Abstract: A feed-forward bit-rate control system that selects and formats DQUANT values in real time for optimal semantically-encoded image transmission by video-compression codecs complying with the ITU-T standards H.263 or H.263E. The system uses a prequantization process to reduce the computational load imposed by the quantizer optimization calculations required for feed-forward semantic coding bit-rate control. The H.263 CBPY and MCBPC coding tables are reordered so as to be indexed using an orthogonal flag-based index values and the RLA coding table is block-indexed using clipped amplitude values, for faster access into these tables. The system also uses a rate-assist process to assure that DQUANT values are provided in each edge macroblock that follows a transition to and from each semantically-defined region when the edge macroblocks have four motion vectors by reducing the number of motion vectors in the macroblock to one.

Abstract: A facility for mapping a plurality of different Virtual Circuit Channels (VCC) into a single VCC is provided for use in a data network. In operation, the facility assembles, in turn, data cells each having a data payload and appropriate header identifying a respective VCC into a series of data cells. The series is then segmented into a predetermined number of data payloads, and a header identifying a common connection over the network is then appended to each of the payloads. The result is then transported over the data network via the common connection.

Abstract: Apparatus and methods are provided for generating an output signal representing an initial Huffman Coding rate for use in compressing a received digital signal. The digital signal includes a plurality of digital sets wherein ones of the digital sets are non-unique. Ones of the digital sets are stored and an indicator is associated with each. The indicator represents the probability of occurrence, or frequency, of the associated digital set within the digital signal. While more than one associated indicator remains stored, pairs of the associated indicators are selectively combined and each of the selectively combined pairs of associated indicators are accumulated to determine the initial Huffman Coding rate. The initial Huffman Coding rate is used to compress the digital signal.

Abstract: A method and apparatus for carrying out rapid, block-based SAD search operations for facial ellipses in a CIF videophone image frame are disclosed. A set of search templates, each having an ellipse pattern with two concentric, contiguous perimeters is defined and a set of parameter values are calculated off line for each template: a predetermined subfactor, index number, number of pixels in its dithered perimeter pattern, and first and second match thresholds. The pixels in the lower portion of each perimeter in the pattern are thinned by dithering so as to emphasize the upper contour of the ellipse. Values of +2k for interior perimeter pixels and -2k for exterior pixels in the template are then added to corresponding +k edge pixels and -k non-edge pixels in each search position of the template on a thresholded binary edge map of the image frame.

Abstract: A method and apparatus for providing high-speed data compressing without sacrificing the quality of data reconstruction. Each input vector or block of original data is expressed as a combination of a codebook index and an error differential, or as a compressed version of the original block of data, depending on whether the total number of bits needed to express the input vector as a combination of a codebook index and an error differential is less than the total bits needed to send the compressed version of the original block of data. In one embodiment, the flexibility to express video data in a compressed format or as a combination of a codebook index plus an error differential is provided through a video system employing a codebook, a scalar quantizer, and an entropy coder.

Abstract: A method and apparatus for coding an image comprising (at least) two regions (e.g., a facial region and a background region) which are to be coded with different quantization error parameters (e.g., quantizer step sizes), wherein the respective quantization error parameters are determined with use of a feed-forward rate control technique. Initial quantization error parameters are assigned to each region, and the overall bit rate which would result for the coding of the given frame is computed based on these assigned quantization error parameters. The computed bit rate is compared to a given bit rate constraint which may, for example, represent a limitation of a transmission channel. Based on the result of this comparison, one or both of the assigned quantization error parameters are adjusted, thereby resulting in different quantization error parameters for the two regions.

Abstract: Apparatus and methods are provided for generating a Huffman Code for use in compressing a received digital signal. The digital signal includes a plurality of digital sets wherein ones of the digital sets are non-unique. Ones of the digital sets are stored. Each stored digital set has associated therewith a codeword and an indicator. The indicator represents a probability of occurrence, or frequency, of the stored digital set within the digital signal. While more than one associated indicator remains stored, pairs of associated indicators are selectively combined and a first digital set associated with a first indicator and a second digital set associated with a second indicator are both associated with the selectively combined indicator. A first binary value is appended to the codeword associated with the first digital set and a second binary value is appended to the codeword associated with the second digital set.