Area-Efficient H.264 VLC Decoder Using Sub-tree Classification

Most video compression standards, such as MPEG-2 and H.264/AVC, use variable length coding (VLC) to remove statistical redundancy. Since the code words have variable length, how to represent the codeword table to reduce storage size is an important issue. A 2-D to 1-D tree translation scheme is proposed to minimize the number of stored bits. However, the throughput is limited by the tree search decoding flow. The VLC tree is then decomposed using sub-tree (ST) classification. The ST classification method not only reduces the amount of storage required for code words but also improves the throughput. The gate count of the proposed H.264/AVC context-based variable length decoder (CAVLD) design is 6.23 K when synthesized at 200 MHz.