JPH10308064A - Recording and reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To always reproduce music high in sound quality regardlessly of a sound recording source. SOLUTION: When a recording source is analog (digital) in recording, a system controller 54A inputs audio data AD (audio data DD having effective bit length of 16-bit outputted from a DIR 52) having effective bit length of 20-bit outputted from an A/D converter 51 to an encoder 56, outputs information indicating effective word length = 20-bit (16-bit) to the encoder 56, and records it in an optical disk 58 with audio data. At the time of reproducing, restored audio data D0 outputted from a decoder 59 is inputted to a data correcting section 80, when effective word length information restored by the decoder 59 is 20 bits, the data is outputted to a D/A converter 60 as it is, when it is 16 bits, the audio data D8 corrected by passing through a quantization distortion reducing circuit 83 in which effective word length is expanded to a lower order side by 4 bits is outputted to the D/A converter 60.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording / reproducing apparatus, and particularly to a CD-WO (Write Once) and an MD-MO (Mag).
CD that records / reproduces audio source digitally on writable recording media such as net Optical)
The present invention relates to a recording / reproducing device such as a WO recorder and an MD recorder.

[0002]

2. Description of the Related Art An optical disk called a CD-WO is a recording medium on which digital data can be recorded only once.
After recording, it can be reproduced repeatedly. FIG. 19 shows a CD-WO
FIG. 2 is a block diagram of a CD-WO recorder for performing digital recording by using. A _IN is an analog input terminal, D _IN
Is a digital input terminal, the former receives an analog audio signal output from an analog source device such as a cassette tape recorder or an FM tuner, and the latter receives a digital audio signal transmitted from a digital source device such as a CD player or DAT. An interface signal is input. The input signal to A _IN is converted into an effective word length n = 2 by an A / D converter 51 having a quantization bit number (word length) of 20 bits.
The data is converted into audio data AD having 0 bits and a sampling frequency F _S = 44.1 kHz. The input signal to D _IN is a digital audio interface receiver (DI
R) 52, the audio data DD in the digital audio interface signal is demodulated and output. The audio data DD is formally output with a word length of 20 bits. The effective word length is n = 20 bits or n ′ = 16 bits. By adding "0000", the word length is formally set to 20 bits.

The audio data AD and DD are supplied to a selector 5
3 is input. The system controller 54 is an operation unit 5
The switching of the selector 53 is controlled in accordance with the user's operation of selecting the analog audio source and the digital audio source in step 5. Therefore, R
When an EC operation is performed, one of the audio data AD and DD desired by the user is selected and input to the encoder 56. When the REC operation is performed, the system controller 54 sets each unit to the recording operation mode, and in response to this, the encoder 56 interleaves the audio data input from the selector 53, adds an error detection / correction code, scrambles the audio data, and outputs the audio data. Control information (subcode information; system controller 5)
4), EFM modulation and the like are performed, and an EFM signal is formed and output to the EFM signal recording / reading unit 57.

[0004] Although not shown, an EFM signal recording / reading unit 57 irradiates a laser beam onto the optical disk 58, a spindle motor for rotating the optical disk (CD-WO) 58 at a constant linear velocity, and a pit train in a pre-groove according to the EFM signal. Optical pickup, which detects the reflected beam of the irradiation beam, an RF amplifier which creates an EFM signal, a focus error signal, and a tracking error signal from the detection output of the optical pickup, and a pre-groove included in the tracking error signal. A meandering component (22.05 kHz carrier signal component; ATIP data that is bi-phase modulated by the FM modulation with a carrier frequency of 22.05 kHz is recorded on the optical disk 58 by making the pregroove meander) is further extracted. ATIP that demodulates (including synchronization detection) A data demodulation circuit, an optical pickup servo circuit that performs focus servo, tracking servo, and feed servo using a focus error signal and a tracking error signal. Based on a 22.05 kHz carrier signal during recording, input from a decoder described later during reproduction. C
It includes a spindle servo circuit for performing constant linear velocity control on the spindle motor based on the LV control signal.

During a recording operation, an EFM signal recording / reading section 57 changes the intensity of the laser beam emitted from the optical pickup in accordance with the EFM signal input from the encoder 56 to form a pit array on the optical disk 58 and, at the same time, reflect light. The optical pickup servo is applied by the focus error signal and tracking error signal created by the RF amplifier using the beam detection output. The ATIP demodulation circuit extracts the 22.05 kHz carrier signal component, detects the synchronization with the ATIP data, and demodulates the data. Then, CLV control is performed based on the carrier signal component. System controller 5
4 generates an A-time (absolute time) and a P-time (performance time) updated one frame at a time from a predetermined initial value each time the ATIP synchronization detection signal is input, and generates an encoder as one of the control information. Output to 56. As a result,
The audio data of the source desired by the user is digitally recorded in the program area of the optical disk 58 while being time-division multiplexed with the control information.

After performing a STOP operation on the operation unit 55, the PL
When the AY operation is performed, the system controller 54 controls the encoder 56 and the EFM signal recording / reading unit 57 to stop, and then sets the EFM signal recording / reading unit 57 and a decoder 59 described later in a reproduction operation mode. At the time of the reproducing operation, the EFM signal recording / reading section 57 uses the focus error signal and the tracking error signal generated by the RF amplifier using the detection output of the reflected beam when irradiating the pit train of the optical disk 58 with the laser beam from the optical pickup. The optical pickup servo is applied, and an EFM signal is created by an RF amplifier using the detection output of the reflected beam, and the CL is controlled based on the CLV control signal input from the decoder.
Perform V control.

At the time of a reproducing operation, the decoder 59 detects synchronization, generates a CLV control signal, performs EFM demodulation,
It demodulates various control information, descrambles, deinterleaves, and performs error detection / correction on EFM demodulated data to restore original 20-bit audio data. The restored audio data is converted to a D / A converter 60 having a length of 20 bits.
/ A conversion and output as an analog audio signal. Various control information demodulated by the decoder 59 is input to the system controller 54, and A-time, P-time
It is used for displaying e.

By the way, as for the audio data AD and DD, the longer the effective word length of one sample is, the smaller the quantization distortion and the higher the sound quality can be recorded and reproduced. Here, the quantization distortion will be briefly described. As shown in FIG. 20, an analog audio signal X in which a 10 kHz sine wave is superimposed on the latter half of a 2 kHz attenuated wave is taken as an example, and
When sampling is performed at 4.1 kHz, quantized with an effective word length n = 16 bits, and converted into audio data D ₀ , a section in which data of the same value continues in the latter half of the 2 kHz attenuation wave occurs as shown in FIG. 21 ( in Figure 21, the sample data of the audio data D ₀ is are represented by the impulse train with a length of the digital value).

The D / A conversion of the audio data D ₀ generally involves outputting a rectangular wave having a height and a sampling period width proportional to the value of the sample data, that is, holding the waveform in the impulse train shown in FIG. This is equivalent to having characteristics, and the D / A conversion output is as shown in FIG. When the signal passes through an analog low-pass filter having a cutoff frequency of 20 kHz for removing aliasing distortion, the waveform becomes as shown in FIG. In the first portion of FIG. 23 where the signal amplitude is large, the rectangular shape of the rectangular wave is almost broken and the quantization distortion is relatively small, but the portion where the signal amplitude from the middle to the latter half is very small (the signal In a section where the dynamic range is close to 1 LSB of digital data), a staircase wave remains, and the quantization distortion becomes significant and the sound quality deteriorates. If the cutoff frequency of the analog low-pass filter for removing aliasing distortion is changed to about 3 kHz in order to reduce the quantization distortion, the waveform becomes a waveform as shown in FIG. Is attenuated.

