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  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

Blocky Blacks on DnxHD output

S

scotty

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Has anyone else had a problem with very blocky / posterised blacks on DnxHD QTs? Having offlined now trying to render footage for online on Symphony Nitris. QTs however have these very blocky / posterised blacks when viewed in QT player and once imported to Avid.

Working on a 1080 25p project, generating 185X QTs from 2:1 4k footage, same problem is evident whether using Redcine / Red Alert / Monkey Extract.
Have just upgraded to Red Alert 3.60 and have the latest Avid codecs.

Looks like the files aren't really 10 bit. A colleague suggested that Avid QTs are only 8 bit even when selecting the 10 bit option?

TIFFs look fine in QT player and import into Avid Symphony Nitris fine as 185X, but would rather use QTs if possible.

regards

Brian
 
Select 185x as source when importing the QT's. If it does not say "fast import" then it is not 10bit. There has been a thread here with this issue when created from REDCINE. I have no issues when creating DNxHD 10 bit from REDrushes.

Michael
 
Michael

Thanks for the reply. Yes files do fast import when 185x is selected so the Symphony thinks they are 10 bit.

I thought I'd post an image to show the problem better.
Here's a section of the shot I noticed the problem on.

shot.jpg


If I export a TIFF and increase the gamma to make the blacks much more visible I get this :

tif.jpg


If I export a DnxHD 185X QT and increase the gamma by an identical amount I get this :

DnxHD.jpg


These stills are representative of the effect I see whether viewing the file in QT on the Mac Pro, or once imported to Symphony Nitris.

What's really interesting is that if I use the eyedropper in Photoshop on the TIFF file I get (in the black sleeve area) figures like 16/17/17, 18/18/19 etc. but on the DnxHD QT I get figures like 16/16/16 or 17/17/17, i.e. there is never any difference between the colour channels.

Does the DnxHD codec reduce saturation near black?

Any other ideas what's going on?

regards

Brian
 
Using a 23.976 R3D file out of REDCINE into DNxHD, I cannot get a "Fast Import" at all. Perhaps 1080p/25 is different. QuickTime Info shows it as a DNxHD file, but the Media Composer does not see it as a 10 bit file and 175x (23.976fps). Interestingly enough none of the resolutions settings will do a fast import. The same R3D file via REDrushes as 175x import with the "Fast Import" words in the import window after clicking OK.

I will try a 1080p/25 file to see if there is a difference in getting the "Fast Import" words to display during the import.

Michael
 
The issue is that the wrong ID is being applied to the QT wrapped DNxHD file - all files are labelled at 1080o/50 regardless of what they truly are. We are working with Assimilate to resolve this problem.

Michael
 
Michael

Thanks for this. Any workround at the moment e.g. modify QTs with something like Apple's Dumpster?

regards

Brian
 
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