Importance

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Abstract

Many low bit rate digital audio encoding systems, including Dolby Digital and MPEG-2 AAC generate data streams in which unused dummy, fill, stuffing, or null bits exist whenever the bit allocation function in the encoder does not utilize all available bits from a bit pool. Instead, all or some of such wasted bits are used to carry information. This can be accomplished after an encoder generates a bitstream. The resulting bitstream is analyzed to identify the locations of some or all of the unused bits. Some or all of the identified unused bits are then replaced with information-carrying bits to embed information-carrying bits in locations formerly occupied by unused bits. Alternatively, instead of replacing some or all unused bits in the bitstream with information-carrying bits after encoding, a modified encoder may insert information-carrying bits in some or all of the unused bit positions during the encoding process.

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First Claim