Drift-controlled scalable video coding in over-complete wavelet domain

In this work, we propose a novel scheme to minimize drift in scalable wavelet based video coding, which gives a balanced performance between compression efficiency and quality. Our drift control mechanism maintains two frame buffers in the encoder and decoder; one for the base layer and the other for the enhancement layer. Drift control is achieved by switching between these two buffers for motion compensation and prediction. In the encoder, the residues are coded using the embedded zerotree wavelet (EZW) algorithm. Our prediction is based on the enhancement layer, which inherently introduces drift in the system, if part of the enhancement layer is not available at the receiver. A measure of drift is computed based on channel information, and a threshold is set. When the measure exceeds the threshold, i.e. when drift becomes significant, we switch the prediction to be based on the base layer, which is always available to the receiver. The proposed coder determines the threshold and the buffer switching instance based on given channel conditions and the rate. Our coder offers high compression efficiency and acceptable video quality for different bit rate conditions. This proves that we need not completely eliminate drift and decrease compression efficiency to get better video quality.