In order to be able to better cope with packet loss, H.264/AVC, besides offering superior coding efficiency, also comes with a number of error resilience tools. The goal of these tools is to enable the decoding of a bitstream containing encoded video, even when parts of it are missing. On top of that, the visual quality of the decoded video should remain as high as possible. In this paper, we will discuss and evaluate one of these tools, in particular the data partitioning tool. Experimental results will show that using data partitioning can significantly improve the quality of a video sequence when packet loss occurs. However, this is only possible if the channel used for transmitting the video allows selective protection of the different data partitions. In the most extreme case, an increase in PSNR of up to 9.77 dB can be achieved. This paper will also show that the overhead caused by using data partitioning is acceptable. In terms of bit rate, the overhead amounts to approximately 13 bytes per slice. In general, this is less than 1% of the total bit rate. On top of that, using constrained intra prediction, which is required to fully exploit data partitioning, causes a decrease in quality of about 0.5 dB for high quality video and between 1 and 2 dB for low quality video.
With all the hype created around multimedia in the last few years, consumers expect to be able to access multimedia content in a real-time manner, anywhere and anytime. One of the problems with the real-time requirement is that transportation networks, such as the Internet, are still prone to errors. Due to real-time constraints, retransmission of lost data is, more often than not, not an option. Therefore, the study of error resilience and error concealment techniques is of the utmost importance since it can seriously limit the impact of a transmission error. In this paper an evaluation of a part of flexible macroblock ordering, one of the new error resilience techniques in H.264/AVC, is made by analyzing its costs and gains in an error-prone environment. This paper concentrates on the study of flexible macroblock ordering (FMO). More specifically a study of scattered slices, FMO type 1, is made. Our analysis shows that FMO type 1 is a good tool to introduce error robustness into an H.264/AVC bitstream as long as the QP is higher than 30. When the QP of the bitstream is below 30, the cost of FMO type 1 becomes a serious burden.
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.