Non-Packet-Loss-based Rate Adaptive Video over the Internet

Introduction: Knowledge of the network state allows transcoder adaptation of a pre-encoded video bit rate by varying the re-quantization parameter. In TCP-Friendly Rate Control (TFRC) [1], which is now an RFC, an equation captures the network state, determining congestion primarily from packet loss events. However, packet loss of intra-coded pictures leads to progressive deterioration of a video sequence group of pictures (GOP). Ideally, a more sensitive measure of congestion is required, which is not reactive to rather limited information conveyed by packet loss. The system should also be a good neighbour to co-existent TCP traffic on the same link, as TCP uses cooperative congestion control. This letter proposes a non-packet-loss-based measure of congestion that forms, along with its rate of change, an input to a fuzzy logic controller. A transcoder changes the encoded video bit rate to the rate determined by the fuzzy controller. It is the combination of transcoder and fuzzy logic controller that makes the system as a whole robust to the non-linearities present in congestion control feedback loops. These results show that the fuzzy control scheme adapts the video rate to the available bandwidth in the face of a typical mix (as determined by measurement studies) of Internet traffic, with behaviour that is comparable to TFRC. TFRC [1] itself is not adapted to variable bit rate (VBR) video, using fixed sized packets, whereas the received video quality from the fuzzy controlled transcoder system gracefully degrades in response to increasing background traffic, as a result improving the subjective viewing experience.