Error concealment in video transmission over packet networks by a sketch-based approach

The transmission of coded visual information over packet networks introduces fidelity problems related to the loss of frames during transmission. In standard block-based coding, such losses result in a wrong reconstruction of long block sequences, also due to the use of predictive and variable length source coding techniques. In video transmission, artifacts are even more visible due to the temporal propagation caused by prediction and interpolation schemes. In order to reduce the impact of these errors on visual quality, appropriate concealment algorithms should be applied, aimed at minimizing the appearance of block artifacts due to transmission errors. In this paper, a new concealment technique is presented, which aims at restoring the lost visual information by using a synthetic reconstruction of the high-frequency content of the damaged blocks. The method is funded on the theory of sketch-based encoders: for each block to be interpolated, the sketch information of the available surrounding blocks is extracted and propagated to the missing area. Then, the low-pass content is easily interpolated from the sketch. The proposed method uses only the spatial correlation, and has been applied with good results in the transmission of video data over non-reliable packet networks.