<p>I want to generate a thumbnail preview of videos in Java. I'm mostly JMF and video manipulation alienated. </p>

<ul>
<li>Is there an easy way to do it?</li>
<li>What about codecs? Will I have to deal with it?</li>
<li>Any video type is suported? (including Quicktime)</li>
</ul>

Are you sure that JMF is right for you?  Unfortunately, it is not in particularly good shape.  Unless you are already committed to JMF, you very well may want to investigate alternatives. Wikipedia has a decent overview at
en.wikipedia.org/wiki/Java_Media_Framework
Many JMF developers have complained that it
supports few codecs and formats in modern use
. Its all-Java version, for example, cannot play MPEG-2, MPEG-4, Windows Media, RealMedia, most QuickTime movies, Flash content newer than Flash 2, and
needs a plug-in to play the ubiquitous MP3 format
.  While the performance packs offer the ability to use the native platform's media library, they're only offered for Linux, Solaris and Windows. Furthermore,
Windows-based JMF developers can unwittingly think JMF provides support for more formats than it does
, and be surprised when their application is unable to play those formats on other platforms.
Another knock against JMF is Sun's seeming abandonment of it. The
API has not been touched since 1999
, and the last news item on JMF's home page was posted in November 2004.
While JMF is built for extensibility,
there are few such third-party extensions
.
Furthermore,
editing functionality in JMF is effectively non-existent
, which makes a wide range of potential applications impractical.