How to Meet the Deadline for Packet Video
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Transcript of How to Meet the Deadline for Packet Video
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How to Meet the DeadlineHow to Meet the Deadlinefor Packet Videofor Packet Video
Bernd GirodBernd Girod
Mark KMark KalmanalmanEric SettonEric Setton
Information Systems LaboratoryInformation Systems LaboratoryStanford UniversityStanford University
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22B. Girod: Packet Video 2006
[Economist, September 2005]
THE MEANING OF FREE SPEECH
The acquisition by eBay of Skype is a helpful reminder to the world's trillion-dollar telecoms industry that all phone calls will eventually be free . . .
. . . Ultimately—perhaps by 2010—voice may become a free internet application, with operators making money from related internet applications like IPTV . . .
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33B. Girod: Packet Video 2006
IPTV is Becoming a Reality IPTV is Becoming a Reality
SBC (ATT)18M IPTV householdsby 2007
Verizon10M IPTV households
by 2009
[IEEE Spectrum, Jan. 2005]
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44B. Girod: Packet Video 2006
Why Is Internet Video Hard?Why Is Internet Video Hard?
Internet is a best-effort network . . .
Congestion Insufficient rate to carry all trafficPacket loss Impairs perceptual qualityDelay Impairs interactivity of services;
Zapping < 500 ms
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55B. Girod: Packet Video 2006
How to Meet the Deadline for Packet VideoHow to Meet the Deadline for Packet Video
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66B. Girod: Packet Video 2006
Internet
How to Meet the Deadline for Packet VideoHow to Meet the Deadline for Packet Video
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77B. Girod: Packet Video 2006
How to Meet the Deadline for Packet VideoHow to Meet the Deadline for Packet Video
• Congestion, QoS, and “fair” sharing• Maximum-utility resource allocation for
multiple video streams• Example: video over wireless home
networks• Congestion-distortion optimized packet
scheduling (CoDiO)• Example: P2P multicasting of live video• Packet scheduling for multicast trees
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88B. Girod: Packet Video 2006
Measuring CongestionMeasuring Congestion
Traffic flow
E[Delay]“Congestion”
Congestion in packet-switched network: queuing delay that packets experience, •weighted by size of the packet•averaged over all packets in the network
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99B. Girod: Packet Video 2006
Congestion GrowsCongestion GrowsNonlinearly with Link UtilizationNonlinearly with Link Utilization
Congestion [seconds]
Rate R
Example: M/M/1 model
1 = C-R
C
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1010B. Girod: Packet Video 2006
1.22 MTURRTT p
How 1B Users Share the InternetHow 1B Users Share the Internet
maximum transfer
unit
roundtrip time
packetloss rate
data rate
[Mahdavi, Floyd, 1997][Floyd, Handley, Padhye, Widmer, 2000]
Rate R
Growing congestion
p0.0010.0001 0.10.01
TCP Throughput
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1111B. Girod: Packet Video 2006
QoS vs. Best EffortQoS vs. Best EffortReservation-ism
– Voice and video need guaranteed QoS (bandwidth, loss, delay)
– Requires admission control: “Busy tone” when network is full
– Best effort is fine for data applications
Best Effort-ism– Best Effort good enough for
all applications– Real-time applications can
be made adaptive to cope with any level of service
– Overprovisioning always solves the problem, and it’s cheaper than QoS guarantees
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1212B. Girod: Packet Video 2006
Simple Model of A Shared LinkSimple Model of A Shared Link• Link of capacity C is shared among k flows
• Fair sharing: each admitted flow uses rate R=C/k• Homogeneous flows with same utility function u(R)• Total utility
C
CU k k u R k uk
[Breslau, Shenker, 1998]
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1313B. Girod: Packet Video 2006
Rigid ApplicationsRigid Applications• Utility u=0 below of
minimum bit-rate B
• Admit at most flows
• With sufficient overprovisioning, no admission control needed, since
u
C/kCkB
B
1
Pr 0CkB
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1414B. Girod: Packet Video 2006
Elastic ApplicationsElastic Applications
• Elastic applications: convex utility function u(R)
• All flows should be admitted: best effort!
R
u(R)
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1515B. Girod: Packet Video 2006
0 500 1000 1500 2000 2500 3000 3500 400024
26
28
30
32
34
36
38
40
42
44
Y-P
SN
R in
dB
encoding rate in kbps
mobileforeman
QoS vs. Best Effort for VideoQoS vs. Best Effort for Video• H.264 video coding for 2
different testsequences• Video is elastic application
. . . above a certain minimum quality
• Bottleneck links: admission control and dynamic rate control combined
• Rate must be adapted to network throughput. How?
