Research And Optimization On H.264 Intra Prediction Algorithm Based On Fourier Spectrum

ITU-T H.264/MPEG-4 Part 10 AVC(H.264 standard for short) is established by Joint Video Team(JVT) consisting of experts from ISO/IEC Moving Picture Experts Group(MPEG) and ITU-T Video Coding Experts Group(VCEG) and is formlly put out in 2003.As the newest generation of video coding standard,H.264 standard introduces a large number of advanced video coding technology and new ideas.That makes it have much higher coding efficiency,better video quality,network friendship and fault tolerant character.And that also brings it great computation complexity,which limits its application area,such as in real time communication application or in some embedded systems.Aiming at the status quo,many researches have been done and being done to decrease compute complexity and together improve running efficiency while keeping high image quality.Firstly,the paper briefly introduces the principle and method of video coding technology and then does a general introduction and comparative analysis on the current two video coding serial standards(H.26X and MPEG-X).Next it takes H.264 video coding international standard as the researching object,simply introduces its birth and development,video codec architecture and main technical characteristics.Especially it studies H.264 intra prediction technology in depth,including a variety of intra coding modes,full search mode selection algorithm and its complexity.And H.264 intra prediction technology is compared to still image coding standard JPEG/JPEG2000 in coding performance.In order to solve the problem that there are many prediction modes and high computional complexity in H.264 intra prediction,this paper mainly studies the fast mode selection algorithm of H.264 intra prediction and proposes a fast intra prediction algorithm based on Fourier spectrum.The major works are as follow:(1) Fourier spectrum wedge and ring feature is introduced to judge the flatness and texture direction of a macroblock and is combined with H.264 intra predition algorithm,thus the intra prediction mode selection process is accelearated.(2) Fourier spectrum ring feature is adopted to describe the flatness of a macroblock. The macroblock having rich detail is directily coding with Intra₄×4,so the Intra₁6×16 coding method is skipped and the amount of computation is reduced.(3) In order to accelerate the process of Intra₄×4 mode selection,Fourier spectrum ring feature is adopted to describe the texture direction of a macroblock and preclude the prediction modes inconsistent with the texture direction.According to an analysis,texture direction of a macroblock is always similar to its sub block.So Fourier spectrum ring feature of a macroblock can be used to determine the texture direction of its all 4×4 sub blocks,and the modes consistent with texture direction are the candidate prediction modes.Thus the Fourier transform of each 4×4 block is avoided and the computational amount of Intra₄×4 mode selections is reduced.(4) Fourier transform adopts fast algorithm to reduce its computational amount.And in this paper the Fourier transform is only for 16×16 size maeroblock.According to this feature, some coefficients can be set as constants to further accelerate computational speed.To testify the performance of the proposed fast algorithm,we adopt H.264 testing model JM10.1 experiment platform and comparison is made between the H.264 full search algorithm and this fast one.Experimental results show that the proposed fast algorithm greatly improves the coding speed while maintaining image quality and bit rate.