Paper review: Quality Adaptation for Congestion Controlled Video Playback over the Internet

Reviewer: Mike Liu

  1. State the problem the paper is trying to solve.
  2. The main problem the paper is trying to solve is the creation of an effective congestion control for streaming video and audio applications on the Internet.
  3. State the main contribution of the paper: solving a new problem, proposing a new algorithm, or presenting a new evaluation (analysis). If a new problem, why was the problem important? Is the problem still important today? Will the problem be important tomorrow?  If a new algorithm or new evaluation (analysis), what are the improvements over previous algorithms or evaluations? How do they come up with the new algorithm or evaluation? 
  4. The main contribution of the paper is that the authors present a mechanism for using layered video in the context of unicast congestion control. The problem the paper addresses is still relevant today in that an efficient mechanism for large amounts of audio and video applications on the Internet has yet to be released and implemented. The problem will continue to be important as we seek to used the Internet for more and more multimedia, interactive applications.
  5. Summarize the (at most) 3 key main ideas (each in 1 sentence.) 
  6. The three 3 key main ideas are: (1) The paper presents a quality adaptation mechanism using layered video, which adds and drops layers of the video stream to perform long-term coarse-grain adaptation, while using a TCP-friendly congestion control mechanism to react to congestion on very short timescales. (2) The mismatches between the two timescales are absorbed using buffering at the receiver and a smoothing parameter for the distribution of buffering among the active layers to trade short-term improvement for long-term smoothing of quality were introduced. (3) They simulated the results of their simulation by obtaining bandwidth traces using their Rate Adaptation Protocol (RAP) in the ns2 simulator and using real Internet Experiments.
  7. Critique the main contribution
  8. What lessons should researchers and builders take away from this work. What (if any) questions does this work leave open?
  9. The lessons researchers should take away from this work are that layered video and audio and its related system of buffering may work as a system for compensating for the bandwidth changes, especially due to congestion control, that may hinder using the Internet for large-scale video and audio applications. The questions the work leaves open are the application of quality adaptation schemes to other congestion control schemes that employ AIMD algorithm, quality adaption with a non-linear distribution of bandwidth among layers, a measurement-based approach of quality adaptation that adjusts Kmax on-the-fly based on the recent history, and the opportunity of proxy caching of multimedia streams.