JPH06231536A - Recording method for signal, signal recorder, reproducing method for signal and signal reproducer - Google Patents

Abstract

PURPOSE:To protect a copyright by ciphering a record signal when a digital video signal is compressed and encoded, and the signal is recorded/reproduced on a recording medium. CONSTITUTION:A digital video signal compressed and encoded by a compression encoder 2 is ciphered by a ciphering circuit 3 based on a key signal. This signal is encoded by an error correcting encoder 5, and recorded on a recording medium. At the time of reproducing, the signal is processed in a reverse order of the above operation, and a cipher is deciphered by the same key signal as that at the time of recording. Thus, since the ciphering is conducted after the signal is compressed and encoded, an efficiency of compressing and encoding the video having correlation in a vertical direction is not lowered. Since it can be ciphered at a low speed, realization of the circuit is facilitated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal for enciphering and deciphering a recording signal of a signal recording medium for the purpose of copyright protection when compressing and encoding a digital video signal or the like for recording and reproducing. The present invention relates to a recording method, a signal recording device, a signal reproducing method, and a signal reproducing device.

[0002]

2. Description of the Related Art In many conventional signal recording / reproducing devices, an analog signal is encrypted and recorded / reproduced on a signal recording medium, and a digital compression-encoded video signal is not encrypted and recorded / reproduced. . An example of a method for encrypting an analog video signal for the purpose of copyright protection is disclosed in Japanese Patent Application Laid-Open No. 61-288582. This will be described as a first conventional example.

This method is for encrypting a signal in the vertical blanking period of the video signal. Here, a commercially available video tape recorded by encryption can be reproduced by a general magnetic recording / reproducing apparatus (VTR), but if the signal to be reproduced is recorded (copied) on another tape, the VT on the recording side is recorded.
A malfunction occurs in the R synchronous system and the automatic gain adjustment function.

FIG. 3 is a waveform diagram of an encrypted signal according to such a system. That is, the pseudo sync signal Sc is inserted after the horizontal sync signal Sa and the burst signal Sb in one horizontal scanning line period within the encrypted vertical blanking period. The pseudo sync signal Sc is a signal in which a plurality of pulses that change within the range of the L level of the horizontal sync signal Sa and the H level (white level) of the luminance signal are arranged. This signal disturbs the periodicity in the reproduction of the horizontal synchronizing signal Sa during recording of the VTR, and V
This causes the TR to malfunction. In a general VTR, during recording, automatic gain adjustment is performed by the black level immediately after the horizontal synchronization signal Sa. Therefore, after the burst signal Sb, the pseudo-synchronization signal Sc is generated at the place where the black level signal should follow.
Comes, the VTR erroneously reproduces the position of the horizontal sync and erroneously recognizes it as the black level of this positive pulse. Therefore VT
The automatic gain adjustment during recording of R malfunctions. If such a coding process is applied to a commercially available soft tape for which copying is prohibited, the video signal cannot be normally rerecorded by the VTR, and copying can be prohibited.

Next, as a second conventional example, an encrypted analog video signal is recorded on a tape, and only the user who wants to reproduce the video signal is given a key indicating the encryption procedure to the VTR decoder to reproduce the video image. There is a way to allow.

FIG. 4 is a waveform diagram of a video signal showing the encryption and decryption processing in the second conventional example. (A) shows an original signal, (b) shows an encrypted signal, and (c) shows a decrypted signal. The encryption referred to here is, as shown in (b), the horizontal synchronizing signal Sa and the burst signal Sb within the horizontal scanning period.
The phase of the video signal in the effective video signal period is shifted for each scanning line with respect to the phase. The amount of phase shift shall have a periodicity of several fields. Then, when this video signal is displayed on the video display device, the screen sways left and right and overlaps, which makes it difficult to view the video. The phase shift amount of each scanning line is determined by a key.

On the other hand, in the decryption, the same key used for encryption is given, so that the horizontal synchronizing signal Sa and the burst signal S are shifted by the phase of the effective video signal period at the time of encryption.
The phase of b is shifted at the time of decoding. Then, the horizontal synchronization signal Sa and the burst signal Sb in each scanning line are controlled so that their relative phases are returned to the phases of the original signals during the effective video signal period as shown in FIG. 4C. In this method, the fluctuation of the relative phase between the scanning lines remains, but the amount is within the allowable range of the synchronous system of a normal video display device, so that the video can be viewed without any trouble.

