Fast Mode Decision and Encryption Policy in H.264/AVC Frame-skipping Transcoding

H.264/AVC adopts Rate-Distortion Optimization (RDO) techniques to search all the prediction modes supported by standard in turn, then determine the optimal encoding mode which has the minimum rate-distortion cost. Frame-skipping transcoding among heterogeneous networks is a way to lower bitrate transcoding, which can solve incompatibility issues of video stream transmission. Aiming to varied motion problem of the video sequences, this paper introduces a set of adaptive threshold for inter mode decision, which can make a more correct code judgment of motion characteristics for the macroblock, also can obtain more reliable video quality; Combing the mode information of the skipping frame which can not be recovered, a simple and practicable encryption policy is introduced here, which avoids the shortcomings of traditional encryption algorithm complexity. Experimental results show that the encoding time of the new algorithm is almost the same with that of the referenced algorithm, the peak value SNR increases steadily, so novel scheme guarantees nice video quality; Encryption policy achieves the desired encryption effect and efficiency, and broadens the applications of the video security technology.