Abstract: Apparatus for eliminating the truncation errors associated with a multiplicative leak factor employed in a predictive coding arrangement adds a temporally varying control signal that affects the leak factor multiplication output. Specifically, in one embodiment the leak factor multiplication output is modified by arbitrarily changing, or dithering, the level of the mean signal. In another embodiment, the leak factor multiplication output is modified by effectively dithering the leak factor itself. The latter is accomplished by adding the varying control signal prior to the truncated division which occurs in the leak factor multiplication process.

Abstract: Encoded blocks of video information are selected for transmission at a plurality of channel rates based on the corresponding location of the portions of the video image represented by the encoded blocks. Each encoded block is designated an image type which determines its transmitted channel rate. The image types are associated with spatial positions of a video image such that encoded blocks within a first area of the video image are designated a first image type and encoded blocks within a second area of the image are designated a second image type. In general, data blocks representing the central portion of the video image are transmitted at a channel rate having less susceptibility to noise or other degradation, thereby ensuring that such portion can be received in fringe areas.

Abstract: A vector codebook with an ordered set of vector entries that satisfy a prearranged continuity requirement is used to encode signals. The continuity requirement specifies that consecutively considered vectors may not differ from each other by more than k elements, where k is less than the number of elements in the vectors. In one embodiment, two memories are maintained. One for determining the best codebook vector selection, and one for quantizing the input signal in accordance with the selected vector. Recognizing the possibility that the best ordering possible for a given set of codebook vectors can not satisfy the continuity requirement, the vector codebook arrangement of this invention is enlarged in such a case to include additional vectors that are interposed in the sequence of vectors and arranged to maintain the continuity requirement.