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Video On Demand - PowerPoint PPT Presentation
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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
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Video on Demand
- One video server
- Many video data
- Many clients
- Client want to watch at any time
NUS.SOC.CS5248-2010
Roger Zimmermann (based in part on slides by Ooi Wei Tsang)
Assumptions
- Constant bitrate stream
- Perfect network transport
NUS.SOC.CS5248-2010
Roger Zimmermann (based in part on slides by Ooi Wei Tsang)
Unicast Solution
- One channel per client
- No start-up latency
- No client buffer
- Low client bandwidth
- Large server bandwidth
- Not scalable
NUS.SOC.CS5248-2010
Roger Zimmermann (based in part on slides by Ooi Wei Tsang)
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.CS5248-2010
Roger Zimmermann (based in part on slides by Ooi Wei Tsang)
Multicast Solution
- User-centered approach
- Scheduling data based on user requests
- Data-centered approach
- Don’t care about user
- Just broadcast popular video
NUS.SOC.CS5248-2010
Roger Zimmermann (based in part on slides by Ooi Wei Tsang)
Multicast Solution
- Batching
- Staggered Broadcast
NUS.SOC.CS5248-2010
Roger Zimmermann (based in part on slides by Ooi Wei Tsang)
Staggered Broadcast
Video
C0
C1
C2
:
NUS.SOC.CS5248-2010
Roger Zimmermann (based in part on slides by Ooi Wei Tsang)
Staggered Broadcast
- 2 hour video
- 5 minutes waiting time
- Number of channels =
2 x 60 / 5 = 24
- Required bandwidth =
1.5Mbps x 24 = 36Mbps
NUS.SOC.CS5248-2010
Roger Zimmermann (based in part on slides by Ooi Wei Tsang)
Multicast Solution
- Batching
- Staggered Broadcast
- clients have to wait
- No client buffer
- Low client bandwidth
- Huge server bandwidth
NUS.SOC.CS5248-2010
Roger Zimmermann (based in part on slides by Ooi Wei Tsang)
Multicast Solution
- Batching
- Staggered Broadcast
- Periodic Broadcast
NUS.SOC.CS5248-2010
Roger Zimmermann (based in part on slides by Ooi Wei Tsang)
Periodic Broadcast
Video
C0
C1
C2
:
NUS.SOC.CS5248-2010
Roger Zimmermann (based in part on slides by Ooi Wei Tsang)
Pyramid Broadcast
Video
C0
C1
C2
:
NUS.SOC.CS5248-2010
Roger Zimmermann (based in part on slides by Ooi Wei Tsang)
Pyramid Broadcast
Video
C0
C1
C2
:
NUS.SOC.CS5248-2010
Roger Zimmermann (based in part on slides by Ooi Wei Tsang)
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.CS5248-2010
Roger Zimmermann (based in part on slides by Ooi Wei Tsang)
Channel Bandwidth
playback time = Ti
i
i+1
i+1
D’oh!
Just
miss
it!
download time = Ti+1Bv/Bi
Download time for segment i+1 needs
to be smaller than Ti for it to arrive in time.
NUS.SOC.CS5248-2010
Roger Zimmermann (based in part on slides by Ooi Wei Tsang)
Start-up Latency
- Worst case waiting time =
NUS.SOC.CS5248-2010
Roger Zimmermann (based in part on slides by Ooi Wei Tsang)
Pyramid Broadcast
- Large client bandwidth (KBv)
- Huge client buffer (70–80% Tv)
NUS.SOC.CS5248-2010
Roger Zimmermann (based in part on slides by Ooi Wei Tsang)
Permutation-based Pyramid Broadcast
C0
C1
C2
NUS.SOC.CS5248-2010
Roger Zimmermann (based in part on slides by Ooi Wei Tsang)
Channel Bandwidth
playback time = Ti
i
i+1
i+1
i+1
i+1
D’oh!
Just
miss
it!
download time = Ti+1Bv/Bi
X
X needs to be smaller than Ti for segment
i+1 to arrive in time.
