yes it's possible :)
but it will only work with realone as in this example i use transparency to display chapter list over video.
here it is :
first part , main smil file :
<?xml version="1.0"?>
<smil
xmlns="http://www.w3.org/2001/SMIL20/Language"
xmlns:rn="http://features.real.com/2001/SMIL20/Extensions">
<head>
<layout>
<root-layout backgroundColor="black" width="656" height="496"/>
<region id="video_region" z-index="1" />
<region id="region_chap"/>
</layout>
</head>
<body>
<par end="video.end">
<video id="video" src=".\MOVIE.rmvb" region="video_region" regPoint="center" regAlign="center" fill="remove"/>
<video region="region_chap" src="./Chapter.rt" end="video.end" regPoint="center" regAlign="center" rn:backgroundOpacity="30%"/>
<set begin="video.activateEvent" dur="6s" targetElement="region_chap" attributeName="z-index" to="3"/>
</par>
</body>
</smil>
and now the chapter.rt file :
<window type="generic"
width="405"
height="140"
duration = "indefinite"
underline_hyperlinks="false"
link="white"
bgcolor="black">
<font face="arial" size="2">
<b>
<a href="command:seek(00:00:00)" target="_player">- Chapitre 01 </a>
<a href="command:seek(00:02:52)" target="_player">- Chapitre 02 </a>
<a href="command:seek(00:04:52)" target="_player">- Chapitre 03 </a>
<a href="command:seek(00:08:32)" target="_player">- Chapitre 04 </a>
<a href="command:seek(00:10:04)" target="_player">- Chapitre 05 </a>
<a href="command:seek(00:12:50)" target="_player">- Chapitre 06 </a>
<a href="command:seek(00:18:01)" target="_player">- Chapitre 07 </a>
</b>
</window>
Some progs automates this task but as far i know they're all in french ,i'll give some links if you want :)