Multiple Sender Distributed Video Streaming Thinh Nguyen (IEEE Member) Avideh Zakhor (IEEE Fellow) IEEE Transactions on multimedia 2004

Outline Introduction Introduction System Overview System Overview Rate Allocation Algorithm Rate Allocation Algorithm Packet Partition Algorithm Packet Partition Algorithm Simulation And Experiment Simulation And Experiment Future work and Conclusion Future work and Conclusion

Introduction Traditional video streaming Sender Video Stream One to many architecture Receiver

Introduction Distributed video streaming Many to one architecture Sender Receiver Packet

Introduction Proposed Distributed video streaming protocol Rate allocation algorithm (RAA) Run at receiver, is used in conjunction with FEC (Forward error correction) to minimize the probability of packet loss in bursty channel environments by splitting the sending rates appropriately across the senders Rate allocation algorithm (RAA) Run at receiver, is used in conjunction with FEC (Forward error correction) to minimize the probability of packet loss in bursty channel environments by splitting the sending rates appropriately across the senders Packet partition algorithm (PPA) Run at individual senders based on a set of parameters estimated at the receiver, ensures that every packet is sent by one and only one sender Packet partition algorithm (PPA) Run at individual senders based on a set of parameters estimated at the receiver, ensures that every packet is sent by one and only one sender

System Overview Sender1 Sender2 Receiver Estimate RTT Estimate loss rates Estimate available bandwidth Rate allocation algorithm Control packet Packet partition algorithm UDP video data

System Overview Every UDP video packet is guaranteed to be sent by one and only one sender Every UDP video packet is guaranteed to be sent by one and only one sender Control packet format Control packet format D1D2S1S2Sync D i : Denote the estimate delay from each sender to receiver S i : Denote the sending rate for each sender Sync : Synchronization sequence number

Rate Allocation Algorithm Why splitting packets across routes can reduce packet loss using FEC ? Why splitting packets across routes can reduce packet loss using FEC ? –Sending packets at higher rate during a congestion period results in larger number of lost packets than sending at a lower sending rate –Because reduces bursty packet, so increases the probability of recovery of the lost packets by FEC –Allows one to recover packets lost on one route using the received packets on the other route

Rate Allocation Algorithm Optimal Rate Allocation Our goal is to find the sending rates Our goal is to find the sending rates –Minimize the probability of irrecoverable loss for a fixed level of FEC –Ensure that each sender sends packets only at available bandwidth N Total number of packets in a FEC block K Number of data packets in a FEC block BmBmBmBm Estimated available bandwidth for sender m in packets per second S Aggregate bit rate of video and FEC in packets per second λ=N/S Interval between successive transmitted FEC blocks in seconds NmNmNmNm Number of packets transmitted by sender m during λseconds

Rate Allocation Algorithm Optimal Rate Allocation P( m, i, N m ) : Denote the probability that i packets are lost out of the N m packets sent by sender m C( K, N A, N B ) : Denote the probability that more than N-K packets are lost out of a total N A +N B packets sent by both senders C( K, N A, N B ) = N A +N B = N, N A /λ<=B A, N B /λ<=B B To find the minimize probability of irrecoverable packet loss

Packet Partition Algorithm Received packets arrive in an interleaved fashion from multiple senders to reduce the startup delay Received packets arrive in an interleaved fashion from multiple senders to reduce the startup delay [n j,k,k’ σ(j)+2D(j)]A k’ (j,k) = P k’ (k) - A k’ (j,k) : difference between arrival and playback time of the kth packet

Packet Partition Algorithm Among all senders j=1, … N, the one that maximizes A k’ (j,k) is assigned to send kth packet Among all senders j=1, … N, the one that maximizes A k’ (j,k) is assigned to send kth packet Each sender keeps track of all the values of A k’ (j,k) for all N senders, and updates every time a packet is sent Each sender keeps track of all the values of A k’ (j,k) for all N senders, and updates every time a packet is sent

Packet Partition Algorithm Synchronize problem Receive the same control packet from receiver Receive the same control packet from receiver Only use the information in the control packet to update Only use the information in the control packet to update Use the same equation to do Use the same equation to do

Packet Partition Algorithm Choice of synchronization sequence number

Fix method: k ” (j) : Estimated sequence number for the latest packet sender j has sent, before receiving the control packet K*(j) : The sequence number for the last packet receiver has received from sender j S : The total sending rate (packets/s) k ” (j) = k*(j) + 2D(j)S K ’ = min j k ” (j)

Simulation and Experiment

Experiment 1 : one sender in Belgium -> UC Berkeley Experiment 2 : two senders in Belgium and Sweden -> UC Berkeley RTTs between Belgium and UC Berkeley is 152 ms RTTs between Sweden and UC Berkeley is 199 ms Average good time : 1s Average bad time : 0.02s FEC Level : RS (60, 46)

Simulation and Experiment

Future work and Conclusion Extend system so that the receiver can dynamically request new senders in order to provide additional bandwidth as required Extend system so that the receiver can dynamically request new senders in order to provide additional bandwidth as required Reduction of packet loss using distributed video streaming scheme over the traditional single path scheme is attributed to the rate allocation between senders, which reduces the bursty loss, hence increasing the error correction capability of FEC Reduction of packet loss using distributed video streaming scheme over the traditional single path scheme is attributed to the rate allocation between senders, which reduces the bursty loss, hence increasing the error correction capability of FEC