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High Definition Video for Independent Filmmakers
A How To Guide for Digital Filmmakers
Welcome all! This is my blog to share my latest research,
thoughts, etc. on utilizing HD for independent filmmaking.

YES, I am available for consulting
Contact me at mike@hdforindies.com

All content copyright 2004-2007 Mike Curtis.

Monday, May 28, 2007

Final Cut Pro 6 ProRes Tidbit: 4:4:4 filtering or sampling? 


Doodling about making some test footage to take with me out of town, I'm getting ready to cook the DCI StEM footage down to ProRes.

Suddenly I notice an option on the export dialog in After Effects 7.0 - a checkbox for "Enable 4:4:4 chroma filtering" - now, is this a smoother cleaner way to get 4:2:2 results, or is this enabling 4:4:4 sampling? I notice it says filtering not sampling, so that gives me pause. Anybody got any more details on it than that?

I'm about to leave town, can't look into it now.

Wizdom of the Interweb Tubez, Inform Me!

-mike

Further note 1/2 hour later - you have to edit your After Effects setup text file (I've blogged on it in the past, don't recall off teh top of my head) to get ProRes to write out to ACTUALLY 10 bits - so that "Trillions" will be available instead of just "Millions" - my test files are going to be 8 bits worth of data, even if in a 10 bit codec. All part of the due dilligence thing, doncha know...

-mike

Tuesday night update - "Enable 4" does not appear in the FCP user manual, nor in the Compressor manual.

Consensus is that it is to help with chroma aliasing, so it truly is chroma FILTERING, not chroma SAMPLING. I emailed Adam Wilt on the issue and he sent me a test file to verify, I'll get to it when I can to have specifics.

I'm pretty much incommunicado this week, so if elsewhere on the web somebody has details, please email or add a Comment (link below) to fill me (and the rest of us) in.

-mike

Labels: , , ,

Posted by: Mike Curtis / 5/28/2007 08:35:00 PM
Comments:
According to DV-friendly Adam Wilt, Chroma Filtering appears to do some chroma voodoo for moving from a lower chroma sampling format (e.g.: 4:1:1) to a higher format codec (using 4:2:2 or 4:4:4 for example).

Check out his analysis in the aptly named "Steppy Edges" page of his site:

http://www.adamwilt.com/SteppyEdges.html
# posted by Blogger Bruce Findleton : Mon May 28, 09:04:00 PM CST
 
Standard ambiguous Applespeak for... yeah, some kind of chroma blur / low-pass filter to fix potential color aliasing / moire issues?

Bruce Allen
www.boacinema.com
# posted by Anonymous Bruce Allen : Mon May 28, 09:32:00 PM CST
 
We tried to test it last week (assuming it was to do subsampling down to 4:2:2) but it broke Shake 4.1 for us. [shrug]
# posted by Blogger stu willis : Tue May 29, 12:30:00 AM CST
 
If you concatenate 4:2:2 to 4:4:4 and back 4:2:2 filtering you will get chroma bleed if done over multiple generations. The CineForm codec has the same option when doing 4:2:2 compression from NLE and compositors that typically use 4:4:4:(4) pixels for processing. If you are doing multiple generations, you want to turn 4:2:2 to 4:4:4 filter off, or just use a 4:4:4 codec. :)

David Newman
CTO, CineForm
# posted by Blogger David : Tue May 29, 10:43:00 AM CST
 
Did any of you see this post over at http://www.studiodaily.com/blog/?p=97#respond Studio Daily. Looks like ProRes422 might not be as good as it is supposed to be. I do wonder if you don't need to change the setup file on AE CS3 to get 10 Bit out of ProRes422 though, and that might be why the 10 bit doesn't look any better than the 8 bit.M
# posted by Blogger Jonah Lee Walker : Tue May 29, 09:48:00 PM CST
 
Thanks for the link Jonah - I've been waiting for some ProRes tests. I don't know, but this one seems to speak more to color shifting than things like banding/artifacts/etc, not that it doesn't highlight a real problem. A close-up of the difference images might show other types of uglies on the edges. Then you could do a frame with a lot of motion...

As I've mentioned in other posts, we are about to go online with our 1080p24 project and I'm struggling to decide between Prores and Uncompressed. I need to upgrade to FCS2 and do some of our own tests, but that's time consuming. Hey - what are Mike's new interns up to these days?
# posted by Anonymous neil : Wed May 30, 07:23:00 AM CST
 
Gee, Neil, we all live to do your bidding!

;p

I've got them working on a project right now while I'm out of town.

-mike
# posted by Blogger Mike Curtis : Wed May 30, 07:32:00 AM CST
 
For anyone looking to modify the After Effects setup file, it is (on a Mac) located at /Library/Preferences/Adobe/After Effects/[version #]/Adobe After Effects [v#] Prefs

For me it was about line 1800 under
["QuickTime 64-bit Output Codecs"]
that I added
"apch" = "1"

apch refers to ProRes(HQ)

I successfully output images that look equivalent to my BlackMagic Uncompressed 10-bit out of After Effects. However, I notice that the ProRes images display a little brighter in QuickTime Player than do the BlackMagic images.

I presume it's a gamma issue that I do not yet understand.

Hope that helps anyone who like me was scouring the internet to figure out how to output to 10-bit color.
# posted by Blogger Eric : Wed Jun 27, 10:14:00 AM CST
 
i tried changing my prefs to add 10 bit access in AE, but i still only get 8bit in the output window.

running 8.0.1

is it still the same code as above?

"apch" = "1"
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# posted by Blogger freefun0616 : Mon Sep 14, 04:05:00 AM CST
 
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