JP2001197041A - Device and method for encoding and decoding audio data - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decode and reproduce audio data of a certain frequency band even if a security key is not available and a code can not be decoded. SOLUTION: Inputted audio data are divided into plural frequency bands and encoded and outputted by a data encoder 105. An encipher unit 107 enciphers encoded data of specific frequency bands among the mentioned encoded data according to the security set by a security setting control part 101 and a multiplexer 109 multiplexes and outputs the results. A deciphering device having received them deciphers the code by a code decipher unit 205 according to the security from a security resetting control part 201 and decodes and outputs the result by a data decoder 207.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an audio data encoding / decoding apparatus and method for encoding, encrypting and encoding audio data, and decoding, decoding and reproducing the audio data.

[0002]

2. Description of the Related Art Conventionally, as an audio encoding method,
Encoding methods such as MPEG-1 and MPEG-2 are known. These encoding methods are based on ISO (International Or
ganization for Standardization (International Organization for Standardization). Further, international standardization work on MPEG-4 as a general-purpose next-generation multimedia coding standard that can be used in many fields such as computer, broadcasting, and communication is in progress.

[0003] Further, with the spread of the above-mentioned digital encoding standards, the content industry has been strongly raising the problem of copyright protection. In other words, there is a problem that it is not possible to provide high-quality contents (images, audio information, and the like) with confidence for standards for which copyright protection is not sufficiently guaranteed. In order to protect the copyright of audio information, which is an example of such content, it is conceivable to encrypt the encoded data.

[0004]

However, the conventional encryption has the following problems. When the audio information is completely encrypted,
Even if you try to purchase the audio information, you cannot listen to it. Depending on the player that plays the audio information,
There is a possibility that a loud noise that may cause an abnormal operation or hurt the ear may occur.

[0005] The present invention has been made in view of the above-mentioned conventional example, and even when a security key is not provided or a decryption device that does not support encryption cannot decrypt the audio data, the audio data in a certain frequency band can be obtained. It is an object of the present invention to provide an audio data encoding / decoding apparatus and method for decoding and reproducing audio data.

[0006]

In order to achieve the above object, an audio data encoding apparatus according to the present invention has the following arrangement. That is, an input means for inputting audio data, a key input means for inputting a security key for applying security, and a code for dividing the audio data input by the input means into a plurality of frequency bands and encoding and outputting the divided data. Encoding means, the encoded data of a predetermined frequency band among the encoded data divided into a plurality of frequency bands by the encoding means, based on the security key input by the key input means And encryption means for performing encryption.

[0007] To achieve the above object, an audio data decoding apparatus according to the present invention has the following configuration. That is, an input means for inputting encoded data, a key input means for inputting a security key for unlocking security, and a predetermined one of encoded data divided into a plurality of frequency bands and encoded and encrypted. Decryption means for decrypting the encryption of the encoded data in the frequency band based on the security key input by the key input means, and the encoded data whose encryption has been decrypted by the decryption means or the encrypted encoding Decoding means for decoding data.

In order to achieve the above object, an audio data encoding method according to the present invention includes the following steps. That is, an input step of inputting audio data, a key input step of inputting a security key for applying security, and a code for dividing and encoding the audio data input in the input step into a plurality of frequency bands and outputting the divided data. Encoding step, the encoded data of a predetermined frequency band among the encoded data divided into a plurality of frequency bands by the encoding step, based on the security key input in the key input step And an encryption step of performing encryption.

To achieve the above object, the audio data decoding method of the present invention comprises the following steps. That is, an input step of inputting encoded data, a key input step of inputting a security key for unlocking security, and a predetermined one of encoded data which is divided into a plurality of frequency bands and encoded and encrypted. A decryption step of decrypting the encryption of the encoded data in the frequency band based on the security key input in the key input step, and the encoded data or the encrypted encoding decrypted in the decryption step. And a decoding step of decoding data.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

[Embodiment 1] FIG. 1 is a block diagram showing a configuration of an audio data encoding / decoding device according to Embodiment 1 of the present invention. FIG. 1 (B) indicates a decoding device.

