  We introduce the idea of distortion side information, which does not directly
depend on the source but instead affects the distortion measure. We show that
such distortion side information is not only useful at the encoder, but that
under certain conditions, knowing it at only the encoder is as good as knowing
it at both encoder and decoder, and knowing it at only the decoder is useless.
Thus distortion side information is a natural complement to the signal side
information studied by Wyner and Ziv, which depends on the source but does not
involve the distortion measure. Furthermore, when both types of side
information are present, we characterize the penalty for deviating from the
configuration of encoder-only distortion side information and decoder-only
signal side information, which in many cases is as good as full side
information knowledge.
