Adaptive Golomb Codes For Level Binarization In The H.264/AVC FRExt Lossless Mode

Fidelity Range Extensions (FRExt) is an H.264/AVC amendment which provides enhanced coding tools and the possibility to perform high resolution and lossless video encoding. However, most of the efforts for lossless coding in the H.264/AVC framework have been concentrated on improving the prediction step while leaving the entropy coder; CABAC, originally designed for lossy coding, unaltered. However, if transformation and quantization of the corresponding coefficients are not performed, as is the case of the lossless coding mode for FRExt, CABAC becomes sub-optimal. In this paper we show how considerable improvements in compression ratios can be achieved with simple modifications of the CABAC engine. The proposed technique was tested on a set of 4:4:4 test sequences, achieving gains of up to 12.80% with respect to the original unmodified H.264/AVC algorithm.