The buffers used with video capture reside in the memory heap. The number of buffers used in a capture operation can vary and depend on the value of the wNumVideoRequested member of the CAPTUREPARMS structure and available system memory.
You can retrieve the current value of requested video buffers by using the WM_CAP_GET_SEQUENCE_SETUP message (or the capCaptureGetSetup macro). The current requested number of video buffers is stored in the wNumVideoRequested member of the CAPTUREPARMS structure. You can request the placement and number of buffers by updating this member, and then sending the updated CAPTUREPARMS structure to the capture window by using the WM_CAP_SET_SEQUENCE_SETUP message (or the capCaptureSetSetup macro).