Embedded quad-tree motion estimation for low bit rate video coding

Low bit rate motion-compensated video codes generally compress their motion descriptions using a fixed scheme. The exact number of bits required to code a given motion field depends on its complexity and the compression scheme used. This approach gives no control over the allocation of bandwidth between the motion component and the residual (clear-up) frame, resulting in a compression scheme whose overall performance is less than optimal. This work describes a method for producing an embedded motion bit stream which can be used to control the proportion of the overall bandwidth dedicated to the motion component. Embedded motion steams, obtained from a number of reference/current frames pairs, are used to investigate the distribution of bits between the motion description and the residual frame. Results show the variation of the optimal bit allocation with different frame pairs and demonstrate the coding advantage obtained from the embedded stream