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    #21
    Senior Member Nick_Shaw's Avatar
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    I did some tests pulling keys with Keylight in Shake from both the uncompressed and RedCoded images. Both gave fantastically good results, with the mattes being visually indestinguishable at 1:1.

    With exactly the same parameters on Keylight, doing a difference between the mattes showed tiny differences, but nothing that would affect the result for a viewer.

    Nick
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    -----------------------------------------------------------------------------------------------
    Advisor to Convergent Design on LUTs and image processing for the Odyssey


     

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    #22
    Red Team Graeme_Nattress's Avatar
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    I don't think people fully realize the danger that the YCbCr + chroma sub-sampling does to an image. It rips it apart from it's heart. Even with DCT based codecs you get better results staying 444 YCbCr and just compressing the chroma channels twice as much. Subsampling (as with interlace) is woefully inefficient compression.

    Graeme
    www.nattress.com - Film Effects and Standards Conversion for FCP
    www.red.com - RED - 4k Digital Cinema Camera


     

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    #23
    Senior Member taubkin's Avatar
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    Thank god we don't need it anymore... God bless the end of NTSC!


     

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    #24
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    I think somebody should write a wikipedia article on Graeme Nattress.

    Any takers?


     

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    #25
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    "I don't think people fully realize the danger that the YCbCr + chroma sub-sampling does to an image. It rips it apart from it's heart....Subsampling (as with interlace) is woefully inefficient compression." Graeme

    Does this mean that RED footage shot in progressive mode will fall apart when converted to the current interlaced NTSC SD broadcast standard, eliminating or reducing the benefits of downsampling from 4k and its original creamy goodness? If RED footage is destined for SD interlaced broadcast, will originating in 1080i be the best alternative?


     

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    #26
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    Quote Originally Posted by billg
    Does this mean that RED footage shot in progressive mode will fall apart when converted to the current interlaced NTSC SD broadcast standard, eliminating or reducing the benefits of downsampling from 4k and its original creamy goodness? If RED footage is destined for SD interlaced broadcast, will originating in 1080i be the best alternative?
    RED will look wondeful downrezed to NTSC (already tried it). Just make sure you use a high quality filer or high sample rate so you don't get zingy edges. And yes stay progressive and then cine-expand (add 3:2 pulldown) once you're in SD. Most SD tv content is shot progressive (on film @ 24p) and cine-expanded in telecine (this is sometimes done in the online, or through a standards converting box, but most of the time it happens in telecine during your one-light transfer or select scene transfer.) Most people would (and should) choose to stay for progressive for as long as possible.


     

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    #27
    Junior Member Bro Anansi's Avatar
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    If destined for broadcast, why not avoid the potential motion artifacts of pulldown and just shoot 30p?

    Ian Sun
    Anansi Moving Images
    Red #1073
    Last edited by Bro Anansi; 11-23-2006 at 10:59 PM.


     

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    #28
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    30p is probably where I'm headed.

    I just finished a documentary this past summer that was produced in 30p on a DVX100A and broadcast on public television. It was okay, but, of course, it looks better on DVD played on a progressive DVD player.

    All of my experience is with video, and I'm not invested in making my stuff mimic the 24 fps cadence of film. I prefer the more immediate look of 30p and wonder whether, before long, it will be the dominant aesthetic in most genres--or the ones I'm interested in--anyway. As far as I'm concerned, I'd rather not be limited by the stu-stu-stuttery look of anything but the slowest of pans and action.


     

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    #29
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    For distribution, chroma subsampling may not be a bad idea.
    --At (very) low birates with DCT-based compression, you are better off having lower resolution (and more bitrate/pixel) than having high resolution. You see this effect in web streaming clips (even when you full screen them).
    --For delivery for television, chroma subsampling works well for analog interfaces (which accept signals with chroma subsampling, such as component Y'PbPr and composite NTSC and composite PAL).

    For digital cinema acquisition, Redcode demonstrates that chroma subsampling is a bad idea. Better quality AND lower bandwidth with Recode VS uncompressed 4:2:2.

    For broadcast acquisition, uncompressed 4:2:2 may not be that bad an idea for workflow reasons. If the online system doesn't accept your data format (i.e. XDCAM is IT-based but most online systems won't take it), then your next best bet is SDI ingest.

    2- With uncompressed 4:2:2, you don't lose a lot of quality. Even arguably with the really bad implementation of 4:2:2 in Apple's uncompressed codecs.

    3- Interlacing on the other hand is something you should be much more concerned about. It's not good for acquisition for VFX work.
    When you also want chroma subsampling, interlacing interacts with it. So with 4:2:0, you may get worse performance than 4:1:1. Chroma subsampling is less than half as efficient/good.
    Many display devices will de-interlace the signal poorly, resulting in artifacts or resolution loss.

    (Just my opinion.)


     

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    #30
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    If destined for broadcast, why not avoid the potential motion artifacts of pulldown and just shoot 30p?

    30p doesn't convert to PAL well. Ideally, you want to sell internationally (to make more money) so shooting 24p can be a better idea for that reason. If your material is unlikely to end up in PAL, then 30p may not be a bad idea.


     

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