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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  • mcveigh - Tuesday, December 21, 2004 - link

    nserra: where do you get your info on mpg4 from? Reply
  • tfranzese - Tuesday, December 21, 2004 - link

    I guess giving you the hardware features now means you should be entitled to the software to take advantage of it as well, huh?

    Those of you who think you're entitled to nVidia's DVD decoder are living in la la land. So now they should also give you the games that take advantage of their technology/features too?
    Reply
  • Koing - Tuesday, December 21, 2004 - link

    Just don't buy an Nvidia card next time if you feel ripped off.

    You paid 'expecting' a feature to be 'fully' and not half 'assed' in to work 8 months late.

    Protest with your WALLETS.

    <-- never an early graphics adopter!

    Still with my Nvidia GF4Ti4200 :P

    Koing
    Reply
  • nserra - Tuesday, December 21, 2004 - link

    http://www.ati.com/vortal/videoinnovations/flash/i...

    #29 VIRGE
    Ati have MPEG4 encoding and decoding since 18/07/2002 so what do you want?

    S3 Omni is better at video then Ati of Nvidia the problem is the rest.... even so, to bad there isnt an S3 in the tests.

    I dont know why nvidia doesnt charge some buck or two for each chip/card it makes, so the feature get paied?

    Unless this enconder software that they are charging, works on any card in the market, if its the case they are right in doing so.
    Reply
  • LoneWolf15 - Tuesday, December 21, 2004 - link

    Anand,

    I think you would do your readers a great service by retesting all of this on an AMD processor. Your Pentium 4 rig had Hyperthreading on, making this issue look far les serious than it is. Hyperthreading P4 chips report far lower CPU utilization numbers as opposed to even high-level Athlon 64 processors. So those of us with a Geforce 6800 who are running high-end AMD hardware are getting 70-100% CPU utilization in WMV9. It explains why a lot of us are having trouble trusting nVidia now, and in the future.
    Reply
  • atssaym - Tuesday, December 21, 2004 - link

    NVDVD =/= NVIDIA DVD Decoder, they are TWO DIFFERENT THINGS

    link
    http://nvidia.com/object/decoder_faq.html#othernv

    Will this product work with NVDVD and ForceWare Multimedia?
    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.

    Decoder Homepage
    http://nvidia.com/object/dvd_decoder.html
    NVDVD Homepage
    http://nvidia.com/page/nvdvd.html
    Reply
  • pataykhan - Tuesday, December 21, 2004 - link

    Nice comparison of ATI and NVIDIA

    But still one thing is missing. I use cyberlink powerdvd for watching dvds. My question is that if i have got nvidia or ati dvd decoder. Should i use hardware accelerated decoder or should i stick with cyberlink decoder.

    Cyberlink has implemented some smart software deinterlacer and image quality enhancer (CLEV-2). So i would like to see the image quality differences between hardware/software decoders available.
    Reply
  • bigpow - Tuesday, December 21, 2004 - link

    This sucks...

    ATI doesn't charge $20 for the claimed decoder/accelerator...

    And they have the ATI HD component dongle too!
    Reply
  • segagenesis - Tuesday, December 21, 2004 - link

    Bah, I would be kind of pissed if I had a high end $500 card only to find out now its more worthless than a sub $200 card at decoding video. A bit of shame on nVidia. Reply
  • Guspaz - Monday, December 20, 2004 - link

    Oh, as a clarification of my previous comment (#41) I meant that I was under the impression that normally the DVD decoding software handled the de-interlacing, obviously PureVideo overrides that. But what I mean is on ATI cards, without any type of hardware de-interlacing, wouldn't the deinterlacing differ from decoder to decoder? Reply

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