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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  • MDme - Monday, December 20, 2004 - link

    Hey Anand, why not suggest to nVidia that owners of 6800 series GPUs be able to download the codec and just have their serial #'s or proof of purchase? I mean, they shouldn't tout a feature that you need to pay extra for?

    They already screwed us 6800GT/U owners with a "broken" feature, now they wanna screw us 20$ more to get the "broken" feature?

    We need a petition site!!!!!
  • Guspaz - Monday, December 20, 2004 - link

    I was under the impression that the deinterlacing was done by the DVD decoder app itself. So would not the results differ from WinDVD to PowerDVD to Zoom? Also would have been nice to compare it to other modes of software deinterlacing such as motion compensated.

    Something that I didn't see mentioned in the article is that while the hardware deinterlacing is certainly a win for nVidia, ATI wins the WMV9 acceleration category, as I'm pretty sure that all R3x0 cards support it back to the 9500/9700. That means that ATI's WMV9 market penetration is way higher than nVidia's, since very few nVidia cards can do the acceleration.
  • Klaasman - Monday, December 20, 2004 - link

    Nevermind. Found info at Nvidia.

    "The new software will upgrade the decoders in ForceWare Multimedia 3.0 to access the new features in the NVIDIA DVD Decoder. The NVIDIA DVD Decoder will not upgrade NVDVD 2.0 as it was a separate application based upon an old architecture."

    They want me to pay twice for it I guess. Greedy bastards.
  • Klaasman - Monday, December 20, 2004 - link

    I got a copy of NVDVD with my eVGA 6800GT. How do I update the DVD codec? When I install the new version from Nvidia, it still asks for credit card info and stuff.
  • jonny13 - Monday, December 20, 2004 - link

    "NVIDIA's DVD decoder has always been $20, unfortunately I don't know of a single manufacturer that gives away their DVD decoders for free."

    I know that their DVD decoder has always been $20. But, they never specified that you would need to pay extra for a feature that they touted for months. Thats like making you pay for a special driver to get PS3.0 to work. If they advertise it as a feature on a card I am paying $500 for, it better damn well be free and not another 20 f'ing dollars.

  • b3roldan - Monday, December 20, 2004 - link

    I'm really disappointed with the 6800s not having the wmv9 decoding... was gonna get myself a 6800U for xmas. I was reading on the X800XT-PE coz there's a Sapphire X800XT-PE relatively cheaper than most 6800Us in

    Then I came accross this webpage that says the nv48 is still coming...

    hehe... I guess I can wait 3 months for the nv48, but then with the R520 just around the corner... man buying a card is starting to become a tough decision.

    neways... I was wonderin if neone could confirm this information on the hardware flaw...
  • RCIEGR - Monday, December 20, 2004 - link

    You missed one very important feature to me.
    The 6800gt lacks the true hd output formats in component video output. I have a 6800gt and these card didn't include the special 10-pin din connector to the hd-component/s-video/composite adaptor plug. My freind at work bought a 6600gt(Chaintech) for his son for xmas, so I borrowed the card for a test this last weekend. Having a old school sony KDP-57XBR2 HDTV with only firewire and 2-hd component vidoe imputs. The true hd-output of the 6600gt is way more important of a feature to me then the wmv9 decoding.

    The output over component(both true 1080i & 720p; the sony can nativly handle both) looked very good, for both hd video(surferp****.com), hd tapestreams recorded from the firewire output of the mot-6208 hd-cable box and the latest games, once you figure out how n-view works and you get the game resolutions correct.

    anand, take a close look at the reference 6800gt cards and I think you will see the 10-pin din connector.

    I want a RMA for a 6800gt with the true hd-output with component video. eVGA does have a 90-day upgrade program. Maybe a 6900gt will show up quick?

    Thanks for you time
  • MDme - Monday, December 20, 2004 - link

    Well, my XFX 6800GT didn't come with the NVDVD decoder. it's a shame nVidia sells a very expensive video card and tout's this feature but doesn't include the software to make it work.

    I think nvidia should know how it's customers feel. after all we were the early adopters. it's one thing to have a partially working feature but it's totally a rip-off not to have it at all!!!! $400 for a video card and you need to pay more for software to make it work? :(

    Hope Anand can be a voice for us.
  • ViRGE - Monday, December 20, 2004 - link

    Anand, check the final X800 press presentation slide-show/PDF, it was in there somewhere last time I read it.
  • sheik124 - Monday, December 20, 2004 - link

    nVIDIA has really done it this time. #29 mentioned ATI not doing their part, but at least the features they advertised and are slowly deploying work on ALL OF THE GPUs. nVIDIA owes us something for the false advertising, they've really wrecked my day, I paid for something, and I expect to have it, not half of it.

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