Decoding method and corresponding device

摘要

Decoding a picture parameter set used for decoding images from a bitstream. In a first embodiment a colour component parameter which indicates whether the image is monochrome and is involved in at least two steps of the decoding method is decoded and at least one step of the decoding method is skipped or amended if the parameter indicates that the image is monochrome. Preferably, this step is skipped rather than amended and relates to the application of a residual adaptive colour transform. In a second embodiment the decoding method includes a step related to the residual adaptive colour transform and a step for defining a palette predictor initialiser. The defining step is processed based on the value of a colour component parameter which indicates whether or not the image is monochrome and the colour component parameter is inferred from the execution of the residual adaptive colour transform. These embodiments rely on a redundancy in the parameters encoded in the extension to the picture parameter set defined in the HEVC Screen Content Coding draft specification A third embodiment has a step of initialising a palette predictor, the step being governed by rules when switching between images based on the number of colour components in each image.