Abstract-In this paper, we are concerned with robust H.264/AVC video transmission over lossy packet networks and present a hierarchical unequal packet loss protection (HULP) scheme in a transmission system that efficiently combines erasure coding, H.264/AVC error resilience techniques and importance measures in video coding schemes. The importance of the video stream packets is distinguished by three criteria: the frame sequence number in a group of pictures (GOP), the per-frame bitrate and the H.264/AVC data partition type. Using a fixed amount of redundancy, more important packets of a video stream are protected with a more powerful erasure code than the less important packets. We demonstrate the effectiveness of this approach by system implementation and performance evaluation. In the presence of packet loss, we show that the received video quality, as measured by PSNR, is significantly improved when the HULP scheme is used. More importantly, in our experiments, HULP can achieve higher PSNR values and better user perceived quality, but requiring less redundancy, than equal loss protection (ELP) schemes.

Abstract-Although a number of investigations have been conducted using IEEE 802.11e enabled networks to stream class differentiated video, very few reports are available based on a real testbed. In our work, we set up a wireless testbed for H.264 video streaming through assigning the partitioned video packets onto the DCF MAC layer and different access classes of the EDCA MAC layer. We investigate three assignment schemes: 1) DCF is used and all the traffic is treated equally; 2) video traffic is assigned to each of the access classes in turn; and 3) the packets are assigned according to their importance and the class priority. In addition to the video stream we introduce TCP traffic from three clients in the best effort class. We show that video quality can be improved through properly assigning packets to wireless access classes compared to the standard best effort scheme. Importantly, we show, based on our testbed results, that the single class assignment can achieve better performance than the multi-class assignment suggested by other researchers. Finally we show that virtual contention between traffic classes at the access point is an important issue to address.

In this paper we investigate the properties of packet losses when packets are transferred using an overlay network. Three packet loss models are established for different packet loss scenarios: random, burst and congestion. Based on these models, it has been shown through simulation that in random and burst packet losses environments the packet loss rate increases as the number of diverse paths increases, whilst the opposite is true in the congestion case. A combined model is presented and then developed to address the situation where the last link of the system experiences different loss patterns to the rest of the network, such as a wireless access link.

Abstract-In this paper, a robust H.264/AVC video transmission system over lossy packet network is investigated and implemented. The H.264/AVC standard has defined a new data partition scheme which can be used to perform unequal loss protection (ULP) in video transmission systems. However, few actual implementation and experiments which integrate data partition and loss protection algorithms have been reported. Based on the H.264/AVC data partitioning mechanism, we implement three loss protection schemes using Reed-Solomon and XOR parity codes, namely equal loss protection (ELP), ULP and partition A protection only (PAP) .The performance of each scheme is evaluated under different network environments. Experimental results and performance analysis show that ELP has higher Peak Signal-to-Noise Ratio (PSNR) values than ULP and PAP, but PAP requires the least redundancy and offers the best tradeoffs between PSNR values and redundancy among all the three schemes.

Abstract-In this paper we investigate the effect of path diversity on the packet loss performance through simulations and experiments using three overlay networks created on top of the PlanetLab testbed. The overlay network consists of a number of relay nodes that are positioned around the Internet. In each of the overlay networks UDP packets are streamed from a client to a destination for a period of 50 days, across up to six paths with a static packet dispatching algorithm. From the results obtained, we can see that increasing the number of paths could increase as well as decrease the packet loss probability, depending on the network environment and the structure of the multiple paths created. We have also investigated the correlation in the underlying network and demonstrated the performance of the metric defined.