Advance in Scalable Video Coding

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Advance in Scalable Video Coding

• Proc. IEEE 2005,
• Invited paper
• Jens-Rainer Ohm, Member, IEEE

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Outline

• Introduction
• Scalability in Existing Standard
• Principles of Scalable Predictive Coding
• Drift control
• Interframe Wavelet Coding
• Conclusion

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Introduction

• Scalable video coding is attractive due to the
  capability of reconstructing lower resolution or
  lower quality signals from partial bit streams.
• A simple and flexible solution for transmission
  over heterogeneous network.
• Allow simple adaptation for a variety of storage
  devices and terminals.

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Scalability in Existing Standard

• MPEG-2
• First general-purpose video compression standard
  which also include tools providing scalability.
• Layered coding, support spatial, temporal, SNR
  scalability.
• Number of layers is restricted to maximum of 3.

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Scalability in Existing Standard(2)

• MPEG-4
• More flexible scalability tools, including
  spatial and temporal scalability within a more
  generic framework.
• SNR scalability with fine granularity and
  scalability at level of video objects.
• AVC can in principle be run in different temporal
  scalability modes.

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Principles of Scalable Predictive Coding

• Prediction should not use any decoded information
  from higher layers, otherwise drift effect would
  occur.
• However the rate-distortion performance toward
  higher rates will be worse than single-layer
  coder.

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Drift control

• It is possible to track the drift within the
  local loop of the encoder that would occur in a
  decoder only receiving the base-layer
  information.
• Drift compensation
• Drift clipping
• Drift leaking

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Drift compensation

• It assume that the decoder side is not aware of
  the drift compensation made.
• Usual MC decoder loop could be used without any
  modifications.
• The encoder have to find the balance between the
  penalties for the base and enhancement decoding.

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Drift clipping

• The drift is dynamically limited if a maximum
  value Dmax is reached.
• A good choice for Dmax is approximately by the
  base-layer quantizer step size.

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Drift leaking

• The accumulation of drift is limited by
  multiplying D a D (a lt 1)
• The best selection of drift coefficient is
  dependent on the operational target and sequence
  characteristic.

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Interframe Wavelet Coding

• To overcome the limitation which are caused by
  drift problem, it would be desirable to discard
  the temporal recursion.
• Motion-Compensated Temporal Filtering

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Spatiotemporal wavelet decomposition
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Spatiotemporal wavelet decomposition (2)
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Lift structure
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Operation of Motion Compensation
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Conclusion

• The fully open loop property of MCTF provides
  high flexibility in bit stream scalability.
• Combination of MCTF with the new drift-controlled
  prediction strategies is also a promising path.
• Decoder could integrate additional signal
  synthesis element whenever the received
  information is incomplete.

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Conclusion (2)

• When low delay is required, the update step must
  be omitted, or the number of temporal wavelet
  decomposition levels must be low.
• Seamless transition between intraframe and
  interframe coding methods.