Improved Delivery of Live SVC-based HTTP Adaptive Streaming Content

Over the past decades, the importance of multimedia services such as video streaming has increased considerably. Since streaming protocols such as Real Time Streaming Protocol (RTSP) and Real Time Transport Protocol (RTP) require server-side bit-rate adaptation schemes, they are not ideally suited to deal with highly heterogeneous and dynamically changing network conditions. Therefore, research shifted towards client-side adaptation schemes, requiring significantly less investments in server-side infrastructure. HTTP Adaptive Streaming (HAS) is now becoming omnipresent in video streaming services due to many advantages offered by HTTPbased streaming: reliable transmission over TCP, reuse of existing caching infrastructure and compatibility with NATs and firewalls. In HAS, the video content is split temporally into segments which are encoded at different quality rates. The client side heuristic decides at which quality rate each segment should be downloaded, based on measured network statistics, buffer filling level and device characteristics. Traditionally, Advanced Video Coding (AVC) is used to encode the different segments, introducing a significant amount of redundancy across quality representations. Scalable Video Coding (SVC) can cope with these issues of content redundancy by creating dependencies between the base and enhancement layers. Adopting SVC in HAS significantly improves caching and bandwidth efficiency at the server side. Another advantage of SVC, is the ability to gradually upgrade the quality of the video by downloading additional video layers. Academia and industry are showing a growing interest in the use of HAS for managed networks. The extensive content catalogue and increased flexibility in terms of supported devices of Over The Top (OTT)-services (e.g., YouTube, Hulu, Netflix) but delivered over a managed network, could greatly benefit both provider and end-user. Delivering paid HAS services, however, requires the ability for the provider to offer guarantees in terms of reliability to the end-users. Since HAS services are originally designed for OTT scenarios, current-generation HAS players require a large play-out buffer to guarantee continuous playback. This makes them ill-suited for live television, as it significantly increases the live signal delay. Shrinking the buffer size has however some implications on the reliability of the streaming service and requires the player to react in a fast and robust way to changes in the network. Therefore, we propose a managed HAS multimedia framework, using SVC and prioritization in the network, which Fig. 1: Network setup used during the demonstration. allows to offer a reliable video streaming service. We take advantage of the ability to gradually improve quality which is present in SVC-based HAS to deliver the base layer with higher priority to the clients. This way, when congestion arises, the continuous playout of the base layer can be guaranteed, allowing the provider to offer a reliable service. Within the MISTRAL project, a prototype of this SVCbased HAS client was implemented as well as an intermediary proxy, which is responsible for classifying the requests. Figure 1 shows the demonstration setup where we compare both the SVC-based client with an Apple HLS client, which is a commonly used commercial HAS client. By introducing best effort crosstraffic, the continuous playout of the SVC-based client is compared with the stuttered playback of the standard HAS player, showing the advantages of our approach.