JPS6286508A - Recording device for digital information signal - Google Patents

Abstract

PURPOSE:To record the high quality PCM signal by changing the number of rotation of the rotary head to the PCM signal with the different frequency and the number of the bit. CONSTITUTION:Switches 14A and 14B are changed over and at the same time, a switch 45 is changed over. Thus, the PCm output with the different frequency and the number of the bit from an audio signal processing circuit 20 or 30 is selected. Simultaneously, in accordance with the control input from the switch 45 corresponding to the frequency and the number of the bit of the PCM output, a phase servo circuit 42 is controlled and the number of the rotation of rotary heads 1A and 1B is changed. Consequently, the high quality PCM signal having the number of many bits with a high frequency can be also recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a recording device for digital information signals, which is commonly used for recording digital information signals, such as digital audio signals, on a magnetic tape using a rotary head.

[Summary of the invention]

The present invention provides an apparatus for recording digital information signals, such as digital audio signals, on a tape by a pair of magnetic heads attached to a rotating drum, and the rotation of the rotating heads.

An 8-bit digital information signal whose sampling frequency is fs is processed so that it is recorded when the number of rotations is R1, and a sampling frequency is fs2 which is processed so that it is recorded when the number of rotations of the rotary head is R2. It can record both 16-bit digital information No. 13,
Therefore, by switching the rotation speed of the rotating drum to R1 or R2, it is possible to record not only 8-bit but also 16-bit digital information signals without changing the configuration of the disk or tape system. It is.

[Conventional technology]

For example, as shown in Japanese Unexamined Patent Publication No. 58-222402, a VTR (so-called 8W VTR) is known that uses a small tape cassette and has a magnetic tape width of 8 mm. One feature of this VTR is that the recording/playback of digital audio signals (referred to as PCM signals) is standardized.

In the 31m VTR, the product rate method is used to record an audio signal converted to an FM frequency on an inclined track together with a recording video signal. Also, as an option, a dedicated area for PCM signals is provided at the end of the track. Furthermore, standards have also been established for using the 3n+ VTR as a recording/reproducing device exclusively for audio signals.

In 3 mm VTR, the sampling frequency is (f
.

= 2 fH = 31.5 kHz, fH: horizontal synchronization frequency), and the number of quantization bits is standardized to (n = 8) bits. Therefore, the reproducible frequency band is (fs
= 15.75 kHz). Also, since 8 bits of quantization bits is too small, an analog noise removal system and nonlinear quantization that compresses 10 bits of information to 8 bits are used to substantially expand the dynamic range. There is.

As a PCM signal recording/reproducing device, 8 +n VT
The R's superiority over other PCM tape recorders, compact disc playback devices, etc. is that it is a tape cassette that can record video signals for 4 hours when used as an audio signal-only device. It is possible to record/play back for an extremely long time (4 hours = 24 hours), and it is possible to play both video and audio at the same time.

[Problem that the invention seeks to solve]

Even if an analog noise removal system and non-linear quantization are maintained, compared to a PCM signal with 16-bit linear quantization, the Guinami noise reduction, S/N,
The quality of the sound is poor in terms of distortion. Also, 31.5kHz
The sampling frequency of z is lower than the standard sampling frequency of 48 kHz for digital tape recorders using a rotary head, the sampling frequency of 44.1 kHz for compact discs, etc., and is insufficient in terms of the reproducible frequency band.

Accordingly, an object of the present invention is to provide a digital information signal recording device that can record higher quality PCM signals without sacrificing the advantages of a 3-arm VTR.

[Means for solving problems]

This invention is a recorder that can record by switching between an 8-bit PCM signal and a 16-bit PCM signal.
A pair of magnetic heads and a sampling frequency of fs perform error correction encoding and time axis compression on an 8-bit digital information signal so as to be in sliding contact with a magnetic tape wound in an angular section of α). a first signal processing circuit for recording in an angular section α of the tape; a second signal processing circuit for error correction encoding and time axis compression of a 16-bit digital information signal with a sampling frequency of fs2; a circuit that switches the output signals of the first signal processing circuit and the second signal processing circuit and supplies them to the pair of magnetic heads; 1. A digital information signal recording device characterized by comprising a circuit for switching to a digital information signal.

