By using transform coding, image transmission rates as low as
0.5 bit/pel can be achieved. Generally, the bit rate reduction
is achieved by allocating fewer bits to low energy high
order coefficients, However, to ensure reasonably good picture
quality, a large number of bits has to be allocated to high
energy dc coefficients for both fine quantization and good
channel error immunity, A technique has been developed that,
in some cases, allows the de coefficients to be estimated at
the receiver, thus eliminating a major source of difficulty
with respect to channel errors. [Continues.
