GetAvailableVideoFrameCount() always returns 0

I am developing a machine vision application on OS X using an Intensity Extreme for capturing HDMI frames.
It turns out that IDeckLinkInput::GetAvailableVideoFrameCount() always returns 0. I hoped to use this method to skip frames when processing can't keep up, but now i have to find another way to achieve that. Is this a known issue in the driver or am i misunderstanding the purpose of this function? Will it only work with some specific capture devices?
It turns out that IDeckLinkInput::GetAvailableVideoFrameCount() always returns 0. I hoped to use this method to skip frames when processing can't keep up, but now i have to find another way to achieve that. Is this a known issue in the driver or am i misunderstanding the purpose of this function? Will it only work with some specific capture devices?