OPTICAL FLOW-BASED MOTION COMPENSATION ALGORITHM FOR VERY LOW-BIT-RATE VIDEO CODING

In this article, we propose an efficient compression algorithm for ver y low-bit-rate video applications. The algorithm is based on (a) an op tical-flow motion estimation to achieve more accurate motion predictio n fields; (b) discrete cosine transformation (DCT) coding of the motio n vectors from the optical-flow estimation to reduce the motion overhe ads; and (c) an adaptive threshold technique to match optical flow mot ion prediction and minimize the residual errors. Unlike the classic bl ock-matching based DCT video coding schemes in MPEG-1/2 and H.261/3, t he proposed algorithm uses optical flow for motion compensation and th e DCT is applied to the optical flow field instead of predictive error s. Thresholding techniques are used to treat different regions to comp lement optical flow technique and to efficiently code residual data. W hile maintaining a comparable peak signal-to-noise ratio (PSNR) and co mputational complexity with that of ITU-I H.263/TMN5, the reconstructe d video frames of the proposed coder are free of annoying blocking art ifacts, and hence visually much more pleasant. The computer simulation are conducted to show the feasibility and effectiveness of the algori thm. Results at II kbps are presented which can be used for videophone applications in the existing public switched telephone network (PSTN) . (C) 1998 John Wiley & Sons, Inc. Int J Imaging Syst Techncl, 9, 230- 237, 1998.