IMPROVEMENT OF DEBLOCKING CORRECTIONS ON FLAT AREAS AND PROPOSAL FOR A LOW-COST IMPLEMENTATION
Frederique Crete, Marina M. Nicolas, Patricia Ladret · 2007
The quantization of data from individual block-based Discrete Cosine Transform generates the blocking effect estimated as the most annoying compression artefact. It appears as an artificial structure caused by noticeable changes in pixel values along the block boundaries. Due to the masking effect, the blocking artefact is more annoying in flat areas than in textured or detailed areas. Existing low-cost algorithms propose strong low-pass filters to correct this artefact in flat areas. Nevertheless, they are confronted to a limitation based on their filter length. This limitation can introduce other artefacts such as ghost boundaries. We propose a new principle to detect and correct the boundaries on flat areas without being limited to a fix number of pixels. This principle can be easily implemented in a low-cost post processing algorithm and completed with other corrections for perceptible boundaries on non-flat areas. This new method produces results which are perceived as more pleasing for the human eye than the other traditional low-cost methods.