A compressed pixel level for a pixel in a frame of an image is compared
with the (compressed) pixel level for the same pixel in a previous image
frame. If the pixel level is unchanged, then the pixel is not moving. An
uncompressed pixel level is then used for that pixel in the current
image. If the pixel level is changed, then the pixel is moving, and a
decompressed, boosted pixel level is used for that pixel in the current
image.