What is overlay ?(nt)

[ole]

what is it ?

[fluggo99]

My guess is you're talking about the video card overlay.

The typical way of displaying something on the computer screen is placing the data in standard video memory, where all other programs place their graphics. Because that can be slow and/or not good-looking, video cards usually support a way to place video in a window on "top" of what's in video memory. That's an overlay. The video card does all the processing for the window, without consulting the processor, since all the video card has to do is modify the output to the display. Makes video a lot faster and a lot higher quality on-screen.

One major thing that an overlay can accomplish is deinterlacing video on the fly. Because each frame of video is made up of alternating lines from two different "fields," a program working with 30fps video would usually display the alternating lines all together in one picture, nothing like what appears on a TV. Overlays can combine or shift the fields in video to make it appear something like it would on TV.

If you're using a Matrox card, you'll see the overlay whenever you play back an MJPEG video that was coded by the Matrox card. You should also see it when capturing video - PC-VCR uses it automatically, but if you're seeing clear lines on the display and skipping frames, your capture program is most likely using "preview" mode instead of the overlay. Preview mode shows you exactly what's being recorded in the file, but like I said above, it doesn't look anything like what you'd see on TV and it takes time away from your processor. Overlays fix that.

Hope that's what you're looking for...