JPH04176060A - Recording and reproducing apparatus - Google Patents

Abstract

PURPOSE:To secure sufficient S/N and a dynamic range by providing an A/D converter circuit and a D/A converter circuit whose quantizing bit number exceeds 16, and performing recording and reproduction by the quantization exceeding 16 bits. CONSTITUTION:In a 20-bit analog/digital converter circuit means 41, input analog audio signals of a specified channel are sampled by quantization exceeding 16 bits. The sampled data are divided into two parts for upper bits and lower bits with a recording and reproducing amplifier means 7. The data are assigned and recorded in signal recording regions for 2 channels. The digital audio signals are demodulated and decoded in the recording and reproducing means 7 in reproduction. Thereafter, the signals are converted into the analog signals in a 20-bit digital/analog converter means 42 exceeding 16 bits. Thus, the sufficient S/N and the dynamic range can be secured.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is directed to a rotary head type digital audio recorder (hereinafter referred to as "digital audio recorder") which converts an analog audio signal into a digital signal, records it on a magnetic tape, and reproduces the recorded digital signal. , DAT).

[Prior Art] The DAT signal format is described in the Japan Electronics Industry Association standard CP-2305, and DATs that record and reproduce high-quality digital audio signals based on this format are already commercially available.

FIG. 3 is a schematic block diagram showing the entirety of such a conventional DAT. The configuration and operation of a conventional DAT will be explained using FIG.

During recording, left (L) channel and right (R) channel analog audio signals are externally input from the analog signal input terminal l, and the input analog audio signals are passed to a low-pass filter 2A (hereinafter referred to as LPF). bandwidth is limited.

The band-limited analog audio signal is given to a 16-bit analog/digital conversion circuit (hereinafter referred to as A/D conversion circuit) 3, where it is converted into a 16-bit digital audio signal using a sampling clock signal. After that, the data is stored in the memory circuit 4.

The encoding circuit 5 adds a test signal for error correction and detection to the digital audio data stored in the memory circuit 4.

The digital audio data to which the error correction/detection code has been added is supplied to the modulation circuit 6, where it is digitally modulated and converted into a data string suitable for recording.

The modulated digital audio signal is amplified by the recording amplifier 7a of the recording/reproducing amplifier 7, and then passed through the rotary transformer (
(not shown) to two rotating rads 8A and 8B mounted 180 degrees opposite to each other on the rotary drum 9, and recorded on the magnetic tape 10 in a predetermined format.

During reproduction, the digital signals reproduced by the rotary heads 8A and 8B are input to the reproduction amplifier 7b of the recording and reproduction amplifier 7 via a rotary transformer (not shown), where they are amplified and sent to the next stage demodulation circuit. 11 and servo times! 15.

In the demodulation circuit 11, the modulated digital signal is demodulated into the original baseband signal, and the demodulated output is given to the memory circuit 4.

The decoding circuit 12 performs error correction and error detection on the reproduced digital audio data stored in the memory circuit 4.

The error-corrected digital audio signal read out from the memory circuit 4 is given to a 16-bit digital/analog conversion circuit (hereinafter referred to as a D/A conversion circuit) 13, where the original signal is converted by a sampling clock signal. converted to an analog audio signal.

The converted analog audio signal is sent to the L and R channel analog signal output terminals 1 through the LPF 2B.
4 is output to the outside.

The rotating drum 9 normally has a diameter of 30 mm and rotates at 2000 PPM during recording and reproduction.

The magnetic tape 10 is wound around the rotating drum 9 at an angle of 90 degrees, and runs at a speed of 8.15 am and 7 sec as a capstan (not shown) rotates.

A drum motor (not shown) is provided to rotate the rotating drum 9, and a capstan motor (not shown) is provided to rotate the capstan.These rotations are controlled by a servo circuit 15. It is being done.

During playback, the servo circuit 15 generates an error signal from the signal recorded on the magnetic tape 10 to control the rotation of a capstan motor (not shown), so as to accurately follow the signal track. There is.

The system control circuit 16 controls the entire system according to the operating mode number specified by the input key 17.

The signal track of the DAT has an area in which a subcode signal related to the digital audio signal that is the main signal is recorded, and the system control circuit 16 also performs signal processing of this subcode signal.

During recording, a subcode signal is generated by the system control circuit 16 and provided to the memory circuit 4. The encoding circuit 5 also adds error correction and error detection codes to the subcode signal. The subcode signal to which the error correction and error detection codes are added is modulated and then recorded in a predetermined area of the signal track.

