1. A method comprising: accessing changes in a list for coded data, the changes having a syntax element, an original value and one or more candidate alternative values; determining for a subset a group of compliant changes from the list of changes, the compliant changes being compliant with a coding protocol; selecting for the subset only compliant changes also meeting at least one performance criterion; and removing or preventing changes from being in the subset if the propagation path of said changes intersect with the propagation path of a previously selected change in the subset, wherein a propagation path for a change consists of all the blocks in the encoded data which are affected by said change.