Application-aware H.264 scalable video coding delivery over wireless LAN: Experimental assessment

This paper is among the first works to document experimental results for application-aware H.264 Scalable Video Coding (SVC) support over Wireless LANs. Application-aware support is achieved by introducing a bandwidth throttling device, called Virtual BottleNeck (VBN), before the WLAN Access Point. Throttling is set to a bandwidth slightly smaller than the actual WLAN capacity (either known or estimated), so that all packet/frame losses occur inside the VBN. Here, loss events are controlled by a scheduling mechanism devised to operate with information taken from the H.264 Network Abstraction Layer Units (NALUs). Despite its relative simplicity, the implemented scheduler exhibits effective video adaptation performance and close to optimal bandwidth efficiency. Setting up the trial was not trivial due to the lack of suitable publicly available tools. We filled this gap by implementing and integrating several separate software modules, e.g., streaming server, NALU dependency filtering, video frame concealment, etc. As a final result, the experimental trial supports the full delivery chain for an SVC stream with the only limitation of an off-line stream conversion for play-out and Peak Signal-to-Noise Ratio (PSNR) measurement purposes, due to the unavailability of real time SVC players.