video on demand
DESCRIPTION
Video On Demand. Video on Demand. One video server Many video data Many clients Client want to watch at any time. Assumptions. Constant bitrate stream Perfect network transport. Unicast Solution. One channel per client No start-up latency No client buffer Low client bandwidth - PowerPoint PPT PresentationTRANSCRIPT
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Video On Demand
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Video on Demand
One video serverMany video dataMany clientsClient want to watch at any time
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Assumptions
Constant bitrate streamPerfect network transport
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Unicast Solution
One channel per clientNo start-up latencyNo client bufferLow client bandwidthLarge server bandwidth Not scalable
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Multicast Solution
Batching aggregate client requests serve using multicast clients have to wait No client buffer Low client bandwidth
“Scheduling Policies for an On-Demand Video Server
with Batching”
Dan, Sitaram, Shahabuddin, IBM
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Multicast Solution
User-centered approachScheduling data based on user requests
Data-centered approachDon’t care about userJust broadcast popular video
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Multicast Solution
BatchingStaggered Broadcast
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Staggered Broadcast
Video
C0
C1
C2
:
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Staggered Broadcast
2 hour video5 minutes waiting timeNumber of channels =
2 x 60 / 5 = 24
Required bandwidth =
1.5Mbps x 24 = 36Mbps
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Multicast Solution
BatchingStaggered Broadcast
clients have to waitNo client bufferLow client bandwidthHuge server bandwidth
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Multicast Solution
BatchingStaggered BroadcastPeriodic Broadcast
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Periodic Broadcast
Video
C0
C1
C2
:
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Pyramid Broadcast
Video
C0
C1
C2
:
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Pyramid Broadcast
Video
C0
C1
C2
:
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Analysis of Pyramid Broadcast
Notations B : Total available bandwidth Bv : Bandwidth of video
Tv : Total length of each video K : Number of segments per video
Ti : Length of segment i : Factor in geometric series
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Channel Bandwidth
i
i+1 i+1
playback time = Ti
download time = Ti+1Bv/Bi
Download time for segment i+1 needsto be smaller than Ti for it to arrive in time.
D’oh!Just miss it!
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Channel Bandwidth
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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= 2
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Start-up Latency
Worst case waiting time =
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Optimal
2.5
T1
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Storage Requirements
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Pyramid Broadcast
Large client bandwidth (KBv)
Huge client buffer (70–80% Tv)
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Permutation-based Pyramid Broadcast
C0
C1
C2
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Channel Bandwidth
i
i+1 i+1
playback time = Ti
download time = Ti+1Bv/Bi
X needs to be smaller than Ti for segment i+1 to arrive in time.
D’oh!Just miss it!
i+1 i+1
X
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Channel Bandwidth
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Client Latency
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Storage Requirement
One channel at a timeCan pause and wait
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Storage Requirement
k-1
k
k
k-1
pause
resume
X
Within time X, betternot consume all data in buffer.
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Storage Requirement
k-1
k
k
k-1
pause
resume
X
Within time X, betternot consume all data in buffer.
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Storage Requirement
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Comparisons
Scheme Storage Server’sBW
Client’sBW
Pyramid 70% KBv 4-5 Bv
Pyramid++ 20% (+p)KBv 2-3 Bv
Carter, Long and Paris “Video on Demand Broadcasting Protocols”
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Pyramid Broadcasting
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Skyscraper BroadcastingObservations:
storage requirement is affected by size of the largest chunk
So, let’s limit the size of the largest chunk!
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Pyramid Skyscraper
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Skyscraper BroadcastingUses series
1 2 2 5 5 12 12 25 25 52 52 … W W W
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Skyscraper Example
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Skyscraper Example
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Comparisons
Scheme Storage Server’sBW
Client’sBW
Pyramid 70% KBv 4-5 Bv
Pyramid++ 20% (+p)KBv 2-3 Bv
Skyscraper
10% KBv 1-2 Bv
Carter, Long and Paris “Video on Demand Broadcasting Protocols”
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Other schemes
Pagoda Broadcasting 1 3 5 15 25 75 125 …
Harmonic BroadcastingEqual segment size, varies bandwidth instead!
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Multicast Solution
BatchingStaggered BroadcastPeriodic Broadcast
Sending rate ≥ playback rateMay need multiple channelsNeed additional client buffer
Need to wait
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Multicast Solution
BatchingStaggered BroadcastPeriodic BroadcastPatching
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Patching
Time
Client Request
mcast
unicast
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Patching
Time
Client Request
Patching Window: W
mcast
mcast
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Grace Patching
if W < Bclient buffer video[W .. end]
30 minutes video1 client arrival per minuteTotal data delivered =
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Scenario 1: B = 15mins30 minutes video1 client arrival per minuteTotal data delivered =
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Scenario 2: B = 5mins
30 minutes video1 client arrival per minuteTotal data delivered =
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Scenario 3: B = 2mins
30 minutes video1 client arrival per minuteTotal data delivered =
NUS.SOC.CS5248-2007Roger Zimmermann (based on slides by Ooi Wei Tsang)
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Summary
Batching (User Centered)Staggered Broadcast (Data
Centered)
Periodic Broadcast (Data Centered)
Patching (True VOD)