Variable Length Encoding of Binary Memoryless Sources with a Fidelity Measure

This concise paper deals with variable length source coding for binary memoryless sources with a fidelity criterion. The encoding scheme under consideration is an (
M_{c}, N, K
) code consisting of a distortionless run-length inner code of size M
c
and an outer code that maps each source vector of length
N
to a codeword of length less than or equal to
K
. The encoding of the outer code is accomplished by means of a trellis search, and the distortion measure used is a Hamming distance. For composite binary memoryless sources an adaptive (
M_{c}, N
) code can be constructed by varying the constraint
K
on codeword length according to the source statistics. The (
M_{c}, N, K
), and (
M_{c}, N
) codes are insensitive to the inaccuracy in estimating the source probabilities. Rate-distortion curves, obtained by computer simulation, are plotted along with the theoretical rate-distortion function
R(D)
.