Thread: Oops! BRAW isnt Raw Its a YCbCr codec

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  1. #21  
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    Yea Denny, but that doesn't really necessitate a colorspace swivel to cause visual aberrations like this, so your aloof tone just makes you seem like you're unaware of the how unexpected this sort of thing was.
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  2. #22  
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    Quote Originally Posted by weui View Post
    I think the main advantage is that you can easily reduce the resolution or compress the Cb and Cr channel without a big visual loss. That's the idea behind 422 and 420. I think most compressed codecs are YCbCr for this reason. It's interesting that CDNG 3:1 does still seem to be RGB. I guess CDNG only allows RGB and that switching to YCbCr with BRAW may have made some of these big improvements in compression possible for BMD.

    Maybe BRAW only switches to YCbCr after a specific compression ratio, say up to 5:1 it's RGB and then 8:1 and more is YCbCr.
    YUV encoding was developed to reduce analog broadcast color bandwidth to fit within the same allotted 6MHz channel space as monochorme TV broadcasts. It takes about half the bandwidth of RGB. So even without subsampling it is more efficient.
    It is amazing to consider how far compressed digital codecs have developed since then. The RF broadcast signal has not changed significantly since NTSC was standardized. Yet in that same 6MHz channel space still running the same 3.5MHz line clock as NTSC analog broadcasts most stations now transmit a 1080i or 720p HD channel AND two standard def 720x480 channels or the equivalent in data services. Now with HEVC we can do 4k in the same space.
    Last edited by razz16mm; 09-21-2018 at 02:20 AM.
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  3. #23  
    Senior Member Frank Glencairn's Avatar
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    Having shot and worked with BRAW since quite a while now, it highly doubt that it is Y’CbCr.

    Wouldn't make any sense also.

    One of the big advantages of a undebayered image is, that it is only black and white, so the data rate is way lower than a debayered image.
    If you want to make a low data rate codec, why would you throw that advantage out of the window, and than counter it with loss of image information by even more compression? So you would ether raise the data rate with Y’CbCr (compared to a undebayered image), or asking for compression losses/artifacts.

    That's nothing BM would develop as a new flagship codec, it's totally against their DNA as I know it.
    Also we already have that since years, it's called ProRes and DNX - why make an other one?

    I guess (out on a limb), gradient prediction, and denoising is done in camera (denoising is probably a necessary step to get efficient compression),
    but the actual debayering (interpolation) is still done in Resolve.

    And yes, I can see the ringing, but that could also be the compression, when they use a wavelet algorythm - I remember seeing that with Cineform raw almost a decade ago.
    Last edited by Frank Glencairn; 09-21-2018 at 04:51 AM.
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  4. #24  
    Senior Member Samuel H's Avatar
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    ^That makes a lot of sense. In any case, the bottom line is that you can get some color fringing artifacts when shooting BRAW that will be avoided when shooting cDNG. I think I'll use BRAW 6:1 most of the time, BRAW 12:1 for whenever I want to save storage space, and cDNG for green screen.
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  5. #25  
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    Even if it is wavelet-based compression causing it, the problems are showing up in the lossless q0 version. This is definitely doing something weird and degenerative to image quality.
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  6. #26  
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    Quote Originally Posted by Frank Glencairn View Post
    I guess (out on a limb), gradient prediction, and denoising is done in camera (denoising is probably a necessary step to get efficient compression),
    but the actual debayering (interpolation) is still done in Resolve.
    That's exactly where I'm leaning towards when it comes to how the de-bayering process is split.

    For what it's worth, after converting the CDNG's from that test to several different codecs, all the RGB ones produced no ringing while the Y'CbCr ones did. I don't know what other things, if any, are common between those codecs though.

    Also there is a slight ringing in the CDNGs as well but it's very subtle by comparison.

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  7. #27  
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    If these are both supposed to be lossless then why is one quite obviously markedly worse than the other? It obviously has less detail and more imaging errors.

    CDNG.JPGq0.JPG

    Say what you will, but this isn't RAW. It's clearly doing some colorspace swivel or subsampling to cause this.
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  8. #28  
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    Would be nice to have some sort of BRAW whitepaper with some details.
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  9. #29  
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    Quote Originally Posted by Danji View Post
    If these are both supposed to be lossless then why is one quite obviously markedly worse than the other? It obviously has less detail and more imaging errors.
    Nobody ever said BRAW was lossless. Everybody knew it was lossy.
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  10. #30  
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    Quote Originally Posted by Myownfriend View Post
    Nobody ever said BRAW was lossless. Everybody knew it was lossy.
    Doesn't sound very raw to me, at that point.
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