JPH02134769A - Digital audio tape recorder - Google Patents

Abstract

PURPOSE:To attain the recording with fidelity at all times by changing over a switch so as to be thrown to a position of a required recording system when a copy inhibit signal is detected from a digital signal inputted to a digital-in terminal. CONSTITUTION:When an input fed to a digital-in terminal 41 of a digital audio tape recorder DAT is a digital audio signal from a Compact Disk player and includes a copy inhibit code, the code is detected and switches SW1 - SW7 are changed over by a code detection circuit 61. Then the input data demodulated by the circuit 61 is recorded via the recording system comprising the switch SW3, a D/A converter 52, an LPF 53, the switch SW1, an A/D converter 24, the switch SW2, a signal processing circuit 25 and a recording circuit 26 and since only one LPF 53 is passed after the converter 52, the recording with fidelity is attained. When no inhibit code is detected, the recording system via a demodulator 42, the switch SW2 and the circuit 25 is used to attain digital recording with fidelity at all times.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a digital audio tape recorder.

[Prior Art] There are audio devices that can output audio signals in the form of digital signals, such as compact disc players (CD players), digital audio tape recorders (DAT), and satellite broadcast tuners (BS tuners). The DAT has a digital in terminal and can record digital audio signals from such digital audio equipment.

By the way, the digital audio signal output from a CD player contains a copy prohibition code, and conventionally,
It was not possible to record this digital audio signal by supplying it to the digital in terminal of the DAT. Therefore, the analog audio signal obtained from the line-out terminal of the CD player is normally supplied to the line-in terminal of the DAT for recording.

FIG. 5 is a system diagram showing one example, in which 10 is a CD player and 20 is a DAT.

The audio signal reproduced by the CD player 10 is converted into an analog signal by the D/A converter 11, and its band is limited by the low-pass filter 12, and then guided to the line-out terminal 13. The analog audio first word outputted to the line-out terminal 13 is supplied to the line-in terminal 21 of the DAT 20.

The recording level of the audio signal supplied to the line-in terminal 21 is appropriately adjusted by a volume 22, and then band-limited by a low-pass filter 23. This band-limited audio signal is sent to the A/D converter 2.
A/4 is supplied to A/4 with a predetermined sampling frequency.
D conversion processing is performed. The digital audio signal output from the A/D converter 24 is digitally recorded by being supplied to a rotating magnetic head device (not shown).

Here, the low-pass filter 23 provided in the DAT 20
To avoid aliasing distortion during A/D conversion,
It is provided to remove the high frequency components.

[Problems to be Solved by the Invention] By the way, when digitally recording an analog audio signal obtained from a CD player 10 as a source as shown in FIG. It is necessary to provide .23.

As a result, there is a drawback that the sound quality of the audio signal to be recorded on the DAT 20 deteriorates.

Therefore, the present invention proposes a digital audio chip recorder that is capable of high-fidelity digital recording.

[Means for Solving the Problems] The present invention provides a first recording system in which a digital signal supplied to a digital input terminal is subjected to signal processing by a signal processing circuit and recorded; A D/A converter converts the digital signal into an analog signal, and after limiting the analog signal to band '#1', the A/D converter converts it to a digital signal, and the signal processing circuit processes the digital signal. a second recording system configured to record a copy prohibition code, and code detection means for detecting a copy prohibition code from a digital signal supplied to a digital input terminal; The first recording system is switched to the first recording system, and when copy inhibition is detected, the second recording system is switched to the second recording system.

[Function] In the above configuration, when a copy prohibition code is detected from the digital signal supplied to the digital in terminal, the digital signal supplied to the digital in terminal is converted into an analog signal by the D/A converter. After band-limiting, this analog signal is converted into a digital signal by an A/D converter, and this digital signal is processed by a signal processing circuit and recorded. Therefore, since the signal is simply passed through a single low-pass filter after being D/A converted, deterioration in sound quality due to band limitation is reduced.

[Embodiment] An embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a system diagram showing the main parts of a digital audio recorder (DAT) 20. As shown in FIG.

In the figure, reference numeral 21 is a line-in terminal, and the analog signal supplied here is passed through a volume 22 and a low-pass filter 23 for band limitation, and then passed through a selector switch SWI.
is supplied to the fixed terminal on the a side. This changeover switch SW
The output signal of I is supplied to the A/D converter 24 and converted into a digital signal, and then the changeover switch SW2 is switched to a.
ll! Supplied to the fixed terminal of II. The output signal of this changeover switch SW2 is supplied to a signal processing circuit 25 and subjected to signal processing such as error correction. and,
The output signal of the signal processing circuit 25 is supplied to a rotating magnetic head device 27 via a recording circuit 26, thereby being recorded on a magnetic tape 28.

Further, the digital signal passed through the signal processing circuit 25 is
The signal is supplied to the fixed terminal on the a side of the changeover switch SW4, and is also supplied to the modulation circuit 30 of the pi-phase mark to be modulated, and then supplied to the digital out terminal 31.

