Encoding strategies for realizing MPEG-4 universal scalable video coding

The universal scalability, which integrates different types of scalabilities and consequently provides a large scaling range for each codec parameter, is of high interests to the applications in the current heterogeneous surroundings. In our previous work, an MPEG-4 universal scalable codec basing on a layered path-tree structure [1,2] has been addressed, in which a video layer and the coding order of two consecutive layers are interpreted as a node and the parent-to-child relationship in a path-tree, respectively. Since individual video layers can be coded separately using different coding tools, defined in MPEG-4 simple scalable profile (SSP) [3] and fine-granularity scalable profile (FGS) [4], the proposed scalable video coder may achieve spatial, temporal and SNR enhancements simultaneously. In this paper, based on some visual observations, we will address some encoding strategies applicable to the universal scalable coding, including the spatial-temporal quality tradeoff, the region sensitivity and the frequency weighting. Applying these strategies will take the content characteristics into consideration and can determine better coding parameters. As a result, the bit allocation of an encoder becomes more sensitive and correlative to those perceptually important parts of spatial, temporal and SNR enhancements. Next, a batch encoding process is conducted to generate universal scalable streams automatically, in which all the abovementioned encoding strategies are fully integrated together. The preliminary experiments show that better visual quality can be obtained within a large range of bitrates.