Multi-threaded video decoding problem

I have simple AIR 3.8 application with 2 VideoPlayers:

<s:WindowedApplication xmlns:fx="http://ns.adobe.com/mxml/2009"
 xmlns:s="library://ns.adobe.com/flex/spark"
 xmlns:mx="library://ns.adobe.com/flex/mx"
 applicationComplete="init()"
 showStatusBar="false"
 >
 <fx:Script source="MultiVideoPlayer.as" />
 <s:VGroup width="100%" height="100%" > 
 <s:HGroup width="100%" height="100%" id="row1" >
 <s:VideoPlayer width="100%" height="100%" source="assets/2.mp4"/>
 <s:VideoPlayer width="100%" height="100%" source="assets/3.mp4"/>
 </s:HGroup>
 </s:VGroup>
</s:WindowedApplication>

Both videos are H.264 Full HD samples.

I launch application and multi-threaded decoding works fine - all cores are involved and CPU usage is around 70%.

When I replace source of VideoPlayers with exactly same files programmatically - videos are reloading, but they doesn't play smoothly and multi-threaded decoding isn't working anymore - CPU usage drops to 10%.

Is there any way  to force use of multi-threaded video decoding when videos are loaded dynamically?