This paper focuses on the bidirectional motion estimation problem for videoconferencing applications at very low bit rate. The missed frames are predicted by the decoder using only the transmitted frames with no additional information. The proposed approach is based on spatio-temporal interpolation. On each of the two selected reference frames, the same chosen moving objects are meshed using deformable block quad-tree decomposition. The positions of the mesh nodes are related to the content of the objects in such a way that the quadratic spatial reconstruction error of the objects is as small as possible. From these nodes, a temporal cubic spline interpolation predicts the mesh nodes of the moving object in the missed frame reconstructing then the meshed object. The proposed approach is integrated in the H.264/AVC video coding standard. Simulation results present the performances of the proposed bidirectional motion estimation, at very low bit rate.