During playback, the playback subcode signal is read out from the memory circuit 4 and displayed on the display 18.

The clock generation circuit 19 is a circuit that generates and supplies lock signals to various parts as necessary.

Next, the format of the signal recorded on the magnetic tape IO will be explained using FIG.

Two rotating heads 8 attached to a rotating drum 9
A and 8B have an azimuth angle of 20 degrees to each other,
Track 23A (+azimuth track) in FIG. 4 is recorded by the rotating head 8A having a + (plus) azimuth angle, and track 23B (-azimuth track) is recorded by the rotating head 8B having a - (minus) azimuth angle. recorded.

One track records a digital audio signal, which is the main signal, and a test signal for error correction.
A CM signal area 24, an ATF signal area 25 where a tracking servo control signal is recorded, and a subcode signal area 26 where a subcode signal related to the main signal is recorded. Areas for recording signals of a constant frequency are provided at the beginning and end of the track.

FIG. 5 is a diagram showing the block format of the PCM signal area 24. In this FIG. 5, 27 is a synchronization signal, 28 is an ID code', 29 is a block address, and 30
For example, this is an area where parity signals for detecting errors in ID code 2B and block address 29 are recorded.
Consists of bits.

31 is an area where digital audio signals (PCM data) and error correction test signals are recorded, and is composed of 256 bits, with a total number of bits per block of 2.
It will be 88 bits.

The format in which the ID code 28 is recorded is shown in Table 1. As shown in Table 1, four PCM blocks are used to record the various ID codes.

<Table 1> In Table 1, "00" is recorded for TD when a digital audio signal is recorded as the main signal.

Further, in the area where the frame address is recorded, the value goes around every 16 frames (32 tracks).

Important information such as the sampling frequency of the system and the number of quantization bits is recorded in each 2-bit area from IDI to ID7.

Table 2 shows the bit allocation for IDI to fD7.

<Table 2> (ID7 bit assignment from IDI) In this Table 2, ID2 is information for identifying the sampling frequency, and DAT is 48 KHz and 44.1 KHz.

It supports three types of sampling frequencies of 32KHz.

ID4 is information identifying the number of quantization bits, and DA
T corresponds to 16-bit linear quantization and 12-pin nonlinear quantization. The sampling frequency is 32Hz,
When quantization is 12-bit non-linear, 4-channel recording (usually 2 channels, identified by ID3), or long-time recording (LP mode, drum rotation speed and tape running speed are half of normal, recording and playback time will be doubled)
is now possible.

The recording position of digital audio data on the PCM signal area 24 will be explained. When the quantization is 16-bit linear, the digital audio signals of the two channels L and R are transferred to the +azimuth track 23A, as shown in FIG.
, the even-numbered sampling data of the L channel (L-ev
en) and the odd-numbered sampling data of the L channel (R-
odd) is recorded, and the even-numbered sampling data (R-even) of the L channel and the odd-numbered sampling data (L-ocld) of the L channel are recorded on the azimuth track 23B.
) are recorded.

As shown in FIG. 4, the signal recording format is such that the digital audio data is arranged in two tracks. Note that Q in FIG. 4 is an area where a test signal for error correction is recorded.

So far, we have explained the recording and playback operations of externally input analog audio signals.
Recording and reproduction of a digital audio signal input from the digital signal input terminal 21 shown in FIG. 3 will be described.

Digital data input from the digital signal input terminal 21 is defined as a digital audio interface formant by the Japan Electronics Industry Association standard CP-340.

This digital audio interface format will be explained using figures.

FIG. 6 is a signal configuration diagram of a subframe of the digital audio interface format, and is composed of 32 bits of information.

In FIG. 6, 34 is a synchronization preamble, 35 is an auxiliary signal, and 36 is an audio signal transmission area.

The audio signal transmission area 36 is 20 bits, and the auxiliary signal transmission area 35 is 4 bits, and these two areas transmit digital audio data of up to 24 bits.

Numeral 37 is a validity flag V indicating the authenticity of the digital audio data to be transmitted, 38 is a user data bit U, and 39 is a channel status bit C14o is a parity bit P for error detection.

In order to transmit a subframe as shown in FIG. 6 as a two-channel signal, one frame is composed of two subframes, channel 1 and channel 2, as shown in FIG. One block is constructed.

To identify the starting point and channel of each block, three types of synchronization preambles are used: synchronization preamble B for the channel 1 subframe at the beginning of the block, and synchronization preamble B for the other channel 1 subframes. ,
A synchronization preamble M and a synchronization preamble W are used for all channel 2 subframes.

