VCR-oriented Video Broadcasting for Near Video-On-Demand Services

1
VCR-oriented Video Broadcasting for Near
Video-On-Demand Services

• Jin B. Kwon and Heon Y. Yeon

Appears in IEEE Transactions on Consumer
Electronics, vol. 49, No. 4, Nov. 2003, pp. 1106
- 1113
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Outline

• Introduction
• Conditions for continuous VCR
• VCR-oriented periodic broadcasting (VPB)
• Reception schedule for continuous VCR actions
• Discontinuous VCR actions handling
• Simulation results
• Conclusion

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Introduction

• True VoD systems use dedicated channel for each
  user
• Respond to users quickly
• Server bandwidth runs out quickly
• Expensive and not scalable

4
Introduction

• Near VoD systems let multiple users share video
  streams
• Scheduled multicast (Close-loop)
• Transmission schedule adapt to users arrival
  pattern
• Periodic broadcast (Open-loop)
• Transmission schedule is fixed regardless of
  users arrival pattern
• This paper proposes a novel architecture of a
  periodic broadcast system that guarantee to
  support VCR actions

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Conditions for continuous VCR

• VCR functions can be classified into continuous
  and discontinuous functions
• Continuous function
• Play Forward/Play Backward
• Fast Forward/Fast Backward
• Slow Forward/Slow Backward
• Pause
• Discontinuous
• Jump Forward/Jump Backward

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Conditions for continuous VCR
d
S0 S1 ...... SK-2 SK-1 S0
SK-1 S0 S1 SK-2 SK-1
SK-2 SK-1 S0 S1 SK-2

S2 S3 S4 S5 S2
S1 S2 S3 S4 S1






Channel 0
b
Channel 1
Channel 2
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Conditions for continuous VCR

• Define
• ?(k0, k) be the distance (in second) from play
  point k0 to a future frame k at a normal play
  rate ?
• c(k) be the time remaining until frame k is
  consumed
• Then,
• Consumption time of frame k time taken to
  consume all frames between k0 and k

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Conditions for continuous VCR

• If B is a set of frames currently in buffer,
  continuous VCR functions can be provided if
• where b(k) is the next broadcast time of k
• Minimal client buffer space required for a client
  to provide continuous VCR functions consistently
  is 2nm
• must be in buffer before c(k)
• Worst case

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VCR-oriented periodic broadcasting (VPB)

• VPB uses K/n channels each with bandwidth nb
• Si is broadcast over channel

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VCR-oriented periodic broadcasting (VPB)

• In VPB, the next broadcast time, b(k) d
• So if , continuous
  VCR functions can be provided
• Frames with distance gt nd do not have to be
  buffered as they can be obtained by next
  broadcast before consumption
• If n 3 and the current play point k0 is in Si,
  target segments containing required future frames
  are Si, Si1, Si2, Si3

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Reception Schedule

• When S1 is being broadcast, S4, S7, , SK/3-2 are
  also being broadcast
• The following show the required frames to be
  stored when the channels are transmitting the
  target segments

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Reception Schedule

• Since only the frames within the distance nd are
  considered, the total buffer requirement for
  forward and backward buffer is 2nm
• Receive and store the currently broadcasting
  frame, kt, into buffer if
• Continuous VCR actions are guaranteed

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Reception Schedule
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Discontinuous VCR Actions Handling

• Discontinuous actions render the buffered content
  useless
• Jump to the requested destination immediately
  maybe impossible due to buffer restrictions and
  the service latency in periodic broadcast
• VPB provides VCR action guarantee as when the
  service start, except for backward action

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Discontinuous VCR Actions Handling

• For (a), as all essential frames are in buffer,
  the action is allowed
• For (b), the action is allowed if the current
  broadcast point satisfy
• For (c), destination shift introduced
• Maximum destination shift is nd/2 while the
  average is nd/4

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Simulation Results

• Parameters
• Mean duration of cont. action 10s
• Mean jumping distance 60s
• Fast Forward/Backward rate, n 3
• Segment length 60s
• No. of Segments 32
• Normal playback bitrate, ? 30fps

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Simulation Results
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Simulation Results

• Proportion of shifted destinations increases with
  mean jump distance
• The average shift distance increases with the
  mean jump distance
• Long jump actions are probably not serviced by
  the buffered data

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Conclusion

• This paper
• analyzes the necessary conditions to provide VCR
  functions
• proposes a VCR-oriented broadcasting scheme (VPB)
  that guarantee to support all continuous actions
  consistently and discontinuous actions with
  destination shift
• VPB utilizes minimal client buffer requirement
• VPB clients bandwidth increases with n

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Final Thoughts

• VPB is a scheme that support VCR actions with the
  trade off of increased client bandwidth
• It requires frame level synchronization, which
  may not be possible
• Comparisons with other schemes should be provided