FIG. 5 is a system diagram of a signal recording / reproducing method to which such an encryption method is applied. A video signal to be encrypted is input from the video input terminal 101 of the signal recording device. As described above, the encryption device 102 shifts the phase of the effective video signal period based on the given key. And Figure 4
The encrypted signal (b) of 1 is given to the VTR 103 and recorded on the tape. When this tape is supplied to a specific user, the VTR 104 on the signal reproducing side reproduces an encrypted signal as shown in FIG. 4B. When this signal is given to the decoding device 105,
The decryption device 105 decrypts the signal with a separately given key and outputs a video signal as shown in FIG.

Therefore, even if an encrypted and recorded tape is obtained, a normal video signal cannot be obtained if there is no decryption device or if there is a decryption key but no decryption key. , Illegal copying and viewing cannot be done.

[0010]

However, in the first conventional example, there is a device having a function of changing the encrypted sync signal portion of the input video signal into a normal sync signal. For example, a normal signal can be obtained through the device and can be easily copied. Many digital process devices having this function are currently on the market, and since these devices are also highly reliable for synchronous reproduction, there is no malfunction due to the pseudo sync signal Sc, and the encrypted horizontal sync signal can be transmitted normally. Turn it into a signal.

Some normal VTRs operate normally even if the pseudo sync signal Sc and the positive pulse are input depending on the model. Further, in this method, even if it is applied to recording and reproduction of a compression-coded digital video signal, the signal to be compression-coded is only the effective video signal period. Therefore, the horizontal and vertical sync portions outside the display screen are not encoded, and the encryption during the vertical blanking period is easily decrypted during playback. Or, there was a problem that it would be reproduced.

Next, the second conventional encryption method is a process of disturbing the spatial and temporal correlation of shifting the phase of the effective video signal period. Therefore, when a video signal is digitally compressed and encoded by utilizing the temporal and spatial correlation, and recorded and reproduced on the signal recording medium, a problem occurs. That is, if this encryption processing is performed before inputting to the signal recording device, the vertical correlation of the video signal is disturbed, and the compression efficiency is reduced. For this reason, even a normally restored signal may be deteriorated or the correlation of the video signal may be disturbed, which causes a problem that it cannot cope with an increase in the data amount.

The present invention has been made in view of the above-mentioned conventional problems, and can be applied to a device for digitally compressing and encoding a video signal for recording and reproducing, and the video signal can be converted without reducing the compression efficiency. An object is to realize a signal recording / reproducing method and a signal recording / reproducing apparatus for encryption.

[0014]

According to the invention of claim 1 of the present application, an error for compression-encoding a digital signal, encrypting the compression-encoded digital signal, and correcting a signal loss occurring in the process of recording / reproducing. It is characterized in that a correction code is added to the encrypted signal.

According to a second aspect of the present invention, there is provided a compression encoding circuit for compression encoding a digital signal, and an encryption circuit for encrypting a digital signal compression encoded by the compression encoding circuit based on a key signal. And an error correction coding circuit for adding an error correction code for correcting a signal loss occurring in the recording / reproducing process to the digital signal encrypted by the encryption circuit. .

A third aspect of the present invention is a signal reproducing method for reproducing a signal recorded by the signal recording method according to the first aspect, wherein an encrypted signal is reproduced from a signal recording medium, It is characterized in that the reproduced signal is decoded based on the error correction code added during recording, and the decoded signal is expanded and decoded into a digital signal by the same key signal as during recording.

The invention according to claim 4 of the present application is a signal reproducing device for reproducing a signal recorded by the signal recording device according to claim 2, wherein an encrypted signal is reproduced from a signal recording medium, An error correction decoding circuit that performs error correction using the error correction code added at the time of recording, a decoding circuit that decodes the cipher that has been error corrected by the error correction decoding circuit, and a compression code that is decoded by the decoding circuit And a decompression / decoding circuit for decompressing and decoding the encoded signal into the original digital signal.