[0010]

When an analog audio source is selected and recorded, the effective word length is converted to n = 20 bits by the A / D converter 51. The quantization distortion that is conspicuous is small. Also, when the digital audio source is selected and recorded, if the effective word length of the audio data is n = 20 bits, the quantization distortion that is conspicuous when a small signal is recorded and reproduced is small.

However, since most of the existing digital audio sources have a word length of 16 bits according to the standard (JIS standard), most of the audio data transmitted by the digital audio interface signal has an effective word length of n '. = 16 bit length, and in most cases, the CD-WO recorder cannot receive audio data having an effective word length of n = 20 bit length. For this reason, the quantization distortion was conspicuous when a small signal was recorded / reproduced. An object of the present invention is to provide a recording / reproducing apparatus which can always reproduce high-quality music regardless of a recording source in view of the above-mentioned problems of the related art.

[0012]

According to a first aspect of the present invention, there is provided a recording / reproducing apparatus for A / D converting an externally input analog audio signal into audio data having an effective word length = n.
/ D conversion means and externally effective word length = n '(n'<n)
Receiving means for receiving a transmission signal including the audio data of the above, and outputting the received audio data; source setting means for setting the type of recording source;
A recording for forming a recording signal of a predetermined format including audio data of a source of the kind set by the source setting means and various control information related to the audio data among outputs of the / D conversion means and outputs of the receiving means. Signal processing means, recording / reading means for recording a recording signal on a predetermined recording medium during recording, and reading / recording a recording signal recorded on the recording medium during reproduction, and a recording signal read from the recording medium during reproduction. And a reproduction signal processing means for restoring and outputting audio data and various control information from the recording / reproducing apparatus, wherein at recording, the effective word length of the audio data of the source of the type set by the source setting means is set. The effective word length information to be generated is output to the recording signal processing means as one of the control information, and the effective word length information is restored by the reproduction signal processing means during reproduction. To over audio data, based on the effective word length information in the control information associated with the audio data, outputs the restored audio data as it is when a valid word length information indicates the n bits, the effective word length information n'
When the bit is indicated, the effective word length is shifted to the lower side (n-
data correction means for outputting the corrected audio data through the restored audio data to the effective word length expansion means for expanding by n ′).

Thus, even when a digital audio source having an effective word length of n 'is recorded, the effective word length is extended (n-n') bits in the lower direction during reproduction, and quantization distortion is reduced. As in the case of recording / reproducing an analog audio source, high-quality music performance with small quantization distortion can be performed.

According to a twelfth aspect of the present invention, there is provided a recording / reproducing apparatus which receives a transmission signal containing audio data having an effective word length = n or n '(n'<n) from the outside and outputs the received audio data. Means for recording, a recording signal processing means for forming a recording signal of a predetermined format including audio data output from the receiving means and various control information related to the audio data, and a recording signal for recording at a predetermined time. A recording / reading means for recording on a recording medium and reading a recording signal recorded on the recording medium at the time of reproduction, and a reproduction for restoring and outputting audio data and various control information from the recording signal read from the recording medium at the time of reproduction A recording / reproducing apparatus comprising: a control unit for generating effective word length information representing an effective word length of audio data received by a receiving means during recording, Effective word length information generating means for outputting to the signal processing means for recording as one of the information, and audio data restored by the signal processing means for reproduction during reproduction.
When the effective word length information indicates n bits based on the effective word length information in the control information related to the audio data, the restored audio data is output as it is, and the effective word length information indicates n ′ bits. In some cases, the data processing apparatus further includes a data correction unit that outputs audio data that has been subjected to data correction through restored audio data to a quantization distortion reduction unit that extends the effective word length to the lower side by (n−n ′). .

Thus, even if a digital audio source having an effective word length of n 'is recorded, the effective word length is extended (n-n') bits in the lower direction during reproduction, and quantization distortion is reduced. As in the case of recording / reproducing a digital audio source having an effective word length of n, high-quality music performance with small quantization distortion can be performed.

According to a second aspect of the present invention, in the recording / reproducing apparatus according to the first aspect, the recording signal processing means includes an A / A
A predetermined format including compressed audio data obtained by compressing audio data of a source of the type set by the source setting means and various control information related to the compressed audio data among outputs of the D conversion means and reception means. The recording signal is formed, and the reproduction signal processing means restores the compressed audio data from the recording signal read from the recording medium, and further decompresses the audio data to restore the audio data. Similarly, in the recording / reproducing apparatus according to the thirteenth aspect, in the apparatus according to the twelfth aspect, the recording signal processing means includes a compressed audio data obtained by compressing the audio data output from the receiving means and a signal associated with the compressed audio data. And a recording signal of a predetermined format including the various control information thus obtained, and the reproduction signal processing means restores the compressed audio data from the recording signal read from the recording medium and then further expands the audio data to restore the audio data. It is characterized by having done. As a result, even if a digital audio source having an effective word length of n 'is input and data is compressed and recorded, upon reproduction, the compressed data is restored and decompressed, and then the effective word length becomes lower (n-n'). Since the bit is extended and the quantization distortion is reduced, high-quality music performance with small quantization distortion can be performed.

According to a third aspect of the present invention, in the recording / reproducing apparatus according to the first or second aspect, or the twelfth or thirteenth aspect, the quantization distortion reducing means formsally converts the restored audio data into a word length. Is input in a form expanded to n bits or more, extracts a low-frequency component below a predetermined cutoff frequency, and outputs a digital filter having an effective word length of n bits. A counting means for counting the number of points having the same value before and after, and a section of the restored audio data in which the counted value is equal to or less than a fixed value, the word length is formally n bits based on the counting result of the counting means. Selecting means for outputting restored audio data in an extended form, and selecting and outputting audio data output from the digital filter in a section where the count value is equal to or more than a predetermined value. It is characterized in that.

With this arrangement, the quantization distortion reducing means can have the same value of the input digital audio signal input from the reproduction signal processing means continuing for a certain length or more, and having a relatively large quantization distortion as compared with the signal amplitude. In the section, a digital filter is used to formally extend the bit length of the input digital audio signal in the lower direction and replace it with a digital signal obtained by extracting low-frequency components below a predetermined cutoff frequency. The chemical strain can be reduced. In addition, the same value is not continuous for more than a certain amount, and the section of the quantization distortion that is relatively small compared to the signal amplitude remains the waveform of the input digital audio signal whose bit length is formally expanded in the lower direction. The high frequency component does not attenuate carelessly.

According to a fourth aspect of the present invention, there is provided a recording / reproducing apparatus comprising:
The apparatus according to claim 3 or 14, wherein a plurality of digital filters are provided in the quantization distortion reducing means,
Each digital filter has a different cutoff frequency, and the selection means selects an input digital audio signal whose bit length is formally extended in the lower direction by m bits in a section where the count value counted by the counting means is less than a certain value. In a section where the count value is output and the count value is equal to or more than a certain value, audio data output from a digital filter having a lower cutoff frequency is selectively selected as the count value increases. As a result, while avoiding attenuation of the signal component, it is possible to surely reduce both the quantization distortion that is relatively large and the quantization distortion that is relatively small as compared with the signal amplitude.

According to a fifth aspect of the present invention, in the recording / reproducing apparatus of the third aspect, the discontinuous point generated in the output of the selecting means is provided to the quantization distortion reducing means. It is characterized by comprising extraction means for extracting and correction means for making discontinuous points in the output of the selection means continuous. Thereby, it is possible to suppress the occurrence of new waveform distortion.

According to a sixth aspect of the present invention, in the recording / reproducing apparatus according to the first or second or third aspect, the source setting means detects an input source among the analog audio source and the digital audio source. It is characterized in that the recording source is automatically set based on the detection result of the detection means. By this, at the time of recording, if the audio output is performed from a desired source device out of the analog audio source device and the digital audio source device, the type of the recording source is automatically set, so that it is not necessary to manually select the source. .

