Integrated joint source-channel symbol-by-symbol decoding of variable-length codes using 3-D MAP sequence estimation

Abstract

Most of multimedia schemes employ variable-length codes (VLCs) like Huffman code as core components in obtaining high compression rates. However VLC methods are very sensitive to channel noise. The goal of this paper is to salvage as many data from the damaged packets as possible for higher audiovisual quality. This paper proposes an integrated joint source-channel decoder (I-JSCD) at a symbol-level using three-dimensional (3-D) trellis representation for first-order Markov sources encoded with VLC source code and convolutional channel code. This method combines source code and channel code state-spaces and bit-lengths to construct a two-dimensional (2-D) state-space, and then develops a 3-D trellis and a maximum a-posterior (MAP) algorithm to estimate the source sequence symbol by symbol. Experiment results demonstrate that our method results in significant improvement in decoding performance, it can salvage at least half of (50%) data in any channel error rate, and can provide additional error resilience to VLC stream like image, audio, video stream over high error rate links.

Joint source-channel coded multidimensional modulation for variable-length codes

“…In recent years, VLCs are widely used in various image/video coding standards [3][4][5][6][7]. Using VLCs, the symbols that occur more frequently are assigned short code words and those that occur infrequently are assigned long code words.…”