A mode decision system and method for motion vector fine search. Each macroblock in a frame has a pre-determined clock number. The system includes a first subtractor, an operation level generator and a determinator. The first subtractor has a first input terminal to receive a clock number and a second input terminal to receive the pre-determined clock number in order to subtract the clock number from the pre-determined clock number and accordingly generate a clock difference. The operation level generator is connected to the first subtractor in order to generate an operation level based on the clock difference. The determinator selects one or more modes in accordance with the operation level and accordingly performs the fine search on the macroblock.
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