Weird relationship in cvQueryFrame( ) instruction

I noticed that there is a weird behaviour with cvQueryFrame isntruction.

I usually work with IplImage* frame; as the variable to contain the actual frame.

frame = cvQueryFrame(capture);

With this instructions, all goes fine but if you want to save for example next frame with another IplImage* variable because you want to do any other thing. I obtain a compilation error throwing a message about size and other things.

It's looks like there is an invisible relationship between the variable you first use with cvQueryFrame() and you cannot break this relation until you release the capture var.

I think the unique relationship is with the capture variable.

Any option to save different frames with differents IplImage* variabl开发者_运维问答es? Any other ideas ???

I use OpenCV under OS X and installed using MacPorts.