There may be someway to call up the decoder in the config file, but I don't know how. Maybe you can use the other filters as examples, and add the nVidia stuff. If I get some time, I'll take a stab at it. But if you do it, it will get done quicker 
<capturecard commercialname="Hauppauge Nova-T Stick DVB-T Tuner Device" capturename="WinTV Nova-T Stick DVB-T Capture (Dev1 Path0)" devid="vid_2040&pid_7060">
<capabilities tv="true" radio="false" mpeg2="true" mce="false" sw="false" bda="true"/>
<tv>
<interface cat="capture" video="2" audio="3" mpeg2="1" sectionsandtables="5"/>
<filters>
<filter cat="networkprovider" name="Microsoft DVBT Network Provider" checkdevice="false"/>
<filter cat="tunerdevice" name="WinTV Nova-T Stick DVB-T Tuner (Dev1 Path0) " checkdevice="true"/>
<filter cat="capture" name="WinTV Nova-T Stick DVB-T Capture (Dev1 Path0)" checkdevice="true"/>
</filters>
<connections>
<connection sourcefilter="networkprovider" sourcepin="0" sinkfilter="tunerdevice" sinkpin="0"/>
<connection sourcefilter="tunerdevice" sourcepin="0" sinkfilter="capture" sinkpin="0"/>
</connections>
</tv>
</capturecard>