Software-only multiple variable length decoding for real-time video on MDSP

We present the multiple variable length decode algorithm implemented in most video applications on MDSP. In our implementations we were able to decode multiple symbols per cycle. The implementation is efficient and is targeted towards memory constrained embedded systems. We have confirmed this algorithm in our implementations of H261/3, MPEG2/4 and achieved multifold speedup improvements against algorithms which can decode at the symbol rate only. This limits the decoding throughput capability of these algorithms. Most parallel decoding approaches use the length of the first codeword to detect the second codeword in parallel. By a single table lookup operation we detect multiple codewords without any detection mechanism.