In FIG. 1A, reference numeral 100 denotes a security key, which is key information for applying security. A security setting control unit 101 controls encryption of audio data based on the security key 100. Reference numeral 102 denotes input audio data, and reference numeral 103 denotes an analysis bank for dividing the audio data 102 into bands. Reference numeral 104 denotes a band division signal, which is an analysis bank 103.
Indicates a signal divided into a plurality of bands. A data encoder 105 receives and encodes the band division signal 104. Reference numeral 106 denotes compression-encoded data that has been compression-coded by the data encoder 105. Reference numeral 107 denotes an encryptor, based on the security key 100 set by the security setting control unit 101, for compressing the encoded data 1
06 is encrypted. Reference numeral 108 denotes encrypted data encrypted by the encryptor 107. A multiplexer 109 converts the encrypted data 108 into a bit stream and outputs the bit stream. 110 is a bit stream output by the multiplexer 109.

In FIG. 1B, reference numeral 200 denotes a security key set when releasing security. 20
Reference numeral 1 denotes a security release control unit, and a security key 20
Based on 0, decryption of the encrypted bit stream is controlled. 202 is an input bit stream,
A separator 203 separates the multiplexed input bit stream 202. Reference numeral 204 denotes encrypted data for each frequency band separated by the separator 203. The 205 decryption unit decrypts and decrypts the encrypted data 204 set by the security release control unit 201. 20
Reference numeral 6 denotes compressed encoded data restored by the decryption unit 205. A data decoder 207 decodes the compressed and encoded data 206. 208 is a data decoder 207
Is a band division signal decoded by A synthesis bank 209 synthesizes the band division signals 208 on respective frequency bands. Reference numeral 210 denotes an audio signal finally decoded by the synthesis bank 209.

Next, an operation procedure based on the above configuration will be described.

The security setting control unit 101, to which the security key 100 has been input, receives the security key 1
00, the encryption algorithm in the encryptor 107 is determined. Here, an example is described. For example, the security key 100 is an ASCII character and its ASCII
The value of the I character is added, and the lower bits 0 to 3 of the addition result
Is "0000", security is set to be effective, and the upper bits 4 to 7 are used as numbers of the encryption table. There are 16 combinations of these upper bits 4 to 7 with 4 bits,
One of them is decided.

FIG. 2 is a diagram showing an example of the encryption table according to the present embodiment.

Here, it is assumed that the number of bits does not change by encryption in order to maintain the original format.
FIG. 2 shows a case of a 3-bit encryption table.

In FIG. 2, the reason why the bit string of “111” is not changed by encryption is that when the sync code indicating the start point of the frame is all “1”, the sync code other than the start point of the frame is used. This is to prevent the same bit string from occurring. This encryption method may be any method as long as the number of bits is not changed.

The analysis bank 103 is a filter bank for dividing the input audio data 102 into a plurality of frequency bands. As a well-known method of division in the analysis bank 103, for example, there are a polyphase filter bank, DCT, MDCT, and the like. Also, filter bank and MDC like MPEG1Audio
There is also a method of combining T into a hybrid configuration.

[0020] The data encoder 105 outputs the band-divided signal 1
04 is compression-coded. This compression method is generally performed using an psychoacoustic model. Here, the band division signal 104 is further normalized by the scale factor Sc. Assuming that a group of band-divided signals 104 is Sq and a normalized signal is Sp, the relationship is S = Sc × Sp. As described above, the scale factor Sc and the normalized signal Sp are decomposed, and only the normalized signal Sp is encrypted. The encryptor 107 encrypts the compressed and encoded data 106 according to the encryption table set by the security setting control unit 101. At the time of data compression in the data encoder 105, there may be a case where bits allocated to a certain band are lost. In such a case, encryption of the band is not performed. In this way, in the encryptor 107, the band to be encrypted is determined in advance.

If the entire band is encrypted,
The contents of the encoded audio data can be made completely invisible. For example, if the audio data is encrypted only in the high-frequency band, the contents can be discriminated although it is unclear.

The multiplexer 109 converts the encrypted data 108 generated in parallel into a bit stream,
Various control information is also embedded in the bit stream.

Next, the operation of the decoding apparatus shown in FIG. 1B will be described.

