Establishment of linkages across GOP boundaries for reverse playback on compressed video

  • Authors:
  • Chang-Hong Fu;Yui-Lam Chan;Wan-Chi Siu

  • Affiliations:
  • -;-;-

  • Venue:
  • Image Communication
  • Year:
  • 2014

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Abstract

Modern video coding standards are basically designed for forward playback only. Recently, we have developed a number of macroblock(MB)-based techniques to support reverse playback for compressed videos by exploiting the motion relationship between adjacent frames. Nevertheless, the MB-based techniques give no effect 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, we borrow ideas from the SP-picture concept in H.264 to establish linkages across GOP boundaries by encoding the last frame of each GOP as a primary SP-frame as well as its corresponding secondary SP-frame. During reverse playback across GOP boundaries, the secondary SP-frame is decoded by using the I-frame in its succeeded GOP as the motion-compensated frame. We believe that we are the first to consider SP-frames to build the linkage between two GOPs for reverse playback. Our scheme can also be used in any future coding standards that offer the similar coding mechanism of SP-frames. This approach can remarkably mitigate the required decoder complexity over 90% during reverse playback across GOP boundaries, but the straightforward implementation introduces serious drift errors. Therefore, as a further contribution of this paper, a novel scheme is designed to avoid the drift problem. Instead of arranging the primary SP-frame before the I-frame, the proposed scheme allocates various MBs within the GOP to be encoded as the SP-picture type. This completely new and unique arrangement for SP coding in which a primary SP MB and its corresponding secondary SP MB are no longer at the same time instant is specially designed for our MB-based techniques, and can be proved to eliminate the possible drift effect for reverse playback. With this allocation strategy, results from our experimental work show that the inherent GOP discontinuity problem can be avoided without introducing additional drift between forward and reverse playback.