During recording, a signal in the format described above is inputted from the digital signal input terminal 21 shown in FIG. 3 and applied to the digital interface circuit 2o.

The digital interface circuit 2o extracts digital audio data from the input signal and outputs it to the memory circuit 4.

Thereafter, the same processing as that for recording the analog input signal described above is performed, and the signal is recorded on the magnetic tape 1o.

During playback, data that has been error-corrected by the decoding circuit 12 is given to the digital interface circuit 20, where it is converted into a predetermined digital audio interface formant and then output to the outside through the digital signal output terminal 22. Output.

[The problem that the invention aims to solve! t) Conventional DAT has a quantization bit number of 16 bits linear and 1
It supports two types of 2-bit non-linear, but especially in the world of professional digital audio equipment, 16-bit nonlinear
Bit-linear quantization has the problem of not being able to secure sufficient S/N and dynamic range; for example, PCM recorders that record and playback using 20-bit linear quantization have already been put into practical use. has been done.

This invention was made to solve the above-mentioned problems, and it can record and play back with quantization exceeding 16 bits, and fully satisfies the demands of the world of professional digital audio equipment. The object of the present invention is to obtain such a recording/reproducing device.

(Means for Solving il) A recording/reproducing apparatus according to the present invention samples an input analog audio signal of a predetermined channel using quantization exceeding 16 bits, and sets the sampled data to an upper focus. An analog/digital conversion means that divides the lower bits into two, and this analog/digital conversion means allocates them to the signal recording area for two channels in the DAT, records digital audio on the recording medium, and converts the digital audio during playback. The recording and reproducing means demodulates and decodes the signal, and the digital/analog converting means converts the audio signal decoded by the recording and reciprocating means into the original analog audio signal.

[For production]

16 in the analog/digital conversion means in this invention
The input analog audio signal of a predetermined channel is sampled by quantization exceeding bits, and the sampled data is divided into two into upper bits and lower bits by a recording/reproducing means, and allocated to a signal recording area for two full channels. and record it.
At the time of reproduction, the digital audio signal is demodulated and decoded by the recording and reproducing means, and then converted into an analog signal by the digital/analog converting means exceeding 16 bits, thereby providing audio performance with sufficient S/N and dynamic range.

〔Example〕

Embodiments of the recording/reproducing apparatus of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of one embodiment.

The DAT shown in Fig. 1 is different from the conventional DAT shown in Fig. 3.
The configuration is almost the same as that of AT, but an A/D conversion circuit 41 as an A/D conversion means and a D/A as a D/A conversion means are used.
The conversion circuit 42 has a quantization bit number of 20 bits. The rest of the structure is the same as that in FIG. 3, and the same parts as in FIG. 3 are denoted by the same reference numerals, and the explanation of the structure will be omitted.

Next, the recording and reproducing operations of the DAT according to the present invention shown in FIG. 1 will be explained. During recording, one channel of analog audio signal is input from the outside through the analog signal input terminal 1, and its frequency band is limited by the next stage LPF 2A. The band-limited analog audio signal is provided to an A/D conversion circuit 41.

The A/D conversion circuit 4 converts the input analog audio signal into a 20-bit digital audio signal using the sampling clock signal.

The digital audio signal 20 bits quantized by this A/D conversion circuit 41 is given to the memory circuit 4 and stored there.

At this time, the digital audio data to be stored is divided into even numbered sampling data (S-even) and odd numbered sampling data (5-odd), and further, even numbered data (S-even). is divided into the upper 16-bit data (S-even, upper) and the lower 4-bit data (S-even, lower), and the odd-numbered data (5-odd) is similarly the upper 16-bit data (S-even, lower). 5-odd, upper) and lower 4-bit data (S-odd, lower).

Data of the top 16 bits of even-numbered data (5-ev
erzupper) and the lower 4 bits of data (S-ev
en, lower) is, for example, a storage area for L channel audio data in a conventional DAT.
The upper 16 bits of odd-numbered data (5-od
d, upper) and the lower 4 bits of data (S-odd
, lower) are stored in the audio data storage area of the R channel.

The digital audio signal stored in the memory circuit 4 is added with a test signal for error correction and detection by an encoding circuit 5, and is provided to a modulation circuit 6.

The digital audio signal modulated by the modulation circuit 6 is amplified by the recording amplifier 7a of the recording/reproducing amplifier 7, and is transferred to a magnetic tape as a storage medium by two rotary heads 8A and 8B via a rotary transformer (not shown). recorded on 10.

