An optical flow based motion compensation algorithm for very low bit-rate video coding

We propose an efficient compression algorithm for very low bit-rate video applications. The algorithm is based on (1) optical-flow motion estimation to achieve more accurate motion prediction fields; (2) DCT-coding of the motion vectors from the optical-flow estimation to further reduce the motion overheads; and (3) a region adaptive threshold technique to match optical flow motion prediction and minimize the residual errors. Unlike the classic block-matching based discrete cosine transformation (DCT) video coding schemes in MPEG 1/2 and H.261/3, the proposed algorithm uses optical flow for motion compensation and the DCT is applied to the optical flow field instead of predictive errors. Thresholding techniques are used to treat different regions to complement the optical flow technique and to efficiently code residual data. While maintaining comparable peak signal to noise ratio (PSNR) and computational complexity with that of ITU-T H.263/TMN5, the reconstructed video frames of the proposed coder are free of annoying blocking artifacts, and hence visually much more pleasant.