According to a seventh aspect of the present invention, in the recording / reproducing apparatus according to the first or second or third aspect, the source setting means includes instruction operating means for instructing detection of a source having an input, and a source having an input. Input source detecting means for detecting, and the recording source is automatically set based on the detection result of the input source detecting means at the time when the instruction is given by the instruction operating means. Thus, before performing recording, a preliminary audio output is performed from a source device that desires recording, and the type of recording source can be set by instructing detection of a source having an input by the instruction operation means. There is no need to determine whether the device outputs analog or digital.

In the recording / reproducing apparatus according to the eighth aspect, in the apparatus according to the first or second or third aspect, the receiving means externally includes audio data of effective word length = n or n '(n'<n). Receiving the transmission signal,
It is characterized by. Accordingly, the present invention can be applied to a case where the audio source device outputs a transmission signal including any audio data of effective word length = n or n ′ (n ′ <n).

According to a ninth aspect of the present invention, in the device of the eighth aspect, when the analog audio source is set by the source setting means, the effective bit length information generating means includes an effective bit length indicating n. Information, and when the digital audio source is set by the source setting means, whether effective word length information is to be generated based on the selection result by the effective word length selection operation means for selecting one of n and n ' Or, to generate effective word length information based on the detection result of the effective word length detecting means for detecting the effective word length of the audio data of the digital audio source,
It is characterized by. Thereby, when the digital audio source is set by the source setting means, the effective word length information desired by the user can be generated according to the manual operation, or the effective word length information can be automatically generated.

According to a tenth aspect of the present invention, in the device of the eighth aspect, the source setting means includes an instruction operating means for instructing detection of an input source, and an input source detecting means for detecting a source having an input. Including automatically setting the recording source based on the detection result of the input detection means at the time when the input source detection is instructed,
It is characterized by. Thus, before performing recording, a preliminary audio output is performed from a source device that desires recording, and the type of recording source can be set by instructing detection of a source having an input by the instruction operation means. There is no need to determine whether the device outputs analog or digital.

In the recording / reproducing apparatus according to the eleventh aspect, in the apparatus according to the eighth or the tenth aspect, the effective word length information generating means includes an instruction operating means for instructing reading of the effective word length, and an instruction operating means for receiving from the digital audio source. Effective word length detection means for detecting the effective word length of the selected audio data, wherein when the digital audio source is set by the source setting means, the effective word length is read when the instruction operation means instructs to read the effective word length. It is characterized in that effective word length information is generated based on the detection result of the word length detecting means. Thus, when a digital audio source is to be recorded, a preliminary audio output is performed from the source device desired to be recorded before recording, and if the instruction operation means instructs to read the effective word length, the recording is actually performed. At the time of performing, correct valid word length information can be generated.

According to a seventeenth aspect of the present invention, in the device of the twelfth, thirteenth or thirteenth aspect, the effective word length information generating means performs an effective word length selection operation of selecting one of n and n '. The effective word length information is generated based on the selection result by the means, or the effective word length information is generated based on the detection result by the effective word length detection means for detecting the effective word length of the audio data received by the receiving means. That is, it is characterized. Thereby, the effective word length information desired by the user can be generated according to the manual operation, or the effective word length information can be automatically generated.

[0028] In the recording / reproducing apparatus according to the eighteenth aspect, in the apparatus according to the twelfth, thirteenth or thirteenth aspect, the effective word length information generating means includes an instruction operating means for instructing reading of the effective word length and a receiving means. Effective word length detection means for detecting the effective word length of the received audio data, and effective word length information based on the detection result of the effective word length detection means at the time when the instruction operation means instructs to read the effective word length. Is generated. This allows
When recording a digital audio source, before performing the recording, perform preliminary audio output from the source device desired to be recorded, and instruct the reading of the effective word length by the instruction operation means, when actually recording, Correct valid word length information can be generated.

[0029]

Next, an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram of a CD-WO recorder according to the present invention. The same components as those in FIG. 19 are denoted by the same reference numerals. Reference numeral 61 denotes an input source detection circuit which receives audio data AD and DD and detects a source having an input by detecting whether or not data has changed. Then, the detection result is output to the system controller 54A. Reference numeral 62 denotes an effective word length detection circuit which receives the audio data DD and detects whether or not the lower 4 bits have changed, so that the effective word length of the audio data DD is n = 20.
Bit or n '= 16 bits. Then, the detection result is output to the system controller 54A.

Reference numeral 55A denotes an operation unit, and a PLAY key 6
3. In addition to the REC key 64 and the STOP key 65, an analog key 66 and a digital key 67 for manually selecting a recording source type from an analog audio source and a digital audio source, and a digital source for manual operation And the effective word length is n '= 16
Digital low key 68 (selection of n '= 16) and digital high key 69 for selecting bits or n = 20 bits
(Selection of n = 20), an auto key 70 for automatically detecting an input source, setting a recording source, and detecting an effective word length when the REC key 64 is operated. A memory key 71 is provided to allow preliminary audio output from a desired source device, and to detect an input source, set a recording source, and detect an effective word length when a user presses a key. ing.

The system controller 54A includes an operation unit 5
In response to the operation of 5A, the switching of the selector 53 is controlled, each part is set to a recording operation mode to record audio data on the optical disk 58, and each part is set to a reproduction operation mode to reproduce audio data from the optical disk 58. . When the recording operation mode is set, the system controller 54A outputs effective word length information indicating the effective word length of audio data input from the selector 53 to the encoder 54 (here, “1” when the effective word length is n = 20, Flag data AF which becomes "0" when the effective word length is n '= 16
), And outputs control information together with A-time, P-time and the like to the encoder 54, and records the control information in the program area of the optical disk 58 in parallel with the recording of the audio data.

The operation of the system controller 54A will be described in more detail.
With respect to the keys 66 to 71, any one of the pressings is received with a higher priority. Manual source selection If you want to record an analog input, connect the output side of the analog audio source device to the analog input terminal A _IN, and if the user presses the analog key 66, the system controller 54A will be in the analog input mode, and the recording source will be the analog source. And the selector 53 is set to the A / D converter 5
Switch to 1 side. When the REC key 64 is pressed, the encoder 56 and the EFM signal recording / reading unit 57 are set to the recording operation mode, and AF = 1 indicating that the effective word length is n = 20 is continued until the STOP key is pressed. Then, it is generated and output to the encoder 56 as control information together with A-time, P-time, and the like. The encoder 56 forms a recording signal in which audio data AD having an effective word length of n = 20 bits input from the A / D converter 51 and control information are combined, and records the recording signal in the program area of the optical disk 58.

[0033] To record a digital input, the output side of the digital audio source device connected to the digital input terminal D _IN, if the user presses a digital key 66, the system controller 54A comprises a digital input mode, a recording source to a digital After setting, the selector 53 is switched to the DIR 52 side. When the REC key 64 is pressed, the encoder 56 and the EFM signal recording / reading unit 57 are set to the recording operation mode, and if the effective word length detection circuit 62 detects that the effective word length is n = 20. AF = 1 is generated and the effective word length is n ′ = 16
Is detected, AF = 0 is continuously generated, and is output to the encoder 56 as control information along with A-time, P-time, and the like. Encoder 56 is D
A recording signal is formed by combining control data and audio data DD having an effective word length of n = 20 bits or n ′ = 16 bits input from the IR 52 and is recorded in the program area of the optical disk 58.

