Research On Intra Prediction And All-zero Block Detection Algorithms In H.264 Coding Standard

H.264 is a new generation digital video encoding standard developed by Joint Video Team(JVT), it has received widely attention since it was published. Because of adopting some new technology, such as new ways of intra prediction and integral transform, multiple reference frames and etc, the encoding function and compression efficiency of H.264 has greatly improved compared with the previous ones. Meanwhile, it brings more complex algorithm and longer time of encoding. In order to meet the requirement of real-time encoding, the algorithm of H.264 standard needs to be streamlined and improved, so that we can raise the encoding rate under the situation that has no influence to the image quality of encoding.This paper outlines the background of coding and the history of video standard firstly, and gives an illustration of the encoding and decoding framework of H.264 and the key techniques it adopts. Then, it proposes two algorithms for encoding process, one is a fast intra prediction algorithm based on detecting pixels'direction of the image and the other is a new algorithm for detecting all-zero block based on the sum of absolute differences, which effectively optimize the encoding process of H.264.Intra prediction as the core component of H.264 standard, is an important way to reduce space redundancy of image, which provides prediction of 4 modes of luma and chroma for 16x16 block as well as 9 modes of luma for 4x4 sub-block, consuming a large amount of encoding time. Through the analysis and research of pixels space correlation in image and calculation and process of pixels variation value, the mentioned modes above can be reduced to 4 and 2 types respectively. The result of the simulation which is done by software informs that:this algorithm can save more than 60% encoding time than standard one, while the loss of image quality it causes can be ignored.On the other hand, a large quantity of all-zero blocks generate after quantization during the encoding process of H.264. This paper further analyses the feature of the coefficients of the 4x4 residual block after transformation, on which basis a new algorithm for predicting all-zero block was proposed, and then got a new Hybrid algorithm to detect all-zero block after connecting to Gaussian detection model. So that we can pick out a greater number of all-zero blocks to avoid transformation, quantification and other operations, and reduce the algorithm complexity as well. Simulation result shows that the highest prediction rate of this algorithm can reach 95.1%, while the decreased value of PSNR is lower than 0.2dB, compared to the other algorithms mentioned in this paper,Finally, this paper makes hardware simulation to the intra prediction process in H.264, based on FPGA. The theoretical analysis and design are made to each sub-module of overall structure designed, as well as functional simulations. At last the paper takes the test sequence as an example, gives a comparison figure between reconstruction frame coded by this design and original frame. Simulation result shows that the system-level design is correct.