KR980011023A - How to process audio data - Google Patents

Abstract

An audio data processing method provides a data encryption method for conditional viewing of MPEG audio.

The MPEG audio data according to the related art does not perform encryption for conditional viewing, so that there is a problem that the voice information is not upgraded and copyright infringement is possible.

The audio data processing method includes the steps of determining whether a program currently being broadcast is a pay program and reporting the program to a smart card, decoding the audio signal supplied with the decoding information and changing each area of the audio data in a predetermined order, And reconstructing the audio bitstream as information to output an audio frame. When applied to an audio-only receiver to which MPEG audio is applied, the descrambler and decryption information can be relatively easily configured by encrypting the most important area of the MPEG audio signal And a perfect scrambling effect can be obtained, thereby enabling the enhancement of the voice information and copyright protection.

Description

How to process audio data

The MPEG audio data according to the prior art does not perform encryption for conditional viewing, and thus, when audio-only broadcasting is started, there is a problem that information can not be advanced and copyright infringement is possible.

It is an object of the present invention to provide an audio processing method for conditional viewing of MPEG audio.

I, composition and function of invention

According to another aspect of the present invention, there is provided a method for processing audio data, the method comprising: receiving decryption information from a smart card;

Hereinafter, an audio data processing method according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 3 is a block diagram illustrating the configuration of an audio decoder according to the present invention. Referring to FIG. 3, the system includes a smart card 31 having encrypted data decryption information, A microcomputer 33 for determining whether the program is currently being broadcasted and reporting the result to the smart card 31 and reconstructing the original signal by receiving the decrypted information from the descrambler 32; And an audio decoder 34 decoding the decoded audio signal and outputting the decoded audio signal as a PCM signal.

Referring to the flow chart of FIG. 8 for encrypting and decrypting the audio decoder constructed as described above, first, an audio bitstream is received (S81), and it is determined whether the current program is conditional listening, that is, a channel program (S82) If it is a listening program, the smart card 31 is reported (S83).

If it is determined that the broadcast program is a pay broadcast, the smart card 31 has the decryption information and sends the decryption information to the descrambler 32 (S84).

The descrambler 32 decrypts the MPEG audio signal encrypted with the decryption information of the smart card 31 (S85). The microcomputer 33 receiving the decrypted information reconstructs the decrypted audio frame (S86) An audio frame is output to the audio decoder 34 (S87).

That is, in the case of a paid program, the smart card 31 usually decrypts the encrypted information by shuffling the data or decrypting the decrypted data.

1, the audio data is composed of a header area, a CRC area, an SCFSI and SCF area, a bit allocation information area, a subband sample area, and an additional information area, of which a header area, a scale factor area , The bit allocation information area is very important. Therefore, when only one bit is shifted or changed, it is completely different from the original sound.

A method of encrypting audio data according to the present invention includes a method of encrypting information other than header synchronization, a method of encrypting SCFSI and SCF, a method of encrypting bit allocation information, There is a method of encrypting the information other than the synchronization of the scale factor division information, the scale factor information, and the bit allocation information in combination.

First, a method for encrypting information other than the header is described with reference to FIG. 4 showing a structure of an MPEG audio header according to the present invention, and the header of audio data according to the present invention in FIG. A description will be made with reference to drawings for explaining a method of encrypting and a method of encrypting bits of audio data according to the present invention of FIG.

The MPEG audio header indicates basic information of one frame.

In the header, the areas # 12 to # 31 except for the synchronization (SYNC), that is, ID (Identification), layer, bit rate, sampling frequency and mode are very important. And outputs a voice signal.

The encryption of the header changes each area from the IDs of the areas # 12 to # 31 to the last bit in a predetermined order or changes the bits from # 12 bit to # 31 bit in a predetermined order.

The smart card 31 has information for decrypting the encrypted signal, and outputs the decryption key to the descrambler 32 when the program is charged.

The descrambler 32 converts the configuration of the header encrypted with the decryption key sent from the smart card 31 into the correct information and outputs it to the microcomputer 33. The microcomputer 33 restores the original signal using the decrypted header information And outputs it to the audio decoder 34.

A method of encrypting SCFSI and SCF information will be described with reference to the drawings for explaining SCFSI and SCF information encryption according to the present invention of FIG.

If there is an error in the SCFSI and the SCF among the audio data, the volume (the magnitude of the current in the analog output) differs from the value required in the original signal.

The SCFSI and SCF bits are changed in a predetermined order, and the same except for the synchronization of the headers described above, in the same order as in the case of encrypting and decrypting the encrypted signal. In this case, It is the same as the decoding process of changing order.

A method of encrypting another bit allocation information by a combination will be described with reference to the configuration of MPEG audio bit allocation information in FIG. 7. Since the bit allocation information is information for determining how many bits are allocated to each subband, The result is completely different from the original signal.

The bit allocation information is determined according to four tables in the decoder 34 according to a sampling frequency and a bit rate.

In the encryption using the bit allocation information, each area allocated by 6 bits is changed in a predetermined order or each bit is changed in a predetermined order.

The decryption and reconstruction of the encrypted signal is the same as the decryption of the method of replacing the bit and the area in a predetermined order except for the synchronization of the header described above.

A method for encrypting information other than synchronization among the headers of other audio data, scale factor division information, scale factor information, and bit allocation information in combination is a method in which the most important areas in audio data from the headers of audio data to bit allocation information are arranged in a predetermined order And then decrypt and reconstruct it in the same way as the above three encryption methods.

