Transcoding red files

Posted by emilyelaine 
Transcoding red files
July 02, 2009 06:47PM
I've got my log an transfer open and I need to transcode from red files to prores 1280x720p 23.98. The only options in the preferences are prores 422 hq and prores 422 but it transfers them to 2048x 1024. I have limited space on my drive. So just wondering where in fcp I can change these settings.

Re: Transcoding red files
July 02, 2009 07:22PM
It's not a good idea to use log-and-transfer to get Red material into Final Cut. I'll skip the details, but suffice to say the workflow just isn't there.

You say you want to go from R3D to 720p ProRes, but you don't say whether this is for an offline or an online. If it's just an offline, no problem, but if it's an online, you're going to have to incorporate a color grading step into your processing. R3D files are 12-bit linear with raw sensor data, while ProRes is 10-bit linear YUV. So that conversion throws away a lot of data. You're going to want to take care if this is for your online.

If you're just offlining, the tool you want to use is REDrushes. It'll let you batch-convert a lot of R3D files to ProRes. What it does NOT do is let you do any sort of one-light (or best-light, for that matter) color grade. For that, you need to use REDAlert to create an RSX file that corresponds to your look; REDrushes will pick up the RSX file and apply that look when it transcodes.

REDrushes is also where you make your debayer choice, as well as setting your color and gamma space. Be aware that if you didn't shoot this stuff yourself, you really need to double-check the color and gamma spaces. I've yet to get an R3D file that had the right combination of color and gamma space set in-camera.

Finally, REDrushes is where you decide how you want to handle the aspect-ratio difference between 2K 2:1 and 720p. You can either fit-width (which adds a slight letterbox) or fit-height (which does a simple center-cut).

Oh: And if you're offlining, make liberal use of the timecode burn-in feature in REDrushes. It'll save your life somewhere down the line, most likely. Always has for me.

Re: Transcoding red files
July 02, 2009 07:36PM
It is for offline. I didn't shoot it. How do I find out what the color and gamma space is? Call the dp?

Re: Transcoding red files
July 02, 2009 07:47PM
If you really want to go to 720p route you use RedRushes or Clipfinder to batch convert to 720p pro res.

I personally would do this assuming of course it was shot 4k, and definitely offline only.

-1/4 debayer
-using edgecode
-1280x720 fit to width
-(optional---- burn in of file name/edgecode/TOD TC @ height 2%, origin .5%)

If this was shot 2:1 you will have black bars top and bottom, which is great for burn ins.... if it was shot 16x9 or 4khd, I would skip the burn ins.

There is no need to know camera settings or do any sort of 1 light correction IMO -of course, again if this is strictly offline.
Re: Transcoding red files
July 02, 2009 07:54PM
If you're just offlining, then it's not as important. You could call the DP, but there's a very real chance (ESPECIALLY if this was a rented camera) that he won't know. Red cameras are complicated as hell, comparatively speaking.

Two scenarios. Either (a) you're in a situation where it really doesn't matter how your offline looks, or (b) your client is gonna have a hard time seeing your edit because of all the ungraded footage.

If you're in (a), just set the look source to "camera," the color space to "REDspace" and the gamma to "REC709" and get on with your life. The footage won't look right (because it's ungraded; it's equivalent to just processing a 35mm neg without setting the lights) but it'll be fine.

If you're in (b), consider taking each R3D into REDAlert and doing a basic one-light color grade on it. Set the ISO and exposure so it looks more-or-less properly lit, adjust the color temperature if need be, set the DRX to 1.0 and use the resulting RSX (which REDAlert generates automatically alongside each R3D) in REDrushes for your transcode.

OH. And prepare to exercise patience. REDrushes is not fast. Even on a beefy 8-processor Mac Pro, it can still take all night, or even a whole weekend, to batch-process a lot of R3Ds.

Re: Transcoding red files
July 02, 2009 08:16PM
Jeff Harrell Wrote:
> R3D files are 12-bit linear with raw
> sensor data, while ProRes is 10-bit linear YUV.

I don't disagree with the advice here - RedRushes is probably the best way to make some 720p editing clips.

But, just as an FYI, codecs themselves don't dictate the linearity or otherwise of the data stored in them. A codec, generally speaking, can have linear, log or gamma encoded data in it.

R3D files "represent" or store 12 bit linear light raw sensor data - that's true enough. But you can't say ProRes is linear.

And as an FYI on the FYI, using the word "linear" is fraught with danger as it has been so misused to mean a perceptually linear encoding like video gamma, which is obviously a curve rather than a straight line. That's why when I talk about linear, I get extra specific and say linear light, and never refer to "linear" or worst of all "lin" because who really knows what anyone means by them? I don't, and it's confusing.

And BTW - YUV should really be Y'CbCr, but that's an awful mouthful...
Re: Transcoding red files
July 02, 2009 09:30PM
Fair enough, Graeme. I was oversimplifying, and you busted me for it. winking smiley

Re: Transcoding red files
July 03, 2009 11:33AM

"REDrushes is also where you make your debayer choice,"


"-1/4 debayer "

I have not worked with Red footage yet, so am confused by the term Debayer.

I don't mean to hijack the thread, but can someone give me a quick definition and explanation? Google wants to tell me about a brand name aspirin.
Re: Transcoding red files
July 03, 2009 12:18PM
On a Red camera, as with many digital cameras, the sensor pixels are arranged in a Bayer pattern. It goes G-X-G-X-G-X, where the "X" is red on the odd rows and blue on the even rows. Debayering is the process of interpolating the sensor data to get a full-color image. Most cameras do this internally; the Red does it on your computer, during processing.

Re: Transcoding red files
July 03, 2009 12:22PM
Thanks Jeff. I was pretty sure it had nothing to do with solving the headaches caused by new technology.

Re: Transcoding red files
July 05, 2009 04:23AM
And to add to that excellent answer:

Demosaicing (or debayering) is done in camera, but only for monitoring purposes, so you can see what you're shooting. Because we record the raw sensor data, compressed through REDCODE which keeps the data in it's raw Bayer pixel format, we get a few advantages, not least in file size, but flexibility in how to treat the data afterwards.

You can also extract movies without the demosaic, which is very fast, but not quite as high quality, but useful if you need a lower than full resolution fast.

Re: Transcoding red files
February 10, 2010 03:16PM
Hi, Jeff...

Great advice regarding "offline" editing workflow. But what about if it's for "online"?
Any suggestions on that?

Thank you!
Re: Transcoding red files
February 10, 2010 03:53PM
If you are editing RED footage online, you're dealing with the strength of the RAW workflow but you have to know what your full data path is to keep the flexibility that is a RED/RAW workflow.

If you are editing in FCP and colour correcting in FCS-Color, the Apple Whitepaper on RED workflow covers this well. If you just want to do a best-light conversion of the RED files for an HD finish and never go back to the RAW sources, you can convert the files in any number of Apps (I really like Colourfinder) and progress as usual. You are relying on that conversion though as our online so a full debayer is likely needed and that's not going to be fast if you don't have access to a RedRocket.

In all the RAW/RED workflow there is no one answer to how to offline/online. It's a very flexible data format and there are a myriad of ways to get it to the end product. You have to know what you need to end up with and what tools you have at your disposal.

Sleeplings, AWAKE!
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