[Effect]

In this invention, a digital information signal (PCM multiplied signal) having an 8-bit sampling frequency fs and a rotation speed R is processed by error correction encoding and time axis compression.
The information is recorded on the magnetic tape by a pair of rotating heads.

On the other hand, a 16-bit PCM signal with a sampling frequency fs2 that has been processed so as to be recorded by a pair of rotary heads with a rotation speed of R2 cannot be directly recorded by a pair of rotary heads with a rotation speed of R1.

In this invention, the rotation speed is changed from R1 to R2, and 16
Bit PCM signals can be recorded, and signal processing such as error correction code encoding and time axis compression processing can be performed in a manner similar to that of, for example, a digital tape recorder.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. This description follows the order of the items below.

a. Overall configuration of the recording/reproducing circuit, head and tape system, and track pattern C. Error correction code d. Data structure of the digital tape recorder e. Error correction code of the digital tape recorder ", 16-bit P
CM Signal Recording/Reproduction g, Modification Example A, Overall Configuration of Recording/Reproduction Circuit FIG. A pair of rotating heads are shown spaced at an angular spacing of 180° on a rotating drum. This rotating head LA, I
A recording signal is supplied to the rotary head LA via amplifiers 11A and 11B and a rotary transformer (not shown).

The signal reproduced from IB is sent to the rotating transformer and amplifier II.
A, taken out via IIB. The drum to which the rotating rads IA and IB are attached is rotated by a drum motor 13.

Each of amplifiers IIA and IIB is composed of a recording amplifier and a reciprocating amplifier. Control pulses for controlling the operation and non-operation of this amplifier 11A are supplied to respective terminals 12A and 12.
A recording operation is performed only at a predetermined timing. This control pulse is formed based on an RF switching pulse that is synchronized with the rotational phase of the rotating healds IA and IB.

The timing of the control pulse is a predetermined timing depending on the recording mode. The recording mode is 81.
Recording mode for IVTR (recording only FM modulated audio signal, recording with added PCM signal, recording in multi-channel format) and recording of 16-bit PCM signal for digital tape recorder (recording of track A or trunk B) There is.

Switch circuits 14A and 14 are connected to amplifiers 11A and IIB.
B are connected respectively. The switch circuits 14A and 14B are switched depending on whether the PCM signal to be recorded is 8 bits or 16 bits. The sampling frequency is 2fH (fo
When recording/reproducing a PCM signal with 8 bits (horizontal synchronization frequency = 15.75 kHz), that is, a PCM signal according to the 8 ml VTR standard, both switch circuits 14A and 14B select side a. . On the other hand,
The sampling frequency is 43.2kHz and the number of bits is 1.
When recording/reproducing a 6-bit PCM signal, both switch circuits 14A and 14B select the b side.

On the a side of the switch circuits 14A and 14B, 8 mm V
A switch circuit 15 constituting the signal processing circuit of TR is connected. This switch circuit 15 is for switching between a video signal and an audio signal, and when recording/reproducing a video signal, the V side is selected, and when recording/reproducing an audio signal, the A side is selected. switch circuit 1
1, a video signal processing circuit 16 is connected to the V side of 5;
An audio signal processing circuit 20 is connected to the A side of the switch circuit 15. Switch circuit 15 is controlled by a control pulse from terminal 12C.

The video signal processing circuit 16 converts the color video signal from the input terminal 17 into a recording signal, and also converts the reproduced signal back into a color video signal and outputs it to the output terminal 18. The luminance signal in the color video signal is FM modulated and the carrier color signal is converted to a signal at a lower carrier frequency.

The audio signal processing circuit 20 encodes the 8-bit PCM signal from the A/D converter 24 with an error correction code during recording, and performs time axis compression processing so that it can be recorded in the PCM signal recording area. In addition, it performs phase modulation. The A/D converter 24 has 8
Performs nonlinear quantization of bits. In addition, input terminal 2
1 is supplied to an A/D converter 24 via a low-pass filter 22 and an analog noise removal circuit 23.

During reproduction, the reproduced PCM signal is supplied to the audio signal processing circuit 20. Audio signal processing circuit 20
Now, demodulation of biphase modulation.

Processes of time axis expansion, error detection/correction, and correction of uncorrectable errors are performed. The output data of the audio signal processing circuit 20 is converted into an analog signal by the D/A converter 25, and the output data is converted to an analog signal by the D/A converter 25,
A reproduced audio signal is taken out to an output terminal 27 via 6.

