An Optimized Dynamic Scene Change Detection Algorithm for H.264/AVC Encoded Video Sequences

Scene change detection plays an important role in a number of video applications, including video indexing, semantic features extraction, and, in general, pre- and post-processing operations. This paper deals with the design and performance evaluation of a dynamic scene change detector optimized for H.264/AVC encoded video sequences. The detector is based on a dynamic threshold that adaptively tracks different features of the video sequence, to increase the whole scheme accuracy in correctly locating true scene changes. The solution has been tested on suitable video sequences resembling real-world videos thanks to a number of different motion features, and has provided good performance without requiring an increase in decoder complexity. This is a valuable issue, considering the possible application of the proposed algorithm in post-processing operations, such as error concealment for video decoding in typical error prone video transmission environments, such as wireless networks. 1. Introduction Scene change detection is an issue easy to solve for humans, but it becomes really complicated when it has to be performed automatically by a device, which usually requires complex algorithms and computations, involving a huge amount of operations. The process of scene change detection becomes more and more complex when other constraints and specific limitations, due to the peculiar environment of application, may be present. A scene in a movie, and, in general, in a video sequence, can be defined as a succession of individual shots semantically related, where a shot is intended as an uninterrupted segment of the video sequence, with static frames or continuous camera motion. In the field of video processing, scene change detection can be applied either in preprocessing and postprocessing operations, according to the purposes that the detection phase has to achieve, and with different features and performance. As an example, in H.264/AVC video coding applications, scene change detection can be used in preprocessing as a decisional algorithm, in order to force Intraframe encoding (I) instead of temporal prediction (P), when a scene change occurs, and to confirm predicted or bi-predicted (B) coding for the remaining frames. As discussed in [1], a dynamic threshold model for real time scene change detection among consecutive frames may serve as a criterion for the selection of the compression method, as well as for the temporal prediction; it may also help to optimize rate control mechanisms at the encoder. In lossy video transmission environments, the effects of