A generalized grouping and retrieval scheme for stored MPEG video

MPEG, in addition to being an international standard, is currently the most popular coding scheme for stored video. For several applications that require stored video, such as video-on-demand, it is advantageous to group MPEG frames into segments. Retrieving segments instead of individual frames can result in a more efficient use of disk retrieval resources and consequently, in the support of a larger number of users and in a more cost-effective system. Depending on the value of parameters such as desired user quality of service, size and cost of required buffers, number of disks to stripe a segment across, etc., a certain segment length (defined as the number of frames per segment) may be preferred over others. In this paper, we propose a generalized grouping scheme that may be used to achieve any desired segment length. Properties of such a grouping scheme and formulae that may be used to achieve such a grouping have been provided. Since a segment is an atomic unit of video retrieval, retrieval of some segments is skipped during fast playback. Some frames belonging to retrieved segments may be discarded due to the unavailability of other frames necessary for their decoding. Tradeoffs between different kinds of fast playback (i.e., the choice of skipped segments) and the number of discarded frames is discussed.