An audio signal processing circuit 3o that conforms to the standard format of a rotary head type digital tape recorder is connected to the b side of the switch circuits 14A and 14B. Input terminal 31
The audio signal is supplied to an A/D converter 33 via a low-pass filter 32. The A/D converter 33 performs 16-bit linear quantization at a sampling frequency of 43.2 kHz.

During recording, the audio signal processing circuit 30 divides the 16-bit sample data into upper 8 bits and lower 8 bits, and converts each 8-bit unit into an error correction code that conforms to the digital tape recorder standard. 9 Performs time axis compression and (8 bits = 10 bits) modulation processing.

During playback, the audio signal processing circuit 30 performs demodulation and time axis expansion of (8 bits→10 bits) modulation, error detection/correction, and correction of uncorrectable errors.

The output data of the audio signal processing circuit 30 is converted into an analog signal by the D/A converter 34, and is outputted to the output terminal 3G via the low-pass filter 35.

The video signal processing circuit 16 performs FM modulation of the audio signal and mixes it with the recorded video signal, as well as separation of the FM modulated audio signal from the reproduced signal and FM demodulation. Further, the video signal processing circuit 16 also performs processing for adding and separating signals for the automatic tracking system 411 (ATF).

A rotation detector 40 that magnetically detects the rotation of the drum motor 13 is provided. The output signal of this rotation detector 40 is supplied to a speed servo circuit 41 and a phase servo circuit 42 of the drum motor 13.

An RF switching pulse is formed from the output signal of this rotation detector 40. The speed servo circuit 41 controls the rotation speed of the drum motor 40 so that the period of the output signal of the rotation detector 40 is specified. A reference voltage for determining this reference rotational speed is supplied to the speed servo circuit 41 via the switch circuit 43.

The switch circuit 43 switches in conjunction with the switch circuits 14A and 14B, and switches between 8 pins in the case of an 8 mm VTR.
When recording a PCM signal, the reference voltage on the terminal a side is selected and the drum motor 13 is controlled to rotate at a rotation speed of 180 rpm. When recording a 16-bit PCM signal according to the digital tape recorder standard, the terminal side is selected and the drum motor 13 is controlled to rotate at a rotation speed of 200 rpm.

A servo reference signal selected by a switch circuit 45 is supplied to the phase servo circuit 42 . switch times 845
is switched in conjunction with the switch circuits 14A and 14B, similar to the switch circuit 44, and when recording an 8-bit PCM signal for an 8mm VTR, the phase reference signal on the terminal a side is selected, and the phase reference signal of the digital tape recorder standard is selected. When recording a 16-bit PCM signal, the phase reference signal on the terminal side is selected. Terminal 4 connected to terminal a
6 is supplied with a field frequency phase reference signal;
A phase reference signal of a segment frequency is supplied to a terminal 47 connected to the terminal side.

b. Head, tape system and track pattern Figure 2 is as follows:
The arrangement relationship of the head and tape system in this embodiment is shown.

In Figure 2, 2 is the frame frequency (1 in the case of the NTSC system) when recording a standard signal of an 8mm VTR.
The drum 2 is shown rotating at 80 Orpm) and 200 Orpm when recording signals of the digital tape recorder standard, with rotating heads IA and IB attached to the drum 2 with an angular spacing of 180°. The extending directions of the magnetic gaps of the rotary heads IA and IB are different from each other, and the configuration is such that the cocoon talk from adjacent tracks can be suppressed by azimuth loss. A magnetic tape 3 having a width of 8 mm is wound diagonally around the circumferential surface of a drum 2 and runs at a constant speed. The winding angle θ (=θ1 - θ2) of the magnetic tape 3 is, for example, 221° (=
185° + 36°). The magnetic tape 3 is wound within an angle θ, with the range θ1 being the video area, and the range θ2 where the scans of the rotary heads IA and IB overlap being the PCM area.

As shown in FIG. 3, the magnetic tape 3 has a rotary head I.
A and IB form alternating slanted trunks. A PCMjJI area 4A is formed at the starting end where the rotary head IA starts scanning the magnetic tape 3, and then a video area 5A is formed. Similarly, by rotating head IB, P
A CM RM area 4B and a video area 5B are formed. The windings in the video areas 5A and 5B include signals (FM modulated luminance signal, FM modulated audio signal) in the area corresponding to the angle 180°.

