Flexible macroblock ordering as a content adaptation tool in H.264/AVC
Yves Dhondt, Peter Lambert, Stijn Notebaert, Rik Van de Walle · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 2005
H.264/AVC is the newest block based video coding standard from MPEG and VCEG. It not only provides superior and efficient video coding at various bit rates, it also has a "network-friendly" representation thanks to a series of new techniques which provide error robustness. Flexible Macroblock Ordering (FMO) is one of the new error resilience tools included in H.264/AVC. Here, we present an alternative use of flexible macroblock ordering, using its idea of combining non-neighboring macroblocks together in one slice. Instead of creating a scattered pattern, which is useful when transmitting the data over an error-prone network, we divide the picture into a number of regions of interest and one remaining region of disinterest. It is assumed that people watching the video will pay much more attention to the regions of interest than to the remainder of the video. So we compress the regions of interest at a higher bit rate than the regions of disinterest, thus lowering the overall bit rate. Simulations show that the overhead introduced by using rectangular regions of interest is minimal, while the bit rate can be reduced by 30% and more in most cases. Even at those reductions the video stays pleasant to watch. Transcoders can use this information as well by reducing only the quality of the regions of disinterest instead of the quality of the entire picture if applying SNR scalability. In extreme cases the regions of disinterest can even be dropped easily, thus reducing the overall bit rate even further.