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Color Correcting Proxy Media

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Ben Withington
Color Correcting Proxy Media
on Jun 14, 2013 at 6:34:58 am

Hi, I recently shot a short film on the 5dmk3 (pre clean HDMI firmware unfortunately) and have been figuring out a good workflow for color correction and grading that keeps the quality of my footage as good as it can be but also not tax my machine.

After reading and doing some tests, I'm thinking I have a good way to go. However, I want to make sure my inexperience isn't blind-siding me.

-First, I convert an XML of my timeline into a script for After Effects.

-I convert all the native 8 bit H.264 to 16 bit, noise reduce it, and render out lossless to the animation codec.

-Import the footage into a new event in FCPX and transcode it all to proxy media. (This is where I'm unsure if I'm reversing the benefit of upconverting the footage and that it'll be akin to color correcting the original files. When FCPX says that the proxy media is 422, does that mean it's transcoding my RGB footage to YUV and retaining the 16 bit color space?)

-Color correct, grade, sharpen, and add film grain to the footage.

-Reconnect to original media and export.

Thanks for any insight on the subject. I'm a little confused from the different tutorials and advice I've been reading concerning the benefits of upconverting the color space and how that interacts with FCPX's 32 bit float environment. If I'm correct, upconverting gives you the headroom to push and pull the image while the 32 bit in FCPX is only for the rendering stage.


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Nikolas Bäurle
Re: Color Correcting Proxy Media
on Jun 14, 2013 at 10:58:49 am

FCPX is a 64 bit application. Upconverting doesn't really give you any benefits when colorcorrecting. If the source is compressed, isn't going to make the image itself better.

In my opinion there's no reason to use any third party apps to convert footage in X. It optimizes the footage for you, and you can easily switch between proxy and optimized.

"Always look on the bright side of life" - Monty Python



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Ben Withington
Re: Color Correcting Proxy Media
on Jun 14, 2013 at 2:32:18 pm

That FCPX is 64 bit is referring to the fact that it is able to take advantage of 64 bit processors. When I say 16 bit, I mean 16 bpc or 16 bits per channel, referring to the color channels of the footage. I think the idea is that upconverting doesn't changing anything within the image, no, but it does give you head room to preserve pixel quality and have cleaner results form the information that is added to the image by color correction and grading.

I don't mind compression artifacts when I'm correcting and grading, I just want to make sure that what I'm seeing in terms of color and contrast ratios will be identitical when I reconnect. You know, like pushing the image to where it posterizes the proxy media but not the original media.


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Nikolas Bäurle
Re: Color Correcting Proxy Media
on Jun 14, 2013 at 3:56:44 pm

I just tried it out, the proxies keep 16bit. Interesting, the h.264 from my 7D are all 16 bit...?

Whatever you do to the proxies should look the same when you switch back to optimised, but I only use FCPX when dealing with h.264, I don't know what happens when you go through AFX.


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Nikolas Bäurle
Re: Color Correcting Proxy Media
on Jun 14, 2013 at 3:42:35 pm

I was referring to your last paragraph, but I just realize my brain was somewhere else, your are talking about rendering.

I was wrong, I just talked to one of our graders, yes, you benefit from upconverting. I always convert to ProRes, so I have never compared.

Why don't you first import the footage in FCPX and let it optimize it for you to ProRes. I don't get why you would create an animation codec in AfterFX.


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Ben Withington
Re: Color Correcting Proxy Media
on Jun 14, 2013 at 4:56:18 pm

I think I forgot to mention that I'd like the footage to hold up as best it can on a big screen in HD projection. If this was online or disk distribution only, I'd definitely go with ProRes. I admit this is out of speculation on what little I know and it could be way off base, but my reasoning is as follows.

422 (HQ) guarantees no compression artifacts to be visible on the first generation; evidently there is quality loss even though it's imperceivable. However, since my source is highly compressed H.264, I would have three generations of compression in my workflow: the H.264 in camera, the transcoded format for color correcting, and the final export. Even though artifacts can't really be seen in either iteration of 422, I wondered if that holds with the kind of scaling that happens with projecting for a larger audience than a 1080p monitor.

So, I thought it might be a good idea to use the animation codec. This way I know there is no quality degradation regardless of whether I can see it or not and the final export will be as close in quality to the original H.264 file as possible and I have more wiggle room in the compression of the final export depending on a venue's specifications.

The only problem is that I couldn't edit animation files cause they're too darn big. I just needed to make sure the proxy media would show me the correct responses to my color correction so I wouldn't get surprises when reconnecting. Thanks for testing the process out by the way, I don't know why I couldn't figure out how to check the color space of the proxy footage.

So that's my theory anyhow. Definitely let me know if I'm making more work for myself than I need. I certainly wouldn't miss the extra step of using After Effects, but absolutely making sure the quality stayed as close to first generation as possible seemed important to me for this kind of project.


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Nikolas Bäurle
Re: Color Correcting Proxy Media
on Jun 14, 2013 at 7:17:30 pm

Using ProPres 422 (HQ) should give you a clean image, at least on an HDTV. I wouldn't worry too much about the very slight loss in quality, you really won't see it.

i haven't projected in HD, but i do remember screenings of DVDs in PAL always looking good for SD.

the Proxies will keep the same color space. I haven't worked with AFX Animation codec, but when using ProRes I see no difference, the color correcting I do looks the same when I switch back to optimized. FCPX deals with color very well.


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Nikolas Bäurle
Re: Color Correcting Proxy Media
on Jun 14, 2013 at 4:23:24 pm

You could export ProRes444. i don't know about the animation codec from AFX


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Ronny Courtens
Re: Color Correcting Proxy Media
on Jun 16, 2013 at 7:19:28 pm

The Animation codec only supports a total of 32-bits per pixel (= 8-bits per channel), it does not support 16-bits per channel. This means that going through AE and exporting using the Animation codec is not a very good workflow in your case.

Just import your footage in FCPX without the roundtripping. If your system is fast enough you may be able to edit your H.264 media natively, also depending on how long and complex your timeline is. If you cannot edit natively you don't necessarily need to optimize to ProRes either. You can create Proxies (like you are doing now) and work with the Proxy media. As has been pointed out the Proxies will retain 16 bpc. When the edit is locked you can switch back to original media for final check and output. Of course, if you wish, you can always optimize to ProRes as well. That's entirely up to you.

However you proceed this workflow will give you only one conversion generation if this is your main concern. Although I can certify from experience that ProRes 422 withstands multiple generations without visual quality loss, even when projected onto large screens in HD.

Best wishes,

Ronny



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