JPH05151505A - Audio signal recording system - Google Patents

Abstract

PURPOSE:To scramble an analog audio signal without deteriorating its reproducibility to be recorded in privacy. CONSTITUTION:A signal of one block BK is recorded at every 600msec. Each block is composed of a header part HD and a segment part SG. A password code and a key code are arranged in the header part. An audio signal of 600msec is divided by 12 periods, each having 50msec, and they are permuted in accordance with the key code to carry out the scrambling processing, and also the audio signal of each period is processed of time axis compression to 37.5msec and arranged in turn. Since the analog audio signal is recorded after scrambling processing, the recorded contents can be kept in privacy. At the time of reproducing, the key code is detected from the header part, and based on this key code, the audio signal of the segment part can be descrambled, and hence the original audio signal can easily be reproduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording system for scrambling an analog audio signal on a magnetic tape for recording.

[0002]

2. Description of the Related Art It is well known in the past to record an analog audio signal on a magnetic tape using a tape recorder.

[0003]

When the analog audio signal is recorded on the magnetic tape as described above, it may be desired to provide confidentiality depending on the recorded contents. In order to provide confidentiality, it is possible to scramble an analog audio signal, for example.

When the analog audio signal is scrambled, the scramble information is required to reproduce the original analog audio signal, but there is a problem in which position the scramble information should be inserted.

The present invention provides a recording method for providing confidentiality by scrambling and recording without impairing the reproducibility of analog audio signals.

[0006]

SUMMARY OF THE INVENTION According to the present invention, a block comprising a header section having a key code and a segment section having an audio signal for a predetermined period scrambled by a scrambling pattern corresponding to the key code is recorded on a recording medium. It is to record continuously.

[0007]

The reproduced audio signal from the recording medium remains scrambled, and descramble processing is required to reproduce the original audio signal. The original audio signal can be easily reproduced by detecting the key code from the header part of each block and descrambling the audio signal of the segment part with a descrambling pattern according to the key code.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In this example, an audio signal is scrambled on a magnetic tape and recorded and reproduced.

First, the format of the recording signal will be described with reference to FIGS.

As shown in FIG. 6A, one block of signal is arranged every 600 msec. Each block is 119.
It is composed of a header part of 5 msec and a segment part of 480.5 msec (illustrated in FIG. 6B).

FIG. 7 shows the format of the header section. 12.5K in the first 10msec area of the header
A burst signal of Hz is arranged, a silent region of 9 msec is provided after that, and a 24-bit secret code and a 16-bit key code are arranged in a region of 100.5 msec thereafter (illustrated in FIG. 7A).

In the first and last 0.5 msec regions of the 100.5 msec period, 12.5K is used for signal separation.
A burst signal of Hz is arranged, and a bit signal is arranged between these burst signals (illustrated in FIG. 7B). An area of 2 msec is provided for distributing each bit signal, and a silent area of 0.5 msec is provided between the areas.

The bit signal is constructed as shown in FIG. 7C. That is, an 8 KHz signal is inserted for 8 cycles to become a data "0" signal, while 16 cycles are inserted for a data "1" signal. FIG. 7C is an example when the personal identification code is “011 ...”.

FIG. 8 shows the format of the segment part. 0.5mse at the beginning and end of the segment
Burst signals of 12.5 KHz are arranged for signal separation in the region of c (shown in FIG. 8B), and audio signals of 600 msec are arranged between these burst signals.

Five audio signals for 600 msec each
It is divided into 12 periods of 0 msec, rearranged by a scramble pattern corresponding to the key code arranged in the header part, and then sequentially arranged in areas # 1 to # 12 (shown in FIG. 8A).

1 mse is provided at each end of each of the areas # 1 to # 12.
A margin portion of c is provided, and a burst signal of 12.5 KHz is arranged for signal separation in an area of 0.5 msec between the margin portions of one area and another area (FIG. 8).
(Shown in B).

By the way, the areas # 1 to # 12 are 37.5.
Since there is only msec and an audio signal for 50 msec cannot be placed as it is, the audio signal is placed after time axis compression processing as follows.

That is, the analog audio signal is 24
Converted to a digital signal with a sampling frequency of KHz and written to the memory,
It is read with a clock of 2 KHz. As a result, the audio signal for each 50 msec is 37.5 ms.
ec is compressed on the time axis and can be arranged in the areas # 1 to # 12 (37.5 msec period).

Signals at both ends of the audio signal arranged in each area are arranged in an extended manner in the margins of 1 msec period provided at both ends of each area of # 1 to # 12.

