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 layered coding is that it invariably results in a reduction in overall coding 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 resolution services can be reconstructed using only a subset of the total generated data. This would mean that there would be no impact on the coding efficiency of the highest quality service. In this paper we demonstrate that the quality of the lower layer when this approach is used is fundamentally limited by drift. It is shown that even a coarsely quantized, low rate correction signal provides a major benefit to the quality of this lower layer service while still not impacting significantly on the coding efficiency of the high quality service. Of course, some overhead is introduced in the coding of the lower quality service but the total overhead is still significantly better than simulcast.