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

Reviewer : Seh Leng Lim

This paper demonstrates that it is possible to use a quality adaptation mechanism that adds and drops layers of 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.

The main contribution of the paper is its study of the quality adaptation mechanism that bridges the gap between the short-term changes in transmission rate caused by congestion control and the need for stable quality in streaming applications.

The key main ideas expounded are :

(a) appropriate buffer distribution among the active layers

(b) smoothing parameter that allows the server to trade short-term improvement for long-term smoothing of quality

I think that the paper has a significant contribution (rating of 4) to the study of smooth streaming of video over the Internet. However, the approach is rather heuristic and involves tuning the smoothing parameter to fit the network settings. The authors have proposed future studies in the areas of extending the quality adaptation with a non-linear distribution among layers, using a measurement-based approach to adjust the smoothing parameter on the fly, and using quality adaptation in proxy caching of multimedia streams.

Researchers and builders of multimedia applications may have a better appreciation from this paper of the difficulties involved in delivering quality video or audio over the Internet.