A projection onto convex sets (POCS)-based method for consistent
reconstruction of a signal from a subset of quantized coefficients
received from an N.times.K overcomplete transform. By choosing a frame
operator F to be the concatenization of two or more K.times.K invertible
transforms, the POCS projections are calculated in R.sup.K space using
only the K.times.K transforms and their inverses, rather than the larger
R.sup.N space using pseudo inverse transforms. Practical reconstructions
are enabled based on, for example, wavelet, subband, or lapped transforms
of an entire image. In one embodiment, unequal error protection for
multiple description source coding is provided. In particular, given a
bit-plane representation of the coefficients in an overcomplete
representation of the source, one embodiment of the present invention
provides coding the most significant bits with the highest redundancy and
the least significant bits with the lowest redundancy. In one embodiment,
this is accomplished by varying the quantization stepsize for the
different coefficients. Then, the available received quantized
coefficients are decoded using a method based on alternating projections
onto convex sets.