Codebook

About: Codebook is a research topic. Over the lifetime, 8492 publications have been published within this topic receiving 115995 citations.

Systems and methods of encoding using a reduced codebook with adaptive resetting

Abstract: To feedback MIMO channel conditions, a codeword from a codebook is selected. To reduce signalling, the codewords are organized into codeword subsets. The receiver signals an index of a codeword into a current codeword subset previously made known to the transmitter. The current codeword subset is adaptively selected based on a threshold criterion. For example, if the best codeword from the current codeword subset is not sufficiently similar to the best codeword in the full codebook, a switch in the codeword subset is made.

Two-stage vector quantization-lattice vector quantization

Abstract: A two-stage vector quantizer is introduced that uses an unstructured first-stage codebook and a second-stage lattice codebook. Joint optimum two-stage encoding is accomplished by exhaustive search of the parent codebook of the two-stage product code. Due to the relative ease of lattice vector quantization, optimum encoding is feasible for moderate-to-large encoding rates and vector dimensions, provided the first-stage codebook size is kept reasonable. For memoryless Gaussian and Laplacian sources, encoding rates of 2 to 3 b/sample, and vector dimensions of 8 to 35 the signal-to-noise ratio performance is comparable or superior to equivalent-delay encoding results previously reported. For Gaussian sources with memory, the effectiveness of the encoding method is dependent on the feasibility of using a large enough first-stage vector quantizer codebook to exploit most of the source memory. >

Improved decoder for transform coding with application to the JPEG baseline system

Abstract: Transform coding, a simple yet efficient image coding technique, has been adopted by the Joint Photographic Experts Group (JPEG) as the basis for an emerging coding standard for compression of still images. However, for any given transform encoder, the conventional inverse transform decoder is suboptimal. Better performance can be obtained by a nonlinear interpolative decoder that performs table lookups to reconstruct the image blocks from the code indexes. Each received code index of an image block addresses a particular codebook to fetch a component vector. The image block can be reconstructed as the sum of the component vectors for that block. An iterative algorithm for designing a set of locally optimal codebooks is developed. Computer simulation results demonstrate that this improved decoding technique can be applied in the JPEG baseline system to decode enhanced quality pictures from the bit stream generated by the standard encoding scheme. >

Delta code messaging

Abstract: A method of communication of digital messages with improved efficiency through the use of the transfer of difference data between devices. In one aspect of the invention, the difference data communicated is between different generations of a derived message sequence such as an email thread. In another aspect of the invention, the messages are encoded by means of a codebook, and the difference data communicated is between different versions of the codebook. In this second aspect of the invention, the codebooks may automatically utilise the difference data to adapt their efficiency, and the codebooks may be automatically customised for specific individuals or groups.