Approaches to adaptive bitrate video streaming

Cahir, Conor (2014) Approaches to adaptive bitrate video streaming. MSc(R) thesis, University of Glasgow.

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Abstract

In this work, I use ns-3 simulations to compare and evaluate different approaches to web based adaptive bitrate (ABR) video streaming. In particular, I look at the difference between client pull and server push based approaches, the effects of media formatting parameters such as chunk duration and number of encoding rates, and the implementation of bandwidth estimation and request scheduling strategies. I find that client pull applications with a 2 second chunk duration are very inefficient with bandwidth compared to applications using a server push based approach. The reasons for this stem from the effect of frequent idle periods at chunk boundaries, which are absent with server push, on the behaviour of TCP. Increasing the chunk duration to 10 seconds makes a significant difference to client pull applications and allows them to perform at a level much more comparable with server push applications. I also find that ABR applications in general are vulnerable to suffering from encoding rate instability, a result that echoes findings from a number of recent studies. This problem seems to stem from the difficulty of selecting a suitable encoding rate based on transfer rates observed at the application layer. Effective remedies for encoding rate instability include ensuring that the system is not over provided for in terms of the number of available encoding rates, and using an averaging function, such as the harmonic mean, over a series of recent transfer rates in order to filter out short term fluctuations in the estimate of available bandwidth. I also show that a simple request scheduling strategy can be used to avoid over buffering and the associated problems, but that periodic request scheduling can introduce further problems related to fairness when multiple ABR flows compete. Finally, I show that a hybrid of client pull and server push, which I call pull selective, can offer a useful compromise between the two, by matching the performance characteristics of server push whilst maintaining the low server overheads and scalability attributes of client pull.

Item Type: Thesis (MSc(R))
Qualification Level: Masters
Keywords: abr dash dynamic adaptive video streaming http Ns3 ns-3 simulation
Subjects: Q Science > QA Mathematics > QA75 Electronic computers. Computer science
Q Science > QA Mathematics > QA76 Computer software
Colleges/Schools: College of Science and Engineering > School of Computing Science
Funder's Name: UNSPECIFIED
Supervisor's Name: Perkins, Dr. Colin
Date of Award: 2014
Depositing User: Mr Conor Cahir
Unique ID: glathesis:2014-5093
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 10 Apr 2014 10:25
Last Modified: 10 Apr 2014 10:25
URI: http://theses.gla.ac.uk/id/eprint/5093

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