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In the perceptual coding scheme, the properties of the human visual system (HVS) are usually used to improve the coding efficiency. The frequency sensitivity is one of the most important properties of HVS and is usually used to improve the subjective quality. The frequency weighting technique is adopted in many video coding standards, such as MP EG 2 and H.264/AVC High Profile. However, the frequency weighting algorithms used in those standards are all in picture level. In this paper, a novel macroblock (MB)- level adaptive frequency weighting (MBAFW) algorithm is investigated. Compared with the picture-level adaptive frequency weighting (PAFW) algorithms, the encoder with MBAFW can select different frequency weighting strategies and different quantization matrices for each MB. The spatial context and the motion activities of one picture are both taken into consideration, which makes the frequency weighting adaptation more efficient and reasonable. The experimental results show that MBAFW can improve the subjective quality significantly. Additionally, MBAFW algorithm can achieve 10%~15% bitrate reductions with almost the same subjective quality.