NUS.SOC.CS5248-2010
Roger Zimmermann (based in part on slides by Ooi Wei Tsang)
Storage Requirement
- One channel at a time
- Can pause and wait
NUS.SOC.CS5248-2010
Roger Zimmermann (based in part on slides by Ooi Wei Tsang)
Storage Requirement
pause
k-1
k-1
k
resume
k
Within time X, better
not consume all data
in buffer.
X
NUS.SOC.CS5248-2010
Roger Zimmermann (based in part on slides by Ooi Wei Tsang)
Storage Requirement
pause
k-1
k-1
k
k
resume
Within time X, better
not consume all data
in buffer.
X
NUS.SOC.CS5248-2010
Roger Zimmermann (based in part on slides by Ooi Wei Tsang)
Comparisons
Carter, Long and Paris
“Video on Demand Broadcasting Protocols”
NUS.SOC.CS5248-2010
Roger Zimmermann (based in part on slides by Ooi Wei Tsang)
Skyscraper Broadcasting
- Observations:
- storage requirement is affected by size of the largest chunk
So, let’s limit the size of the largest chunk!
NUS.SOC.CS5248-2010
Roger Zimmermann (based in part on slides by Ooi Wei Tsang)
Skyscraper Broadcasting
- Uses series
1 2 2 5 5 12 12 25 25 52 52 … W W W
NUS.SOC.CS5248-2010
Roger Zimmermann (based in part on slides by Ooi Wei Tsang)
Comparisons
Carter, Long and Paris
“Video on Demand Broadcasting Protocols”
NUS.SOC.CS5248-2010
Roger Zimmermann (based in part on slides by Ooi Wei Tsang)
Other schemes
- Pagoda Broadcasting1 3 5 15 25 75 125 …
- Harmonic Broadcasting
Equal segment size, varies bandwidth instead!
NUS.SOC.CS5248-2010
Roger Zimmermann (based in part on slides by Ooi Wei Tsang)
Multicast Solution
- Batching
- Staggered Broadcast
- Periodic Broadcast
- Sending rate ≥ playback rate
- May need multiple channels
- Need additional client buffer
- Need to wait
NUS.SOC.CS5248-2010
Roger Zimmermann (based in part on slides by Ooi Wei Tsang)
Multicast Solution
- Batching
- Staggered Broadcast
- Periodic Broadcast
- Patching
NUS.SOC.CS5248-2010
Roger Zimmermann (based in part on slides by Ooi Wei Tsang)
Patching
Time
mcast
unicast
Client Request
NUS.SOC.CS5248-2010
Roger Zimmermann (based in part on slides by Ooi Wei Tsang)
Patching
Patching Window: W
Time
mcast
mcast
Client Request
NUS.SOC.CS5248-2010
Roger Zimmermann (based in part on slides by Ooi Wei Tsang)
Grace Patching
ifW < B
client buffer video[W .. end]
- 30 minutes video
- 1 client arrival per minute
- Total data delivered =
NUS.SOC.CS5248-2010
Roger Zimmermann (based in part on slides by Ooi Wei Tsang)
Scenario 1: B = 15mins
- 30 minutes video
- 1 client arrival per minute
- Total data delivered =
NUS.SOC.CS5248-2010
Roger Zimmermann (based in part on slides by Ooi Wei Tsang)
Scenario 2: B = 5mins
- 30 minutes video
- 1 client arrival per minute
- Total data delivered =
NUS.SOC.CS5248-2010
Roger Zimmermann (based in part on slides by Ooi Wei Tsang)
Scenario 3: B = 2mins
- 30 minutes video
- 1 client arrival per minute
- Total data delivered =
NUS.SOC.CS5248-2010
Roger Zimmermann (based in part on slides by Ooi Wei Tsang)
Summary
- Batching (User Centered)
- Staggered Broadcast (Data Centered)
- Periodic Broadcast (Data Centered)
- Patching (True VOD)
NUS.SOC.CS5248-2010
Roger Zimmermann (based in part on slides by Ooi Wei Tsang)