Further, 41 is a digital in terminal, and a digital signal in the format of a digital audio interface (EIAJ standard) supplied thereto is supplied to a demodulation circuit 42 of the biphase mark and demodulated. In this case, the digital signal is further supplied to the clock regeneration circuit 43, and a sampling clock (44° 1KH2 in this example) that is similar to the human-powered digital signal generated by the clock regeneration circuit 43 is supplied to the demodulation circuit 42. demodulated.

The output signal of this demodulation circuit 42 is transmitted through changeover switches S to V2.
is supplied to the fixed terminal on the b side of the selector switch S.
Supplied to the fixed terminal of b III of W4. The output signal of this changeover switch SW4 is supplied to a D/A converter 52, converted into an analog signal, and then band-limited by a low-pass filter 53. The output signal of this low-pass filter 53 is supplied to the line-out terminal δ1, and
The signal is supplied to the b-side fixed terminal of the changeover switch SW1 via a fade-in/fade-out volume 54.

Further, the sampling clock generated by the clock regeneration circuit 43 is supplied to the a-side fixed terminal of the changeover switch SW3. Fixed terminals on the a side and b side of this changeover switch SW3 are connected to each other via a connection switch SW5, and the sampling clock output from this changeover switch SW3 is supplied to the D/A converter 52.

Further, 35 is a signal generating means, and this signal generating means 3
The sampling clock generated at step 5 is supplied to the b-side fixed terminals of the changeover switches S to V6.

The fixed terminal on the a side of this changeover switch SW6 and its movable terminal are connected via a connection switch SW7, and the a
The fixed terminal on the side is connected to the fixed terminal on the b side of the changeover switches S to V3. The sampling clock output from the changeover switch sw6 is supplied to the A/D converter 24 and the signal processing circuit 25.

Further, 61 is a code detection circuit, and the code detection circuit 61 is supplied with the digital signal supplied to the digital in terminal. This code detection circuit 61 detects a copy prohibition code included in the digital signal. In the digital audio interface format, bit 2 of the channel status contains a copy prohibition code; a low level of ``0'' prohibits copying, and a high level of ``1'' allows copying. When the signal is supplied, the changeover switches S to V2, SW4.S'vV6.Connection switch SW5 are controlled by the detection signal of the code detection circuit 61.

That is, when a digital signal is supplied to the digital in terminal 41, the changeover switches S' and VI are connected to the b side, the changeover switch Sw3 is connected to the a side, and the connection switch SW7 is turned off. When copy prohibition is detected, the changeover switch SW2 is connected to the a side, the changeover switches SW4, 3W6 are connected to the b side, and the connection switch SW5 is turned off.On the other hand, when copy permission is detected, The changeover switch SW2 is connected to the b side, and the changeover switch SW4. SW6 is connected to the a side, and the connection switch SW5 is turned on.

Note that when an analog signal is supplied to the line-in terminal 21, the changeover switch SW1. SW2. SW4 is connected to the a side, changeover switch SW3.5W6 is connected to the b side, connection switch SW5 is turned off, and connection switch SW
7 is turned on.

In the above configuration, when a digital signal is supplied to the digital in terminal 41 and copy prohibition is detected by the code detection circuit 61, the selector switch SWI
~SW4. SW6. Connection switch SW5゜SW
7 is controlled as shown in FIG.

In this case, the signal is recorded or output via the following path. For convenience of explanation, only the symbols of the signal paths are shown.

41→42→SW4→52→53→54→SWI→24
→SW2→25→26→27 As a result, the digital signal supplied to the digital in terminal 41 is -d
/A7R conversion, A/D conversion again, and digital recording.

41→42→SW4→52→53→54→SWI→24
→SW2→25→30→31 As a result, the digital signal supplied to the digital in terminal 41 is digitized again and output to the digital out terminal 31.

41→42→SW4→52→53→51 As a result,
The digital signal supplied to the digital in terminal 41 is converted into an analog signal and outputted to the line out terminal 51.

In such a signal processing path, the demodulation circuit 42 includes:
A sampling clock generated by a clock recovery circuit 43 is supplied. Similarly, the D/A converter 52 is also supplied with the sampling clock generated by the clock recovery circuit 43.

As a result, the digital signal is connected to the digital signal supplied to the digital input terminal 41.
/A converted.

In addition, the A/D converter 24 and the signal processing circuit 25 include
A predetermined sampling clock generated by the signal generating means 35 is supplied. As a result, A/D conversion processing and signal processing are performed in accordance with the DAT format.

By providing independent signal generation means 35 and clock regeneration circuit 43, even if the digital signal is supplied to digital input terminal 41, it can be converted into D/A converter and A/D converter according to the respective signal format. Conversion processing can be performed.

Further, when a digital signal is supplied to the digital in terminal 41 and copy permission is detected by the code detection circuit 61, the changeover switches SW1 to SW4,
SW6, connection switches SW5 and SW7 are controlled as shown in FIG.

In this case, the signal is recorded or output via the following path. For convenience of explanation, only the symbols of the signal paths are shown.

