing a sampling frequency that is an integral multiple of 44.1 KHz can be realized.

Further, the present invention is applied to a recording / reproducing system having a sampling frequency of 32 KHz or 48 KHz to construct a second generation system in which the sampling frequency is set to 32 KHz · n or 48 KHz · n (where n is an integer). You can also. That is, taking a disk as an example, it is conceivable to record 48 KHz sampling data on the first layer and 96 KHz sampling data on the second layer.
Further, the structure of the recording layer in the recording medium may be three or more.

FIG. 1 is an explanatory diagram of a recording medium according to an embodiment of the present invention. FIG. 2 is a block diagram of a main part of a recording apparatus for the recording medium according to the embodiment of the present invention. FIG. 3 is an explanatory diagram of a frequency spectrum at each stage of a recording signal according to the embodiment. FIG. 11 is an explanatory diagram of a case where the second generation disc of the embodiment is reproduced by the second generation reproduction device. FIG. 3 is an explanatory diagram of a case where a second-generation disc according to the embodiment is reproduced by a first-generation reproducing device. FIG. 3 is an explanatory diagram of a case where the second generation disc of the embodiment is reproduced by a compatible reproduction device.

Explanation of reference numerals

1 disk 11 ΔΣ modulation 1-bit A / D converter 12, 13, 35 decimation filter 15, 17 recording signal processing unit 14 bit mapping 21, 39 pickup 22 disk discrimination unit 23, 35 oscillator 24, 27, 36 frequency divider 25 Motor controller 26 Spindle motor 28 Normal data decoder 29 High sampling data decoder 30 Oversampling filter 31 ΔΣ modulation circuit 32 Switch 33 1-bit D / A converter 37 D / A converter 38 Focus controller L ₁ First layer L ₂ Second layer

Claims (3)

In an optical disc in which a recording layer has a multilayer structure having at least a first layer and a second layer,
On the first layer, a first digital audio signal having 16 bits of quantization bits sampled at a sampling frequency of 44.1 KHz is recorded,
An optical disc characterized in that a second digital audio signal having the same program as that of the first digital audio signal whose 1-bit quantization bit sampled at 2.8224 MHz is recorded in the second layer. The input analog audio signal is converted into a 1-bit digital audio signal by quantizing bits sampled at n × fs (Hz) (fs is a sampling frequency, n is a positive integer) by a Δ で modulation 1-bit A / D converter. Converting,
A step of adding an error correction code and modulating the digital audio signal in which the quantized bits sampled at n × fs (Hz) are 1 bit;
A step of recording a digital audio signal having 1 bit of quantized bits sampled at nx fs (Hz) to which the above-mentioned error correction code has been added and modulated on a first layer of an optical disc having a plurality of layers. When,
The quantization bits sampled at the above nx fs (Hz) downsample a 1-bit digital audio signal and convert the quantization bits from 1 bit to a first multi-bit to generate a second digital audio signal. Steps to
Reducing the generated second digital audio signal to fewer quantized bits than the first multi-bit;
Recording the second digital audio signal having the reduced number of quantization bits on a second layer different from the first layer of the optical disc having the plurality of layers. ΔΣ modulation means for converting the input analog audio signal into a 1-bit digital audio signal in which quantization bits sampled at n × fs (Hz) (fs is a sampling frequency, n is a positive integer);
Signal processing means for adding and correcting an error correction code to a digital audio signal whose quantization bit sampled at the n × fs (Hz) is 1 bit;
A first digital audio signal having a 1-bit quantized bit sampled at nx fs (Hz) to which an error correction code has been added and modulated by the signal processing means is an optical disc having a plurality of layers. First recording means for recording on the first layer;
Decimation for down-sampling a 1-bit digital audio signal with quantized bits sampled at n × fs (Hz) output from the ΔΣ modulator and for converting the quantized bits from 1 bit to first multi-bits Filter means;
Bit mapping means for down-sampled quantized bits output from the decimation filter means for reducing a first multi-bit digital audio signal to less than the first multi-bit quantized bits;
And a second recording means for recording the digital audio signal whose quantization bits have been reduced by the bit mapping means on a second layer different from the first layer of the optical disc having the plurality of layers. Recording device.

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