Thus, the system controller 5
4A sets the recording source and generates the corresponding effective word length information according to the user's source selection operation. In addition,
I want to record digital input, but if the effective word length is n =
If it is known that the bit is 20 bits, simply pressing the digital high key 69 causes the system controller 54A to enter the digital high bit input mode and set the selector 53 to DI.
Switch to R52 side. When the REC key is pressed, each unit is set to the recording operation mode, and control information including AF = 1 is generated and output. Conversely, if the effective word length is n 'in advance
= 16 bits, simply pressing the digital low key 68 causes the system controller 54A to enter the digital low bit input mode,
Switch to IR52 side. When the REC key is pressed, each unit is set to the recording operation mode, and control information including AF = 0 is generated and output. As described above, since the effective word length can be specified by the manual operation, the effective word length detection circuit 62 can be omitted.

Automatic source setting during recording In particular, when the user wants to automatically determine the audio input from the analog audio source device or the digital audio source device and perform recording without the user performing a source selection operation, the auto key 70 is set. Press. Then, the system controller 54A enters the auto mode, and if the result of the detection by the input source detecting circuit 61 at the time when the REC key 64 is pressed indicates that the analog source is input, the recording source is set to analog. Then, the selector 53 is switched to the A / D converter 51 side, and AF = 1
Is generated and output.

Conversely, if the result of the detection by the input source detection circuit 61 at the time when the REC key 64 is pressed indicates that the digital source is input, the recording source is set to digital, and the selector 53 is set to the DIR 52 Switch to the side. Subsequently, the effective word length detection circuit 62 determines that the effective word length is n = 2.
Generates and outputs control information including AF = 1 if detected as 0, and generates control information including AF = 0 if detected that the effective word length is n '= 16. And output. As described above, since a desired source can be automatically recorded without performing a source selection operation, labor can be saved.

Automatic source setting before recording If it is desired to automatically set a desired source before recording, for example, if the desired source is an analog cassette tape recorder, the desired music to be recorded is reproduced and output in a preliminary manner. Press the memory key 71. Then, the system controller 54A enters the preliminary setting mode, and the detection result of the input source detection circuit 61 at that time indicates that there is an analog source input. Therefore, the recording source is set to analog, and the selector 53 is set to the A / D converter. Switch to the side of 51. The user rewinds the cassette tape to the beginning of the desired song and
When the reproduction output is started for recording after the key is pressed, the system controller 54A sets each unit to the recording operation mode, and generates and outputs control information including AF = 1.

If the desired source is the digital out of the CD player, the desired music is preliminarily reproduced and output, and the memory key 71 is pressed halfway. Then, the system controller 54A enters the preliminary setting mode, checks the detection result of the input source detection circuit 61 at that time, and there is a digital source input. Therefore, the recording source is set to digital, and the selector 53 is set to the DIR 52. Switch to the side. Further, the detection result of the effective word length detection circuit 62 at the time when the memory key 71 is pressed is stored. And REC
After the user presses the key, the user starts reproduction output for recording again from the beginning of the desired song on the CD. When the system controller 54A performs a recording operation mode on each part, the effective word length stored earlier is n = 20 bits. If it is, control information including AF = 1 is generated and output, and if the effective word length is n '= 16, control information including AF = 0 is generated and output.

As described above, the desired source can be automatically recorded without performing the source selection operation, and the recording operation can be started by pressing the REC key before starting the reproduction output on the source side. Therefore, it is possible to prevent the beginning of the song from being interrupted.

When the STOP key is pressed after recording, the system controller 54A stops the recording operation. Thereafter, when the PLAY key is pressed, the system controller 54 is pressed.
A sets each unit to the reproducing operation mode and starts the reproducing operation. At this time, the EFM signal recorded on the optical disk 58 is read by the EFM signal recording / reading unit 57 and output to the decoder 59. The decoder 59 restores the audio data having the same word length of 20 bits and control information output from the original selector 53, and the former restored audio data D ₀ is interposed at a stage preceding the D / A converter 60. The data is output to the data correction unit 80, and the latter is output to the system controller 54A.

If the effective word length of the restored audio data D ₀ is n = 20 bits, the data correction section 80 outputs the data as it is. However, if the effective word length of n ′ = 16 bits, the effective word length is shifted to the lower side by nn ′. = By 4 bits to reduce and correct the quantization distortion. 81 of the data correction units 80
When 82 denotes a selector, 83 is an effective word length of the restored audio data D ₀ of the effective word length n'= 16 bits to the lower side n-
This is a quantization distortion reduction circuit that expands by n '= 4 bits. In the reproduction operation mode, when the AF in the control information input from the decoder 59 is 1, the system controller 54A
The output side of the selector 81 is switched to the selector 82 and the input side of the selector 82 is switched to the selector 81 side. When AF is 0, the selector 8
1 is switched to the quantization distortion reduction circuit 83, and the input side of the selector 82 is switched to the quantization distortion reduction circuit 83.
Switch to the side. The output side of the selector 82 is A / D
It is connected to the converter 60.

The configuration of the quantization distortion reduction circuit 83 will be specifically described with reference to FIG. 1 is the sampling frequency 4
4.1 kHz, input terminal of restored audio data D _{0 having} word length n = 20 bits, 2 is a counter, and a point where the same value continues before and after each point (sample point) of input audio data D ₀ (Excluding itself) and outputs a count value indicating the degree of quantization distortion. When the number of consecutive identical values is large, it can be considered that the quantization distortion is larger than the signal amplitude at that point. Reference numerals 3 to 5 denote digital low-pass filters having cut-off frequencies of 7 kHz, 4 kHz, and 2.5 kHz, respectively, regardless of whether the effective word length is n = 20 bits or n '= 16 bits. A predetermined internal operation is performed on the input audio data D ₀ which is formally expanded to 20 bits (the operation word length is 20 bits or more), and a low-frequency component is passed. Each of the digital low-pass filters 3 to 5 outputs the operation result in a word length of 20 bits. Therefore, the effective word length of the output of each of the digital low-pass filters 3 to 5 is 20 bits.

The counter 2 receives Td (1 in this case, seven times the sampling period) from the input of a certain point of the input audio data D ₀ until the output of the count _value of the certain point.
58 μs), and the group delay time of the digital low-pass filters 3 to 5 also matches Td.

[0044] 6 is a selection means, counter based on the output of the 2 input audio of the data D _0, the input audio data D ₁ is a count value is constant following section is formal word length 20 bits ( D ₁ selects and outputs those) obtained by delaying the D ₀ only Td, the digital signal D ₂ to D count value above a certain section through the digital filter 3-5
_{Among 4} , the audio data output from the digital filters 3 to 5 having a lower cutoff frequency is selected and output as the count value is larger. 7 of the selection means 6 is an encoder that divides the count value output from the counter 2 into a plurality of stages. Here, the count value is r, and r = 0... First stage 1 ≦ r ≦ 2. 2nd stage 3 ≦ r ≦ 5 3rd stage 6 ≦ r 4th stage Divide into 4 stages and output i indicating the stage. Note that r may be divided into four stages in another range.

Reference numeral 8 denotes a counter 2 and a digital low-pass filter 3 which delay the input audio data D ₀ by Td.
A delay unit 10 for adjusting the delay with respect to the delay between the input and the output of the encoder 5;
Selects the output D ₁ of the delayer 8 when, when the 2 selects the output D ₂ of the digital low-pass filter 3, and selects the output D ₃ of the digital low-pass filter 4 for 3, digital low-pass filter 5 when the 4 selects and outputs the output D _4. In the input audio data D ₀ , a section where r = 0 and the quantization distortion is considered to be relatively small compared to the signal amplitude is selected by selecting the output D ₁ of the delay unit 8. remains in the waveform of D _0, the signal is output without being attenuated. Of the input audio data D _0, r is not 0, the section considered quantization distortion is relatively large compared to the signal amplitude, one of the outputs D ₂ to D ₄ of the digital low-pass filter 3-5 By being selected, continuous sections having the same value become smooth curves, and quantization distortion is reduced.

