I think it is because this is a webcam and always wants to run at the fastest rate. In IMAQdx we do iterate over the listed framerates and so I expect that this particular camera was only listing one per each resolution/format.
I just came across the same problems as yours. So I tried to use LabVIEW to control a Philips webcam NPC900NC. I could configure it in MAX and vi, but only for some "basic" modes. I cannot change the frame rate of it above 30 FPS, which I can achieve in the camera's driver and in VC code. The VC code did this by calling functions in DirectShow. So I wondered if there is any way I can call the hidden functions of DirectShow in LabVIEW?
You mentioned that you solved this by creating an AcitveX control. Could you give more details on it? Thank you very much.
(Windows XP 32-bit, LabVIEW 2009, IMAQdx)
Thank you for your reply. It is really helpful. I will look up calling AM_MEDIA_TYPE function in LabVIEW then.
Thanks again for your help.
AM_MEDIA_TYPE is a structure type:
The member pbFormat contains a pointer to a VIDEOINFOHEADER structure:
Its AvgTimePerFrame member contains the frame rate.
The AM_MEDIA_TYPE is used in SetMediaType and when filter pins are connected.