Extensive pixel-based fast direction detection algorithm for H.264/AVC intra mode decision

In a H.264/AVC intra-frame encoder, the high-complexity mode decision requires a lot of computations, spends much time in the encoding procedure, and calculates all modes to select the best one that achieves the minimum rate-distortion (RD) cost value. The complicated computations for the mode decision cause the difficulty in real-time applications. In this paper, we propose a fast and efficient algorithm to predict all direction modes except for the DC mode, and the pixel direction differences are computed for the fast decision. By the method, we choose fewer high-potential direction modes and send them to the mode decision to calculate the RD cost, and the computational time will be reduced. Simulation results show that the proposed algorithm reduces the encoding time by 62%, and requires bitrate increase about 2.5% and peak signal-to-noise ratio (PSNR) decrease about 0.07 dB in QCIF and CIF sequences. Our method can achieve almost the same improvement of encoding time saving as the previous method with less PSNR degradation and bit-rate increase.