Why can’t I take a screenshot of DVD video? Why do I get a pink or black square?

Dec 27th, 2009 by dvdxplayer 2,042 views |Comments Off

Most DVD PCs, even those with software decoders, use video overlay hardware to insert the video directly into the VGA signal. This an efficient way to handle the very high bandwidth of full-motion video. Some decoder cards, such as the Creative Labs Encore Dxr series and the Sigma Designs Hollywood series, use a pass-through cable that overlays the video into the analog VGA signal after it comes out of the video display card. Video overlay uses a technique called colorkey to selectively replace a specified pixel color (often magenta or near-black) with video content. Anywhere a colorkey pixel appears in the computer graphics video, it’s replaced by video from the DVD decoder. This process occurs “downstream” from the computer’s video memory, so if you try to take a screenshot (which grabs pixels from video RAM), all you get is a solid square of the colorkey color.

Hardware acceleration must be turned off before screen capture will work. This makes some decoders write to standard video memory. Utilities such as Creative Softworx, HyperSnap, and SD Capture can then grab still pictures. Some player applications such as PowerDVD and the Windows Me player can take screenshots if hardware acceleration is turned off.

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