• Utility function depends on content: should use unequal rate allocation
Foreman
Mobile
Goodpicturequality
Badpicturequality
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1616B. Girod: Packet Video 2006
• Better than utility-oblivious “fair” sharing
• With rk>=0 Karush-Kuhn-Tucker conditions
Different Utility FunctionsDifferent Utility Functions
rk
uk Equal-slope “Pareto condition”
Vilfredo Pareto1848-1923
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1717B. Girod: Packet Video 2006
Distribution of TV over WLANDistribution of TV over WLAN
[courtesy: van Beek, 2004]
5 Mbps
2 Mbps
11 Mbps
Home MediaGateway
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1818B. Girod: Packet Video 2006
Video over WLANVideo over WLAN
Decoder
Transcoder
Controller
802.11b
Wireless Terminal
NetworkInterface playout
buffer
Video encoded at higher rate
Receiver
[Kalman, van Beek, Girod 2005]
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1919B. Girod: Packet Video 2006
Video over WLAN with Multiple StreamsVideo over WLAN with Multiple Streams
DecoderTranscoder
Controller
Wireless terminals
NetworkInterfaceTranscoder
Transcoder
…
…
… Decoder
Decoder
…
c0
c1
cM
0
1
M
0
1
M
Receiver
(Multi-Channel)
[Kalman, van Beek, Girod 2005]
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2020B. Girod: Packet Video 2006
1 2 3 4 55
10
15
20
25
30
35
40
45
time in seconds
Y-P
SN
R in
dB
Dynamic Estimation of R-D CurveDynamic Estimation of R-D Curve
Parameters track weighted average of last I-Frame, P-Frame and B-Frame
Scene cuts
[Stuhlmüller et al. 2000]
00
D DR R
R-D Model
Rate
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2121B. Girod: Packet Video 2006
0 5 10 15 20 25 300
2000
4000
chan
nel c
apac
ity in
kbs
0 5 10 15 20 25 300
0.5
1
chan
nel-t
ime
allo
catio
n
0 5 10 15 20 25 300
1000
2000
trans
code
d
rate
in k
bps
0 5 10 15 20 25 300
5
10
15
back
log
in
fram
es
0 5 10 15 20 25 3010
20
30
40
50
Y-P
SN
R in
dB
time in seconds
Mean PSNR: 31 dB
802.11b Transmission of 2 Video Streams802.11b Transmission of 2 Video StreamsLink
rates[kbps]
Channeltime
allocation
Transcoderbit-rate[kbps]
Backlogin frames
PSNRin dB
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2222B. Girod: Packet Video 2006
Video Distortion with SelfVideo Distortion with Self CongestionCongestion
GoodPicturequality
Badpicturequality
Bit-Rate [kbps]
Self congestioncauses late loss
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2323B. Girod: Packet Video 2006
Effect of Playout Delay and Loss Sensitivity Effect of Playout Delay and Loss Sensitivity
Foreman Salesman
Simulations over ns-2 Link capacity 400 kb/s
40% headroom 10%
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2424B. Girod: Packet Video 2006
1 sender
380 kbps, 36 dBHighest sustainable video quality
420 kbps, 33.7 dB
Simulation of 600 kbps link Latency 400 msec
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2525B. Girod: Packet Video 2006
Modeling Self-CongestionModeling Self-Congestionfor Packet Schedulingfor Packet Scheduling
Prob
abili
ty
dist
ribut
ion
delay
• Rate-distortion optimized packet scheduling (RaDiO) typically assumes independent delay pdfs for successive packet transmissions [Chou, Miao, 2001]
• Model delay pdf by exponential with varying shift
[Setton, Girod, 2004]
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2626B. Girod: Packet Video 2006
CoDiO Light SchedulerCoDiO Light Scheduler
I B B B P
BIBB
P
Pictures to send ScheduleI P B BBP I BBB I
B
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2727B. Girod: Packet Video 2006
CoDiO Scheduling PerformanceCoDiO Scheduling Performance
Simulations over ns-2 Packet loss rate 2%Bandwidth 400 kb/s
Propagation delay: 50ms
30 %25 %
Mother & Daughter News
Playout deadline (s) Playout deadline (s)
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2828B. Girod: Packet Video 2006
H.264/AVC @250 kb/sLink rate 400 kb/s, propagation delay 50 ms
2 % packet loss0.6 second playout deadline
CoDiO ARQ
