  We present adaptive on-line schemes for lossy encoding of individual
sequences under the conditions of the Wyner-Ziv (WZ) problem. In the first part
of this article, a set of fixed-rate scalar source codes with zero delay is
presented. We propose a randomized on-line coding scheme, which achieves
asymptotically (and with high probability), the performance of the best source
code in the set, uniformly over all source sequences. The scheme uses the same
rate and has zero delay. We then present an efficient algorithm for
implementing our on-line coding scheme in the case of a relatively small set of
encoders. We also present an efficient algorithm for the case of a larger set
of encoders with a structure, using the method of the weighted graph and the
Weight Pushing Algorithm (WPA). In the second part of this article, we extend
our results to the case of variable-rate coding. A set of variable-rate scalar
source codes is presented. We generalize the randomized on-line coding scheme,
to our case. This time, the performance is measured by the Lagrangian Cost
(LC), which is defined as a weighted sum of the distortion and the length of
the encoded sequence. We present an efficient algorithm for implementing our
on-line variable-rate coding scheme in the case of a relatively small set of
encoders. We then consider the special case of lossless variable-rate coding.
An on-line scheme which use Huffman codes is presented. We show that this
scheme can be implemented efficiently using the same graphic methods from the
first part. Combining the results from former sections, we build a generalized
efficient algorithm for structured set of variable-rate encoders. The
complexity of all the algorithms is no more than linear in the sequence length.