The rearrangement processing by the scramble pattern and the formation of the signal arranged in the margin portion are executed by controlling the read address of the memory in the above-mentioned time base compression processing, for example.

Signals recorded in the rearrangement process and the margin portion will be further described with reference to FIG.

For example, as shown in FIG. 9A, when the audio signal is divided into 50 msec each, each 50 msec
As shown in FIG. 9B, the signal arranged in the overlap portion with respect to the audio signal for sec is formed by extending the signals at both ends. The original audio signal is DATA1,
When DATA2, DATA3, and DATA4 are in this order (shown in FIG. 9A), the scrambling pattern DA
When TA3, DATA1, DATA4, and DATA2 are rearranged in this order, a recording signal is formed as shown in FIG. 9C.

FIG. 10 shows the frequency spectrum of the recording signal. As described above, since the audio signal is recorded after the time axis compression processing, when the original audio signal band is limited to 9 MHz or less (shown by the broken line), the actually recorded audio signal band is limited to 12 MHz or less. (Solid line is shown). As a result, it is possible to prevent the audio signal and the burst signal of 12.5 KHz from being recorded without being mixed with each other, and prevent the header section from being erroneously detected by detecting the signal of 12.5 KHz from the audio signal during reproduction.

In the present example, the recording signal of the above format is recorded on the magnetic tape and reproduced from the magnetic tape.

FIG. 1 shows an example of a recording / reproducing apparatus for recording / reproducing an audio signal on a magnetic tape in the recording signal format as described above.

In the figure, the analog audio signal SA1 supplied to the audio-in terminal 1 is supplied to the fixed terminal on the side a of the switch circuit 2. A reproduction signal SA2 output to the audio-out terminal 3b of the cassette deck 3 using, for example, a compact audio cassette tape is supplied to the fixed terminal on the b side of the switch circuit 2. The switching of the switch circuit 2 is controlled by the CPU 4, and is connected to the side a during recording and to the side b during reproduction.

The output signal of the switch circuit 2 is band-limited by the low-pass filter 5 and then supplied to the A / D converter 6.
For example, one sample is converted into 16-bit digital audio data.

Reference numeral 7 is a sequence generator. The sequence generator 7 is supplied with a control signal from the CPU 4 to control its operation. A clock CK1 is supplied from the sequence generator 7 to the A / D converter 6 described above, and sampling is performed in synchronization with the clock CK1. The frequency of the clock CK1 is set to 24 KHz during recording and 32 KHz during reproduction.

The digital audio data output from the A / D converter 6 is transferred to the RAM via the data buffer 8.
9 is supplied as write data. In this case, RA is generated from the sequence generator 7 via the address buffer 10.
An address signal is supplied to M9, and audio data is written to a predetermined address of RAM9.

The audio data output from the A / D converter 6 is sequentially written into the RAM 9 during recording, but during reproduction, the audio signals arranged in the areas # 1 to # 12 of the segment portion of each block are digitally converted. Only the audio data is written in the RAM 9.

The reproduction signal SA2 output to the audio-out terminal 3b of the cassette deck 3 is supplied to the bit burst detection circuit 11. In the detection circuit 11, 1
8K with burst signal of 2.5KHz detected
A bit signal (a secret code and a key code) is detected based on the number of cycles of the Hz signal, and the detected signal is supplied to the sequence generator 7.

At the time of reproduction, the 12.5 KHz burst signal arranged at the beginning of the header portion of each block is detected from the reproduction signal SA2 output to the audio-out terminal 3b of the cassette deck 3 to detect the header of each block. Parts are detected. In addition, 12.5 placed in the segment part
When the KHz burst signal is detected, # 1 to # 1
Region 2 is detected. Based on this, as described above, only the audio data obtained by digitally converting the audio signals arranged in the areas # 1 to # 12 is controlled to be written in the RAM 9.

Further, the audio data written in the RAM 9 is read at a clock of 32 KHz at the time of recording and compressed on the time axis, and at the time of reproduction it is 24 K.
The data is read out with the clock of Hz and expanded on the time axis. In this case, at the time of recording, reading is performed at a timing corresponding to the areas # 1 to # 12 (including the margin portion) of the recording signal format.

At this time, at the time of recording, the scramble pattern corresponding to the key code randomly generated by the CPU 4 and supplied to the sequence generator 7 is set to 60.
Each 50 mse that composes 0 msec audio signal
The audio data corresponding to the audio signal for 12 periods of c minutes is rearranged, and thus the scramble process is performed, and the data at both ends of each 50 msec audio data is continuously extended by 1 msec and the data of the margin portion is read. It is formed.