It should be noted that, among the outputs D _{2 to} D ₄ of the three digital low-pass filters 3 to 5, the one with a lower cutoff frequency is selected as the count value counted by the counter 2 is larger. This is to ensure that both large and small quantization distortions relative to the signal amplitude are reduced, and that the signal components are not attenuated as the quantization distortion is reduced. If, when the cutoff frequency is only one of the digital low-pass filter 3 of 7 kHz, r = 0 of the section select D _1, section 1 ≦ r is for selecting the output D ₂ of the digital low-pass filter 3, the input In the audio data D _0, a section in which points having the same value lasts only for a short time (the relative quantization distortion is small relative to the signal amplitude) can be easily smoothed, but a section in which points having the same value continue for a long time (signal (The relative quantization distortion is large compared to the amplitude) is biased toward the low band when viewed in the frequency component, and it is difficult to make it smooth.

Conversely, if only one of the digital low-pass filters 5 having a cutoff frequency of 2.5 kHz is set, and r ≦ 5
The interval select D _1, case of 6 ≦ r section selects the output D ₄ of the digital low-pass filter 5, of the input audio data D _0, interval point continues for a long time the same value can be easily smoothly However, continuous sections in the range of r ≦ 5 cannot be made smooth. Wakashi, r = 0 of the section to select the D _1,
The section of 1 ≦ r is the output D of the digital low-pass filter 5.
If you choose _4, of the input audio data D _0, section points with the same value continues relatively short when viewed in the frequency components, are biased to a higher frequency side than the cut-off frequency, attenuates the signal Would.

Although the audio data D ₅ whose quantization distortion is reduced without attenuating the signal is output from the selection means 6, there is a possibility that a discontinuity may occur at the switching timing of the selector 10. Therefore, in the example of FIG.
The discontinuous points are made continuous in the subsequent stage. 11
An extraction means, the sign of the difference is extracted as a discontinuous point above a certain there point difference between the corresponding points of the value as the input audio data D ₀ for each point of the output D ₅ of the selecting means 6, then the Is determined. Among extracting means 11, 12 is a subtracter for obtaining a difference by subtracting the audio data D ₁ from the output D ₅ of the selecting means 6, 13 is a comparator circuit, the output δ of the subtracter 12 the positive side reference value + R, and Compared with the negative reference value -R, a comparison result j that satisfies j = 3 when -R <δ <+ R, j = 2 when δ ≦ −R, and j = 3 is output. j = 2 indicates that the difference D ₅ and D ₁ is positive, j = 3 indicates that the difference is negative. When j = 2 or j = 3, the output of the selection means 6 is a discontinuous point generated by switching of the selector 10. Note that R is an arbitrary positive value, but here, for example, R = 8 (corresponding to (1/2) LSB in the case of audio data having a word length of 16 bits).

Numeral 14 denotes a correction means, which outputs the discontinuous point extracted by the extraction means 11 from the output of the selection means 6 to a point corresponding to the input audio data D ₁ by the sign of the difference between D ₅ and D _1. Is replaced with a value obtained by adding or subtracting a predetermined value in accordance with the formula (2), and the data is made continuous. 15 of the correction means 14 is the input audio data D
Adder for adding _R'1, 16 is a subtracter for subtracting an R'from the input audio data D _1. 17 is a selector, based on the comparison result of the comparison circuit 13, between the j = 1 selects the output D ₅ of the selecting means 6 to select the output D ₆ of the adder 15 becomes j = 2, j = When it reaches 3, subtractor 1
Selects the output D ₇ 6 outputs. R 'is an arbitrary positive value, but is the same as R here. By replacing the discontinuous points extracted by the extracting means 11 with the output of the adder 15 or the output of the subtractor 16 from the output of the selecting means 6,
The difference from the input audio data D ₀ at the discontinuous point is limited to a certain value or less. As a result, it is possible to correct the discontinuous point so as to be continuous. The audio data D ₈ after the quantization distortion reduction output from the correction unit 14 is output from the output terminal 18 to the selector 82.

Next, the operation of the data correction unit 80 will be described with reference to FIGS. When the effective word length of the restored audio data is n = 20, the analog audio source is re-recorded or the effective word length is n.
When a digital audio source of = 20 bits is recorded / reproduced, the decoder 59 outputs restored audio data D ₀ having a formal word length of 20 bits and an effective word length of n = 20 bits. At this time, the system controller 5
4A is AF = 1 in the control information input from the decoder 59.
Therefore, the output side of the selector 81 of the data correction unit 80 is switched to the side of the selector 82, and the input side of the selector 82 is switched to the output side of the selector 81. Therefore, the restored audio data D ₀ is directly output to the D / A converter 60 and D / A converted. Since the restored audio data D ₀ has an effective word length of 20 bits, quantization distortion is extremely small.
You can listen to high quality music.

The effective word length of the restored audio data is n '=
In the case of 16, when a digital audio source having an effective word length of n '= 16 bits is recorded / reproduced, the decoded audio from the decoder 59 has a formal word length of 20 bits but an effective word length of n' = 16 bits. data D ₀ is output. At this time, since AF = 0 in the control information input from the decoder 59, the system controller 54A switches the output side of the selector 81 of the data correction unit 80 and the input side of the selector 82 to the quantization distortion reduction circuit 83 side. The restored audio data D ₀ is input to the quantization distortion reduction circuit 83.

Here, for convenience of explanation, the case where the input of the input terminal 1 is the input audio data D ₀ (a waveform in which a 10 kHz sine wave is overlapped by one cycle in the middle of the latter half of the 2 kHz attenuation waveform) in FIG. think of. A count value indicating the degree of quantization distortion at each point of the input audio data D ₀ (the number of points having the same value before and after the point excluding the own point) r
Is counted by the counter 2 and output with a delay of Td (see FIG. 3). Also, by performing predetermined internal operation with an operation word length of 20 bits or more by digital low-pass filters 3 to 5 having different cutoff frequencies, a low-frequency component of the input audio data D ₀ is extracted, and the effective word length is reduced. n
= 20 audio data D ₂ to D _4-bit length is outputted (see FIGS. 4 to 6). Each of the digital low-pass filters 3 to 5 also has a group delay time Td between input and output.

In the selection means 6, the input audio data D ₀ is delayed by Td by the delay unit 8,
Time adjustment with the outputs of the digital low-pass filters 3 to 5 is performed (see FIG. 7). Encoder 7 of the selecting means 6 divides the count value r in four steps, and outputs an i of an operation, the selector 10 based on the i outputs choose one alternative from among D ₁ to D ₄ (See FIG. 3).

[0054] From the first rising slope of the input audio data D ₀ in FIG. 3 up to the second rising gradient is 2k
The amplitude of the Hz waveform is large and the same value is not continuous at most points. Therefore, a r = 0, the relative quantization distortion that compared to the signal amplitude also occupied almost constant following smaller section A ₀ to A _2. In these sections, i becomes 1, and the selector 10 outputs the input audio data D ₁ delayed from D ₀ by Td. Sections A ₃ and A ₄ (A ₄ is 10 kHz
The same applies to the z waveform portion). In the first after the peak of the input audio data D _0, section B ₀ .about.B ₂ which points having the same value due to the influence of quantization errors are consecutive 2-3 occurs. These sections are sections where the relative quantization distortion relative to the signal amplitude is equal to or greater than a certain value, but are still relatively small, and r = 1
２2, i = 2, and the selector 10 selects the output D ₂ of the digital low-pass filter 3. After that, 2kHz
As the waveform of z attenuates gradually, points of the same value become 2-3.
4 points with the same value magic to the section B ₂ .about.B ₅ to pieces continuously
Six consecutive sections C ₀ and C ₁ appear. These are relatively large interval quantization distortion, becomes r = 3~5, i = 3, the selector 10 selects the output D ₃ of the digital low-pass filter 4. Further, where the waveform of 2 kHz is greatly attenuated, sections E ₀ and E _{1 in} which seven or more points of the same value continue and the quantization distortion is extremely large occur.
When r ≧ 6 and i = 4, the selector 10 selects the output D ₄ of the digital low-pass filter 5. As a result, the output D ₅ of the selecting means 6 becomes as shown in FIG. 8, without causing inadvertent signal attenuation, smooth the same value continuously sections of various lengths were present in FIG. 21 has been established corners The curve is changed, and it can be seen that those having a large and small quantization distortion relative to the signal amplitude are surely reduced.

