1. A method for determining a prediction mode for performing intra prediction of a 16×16 macro-block, the method comprising: determining a cost associated with each of a DC prediction mode, a V-prediction mode, an H-prediction mode and a plane prediction mode for predicting the 16×16 macro-block and choosing a mode having the lowest cost as a first mode; determining costs associated with one or more modes for each 4×4 sub-macroblocks of the 16×16 macro-block and choosing a mode having the lowest cost as a second mode for each 4×4 sub-macroblocks; computing a cumulative of the lowest costs and comparing the cumulative of the lowest costs with the cost associated with the first mode; choosing the mode with the lower cost among the cumulative cost and the cost associated with the first mode for performing intra prediction of the 16×16 macro-block, wherein, determining the second mode for each of the 4×4 sub-macroblocks of the 16×16 macro-block comprises: calculating a cost associated with DC prediction mode, H-prediction mode, and V-prediction mode; in response to a cost associated with the DC prediction mode is less than the cost associated with the H-prediction mode and the cost associated with the V-prediction mode, calculating a cost associated with each directional mode and associated diagonal directional modes for both H-prediction mode and the V-prediction modes and choosing the mode with minimum cost associated with it as the second mode; instead of selecting the mode with a lower cost between H-prediction mode and V-prediction mode; calculating a cost associated with each directional mode associated with the selected mode; in response to the cost associated with the selected mode being less than the cost associated with the directional modes associated with the selected mode, selecting the selected mode as the second mode instead of calculating cost associated with each diagonal directional mode, and comparing the calculated cost with the cost associated with the directional modes; and selecting the mode with least cost, as the second mode.