In image/video coding standards, the zigzag scan provides an effective encoding order of the quantized transform coefficients such that the quantized coefficients can be arranged statistically from large to small magnitudes. Generally, the optimal scan should transfer the 2-D transform coefficients into 1-D data in descending order of their average power levels. With the optimal scan order, we can achieve more efficient variable length coding. In H.264 advanced video coding (AVC), the residuals resulting from various intramode predictions have different statistical characteristics. After analyzing the transformed residuals, we propose an adaptive scan order scheme, which optimally matches up with intraprediction mode, to further improve the efficiency of intracoding. Simulation results show that the proposed adaptive scan scheme can improve the context-adaptive variable length coding to achieve better rate-distortion performance for the H.264/AVC video coder without the increase of computation.
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