[0018]

According to the invention of claim 1 or claim 2 having the above characteristics, the compression encoding circuit compresses and encodes the digital signal at the time of recording the video signal. The encryption circuit encrypts the compression-encoded digital signal based on the key signal. Next, the error correction coding circuit adds an error correction code for correcting signal loss during recording or reproduction to the encrypted digital signal. In this case, since the encryption processing is performed after the compression encoding, the efficiency of signal compression is not deteriorated and the encryption can be processed at a low speed.

Further, according to the invention of claim 3 or 4 of the present application,
When reproducing the video signal, the error correction decoding circuit reproduces the encrypted signal from the signal recording medium, and performs error correction using the error correction code added at the time of recording. Next, the decryption circuit decrypts the error-corrected cipher. Then, the expansion decoding circuit expands and decodes the decoded compression coded signal into the original digital signal. In this way, since the encryption decryption processing is performed after the error correction decryption, the encryption can be decrypted at a low speed.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A signal recording apparatus according to the first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing the overall configuration of the signal recording device in the first embodiment. In FIG. 1, the video signal is input to the compression encoding circuit 2 via the input terminal 1. The compression encoding circuit 2
It is a circuit for compressing and coding a video signal by utilizing the correlation between the video signal in the horizontal and vertical directions. The compression encoding circuit 2
For example, a discrete cosine transform (hereinafter referred to as DCT) is applied,
The DCT coefficient is quantized and variable length coding processing is performed.

Next, the encryption circuit 3 is a circuit which inputs the digital video signal compression-encoded by the compression encoding circuit 2 and encrypts it based on the key signal. As shown in FIG. 1, the encryption circuit 3 is composed of an exclusive OR circuit (EOR) 3a and a random number generation circuit 3b. The EOR 3a inputs the bit stream output from the compression encoding circuit 2, and when a key signal is applied to the input terminal 4, inputs a specific random number pulse output from the random number generator 3b, and outputs the exclusive OR of these. It is a circuit that generates a signal. The error correction coding circuit 5 adds an error correction code to the signal output from the encryption circuit 3,
This is a circuit for outputting a digital video recording signal from the output terminal 6.

The operation of the signal recording apparatus of this embodiment having the above structure will be described. The digitized video signal is input from the input terminal 1 and given to the compression encoding circuit 2. The random number generator 3b of the encryption circuit 3 generates a specific random number pulse according to the key signal input from the input terminal 4, and gives the signal to the EOR 3a. The EOR 3a takes the exclusive OR of the compressed digital video signal supplied from the compression encoding circuit 2 and the random number pulse, and outputs the signal as an encrypted signal to the error correction encoding circuit 5.

The error correction coding circuit 5 adds an error correction code to the encrypted video signal together with the data accompanying the recording, and outputs a digital video recording signal from the output terminal 6. Then, this signal is converted into a recording format and recorded on the tape.

As described above, according to this embodiment, the compression-encoded video signal is encrypted later, so that the compression-encoding efficiency can be processed without any adverse effect. Furthermore, since the amount of data is reduced by compression encoding, encryption processing can be performed at low speed.

Next, a signal reproducing apparatus according to the second embodiment of the present invention will be described with reference to FIG. FIG. 2 is a block diagram showing the overall configuration of the signal reproducing apparatus of the second embodiment. In the figure, the recording medium recorded by the above-mentioned signal recording device is reproduced by this signal reproducing device. The reproduced digital video signal is output to the error correction decoding circuit 12 via the input terminal 11. The error correction decoding circuit 12 is a circuit for detecting and correcting a code error using an error correction code, and its output is given to the decoding circuit 13.

The decryption circuit 13 has an EOR 13a and a random number generation circuit 1 as shown in FIG.
3b. The random number generator 13b has an input terminal 1
When the key signal is given to 4, the same random number pulse as that at the time of recording is generated, and its output is given to the EOR circuit 13a. The EOR 13a is a circuit for generating a signal of exclusive OR with the bit stream output from the error correction decoding circuit 12. The decompression decoding circuit 15 is the decoding circuit 1
3 is a circuit that expands the signal output from 3 and converts it to the original digital video signal. This signal is output as a digital video reproduction signal via the output terminal 16.

The operation of the signal reproducing apparatus of this embodiment having the above configuration will be described. The reproduction signal of the tape given through the input terminal 11 is a portion of the data in the signal format to which the error correction code is added. The error correction decoding circuit 12 corrects the error of the input data and outputs the portion of the video signal to the decoding circuit 13. Decoding circuit 13
When the same key signal as that at the time of recording is input from the input terminal 14, the random number generation circuit 13b generates a random number pulse in the same procedure as on the recording side and gives it to the EOR 13a.

The EOR 13a takes the exclusive OR of the output bit of the error correction decoding circuit 12 and the random number pulse, and decrypts the encrypted signal. The decompression decoding circuit 15 performs the decoding of the variable length code, the inverse quantization, and the inverse DCT in the reverse procedure of the compression encoding. Then, the compression-encoded video signal is expanded and decoded, and the original digital video signal is output from the output terminal 16.

As described above, according to the second embodiment, the video signal compression-encoded by the signal recording apparatus of the first embodiment is error-correction-decoded, then decrypted by encryption and expanded-decoded. ing. Therefore, the encrypted signal can be normally decoded without any adverse effect on the efficiency of the compression encoding. Further, since the encryption is decrypted in the compressed and encoded state as in the recording, the decryption process can be performed at a low speed.

In the first embodiment, the processing of the compression coding circuit 2 is based on DCT, quantization, and variable length coding, and the processing of the decompression decoding circuit 15 in the second embodiment corresponds to the inverse processing. However, the same effect can be obtained by using a process using the temporal and spatial correlation of other video signals. Further, although the processing related to the encryption of the encryption circuit 3 in the first embodiment and the encryption circuit 13 in the second embodiment are random number addition, the same effect can be obtained by using an encryption method such as block cipher. Is obtained.

[0031]

As described above, according to the inventions of claim 1 and claim 2 of the present application, the compression code is obtained by digitally compressing and encoding the video signal, and then encrypting and encoding the error signal. Efficiency does not decrease. Furthermore, since the encryption is performed in the compression-encoded state, the encryption process can be performed at low speed.

According to the third and fourth aspects of the present invention, when the signal recorded by the signal recording method and the apparatus according to the first and second aspects is reproduced, the error correction decoding of the reproduced signal is performed. After the encryption, the encryption is decrypted, and then the expansion decryption is performed. Therefore, it is possible to decode the digital compression coded video signal without adversely affecting the compression coding efficiency. Further, since the cipher is decrypted in the compression-encoded state, the cipher can be decrypted at a low speed.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a signal recording device in a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a signal reproducing device according to a second embodiment of the present invention.

FIG. 3 is a signal waveform diagram showing an example of a conventional encryption method.

FIG. 4 is a signal waveform diagram showing another example of a conventional encryption method.

FIG. 5 is a block diagram showing a general configuration of a conventional encryption method.

[Explanation of symbols]

 1, 4, 11, 14 Input terminal 2 Compression coding circuit 3 Encryption circuit 3a, 13a EOR 3b, 13b Random number generation circuit 5 Error correction coding circuit 6,16 Output terminal 12 Error correction decoding circuit 13 Decoding circuit 15 Decompression / decoding circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Seiji Nakamura 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (4)

[Claims] 1. A digital signal is compression-encoded, the compression-encoded digital signal is encrypted, and an error correction code for correcting a signal loss occurring in the process of recording and reproducing is added to the encrypted signal. Signal recording method. 2. A compression encoding circuit for compression encoding a digital signal, an encryption circuit for encrypting a digital signal compression encoded by the compression encoding circuit based on a key signal, and the encryption circuit A signal recording device, comprising: an error correction coding circuit for adding an error correction code for correcting a signal loss occurring in a recording / reproducing process to an encrypted digital signal. 3. A signal reproducing method for reproducing a signal recorded by the signal recording method according to claim 1, wherein an encrypted signal is reproduced from a signal recording medium, and the reproduced signal is recorded at the time of recording. A signal reproducing method characterized by decoding based on an added error correction code, and expanding and decoding the decoded signal into a digital signal by the same key signal as at the time of recording. 4. A signal reproducing device for reproducing a signal recorded by the signal recording device according to claim 2, wherein the encoded signal is reproduced from the signal recording medium, and the error correction added at the time of recording. An error correction decoding circuit that performs error correction using a code, a decoding circuit that decodes the cipher that has been error corrected by the error correction decoding circuit, and a compressed coded signal that is decoded by the decoding circuit as the original And a decompression / decoding circuit for decompressing / decoding to a digital signal.