Efficient table access for reversible variable-length decoding

A new method for reversible variable-length codes (RVLC) decoding is described, which decreases the amount of table space required, particularly for MPEG-4 video RVLC decoding on a DSP chip. Because of the special structure of RVLC codewords, the decoding techniques that are common for regular VLCs are less efficient when used with RVLCs. The new method does not use the codeword itself to access a lookup table, but instead forms a sort of hash index. This reordering can significantly decrease the amount of memory required by reducing gaps or redundancy in the table entries.