To better exploit spatial correlations in a video frame, the High Efficiency Video Coding (HEVC) standard has adopted a great many more intra prediction modes than H.264/AVC. As a result, the complexity of rate-distortion-optimized (RDO) HEVC intra mode selection is very high. Many techniques have been proposed to expedite the intra mode selection process to achieve a better overall tradeoff between complexity and RD performance. In this paper, two novel techniques for adaptive intra mode candidate selection and bidirectional depth search algorithms are utilized to accelerate intra prediction. The proposed techniques show an average of 63% (up to 67%) time saving with only 1% BD-Rate increase, outperforming most of existing intra prediction algorithms.