Improved HEVC lossless compression using two-stage coding with sub-frame level optimal quantization values

Lossless video coding is used when perfect preservation of video data is required. In HEVC, lossless coding is accomplished by bypassing the transform and quantization stages. Prediction residuals are coded with the entropy coder in the spatial domain. In this paper, two-stage coding with sub-frame adaptive quantization is proposed. The DCT is firstly applied to the prediction residuals and the DCT coefficients are quantized. The quantized DCT coefficients and the quantization error are coded. Adaptive quantization parameters are used for each Coding Unit. Simulation results show that the proposed method significantly outperforms the HEVC lossless coding.