Dissolve detection in MPEG compressed video

Abstract

A dissolve is a gradual transition from one shot to another in a video, resulting from gradually scaling the intensity values of the two shots. Up to now, there have been very few algorithms for detecting dissolves. By analysing characteristics exhibited by a typical dissolve, we propose two methods of detecting dissolves directly in MPEG compressed video. The first method is based on the characteristics that the average intensity of each frame changes linearly with time during a dissolve. Dissolves are detected by finding rectangular shapes on the difference curve of the average frame intensity values, which can be obtained by averaging the DC values of luminance blocks of each frame in an MPEG stream. The second method is based on the characteristics that each pixel changes its intensity value linearly and gradually during a dissolve. As a result, most of the pixel difference values between two consecutive frames will be moderate and fall within a range. This range is determined by the duration of a typical dissolve and the maximal intensity difference allowed. If the number of pixels with difference values falling within such a range is large over a period of time, a dissolve can be declared. For an MPEG stream, we define a measure D as the percentage of blocks with DC difference values falling within a specified range. Dissolves are thus detected by finding periods with consistent large values of D. Both methods have been tested on a range of MPEG video sequences and the results show that most dissolves can be correctly detected. Since the proposed methods operate directly on compressed data, they are much more efficient than some pixel domain methods.