On Optimal Embedded Schedules of JPEG-2000 Packets

The JPEG-2000 compression standard codes images into data units, referred to as packets, such that images can be successfully decoded, while incurring some distortion, with a subset of these packets. This paper examines how to optimally select subsets of packets (referred to as schedules) that minimize distortion subject to varying rate constraints. We solve for the optimal schedule at a single rate by solving the precedence constraint knapsack problem (PCKP) via dynamic programming, and show that with modifications that consider the specific dependencies of JPEG-2000 packets, we can compute the optimal schedules for all rates through a single execution of our algorithm. We then analyze important properties of the optimal schedule. Using these properties, we look at a fused-greedy algorithm, similar to the recently proposed convex hull algorithm, to generate embedded schedules of JPEG-2000 packets. These embedded schedules have the property that all the JPEG-2000 packets in lower rate schedules are included in higher rate schedules; embedded schedules enable low-complexity, adaptive streaming. We demonstrate the algorithm's near optional performance through comparisons to the optimal performance for JPEG-2000 coded data.