A simplified syntax signalling for the number of palette indices is disclosed, where the syntax element corresponding to the total number of palette indices minus one is signalled and the palette indices are associated with the copy-index modes in the current block. In another embodiment, a syntax corresponding to the number of palette indices minus 1 is signalled, where the palette indices are associated with the copy-index modes in the current block. According to this embodiment, the syntax is constrained to a range from 0 to block size minus 1. In yet another embodiment, conformance constraint is imposed on the palette predictor run. For a current position of the palette predictor list, a syntax element corresponding to a current palette predictor run is parsed from the input bitstream and the syntax element is constrained to a range of values access valid entries in the palette predictor.