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Fast Mode Decision Algorithms for Adaptive GOP Structure in the Scalable Extension of H.264/AVC. Chih -Wei Chiou , Chia -Ming Tsai, and Chia-Wen Lin Dept. of CSIE, Chung Cheng Univ. IEEE Int. Symposium on Circuits and Systems , May 2007. Outline. Introduction
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Fast Mode Decision Algorithms for Adaptive GOP Structure in the Scalable Extension of H.264/AVC Chih-Wei Chiou, Chia-Ming Tsai, and Chia-Wen Lin Dept. of CSIE, Chung Cheng Univ. IEEE Int. Symposium on Circuits and Systems, May 2007
Outline • Introduction • Scalable Video Coding (SVC) • Motion-Compensated Temporal Filtering (MCTF) • Adaptive GOP Structure (AGS) • Feature-based Fast Mode Decision Algorithms for AGS • Feature Selection • Fast Mode Decision Algorithm • Experimental Results • Conclusion
Motivation of SVC • To support clients with diverse capabilities in complexity, bandwidth, power, and display resolution
Scalable Video Coding (SVC) • Scalable video coding methods can adapt in real time to the bandwidth variations over heterogeneous networks and to the terminal capabilities • Partition of video into layers • SNR scalability: Different quantization levels • Spatial scalability: Different picture size • Temporal scalability: Different frame rate
Adaptive GOP Structure (AGS) • Divide a GOP into several sub GOPs by appropriate mode decision • Decreasing the distance between two low-pass pictures
Algorithm for AGS may have unnecessary MCTF operations
Feature-based Fast Mode Decision Algorithms • Goal: extract reliable features from the first MCTF operation with full GOP size to reduce the complexity of AGS • If the selected best GOP mode contains sub-GOPs → this GOP has larger temporal activities → has relatively larger motion vectors and a larger number of intra macroblocks
Features used for mode decision in AGS • Average MV magnitude • Number of intra-coded macroblocks
Experimental Results Scheme 1: use number of intra-coded macroblocks of the high-pass frame at lowest layer of MCTF Scheme 2: use the total number of intra-coded macroblocks from the high-pass frames of all layers of MCTF
Conclusion • Propose a fast GOP mode selection algorithm to reduce the coding complexity for AGS • Select the average MV magnitude and the number of intra-coded macroblocks as features to capture the temporal characteristics of a GOP • The proposed method avoids unnecessary MCTF procedures of sub-GOPs so as to reduce coding complexity