xtraction of information from multimedia contents.</p>
<p>A first successful example of extraction of information from an image is <a href="http://en.wikipedia.org/wiki/QR_Code">QR codes</a>. the idea is similar to barcodes: some information is coded in a picture (a square with white and black points) and could be decoded in real time by QR-code readers. Actually they are used for mobile applications: using a smartphone with a camera is possible to take a picture of a QR-code (from a newspaper, a poster, et