On the other hand, during reproduction, the reproduction signal SA2
With the descramble pattern corresponding to the key code detected by the detection circuit 11, the audio data in the areas # 1 to # 12 are rearranged, and thus the descramble process is performed.

The rearrangement of the audio data and the formation of the data in the margin portion are performed by controlling the address signal supplied from the sequence generator 7 to the RAM 9.

The audio data read from the RAM 9 is supplied to the D / A converter 12 via the data buffer 8. The clock CK2 is supplied from the sequence generator 7 to the D / A converter 12. The frequency of the clock CK2 is 32 KHz during recording and 24 K during playback.
It is set to Hz.

The analog audio signal output from the D / A converter 12 is band-limited by the low-pass filter 13 and then supplied to the movable terminal of the switch circuit 14. The switching of the switch circuit 14 is controlled by the CPU 4,
It is connected to the side a during recording and to the side b during reproduction. The fixed terminal on the b side of the switch circuit 14 is connected to the audio-out terminal 15.

At the time of recording, which is not described above, the personal identification code supplied to the CPU 4 by the user's operation of the keyboard 17 is supplied to the sequence generator 7 together with the key code. Then, the sequence generator 7 supplies the bit burst generation circuit 16 with data indicating the timing of generating a burst signal of 12.5 KHz and the timing of generating a signal of 8 KHz indicating a bit signal (password code and key code).

The burst signal and the bit signal output from the generating circuit 16 are supplied to the synthesizing circuit 18 and synthesized with the audio signal obtained at the fixed terminal on the a side of the switch circuit 14. The output signal of the synthesis circuit 18 is supplied to the audio-in terminal 3a of the cassette deck 3.

In the above configuration, the operation during recording will be described first.

Since the switch circuit 2 is connected to the side a during recording, the analog audio signal SA1 supplied to the terminal 1 is supplied to the A / D converter 6 and converted into digital audio data with a sampling clock of 24 KHz. And sequentially written in the RAM 9.

Then, the audio data written in the RAM 9 is read at a 32 KHz clock corresponding to the areas # 1 to # 12 (including the margin portion) of the recording signal format and time-axis compressed. At this time, 600
Each 50 mse that composes audio data for msec
The audio data for 12 periods of c minutes is rearranged in a scramble pattern according to a key code randomly generated by the CPU 4 and scrambled. At this time, the data at both ends of the audio data for 12 periods of 50 msec each is extended and read for 1 msec, and the data of the margin portion is formed.

The audio data read from the RAM 9 is supplied to the D / A converter 12 and converted into an analog audio signal. Since the switch circuit 14 is connected to the side a during recording, the synthesizing circuit 18 synthesizes the analog audio signal output from the D / A converter 12 with the burst signal and bit signal output from the generating circuit 16.

The combining circuit 18 outputs a signal SA3 in accordance with the above-mentioned recording signal format, and this signal S
A3 is supplied to the audio-in terminal 3a of the cassette deck 3 and recorded on the magnetic tape.

Next, the operation during reproduction will be described.

Since the switch circuit 2 is connected to the b side during reproduction, the reproduction signal SA2 output to the terminal 3b of the cassette deck 3 is supplied to the A / D converter 6 and 32K.
Converted to digital data with a sampling clock of Hz. Then, only the audio data corresponding to the areas # 1 to # 12 are sequentially written in the RAM 9.

Then, # 1 to # written in the RAM 9
The audio data in the 12 areas is read at a clock of 24 KHz and expanded on the time axis. At this time, # 1
The # 12 audio data is rearranged in the descramble pattern according to the key code detected by the detection circuit 11 from the reproduction signal SA2 and descrambled.

The audio data read from the RAM 9 is supplied to the D / A converter 12 and converted into an analog audio signal. Since the switch circuit 14 is connected to the b side during reproduction, the analog audio signal SA4 output from the D / A converter 12 is output to the terminal 15.

Although not described above, in the example of FIG. 1, the user needs to operate the keyboard 17 and input the personal identification code even during reproduction. The descrambling process is started only when the same code as the code input at the time of reproduction is continuously detected twice from the reproduction signal SA2. After that, the PIN codes detected in three consecutive blocks are compared, and if at least two PIN codes match, the descrambling process is continued. In this judgment of the personal identification code, the personal identification code detected by the detection circuit 11 is supplied to the CPU 4 via the sequence generator 7, and the CPU 4
Judged by

A specific example of the identification code identification will be described with reference to FIG. The secret code shown is a secret code detected by the detection circuit 11 from the header of each block.
It is displayed in hexadecimal system. As described above, the personal identification code is a 24-bit code, but each 4 bits indicates each digit of hexadecimal system.

