Tech Tip: Live Video & Overlays for Win 95/98 & Win NT

The PIXCI® SV4 imaging board can, in conjunction with an appropriate S/VGA card, display live video directly upon the VGA monitor, under Win 95/98 or Win NT. This allows full video rate display, even on slower PC's; and avoids using processor power to repeatedly copy images from system memory to the S/VGA.

With selected S/VGA cards, graphic overlays over live video are also available!

The S/VGA requirements are:

  • S/VGA drivers supporting DirectDraw.
  • Hardware overlay feature.
  • Overlay surface accepting UYVY or YUYV format video.
  • Hardware cursor/sprite/icon support.
  • Hardware chroma key support (optional, for graphic overlays on live video).

In addition, the DirectX enhancement must be installed in Win 95 (DirectX is included with Win NT and need not be installed separately). DirectX is available from Microsoft and most VGA manufacturer's web sites, for example:

The live video feature expects a color video format. If using a monochrome camera, simply select NTSC (or PAL) format; the video format will be color, but the perceived image will remain monochrome.

For users of "C" libraries, putting live video into a window requires only two, simple, function calls. Thereafter, any of the Windows standard Graphics Device Interface functions (e.g. TextOut, LineTo, or their MFC or Visual Basic equivalents) can be used to draw graphics or text in the window, which automatically appears overlayed on the live video!

S/VGA cards performance tested with the PIXCI® SV4 Imaging Board:

ATI with 3D Rage Pro Chip. Provides chroma keying support, and thus graphics over live video. Displays full resolution RS-170. Supports Win NT.

ATI with 3D Rage II Chip. Provides chroma keying support, and thus graphics over live video. Resolution of live video limited to 720x540.

Hercules Dynamite 128/Video. Doesn't support graphics on top of live video. With 4 Megabytes of VGA memory, can display full resolution RS-170. As last checked, doesn't support live video under Win NT.

Note. Any Win 95/98 or Win NT compatible S/VGA card may be used for almost-live video, with the liveliness depending upon the image size and CPU speed.

S/VGA card models and features change often; the S/VGA card manufacturer can advise whether currently sold cards maintain the necessary features.

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