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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Chapter 1<br />
Digital Video Coding at<br />
Very-Low BitRate<br />
\Visual communication is commonly regarded as the next generation<br />
communication tool beyond the conventional voice communication (...<br />
<strong>and</strong>) to achieve more e cient visual communication <strong>and</strong> fully utilize<br />
limited channel b<strong>and</strong>width <strong>and</strong> storage space, <strong>video</strong> compression (or <strong>coding</strong>)<br />
that reduces data amount is necessary." (C.T. Chen)<br />
Aware of this relevant challenge, research has been focusing on <strong>video</strong><br />
compression <strong>for</strong> already more than twenty years. People from both the<br />
industry <strong>and</strong> research teams have collaborated in groups like the International<br />
Telecommunications Union (ITU) or the Moving Picture Experts<br />
Group (MPEG) to design several international st<strong>and</strong>ards <strong>for</strong> transmission<br />
<strong>and</strong> storage of digital <strong>video</strong>.<br />
The present chapter aims at introducing the general framework of the<br />
doctoral work. It rst <strong>very</strong> brie y describes the structure of a digital<br />
<strong>video</strong> signal, <strong>and</strong> exp<strong>and</strong>s on the generic principles of <strong>video</strong> compression<br />
according to type of correlation which is exploited: spatial or spatiotemporal.<br />
It then highlights the speci city ofVery-Low Bitrate Coding<br />
(VLBR) with regards to high-<strong>bitrate</strong> <strong>coding</strong>: VLBR is unable to transmit<br />
a visually perfect copy of the source images as the limited channel<br />
capacity prevents the coder from sending all the in<strong>for</strong>mation needed.<br />
Secondly, it reviews three <strong>video</strong> coders-decoders (codecs): the H.263<br />
st<strong>and</strong>ard from the ITU, the scheme to be st<strong>and</strong>ardized in November<br />
1998 under the acronym MPEG-4, <strong>and</strong> some trials implemented at UCL<br />
within a scheme named COMIS.
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