Design and Implementation of Robust Mode Decision Algorithms for Video Transmission over Lossy Networks
Date Issued
2011
Date
2011
Author(s)
Yang, Ya-Lun
Abstract
Video quality suffers from significant degradation when transmitted over lossy networks, where a widely accepted technique is rate-distortion optimized mode decision for error resilience coding. However, the estimation of end-to-end distortion introduces noticeable computing complexity. In addition, the search for the optimal mode among all possible modes also takes a lot of encoding time in a general video encoder. The complexity due to the two problems therefore makes it difficult to achieve robust video streaming for real-time transmission over lossy networks. Although some heuristic methods have been developed to reduce complexity, they have been designed for coping with one of the above reasons alone without consideration of each other. To address the issue, in this thesis we design a complexity-reduction algorithm which can solve the above problems to achieve robust mode decision. First, we construct a unified end-to-end distortion model and then apply it in a rate-distortion optimized framework. Through result analysis, we demonstrate that such a framework can indeed perform robust mode decision and a significant proportion of MBs are encoded as SKIP mode for all loss conditions. By using this characteristic and some factors of robust mode decision as decision criterion, we develop an algorithm which can determine the modes of possible MBs into SKIP mode before real encoding process. In addition, the algorithm reduces the time of estimation for end-to-end distortion by modifying coding structure into MB-level and calculating only for non-SKIP MBs. Finally, we implement this algorithm into XviD codec to demonstrate the practicality. Experimental results show that the proposed algorithm can reduce coding complexity up to 37% while maintaining similar average picture quality in comparison with the conventional rate-distortion framework for robust mode decision.
Subjects
Video coding
Mode selection
Type
thesis
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