41 → 42 → SW2 → 25 → 26 → 27 As a result, the digital signal supplied to the digital in terminal 41 is directly supplied to the signal processing circuit 25 via the demodulation circuit 42 for signal processing, and then passed through the recording circuit 26. Recorded digitally.

41→42→5W2-1-25→30→31 As a result, the signal supplied to the digital in terminal 41 is outputted to the digital out terminal 31 as a digital signal.

41 → 42 → SW2 → 25 → SW4 → 52 → 53 51 As a result, the digital signal supplied to the digital in terminal 41 is converted to analog and sent to the line out terminal 51.
is output to.

In such a signal processing path, the demodulation circuit 42 and the signal processing circuit 25 are supplied with a sampling clock generated by the clock recovery circuit 43.

Thereby, signal processing is performed in synchronization with the digital signal supplied to the digital in terminal 41.

Further, the D/A converter 52 is also supplied with a sampling clock generated by the clock recovery circuit.

As a result, the digital signal is synchronized with the digital signal supplied to the digital in terminal 41.
/A converted.

Further, when an analog signal is supplied to the line-in terminal 21, selector switches SW1 to SW4. SW6 and connection switches SW5.3W7 are controlled as shown in FIG.

In this case, the signal is recorded or output via the following path. For convenience of explanation, only the symbols of the signal paths are shown.

21 →22→23→SWI →24→SW2 →
25→26→27 As a result, the analog signal supplied to the line-in terminal 21 is digitized by the A/D converter 24, and then digitally recorded through predetermined signal processing.

21 →22→23→SW 1 →24→SW2
→25→30→31 As a result, the analog (word) supplied to the line-in terminal 21 is digitized and output to the digital-out terminal 31.

21 → 22 → 23 → SWI → 24 → S ~ V2 → 25 → S
W4→52-+53→51 As a result, the analog signal supplied to the line-in terminal 21 is converted into an analog signal again and sent to the line-out terminal 51.
is output to.

In such a signal processing path, an A/D converter 24,
The signal processing circuit 25 and the D/A converter 52 are supplied with a sampling clock generated by the signal generating means 35. As a result, A/D conversion processing, signal processing, and D/A conversion processing are performed in accordance with the DAT format.

Thus, according to this example, when a copy prohibition code is detected from the digital signal supplied to the digital in terminal, the digital signal supplied to the digital in terminal is converted into an analog signal by the D/A converter a 52. This analog signal is band-limited by a low-pass filter 53, then converted to a digital signal by an A/D converter 24, and this digital signal is processed by a signal processing circuit 25 and recorded.

Therefore, since the signal is simply passed through a single low-pass filter 53 after being D/A converted, deterioration in sound quality due to band limitation can be reduced, and high-fidelity digital recording can be performed.

Also, according to this example, the volume for fade-in and fade-out is set to the maximum level of 1! ! By keeping things organized, you can record digitally at an appropriate level.

Furthermore, since data processing is performed within the DAT using a plurality of sampling clocks that differ depending on the source source, the digital signal reproduced from the source source to be digitally recorded, for example, a CD player, can be used as is. .

[Effects of the Invention] As explained above, according to the present invention, when a copy prohibition code is detected from the digital signal supplied to the digital input terminal, the digital signal supplied to the digital input terminal is The converter converts it into an analog signal, and this analog signal is band-limited and then sent to the A/
It is converted into a digital signal by a D converter, and this digital signal is processed by a signal processing circuit and recorded. Therefore, since the signal is simply passed through a single low-pass filter after being D/A converted, deterioration in sound quality due to band limitation can be reduced, and high-fidelity digital recording can be performed.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of the main parts showing one embodiment of this invention;
4 to 4 are diagrams showing the signal recording path, and FIG. 5 is a system diagram of main parts for explaining the conventional example. 10...CD player 20...DAT 21...Line-in terminal 24...A/D converter 25...Signal processing circuit 26...Recording circuit 27...Rotating magnetic head device 31... ...Digital out terminal 35...Signal generating means 41...Digital in terminal 42...Demodulation circuit 51...Line out terminal 52...D/A converter 53...Low pass filter 54...・Volume SWI~SW4 for fade in/fade out. SW6 φ...Selector switch SW5.
SW? ...Fist connection switch patent applicant Iwa Co., Ltd.

Claims (1)

[Claims] (1) A first recording system in which the digital signal supplied to the digital in terminal is processed and recorded by a signal processing circuit, and the digital signal supplied to the digital in terminal is processed by a D/A converter. A second recording system in which the analog signal is converted into an analog signal by the A/D converter, the analog signal is band-limited, the analog signal is converted into a digital signal by an A/D converter, and the digital signal is processed by a signal processing circuit and recorded. and code detection means for detecting a copy prohibition code from the digital signal supplied to the digital in terminal, and when the code detection means detects copy permission, the recording system is switched to the first recording system, and A digital audio tape recorder characterized in that when copy prohibition is detected, switching is made to the second recording system.