Analysis of video quality losses in the homogenous HEVC video transcoding.

This paper presents a detailed, quantitative analysis of video quality losses in a homogeneous HEVC video transcoder together with the analysis of the origin of those quality losses and the influence of quantization step alignment on transcoding. With the use of HM15.0 reference software and a set of test video sequences, the cascaded pixel domain video transcoder (CPDT) concept has been used to gather all the necessary data needed for the analysis. This experiment was performed for a wide range of source and target bitrates. The essential result of the work is an extensive evaluation of CPDT, commonly used as a reference in works on effective video transcoding. So far, no such extensively performed study has been made available. The quality degradation between a transcoded video and a video that would be the result of direct compression of the original video at the same bitrate as the transcoded one has been reported. The dependences between quality degradation caused by transcoding and bitrate changes of the transcoded data stream are clearly presented in graphs.