An Interlacing Primer

A big part of the PureVideo feature set are its de-interlacing capabilities, but before we explain what de-interlacing is we have to explain what interlacing is and why you would want to de-it. Let's say we wanted to display an animation and here we have one frame of that animation:

If the world were perfect we would just broadcast as many frames of our animation as we had, at a constant frame rate, and we would have accomplished what we set out to do. Unfortunately the world isn't perfect and when we first wanted to broadcast this animation there were significant bandwidth limitations both on the transmitting and receiving side, preventing us from sending one complete animation frame at a time. One solution to this problem would be to divide up each frame into separate parts and display those parts in sequence. If the sequence is fast enough, the human eye would be hard pressed to notice the difference. So let's do it, we take our original frame and produce two separate fields, each with half of the resolution of the original frame:

Field 1

Field 2

And we're done, what we've just briefly described is how interlaced television came about. Interlaced NTSC TV (the North American standard) works by displaying 60 interlaced fields per second relying on the human eye to do a bit of blending work on its own, making two half resolution fields appear to be a single full resolution frame. More recently there has been a push away from interlaced TVs to non-interlaced displays, which is a wonderful step towards improved picture quality but not without creating a whole new set of problems. Keep this basic introduction to interlaced TV in mind as we look at converting non-interlaced (progressive) content to an interlaced format and back again.
Index Frame Rate Conversion and You
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  • Cybercat - Monday, December 20, 2004 - link

    Oh, nevermind, that's for PCI Express 6800s, which are apparently the only cards that use the NV41 core. AGP 6800s use the NV40 core.
  • Novaoblivion - Monday, December 20, 2004 - link

    For anyone who wants it the link on Nvidia's site seems to working I just downloaded it.
  • Cybercat - Monday, December 20, 2004 - link

    How does the 6800 have acceleration support if it's also based on the NV40 core?
  • skunkbuster - Monday, December 20, 2004 - link

    "At the same time, ATI sent us information on how to enable hardware acceleration of WMV9 on their cards before the forthcoming WMP10 update."

    would someone care to share this with the rest of us ?
  • KnightBreed - Monday, December 20, 2004 - link

    I hope nVidia plans to add support for decoding MPEG4-AVC HP at some point. Whether it's this product line or next, MPEG4 will be important for next generation optical media (whether it's HD-DVD or Blu-Ray).
  • LoneWolf15 - Monday, December 20, 2004 - link

    What makes me truly upset is that so far, the sites reviewing PureVideo has not take a stand for the consumers that own the 6800 and were promised the full PureVideo featureset by nVidia. Rather, sites are reviewing the tech, and ducking the issue, as if they are more concerned about continuing to receive nVidia products for review than they are for us. Who's looking out for the little guy?

    P.S. Anandtech's review states that the 6800 Standard has a fully functional video processor --this isn't fully true, as the AGP version according to nVidia's website, does not.
  • jamawass - Monday, December 20, 2004 - link

    Great review. Even though Nvidia doesn't always win the deinterlace test, it wins on picture quality in most tests.Looks like a 6600 Nvidia will be replacing my ATI as the next video card in my htpc.
  • Aquila76 - Monday, December 20, 2004 - link

    That is so retarded that it doesn't fully work on the 6800GT/Ultra. Why would they cripple their high end cards? I guess since they aren't very available it doesn't really matter. Hope they add the rest of the functionality to new revs of these cards.
  • GnomeCop - Monday, December 20, 2004 - link

    wow I guess they will get away with touting this feature on the AGP 6800Ultra/GTs , even though it doesn't fully work after all.
  • jg123 - Monday, December 20, 2004 - link

    I don't see a link on Nvidia's website for a trial mentioned in this article.

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