Abstract: A method for optimizing a wavelet packet structure for subsequent tree-structured coding which preserves coherent spatial relationships between parent coefficients and their respective four offspring at each step. A valid frequency tree is defined by a wavelet packet decomposition algorithm. Constraints are placed on the pruning of the frequency tree in order to select valid frequency trees as each step. These constraints include considering any four offspring sub-bands as candidates for pruning only when their current frequency decomposition level is the same as that of their respective spatially co-located parent sub-band, and pruning the spatially co-located offspring sub-bands when pruning only the parents results in an invalid wavelet packet structure.

Abstract: A method of encoding a video sequence including a sequence of video images includes first comparing elements of a portion of a first video image (e.g., pixels of a macroblock of a current frame) with elements of a portion of a second video image (e.g., corresponding pixels of a macroblock of a previous frame) to generate respective intensity difference values for the element comparisons. Then, a first value (e.g., one) is assigned to the intensity difference values that are above a visually perceptible threshold value and a second value (e.g., zero) is assigned to the intensity difference values that are at or below the visually perceptible threshold value. Next, the method includes summing the first and second values to generate a sum. If the sum is greater than a predetermined decision value, the portion of the first video image is encoded (e.g., motion compensated). The method is fully compatible and, thus, may be implemented with video standards such as, for example, H.261, H.

Abstract: An adaptive postfiltering arrangement for decoding video images is disclosed wherein the postfilter parameters used to control the strength of the postfilter are computed by the encoder at the time the video images are encoded and are transmitted to the postfilter as side information contained in the video image bitstream. The postfilter removes distortions from decoded video images, derived as a result of DCT coefficient quantization errors produced when the image is compressed for transmission to a decoder, and is based on computation of signal-to-noise ratios (SNRs), of one or more components of encoded video images. Other information about image content, such as face location information, can also be included in the side information sent to the postfilter in the video image bitstream, to modulate the postfilter strength according to the image content.

Abstract: A new method for real time implementation of rate-distortion optimized coding mode selection is disclosed that can be efficiently applied to H-263-compatible video codecs and other codecs of similar type. A normalized rate-distortion model is used to efficiently compute the rate and the distortion when encoding motion-compensated prediction error signals, instead of performing DCT, quantization and entropy-encoding. A fast algorithm is also disclosed that determines sub-optimal values of coding parameters such as the quantization parameter and the Lagrangian multiplier, .lambda., for the trellis search. Very good rate control and picture quality are achieved, especially when the disclosed techniques are applied in very low bitrate video coding.

Abstract: An apparatus responds to a video signal representing a succession of frames, where at least one of the frames corresponds to an image of an object, to detect at least a region of the object. The apparatus includes a processor for processing the video signal to detect at least the region of the object characterized by at least a portion of a closed curve and to generate a plurality of parameters associated with the closed curve for use in coding the video signal.

Abstract: A method and apparatus for video coding whereby a region of an image which includes a predetermined object such as a person's face in the foreground portion of the image is automatically determined. Specifically, the foreground portion of the image is identified, and one or more predetermined (geometric) shapes (e.g., ellipses) are compared with the shapes of objects found in the foreground portion of the image. The foreground portion of an image may be determined by performing a global motion estimation of the overall image to detect global image movement resulting, for example, from camera pan and zoom. That portion of the image whose movement is consistent with the estimated global motion may be identified as the background portion, with the remainder of the image identified as the foreground portion. The identified region of the image which includes the predetermined object and portions of the image which do not include the predetermined object may be coded with differing levels of coding accuracy (e.g.

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.