Quote:
Originally posted by agent
Overlay wasn't invented to keep you from capturing streams, it was invented to display video extremly fast.
The way it works is the program draws a box of a specific color (in wmp's case it's 16,0,16 (r,g,b repectivly)). then the program sends a command to DirectX (i think it is) that turns on overlay and give the dimentions and position of the (almost) black box. DirectX tells the video card to replace the color 16,0,16 with the video. This is completely independant of the GDI. The video is moved directly to the video card's memory (and then to the screen) with windows none the worse for the ware. Windows doesn't know that anything other than an (almost) black square is being drawn, hence no window updates, hence no CPU usage, hence fast video, and also the ability for tv tuner cards to continue to update the screen even when the computer has been frozen (this works in windows 98 when the mouse is frozen)
all wmp needs to do is pass the video info to what windows thinks is an off-screen buffer, but is actually video memory
most newer cards support overlays, but some older ones don't
it also passes position information (of the window that contains the video), however no window clipping info is passed.