p2p iptv: cmdc polly huang
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P2P IPTV: CMDC
Polly HuangDepartment of Electrical Engineering
National Taiwan University
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OutlineMotivationKey components
Peer capability estimationPeer information exchangeJob schedulingEncoding priority decision
Experimental resultsConclusion
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MotivationAny device can share its content by
Bandwidth peering (P2P network)Computation peering (CMDC)
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Multiple Description Coding MDC-STHI
MDC with Spatial-Temporal Hybrid Interpolation
6420
7531
... ...
... ...
6420... ...1 3 5 7
7531... ...2 4 60
O q
E f
E q
O fAdd redundancy
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Heterogeneity of Mobile IPTV
Ef+Oq Of+Eq
Ef+Of+Eq+Oq
Ef+Oq
Eq+Oq
N1 N2
N3
N4N5
N6
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A Rising ProblemMobile devices as the video sources?
http://www.ithome.com.tw/itadm/article.php?c=44159明年 3.5G上傳頻寬昇級至 1.5M加速 3.5G網路系統頻寬，中華電信與台哥大明年計劃昇級現有網路上傳與下載頻寬，讓使用者可用更短的時間下載或上傳分享影片、音樂。
2007/7/3
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Simple ExperimentsCPU load 0% 20% 40% 60% 80%
F+Q ratio 100% 100% 2% 2% 2%
F ratio 0% 0% 98% 98% 85%
MP4 ratio 0% 0% 0% 0% 13%
Assume the original data is MPEG-4 P4 3.6GHz, 1G Ram, 320x240 WebCam, FPS = 20 Use CPUKiller to control the CPU load Source node tries to do as much as possible
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P-M 1.8G CPUs for cell phones?
Not for now
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CMDC?Source node
MPEG-4
MDC-STHI
MPEG-4+MDC-STHI
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Technical Issues in CMDCWho can do the job?
Peer capability estimationCapability information exchange
How to share the job?Job scheduling
How to decide the transcoding order?Transcoding priority decision
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Source NodeCapability estimation
Periodic probing (every 64 seconds)Encoding type decision
Q+F, F, MPEG-4Bit rate adjustment
Try to fit the available bandwidth
Capability estimation
Encoding type decision
Bit rate adjustment
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Peer Capability EstimationPeriodic probing (every 32 seconds)
Cf = no. of F segments the peer can handle in tswarm
Cq = no. of Q segments
Capability discountThe load of the current tasks must be covered.
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Peer Information Exchange
Consuming Peer
Providing Peer
(1) Buffer map request(including capability)
(2) Buffer map response(including assignment)
(3) Segment request
(4) Segment transmission
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Buffer Map (MDC)Carry 3 kinds of information
MDC typeStatus of the segmentEstimated # of downloads
0 0 00
Ef Eq Of Oq
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Buffer Map (MP4)
We can define arbitrary amount of statusesStatus mapping example
0001 ： (NOASSIGNED) Unable to encode0010 ： (ASSIGNED) The peer will handle this job0011 ： (DOWNLOAD) Downloaded by other peers0100 ： (ENCODE) Currently processing the job0101 ： (SERVER_ASSIGNED) Assigned by the server
No. of downloadsStatus tag
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The Timeline of a Segment
(NOASSIGNED) Unable to encode(DOWNLOAD) Downloaded by other peers(ASSIGNED) The peer will handle this job(ENCODE) Currently processing the job(SERVER_ASSIGNED) Assigned by the server
Issued
No-assign
Download
Assigned
Start encoding
Finish
MDC
MP4
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SchedulingTwo-Phase Scheduling
Providing peer scheduling (phase I) Generate proper buffer map responses
Receiving peer scheduling (phase II) After receiving all the buffer map responses Generate download & encoding plan
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Flow Chart
Consuming peer
Providing peer
(1) Buffer map request(including capability)
(2) Buffer map response(including assignment)
(3) Segment request
(4) Segment transmission
Phase-I Scheduling
Phase-II scheduling
Encodingpriority
decision
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PlanetLab Experiments100 peers420Kbps video (MDC F+Q 530Kbps)Each experiment lasts 5400 secondstswarm = 4 secondsMembership size = 8 – 11 peersPartnership size = 6 partners
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Continuity Index
PCFast NB
Slow PCNB
Slow NBPDA
Smart Phone
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Buffer Level
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Computation Load
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With Heterogeneous PeersPeers with different computing power
Strong peers: Finish one segment in 2.0-2.5 seconds
Weak peers: Finish one segment in 12.0-12.5 seconds
Different ratio of strong/weak peers are mixed
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Continuity Index
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Buffer Level
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Computation Load
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Questions?