Automatic scene decomposition and optimization of mpeg compressed video

Abstract

Analysis of video data in an MPEG compressed format to identify scene changes to facilitate indexing to access specific video frames and to improve data compression and/or quality of the compressed video. MPEG compressed video data include I-pictures, P-pictures, and B-pictures. Scene changes are identified by analyzing P-pictures using average error power, based upon direct cosine transform components in the compressed data, and/or using an interframe correlation between a P-picture and its past reference frame. When a scene change occurs, average error power becomes large and interframe correlation between frames becomes substantially zero. Alternatively (or in addition), B-pictures in a video slot can be analyzed, in terms of interframe correlation between past and future reference frames, using either an AND analysis technique or an OR analysis technique. The AND analysis identifies a scene change when two or more B-pictures between two reference frames defining the video slot all imply a scene change, while the OR analysis indicates that a scene change has not occurred in the video slot if one B-picture implies that a scene change has not occurred. Once the scene changes have been identified, all I-pictures not occurring at a scene change are converted to P-pictures, and all P-pictures immediately following a scene change are converted to I-pictures. This step improves compression and/or quality of the compressed video, since P-pictures require less data than do I-pictures, and fewer I-pictures will be used in the compressed data following this step.