| The great advances in wireless communications over the past years facilitate the wireless video transmission in real-time basis. However, wireless video transmission still needs high capacity channels and good techniques that mitigate the error-prone wireless channels effect. Recently, different techniques have been proposed for efficient real-time video streaming over wireless and heterogeneous networks. The Scalable Video Coding (SVC) or layer coding is proposed to achieve graceful degradation for video quality in lossy transmission environments by dropping part of the enhancement layers without reencoding. SVC faces the problem of unequal layer protection, where the base layer, inside sub-stream, may be dropped while the enhancement layer could be dropped first. Furthermore, the whole scalable layer may be dropped while there is a chance to drop packet by packet. These limitations lead to a significant effect on the graceful degradation mechanism. In this paper, an application-layer and middleware-based solution is proposed to implement SVC, which increases network reliability, flexibility and provides Quality of Service (QoS) control. Specifically, due to the real-time and QoS support of Data Distribution Service (DDS) middleware, it is used to implement the four types of SVC scalability, Viz. Temporal, Spatial, Quality and Combined Scalability. Furthermore, an open source evaluation tool called Scalable Video-streaming Evaluation Framework (SVEF) is used to assess the video transmission performance, with performance metrics, Viz. Peak Signal to Noise Ratio (PSNR), Mean Opinion Score (MOS), frames delay and jitter. The experiments' results show a graceful degradation to the video quality when using the DDS-based SVC, especially when the number of receivers are increased. Furthermore, we notice that the video quality is sensitive to the encoding type, thus, SNR performs better due to the efficient encoding, which leads to the smallest video encoding size and packet size. |