In the figure, the secret code is "25252.
5 ”to start reproduction from the point P, No. Four
If the security code is detected from the block of N, it means that the correct security code has been detected twice in succession.
o. The descrambling process is started from block 4.

No. An incorrect secret code is detected from the block No. 6 but two blocks (No. 4, No. 4).
Since the secret code of 5) is correct, the descrambling process is continued.

No. When the personal identification code is detected from the block of No. 8, the personal identification code of the two blocks (No. 6 and No. 8) is incorrect. The descrambling process is stopped from block 8. However, no. If the security code is detected from the 9th block, 2 blocks (N
o. 7, No. No. 9) because the security code is correct.
The descrambling process is restarted from block 9.

For the same reason, No. From the block of No. 13, the descrambling process is stopped, and No. 17
The descramble processing is restarted from the block.

Although not described above, the reproduction signal SA2 is reproduced at the time of reproduction.
When the same key code is detected twice in succession,
The descrambling process is started with the descrambling pattern according to the key code. After that, the key codes detected in three consecutive blocks are compared, and if at least two key codes match, the descrambling process is continued with the descrambling pattern according to the key code.

In the determination of this key code, the key code detected by the detection circuit 11 is C through the sequence generator 7.
It is supplied to the PU 4 and judged by the CPU 4. It should be noted that the determination of the key code is performed after the descramble processing is enabled by the above-described determination of the secret code.

A specific example of determining the key code will be described with reference to FIG. The key code shown in the figure is a key code detected by the detection circuit 11 from the header of each block.
It is displayed in hexadecimal system. As described above, the key code is a 16-bit code, but each 4 bits represents each hexadecimal digit.

In FIG. 3A, Q1 is determined by the identification code.
It is assumed that the descrambling process has become possible at the time. No. When the key code is detected from the block of No. 2, it means that the same key code is detected twice consecutively. Key code “FFF” from block 2
The descramble processing is started with the descramble pattern corresponding to "F".

No. The key code of "8888" is detected from the block of No. 4, but two blocks (No. 2, N
o. Since the key code of 3) is "FFFF", the descramble processing is continued with the descramble pattern according to the key code "FFFF".

No. When the key code is detected from the block of No. 6, the key code of 2 blocks (No. 4, No. 6) becomes “8888”, and thus No. The descramble processing is performed from the block 6 in the descramble pattern corresponding to the key code "8888".

It is assumed that the descrambling process becomes possible at the time point Q3 after the descrambling process is stopped at the time point Q2 in the judgment of the personal identification code. No. When the key code is detected from the block of 13, the same key code is
This means that it was detected consecutively, and this No. The descrambling process is restarted from the block 13 with the descrambling pattern according to the key code "0000".

Further, in FIG. 3B, it is assumed that the descrambling process becomes possible at the time of Q4 in the judgment of the secret code. No. When the key code is detected from the block of No. 4, it means that the same key code is detected twice consecutively. Key code "FF" from block 4
The descramble processing is started with the descramble pattern according to "FF".

Next, the operation of the CPU 4 will be described with reference to FIGS.
This will be described using the flowchart of.

When the power is turned on, first, initialization is performed (step 31). Next, it is judged whether or not the personal identification code is input from the keyboard 17 (step 3
2) When the personal identification code is input, the personal identification code is set in the register (step 33).

Next, it is judged whether or not the reproduction key is turned on (step 34), and if not, it is judged whether or not the recording key is turned on (step 35). If the recording key is not turned on in step 35, the process returns to step 34.

When the record key is turned on in step 35, a key code randomly generated by the CPU 4 is set in the register (step 36) and the mode is set to record (step 37).

Next, the cassette deck 3 is started in the recording mode (step 38), and the operation of the sequence generator 7 etc. is started (step 39). Then, the analog audio signal SA1 supplied to the terminal 1
Is A / D converted at a sampling frequency of 24 KHz and written in the RAM 9 (step 40).

Audio data of 12 msec, which is obtained by dividing audio data of 600 msec into each 50 msec, is read out from the RAM 9 by rearranging at a clock of 32 KHz and with a scramble pattern according to the key code, and time-axis compression processing is performed. At the same time, scramble processing is performed (step 41). At this time, the read address is controlled to form the signal of the margin portion.

