The Mask Module is used to encode the various subtractions applicable to a Multi-frame Image.

The Enhanced XA IOD allows creating groups of mask-contrast pairs in the Mask Module, each group identified by a unique Subtraction Item ID within the Multi-frame Image.

The Enhanced XA IOD, with per frame macro encoding, supports multiple and different pixel-shift values per frame, each pixel-shift value is related to a given Subtraction Item ID.

It has to be assured that all the frames in the scope of a Subtraction Item ID have the pixel-shift values defined under that Subtraction Item ID.

In case a frame does not belong to any Subtraction Item ID, that frame does not necessarily have a pixel shift value encoded.