Motion-compensated transform coding of video using adaptive displacement fields

To find good trade-offs between the rate-distortion efficiency of motion-co mpensated discrete-cosine-transform video coding and its computational comp lexity, we explore a scheme which uses an adaptive displacement vector fiel d for motion compensation. The sampling density of the field is nonuniform and is adapted to the image scene using a Lagrangian optimization algorithm . The algorithm is formulated to minimize an overall distortion for a given bit rate constraint on the video frame. The algorithm takes into account t he contributions to the overall bit rate and distortion due to motion vecto r and prediction residual coding. Our simulation results demonstrate that f or various common video sequences, the proposed scheme outperforms a popula r H.263 test model by about 0.5 dB of peak signal-to-noise ratio. Significa nt reduction in coding artifacts is observed and visual quality improvement is highly palpable. The work demonstrates that a suitably crafted rate-dis tortion optimization scheme can improve performance without exacerbating co mplexity. (C) 1998 SPIE and IS&T. [S1017-9909(98)00703-X].