An Active Buffer Management Technique for Providing Interactive Functions in Broadcast Video-on-Demand Systems

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An Active Buffer Management Technique for
Providing Interactive Functions in Broadcast
Video-on-Demand Systems
Zongming Fei, Member, IEEE, Mostafa H. Ammar,
Fellow, IEEE, Ibrahim Kamel, Member, IEEE,
and Sarit Mukherjee, Member, IEEE

IEEE TRANSACTIONS ON MULTIMEDIA, VOL. 7, NO. 5,
OCTOBER 2005
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Outline

• Introduction
• Background and related work
• The idea of Active Buffer Management
• Providing VCR functions in partitioned video
  broadcast
• Simulation results
• Conclusion

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Introduction(1/2)

• Multicast VoD service
• On-demand batching
• Continuous broadcast
• Goal
• Provide interactive functions in broadcast VoD
• system

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Introduction(2/2)

• Problem
• Provide VCR functions
• Discontinuity of playback
• Solution
• Selectively prefetch segments from broadcast
  channels
• Feasible points to adjust clients destination

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Outline

• Introduction
• Background and related work
• The idea of Active Buffer Management
• Providing VCR functions in partitioned video
  broadcast
• Simulation results
• Conclusion

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Partitioned video broadcast

• Partitioned video broadcast
• Divide video into segments
• Uses one channel to send each segment in cycles
• More channel, less startup latency
• Let bandwidthB Mbit/s
• Bandwidth of each channelb Mbit/s
• Channel number K

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Weight function

• Divide video of length L into K segments
• Let channel i periodically broadcast segment i
  (1 i K)
• Each segment size is determined by weight
  function
• Size of segment i is

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Weight function

• Goal minimize startup latency
• Make increase as fast as possible
• Cant be too fast continuity problem !
• Skyscraper broadcasting scheme
• Series generated by 1,2,2,5,5,12,12,25,25
• Upper bound W ser to W if gt W
• Analyze the problems encountered while try to
  provide interactive functions in these schemes
• Design new broadcasting series more suitable

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VCR Actions

• Jump Forward/Backward (JF/JB)
• Fast Forward/Backward (FF/FB)
• Slow Forward/Backward (SF/SB)
• Pause
• Play/Play Backward

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Outline

• Introduction
• Background and related work
• The idea of Active Buffer Management
• Providing VCR functions in partitioned video
  broadcast
• Simulation results
• Conclusion

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Effect of VCR actions
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Conventional Client Buffer Scheme

• Problems
• Lack of flexibility for providing interactive
  functions
• Consecutive VCR actions in the same direction
• may made the play point ultimately move to
  boundary

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Active buffer manager

• Keep the play point in the middle of the buffer
• Lower probability that VCR actions will move the
  play point outside the buffer
• Buffer manager
• Adjust the content of the buffer after VCR action
• Selectively download segments from broadcast
• channel

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Active buffer manager

• the client buffer hold 3 segments
• Case 1 No VCR actions

Download finish
download
K3
K2
K1
K
discard
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Active buffer manager
Download finish

• Case 2 Fast forward

K4
download
K3
K2
K1
discard
K
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Destination Adjustment for VCR Actions

• Client can resume normal play after VCR actions
• There is always destination point ouside client
  buffer
• Adjust the destination point to feasible point

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Outline

• Introduction
• Background and related work
• The idea of Active Buffer Management
• Providing VCR functions in partitioned video
  broadcast
• Simulation results
• Conclusion

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A VCR-Oriented Broadcasting Series

• Segment size 1,2,4,4,8,16,16,32,64,64,
• Let the series increase as fast as possble
• Set parameter to limit the maximum number of the
  series

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VCR function implementation with active buffer
management scheme

• Client required 3 buffers with the same size as
  the maximum segment
• 3 loaders download from 3 channels
• Two components to work with VCR functions
• Player accept user interaction commands
• loader/buffer manager decide which channel
• the client can download segments

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player

• Accept VCR command
• Check whether the content is in the buffer
• Check whether the destination point is feasible
• Assume current play point in segment k
• Pyramid phase
• K, k1,k2 should allocate loader
• Equal segment phase
• K-1, k,k1 should allocate loader

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loader/buffer manager

• Allocate loader/buffers to channel
• Pyramid phase
• Allocate loader to segments K1,k2,k3
• Equal segment phase
• Play point in the early half
• Allocate loader to segments K-1,k,k1
• Play point in the later half
• Allocate loader to segments K,k1,k2
• More loader/buffer is feasible
• Key problem select a appropriate channel to
  download required segments

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Feasible point

• Deal with discontinuity problem
• Definition
• start postion of segment i
• end postion of segment i
• broadcasting point of channel i
• represent video between two y1, y2
• The segment contains destination point d
• is called Target segment
• Consider some rule for feasible point

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Feasible point case 1
If is in the buffer, then is
feasible.
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Feasible point case 2
case 2.1 If and
are in the buffer, then d is feasible.
case 2.2 If are in the buffer, then
is feasible.
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Feasible point case 3
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• Consider the case destination pointd is after the
  channel point Cj
• designate next segment as target segment

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Outline

• Introduction
• Background and related work
• The idea of Active Buffer Management
• Providing VCR functions in partitioned video
  broadcast
• Simulation results
• Conclusion

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Experiment settings

• Video length 120 min
• Divide the video into 30 segments for 30
• channels to broadcasting
• First 8 segments are unequal size,the others are
  in equal size
• First segment is 4.83sec,the largest segment is
  5.15min
• Buffer size is 3 times the largest segment

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User interaction model
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Experiment Definition(1/2)

• Pi probablity of issuing specific VCR actions
• Reduce parametersSet p7p8p90
• Let ,and we have
• Let for 1 i 6
• Define as duration ratio
• Experiment in two ways
• Change probability we let 0.5 and
  vary
• from 0.1 to 0.9.
• Change duration ratio . we change the
  duration ratio from 0.2 to 1.0.

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Experiment Definition(2/2)

• Percentage of VCR actions
• The higher this percentage , the better
  interactive performance of the system
• Percentage of destination shift
• The smaller this percentage, the better
• performance of the system.

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Numerical Results
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Numerical Results
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Numerical Results
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Numerical Results
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Outline

• Introduction
• Background and related work
• The idea of Active Buffer Management
• Providing VCR functions in partitioned video
  broadcast
• Simulation results
• Conclusion

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Conclusion

• A VCR-Friendly broadcast series
• Active buffer management technique
• Provide functionality of interactive services in
  broadcast VoD systems.
• The scheme can implement VCR actions through
  buffering with high interaction levels.