Generating lists of positions of coefficients in a code block to be entropy coded

Abstract

A method of entropy coding symbols representative of a code block comprising transform coefficients of a digital image. The method comprises a significance propagation pass , a magnitude refinement pass , and a cleanup pass for entropy coding the symbols. The method generates ( ), prior to the significance propagation pass of the current bitplane, a first list of positions of those coefficients in the code block that have symbols to be entropy coded during the significance propagation pass of the current bitplane. The method also generates ( ), prior to the magnitude refinement pass of the current bitplane, a second list of positions of those said coefficients in the code block that have symbols to be entropy coded during the magnitude refinement pass of the current bitplane. The method further generates ( ), prior to the cleanup pass of the current bitplane, a third list of positions of those said coefficients in the code block that have symbols to be entropy coded during the cleanup pass of the current bitplane.