Design and Verification of H.264 Context Adaptive Variable Length Decoder

• Main Authors: Shengta-Ta Jiang, 江昇達
• Other Authors: Gwo Giun Lee
• Format: Others
• Language: en_US
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/54145441497172911877

碩士 === 國立成功大學 === 電機工程學系碩博士班 === 93 === 　Entropy coding is one of the most popular lossless compress techniques. Recently, the newest compression standard, H.264, was proposed a context-adaptive variable length coding (CAVLC) for entropy coding. The CAVLC is different from conventional variable length coding. It uses the spatial correlation of images to increase the ompression performance of entropy coding. But it also increases the complexity of the Context-Adaptive Variable Length Decoder (CAVLD). 　Here we tried to implement the CAVLD by hardware, and it can support the real-time decompression for standard definition. The CAVLD’s decoding unit is a 4x4 block, and it has a specific decoding flow. There are five types of symbols defined in CAVLD decoding flow and these symbols have data dependency. Our aim is to design a faster CAVLD, so we tried to reduce the critical path of CAVLD to raise its speed, and let those steps which are not on the critical path to decode two symbols per cycle to increase the throughput. The implement result showed that the proposed CAVLD can operate at 120 MHz based on the UMC 0.18 µm CMOS technology. Its input data rata is 32bits/cycle, and output data rata is 0.4pixel/cycle. The proposed CAVLD can support the H.264/MPEG-4 AVC decoding in baseline profile level 3.1. 　The other major point of design CAVLD is verification. In the decoding flow, there are too many different combinations. While only several sequences were used for testing it, the confidence of the proposed CAVLD was not enough. So a verification plan was designed to test the CAVLD to get higher confidence. This plan included compliance testing, corner case testing, random testing and real code testing. Finally, we did the verification on a software-hardware co-simulation platform to ensure it can work correctly on an AMBA system.