H.264/AVC provides several advanced features such as improved coding efficiency and error robustness for video storage and transmission. In this paper, to further improve the coding quality for encoding possible scene changes and fast variation sequences, we propose a new adaptive GOP scheme that uses the existing motion vectors and motion residuals. The proposed scheme effectively identifies the H.264/AVC coding core {I, P} frames using a statistical table that improves the coding efficiency for changed scene sequences and different video content variance. Simulation results show that the proposed adaptive GOP scheme can increase PSNR 0.65 dB on average and achieve a 92% correct rate for scene change detection from the original H.264 reference software JM10.1 operated in the fixed GOP size.
Abstract-In H.264 advanced video coding (AVC), variable block size motion estimation plays an important role in compression of interframes. In this paper, we propose a fast inter prediction algorithm based on hierarchical homogeneous detection and cost analysis to select the best mode effectively. For each macroblock, we first detect that whether the macroblock is spatial homogeneous or not. For the non spatial homogeneous macroblock, we then perform the 16x16 motion estimation and examine if the 16x16 block is temporal homogeneous or not. Once the homogeneous macroblock is detected in the above process, the best mode will be chosen as 16x16 mode. For the non-homogeneous macroblock, we then execute 8x8 motion estimation and analyze the cost of 8x8 mode and 16x16 mode for deciding the best inter mode should be 16x16 mode or any other mode. The process for searching the best 8x8 block subtype is similar to the process for macroblocks. Finally, the best inter mode is decided by selecting the inter mode with least cost from the candidate modes. Experimental results show that our proposed algorithm can save about 32~54% computation time without introducing any noticeable performance degradation.
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