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.
An apparatus for processing digital data signals which may be used in recording/reproducing and transmitting/receiving of such signals. During recording or transmission, error correction codes are added to the digital signals and a portion of such error correction codes is replaced with other information. Such other information may provide an indication as whether the digital signals are original signals or a copy thereof. During reproduction or reception, the other information is extracted and utilized in a predetermined manner. For example, reproduced digital signals may or may not be outputted depending on whether the extracted information indicates that the digital signals are original signals or a copy thereof. As a result, unauthorized copying of signals may be discouraged or prevented. Furthermore, by replacing a portion of the error correction code with the other information, storage capacity for the digital signals and/or the rate for processing such signals may not be adversely effected.
A voice decoder detects channel errors and loss of cryptographic synchronization using the change in spectral energy between sequential frames. The change in energy between frames is determined between corresponding LSP's of said successive frames and summed together. A running average of the change in energy for a predetermined number of frames is maintained. Current voice frames are eliminated based on the difference between the change in energy associated with the current frame and the running average. Accordingly, offensive audio associated with such channel errors or cryptographic synchronization loss is eliminated.
