Motion-adaptive modelling of scene content for very low bit rate model-assisted coding of video sequences

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., using different quantization levels), such that if the identified region contains, for example, a person's face, the quality of the coding of the face may be improved relative to the quality of the coding of other portions of the image.

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