An encoder for performing motion compensated encoding of a sequence of video frames having picture segments, the encoder comprising: memory means for storing a reference frame; motion field estimation means for estimating picture segment motion in a current frame using at least the reference frame, wherein the motion field estimation means comprises a first motion estimation block and a second motion estimation block, wherein the first motion estimation block uses a series of motion estimation methods of varying complexity and is configured to use predicted motion coefficients previously estimated for at least one first picture segment of the current frame, in the estimation of first motion coefficients for at least one second picture segment of the current frame and wherein the second motion estimation block uses a series of motion estimation methods of varying complexity and is configured to use initial motion coefficients in the estimation of second motion coefficients for said at least one second picture segment of the current frame, said initial motion coefficients being inherited from an earlier motion estimation carried out on a master picture segment the splitting of which created said second picture segment, wherein the first and second motion estimation blocks comprise means for selecting and using a subsequent motion estimation method in the series if a cost function representing a measure of prediction error associated with motion coefficients estimated by a currently selected motion estimation method exceeds a predetermined threshold; and a motion field coding block configured, if both the first motion estimation block and the second motion estimation block are operational and upon receipt of the first and second motion coefficients, to choose either the first or second motion coefficients to be used to represent motion of the second picture segment. memory means for storing a reference frame; motion field estimation means for estimating picture segment motion in a current frame using at least the reference frame, wherein the motion field estimation means comprises a first motion estimation block and a second motion estimation block, wherein the first motion estimation block uses a series of motion estimation methods of varying complexity and is configured to use predicted motion coefficients previously estimated for at least one first picture segment of the current frame, in the estimation of first motion coefficients for at least one second picture segment of the current frame and wherein the second motion estimation block uses a series of motion estimation methods of varying complexity and is configured to use initial motion coefficients in the estimation of second motion coefficients for said at least one second picture segment of the current frame, said initial motion coefficients being inherited from an earlier motion estimation carried out on a master picture segment the splitting of which created said second picture segment, wherein the first and second motion estimation blocks comprise means for selecting and using a subsequent motion estimation method in the series if a cost function representing a measure of prediction error associated with motion coefficients estimated by a currently selected motion estimation method exceeds a predetermined threshold; and a motion field coding block configured, if both the first motion estimation block and the second motion estimation block are operational and upon receipt of the first and second motion coefficients, to choose either the first or second motion coefficients to be used to represent motion of the second picture segment.