VfW Video modes

There are two modes of operation called Preview and Overlay. Preview mode shows video using software BitBlt function on primary display surface. This is very CPU consuming. Overlay mode is using overlay surface in graphic card's memory and video is hardware stretched to primary sourface. Not all graphic cards suport this mode, but all new cards does.

Note: Some video capture drivers (for example cards with BT848/878 based chipset) don't support capture in overlay mode with more then half of maximum video lines (so 288 for PAL/SECAM and 240 for NTSC). In this case you must use preview mode.