Interaction with Broadcast Video

1
Interaction with Broadcast Video

• Mounir A. Tantaoui
• Kien A. Hua
• Simon Sheu
• December 2002  Proceedings of the tenth ACM
  international conference on Multimedia

2
Outline

• Introduction
• Related Work
• CCA Broadcasting
• Implementing
• Simulation
• Conclusion

3
Introduction

• Two types of multicasts
• Non-periodic multicast
• Batching
• Patching
• Chaining
• Adaptive piggybacking
• Periodic Broadcast
• Pyramid broadcasting
• Skyscraper Broadcasting (SB)
• Client-Centric Approach (CCA)
• Harmonic Broadcasting (HB)

4
Related Work

• Type of Interactions
• Continuous interactive functions
• Fast-forward
• Fast-backward
• Discontinuous interactive functions
• jump-forward
• jump-backward

5
Related Work (cont)

• Prefetch scheme
• if the data in the prefetch buffer cannot
  accommodate a jump request, the client requesting
  the interaction is moved to an existing stream
• If such a stream does not exist, the server
  issues an emergency stream to provide the
  service.
• Emergency streams are expensive since they serve
  only one client.

6
CCA Broadcasting
The parameter c denotes the maximum number of
fragments a client can download at one time.
7
CCA Broadcasting(cont)
8
CCA Broadcasting(cont)

• Since the first loader finishes downloading the
  first and smallest segment of a group, it can be
  used to download the first segment of the next
  group.
• Segments across a group boundary are always of
  the same size, so the continuity across group
  boundaries is satisfied.
• The CCA technique not only shows good performance
  in term of access latency, but can also be
  extended to support VCR operations .

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A Broadcast Based InteractionTechnique (BIT)

• We assume that we have two versions of the same
  video a normal version and a version compressed
  by a factor f that we call the compression
  factor.
• An example of compression could be selecting each
  f frame of the original video.
• The user watching the compressed version of the
  video at the playback rate will have the
  impression of fast playing the normal video.
• The bandwidth requirement is independent of the
  number of users the system is designed to
  support.

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Channel Design

• If we refer to K as the total number of channels,
  K can be divided into K Kr Ki, where Kr is
  the number of regular channels used to broadcast
  the regular version of the video, and Ki the
  number of interactive channels used to broadcast
  the compressed version of the same video.

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Implementing VCR functions with BIT

• The client storage space is divided into two
  parts
• normal buffer holds the normal video buffer. The
  size of the normal buffer should be large enough
  to store a W-segment
• an interactive buffer caches the compressed
  version of the same video. The size of the
  interactive buffer is set twice the size of the
  normal buffer

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Implementing VCR functions with BIT(cont)

• To play back and provide VCR functions, we
  identify two components that work together
• The Player responsible for rendering the frames
  and accepting interactions
• The Loader responsible for tuning to the
  appropriate channels and downloading the
  segments.

13
BIT Player

• Play Action During the playback of the video,
  the player renders the current play point of the
  normal buffer, and the play point of the
  interactive buffer moves accordingly.
• Jump Forward/Jump Backward actions If the
  destination point is in the normal buffer, the
  player simply moves to the destination point, and
  continues the normal play. Otherwise, the player
  allocates the loaders to start downloading the
  appropriate segments, and continues the normal
  play from the closest point. During these types
  of interactions there is no switch of modes.

14
BIT Player(cont)

• Fast-Forward/Fast-Reverse/Pause actions
• switches to the interactive mode to render the
  frames in the interactive buffer.
• Two scenarios can follows
• (1) If the user resumes the normal play before
  this buffer is exhausted, the player switches to
  the normal mode, and allocates the loaders to
  download the appropriate segments such that the
  normal playback is resumed at a frame closest
  possible to the destination point.

15
BIT Player(cont)

• If the user continues the interactive action
  beyond the frames in the interactive buffer
• Fast-Forward the player forces the user to
  resume the normal play by setting the destination
  point to the newest frame of the interactive
  buffer
• Fast-reverse or pause actions Set to the oldest
  frame
• The player then allocates the loaders, and
  resumes the normal play at the closest point.
• We note that jumping to the closest point will
  show some discontinuity that we refer to as a
  displacement.

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BIT Loader

• If the user continues the interactive action
  beyond the frames in the interactive buffer
• Fast-Forward the player forces the user to
  resume the normal play by setting the destination
  point to the newest frame of the interactive
  buffer
• Fast-reverse or pause actions Set to the oldest
  frame
• The player then allocates the loaders, and
  resumes the normal play at the closest point.
• We note that jumping to the closest point will
  show some discontinuity that we refer to as a
  displacement.

17
Loader Algorithm
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Analysis of the Closest Broadcast Point

• Unequal phase
• All segments are of unequal sizes
• The first two segments are of equal size but not
  the last one
• the last two segments are of the same size but
  not the first one.
• Case 1.1 The segments are all left aligned. If
  segment i was loaded at its broadcast point, the
  user will consume it before the broadcast of the
  next cycle of segment i1, similarly for segment
  i1. Hence the closest broadcast point in this
  case is the broadcast point of segment i2. When
  the loading of segment i2 starts, the two other
  available loaders are reallocated to the next
  round.

19
Analysis of the Closest Broadcast Point(cont)

• Unequal phase
• Case 1.2 Since segments i and i1 are right
  aligned. The closest broadcast point is at
  segment i. After the consumption of segment i,
  the beginning of segment i1 is available and the
  beginning of segment i2 is available after the
  consumption of segment i1.
• Case 1.3 Segments i and i1 are not right
  aligned, but segments i1 and i2 are. Thus the
  closest broadcast point is at segment i1. When
  the user consumes segment i1, segment i2 is
  available.
• Case 1.4 Since all segments are left aligned,
  the closest broadcast point is at segment i.

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Analysis of the Closest Broadcast Point(cont)

• equal phaseDuring the equal phase, the closest
  broadcast point is always at the same segment as
  the destination point. Since we use only one
  regular loader in the equal phase, once the user
  consumes segment i segment i1 is always
  available.

21
Simulation

• compare with the Active Buffer Management (ABM)
  scheme.
• Performance Metrics
• Percentage of Unsuccessful Actions
• Average Percentage of completion
• Effect of the duration ratio
• Effect of the buffer size
• Effect of server bandwidth to the total average
  displacement
• The Effect of Changing the compression factor

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Conclusion

• The existing techniques solved only partially the
  problem of VCR interactivity in a broadcast
  framework.
• This paper proposed a new video interaction
  technique, which offers better interaction
  quality by repeatedly broadcasting the
  interactive (compressed) version of the video.