Then, the bit signal and the burst signal from the generating circuit 16 are added (step 42) and supplied to the cassette deck 3 and recorded on the magnetic tape (step 4).
3). Follow the steps 40 to 43 for the keyboard 1
Repeat until the 7 stop key is turned on.

When the stop key is turned on in step 44, the cassette deck 3 is set in the stopped state (step 45), and the process returns to step 32.

When the reproduction key is turned on in step 34, the mode is set to reproduction (step 46), the cassette deck is started in the reproduction mode (step 47), and the sequence generator 7 and the like are operated. The operation is started (step 48).

Next, the secret code detected by the detection circuit 11 is loaded from the reproduction signal SA2 (step 49), and the secret code detected in the next block is loaded (step 50). Then, the two consecutively detected personal identification codes are compared with the personal identification code input from the keyboard 17 (step 51), and it is determined whether or not the personal identification codes are unmatched (step 52). In this case, if one of the two consecutively detected personal identification codes does not match the input personal identification code, it is judged as unmatched.

If there is no match in step 52,
Returning to step 50, the secret code detected from the next block is loaded, and in steps 51 and 52, the comparison judgment is similarly performed.

If there is no unmatch in step 52,
The key code detected by the detection circuit 11 is loaded from the reproduction signal SA2 (step 53), and the key code detected in the next block is loaded (step 54).
Then, the two consecutively detected key codes are compared (step 55), and it is determined whether or not the key codes are unmatched (step 56). In this case, if two consecutively detected key codes do not match, it is judged as unmatched.

If there is no match in step 56,
Returning to step 54, the key code detected from the next block is loaded, and in steps 55 and 56, the comparison judgment is similarly performed.

When it is not unmatched in step 56,
A descramble pattern is set according to the detected key code (step 57).

Then, the reproduction signal SA2 is A / D converted at a sampling frequency of 32 KHz, and only the audio data corresponding to the areas # 1 to # 12 of a certain block is written in the RAM 9 (step 58).

Then, the audio data of the areas # 1 to # 12 which compose each block from the RAM 9 is set to 24 KH.
The data is rearranged and read by the z clock and the descramble pattern, and the time axis expansion process and the descramble process are performed (step 59). This allows
The descrambled analog audio signal SA4 is output to the audio-out terminal 15.

Next, the personal identification code detected from the three consecutive blocks is compared with the input personal identification code, and the key codes detected from the three consecutive blocks are compared with each other (step 60).

Next, it is judged whether or not the secret code is unmatched (step 61). When at least two or more personal identification codes do not match the input personal identification code, it is judged as unmatched. When it is determined that there is no match in step 61, the secret code detected by the detection circuit 11 is loaded from the next block (step 62), and the process returns to step 60 to determine the mismatch of the secret code.

If the secret code is not unmatched in step 61, it is determined whether or not the key code is unmatched (step 63). If at least 2 or more key codes do not match, it is judged as unmatched. Step 6
When it is determined that there is no match in step 3, the key code detected by the detection circuit 11 is loaded from the next block (step 64), and the process returns to step 60 to determine the mismatch between the personal identification code and the key code.

As described above, when the secret code or the key code is unmatched, the processes of steps 57 to 59 are not performed, and the time axis expansion process and the descramble process of the audio data in the areas # 1 to # 12 of the next block are performed. Is stopped.

When it is determined in step 63 that the key code is not unmatched, it is determined whether or not the stop key is turned on (step 65). If not, the process returns to step 57 to proceed to the next block. The time axis expansion processing and descrambling processing for the signal are continuously performed.

If the stop key is turned on in step 65, the cassette deck 3 is stopped (step 45), and the process returns to step 32.

As described above, in this example, the audio signal can be scrambled and recorded on the magnetic tape, and can be recorded with confidentiality.

Further, since the audio signal is subjected to time-axis compression processing so that there is a margin in time and a header portion is provided for each block and a key code and the like are recorded simultaneously with the audio signal, it is detected from the reproduced signal during reproduction. The descramble pattern corresponding to the generated key code can be used to descramble the audio signal, and the original audio signal can be easily reproduced.

