Mid Sweden University

We propose a coding algorithm called unary prefixed Huffman (UPH) coding for a family of infinite sources called quantized generalized Gaussian (GG) sources. Compared with the existing codes for these GG sources, the UPH algorithm provides a more adaptive approach, and its coding efficiency is upper bounded by entropy +2.

A unary-prefixed encoding (UPE) algorithm for coding the lengths of zeros in a bit vector is proposed. While the lengths of consecutive zeros in a bit vector can be mapped to integer sources with a geometrical distribution (when the bits in the bit vector are independent of each other), the actual case, in a real-world situation, is more often that the distributions are exponential, with high peaks and heavier tails (when the bits in a bit vector are correlated). For the geometric distribution, the UPE code set can be proven to be optimal. For integer sources with high peaks and heavier tails, the UPE almost always provides better compression compared to existing suboptimal codes.

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 25% in speed, decreases 41% in size, and consumes 45% power of the PLS decoder.

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 new coding method under the name "Alternating Coding" (ALT coding) and apply it to the UVLC The ALT coded UVLC yields the same high coding efficiency as the original UVLC, but ALT coding also enables immediate decoding, immediate error detection and location in a UVLC packet. It improves the error resiliency and error robustness of the UVLC packet by applying an "error speculation". Results show that the ALT coded UVLC packet always outperforms the original UVLC packet in terms of error resiliency and robustness. Moreover the simple pattern of ALT coded UVLC can greatly simplify the UVLC decoder architecture and therefore enables small, fast, and low-power decoder design.

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 develop an efficient decoder for UVLC by utilizing the special properties of UVLC which perform coding in an alternating way (ALT). We compare the ALT decoder with the decoder called "VLC decoder using plane separation" (PLS) which is claimed to be one of the most effective VLC decoders. Our results show that the ALT decoder is 1.34 times faster, 1.7 times smaller, and consumes 45% power in comparison to the PLS decoder

The authors develop a class of codes for quantised generalised Gaussian (GG) sources. This new class of codes, that are called hybrid Golomb (HG) codes, are hybrids of Golomb-Rice (GR) codes and exp-Golomb (EG) codes. They integrate the properties of both GR and EG codes, which makes their performance more robust under variable source parameters. The efficiencies of the three classes of codes are compared and it is shown that the set of HG codes have efficiencies of approximately 70% or greater for a wide range of parameter values, whereas GR and EG codes can have efficiencies lower than 20%. The efficiencies of the set of HG codes are also compared with the set of EG codes that have the best performance under parameter scaling. It is shown that. this set of HG codes still achieve a higher efficiency.