The separator 203 receives the encoded and encrypted audio data 202, and performs the reverse operation of the multiplexer 109 to convert the bit stream 202 into encrypted parallel data 204. Encryption / decryption device 20
5 is the encrypted data 204 input in parallel.
Among them, the encrypted signal of the specific frequency band is decrypted based on the security key from the security release control unit 201. The encoded data 206 decrypted in this way
Is output to the data decoder 207. Data decoder 2
07 decodes the encoded data 206 and outputs it as a band division signal 208. Synthesis Bank 209
The band division signal 208 is synthesized on each frequency band, and a decoded audio signal 210 is finally output.

FIG. 3 is a flowchart showing an encoding process in the encoding device according to the first embodiment.

First, in step S1, audio data is encoded. In step S2, when the security key 100 is input, the process proceeds to step S3, where the encoding is performed based on the security key 100 set by the security setting control unit 101. A signal of a specific frequency band of the obtained audio data is encrypted. The encoded and encrypted audio data is multiplexed by the multiplexer 109 and output as a bit data string (step S4).

FIG. 4 is a flowchart showing a decoding process in the decoding device according to the first embodiment.

First, in step S11, encoded and encrypted audio data is input, and in step S12
To see if a security key to decrypt the code is entered. When the security key is input, the process proceeds to step S13, and the encryption is decrypted using the security key. Then, in step S14, the coded data whose code has been decrypted is decoded, and in step S15, it is output as an audio signal.

If it is determined in step S12 that the security key for decrypting the code has not been input, the process proceeds to step S12.
Proceeding to 14, the encoded data that has been encrypted is decoded, and output as an audio signal in step S15.

Therefore, when decoding an audio signal,
If a security key for decrypting the code is not input, that is, a user who does not have the right to listen to the audio signal can only normally reproduce the audio signal in a specific frequency band and encrypt the other frequency bands. The audio signal is reproduced as an audio signal that cannot be determined.
This allows the user to listen to the audio signal and determine whether to purchase the audio data.

Thus, by setting the frequency band to be encrypted to an appropriate band, even a user who does not have the right to listen to the audio signal can listen to a part of the audio signal.

[Second Embodiment] FIG. 5 is a block diagram showing a configuration of an audio data encoding / decoding device according to a second embodiment of the present invention. FIG.
(B) shows each of the decoding devices. The same components as those in FIG. 1 of the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 5, reference numeral 111 denotes a checksum generator, which generates a checksum indicating the type of the encryption algorithm set by the security setting control unit 101. The multiplexer 109 multiplexes the checksum generated by the checksum generator 111 into a bit stream. 21
A checksum error detector 1 detects a checksum error of the input bit stream 202 and determines the type of the encryption algorithm set by the security setting control unit 101 from the error value.

A major difference between the configuration of the second embodiment and the first embodiment is that checksum data is present. Taking the case of MPEG audio as an example, if the player detects a checksum error and performs processing to skip the frame, the bit stream 110 may have information up to the checksum conforming to the standard. . Therefore, the compressed encoded data 106 and
The encrypted data 108 does not necessarily have to have the same number of bits. Therefore, the encryptor 107 and the encrypted data 10
8, multiplexer 109, bit stream 110, input bit stream 202, separator 203, encrypted data 2
04, the encryption / decryption unit 205 can have a configuration different from that shown in the first embodiment.

Hereinafter, a characteristic operation in the second embodiment will be described with reference to FIG.

It is assumed that the security setting control unit 101 has been informed of information about what kind of encryption is to be applied from the user. The type of the encryption is represented by an integer called an encryption ID. Checksum generator 111 typically has
A value is generated such that the operation result is “0”. Here, a value is generated such that the operation result is an encryption ID, and is passed to the multiplexer 109.

The encryptor 107 converts the compressed and encoded data 106 into encrypted data 108 using an algorithm according to the encryption ID from the security setting control unit 101.
In the case of the second embodiment, as in the first embodiment,
The compression encoded data 106 and the encrypted data 108 do not necessarily have to have the same number of bits, and various encryption schemes can be adopted.

