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Advanced motion information coding and deblocking techniques for scalable video compression

vrijdag, 15 december, 2006 - 16:30
Campus: Brussels Humanities, Sciences & Engineering campus
D
2.01
Joeri Barbarien
doctoraatsverdediging

Today, the increasing heterogeneity of play-back devices and networks poses substantial
problems for multimedia content distribution applications, since different end-users
require a separate version of the content, specifically tailored to their terminal and
connection characteristics. Scalable video coding schemes, which produce a single
compressed bit-stream from which content representations with a different quality,
resolution, and frame-rate can be extracted without the need for re-encoding, are
considered to be the best solution to tackle this problem.

Wavelet-based video coding technology can provide full support for scalability while
delivering state-of-the-art compression performance. In this dissertation, several
problems limiting the compression efficiency and functionality of wavelet-based scalable
video coding schemes are tackled.

A major part of our work is related to motion information coding in wavelet-based
scalable video codecs. The majority of these video codecs employ motion compensated
prediction or motion compensated temporal filtering to eliminate the temporal
redundancies from the video material. This means essentially that a motion model is used
to estimate the object and camera motion between subsequent frames and that the
estimated motion is used as a basis for the efficient prediction of frames based on their
neighboring frames. To allow proper reconstruction of the video sequence at the decoder
side, the parameters of the motion model describing this estimated motion need to be
encoded using a motion information codec and sent to the decoder.

The first part of our work is focused on wavelet-based video coding approaches
employing so-called in-band motion compensated prediction or in-band motion
compensated temporal filtering (MCTF). These approaches produce significantly more
motion information than their spatial- domain equivalents, which affects the compression
performance, particularly when targeting low bit-rates. To resolve this problem, efficient
motion information coding schemes for in-band motion estimation are proposed in this
dissertation.

As a second contribution, this thesis presents a novel quality scalable motion information
coding scheme for video codecs employing spatial-domain MCTF. Quality scalable
motion information codecs produce a single scalable bit-stream which can be truncated at
specified locations to produce a lower-quality, lower bit-rate representation of the motion
information. Using quality scalable motion information coding leads to a systematically
better compression performance when targeting low bit-rates and can indirectly lead to
improved compression performance at higher bit-rates as well, since the complexity and
corresponding accuracy of the motion field are no longer limited by the lowest bit-rate
that needs to be supported. The quality scalable motion information coding technique
proposed in our work outperforms state-of-the-art wavelet-based solutions. To be able to
practically benefit from the proposed scheme, two rate allocation strategies for waveletbased
video codecs, capable of optimally distributing the available bit-budget between
texture and motion information are also proposed.

A final contribution of this work is a novel adaptive deblocking filter which resolves the
problems caused by block-boundary discontinuities in wavelet-based video codecs
employing a block-based motion model. Applying the proposed deblocking filter yields
the same visual quality as using classical overlapped-block motion compensation but
requires significantly less processing time when targeting a PC platform implementation.