Research In Fast Mode Decision Algorithm For Intra Prediction In H.264Video Coding

H.264/AVC is a new generation of video codec standard proposed by JVT(Joint Video Working Group) set up joinly by ITU-Ts VCEG (Video Coding Experts Group) and ISO/IEC’s MPEG (Moving Picture Coding Experts Group).Compared with the previous video codec standards, it uses some new technologies, such as VLC symbol encoding, integer transform based on block4×4block, layered coding syntax. So that it has many incomparable advantages, such as high compression ratio, excellent image quality, a wide range of applications, strong network adaptable, fault-tolerant capability. But H.264/AVC has its own shortcomings, because its predictive encoding mode selection using the full search algorithm based on the rate-distortion optimization model requires a large amount of computation, a high degree of complexity of the coding algorithm limits its application of the real-time communication system.Aim at problems of large amount of computation for the H.264coding standard predictive encoding mode selection, this paper proposes an intra prediction fast mode selection algorithm based on the Mean Absolute Deviation (MAD). The algorithm makes a comparison between the Mean Absolute Deviation value and two threshold values set up in advance, judging suitable intra predictive encoding type; As for the choice of the prediction mode of the intra4×4block, we use the correlation of adjacent directions of the prediction mode to judge it; As for the intra prediction mode of the16x16macroblock, we also set two threshold values, and use the comparition between macroblock line smoothness or macroblock column smoothness and the threshold values to select the most probable prediction mode. As for prediction mode for the8x8chroma block, we use the correlation between intra16×16brightness prediction mode and intra8x8chroma prediction mode and the characteristics of the8×8DC prediction mode and8×8plain prediction mode to select the most probable prediction mode. Finally, we makes a C language imple mentation of this algorithm in the JM reference model of the H.264standard and a experiment to evaluate the performance of this algorithm with several typical H.264testing video sequences. Experimental results show that:in the same encoding conditions, we compare the intra prediction fast mode selection algorithm based Mean Absolute deviation with the Full Search Algorithm, encoding time savings of nearly70%under the premise of small coding performance loss-the Average Peak Signal to Noise Ratio decreasing only0.18dB, the encoding rate increasing of only2.65%; Compared with several other fast algorithms, our algorithml’s coding performance loss is smaller, but the encoding time of our algorithm saves of10%or more, which fully illustrate the effectiveness of the our algorithm. More importantly, this algorithm only adds some simple arithmetic, all operations are carried out in the range of integers.