A Brief Look at De-Interlacing Modes

The process of taking interlaced content and displaying it in a non-interlaced form is often referred to as de-interlacing (for obvious reasons). There are two basic methods of de-interlacing, commonly known as "bob" and "weave."

Bob de-interlacing is more technically referred to as linear interpolation and it simply fills in the missing lines of resolution by interpolating between the resolution lines that are available. This interpolation form of de-interlacing is particularly useful if there are a lot of solid colors on the screen and if the decoder screws up and decides to combine two fields from different frames.

Weave de-interlacing, as the name implies, simply combines alternating lines of resolution from two separate interlaced fields. Using either method individually is generally not the best way of doing things, but thanks to the decent amount of power in today's PCs more sophisticated algorithms can be implemented to dynamically switch between bob and weave on a per pixel basis within a frame (usually referred to as adaptive per pixel de-interlacing).

NVIDIA's PureVideo supposedly takes adaptive per pixel de-interlacing one step further with what they call Spatial-Temporal de-interlacing. The idea here is that normal per pixel adaptive de-interlacing uses data from fields within a single frame to essentially fill in the blanks. NVIDIA's Spatial-Temporal de-interlacing can use data from fields in other frames to improve de-interlacing quality. We'll have to see if this ends up improving quality or not in our tests later in the article.

Frame Rate Conversion and You NVIDIA's PureVideo Driver and Encoder
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  • Anand Lal Shimpi - Monday, December 20, 2004 - link

    gordon151

    I should have made this more clear, I used the NVIDIA codec for NVIDIA's tests and I used ATI's codec for ATI's tests. I used Zoom Player for both of them.

    ViRGE

    They never briefed me on anything like that but I can always ask :)

    Take care,
    Anand
  • ViRGE - Monday, December 20, 2004 - link

    Thanks Crimson, but I'm talking about the video features, not the elusive cards themselves. ;-)
  • crimson117 - Monday, December 20, 2004 - link

    #29: http://anandtech.com/news/shownews.aspx?i=23531
  • ViRGE - Monday, December 20, 2004 - link

    I know this is an Nvidia article Anand, but could you get on ATI's butt about their lack of features too, and find out what's going on? When the X800 was launched, ATI was talking about decode acceleration for MPEG4 along along with some sort of encode acceleration(i.e. all the features NV promissed but never delivered on). I'm curious to know what happened to that, and if we're going to get something new out of ATI besides WMV acceleration.
  • gordon151 - Monday, December 20, 2004 - link

    I was wondering why AT's results were different than PCPers and just noticed they used MMC & 4.12 while AT used the nVidia codec and player for both cards tests.
  • Anand Lal Shimpi - Monday, December 20, 2004 - link

    Ytterbium

    I've asked numerous times, never gotten a response. I'll try again :)

    For those of you who are wondering, I have asked NVIDIA what their official statement is to early 6800 adopters, but that has also been met with no response.

    Take care,
    Anand
  • Ytterbium - Monday, December 20, 2004 - link

    I'm dissapointed that the encode function never made it, that was a killer feature. Any idea if it will come?
  • Spike - Monday, December 20, 2004 - link

    Thanks for that! I have the BFG 6800 GT and on the BFG cd there is the nvDVD software. It's nice to know I can actually use the VP that I paid for!

    -spike
  • Gatak - Monday, December 20, 2004 - link

    Here are some examples of interlacing artifacts when redering on a progressive screen:

    1) http://moment22.mine.nu/interlace_1.jpg

    Most software DVDs either blend or remove one of the fields by some partial de-interlacing algorithm. nvidia's DVD decoder does it ok. The image is sharp but still leaves only half framerate.

    2) http://moment22.mine.nu/interlace_2.jpg

    But in reality, half temporal resolution is lost. What should have been done is to render each field as a separate frame.

    3) http://moment22.mine.nu/interlace_3.jpg
  • Anand Lal Shimpi - Monday, December 20, 2004 - link

    Spike

    I wasn't aware that the 6800s are coming with NVDVD, in that case you are good to go. Just download the updated version (1.00.67 is the official version) from the website.

    Rand

    The full system was configured as follows:

    Intel Pentium 4 570J
    Intel D915GUX Motherboard
    2 x 512MB DDR2-533 DIMMs
    Intel HD Audio Enabled

    Windows XP SP2 w/ DX9c

    Take care,
    Anand

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