ATF viroft signal) is recorded. PCM area 4
The output signal of the audio signal processing circuit 20 is recorded in A and 4B.

Therefore, the switch circuit 15 in FIG.
Select the A side during the scanning period of A and 4B, and select the video area 5.
Control is performed to select the V side during the period of scanning A and 5B. The RF switching pulse is applied to the PCM areas 4A, 4
B and video area 5A.

This signal has a rising edge or a falling edge at the timing of the boundary with 5B.

The 3m VTR is designed to record/reproduce only PCM signals. In this multi-channel format, one trunk is divided into six, as shown in FIG. In the 221° wrapping, the 216° section is divided into 36° sections, excluding the 5° section at the end. These six sections are divided into channels 1, 2, and 3 in order in the head scanning direction. Channel 2. . . . is called channel 6. One section consists of a data section 6 sandwiched between a run-in section 7 at the beginning and an after-record margin 8 at the end, as shown in an enlarged view of the channel 1 section in FIG. It has a configuration where it is located. R at the boundary between channel 1 section and the next channel 2 section
A transition of the F switching pulse occurs. P
When recording/reproducing only CM signals, the switch circuit I5 selects the A side only in the designated channel section.

C. In the error correction code audio signal processing circuit 20, P for one field is
Encoding processing and decoding processing of error correction codes are performed in units of CM signals, that is, data recorded in the PCM areas 4A and 4B. Figure 5 shows a two-dimensional array of data, in which each horizontal row contains malletizers Q, WO, W.
l, W2. W3, P, W4. W5. W6. It is expressed as W7.

Each row contains 132 pieces of data.

Therefore, each piece of 8-bit data is arranged in a (10×132) matrix. This data includes a stereo PCM signal for one field and six pieces of data for control.

In the data array described above, each column in the vertical direction is called a column. In FIG. 5, nine pieces of data indicated by black dots form one parity code sequence containing parity data P, and ten pieces of data indicated by white dots form the other parity code series containing parity data P and Q. A parity code sequence is formed. One parity code sequence containing parity data P is formed from data contained in blocks 15 or 14 blocks apart. The other parity code sequence including parity data P and Q is formed from data contained in blocks equally spaced apart by 12 blocks. Each data in one two-dimensional array is included in two different parity code sequences.

Furthermore, a 16-bit CRC code (a type of error detection code using a cyclic code) is added to each block consisting of (Q, WO, . . . W6.W?). The presence or absence of errors in each block is detected using this CRC code. Since simple parity is used, if there is one data item in one code sequence that is determined to have an error by a CRC check, the error can be corrected. At the time of decoding, error correction ability is improved by repeatedly performing decoding for a code sequence including parity data P and decoding for a code sequence including parity data P and Q.

The data that has been encoded with the error correction code is recorded in order from the first block to the 132nd block. A synchronization code for block synchronization and an address code indicating the block address are added to the beginning of each block. Error data that cannot be corrected by the error correction code described above is replaced by the average value of the correct data located before and after it.

In addition, the above-mentioned error correction code is used together with the video signal.
When recording/playing M signals, record/play only PCM signals.
Applies to both when playing.

d. Data structure of digital tape recorder A rotary head type digital tape recorder records data using a pair of rotary heads attached to a drum with an angular spacing of 180'. The magnetic gaps of the pair of rotary heads extend in different directions. The drum has a diameter of 3
0mm and is rotated at 200Orpm. The magnetic tape is wrapped diagonally at the corner to wrap 90" around the circumference of the drum. The magnetic tape is 8.15 (Ryu/5ec)
), and a pair of rotating heads alternately come into sliding contact with the magnetic tape. An inclined track is formed on the magnetic tape by each of the pair of rotating heads.

The entire data recorded on one track is called one segment. FIG. 6A shows the structure of the data of the l segment recorded by do in one rotation. When the unit amount of recording data is one block, one segment includes 196 blocks of data. A margin (
11 blocks) are provided. Subcodes (11 blocks) are recorded adjacent to each of these margins.

