Abstract: A signal coder is disclosed with improved compression of pictorial data that has been decomposed into plural subbands through a two-dimensional quadrature-mirror decomposition (102). In each of the higher frequency bands, the decomposed samples are quantized and then partitioned (106, 110, 114), in two dimensions, into blocks. The blocks in each band are scanned (107, 111, 115) in a way that exploits the characteristics of the band so as to increase the average length of the runs of zero and nonzero quantized samples. The bands containing horizontal, vertical and diagonal edge information are scanned with a horizontal, vertical, and diagonal zig-zag pattern, respectively. These scanned bands are entropy coded (108, 112, 116) using run-length coding to code the runs of either zero band or nonzero quantized samples.

Abstract: A highly efficient video coding scheme is disclosed which codes, for transmission, the pel values of a scanned high quality HDTV video signal in such a manner that a low-quality version of the signal as well as a high-quality version are available to different video subscribers. The coder includes a basic layer coder (110) and a contribution layer encoder (150). A subscriber to a low-quality video service receives only the basic layer signal while a high-quality video subscriber receives both the basic layer signal and the contribution layer signal, which when combined together enable the high quality video signal to be reconstructed. The basic layer coder codes the baseband of a frequency decomposed video signal using a hybrid discrete cosine transform/differential pulse code modulation coding structure, such as the CCITT recommended H.261 coder.

Abstract: A video coder is disclosed which codes the digital pel values of a video signal in such a manner that different levels of picture quality, i.e. resolution, are available to users. The coder uses a two-dimensional quadrature-mirror filter (103) to decomposes the input into plural subbands. The baseband lowest horizontal-lowest vertical frequency subband is coded using a hybrid DCT/DPCM coder (104) that is compatible with a proposed CCITT standardized codec. The output of this coder is a layer 1 signal which is available to subscribers who desire only low-quality video service. The other subbands are coded using an interframe DPCM coder (108, 109, 110, 111) for those subbands in which the filtered samples in the subband represent horizontal or vertical edge variations in the video frame, or an intraframe PCM coder (116, 117) for those subbands in which the filtered samples in the subband represent diagonal variations.

Abstract: A method and apparatus (110) for performing block-matching motion estimation in a video coder is disclosed which estimates the motion vector associated with each block of pels in the current coding frame. The motion vector for each block in the current frame is estimated by searching through a larger search window in the previous frame for a best match. At each possible shift position within the search window a pel-by-pel comparison (304) is made between the intensity of the pels in the block in the current frame and the corresponding pels in the previous frame. Each pel is classified as either a matching pel or a mismatching pel depending upon the pel difference and a threshold (306). The number of matching pels at each possible shift position is counted (307) and the motion vector is determined from the shift position that yields the maximum number of matching pels.

Abstract: A method and apparatus for achieving a high compression of a video signal. The PEL-by-PEL difference between an input signal consisting of digital PEL values of a scanned video signal and a motion compensated interframe prediction signal is decomposed into several narrow bands using separable two-dimensional quadrature mirror filtering (105). Each sub-band is quantized by a symmetric uniform quantizer (106-1-106-4) with a center dead zone. Entropy coders (124-1-124-4) code the quantized values by variable word-length coding the nonzero quantized values and transmitting that information with the corresponding run-length coded positional information. The outputs of the coders are combined by a multiplexer (108), the output of which is input to a buffer (123) which produces a constant rate bit stream.

Abstract: An improved low bit-rate interframe video encoder is disclosed of the type known as a hybrid coder. A hybrid coder achieves image compression by using a two-dimensional signal transformation on blocks of differential pel data in the forward loop of a DPCM coder. The transform coefficients of each block are then quantized and entropy coded for transmission. Coding efficiency is in part determined by the size of the transform block. Larger blocks are more bit efficient because of the lower quantity of overhead data required, but require a complex transformer hardware implementation. In addition, larger blocks produce annoying block distortion. The disclosed coder has the advantages of both large and small block size division of the video image. In the disclosed coder, after differential combination (307) with a corresponding block from the previous frame, each m.times.m block of pel data is sub-divided (309) into smaller n.times.

Abstract: In the transmission of PCM coded picture elements (pels), the level value of each pel of an image is quantized in accordance with one-of-a-plurality of quantization schemes that is determined by the quantized level values of adjacent neighbor pels. Each of the quantization schemes is configured from the relative frequency of occurrence of each pel level value for a given combination of neighbor pel level values. Various embodiments may involve grey-level values of each pel of an image, the three-dimensional red, green and blue level values of an image quantized in accordance with a three-dimension quantization scheme determined by the three-dimensional quantized level values of adjacent neighbor pels, or three-dimensional color values that a prequantizer quantizes and linearizes into one-dimension that are then conditionally quantized using one-dimensional grey-level techniques.

Abstract: In a first embodiment, an image signal is segmented into bilevel and multilevel regions. The picture elements, or pels, representing the bilevel regions are center-thresholded and encoded using a two-dimensional CCITT coding scheme. The pels representing the multilevel regions are coded in a differential pulse code modulation (DPCM) coder. The resulting DPCM errors are coded by an intermediate coder which assigns the i.sup.th one of an ordered plurality of codewords to represent each pel whose value is the i.sup.th most-frequently-expected to occur, given the values of predetermined ones of the neighbor pels. The intermediate codeword values are assigned such that the intermediate coder output stream contains long bit runs. That output stream is then run- and variable-length coded in accordance with a one-dimensional CCITT bilevel image coding scheme.