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2929B. Girod: Packet Video 2006
Sequence: ForemanPacket loss rate 2%
Link capacity 400 kb/sPropagation delay: 50ms
60 %
Playout deadline (s)
Playout deadline (s)
Playout deadline (s)
CoDiO vs. RaDiOCoDiO vs. RaDiO
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3030B. Girod: Packet Video 2006
Video Multicast over P2P Networks Video Multicast over P2P Networks Challenges• Limited bandwidth • Delay due to multi-hop transmission• Unreliability of peersOur Approach [Setton, Noh, Girod, 2005]• Determine encoding rate as a function of
network bandwidth• Build and maintain complementary
multicast trees• Adapt media scheduling to network
conditions and to content• Request retransmissions to mitigate lossesRelated work• [Chu, Rao, Zhang, 2000]• [Padmanabhan, Wang and Chou, 2003]• [Guo, Suh, Kurose, Towsley, 2003]• [Cui, Li, Nahrstedt, 2004]• [Do, Hua, Tantaoui, 2004]• [Hefeeda, Bhargava, Yau, 2004]• [Zhang, Liu, Li and Yum, 2005]• [Zhou, Liu, 2005]• [Chi, Zhang, Packet Video 2006]
… …Video stream
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3131B. Girod: Packet Video 2006
Experimental SetupExperimental Setup• Network/protocol simulation in ns-2
– 300 active peers – Random peer arrival/departure
average life-time 5 minutes– Over-provisioned backbone– Typical access rate distribution– Delay: 5 ms/link + congestion
• Video streaming– H.264/AVC encoder @ 250 kb/s– 15 minute live multicast
[Sripanidkulchai et al., 2004]
Downlink Uplink Percentage 512 kb/s 256 kb/s 56% 3 Mb/s 384 kb/s 21%1.5 Mb/s 896 kb/s 9% 20 Mb/s 2 Mb/s 3% 20 Mb/s 5 Mb/s 11%
[Setton, Noh, Girod, 2005]
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3232B. Girod: Packet Video 2006
Join and Rejoin LatenciesJoin and Rejoin Latencies
Simulations over ns-2, 300 peersNumber of trees: 4
Retransmissions enabled[Setton, Noh, Girod, 2005]
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3333B. Girod: Packet Video 2006
CoDiO retransmissions No retransmissions
P2P Video Multicast: 64 out of 300 Peers
H.264 @ 250 kb/s2 second playout deadline for all streams
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3434B. Girod: Packet Video 2006
P2P Video Multicast: 64 out of 300 PeersP2P Video Multicast: 64 out of 300 Peers
H.264 @ 250 kb/s2 second playout deadline for all streams
CoDiO retransmissions No retransmissions
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3535B. Girod: Packet Video 2006
CoDiO Scheduling for Multicast TreesCoDiO Scheduling for Multicast Trees
Parent
PI B P B P BDI DB DP3 DP2 DP1DB DB
min.E D min.Treesize E D [Setton, Noh, Girod, 2006]
Child
Child
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3636B. Girod: Packet Video 2006
Gain by Multicast CoDiOGain by Multicast CoDiO
Simulations over ns-2, 300 peers Number of trees: 4
Retransmissions enabled
30 %40 %
Foreman Mother & Daughter
Playout deadline (s) Playout deadline (s)
[Setton, Noh, Girod, 2006]
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3737B. Girod: Packet Video 2006
Sender-driven CoDiO light33.71 dB
Without prioritization30.17 dB
H.264 @ 250 kb/s0.8 second playout deadline for all streams
Average Video Sequence for 75 Peers
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3838B. Girod: Packet Video 2006
ConclusionsConclusions• Must avoid congestion for low latency• Video streaming over bottlenecks (IPTV, WLAN . . . ):
combine admission control and rate control• R-D-aware rate allocation better than fair sharing• Packet scheduling should consider congestion rather than rate• Low-complexity CoDiO scheduler• P2P video multicast possible with low latency• Retransmissions effective with application-layer multicast• CoDiO extended to packet scheduling for multicast trees
Cross-layer paradigm Media-aware transport superior system performance
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The EndThe Endhttp://www.stanford.edu/~bgirod/publications.htmlhttp://www.stanford.edu/~bgirod/publications.html