These two subcodes are the same data and are recorded twice. Is the subcode a system for determining time code, sampling frequency, etc.? IIl Sei 91
It is. Of the 11 blocks of the subcode, 8 blocks are the recording area for subcode data, and the PLL is on both sides.
A run-in section (2 blocks) and a post-ampule section (1 block) are arranged.

Furthermore, the shaded section indicates an inter block gear in which no data is recorded, and is sandwiched between three inter block gaps, and a pilot signal for ATF is recorded over five blocks. 1
A PCM signal subjected to recording processing is recorded in a 128 block long area excluding the 2 block PLL run-in section within a 130 block long area at the center of the segment. This PCM signal is data corresponding to the audio signal of the rotation time of the rotary head.

This PCM signal consists of a two-channel stereo PCM signal consisting of an L (left) channel and an R (right) channel and parity data of an error detection/correction code. 6th
In one segment shown in FIG. A, data Le is recorded in the left half of the PCM signal recording area, and data RO is recorded in the right half. Data Le consists of even-numbered data on the L channel and parity data regarding this data, and data RO consists of odd-numbered data on the R channel and parity data regarding this data.

Figure 6B on the trunk formed by the other rotating head.
1 with the same configuration as one of the tracks mentioned above, as shown in
Segment data is recorded.

In the data section of one segment of data on the other track, data Re is recorded in the left half and data LO is recorded in the right half at step 6l8. The data Re consists of even-numbered data of the R channel and parity data regarding this data. Data Lo consists of odd-numbered data of the L channel and parity data regarding this data. In this way, even-numbered data and odd-numbered data of each channel are recorded separately on two adjacent trunks, and
The reason why L channel and R channel data are recorded on the same track is to prevent errors in successive data on the same channel due to dropouts or the like.

FIG. 6C shows the data structure of one block of the PCM signal and subcode. An 8-bit (1 symbol) block synchronization signal is added to the beginning of one block, and then an 8-bit ID signal is added.

A block address is added next to the ID signal.

Simple parity error correction encoding processing is performed on the two symbols of the ID signal and block address,
An 8-bit parity is added next to the ID signal. The MSB of the block address is "1" for a subcode block and "0" for a PCM data block.

The I block contains 256 bits (32 symbols) of data.

e. Error correction code of digital tape recorder An error detection/correction code is processed for each 128 block of data recorded in the l segment. Figure 7A is
The code structure of the data recorded in the l segment shown in FIG. 6 is shown, and FIG. 7B shows the code structure of the data recorded in the l segment shown in FIG. 6B. A PCM signal with a quantization bit count of 16 bits is divided into upper 8 bits and lower 8 bits, and an error detection/correction code is encoded using 8 bits as one symbol.

Data of (1-28×32=4096 symbols) is recorded in the l segment. As shown in Figure 7A, (
Error detection code C1 and error in each of the vertical and horizontal directions of a two-dimensional array of data consisting of even-numbered data of the L channel consisting of 3Qx52-1560) symbols and odd-numbered data of the same number of R channels. The correction code C2 is encoded. vertical 30
The symbols are encoded with a C1 code using a (32,28,5) Reed-Solomon code.

This C1 code parity data P is arranged at the last position of the two-block set in the two-dimensional array. Also, the horizontal 5
Two symbols are encoded with a C2 code using a (32, 26, 7) Reed-Solomon code. This C2? The I code is applied to every 26 symbols of the 52 symbols, and parity data Q consisting of 6 symbols is generated for one code sequence. Parity data Q consisting of a total of 12 symbols of C2 code is arranged at the center of the two-dimensional array. The other 5 located horizontally
Similar 02 code encoding is performed on the two PCM data symbols, and their parity data Q is placed in the center.

The code configuration shown in FIG. 7B replaces the even-numbered PCM signals of the L channel with the even-numbered PCM signals of the R channel in the code configuration of FIG. 7A, and replaces the odd-numbered PCM signals of the R channel. This is a code configuration replaced by an odd-numbered PCM signal of the L channel.

For 32 symbols arranged vertically in these code configurations, as shown in FIG. 6C, a block synchronization signal,
One PCM data block is configured by adding an ID signal, block address, and parity. The subcode block also has the same data structure as shown in FIG. 6C.

f. Recording/playback of 16-bit PCM signal Recording/playback of a 16-bit PCM signal, which has undergone signal processing similar to that of the digital tape recorder described above, is performed by the head and tape system shown in Figure 2. .

