LAYERED CODING USING BITSTREAM DECOMPOSITION WITH DRIFT CORRECTION

It is well known that layered video coding is useful both for service interworking and as an aid to error resilience. A major drawback of la yered coding is that it invariably results in a reduction in overall c oding efficiency for the high quality service. An attractive approach would be one in which the high quality service is coded, and then the resulting bitstream is decomposed in such a way that the lower resolut ion services can be reconstructed using only a subset of the total gen erated data. This mould mean that there mould be no impact on the codi ng efficiency of the highest quality service. In this paper we demonst rate that the quality of the lower layer when this approach is used is fundamentally limited by drift. It is shown that even a coarsely quan tized, low rate correction signal provides a major benefit to the qual ity of this lower layer ser,ice while still not impacting significantl y on the coding efficiency of the high quality service. Of course, som e overhead is introduced in the coding of the lower quality service bu t the total overhead is still significantly better than simulcast.