However, in FIG. 8, some discontinuous points such as α, β, and γ occur near some switching timings of the selector 10. These discontinuous points are corrected by the operation of the extracting means 11 and the correcting means 14. That is, when the difference δ between the value of each point of the output D ₅ of the selection means 6 and the corresponding point of the input audio data D ₀ is equal to or more than a certain value, the extraction means 11 extracts the point as a discontinuous point. Also determine. Then, while the output D ₅ of the selection means 6 is not a discontinuity point, the correction means 14 outputs D ₅ as it is, but when the output point D ₅ becomes a discontinuity point, if the difference δ is positive, the input audio data D ₀ Is replaced by a value obtained by adding a constant value to the corresponding point of, and if the difference δ is negative, the discontinuous point is made continuous by replacing the value by subtracting a constant value from the corresponding point of the input audio data D ₀ .

Specifically, first, the difference δ between the output D ₅ of the selection means 6 and the delayed input audio data D ₁ is calculated by the subtractor 12 (see FIG. 9). Then, the difference δ is compared with + R and −R by the comparison circuit 13 (R = 8), and −R <δ <+
When R, j = 1 is output, when + R ≦ δ, j = 2 is output, and when δ ≦ −R, j = 3 is output (see FIG. 9). In FIG. 8, j = 2 for α, j = 3 for β and γ, and j = 1 for the others. In the correction means 14, the adder 1
5 adds R to D ₁ and outputs D ₆ (see FIG. 10),
Subtracter 16 outputs the D ₇ subtracts R from D ₁ (see FIG. 11). D ₆ indicates the upper limit of the final output can take, D ₇ represents a lower limit for the final output can take. The selector 17 is between the j = 1 selects and outputs the output D ₅ of the selecting means 6, when it becomes j = 2 come discontinuities D ₅ alpha is, the adder 15 in place of the alpha selects and outputs the output D ₆ of. Similarly, when the discontinuous point β (γ) of D ₅ comes, j = 3
, The output D _{7 of the} subtractor 16 is used instead of β (γ).
Select and output. Thus, the selector 17, as shown in FIG. 12, discontinuity in D ₅ alpha, beta, discontinuity is small α'the gamma, .beta. ', Continuous reduction and back and forth a γ'been achieved audio data D ₈ has is output.

The audio data D ₈ is converted to a 20-bit D / A
D / A conversion by the converter 60 is as shown in FIG.
Further, a cut-off frequency of 20 kHz for removing aliasing distortion.
14 through an analog low-pass filter (not shown). When FIG. 14 is compared with FIG. 23 of the prior art, according to the present embodiment, not only the small signal area, but also
It can be seen that the quantization distortion is significantly reduced even in a region where the amplitude is slightly large.

According to this embodiment, when the analog source is re-recorded and when the audio source having an effective word length of 20 bits is re-recorded, the restored audio data having an effective word length of 20 bits is D / A. Since it is output to the converter 60, music reproduction with extremely small quantization distortion utilizing the effective word length can be enjoyed. When an audio source having an effective word length of 16 bits is recorded / reproduced, the restored audio data D ₀ is input to the quantization distortion reduction circuit 83, and the effective bit length is extended by 4 bits to the lower side. Can reduce the noticeable quantization distortion when recording / reproducing.

The quantization distortion reduction circuit 83 outputs the digital low-pass filter 3 to the section of the input audio data D ₀ where the same value continues for a certain amount or more and the quantization distortion is relatively large compared to the signal amplitude. 5 to extend the effective word length in the lower direction and replace it with audio data from which low-frequency components have been extracted to form a smooth curve. Therefore, quantization distortion can be reduced. without continuous constant over a relatively small section of quantization distortion as compared to the signal amplitude, because the word length is to remain formally n bits input audio data D ₀ of the waveform, the high frequency component There is no inadvertent attenuation.

The quantization distortion reduction circuit 83 includes three digital low-pass filters 3 to 3 having different cutoff frequencies.
5, the selection means 6 selects and outputs the input audio data D ₀ whose bit length is formally expanded in the lower direction in a section in which the number of consecutive identical values is equal to or less than a certain value from the input audio data D _0. On the other hand, in the section of the input audio data D ₀ in which the number of consecutive identical values is equal to or more than a certain value, the audio data output from the digital low-pass filter having a lower cutoff frequency is selected as the number of consecutive data is larger. Is selected and output, so that those having relatively large or small quantization distortion as compared with the signal amplitude can be reliably reduced. Further, the quantization distortion reducing circuit 38
Newly generates waveform distortion by providing extraction means 11 for extracting discontinuous points generated in the output of the selection means 6 and correction means 14 for making the discontinuous points in the output of the selection means 6 continuous. Can also be suppressed.

In the above embodiment, three digital low-pass filters having different cutoff frequencies are provided. However, two or four or more digital low-pass filters may be provided, and 7 kHz, 4 kHz, 2.5 kHz For example, only one digital low-pass filter having a predetermined cutoff frequency is provided, and the input audio data has a section in which the count value r counted by the counter (2) is equal to or less than n (n may be 0; A suitable integer of 1 or more such as 2, 3, 4, 5) may be used as a selector (10) to select the input audio data (D ₁ ) after the delay by the delay unit (8), and the count value r is larger than n. Even if the output of the digital low-pass filter is selected in a large section, the quantization distortion can be reduced. Further, the description has been made assuming that n = 20 and n ′ = 16, but the present invention is not limited to this, and other values such as n = 24 and n ′ = 18 may be used.

The extraction of discontinuous points in the output of the selector (10) and the correction by continuity may be executed by a method other than the above embodiment. For example, as shown in FIG. 15, the adder 15A of the correction means 14A is a selector (10).
Of adding a positive constant value R'the output D _5, the subtractor 16A is to subtract the positive constant value R'from D _5. In the extracting means 11, the subtracter 12 outputs D ₅ and the output D ₁ of the delay unit (8).
Is obtained by comparing the difference δ with ± R by the comparison circuit 13,
-R <has a δ <+ R, if there is no discontinuous point in D ₅ (j = 1), the selector 17A selects and outputs the D _5. Unlike this, if a negative discontinuous point D ₅ becomes [delta] ≦ -R occurs (j = 3), the selector 17A selects and outputs the output of the adder 15A, conversely, + R ≦ [delta] becomes when a positive discontinuous point occurs in D ₅ (j = 2), the selector 17A is to select and output the output of the subtracter 16A. Note that R ′ may be the same value as R or a different value. Examples of Figure 15 is also relatively simple configuration, the can be removed discontinuities size larger than a certain produced output D ₅ of the selector (10) securely.

As another method for avoiding the occurrence of discontinuous points in the output, as shown in FIG.
In each of D _5, 1 sample period by delay time delayed by the two-stage delay unit 19, 20 with the Create a D ₅₁ and D _52, the averaging circuit 21 of the D _5, D _51, D ₅₂ The three values are averaged. On the other hand, the extraction means D ₁ in 11B the delayed by delay unit 22 having a delay time of one sampling period to create a D _11, calculates the difference δ in D ₅₁ and D ₁₁ by the subtractor 12, the comparison circuit 13B -R <δ <+ R
J indicates that there is no discontinuity point
'= 1, and if δ ≦ −R or + R ≦ δ, j ′ = 2 indicating that a discontinuous point has been extracted is output. When the selector 17B of the correction means 14B is the j'= 1 there is no discontinuity in D _51, and selects and outputs D _51, a j'= 2 with discontinuous point occurs in the D ₅₁ If
The output of the averaging circuit 21 is selected and output.

