No abstract

No abstract

Real-time processing of video waveforms has been implemented for the purpose of analyzing image dynamics. A digital preprocessor yields data sets that describe the difference between selected fields of an input video signal in both the spatial and temporal domains. Further reduction and analysis of the acquired data can provide several measures of image activity such as the frame-to-frame correlation, the framedifference signal (FDS), and statistics of scene lengths. The results of a series of measurements of the dynamics of typical broadcast television programs are presented. It is demonstrated that image activity is separable into two distinct classes, one caused by image and camera movement, and the other by scene switches.The oft-repeated television image is highly redundant and it is possible to exploit interframe and intraframe relationships of the image sequences to reduce the amount of information that must be transmitted.If it were not for the effect that flicker has on the human reception system, many video .communication processes could function adequately with image renewal rates well below 30 frames/s, since for a large class of television programs image motion is very slow. Such conditions often exist during teleconferencing and teleteaching. In these cases, activity, as measured by the change in the image, may be used as a trigger to initiate the renewal of the stored image portion of an audiovisual communication. For example, when a single television channel exists for the communication of a number of television images, access to the channel could be determined by the activity in each, and a new frame transmitted to a storage device associated with each source.The purpose of the work described in this correspondence was t o develop apparatus and procedures to measure the image activity of television programs in real time and to explore the hypothesis that these measures could be used to classify programs on the basis of the average number of frames required to adequately represent their content. The primary objective has been to obtain a small set of parameters with which to characterize activity.Although the redundancy in television images has been the subject of extensive studies related to potential bandwidth compression schemes, these studies have usually been restricted to simple image situations or to the analysis of limited amounts of data.In pioneering studies, Seyler [ 1 ] , [ 21 measured the probability distribution of frame-difference signals, and showed that Paper approved by the Editor for Communication Theory of the IEEE Communications Society for publication without oral presentation. Manuscript is with Computing Devices of Canada, Ottawa, Ont., Canada.the gamma distribution provides a good fit to the probability density function of television frame differences. This work has been repeated recently and similar results were reported Soroka [4] computed the interframe correlation of a sample television program by optically correlating a sequence of images that had been transferred on...

No abstract

No abstract