Content aware packet scheduling in peer-to-peer video streaming By: Reza Motamedi Advisor: Hamid Reza Rabiee

2 DML P2P Live Video Streaming DML P2P Live Video Streaming 2 Outline  Scheduling in file sharing vs. stream trading  Scheduling in sender vs. scheduling in receiver  Content aware scheduling  Design choices of a P2P streaming application  Mesh or Tree  Scheduling  Video Coding  Problem Definition

3 DML P2P Live Video Streaming DML P2P Live Video Streaming 3 Scheduling in P2P Networks  File sharing, Bit Torrent (as one of the most prosperous file sharing protocols)  Tit-for-Tat: trading chunks. A mechanism to provide incentive  Rarest chunk first: spread those parts of the file that are rare in the network.  Question: How can these strategies be used in case of P2P media streaming?

4 DML P2P Live Video Streaming DML 4 Live Media Streaming  All peers are interested in a small part of the stream. (interested chunks are limited)  Trading chunks (Tit-for- Tat) is barely applicable  Strict timing constraints  A chunk is of no use when it’s play back has passed. File Sharing  A large file is to be transferred  No temporal dependencies  Nothing happens in case the last portion of file gets to receiver earlier that initial portion. Live Media Streaming vs. File Sharing

5 DML P2P Live Video Streaming DML 5 In sender  Actually applicable when tree is used.  Single sender  Also called “PUSH”  Decision  What to send  When to send  Whom to provide with stream (incentive) In receiver  Applicable in case more that one data provider are available  mesh  Multiple sender  “PULL”  Decision  What to request  Whom to ask for the stream Scheduling

6 DML P2P Live Video Streaming DML P2P Live Video Streaming 6 Content Aware Scheduling  Not all packets transferred in the system are the same:  Packets may belong to different frames of a GoP  Packets may belong to different layers (if layered coding is used)  Better result can be achieved when this difference among different packets can be taken into consideration.

P2P Streaming Design Choices

8 DML P2P Live Video Streaming DML 8 MDC  Stream is divided into sub- streams  No strict dependency among different dependency  The more description you receive, the better is the playback quality  Each single description is solely decodable  Large overhead Layered  Stream is divided into sub- streams  Strict dependencies among different layers  Smaller overhead  H 264/SVC (Scalable Video Coding) Smaller number of layers (6 layers)  H 264/FGS (Fine Granular Scalability) Larger number of layers (up to 20 layers) Coding Technique?

9 DML P2P Live Video Streaming DML P2P Live Video Streaming 9 Where to Perform Scheduling?  Tree:  Schedule base layer packets in the sender  Mesh:  Schedule enhancement layers packet request in the receiver  Sender can also schedule which receiver to serve to exert an incentive

10 DML P2P Live Video Streaming DML P2P Live Video Streaming 10 What to Trade?  Sub-stream trading  Scheduling stream chunks  Chunks of different descriptions or layers  Chunks of same description or layer with different time lags  Scheduling a GoP  Scheduling single frames  Monitor links to detect failures and request those parts you have missed

P2P Streaming Problem Definition

12 DML P2P Live Video Streaming DML P2P Live Video Streaming 12 Problem Definition (receiver side scheduler)  x sn =1: sub-stream s is going to be requested from peer p  S : all streams  S n : Set of all available layer chunks in the partner n  w s : weight given to each sub-stream.  Rank your partners. Request commensurate to your previous upload to each of your partners.

13 DML P2P Live Video Streaming DML P2P Live Video Streaming 13 Problem Definition (receiver side scheduler)  Can be solved as classical maximum weight matching in bipartite graph.  Weight:  MDC: w s =1  Layerd w s =2 S-s, Where s= 1,…,S

14 DML P2P Live Video Streaming DML P2P Live Video Streaming 14 Problem Definition (sender side scheduler)  Distribution of outgoing bandwidth among peers: a mechanism to provide incentive  Balancing data emission of base and enhancement layers

15 DML P2P Live Video Streaming DML P2P Live Video Streaming 15 Problem Definition (sender side scheduler)  a i,j =1: j th request from partner i is going to be replied.  c(i,j,l,t): gain attained from replying a request.  T: all requests for base layer  N: all partners  R i : all n i ’s requests  S n : partner n’s share  D j : request j’s delay  TD j : bearable delay for request j

16 DML P2P Live Video Streaming DML P2P Live Video Streaming 16 Gain Function  Defines importance of a layer chunk  l: total number of layers a partner receives  j: request is for layer number j  TD i : deadline for request i  t: current time

17 DML P2P Live Video Streaming DML P2P Live Video Streaming 17 Future Works  Tuning layer chunks’ weight  Including distortion information into Gain Function  Considering incentive

Q&A