Locally adaptive passive error concealment for wavelet coded video


In lossy packet networks such as the Internet, information often gets lost due to, e.g., network congestion. While these problems are typically solved by Active Error Concealment techniques such as error correcting codes, they do not always work for applications such as real time video. In these cases, Passive Error Concealment is essential. Passive error concealment exploits the redundancy in the video: lost data are estimated from their correctly received neighboring data. In this paper, we focus on wavelet based video coding. We compress video frames by dispersively spreading neighboring wavelet coefficients over different packets, and by coding these packets independently from each other. If a packet gets lost during the transmission, we estimate the missing data (wavelet coefficients in I-frames and P-frames, and motion vectors) with passive error concealment techniques. In the proposed method, we extend our earlier image concealment method to video. This technique applies a locally adaptive interpolation for the reconstruction of lost coefficients in the I-frames of wavelet coded video. We also investigate how the lost coefficients in P-frames can be reconstructed. For the reconstruction of lost motion vectors, we use the vector median filtering reconstruction technique. Compared to related video reconstruction methods of similar complexity, the proposed scheme estimates the lost data much better. The reconstructed video also looks better. As the proposed method is fast and of low complexity, it is widely usable.