In the decoding apparatus shown in FIG. 5B, the checksum of the input bit stream 202 is released by the checksum error detector 211.
The value is not “0” but an encryption ID. This encryption ID
Is passed to the security release control unit 201, and an algorithm for decryption in the decryption unit 205 is determined. The encrypted data 204 is decrypted based on the determined algorithm, and the
Becomes Further, the encoded data 206 is decoded by the data decoder 207, and an audio signal 210 is obtained by the synthesis bank 209.

As described above, according to the second embodiment, only the encryption ID used in the encryption device is set as the checksum, and the decryption device extracts the encryption ID from the checksum. Thus, the encrypted data can be decrypted.

[Other Embodiments] In the above-described second embodiment, the checksum generator 111 has been described as a simple addition. However, the present invention is not limited to this. For example, a method such as CRC may be used. good. Security key 10
Although 0 has been described as an ASCII character, it may be a binary bit string.

In FIGS. 1 and 5 described above, a one-channel system has been described.
3. The data encoder 105, the encryptor 107, the encryption / decryption unit 205, the data decryption unit 207, and the synthesis bank 209 may have a multi-channel configuration.

Further, the functions of each part or all of the present embodiment may be described in software and processed by an arithmetic unit such as a CPU.

Even if the present invention is applied to a system including a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), a device including one device (for example, a copying machine, a facsimile machine, etc.) ) May be applied.

Another object of the present invention is to supply a storage medium (or a recording medium) in which a program code of software for realizing the functions of the above-described embodiments is recorded to a system or an apparatus, and to provide a computer (a computer) of the system or the apparatus. Alternatively, this can be achieved by a CPU or an MPU) reading and executing the program code stored in the storage medium. In this case, the program code itself read from the storage medium implements the functions of the above-described embodiment, and the storage medium storing the program code constitutes the present invention. By executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an operating system (OS) running on the computer based on the instruction of the program code. This also includes a case where some or all of the actual processing is performed and the functions of the above-described embodiments are realized by the processing.

Further, after the program code read from the storage medium is written into the memory provided in the function expansion card inserted into the computer or the function expansion unit connected to the computer, the program code is read based on the instruction of the program code. This also includes the case where the CPU provided in the function expansion card or the function expansion unit performs part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.

As described above, according to the present embodiment, even when there is no security key for decrypting the encrypted data, it is possible to reproduce audio to some extent and to reduce the frequency resolution for trial listening. become.

Also, even if the playback device is not an encryption-compatible playback device, the data created by the present encoding method does not cause the audio signal to be played back at all, and is played back by mixing noise of an appropriate volume. become. As a result, it is possible to prevent the reproduction apparatus from being abnormal or causing a volume that would hurt the ears.

[0048]

As described above, according to the present invention, there is an effect that audio data in a certain frequency band can be decrypted and reproduced even when the security cannot be decrypted without a security key.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an audio encoding / decoding device according to Embodiment 1 of the present invention.

FIG. 2 is a diagram illustrating an example of a 3-bit encryption table in the encryptor according to the first embodiment.

FIG. 3 is a flowchart showing processing of the audio encoding device according to Embodiment 1 of the present invention.

FIG. 4 is a flowchart showing processing of the audio decoding device according to Embodiment 1 of the present invention.

FIG. 5 is a block diagram showing a configuration of an audio encoding / decoding device according to Embodiment 2 of the present invention.

Claims (20)

