An entropy coding system for digital HDTV applications

Run-length coding (RLC) and variable-length coding (VLC) are widely used techniques for lossless data compression. A high-speed entropy coding system using these two techniques is considered for digital high definition television (HDTV) applications. Traditionally, VLC decoding is implemented through a tree-searching algorithm as the input bits are received serially. For HDTV applications, it is very difficult to implement a real-time VLC decoder of this kind due to the very high data rate required. A parallel structured VLC decoder which decodes each codeword in one clock cycle regardless of its length is introduced. The required clock rate of the decoder is thus lower, and parallel processing architectures become easy to adopt in the entropy coding system. The parallel entropy coder and decoder are designed for implementation in two experimental prototype chips which are designed to encode and decode more than 52 million samples/s. Some related system issues, such as the synchronization of variable-length codewords and error concealment, are also discussed.