Therefore, the smart card 31 has decoding information for implementing the audio data processing method, and the descrambler 32 decodes the encrypted information by using the decoding information, thus the conditional listening system is simple and inexpensive.

C. Effect of the Invention

When the audio data processing method according to the present invention is applied to an audio-only receiver to which MPEG audio is applied, the descrambler and the decryption information can be relatively easily configured by encrypting the most important area of the MPEG audio signal, and a perfect scrambling effect can be obtained Thereby enabling the upgrading of the voice information and copyright protection.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a configuration of general MPEG audio data; FIG.

2 is a block diagram showing a configuration of a general audio decoder;

3 is a block diagram showing a configuration of an audio decoder according to the present invention;

4 is a diagram showing the structure of an MPEG audio header according to the present invention;

FIG. 5A is a diagram for explaining a method of encrypting the header of audio data according to the present invention by replacing each area except for the synchronization in a predetermined order. FIG.

FIG. 5B is a diagram for explaining a method in which bits other than the synchronization among the headers of audio data according to the present invention are changed in a predetermined order and encrypted. FIG.

FIG. 6 is a diagram for explaining SCFSI and SCF information encryption according to the present invention; FIG.

FIG. 7 is a diagram for explaining bit allocation information encryption according to the present invention; FIG.

8 is a flowchart illustrating an MPEG audio data processing method according to the present invention.

DESCRIPTION OF THE REFERENCE NUMERALS

31: smart card 32: descrambler

33: Microcomputer 34: Audio decoder

end. Object of the invention

(1) Description of the Prior Art

The present invention relates to MPEG, and more particularly, to a method of encrypting audio data for conditional viewing of MPEG audio.

In general, MPEG audio is the most widely used speech compression algorithm and is being adopted not only for general players but also for broadcasting decoders such as satellite broadcasting standards.

In general, scrambling for conditional viewing is usually used for video signals, but encryption of the MPEG audio signal is necessary to enhance the quality of audio information and copyright protection, such as the appearance of audio-only channels.

The MPEG audio data includes a header area having information on synchronization, a bit rate, a sampling frequency and a mode, a CRC (Cyclic Redundancy Checking) field with information on error checking and concavity as shown in the diagram of the general MPEG audio data of FIG. (SCF), which is the maximum absolute value of three subframes per subband, is used only in Layer 2, and the subframe is used only for the subframe. SCFSI (Scale Factor Subband Information) and SCF (Scale Factor) areas with SCFSI, which are information on how many sub-band samples per subband are represented by SCFs, and bit allocation information areas A subband sample area having an audio sample passed through the filter, and an additional information area which the manufacturer can arbitrarily use.

2 is a block diagram showing the configuration of a general audio decoder. The general audio decoder is composed of a microcomputer 21, an audio decoder 22, and a converter 23.

The microcomputer 21 receives the demodulated audio bitstream, controls the audio decoder 22, and outputs audio frames by initializing and controlling the audio signal.

The audio decoder 22 receiving the audio frame output from the microcomputer 21 decodes the audio frame and outputs PCM (Pulse Code Modulation) data. The converter 23, receiving the PCM data, Converts the signal into an analog signal and outputs it.

One of the audio frames is a stream in which a discrete signal 1152 samples are encoded.

The sampling frequency is selected from 44.1 kHz, 48 kHz, and 32 kHz. The bit rate is selected from 32, 48, 56, 64, 80, 96, 112, 128, 160 and 192 kbps per channel.

Audio data having a compression ratio of about 3.5-5.5 is appropriately allocated to low, middle, and high frequencies (32 subbands) according to a 4-bit allocation table according to a sampling frequency and a bit rate, .

The decoding process of the audio decoder 22 will be described in more detail. First, a frame in the audio data on the MPEG stream is recognized by recognizing the sync in the header area.

Skip, and repeat are determined by determining whether the data of the read frame is correct or not, as the CRC information of the CRC area.

Then, the number of bits for each subband is determined using the bit allocation information of the bit allocation information area, and the subframe sample value of the subband sample area is multiplied by the SCFSI and the scale factor value of the SCF area.

And then passes through a Synthsis Filter (not shown) to determine the audio sample value and outputs the audio sample value in PCM format.

The audio data of the prior art is not encrypted even when the video signal is encrypted for conditional viewing so that the input audio data is decoded and output without decryption process so that conditional viewing is not possible even when an audio dedicated channel appears.

Claims (6)

The method comprising the steps of: confirming whether the program currently being broadcast is a paid program; decrypting the audio signal by decoding each area of the audio data in a predetermined order, receiving the decryption information; reconstructing the audio bitstream as decoded information, And outputting the audio data. The decoding method as claimed in claim 1, wherein the step of decoding the audio signal comprises decoding the audio signal in which the areas other than the header synchronization, the scale factor division information, the scale factor information, and the bit allocation information are changed in a predetermined order A method for processing audio data. The method of claim 1, wherein the decoding of the audio signal comprises decoding the audio signal in which the bits of the information are changed in a predetermined order in addition to the synchronization of the audio data header by receiving the decoding information. The method of claim 1, wherein the decoding of the audio signal comprises decoding the audio signal having the decoded information and the scale factor division information and the scale factor information bits of the audio data in a predetermined order. The method of claim 1, wherein the decoding of the audio signal comprises decoding the audio signal in which the decoded information is supplied and the bit allocation information of the audio data is changed in a predetermined order. The method of claim 1, wherein the decoding of the audio signal comprises decoding the bidirectional bidirectionally decoded audio data, and decoding the bidirectional audio data. ※ Note: It is disclosed by the contents of the first application.