Design and evaluation of tile selection algorithms for tiled HTTP adaptive streaming (Best paper award)

The future of digital video is envisioned to have an increase in both resolution and interactivity. New resolutions like 8k UHDTV are up to 16 times as big in number of pixels compared to current HD video. Interactivity includes the possibility to zoom and pan around in video. We examine Tiled HTTP Adaptive Streaming (TAS) as a technique for supporting these trends and allowing them to be implemented on conventional Internet infrastructure. In this article, we propose three tile selection algorithms, for different use cases (e.g., zooming, panning). A performance evaluation of these algorithms on a TAS testbed, shows that they lead to better bandwidth utilization, higher static Region of Interest (ROI) video quality and higher video quality while manipulating the ROI. We show that we can transmit video at resolutions up to four times larger than existing algorithms during bandwidth drops, which results in a higher quality viewing experience. We can also increase the video quality by up to 40 percent in interactive video, during panning or zooming

On the merits of SVC-based HTTP adaptive streaming

HTTP Adaptive Streaming (HAS) is quickly becoming the dominant type of video streaming in Over-The-Top multimedia services. HAS content is temporally segmented and each segment is offered in different video qualities to the client. It enables a video client to dynamically adapt the consumed video quality to match with the capabilities of the network and/or the client's device. As such, the use of HAS allows a service provider to offer video streaming over heterogeneous networks and to heterogeneous devices. Traditionally, the H. 264/AVC video codec is used for encoding the HAS content: for each offered video quality, a separate AVC video file is encoded. Obviously, this leads to a considerable storage redundancy at the video server as each video is available in a multitude of qualities. The recent Scalable Video Codec (SVC) extension of H. 264/AVC allows encoding a video into different quality layers: by dowloading one or more additional layers, the video quality can be improved. While this leads to an immediate reduction of required storage at the video server, the impact of using SVC-based HAS on the network and perceived quality by the user are less obvious. In this article, we characterize the performance of AVC- and SVC-based HAS in terms of perceived video quality, network load and client characteristics, with the goal of identifying advantages and disadvantages of both options

On the impact of redirection on HTTP adaptive streaming services in federated CDNs

HTTP Adaptive Streaming (HAS) refers to a set of novel streaming services that allow clients to adapt video quality based on current network conditions. Their use of existing HTTP delivery infrastructure makes them perfectly suited for deployment on existing Content Delivery Networks (CDNs). Nevertheless, this leads to some new challenges, related to the distribution of content across servers and the latency caused by request redirection. The federation or interconnection of CDNs proliferates these problems, as it allows content to be distributed across networks and increases the number of redirects. This paper focuses on the second problem, assessing the impact of redirection on the Quality of Experience of HAS in CDN interconnection scenarios. Additionally, several novel inter-CDN request routing policies are proposed that aim to reduce the number of redirects. Our results indicate that redirection latency significantly impacts performance of HAS and more intelligent routing mechanisms are capable of solving this problem

Improved DASH Architecture for Quality Cloud Video Streaming in Automated Systems

In modern times, multimedia streaming systems that transmit video across a channel primarily use HTTP services as a delivery component. Encoding the video for all quality levels is avoided thanks to fuzzy based encoders' ability to react to network changes. Additionally, the system frequently uses packet priority assignment utilising a linear error model to enhance the dynamic nature of DASH without buffering. Based on a fuzzy encoder, the decision of video quality is made in consideration of the bandwidth available. This is a component of the MPEG DASH encoder. The Fuzzy DASH system seeks to increase the scalability of online video streaming, making it suitable for live video broadcasts through mobile and other devices

Rate adaptation for dynamic adaptive streaming over HTTP in content distribution network

Recently the 3rd Generation Partnership Project (3GPP) and the Moving Picture Experts Group (MPEG) specified Dynamic Adaptive Streaming over HTTP (DASH) to cope with the shortages in progressive HTTP based downloading and Real-time Transport Protocol (RIP) over the User Datagram Protocol (UDP), shortly RTP/UDP, based streaming. This paper investigates rate adaptation for the serial segment fetching method and the parallel segment fetching method in Content Distribution Network (CDN). The serial segment fetching method requests and receives segments sequentially whereas the parallel segment fetching method requests media segments in parallel. First, a novel rate adaptation metric is presented in this paper, which is the ratio of the expected segment fetch time (ESFT) and the measured segment fetch time to detect network congestion and spare network capacity quickly. ESFT represents the optimum segment fetch time determined by the media segment duration multiplied by the number of parallel HTTP threads to deliver media segments and the remaining duration to fetch the next segment to keep a certain amount of media time in the client buffer. Second, two novel rate adaptation algorithms are proposed for the serial and the parallel segment fetching methods, respectively, based on the proposed rate adaptation metric. The proposed rate adaptation algorithms use a step-wise switch-up and a multi-step switch-down strategy upon detecting the spare networks capacity and congestion with the proposed rate adaptation metric. To provide a good convergence in the representation level for DASH in CDN, a sliding window is used to measure the latest multiple rate adaptation metrics to determine switch-up. To decide switch-down, a rate adaptation metric is used. Each rate adaptation metric represents a reception of a segment/portion of a segment, which can be fetched from the different edge servers in CDN, hence it can be used to estimate the corresponding edge server bandwidth. To avoid buffer overflow due to a slight mismatch in the optimum representation level and bandwidth, an idling method is used to idle a given duration before sending the next segment. In order to solve the fairness between different clients who compete for bandwidth, the prioritized optimum segment fetch time is assigned to the newly joined clients. The proposed rate adaptation method does not require any transport layer information, which is not available at the application layer without cross layer communication. Simulation results show that the proposed rate adaptation algorithms for the serial and the parallel segment fetching methods quickly adapt the media bitrate to match the end-to-end network capacity, provide an advanced convergence and fairness between different clients and also effectively control buffer underflow and overflow for DASH in CDN. The reported simulation results demonstrate that the parallel rate adaptation outperforms the serial DASH rate adaptation algorithm with respect to achievable media bitrates while the serial rate adaptation is superior to the parallel DASH with respect to the convergence and buffer underflow frequency. (C) 2011 Elsevier B.V. All rights reserved