[Claims] An input unit for inputting audio data; a key input unit for inputting a security key for applying security; and an audio data input by the input unit being divided into a plurality of frequency bands and encoded. Encoding means for outputting, and the security key input by the key input means, the encoded data of a predetermined frequency band among the encoded data divided into a plurality of frequency bands and encoded by the encoding means. An audio data encoding device, comprising: an encrypting unit that performs encryption based on. 2. An apparatus according to claim 1, further comprising an identification code providing means for providing the encoded data re-encrypted by said encryption means with an identification code used for encryption in said encryption means. The audio data encoding device according to claim 1. 3. The audio according to claim 1, further comprising a check bit assigning unit that assigns a check bit that always causes a bit error to the encoded data re-encrypted by the encrypting unit. Data encoding device. 4. The audio data encoding device according to claim 3, wherein the bit error caused by the check bit is information for identifying an encryption method. 5. The method according to claim 1, wherein the data is divided into the plurality of frequency bands, and the data is developed into a product of a scale factor and normalized data, and the encrypting means encrypts only the normalized data. The audio data encoding device according to any one of claims 1 to 4. 6. An input means for dividing audio data into a plurality of frequency bands and encoding the encoded data, and inputting encoded data for a predetermined frequency band out of the plurality of frequency bands, and for unlocking security. Generating means for generating a security key, decoding means for decoding the encrypted encoded data of the predetermined frequency band based on the security key, and decoding means for decoding the encoded data. An audio data decoding device, characterized in that: 7. The encoded data is always provided with a check bit in which a bit error occurs, a detecting means for detecting the bit error of the check bit, and when the bit error is detected by the detecting means, the code Means for determining that the encrypted data is encrypted and controlling the decryption means to decrypt the encryption,
The audio data decoding device according to claim 6, further comprising: 8. The encoded data is always provided with a check bit in which a bit error occurs, a detecting means for detecting the bit error of the check bit, and when the bit error is detected by the detecting means, the code 7. The audio processing apparatus according to claim 6, further comprising: means for determining that the encrypted data is encrypted, and controlling the decryption means to generate a security key for decrypting the encrypted data. Data decryption device. 9. When the encoded data is divided into a plurality of frequency bands and encoded, and the encoded data is in the form of a product of a scale factor and normalized data, the decryption unit decrypts the normalized data. 9. The audio data decoding device according to claim 6, further comprising a control unit. 10. An inputting step of inputting audio data, a key inputting step of inputting a security key for applying security, and dividing the audio data input in the inputting step into a plurality of frequency bands and encoding the divided audio data. An encoding step of outputting, and encoding data of a predetermined frequency band among encoded data divided into a plurality of frequency bands and encoded by the encoding step, the security key input in the key input step. An audio data encoding method, comprising: an encrypting step of performing encryption based on the audio data. 11. The method according to claim 11, further comprising the step of adding an identification code used for encryption in the encryption step to the encoded data encrypted in the encryption step. Item 11. The audio data encoding method according to Item 10. 12. The audio data code according to claim 10, further comprising a check bit assigning step of assigning a check bit that always causes a bit error to the encoded data encrypted in the encrypting step. Method. 13. The audio data encoding method according to claim 12, wherein the bit error caused by the check bit becomes information for identifying an encryption method. 14. The method according to claim 10, further comprising dividing the data into a plurality of frequency bands, expanding the data into a product of a scale factor and normalized data, and encrypting only the normalized data in the encrypting step. 14. The audio data encoding method according to any one of claims 13 to 13. 15. An inputting step of dividing audio data into a plurality of frequency bands and encoding the encoded data, and inputting encoded data encrypted for a predetermined frequency band among the plurality of frequency bands; A generating step of generating a security key, a decrypting step of decrypting the encoded data of the encrypted predetermined frequency band based on the security key, and a decoding step of decoding the encoded data. A method for decoding audio data, comprising: 16. A detecting step for detecting a bit error of the check bit, wherein a check bit that always causes a bit error is attached to the encoded data; 16. The audio data decoding method according to claim 15, further comprising the step of: determining that the data is encrypted and controlling the decryption in the decrypting step. 17. A detecting step for detecting a bit error of the check bit, wherein the coded data is always provided with a check bit that causes a bit error, and detecting the bit error in the detecting step, 17. The audio system according to claim 15, further comprising: a step of determining that the data is encrypted, and controlling to notify a security key for decrypting the decryption in the decrypting step. Data decryption method. 18. When the data is divided into a plurality of frequency bands and encoded, and the encoded data is in the form of a product of a scale factor and normalized data, the decryption step decrypts the normalized data. The method according to any one of claims 15 to 17, wherein the audio data is controlled. 19. A computer-readable storage medium storing a program for executing the audio data encoding method according to claim 10. Description: 20. A computer-readable storage medium storing a program for executing the audio data decoding method according to claim 15. Description: