Title:   "Multi-Resolution   Layered   Coding   for   Real-Time    Image   
Transmission: Architectural and Error Control Considerations"

Authors: James K. Han and George C. Polyzos

To appear in: Real-Time Imaging, Academic Press, 1997.

We examine the rationale for and systems aspects of using layered coding
for   the   transmission   of   images   and  video  over  heterogeneous
communication networks.  We  advocate  Multi-resolution  Layered  Coding
(MLC)  and present architectural alternatives that can support it within
the scope of existing standards and technologies.  Since the premise  of
layered  coding  is  controlled  loss,  the  issues of error control and
concealment are central.  We demonstrate that MLC  exhibits  good  error
tolerance,  effectively  compensating  for  errors  in  situations where
traditional error concealment schemes, based  on  the  interpolation  of
pixels in adjacent blocks, are ineffective.  In particular, MLC yields a
higher Peak Signal-to-Noise Ratio  (PSNR)  than  two-layer  coding  when
packet  loss  occurs  in  the base layer.  Finally, we show that MLC can
effectively exploit efficient network  error  control  strategies  which
distribute  redundancy  non-uniformly  and  provide  unequal  levels  of
protection across layers.