Further, in the present example, in addition to the key code, the personal identification code input by the user from the keyboard 17 is recorded in the header portion, and the personal identification code detected from the reproduction signal during reproduction is identical to the personal identification code input by the user. When not doing so, the operation of the descramble processing is not started, so only the user who recognizes the personal identification code can reproduce the original audio signal by the descramble processing, improving the confidentiality. You can

When the personal identification code detected from the reproduction signal at the time of reproduction does not match the personal identification code input by the user twice in a row, the descrambling process is not started, so that the magnetic tape is not damaged. Even if an error occurs in the PIN code detected from the playback signal due to a physical failure and it happens that the PIN code coincides with the input PIN code, the descrambling process will not start unless the error is continuous. , The confidentiality of the secret code can be maintained well.

After the personal identification code detected from the reproduced signal coincides twice with the personal identification code input by the user and the operation of the descrambling process is started, the personal identification code detected in three consecutive blocks. When at least two or more personal identification codes match the personal identification code input by the user, the descrambling process is continuously performed. Therefore, even if an error occurs in the secret code detected from the reproduction signal due to a physical obstacle such as a scratch on the magnetic tape, the descrambling process is not interrupted unless the error is continuous.

Further, in the present example, when the key code detected from the reproduction signal at the time of reproduction is not the same twice consecutively, the descrambling process based on the key code is not started, and an erroneous descrambling process is not started. It is possible to prevent the pattern from being descrambled.

After the key code detected from the reproduced signal becomes the same twice consecutively and the descrambling operation is started, at least two or more of the key codes detected in three consecutive blocks are detected. When the key codes of the two coincide with each other, the descrambling process based on the key code is performed. Therefore, even if an error occurs in the key code detected from the reproduction signal due to a physical obstacle such as a scratch on the magnetic tape, if the error is not continuous, the descrambling process based on the correct key code will be interrupted. There is no.

In this example, the audio signal of 600 msec is divided into 12 periods of 50 msec each, and the scrambling process is performed by rearranging these. In this case, the audio signal in each period after rearrangement becomes discontinuous, and if recording is performed continuously as it is, there is a possibility that signals near both ends of each period may be lost or changed due to a transient phenomenon or the like during recording and reproduction. is there. In this example, the signal obtained by extending the signal at both ends of the audio signal in each period is arranged and recorded as the signal at the margin for a predetermined period. It is possible to prevent the data from being lost during the recording / reproduction, and the original audio signal can be well reproduced by the descrambling process.

In the above embodiment, 600 ms
The ec audio signal is divided into 12 periods of 50 msec each, and the scrambling process is performed by rearranging the audio signals in a scrambling pattern according to the key code, but the scrambling process format is not limited to this. .. However, due to the descramble processing,
It is necessary to place the key code in the header part.

Further, in the above-mentioned embodiment, the example of recording and reproducing the audio signal on the magnetic tape is described, but the present invention is similarly applied to the case of recording and reproducing on the magnetic disk or the one for optically recording and reproducing. be able to.

[0096]

According to the present invention, since the audio signal is scrambled and recorded on the recording medium, the recorded contents can be made confidential. Also, since a key code is recorded at the same time as the audio signal by providing a header section, the key code is detected from the header section during playback, and the audio signal of the segment section is descrambled based on this key code to reproduce the original audio signal. Can be easily reproduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a recording / reproducing apparatus.

FIG. 2 is a diagram for explaining determination of a personal identification code.

FIG. 3 is a diagram for explaining determination of a key code.

FIG. 4 is a flowchart showing the operation of the CPU.

FIG. 5 is a flowchart showing the operation of the CPU.

FIG. 6 is a diagram for explaining a format of a recording signal.

FIG. 7 is a diagram for explaining a format of a header part.

FIG. 8 is a diagram for explaining a format of a segment part.

FIG. 9 is a diagram for explaining a rearrangement process and signals of a margin portion.

FIG. 10 is a diagram showing a frequency spectrum of a recording signal.

[Explanation of symbols]

 1 Audio-in terminal 2, 14 Switch circuit 3 Cassette deck 4 CPU 6 A / D converter 7 Sequence generator 9 RAM 11-bit burst detection circuit 12 D / A converter 15 Audio-out terminal 16-bit burst generation circuit 17 keyboard 18 synthesis circuit

Claims (2)

[Claims] 1. A block comprising a header section having a key code and a segment section having an audio signal scrambled by a scrambling pattern corresponding to the key code for a predetermined period is continuously recorded on a recording medium. Characteristic audio signal recording method. 2. The audio signal is obtained by subjecting an input audio signal to A / D conversion at a first frequency and then D / A conversion at a second frequency higher than the first frequency. The audio signal recording method according to claim 1.