FIG. 2 shows the recording position of digital audio data on a magnetic tape 10 according to the present invention.

As shown in FIG. 2, for example, +azimuth track 23
In the first half of the PCM signal area 24 of A, data of the upper 16 bits of even-numbered data (S-eVenl up
er) is shown in the second half of the data of the lower 4 pints of the even-numbered data (S-eVenllower) and the data of the lower 4 pints of the odd-numbered data (S~odd,
lower) is recorded, -azimastra, ri23
B (7) P CM (f number sNM24 (7) In the first half, the data of the lower 4 bits of the even numbered data (S-e
ven.

lower) and the lower 4 bits of odd-numbered data (S-odd, lower) are in the second half,
The upper 16 bits of odd-numbered data (S o
dd.

upper) is recorded.

During playback, the digital audio signals recirculated by the rotary heads 8A and 8B are input to the recirculation amplifier of the recording/reproducing amplifier 7 via a rotary transformer (not shown), amplified, and then applied to the demodulation circuit l]. The signal is then demodulated to the original baseband signal.

The demodulated digital audio signal is temporarily stored in the memory circuit 4, and the decoding circuit 12 detects and corrects errors.

The error-corrected 20-bit digital audio signal is given to the 20-bit D/A conversion circuit 42, where it is converted into the original analog audio signal by the sampling clock signal, and then outputted as an analog signal via the LPF 2B. The signal is output from the terminal 14 to the outside.

Next, recording and retransmission of digital signals inputted from the digital signal input terminal 21 will be explained.

During recording, one channel of digital audio data transmitted in a digital audio interface format and having a word length of 24 bits, for example, is extracted by the digital interface circuit 20,
Memory times! 84 and stored here.

At this time, the digital audio data to be stored is the even-numbered data (
5-even) and odd-numbered data (5-odd).
n) is the upper 16 bits of data (5-even, up
per) and the lower 8 bits of data (S-eVenl
lower ).

The odd-numbered data (S-0dd) is also divided into upper 16-bit data (S-odd, upper) and lower 8-bit data (S-odd, lower).

The upper 16 bits of even-numbered data (5-ev
en+upper) and the lower 8 bits of data (S
-even, lower) is the data of the upper 16 bits of odd-numbered data (5
-odd+a'pper) and lower 8 pinto data (S
-odd+io@er) is stored in the R channel audio data storage area.

Thereafter, the same processing as that for recording the analog input signal described above is performed, and a digital audio signal is recorded on the magnetic tape 10.

The recording position of the digital audio data on the magnetic tape 1° is the same as when recording the analog input signal described above, and as shown in FIG. In the first half, the upper 16 bits of even-numbered data (5-even+up
per), and in the second half, the data of the lower 8 bits of even-numbered data (S-even, lower,) and the data of the lower 8 bits of odd-numbered data (S-odd,
lower) is recorded, -azimuth track 23
In the first half of the B PCM signal area 24, the lower 8 bits of even-numbered data (S-even, low
er) and the data of the lower 8 bits of the odd-numbered data (S-odd, lower) are shown in the latter half of the data of the upper 16 bits of the odd-numbered data (5-odd, lower).
upper) is recorded.

During playback, the playback digital audio data stored in the memory circuit 14 is error-detected and corrected by the decoding circuit 12, and the error-corrected 24-bit digital data is given to the digital interface circuit 20, where a predetermined After being converted into the digital audio interface format, the signal is output from the digital signal output terminal 22 to the outside.

In the above embodiment, one word of digital data exceeding 16 bits is divided into upper 16 bits and lower bits, but the number of bits is not limited to this and may be arbitrary.

Furthermore, in the above embodiment, digital audio data is recorded, but since data of up to 32 bits can be recorded, information other than digital audio data,
For example, dither information or the like may be recorded.

Furthermore, in the above embodiment, a DAT that records and reproduces digital data exceeding 16 bits for 1 channel and 2 channels has been described. The playback mode and the high focus (17 bits or more)/1 channel recording/playback mode may be selected for operation.

Further, in the above embodiment, the DAT was explained, but the present invention can be applied to all digital audio equipment such as a professional PCM recorder, a CD recorder/player, an 8I11n PCM recorder, etc., and the quantization It is clear that a recording/reproducing device with a high number of bits can be constructed easily.

〔Effect of the invention〕

As described above, according to the present invention, an input analog audio signal of a predetermined channel is sampled by quantization exceeding 16 bits, and the sampled data is divided into two parts, the upper bit and the lower bit. As well as assigning to the signal recording area for each channel, +azimuth track PC
In the first half of the M signal region, the data of the upper bits of the even-numbered data (S-even, upper) are stored, and in the second half, the data of the lower bits of the even-numbered data (S-ev
The data of the lower bits of the odd-numbered data (S-odd, 1over) are recorded, and the data of the lower bits of the even-numbered data (S-eVen, lower) are recorded in the first half of the PCM signal area of the -azimuth track. ,
lower) and data of the lower bits of odd-numbered data (S-odd).

lower) is the top 16 odd-numbered data in the second half.
Since bit data (5-odd, upper) is recorded and replayed, even if the reproduced signal in the first half or the second half of the PCM signal area is missing, the replay signal from one track is also missing. However, it will be a corrected sound,
It is possible to provide an excellent recording and reproducing device that can reproduce sound without deterioration in S/N and dynamic range.

Furthermore, the encoding circuit that adds test signals for error correction and detection to digital data, the decoding circuit that performs error correction and detection of reproduced digital data, the modulation and demodulation circuits, etc., are the same as conventional ones and can be used without modification. Therefore, the device can be constructed at low cost.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a recording and reproducing apparatus according to an embodiment of the present invention, and FIG. 2 is an explanation showing recording positions of digital audio data on a track pattern recorded by the recording and reproducing bag 1 shown in FIG. Figure 3 is a block diagram of the conventional DAT, and Figure 4 is the conventional DAT shown in Figure 3.
Figure 5 is an explanatory diagram showing the block format of the PCM signal area, and Figure 6 is the digital audio interface format. FIG. 7 is a diagram showing the transmission format when transmitting two-channel signals. 4... Memory circuit, 5... Encoding circuit, 6... Modulation circuit, 7... Recording/reproducing amplifier, 8A, 8B... Rotating head, 9... Rotating drum, 10... magnetic tape, 11... demodulation circuit, 12... decoding circuit, 15...
・Servo circuit, 16... system control circuit,
17... Input key 218... Display unit, 19... Clock generation circuit, 20... Digital interface circuit, 24... PCM signal area, 23A...+azimuth track, 23B... -Azimuth track, 41
...20-bit A/D conversion circuit, 42...20-bit D/A conversion circuit. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Agent Masuo Oiwa Figure 2 I(') Tape running direction 26A: + Azimuth track 23B Knee azimuth track 24: PCM signal area Figure 4 IO Sui-111 Tape running direction Figure 5 Procedure amendment (voluntary) ) April 23, 1991 2. Title of the invention Recording and reproducing device 3. Person making the amendment Relationship to this case Patent applicant address 2-2-3 Marunouchi, Chiyoda-ku, Tokyo Name (601) Mitsubishi Electric Stock Company Representative Moriya Shiki 4, Agent Address 2-2 Marunouchi, Chiyoda-ku, Tokyo
No. 3 Mitsubishi Electric Corporation -m-8, Name (7375) Patent Attorney Masuo Oiwa -,,::1 (=
・' (Contact information 03 (3213) 3421 Permits Department) 5, Column 6 for detailed explanation of the invention in the specification subject to amendment, Contents of amendment (1) Section ``12'' of Table 2 rD4 on page 10 of the specification Correct "bit linear" to "12-bit nonlinear". (2) Page 15, line 20 to page 16, line 7 “It was sampled...
``A recording and reproducing means for performing...'' is deleted and the following is added in the same place. [Divide the sampled data into upper bits and lower bits]
a recording/reproducing means for demodulating and decoding the reproduced digital audio signal by allocating it to a signal recording area for two channels in the DAT, recording it on a recording medium, and demodulating and decoding the reproduced digital audio signal. )Page 19, lines 11-12 ``Storage medium'' is changed to ``Recording medium''
I am corrected. that's all

Claims (1)

[Claims] An analog/digital conversion means for sampling an audio signal of a predetermined channel into a digital audio signal of 16 bits or more; The high-order bit data of the even-numbered digital audio data is recorded in the first half of the PCM signal area of a predetermined track of the recording medium, and the low-order bit data of the even-numbered data and the odd-numbered data are recorded in the second half. The lower bit data is recorded, the lower bit data of the even and odd data is recorded in the first half of the PCM signal recording area of the other track of the recording medium, and the upper bit of the odd data is recorded in the latter half. a recording/reproducing means for recording and reproducing bit data;
A recording and reproducing device comprising digital/analog converting means for converting the digital audio signal reproduced by the recording and reproducing means into an audio signal using a sampling clock signal of 16 bits or more.