As a follow up on the gamma shift subject, here is another writing:
How to fix an exported QuickTime video file that has the wrong color space tag.
There is an application written by Alex Mogurenko, called AMDCDX. It’s available for Windows, MacOS and Centos.
Download here:
https://mogurenko.com/2021/01/29/amcdx- ... er-v0-6-7/This application allows you to change the tag of a QuickTime video file so it can be interpreted correctly by the player.
It has other advanced editing purposes than changing metadata. However, I have only used it to edit Quicktime video: Color Primaries, Transfer Function, and Matrix Coefficients tag.
In the link below Alex is providing a list of color space Primaries, Transfer Function and Color Matrix.
http://mogurenko.com/2020/09/11/amcdx-v ... f_transferThe application has a Frame, Metadata, and File to File editor. Currently, it supports metadata editing for MOV. MFX, ProRes and MP4. Recently support for HDR metadata has been added.
If you are only interested in changing the color space video tag, use the Metadata editor tab >Color(colr/nclc< to change the Primaries, Transfer Function and Color Matrix.
To do this, please, follow these steps.
1- Download the application, AMCDX
2- Lunch AMCDX
3 - From the three tabs Menu (upper right corner) please select Metadata Editor
4 - Select, Open file
5 - From the dialog box, navigate and select the video file to be tagged
6 - Once loaded from Color(colr/nclc, select Remove NCLC
7 - Enter the corresponding Color Primaries, Transfer Function, and Matrix Coefficients in each contextual submenu tab.
8 - For Rec.709 equivalent to DaVinci Resolve: Rec.709-A, (1-1-1) select, ITU-R BT. R 709 in the three tabs. Then, select, Apply at the bottom right corner of the application.
You are done!
Please see screenshots attached here.
After this, I compare side by side the image and the new tag in QuickTime Player.
The new video file looks identical to Resolve Viewer, if you have followed the steps described in the previous response I did on this thread.
Note 1: I always make a copy of the original before I process to do this operation.
Note 2: Please notice that the application is not actually changing your grade within the video file. It’s changing the metadata for the file to be interpreted correctly outside the color grading studio.
In other words, it’s like this: my name is Willian Aleman. Most of my friends call me Willy. I’m still the same person who responses to his nickname too. Well, it’s something like that.
The full range versus legal range is another story.
You can avoid going into all this by using DaVinci Resolve with the right color management for the delivery color space with the right tag, as described in the previous email I wrote on this thread.
Hope this helps.
Thanks at lot to Alex Morurenko for developing AMCDX, and for his kind and prompt responses to my questions at his blog. Additional thanks to Dan Swierenga at The Post Process for his excellent writing describing the gamma shift and how to fix it using the right metadata tag.