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Audio scrambling system for scrambling and descrambling audio signals
| Details |
Inventors: Ibaraki, Susumu; Katta, Noboru; Nakamura, Seiji; Murakami, Hiroki;
Assignee: Matsushita Electric Industrial Co., Ltd. (Osaka-fu, JP)
Primary Examiner: Tarcza; Thomas H.
Assistant Examiner: Sayadian; Hrayr A.
Attorney, Agent or Firm: Wenderoth, Lind & Ponack
A scrambling system includes a scrambling apparatus and a descrambling apparatus for scrambling and descrambling digital audio codes having plural sub-band units. Each sub-band unit includes at least a scale factor and a quantized sample data which is quantized after scaling with the scale factor. In the scrambling apparatus, a sample period during which the quantized sample data is present is detected, and only the quantized sample data is scrambled at the sample period. In particular, the quantized sample data and data other than the quantized sample data are separated, and the separated quantized sample data is applied to a scrambler, and the other data is applied to a delay circuit. The separated and scrambled quantized sample data and the delayed data are synthesized. The descrambling apparatus also detects a sample period during which the quantized sample data is present, and descrambles only the scrambled quantized sample data at the sample period. |
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DETAILED DESCRIPTION Therefore, the first object of the present invention is to provide an audio scrambling system for processing any pulse-code modulation (PCM) digital audio signal without needing to transfer non-audio data, with relatively high security, and without producing a scrambled audio signal that is unpleasant to the listener's ear.
A second object of the invention is to provide an audio scrambling system for encrypting data comprising plural codes, one of which is a reserved code, and which can execute reserved code management; can be achieved by a simple hardware configuration; and can use any desired encryption method.
A third object of the invention is to provide an audio scrambling system for a scrambling digital audio code comprising plural sub-band units, each sub-band unit comprising scale factor information and a quantized sample data quantized after scaling with the scale factor; and which does not result in a scrambled audio signal that is unpleasant to the listener's ear.
According to the first embodiment of the invention, in a scrambling system comprising a scrambling apparatus and a descrambling apparatus for scrambling and descrambling a digital audio signal having a plurality of sample data units, each unit having a predetermined bit length, the scrambling apparatus comprises: first detection means for detecting a first portion and a second portion in each sample data unit; and encryption means for encrypting said sample data unit only at said second portion, and for producing a scrambled sample data unit; and the descrambling apparatus comprises: second detection means for detecting said first portion and said second portion in each scrambled sample data unit; and decryption means for decrypting said scrambled sample data unit only at said second portion, and for producing a descrambled sample data unit.
According to a preferred embodiment, the first portion and the second portion is separated by a next-most-significant bit which is the highest order bit with a value which is not equal to that of a most-significant bit in said sample data unit, and said next-most-significant belonging to said first portion
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Multiplexer-related 
