A coding method for UVLC targeting efficient decoder architecture

Variable length code (VLC) is used in a large variety of lossless compression applications. A specially designed VLC, called "universal variable length code" (UVLC), is utilized in the latest video coding standard H.26L under development. In this work we propose a coding method that we call "alternating coding" (ALT coding) for UVLC. An efficient UVLC decoder is designed (ALT decoder) on the basis of it. ALT coding facilitates a much easier decoding scheme for UVLC. It frees the decoder from codeword tables and the sizes of the barrel shifters are reduced. The codeword tables and barrel shifters usually occupy the largest portion of the area in the traditional VLC decoders and they are also performance limiting in terms of speed and power consumption. We compare the ALT decoder with one of the most efficient VLC decoders called "VLC decoder using plane separation" (PLS). Our results show that the ALT decoder increases 257% in speed, decreases 41% in size, and consumes 45% power of the PLS decoder.