1. Social Media: YouTube as a Case

2. 2 New generation of video sharing service Feb.15th, 2005 Some statistics: 60 hours video uploaded very minute 4 billion views daily (Jan 2012) 14 billion videos viewed (May 2010) 20% growth per month 3 rd most visited site (behind Google and Facebook) 43% market share

3. 3 Background Web 2.0 and UGC Web 2.0 Facebook, Flickr, Google Map, etc. User Generated Content Communities, Social network

4. 4 YouTube Challenges Client/Server architecture Bandwidth costs 20% of all HTTP traffic, 10% of all traffic on the Internet Traffic Cost: $11 million per month (assume $10 per Mbps) Sold to Google for $1.65 billion on Nov.13th, 2006 Scalability and performance “Slow, 69% other are faster” (Alexa.com)

5. 5 YouTube Meta-Data Are YouTube videos different from traditional videos?

6. 6 Statistics of YouTube Videos Video Category Highly skewed

7. 7 Statistics of YouTube Videos Date Added Increasing steeply

8. 8 Statistics of YouTube Videos Video Length Most distinguished Short video clips 97.9% ≤ 600s, 99.1% ≤ 700s Due to the 10 minutes limit Now 15 mins Unlimited for power users Three peaks Different from traditional videos 1-2 hour movies

9. 9 Statistics of YouTube Videos Video File Size 98.3% less than 25 MB average 8.4 MB Millions of videos ! Video Bitrate Most around 330 kbps

10. 10 YouTube Video Format Initially, 320x240 pixels, Sorenson Spark codec (H.263),with mono MP3 audio June 2007, 3GP format on mobile phones March 2008, 480x360 November 2008, 720p HD, 4:3 aspect ratio to a widescreen 16:9 H.264/MPEG-4 AVC November 2009, 1080p HD July 2010, 4K format: 4096x3072 YouTube accepts upload in most container formats and performs conversion

11. 11 Statistics of YouTube Videos Views Long-tail Does not fit Zipf’s Not so many unpopular videos (i.e., views fewer than 100) Gamma, Weibull Zipf’s Website access VoD

12. 12 Statistics of YouTube Videos Ratings and comments Still, users are more willing to watch videos rather than to log in to rate and make comments User Friends Average: 4.3, Median: 0 58% no friends

13. 13 Social Network of YouTube Videos Videos are no longer independent Small-World Phenomenon Refer to the principle that people are linked to all others by short chains of acquaintances (AKA. six degrees of separation) Clustering coefficient Much larger than that of a random graph with the same number of vertices and average number of edges per vertex Characteristic path length Almost as small as that for the corresponding random graph

14. 14 Social Network of YouTube Videos Small-World in YouTube Strong small-world characteristics

15. 15 Social Network of YouTube Videos Implication for Caching and Storage Correlation between videos A user is likely to watch another video in the group after finishing the first one