IMPROVED ENCODING PROCESS USING A PALETTE MODE

The present invention is related to video coding and decoding, in particular HEVC RExt that define a palette coding mode dedicated to the coding of screen contents. In improved palette coding modes according to the invention, when building a palette, each time a new pixel is added to the class a palette entry defines, the palette entry is modified to take the means value of the pixels belonging to such class. In other improved palette coding modes, a built palette is post-processed to substitute a palette entry with a close entry of a palette predictor PRED. In yet other embodiments, palette coding modes having different threshold values to drive the building of their respective palettes are successively tested to use the best one in terms of rate-distortion criterion.