An MPEG encoder compresses moving pictures into I-, P-, and B-frames, where the most important I-frames generate traffic with the highest bit rate. For MPEG videos transmitted over ATM networks, invalid cells are discarded by a usage parameter control scheme at the user network interface and thus cause error propagation in both spatial and temporal domains. For spatial error propagation, the effect of a lost cell depends on the position located in a slice: the farther the position is, the lesser affected are the data. Besides, lost data near the edge of a screen is more tolerable than those at the central part. In order to improve the quality of the received video, we propose two methods to impute the violation of non-conforming cells to others located at a less important position of the same slice. Simulation results reveal that the quality is improved based on both PSNR and subjective visual feeling. (C) 1999 Elsevier Science B.V. All rights reserved.
