motion estimation and compensation for very low bitrate video coding
motion estimation and compensation for very low bitrate video coding
motion estimation and compensation for very low bitrate video coding
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Conclusion<br />
With the emergence on the market of <strong>low</strong>-cost cards al<strong>low</strong>ing customers<br />
to decode the ISO MPEG-1 <strong>and</strong> MPEG-2 st<strong>and</strong>ards, digital <strong>video</strong> <strong>coding</strong><br />
is becoming a <strong>very</strong> common functionality ofmultimedia personal<br />
computers. For several years, <strong>video</strong> <strong>coding</strong> has moved towards <strong>very</strong><strong>low</strong><br />
<strong>bitrate</strong>s (under 64kbits=s). A major result of this trend is the ITU<br />
H.263 st<strong>and</strong>ard which also has the advantage that the software version<br />
of its decoder per<strong>for</strong>ms in real-time on a PC. The future ISO MPEG-4<br />
st<strong>and</strong>ard goes one step further as it o ers the possibility to the user to<br />
somehowinteract with the contents of the pictured scene. Because of the<br />
convergence of the target <strong>bitrate</strong>s with the ever-increasing capabilities of<br />
existing networks, some people already claim that these two st<strong>and</strong>ards<br />
are putting an end to research in \pure" <strong>video</strong> <strong>coding</strong>.<br />
Among the tools used to achieve compression of the <strong>video</strong> signal, <strong>motion</strong><br />
<strong>estimation</strong> is probably the one o ering the greatest compression ratio. A<br />
lot of research has been devoted to it during the last two decades. It not<br />
only resulted in great outcomes in <strong>video</strong> <strong>coding</strong> but also in other elds<br />
where <strong>motion</strong> analysis plays a key role, like semantic interpretation or<br />
target tracking. The exploitation of <strong>motion</strong> in a <strong>video</strong> <strong>coding</strong> scheme<br />
typically involves three steps: <strong>estimation</strong>, transmission <strong>and</strong> <strong>compensation</strong>.<br />
The <strong>video</strong> <strong>coding</strong> context <strong>and</strong> the state of the art in related <strong>motion</strong><br />
<strong>estimation</strong> techniques have respectively been presented in Chapter One<br />
<strong>and</strong> Chapter Two. Some emphasis was put on the <strong>very</strong>-<strong>low</strong> <strong>bitrate</strong><br />
environment <strong>and</strong> on the most used <strong>motion</strong> <strong>estimation</strong> techniques (BMA<br />
<strong>and</strong> warping techniques). In this sense, the present thesis contributes to<br />
the investigation of the possibility to enhance the various steps of the<br />
<strong>motion</strong> chain by somehow taking into account the spatial contents of the<br />
image(s).<br />
Chapter Three modi es the <strong>estimation</strong> per<strong>for</strong>med by a classical BMA