I am creating a SMIL file to create a pseudo live broadcast with a lot of mp3 files. I need that while a file is fading in, the next file is fading out. For instance:

<playlist name="1" playOnStream="Stream1" repeat="false" scheduled="2015-05-04 04:00:00">
<video src="mp3:A.mp3" start="0" length="-1"/>
<video src="mp3:B.mp3" start="0" length="-1"/>

In that case, in the the last seconds of A.mp3 it should be faded out and, at the same time, the B.mp3 file should be faded in. I mean, the two files should be played at the same time for a few seconds.
How can I do this using Wowza Server-Side API?