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.

Abstract: A method and system for identifying end systole and end diastole frames within an angiography sequence. A plurality of images produced during an angiography sequence are digitized, producing digital image data in which gray scale values for each of the pixels in the images are represented. The digital image data are input to a computer (48) to determine the frames in which the coronary arteries are most visible. The coronary arteries are made visible in the images by injecting a radio-opaque contrast substance into the arteries. The frames that occur a end diastole are preferred for diagnostic analysis because the arteries are distended, spread apart from each other, and moving very slowly. To identify such frames for further analysis, the total length of edges within a centered window covering approximately one-fourth of each image is determined. The edges represent spatial transitions between relatively light and dark areas in the image that occur across the borders of the coronary arteries.