Reverse-play technique on compressed video across GOP boundaries

Abstract

In modern video coding standards, they are mainly designed for normal forward playback. Recently, we have developed a macroblock-based reverse-play scheme for compressed video bitstreams. By exploiting the motion relationship between two adjacent frames, this scheme can significantly reduce the requirements on the decoder complexity and network bandwidth during reverse playback. However, the MB-based technique does not works well on traversing GOP boundaries reversely since no inter-frame prediction takes place between the last frame of one GOP and the first frame of its succeeded GOP. In this paper, by utilizing a new SP picture type in the H.264, we can solve the GOP discontinuity problem by building linkages across GOP boundaries. Instead of arranging the primary SP-frame before the I-frame, a novel scheme is proposed to allocate various macroblocks within the GOP to be encoded as the SP type. This new arrangement for SP coding is specially designed for our macroblock-based reverse-play scheme and can be proved to eliminate the possible mismatch effect for reverse playback across GOP boundaries. With this allocation strategy, results from our experimental work confirm that the inherent GOP discontinuity problem can be avoided without introducing any mismatch between forward and reverse playback.