[0064] According to the example of FIG. 16, the selector (10) outputs D value as delayer for each point ₅ (8) at the corresponding point and the difference is constant over a certain point of the input audio data D ₁ of the post-delay since so as to extract as a discontinuous point, it is possible to extract a discontinuous point output D ₅ to the resulting constant over the size of the selector (10) with a simple structure easily, the selector (10 If discontinuous point larger than a certain size to the output D ₅ of) occurred among the D _5, since such substitution with an average value of the plurality of points near the discontinuous point, the discontinuous point with a simple structure Can be easily changed to a smooth curve. In the case of Figure 16, the averaging circuit 21 D ₅ and D ₅₁ or D ₅ and D _52,
Or to perform only the average of the two points, two D ₅₁ and D ₅₂
Averaging may be performed only on points, and the values of discontinuous points may not be used for averaging.

[0065] Still another method to avoid the discontinuous point in the output occurs, as shown in FIG. 17, the averaging circuit 23 in correction means 14C keep averaging the D ₅ and D _1. On the other hand, calculates the difference [delta] of D ₅ and D ₁ by extracting means 11C subtracter 12, as compared to ± R at the comparison circuit @ 13 C, -R <[delta]
If <+ R, j ′ = 1 indicating that there is no discontinuity point is output, and if δ ≦ −R or + R ≦ δ, j ′ = 2 indicating that the discontinuity point has been extracted is output. Output. When the selector 17C of the correcting means 14C is the j'= 1 there is no discontinuous point in D _5, and selects and outputs D _5, a j'= 2 discontinuities occurs in the D ₅ In this case, the output of the averaging circuit 23 is selected and output. According to the example of FIG. 17, the output D of the selector (10)
₅ of the discontinuity, since the serialized by substituting the average value of the values of the corresponding points of the value as the input audio data D ₁ of the discontinuity point, the discontinuous point to facilitate smooth curve with a simple structure Can be changed.

As still another method for avoiding the occurrence of a discontinuity in the output, as shown in FIG. 18, the correcting means 14D is provided with a delay unit 24 for delaying the output of the selector 17D by one sample period. Is a selector (1
0) of the output D ₅ and selects the output of the delay device 24 so as to output. On the other hand, the extraction unit 11D by the subtractor 12 obtains the difference D ₅ and D ₁ [delta], as compared to ± R at the comparison circuit 13D, there is a discontinuity point if it is an -R <δ <+ R J ′ = 1 indicating that no discontinuous point is extracted if δ ≦ −R or + R ≦ δ.
2 is output. The selector 17D of the correcting means 14D For j'= 1 there is no discontinuous point in D _5, and selects and outputs D _5, and discontinuity occurs in D ₅ j
When '= 2, the output of the delay unit 24 is selected, and D ₈
Output. According to the example of FIG. 18, D ₅
Discontinuities in, among D _5, since it is replaced by the value of a point is not a point of discontinuity immediately before the discontinuous point can be changed discontinuities facilitating smooth curve with a simple structure .

In the above embodiment, the CD-WO recorder has been described as an example. However, the present invention can be similarly applied to other recording / reproducing devices such as an MD recorder. MD
In the case of a recorder, at the time of recording, the encoder converts audio data having a word length of n bits input from the selector at the preceding stage into AT data.
The compressed audio data is compressed by the RAC method, subjected to predetermined error detection / correction processing, converted into control information (sub-data) including effective word length information, and converted into an EFM signal by time division and output. The EFM signal recording / reading unit magneto-optically records the EFM signal output from the encoder in a program area of the MD-MO. During playback, the decoder uses EF
E read from MD-MO by M signal recording / reading unit
Based on the FM signal, the control information is demodulated and output to the system controller, and the compressed audio data is demodulated (decompressed).
Bit audio data is restored and output to the data correction unit. In the case of the MD recorder, after recording, the effective word length information is recorded for each track in the UTOC area of the MD-MO, and when a certain track is reproduced, U is read from the UTOC area of the MD-MO in advance.
Based on the effective word length information of the track in the TOC information,
Switching between the two selectors of the data correction unit may be performed.

[0068]

According to the recording / reproducing apparatus of the present invention, when a digital source having a short effective word length is recorded / reproduced, the effective bit length of reproduced audio data is extended in a lower direction to reduce quantization distortion. Therefore, high-quality music reproduction with small quantization distortion can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram of a CD-WO recorder according to one embodiment of the present invention.

FIG. 2 is a circuit diagram of a quantization distortion reduction circuit.

FIG. 3 is an explanatory diagram showing operations of a counter and an encoder.

FIG. 4 is a diagram showing an output of a digital low-pass filter having a cutoff frequency of 7 kHz.

FIG. 5 is a diagram showing an output of a digital low-pass filter having a cutoff frequency of 4 kHz.

FIG. 6 is a diagram illustrating an output of a digital low-pass filter having a cutoff frequency of 2.5 kHz.

FIG. 7 is a diagram showing the output of the delay unit.

FIG. 8 is a diagram showing an output of a selection unit.

FIG. 9 is an explanatory diagram showing the operation of the extracting means.

FIG. 10 is a diagram showing the output of the adder.

FIG. 11 is a diagram showing an output of a subtractor.

FIG. 12 is a diagram showing an output of a correction unit.

FIG. 13 is a diagram illustrating a waveform obtained by passing an output of a correction unit through a D / A converter.

FIG. 14 is a diagram showing a waveform obtained by passing an output of a correction unit through a D / A converter and an analog low-pass filter.

FIG. 15 is a circuit diagram showing a modification of the extracting means and the correcting means.

FIG. 16 is a circuit diagram showing another modification of the extracting unit and the correcting unit.

FIG. 17 is a circuit diagram showing still another modified example of the extracting means and the correcting means.

FIG. 18 is a circuit diagram showing still another modified example of the extracting means and the correcting means.

FIG. 19 is a block diagram of a conventional CD-WO recorder.

FIG. 20 is a diagram illustrating an example of an analog audio signal.

21 is a diagram showing a waveform obtained by A / D converting the analog audio signal of FIG. 20.

FIG. 22 shows a digital audio signal of FIG.
FIG. 4 is a diagram illustrating a converted waveform.

FIG. 23 shows the waveform of FIG. 22 cut off at a frequency of 20 kHz.
FIG. 3 is a diagram showing a waveform passed through an analog low-pass filter of FIG.

24 is a diagram showing a waveform obtained by passing the waveform of FIG. 22 through an analog low-pass filter having a cutoff frequency of 3 kHz.

