Streaming Media Distribution Techniques

1. Streaming Media Distribution Techniques Jie Huang Class Presentation for CSE581 Internet Technology

2. Papers • Broadcasting on Isochronous channels • Skyscraper Broadcasting: A New Broadcasting Scheme for Metropolitan Video-on-Demand Systemsby Kien A. Hua and Simon Sheu, Univ. of Central Florida • Scalable On-Demand Media Streaming with Packet Loss Recoveryby Anirban Mahanti, Derek L. Eager, Mary K. Vernon, and David Sundaram-Stukel, Univ. of Saskatchewan and Univ. of Wisconsin • Caching in the Internet • Caching Techniques for Streaming Multimedia over the Internetby Markus Hofmann, T.S. Eugenne Ng, Katherine Guo, Sanjoy Paul, and Hui Zhang, Bell lab and Carnegie Mellon Univ. CSE581 Streaming Media Distribution Techniques

3. Measurements for Video-on-Demand • Server bandwidth • Client bandwidth • Client buffer space • Startup Latency CSE581 Streaming Media Distribution Techniques

4. Broadcasting Schemes • Periodic Broadcast Server centered (server bandwidth) • Pyramid Broadcasting (PB) • Permutation-Based Pyramid Broadcasting (PPB) • Skyscraper Broadcasting (SB) • Reliable Periodic Broadcast (RPB) • Bandwidth Skimming A client merging technique, client centered (client bandwidth, startup latency) • Simple Bandwidth Skimming • Reliable Bandwidth Skimming CSE581 Streaming Media Distribution Techniques

5. Pyramid Broadcasting 1 αα2 α3 α4 Video 1 5 1 2 3 4 Video 2 1 2 3 4 5 Channel bandwidth Server bandwidth CSE581 Streaming Media Distribution Techniques

6. Pyramid Broadcasting (cont.) At the client side: • Download the next segment at the earliest possible time after beginning to play the current segment • Play time for segment i must be longer than the longest waiting time for the start of segment i+1 • At most two concurrent channels! Channel bandwidth > play rate • High network and disk bandwidth • Large buffer, 70% of the length of the video CSE581 Streaming Media Distribution Techniques

7. Permutation-based Pyramid Broadcasting • Smaller transmission bandwidth reduces disk bandwidth and space requirement • Large latency • Number of channels is limited to 7 CSE581 Streaming Media Distribution Techniques

8. Skyscraper Broadcasting 1 2 2 5 5 Video 1 Video 2 Channel bandwidth = play rate Even group Odd group Server bandwidth CSE581 Streaming Media Distribution Techniques

9. At the client side Receiving segments in terms of transmission group A group consists of consecutive segments having the same sizes A group is downloaded in its entirety, in the segment order Skyscraper Broadcasting (cont.) • At most two groups are being downloaded at the same time • Maximum bandwidth requirement = 2 * play rate • Maximum buffer space = longest segment size – first segment size CSE581 Streaming Media Distribution Techniques

10. Skyscraper Broadcasting (cont.) • Segment size restriction • No segments larger than W times the size of the first segment • Small buffer space prefers small W • (W-1)* first segment size • Low startup latency prefers large W • large W means small first segment size CSE581 Streaming Media Distribution Techniques

11. Skyscraper Broadcasting (cont.) • Choosing W allows flexibility • achieve latency of PB and buffer space of PPB CSE581 Streaming Media Distribution Techniques

12. Original data 1 2 3 4 ... Stretched data e d f g h a b c e Reconstructed original data 1 2 3 4 Reliable Periodic Broadcast • Loss Recovery • Digital Fountain: loss recovery without retransmission Any four packets received d b c f CSE581 Streaming Media Distribution Techniques

13. Reliable Periodic Broadcast (cont.) • Each segment is delivered by an approximation of a digital fountain • Receive an entire segment before playing it • ! latency performance is competitive with Skyscraper • Low latency comes from: • A client can begin receiving immediately • The maximum possible segment size increase • The client will receive an entire segment just in time to begin playing it CSE581 Streaming Media Distribution Techniques

14. Reliable Periodic Broadcast (cont.) • Comparison with Skyscraper • K: total number of segments number of channels available for a video sever bandwidth = K*r • r: segment transmission rate (in playback rate) • s: maximum number of streams clients listen to • lk: length of the kth segment relative to segment 1 • D: video length (in playback time) • D1: segment 1 length (in playback time) r = 1, s = 2 in Skyscraper, which makes the RPB length progression a Fibonacci series. CSE581 Streaming Media Distribution Techniques

15. Reliable Periodic Broadcast (cont.) • Latency depends on D1 • SB: D1/2 • RPB: D1 • D1 = D / Σlk • For a certain server bandwidth, K is fixed • So D1 depends on how the segment sizes increase CSE581 Streaming Media Distribution Techniques

16. Reliable Periodic Broadcast (cont.) • Price of low latency • Buffer size CSE581 Streaming Media Distribution Techniques

17. Bandwidth Skimming • Client merging: a new client listens to its own new stream as well as the most recently initiated on-going stream that it can merge with. CSE581 Streaming Media Distribution Techniques

18. Bandwidth Skimming (cont.) • Emphasis on client bandwidth < 2*play rate • e.g. client bandwidth = 1.33*play rate in 4 channels CSE581 Streaming Media Distribution Techniques

19. Bandwidth Skimming (cont.) • Reserve a small skim of client reception bandwidth to support substantial reduction in server and network bandwidth • Skim can be tuned to provide the trade-offs between playback quality and required server bandwidth CSE581 Streaming Media Distribution Techniques

20. Reliable Bandwidth Skimming • Divide the media stream into segments that have fixed duration • Each segment is stretched using erasure codes • For each segment, the server transmits a rate 1.0 primary stream and a rate p/(1-p) secondary stream • The secondary stream is offset in time by the segment duration • Merge secondary streams as well as the primary streams CSE581 Streaming Media Distribution Techniques

21. Caching Techniques for Streaming Media • Segmentation of Streaming Objects • rather than all-or-nothing • Dynamic Caching • like a ring buffer • Self-organizing Cooperative Caching • helper machines inside the network CSE581 Streaming Media Distribution Techniques

22. Summary • Broadcasting schemes • Periodic Broadcast • Pyramid Broadcasting (PB) • Permutation-Based Pyramid Broadcasting (PPB) • Skyscraper Broadcasting (SB) • Reliable Periodic Broadcast (RPB) • Bandwidth Skimming • Simple Bandwidth Skimming • Reliable Bandwidth Skimming • Caching techniques for streaming media CSE581 Streaming Media Distribution Techniques