Matlab video input using a hardware encoded h.264 video stream?

I have been using a PCI video capture card with analog PAL/NTSC cameras for a few years now. Up to this point I have been able to use Direct Show drivers to see the card and read video frames into Matlab 2015a, writing them to file with a video writer.

Recently, I updated my PCI card to include onboard hardware h.264 video compression. Unfortunately, while I can see both the unencoded and the hardware encoded streams as video sources in Matlab, if I try to preview (or do anything with) the encoded stream, I get junk (green screen with multi color pixelation at the top). I have a sample application that shipped with the card demonstrating that the encoded video stream is good, but Matlab just can't make sense of it.

Is there something special that I should be doing to be able to see hardware encoded h.264 streams? Keep in mind that this is not a file writer problem as even the following will give me a bad screen:

videoinput('winvideo',2)

preview(ans)