Fast High Complexity Intra Prediction Mode Decision Algorithm In H.264

H.264 is the newest video coding standard, supporting many kinds of applications that from wireless migration video communication which has the low band width and high error rate to video broadcast, which has the high code rate and the low detention, and in the filamental flow media and so on. Comparing with the old video coding standard H.261, H.263 and MPEG-1, MPEG-2, MPEG-4, H.264 has used many new code characteristic, such as multiple reference Picture, multi-size code block pattern, quarter-pixel accuracy for motion vector, integer transformation, loop filter deblocking. Under the same decoding picture quality, it can reduce the code rate to the half.H.264 has joined many new elements, with the outstanding compression performance and the good network endophilicity, but high coding complexity and large time, which serious block the development of the real-time video service. Therefore, making the research improvement according to the actual need to the video coding algorithm, has the important theory and the practical value.Intra mode decision algorithm is one of H.264 video coding key technologies, using the RDO technology, and choosing the best mode from two intra blocks and chroma blocks, needs to experience a series of consuming time operations, and enormously increases the coding time. Optimized intra mode decision algorithm, can effectively reduce I frame coding time, which makes contribution to the entire coding time to have the important influence.First, the principle and key technologies of H.264 were introduced. Next, intra prediction mode decision algorithm was conducted the thorough research, and the fast algorithm was proposed. The best mode was choosed using the SATD cost function in the chroma mode decision. Intra4x4 block also using the SATD cost function, reduced 9 modes to 3 or 4 modes, then using the RDO cost function to choose the best mode from the candidate modes, and then withdrawing ahead of time when needed. The experimental result indicated that, the optimized algorithm reduced coding time to about 78% compared with that of the original high complexity algorithm in I frame coding, and the PSNR and the coding rate changed little, with important theoretical and practical value.