Transcript Advance in Scalable Video Coding

Advance in Scalable Video
Coding
Proc. IEEE 2005,
Invited paper
Jens-Rainer Ohm, Member, IEEE
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 singlelayer 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 < 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 driftcontrolled 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.

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