Overlays

Direct Draw is a fast drawing method that moves video directly from the Osprey capture card to the display adapter. If Use Direct Draw is selected, the driver use Direct Draw for Overlay drawing. If for some reason it cannot use Direct Draw, it will automatically fall back to the default drawing mode (known as "DibDraw").

Direct Draw works with the vast majority of display adapters and software driver. We recommend running with Direct Draw enabled unless you are having a problem viewing overlay video, or want to use the "doubled lines" option discussed below. For more details on Direct Draw, refer to Appendix E: Direct Draw in the User's Guide.

DibDraw is the default drawing method. Video is moved first into system memory, then copied to the display adapter. It is useful in the following cases:

  1. For systems where Direct Draw does not work correctly.

  2. If you want to enable "line doubling". When DibDraw is selected, two radio buttons are enabled that let you choose between interlaced and line-doubled video.

Normally, video larger than ½-height (240 lines NTSC, 288 lines PAL) is interlaced. NTSC and PAL video both consist of alternating odd and even fields of data. Odd numbered lines come from the odd fields, even numbered lines come from the even fields.

Interlaced video offers maximum resolution but suffers from a "comb" effect: When there is rapid motion in the video, it appears blurred. It is recommended for still or slow-motion video, but may not look good with high-motion content.

Line-doubled video uses video data from only one field. Each video line is copied to two lines of your display. Line-doubling reduces the still-picture resolution by half; however, it eliminates the "comb" effect of interlaced video and is therefore useful for viewing rapid-motion video.

  1. If you want to stretch the video on your screen beyond full size (640x480 NTSC, 768x576 PAL). You would need a special application to do this. DibDraw video can be stretched but Direct Draw video cannot be.