Low-complexity wavelet-based scalable image & video coding for home-use surveillance

We study scalable image and video coding for the surveillance of rooms and personal environments based on inexpensive cameras and portable devices. The scalability is achieved through a multi-level 2D dyadic wavelet decomposition featuring an accurate low-cost integer wavelet implementation with lifting. As our primary contribution, we present a modification to the SPECK wavelet coefficient encoding algorithm to significantly improve the efficiency of an embedded system implementation. The modification consists of storing the significance of all quadtree nodes in a buffer, where each node comprises several coefficients. This buffer is then used to efficiently construct the code with minimal and direct memory access. Our approach allows efficient parallel implementation on multi-core computer systems and gives a substantial reduction of memory access and thus power consumption. We report experimental results, showing an approximate gain factor of 1,000 in execution time compared to a straightforward SPECK implementation, when combined with code optimization on a common digital signal processor. This translates to 75 full color 4CIF 4:2:0 encoding cycles per second, clearly demonstrating the realtime capabilities of the proposed modification.