Impact of motion on the random access efficiency of scalable compressed video

To achieve high access efficiency in scalable video compression, the embedded codestream should facilitate efficient viewing through a window with compact support in space and time. The ability to interact with a region of interest in any spatio-temporal subband is limited by the granularity of the code blocks chosen during compression, which is linked to coding performance. Previous studies have investigated the optimal code block dimensions with respect to coding efficiency and random accessibility without considering the impact of motion. This paper further examines how the random access cost is exacerbated by motion. The loss in performance due to motion-compensation is considered from a random access perspective, in the context of a non-separable spatio-temporal subband transform. The methods are general and the results are pertinent to a variety of interactive video browsing applications.