HTTP-based Video Streaming

Confused, Timid, and Unstable: Picking a Video Streaming Rate is HardTe-Yuan Huang, Nikhil Handigol, Brandon Heller, Nick McKeown, Ramesh Johari

Experimental Setup

The$Internet$

Video Client

The$Internet$

Bandwidth$Controller$

CDN$1$

CDN$2$

CDN$3$

Content$Distribu9on$Networks$

CDN A

Get File 1 (1750kb/s), Chunk 1

Serve the video with quality 1750kb/s

Playout Buffer Standardized, commoditized HTTP servers

Videos are pre-encoded and deployed in CDNs

Rate selection logic resides at the client side

File%1:%

File%2:%

1750% 1750%

1050% 1050%

Problem

0 100 200 300 400 500 600 700 800 900Time (s)

235375560750

105014001750

2500

3000

4000

5000

kb/s

Avai

labl

e Vi

deo

Rat

e

Video Flow Throughput

Competing Flow Throughput

Video Rate

Fair Share

In the presence of a completing flow, video quality steps down all the way to the lowest

Why? Here is the answer!

Download and

MeasurePick a Rate

Initial Bitrate

BandwidthEstimation

Video Rate for the Next Chunk

Bandwidth Under-estimation: The ON-OFF traffic pattern periodically resets TCP congestion window.Pick a Rate Conservatively: Since the estimated bandwidth typically is not equal to the actual bandwidth, video clients tend to pick a rate conservatively.Lower Rate means Smaller Chunk: Requesting a smaller chunk means a lower probability to obtain fair share. More information? Read our paper!

http://www.stanford.edu/~huangty/IMC.pdfRecipient of IETF/IRTF Applied Network Research Prize

BandwidthUnder-estimation Conservatively

Request for a smaller chunk

Video Client

Competing Flow Generator