1. A method for encoding video, comprising: determining early termination based on the value of a sum of absolute difference (SAD 0 ) by a processor, comprising enabling early termination if SAD 0 is less than or equal to a threshold (THRESHOLD); performing motion prediction using a motion vector from a previous frame as a prediction point by the processor; using the prediction point as the center to obtain the integral motion vector by conducting a 3×3 cross searching until a minimum sum of absolute difference (minSAD) is located at the center of the cross; and predicting a location of a half-pixel point based upon a point corresponding to the integral motion vector, values of the minimum sum of absolute difference of other four cross points, wherein THRESHOLD=−500+MAP(QP)×256, and wherein MAP(QP) has the following values: QP 1-7 8-11 12-15 MAP(QP) 4 5 6.