Fast and e cient storage, browing, indexing, and retrieval of video is necessary for the development of various multimedia database applications. Given that video is typically stored e ciently in a compressed format, if we can analyze the compressed representation directly, we can avoid the costly overhead of decompressing and operating at the pixel level. Compressed domain parsing of video has been presented in earlier work where key frames are identi ed for shots, subshots, and scenes 9, 10]. In this paper, we describe key frame selection, feature extraction, indexing, and retrieval techniques that are directly applicable to MPEG compressed video. We develop a frame-type independent representation of the various types of frames present in an MPEG video in which all frames can be considered equivalent. Features are derived from the available DCT, macroblock, and motion vector information and mapped to a low-dimensional space where they can be accessed using standard database techniques. The spatial information is used as primary index while the temporal information is used to enhance the robustness of the system during the retrieval process. The techniques presented enable fast archiving, indexing, and retrieval of video. Our operational prototype typically takes a fraction of a second to retrieve similar video scenes from our database, with over 95% success.
In the compressed domain, Kobla et al. REF present a method for determining the flow of a pixel block using motion vectors and frame types.
Feature Normalization for Video Indexing and Retrieval
Computer Science