Ingest workflow: Alexa / ProRes HQ / Avid / Windows

[Job Ter burg]

I would not opt to work in ProRes on Win, You cannot generate ProRes on Win (thank you, Apple), so your titles and renders would need to be in a different codec, which is not great when you need to do self-containee exports. Also, you would only be able to import as ProRes if they shoot 1920×1080 – if they shot 2K, it needs to be scaled back to 1920, so that wouls require a transcode anyway.

I would say there are two ways to go about this.

1. AMA-link to the files, select the clips in the bin, apply LUT as needed, select Clip-Transcode and transcode the clips to a DNxHD flavor of your liking (DNxHD36 would be great for offlining in HD. Conform can be either done in MC by relinking to the original ProRes files after completing the cut, or via AAF or EDL to a third party conform and grading tool (Resolve, Scratch, BaseLight, NuCoda, etc.).

2. Use a 3rd party tool (many available, Resolve Light does this as well) to apply LUT and transcode to DNxHD Avid MXF media. Conform can be done inside MC by relinking to the original ProRes files (slightly more hassle as you need to relink source file names to tape names), or in a 3rd party conform & grading tool.

[Pat Horridge]

I’d agree with Job. Avoid Prores on the PC. Go the dnx36 offline route. Dnx36 looks really good and your system will be more responsive with dnx low bitrate media.
Check the conform process with who ever is doing the conform and grade and ideally do a test first.

Pat Horridge
Technical Director, Trainer, Avid Certified Instructor
Free online Tutorials at VET digital media academy online https://vimeo.com/channels/752951
VET
Production Editing Digital Media Design DVD
T +44 (0)20 7505 4701 | F +44 (0)20 7505 4800 | E pat@vet.co.uk |
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[Jon Hensen]

Job and Pat thank you.

DNx it is. I just spoke with the DP and they baked in a LUT for the footage. Will I need to do anything additionally during transcode to make sure that information is retained? Will the transition through offline to online pose any problems for this?

In a perfect world I’d like to do everything within MC. Possible? Probable? Advised?

Thanks!

[Pat Horridge]

Yes you need the same LUT and apply it in the source settings for the AMA’d clips before you transcode.

Pat Horridge
Technical Director, Trainer, Avid Certified Instructor
Free online Tutorials at VET digital media academy online https://vimeo.com/channels/752951
VET
Production Editing Digital Media Design DVD
T +44 (0)20 7505 4701 | F +44 (0)20 7505 4800 | E pat@vet.co.uk |
http://www.vet.co.uk | Lux Building 2-4 Hoxton Square London N1 6US

[Job Ter burg]

“they baked in a LUT for the footage” – if they baked in the LUT, there’s nothing for you to add or change. Unless they don’t really mean they baked it in. A bit vague, the idea of a LUT is NOT to bake it into the production source files.

“I’d like to do everything within MC. Possible? Probable? Advised?”
Can be done. If they did in fact bake in a LUT and you’re getting Rec709 sources that they want to finish in Rec709, you can just pull everything through MC.

If they did not bake in the LUT, you can still work in MC, add the LUT there, but you will not have the advantage of the Log-C color space that you would in finishing tools.

[Job Ter burg]

Not if that LUT is already baked in, methinks.

[Pat Horridge]

If the DP was supplying Transcoded files then baked in LUT makes sense. if it’s the source files then surely they mean a LUT has been applied and therefore the LUT needs to be used to ensure the Transcoded footage now looks “normal”

Pat Horridge
Technical Director, Trainer, Avid Certified Instructor
Free online Tutorials at VET digital media academy online https://vimeo.com/channels/752951
VET
Production Editing Digital Media Design DVD
T +44 (0)20 7505 4701 | F +44 (0)20 7505 4800 | E pat@vet.co.uk |
http://www.vet.co.uk | Lux Building 2-4 Hoxton Square London N1 6US

[Jon Hensen]

The picture is getting clearer.

I’ve just done my first preliminary batch of transcoding to assess the results.

What I’m seeing is this…

COLOR SPACE:
Arri ALEXA LogC (AMA CLIP)
ARRI Log-C gamma [64-940 (8bit)] (Transcoded DNxHD36 clip)

COLOR TRANSFORMATION:
ARRI ALEXA LogC to REC 709

I was provided with source ProRes HQ files. It was confirmed they did in fact apply a look in the field. The resulting REC709 image is incredibly crushed and saturated which is worrying. I remove the color transformation in the settings and get back to the LogC look taking us back to a blank canvas.

I guess my next question is if I am missing anything metadata-wise during ingest? Is MC seeing the applied look correctly? Is this REC709 just a stock LUT in the camera which is the culprit for the across the board satuaration issues?

One more little piece of information is that this was all shot on an AMIRA not an ALEXA (apologies). I don’t know how much that changes things. I found little literature on this latest and greatest of ENG cameras.

Thanks Job and Pat.

[Pat Horridge]

That doesn’t sound correct. Looking at Log-c footage as REC709 with no LUT applied at your end should give you washed out de-saturated images. Blacks lifted whites low.

It sounds to me like the footage you have is actually REC709 but flagged as having a Log0C LUT applied. Applying the Log0C to REC709 LUT your end is expanding out what is a REC709 image already.

You need to resolve this ASAP as it’s likely something is wrong at the acquisition end.

If you have a way of uploading a small clip I can look and let you know what’s what.

Pat Horridge
Technical Director, Trainer, Avid Certified Instructor
Free online Tutorials at VET digital media academy online https://vimeo.com/channels/752951
VET
Production Editing Digital Media Design DVD
T +44 (0)20 7505 4701 | F +44 (0)20 7505 4800 | E pat@vet.co.uk |
http://www.vet.co.uk | Lux Building 2-4 Hoxton Square London N1 6US

[Pat Horridge]

Got the smaple clip you sent.
It looks fine.
The source setting window identifies it as Arri Log-C and adds the log-c to rec709 transformation. on the RGB display levels look good.
If you click bypass transformations you see sat up blacks and lower whites but more detail in the sky and clouds as expected.
So with the transformation in place it looks more “normal”
Good to go I’d say.

Pat Horridge
Technical Director, Trainer, Avid Certified Instructor
Free online Tutorials at VET digital media academy online https://vimeo.com/channels/752951
VET
Production Editing Digital Media Design DVD
T +44 (0)20 7505 4701 | F +44 (0)20 7505 4800 | E pat@vet.co.uk |
http://www.vet.co.uk | Lux Building 2-4 Hoxton Square London N1 6US