Abstract: A sprite generation method used in video coding generates a sprite from the video objects in the frames of a video sequence. The method estimates the motion between a video object in a current frame and a sprite constructed from video objects for previous frames. Specifically, the method computes motion coefficients of a 2D transform that minimizes the intensity errors between pixels in the video object and corresponding pixels inside the sprite. The method uses the motion coefficients from the previous frame as a starting point to minimizing the intensity errors. After estimating the motion parameters for an object in the current frame, the method transforms the video object to the coordinate system of the sprite. The method blends the warped pixels of the video object with the pixels at corresponding positions in the sprite using rounding average such that each video object in the video sequence provides substantially the same contribution to the sprite.

Abstract: To represent the motion of a pixel between successive image frames, this method utilizes the motion information for the transformation block containing the pixel, as well as the motion information for adjacent transformation blocks whenever the adjacent transformation blocks are associated with the same object with which the selected pixel is associated. As a result, transformation errors arising from transformation block discontinuities are decreased and the accuracy and integrity of motion representations of pixels within an object are maintained. Preferably, the motion representations for the transformation blocks are multi-dimensional or affine transformations that are capable of representing complex motions that include any or all of translation, rotation, magnification, and shear.

Abstract: A transformation method provides a multi-dimensional affine transformation for representing motion between corresponding image components of successive video image frames. The multi-dimensional affine transformations can represent complex motion that includes any or all of translation, rotation, magnification, and shear. The transformation method of this invention includes determining motion transformations between corresponding pixels in the image components of the first and second video image frames. From the motion transformations between corresponding pixels, multi-dimensional affine motion transformations between the corresponding image components are determined. This transformation method increases the accuracy with which complex motion is represented and results in fewer compression or encoding errors in comparison to conventional methods, thereby increasing compression efficiency.

Abstract: A video compression encoding process compresses or encodes dense motion vector fields to provide and improved compression ratio. In accordance with this method, a dense motion vector field is obtained for an object or a portion of an object between a pair of video image frames. The dense motion vector field may correspond, for example, to an object or other image portion of arbitrary configuration or size. The configuration of the dense motion vector field is extrapolated to a regular, preferably rectangular, configuration to facilitate encoding or compression. The dense motion vector field with its extrapolated regular configuration is encoded or compressed according to conventional encoding transformations such as, for example, discrete cosine transformation (DCT) or lattice wavelet compression.

Abstract: A precompression extrapolation method extrapolates image features of arbitrary configuration to a predefined configuration to facilitate compression of the image features. This extrapolation method allows compression of arbitrary image features to be performed in a conventional manner, such as discrete cosine transform or lattice wavelet compression. This method includes defining an extrapolation block boundary about an object or image feature that is bounded by a feature boundary. Pixels within the block, but not included in the image feature, are identified as non-feature pixels. The feature pixels in the feature boundary include pixel values that correspond to the image characteristics of the pixels. The non-feature pixels adjacent the pixels of the feature boundary are assigned pixel values that include the pixel values of the adjacent feature boundary pixels.

Abstract: A hierarchical object encoding technique or process capable of representing general binary arbitrary shapes that include, for example, embedded or disconnected components. The method decomposes successive layers of general binary arbitrary shapes into simple arbitrary shapes. Each mask formed in this manner is a simple arbitrary shape having only a continuous outer boundary. Accordingly, each outer boundary is encoded, preferably by a contour encoding method, to provide accurate encoding of general binary shapes.

Abstract: Video coding efficiency for high motion scenes is improved by adaptively disabling a parameter indicating whether texture and motion data is coded for a macroblock. The COD parameter is disabled when the number of macroblocks with substantially all zero motion and texture data is less than a threshold number. This reduces the number of bits required to code an interframe video image in a video sequence with high motion and large changes from frame to frame. The coded block pattern for chrominance is also used to determine how to perform entropy coding for the coded block pattern for luminance. In interframe blocks, if the chrominance blocks are coded, it is likely that the luminance blocks will be coded as well. The coded block pattern for chrominance, therefore, is used to select the appropriate entropy coding table for the coded block pattern for luminance.

Abstract: A transformation block optimization method provides transformation blocks of variable size for video compression processes. The method includes defining a transformation block of multiple pixels in an image frame and determining a peak signal-to-noise ratio for the transformation block. The transformation block is tentatively subdivided into subcomponents for which a signal-to-noise ratio is also obtained. The subcomponents are adopted as transformation blocks whenever the signal-to-noise ratios of the subcomponents are greater than the signal-to-noise ratio of the transformation block by more than a predetermined threshold.

Abstract: Sprite-defined objects are completely defined throughout the video sequence as of their first appearance by a "sprite" and one or more trajectories. The sprite includes all the image characteristics of an object throughout the video sequence, and one or more trajectories warp or transform the sprite to represent the object in each frame of the video sequence. The sprite-defined object or objects are a subset of the general objects in the general video sequence and have available more information when they first appear in a video sequence than general objects. A simplified compression method allows the additional information available for sprite-defined objects to be utilized more efficiently than the additional information would be by encoder and decoder processes for general objects.

Abstract: A hierarchical object encoding technique or process capable of representing general binary arbitrary shapes that include, for example, embedded or disconnected components. The method decomposes successive layers of general binary arbitrary shapes into simple arbitrary shapes. Each mask formed in this manner is a simple arbitrary shape having only a continuous outer boundary. Accordingly, each outer boundary is encoded, preferably by a contour encoding method, to provide accurate encoding of general binary shapes.

Abstract: A method implemented in an object-based video encoder or decoder uses shape information that describes the boundary of a group of pixels representing an object in a sequence of video frames to identify transparent blocks (e.g., macroblocks or blocks so that coding/decoding of these blocks can be skipped. In the object-based video coding method, encoders code shape separately from motion and texture, and shape information is available before the encoder/decoder codes/decodes texture and motion data. The encoder and decoder use this shape information to identify transparent macroblocks or blocks so that texture coding and possible motion coding can be skipped. This method for transparent block skipping reduces coding and decoding operations and reduces the number of bits needed to store a bitstream representing a compressed video sequence.

Abstract: Motion estimation plays a very important role in a video compression scheme. It is well known that in a video compression scheme, there exists a high temporal correlation between consecutive video image frames. However, it is difficult to do motion estimation for newly exposed objects, since there is no temporal information and thus, the error signal generated by newly exposed object is large. A method of unrestricted motion estimation is used to take advantage of spatial correlation between the pixels of a newly exposed object. Using unrestricted motion estimation, a newly exposed reference object is padded and expanded with virtual pixels which have the same characteristics of the portion of the object which is newly exposed. The padded object is used to determine the error signal. The error signals produced by using unrestricted motion estimation are significantly smaller, reducing the error signal by up to between 5% and 10%.