This paper introduces a method for adapting block quantisation parameter values in HEVC video compression based on perceptual coding maps. These maps are computed per block taking into account masking effects. Masking levels are calculated using spatial, temporal and foveation features that are extracted from the video and are stored in a perceptual coding map. The produced map drives a QP adaptation process that aims to redistribute coding bits in the frame so that the perceived quality is improved, especially at those bitrates where coding artifacts become visible (mid to high QP values). The subjective performance evaluation that was conducted showed that the proposed method can offer a measurable improvement in perceived quality relative to a constant QP approach, with Bjontegaard mean opinion scores (MOS) gains reaching almost 9% for the test sequences used. The paper additionally highlights the need for further work in order to increase gains in perceived quality and optimise parameter selection.
- Perceptual coding maps
- QP variation
- Subjective quality assessment