The Study And Hardware Design Of Entropy Coding Technology For H.264

H.264 is the newest video coding standard of the ITU-T Video Coding Experts Group and the ISO/IEC Moving Picture Experts Group and is currently one of the hot subjects of image processing technology. Coding quality and compression ratio have been greatly improved in the new standard compared with the previous standards. The context-based adaptive technology is introduced into the new standard, which can be said to be a technology renovation of the video coding. In the paper the study of entropy coding is carried on and designed a Context-based Adaptive Variable-Length entropy coder in hardware method.The main entropy coding technologies of H.264 include Variable-Length Coding (VLC) and Context-based Adaptive Binary Arithmetic Coding (CABAC). Both Exponential-Golomb coding and Context-based Adaptive Variable-Length Coding (CAVLC) are Variable-Length Codings. Exponential-Golomb codes are variable length codes with a regular construction, which can code the symbols in a table. Both CAVLC and CABAC adopt the context-based adaptive technology, the main idea of which is switching the tables independently(variable length coding) or updating symbol conditional probability (arithmetic coding) according to the contents of information in the process of the entropy coding, thereby the coding efficiency is greatly enhanced.Today, the design of the CAVLC encoder is mainly in software method, but with the development of real-time image processing technology, it is difficult for software method to meet the demands. As a result, the hardware method in designing of CAVLC coder becomes a good choice. The hardware architecture of the CAVLC coder in the paper is implemented on an Altera FPGA device, and can process 4x4 or 2x2 blocks per 16 clock periods with pipelined architecture.