In other words, as shown in FIG. 8, the magnetic tape 3 has 1800 windings within the corner, which correspond to the video area, and the corner is divided into two equal parts of 90" each. As shown in FIG. 9, a track 9 (referred to as trunk A) and a track 10 (referred to as track B) relating to the 16-bit PcM signal are formed in correspondence with each other. The data structure of the digital tape recorder shown in FIG. 6A and FIG. 6B is installed in each of the track A and trunk B.
Segment data is recorded.

When recording a 16-bit PcM signal, switch circuits 44 and 45 (see FIG. 1) select side b. Therefore, the rotational speed and rotational phase of the drum motor are controlled so that the drum motor 13 rotates at 2000 rpm and one segment of data is recorded as track A or trunk B. I[l is done.

The trunk pattern shown in FIG. 9 corresponds to the case where both tracks A and B are formed while the magnetic tape 3 is running in the forward direction shown by the arrow. However, the track A may be formed in the forward direction, and the track B may be formed in the reverse direction, which is the opposite direction to the forward direction. In addition, both the PCM area 4 defined by 8W VTR and the recording area (track A and track B) for 16-viso 1-PCM signals can coexist.

g. Modification This invention is based on CCIR method 2 - 3 Tsuru V in which the rotation speed is set to 150 Orpm in order to record a video signal.
It can also be applied when using TR.

The present invention can also be applied when a PCM signal is input, and can also be applied when recording digital information signals other than digital audio signals.

〔Effect of the invention〕

According to this invention, the sampling frequency is 43°2kHz.
z, a 16-bin linear quantized PCM signal can be recorded. Therefore, compared to recording an 8-bit PCM signal, the dynamic range, frequency characteristics,
It is possible to record/reproduce high-quality audio signals with good S/N, distortion rate, etc. This invention is 8m+V
It is possible to selectively record either an 8-bit PCM signal according to the TR standard or a 16-bit PCM signal according to the digital tape recorder standard. It is more useful than a recorder.

In addition, the same signal processing as that of a digital tape recorder can be performed, and there is an advantage that there is no need to develop a new error correction code system or design a signal processing circuit.

Furthermore, in the case of a 3-mar VTR, round-trip recording is possible, and recording/playback can be performed for a longer recording time than a digital tape recorder, up to 8 hours (round-trip).

[Brief explanation of drawings]

Fig. 1 is an overall block diagram of a recording/reproducing circuit according to an embodiment of the present invention, Fig. 2 is a route diagram showing the configuration of the head and tape system, and Figs. 3 and 4 are video signal and 8-bit A route map showing track patterns for recording audio PCM signals and track patterns for recording only audio PCM signals, Figure 5 is a route map for explaining error correction codes, and Figure 6 is a route map for digital tape. A route map showing the structure of recorder data; Figure 7 is a route map used to explain the error correction code of a digital tape recorder; Figures 8 and 9 are route maps used to explain when recording a 16-bit PCM signal. It is a diagram. Explanation of main symbols in the drawings IA, IB: rotating head, 3: 6 air tape, 4A
, 4B: PCM area, 5A, 5B: Video area,
6: Data section, 9, 10: I-rack A and truck
/riB, IIA, IIB: amplifier, 13 Ni drum motor, 16: video signal processing circuit, 20: audio signal processing circuit regarding 8-bit PCM signal, 3
0: Audio signal processing circuit for 16-bit PcM signal, 40: Rotation detector, 41: Speed servo circuit.

Claims (1)

[Claims] A pair of magnetic heads rotating at a rotation speed R1 so as to be in sliding contact with a magnetic tape wound in an angle section of (180°+α), and an 8-bit digital information signal with a sampling frequency fs_1. a first signal processing circuit for error-correction encoding and time-base compression and recording at least in the section of the angle α of the magnetic tape;
At s_2, a second signal processing circuit performs error correction encoding and time-base compression of a 16-bit digital information signal, and the output signals of the first signal processing circuit and the second signal processing circuit are switched to generate the pair of signals. When recording the output signal of the first signal processing circuit, the rotation speed of the pair of magnetic heads is set to R1, and when recording the output signal of the second signal processing circuit, the rotation speed of the pair of magnetic heads is set to R1. 1. A recording device for a digital information signal, comprising means for switching the number of rotations of a head to R2.