[Explanation of symbols]

2 Counter 3, 4, 5 Digital low-pass filter 6 Selection means 11, 11B, 11C, 11D Extraction means 14, 14A, 14B, 14C, 14D Correction means 51 A / D converter 52 DIR 53 Selector 54A System controller 55A Operation unit 56 encoder 57 EFM signal recording / reading circuit 58 optical disk 59 decoder 60 D / A converter 61 input source detection circuit 62 effective word length detection circuit 80 data correction unit 81, 82 selector 83 quantization distortion reduction circuit

Claims (18)

[Claims] 1. A / D conversion means for A / D converting an analog audio signal inputted from the outside into audio data having an effective word length = n, and an effective word length = n '(n'<
n) receiving means for receiving a transmission signal containing audio data and outputting the received audio data, source setting means for setting the type of recording source, and output from the A / D conversion means during recording. Recording signal processing means for forming a recording signal of a predetermined format including audio data of a source of the type set by the source setting means and various control information related to the audio data in an output of the receiving means; Recording / reading means for recording a recording signal on a predetermined recording medium during recording, and reading / recording the recording signal recorded on the recording medium during reproduction, and audio data and various control information from the recording signal read from the recording medium during reproduction. And a playback signal processing means for restoring and outputting the audio signal. Effective word length information generating means for generating effective word length information representing the effective word length of the data and outputting the effective word length information to the recording signal processing means as one of the control information; Based on the effective word length information in the control information related to the audio data, if the effective word length information indicates n bits, the restored audio data is output as it is, and the effective word length information is n ′ bits. And data correction means for outputting the corrected audio data through the restored audio data to the quantization distortion reduction means for extending the effective word length by (n-n ') to the lower side. Recording / reproducing apparatus characterized by the above-mentioned. 2. A recording signal processing means comprising: compressed audio data obtained by compressing audio data of a source of a type set by a source setting means among output of an A / D conversion means and output of a receiving means; A recording signal of a predetermined format including various control information related to the audio data is formed, and the reproduction signal processing means decompresses the compressed audio data from the recording signal read from the recording medium and further decompresses the audio data to recover the compressed audio data. The recording / reproducing apparatus according to claim 1, wherein the recording / reproducing apparatus is restored. 3. The quantization distortion reducing means inputs the restored audio data formally with the word length extended to n bits or more, extracts low-frequency components below a predetermined cutoff frequency, and extracts the effective word length. A digital filter for outputting n-bit audio data, a counting means for counting the number of points having the same value before and after each point of the restored audio data, and a restored audio based on the counting result of the counting means. In the section where the count value is equal to or less than a fixed value, the restored audio data whose word length is formally expanded to n bits is output,
3. The recording / reproducing apparatus according to claim 1, further comprising: selecting means for selecting and outputting audio data output from the digital filter in a section where the count value is equal to or greater than a predetermined value.
Playback device. 4. A plurality of digital filters are provided, and each digital filter is provided with a different cutoff frequency. The selecting means includes a section in which the count value counted by the counting means is equal to or less than a predetermined value, the word length is formally n. Outputs the restored audio data in a form expanded to bits, and in the section where the count value is equal to or greater than a certain value, as the count value is larger, audio data output from a digital filter with a lower cutoff frequency is selectively selected. The recording / reproducing apparatus according to claim 3, wherein: 5. The apparatus according to claim 3, further comprising: extracting means for extracting a discontinuous point generated in the output of the selecting means, and correcting means for making the discontinuous point in the output of the selecting means continuous. 4. The digital recording device according to 4. 6. A source setting means for automatically setting a recording source based on a detection result by an input source detection means for detecting a source having an input among an analog audio source and a digital audio source. The recording / reproducing apparatus according to claim 1, 2 or 3, wherein: 7. The source setting means includes an instruction operating means for instructing detection of a source having an input, and an input source detecting means for detecting a source having an input. 4. The recording / reproducing apparatus according to claim 1, wherein a recording source is automatically set based on a detection result of the input source detecting means. 8. The receiving means according to claim 1, wherein the receiving means receives a transmission signal including audio data having an effective word length = n or n ′ (n ′ <n) from outside. Recording / reproducing apparatus according to the above. 9. The effective word length information generating means, when an analog audio source is set by the source setting means,
n, and generates effective bit length information indicating the digital audio source.
Effective word length information is generated based on the selection result by the effective word length selecting operation means for performing one of the selection operations of n and n ', or an effective word length detection for detecting an effective word length of audio data of a digital audio source. 9. The recording / reproducing apparatus according to claim 8, wherein effective word length information is generated based on a detection result of the means. 10. The source setting means includes an instruction operating means for instructing detection of an input source, and an input source detecting means for detecting a source having an input, and the input detection at the time when the input source is instructed to be detected. 9. The recording / reproducing apparatus according to claim 8, wherein a recording source is automatically set based on a detection result of the means. 11. The effective word length information generating means includes an instruction operating means for instructing reading of an effective word length, and an effective word length detecting means for detecting an effective word length of audio data received from a digital audio source, When the digital audio source is set by the source setting means, the effective word length information is generated based on the detection result of the effective word length detecting means at the time when the instruction operation means instructs to read the effective word length. 11. The recording / reproducing apparatus according to claim 8, wherein: 12. Effective word length = n or n ′ (n
'<N) receiving a transmission signal including audio data;
Receiving means for outputting the received audio data,
At the time of recording, a recording signal processing means for forming a recording signal of a predetermined format including audio data output from the receiving means and various control information related to the audio data, and at the time of recording, the recording signal is recorded on a predetermined recording medium. Recording / reading means for recording and reading a recording signal recorded on a recording medium during recording and reproduction, and reproduction signal processing for restoring and outputting audio data and various control information from the recording signal read from the recording medium during reproduction Means for generating effective word length information indicating the effective word length of the audio data received by the receiving means during recording, and outputting the generated effective word length information to the recording signal processing means as one of the control information. Effective word length information generating means; and, for reproduction, the effective word length in the control information associated with the audio data restored by the reproduction signal processing means. If the effective word length information indicates n bits, the restored audio data is output as it is, and if the effective word length information indicates n ′ bits, the effective word length is shifted to lower (n− a data correction means for outputting audio data obtained by performing data correction through restored audio data to quantization distortion reduction means extending by n ′). 13. A recording signal processing means for forming a recording signal of a predetermined format including compressed audio data obtained by compressing audio data received by a receiving means and various control information related to the compressed audio data, 13. The recording / reproducing apparatus according to claim 12, wherein the signal processing means restores the compressed audio data from the recording signal read from the recording medium and further expands the audio data to restore the audio data. 14. A quantization distortion reduction means for inputting the restored audio data formally with a word length extended to n bits or more, extracting a low-frequency component below a predetermined cutoff frequency, and extracting an effective word length. A digital filter for outputting n-bit audio data, a counting means for counting the number of points having the same value before and after each point of the restored audio data, and a restored audio based on the counting result of the counting means. In the section where the count value is equal to or less than a fixed value, the restored audio data whose word length is formally expanded to n bits is output,
14. The recording / reproducing apparatus according to claim 12, further comprising: selecting means for selecting and outputting audio data output from the digital filter in a section where the count value is equal to or greater than a predetermined value. 15. A digital filter comprising a plurality of digital filters, each digital filter having a different cutoff frequency, and a selecting means for which the word length is formally n for a section in which the count value counted by the counting means is less than a certain value. Outputs the restored audio data in a form expanded to bits, and in the section where the count value is equal to or greater than a certain value, as the count value is larger, audio data output from a digital filter with a lower cutoff frequency is selectively selected. The recording / reproducing apparatus according to claim 14, wherein: 16. An apparatus according to claim 13, further comprising: extracting means for extracting a discontinuous point generated in the output of the selecting means, and correcting means for continuousizing the discontinuous point in the output of the selecting means. 15. The recording / reproducing apparatus according to 14. 17. The effective word length information generation means generates effective word length information based on a selection result by an effective word length selection operation means for selecting one of n and n ', or a reception means. 15. The recording / reproducing apparatus according to claim 12, wherein effective word length information is generated based on a detection result by an effective word length detecting means for detecting an effective word length of received audio data. apparatus. 18. An effective word length information generating means includes instruction operation means for instructing reading of an effective word length, and effective word length detecting means for detecting an effective word length of audio data received by a receiving means. 15. The effective word length information is generated based on the detection result of the effective word length detecting means at the time when the reading of the effective word length is instructed by the operating means, wherein the effective word length information is generated. Recording / playback device.