The hierarchical encoding encodes an image in multiple resolutions.
For e.g., one could provide 320x240, 640x480 and 1280x960 versions of an
image; the decoder at the receiving end can choose the optimum resolution
depending on the targets capabilities. Thus, high-resolution images can be
easily viewed in lower resolution devices. This is particularly relevant to
small portable terminals and for conferencing where multiple smaller images
need to share the screen with full size images at different times.