function traitAdded(event:MediaElementEvent):void {
    var element:VideoElement;//should be your video element
    if (event.traitType === withTrait){
        var dynamicStreamTrait:DynamicStreamTrait = element.getTrait(event.traitType) as DynamicStreamTrait;
        //Make sure autoSwich is true
        dynamicStreamTrait.autoSwitch = true;
        dynamicStreamTrait.switchTo(1);
        trace("-----")
        trace(dynamicStreamTrait.getBitrateForIndex(0));
        trace(dynamicStreamTrait.getBitrateForIndex(1));
        trace(dynamicStreamTrait.getBitrateForIndex(2));
        trace("-----")
        dynamicStreamTrait.addEventListener(DynamicStreamEvent.SWITCHING_CHANGE, function(evt:DynamicStreamEvent):void {
            if (evt.switching){
                trace("Dynamic stream switching in progress");
            } else {
                trace("Dynamic stream switched to", dynamicStreamTrait.getBitrateForIndex(dynamicStreamTrait.currentIndex));
            }
        });

    }
}