Overview

As more and more audio-visual information becomes available in digital form, there is an increasing pressure to make use of it. Before one can use any information, however, it has to be located. Unfortunately, widespread availability of interesting material makes this search extremely difficult.

For textual information, currently many text-based search engines, such as Google, Yahoo, Altavista etc. are available on the worldwide web (www), and they are among the most visited sites. This is an indication of real demand for searching information in the public domain. However, identifying information for audio-visual content is not so trivial, and no generally recognised description of these materials exists. In the mean time, there is no efficient way of searching the www for, say, a piece of video concert by Pavarotti, or improving the user friendliness of interconnected computers via the Internet by rich-spoken queries, hand-drawn sketches and image-based queries.

The question of finding content is not restricted to database retrieval applications. For example, TV programme producers may want to search and retrieve famous events stored among the thousands of hours of audio-visual records, in order to collect material for a programme. This will reduce programme time and increase the quality of its content. Another example is the selection of a favourite TV programme from a vast number of available satellite television channels. Currently 6-8 MPEG-2 coded TV programmes can be accommodated in a satellite transponder. Considering that each satellite can have up to 12 transponders, each in horizontal and vertical...