Paper review: Quality Adaptation for Congestion
controlled Video Playback over the Internet
Reviewer: Kevin Hofstra
- Video playback over the web
must not only deal with varying bitrates for different customers but also
with fluctuations in bandwidth caused to congestion. What is the best way for having
different quality video for the different bandwidth restrictions of
users? How can the streams be made
to avoid stoppages and degeneration in the event of network congestion?
- This paper presents a
mechanism for using buffered layers of video to present a fluid stream to
many users of differing bandwidths at different qualities. They have a study of how many layers
should be present, how much buffer they should receive and the Kmax that
will provide the most smoothing.
A. The video
will be sent in distinct layers with each layer adding quality when available,
and all streams containing at least the base layer. This allows each user to receive the stream with those that can
handle higher receiving better quality.
This is also important in the case where a high bandwidth user
experiences high congestion, and instead of losing his entire high bandwidth
stream, he loses the added quality layers, while retaining the base stream.
is possible to calculate the Optimal Inter-Layer Buffer Allocation. Efficiency is gained by trying to prevent
the loss of useful buffer when a layer is lost, but still making sure that each
layer is able to buffer enough that it may still be kept for playback.
Kmax factor may contribute to smoothing.
This ensures that a layer is added if and only if it has the
availability of optimal buffer allocation for recovery from Kmax backoffs. We can then prevent the continuous adding
and removing of a layer that is not semi-permanent.
- Critique the main
System researchers and
builders should recognize that streaming video is distributed over many
varying bandwidths, and each also has the possibility of heavy
congestion. In order to ensure a
constant stream, the most effective method is always having a base stream
and adding layers of additional quality when bandwidth or congestion
allow. Further areas of research
that will be needed include the optimal time for additional layers, and
more research into optimizing the buffer across the layers depending on
probability of losing a layer.
4 I believe that they have come
up with some very important theories in how layered video should be
distributed. Although the idea
was already present, I think some of their additions will greatly
increase the functuallity of this method.
- Convincing- 4 I think that is article is also very
convincing. The theory are
soundly based and supported by their simulation. It seems that there is very little to
hide, and although some aspects of the paper seem trivial or assumed,
they are often proved through simulation.